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Polylactic acid (PLA) is currently the largest volume of production and application of synthetic biodegradable polymer via bio-derived materials. However, the relaxation characteristics and very low crystallization rate determined by the hand- structure of PLA chains result in low heat-resistance temperature and troublesome demold behavior for fast extrusion and/ or injection molding process. It is well known, by introducing of nucleating agent and crystal growing accelerator, the crystallization properties of PLA materials can be improved efficiently. In the paper, the isothermal crystallization behaviors of PLA, which include the rate and temperature of crystallization, crystallinity, crystals morphologies, were systemically shown. Meanwhile, a serious of regulation strategies of isothermal crystallization kinetics of PLA materials, such as adding of biodegradable polymers, different dimension of fillers, various chain-reconstruct for PLA, processing flow fields and post-treatment, were comprehensively summarized. Additionally, the regularity strategies and next study points for PLA isothermal crystallization behavior were also presented. [ABSTRACT FROM AUTHOR]

The work is devoted to the determination of technologically appropriate conditions for preparation of chemically pure salts of sodium and potassium orthophosphates based on solutions formed after the purification of orthophosphate acid from impurities of toxic elements by the method of complete ammonization with parallel co-precipitation with dicalcium phosphate. Based on the calculated solubility polytherms of mixtures of orthophosphates and chlorides of sodium, potassium, and ammonium at temperatures of 0–1000 Ñ, the conditions of their selective crystallization were determined. The results of calculations are compared with experimental data on crystallization of salts under laboratory conditions. The phase compositions of the sediments were confirmed by the XRD method. It was shown that the following chemically pure salts can be prepared from solutions of mixtures of orthophosphates and ammonium chlorides using the methods of isothermal-isohydric crystallization and conversion: Na2HPO4 (with a yield of up to 96%), NaH2PO4 (with a yield of up to 34%) and KH2PO4 (with a yield of up to 41%). The yield of crystalline KH2PO4 can be increased to 64% by converting NaH2PO4 with KCl. Measurements of the content of toxic compounds Cd(II), As(III), Cu(II), Pb(II) and fluorine in the synthesized salts showed that they were at levels lower than the current requirements for maximum permissible concentrations, therefore the synthesized salts can be used as food additives. [ABSTRACT FROM AUTHOR]

Polybutylene-1 (PB-1) consisting of form II and I in different ratio was achieved by solvent vapor annealing pure form II polybutylene-1 for different time. X-ray diffractometer was used to observe the phase transition of the residue form II at room temperature after solvent vapor annealing. The results show that the phase transition speed is faster than that of the natural phase transition and changed from fast to slow. By FTIR, the volatilization process of n-hexane in PB-1 was observed. After PB-1 sample was treated with solvent vapor annealing for several minutes, n-hexane in PB-1 was saturated. In the following phase transition at room temperature, the time required for n-hexane to volatilize from PB-1 is the same which demonstrates that it is independent of the time of solvent vapor annealing. This phenomenon indicates that residue n-hexane still promoted the phase transition of the residue form II at room temperature. With the volatilization of n-hexane, the promotion gradually decreased until it disappeared. Therefore, it is not necessary to treat Form II PB-1 sample in solvent vapor annealing until completely phase transition to Form I in actual application because more than 75% transition is enough and the residue solvent will also accelerate phase transition. [ABSTRACT FROM AUTHOR]

The precipitation and deposition of waxes in high waxy crude oil often result in the low throughput and clogging of pipeline. Adding polymers is a practical approach to solve these problems. In this study, poly(styrene-co-docosyl maleate) s (PSDMs) were synthesized by reversible addition-fragmentation chain transfer polymerization. The chemical structure and molecular weight of copolymers were characterized using Fourier infrared spectroscopy, 1H nuclear magnetic resonance spectroscopy, and gel permeation chromatography. The ratio of phenyl to aliphatic branches varies from 10:8 to 25:8. The crystallization and morphology of waxes in model oil were investigated by x-ray diffraction, differential scanning calorimetry, and polarized light microscopy. The cold flow behaviors of crude oil were evaluated by rheological methods. With the increase of the ratio of phenyl to aliphatic branches, the crystallinity, viscosity, and yield stress of crude oil first increase and then decrease. In the presence of PSDM-2, the crystallinity and enthalpy of phase transition (H) are reduced by 44.2% and 48.9%. Thus, the pour point, viscosity, and yield stress of crude oil are reduced by 6.0°C, 76.8% and 77.4%, respectively. Therefore, welldefined PSDMs are promising to be remarkable flow improvers for waxy crude oils. [ABSTRACT FROM AUTHOR]

The purpose of the work was to determine the optimal conditions for preparation of chemically pure salts of ammonium orthophosphates based on solutions formed after purification of extractable orthophosphoric acid from toxic impurities of d-metals, lead, arsenic and fluorine by their coprecipitation with calcium hydrogen phosphate. Based on the Sechenov’s modified formula, a method for calculating the solubility polytherms of orthophosphate salts in their mixtures with ammonium chloride was proposed. For its experimental confirmation, studies were conducted to determine the concentrations of saturated solutions of a number of orthophosphate salts in their mixtures with ammonium chloride at temperatures of 14, 40 and 800 C. The results of the calculations were well confirmed by experiments on selective crystallization. It was shown that the following chemically pure products can be obtained from solutions of mixtures of (NH4)2HPO4 and NH4Cl by the methods of isothermal-isohydric crystallization: (NH4)2HPO4 (with a yield of up to 79.5%) and NH4H2PO4 (with a yield of up to 52.4%). Measurements of the concentrations of Cd(II), As(III), Cu(II), Pb(II) and fluorine in the synthesized salts showed that they were at levels lower than the current requirements for maximum permissible concentrations. Therefore, these salts can be recommended for use as food additives. [ABSTRACT FROM AUTHOR]

The effect of melt processing temperature on the isothermal crystallization behavior of poly(3-hydroxybutyrate-co-4-hydroxybutyrate)[P(3HB-co-4HB)] is studied using differential scanning calorimetry and polarizing microscopy. P(3HB-co-4HB) undergoes thermal degradation above its melting temperature. The degree of degradation increases with increase in the 4HB content in copolymer. The formation of low molecular weight P(3HB-co-4HB) from thermal degradation reduces the crystallization temperature. Thus, the isothermal crystallization rate and crystallinity decrease at a processing of 190 ℃ compared with 180 ℃ where less thermal degradation occurs. This is more evident in the case of P(3HB-co-4HB) of high 4HB content. The P(3HB-co-4HB) crystals formed in the isothermal crystallization process have different perfectness in the 4HB rich phase and the 3HB rich phase depending on the melt processing temperature. This results in the appearance of two distinct melting peaks with different melting temperatures and melting enthalpies. Our results indicated that thermal history in the isothermal crystallization process will affect these crystals differently. [ABSTRACT FROM AUTHOR]

Mango (Mangifera indica L.) seeds is an interesting source of fat, rich in stearic (St) and oleic (O) acid with three major triacylglycerols (TAG): StOSt, StOO, and StLSt. The kernel fat content and quality depend however on the varieties and their origin. The objective of this study was to investigate the crystallization and polymorphic behavior of mango kernel fat extracted from three selected Ivorian varieties which differ in terms of TAG composition: Kent (KT), Djakoumankoun (DN) and Brooks (BR). The isothermal crystallization behavior was examined at 15 and 20°C by pulsed nuclear magnetic resonance, differential scanning calorimetry, x‐ray diffraction (XRD) and polarized light microscope. Under static conditions, DN crystallized faster, followed by BR, then KT. At 15°C, an unusual evolution was observed for both DN and BR, which can be explained by a melt‐mediated polymorphic transition from α into more stable forms. Using a differential scanning calorimetry (DSC) stop‐and‐return technique, different crystallization behaviors were also observed. Isothermal XRD experiments confirmed that the kinetics of the polymorphic transformation was different within the three samples, even if the three fats were β‐3L‐tending. At 15°C, KT transformed from liquid state to stable form without passing through α‐form, while DN and BR crystallized first into α‐from which transformed further to β′, then into stable β‐form. At 20°C, DN and BR crystallized directly from liquid to β′, which later transformed into β‐form while KT did not crystallize under the same conditions. The huge differences observed result from the differences in the TAG profiles, mainly in the StOO and StOSt content. [ABSTRACT FROM AUTHOR]

To study the effect of applied electric field on polymer crystallization, the crystallization of polyvinylidene fluoride (PVDF) was observed under modified polarized optical microscopy. The PVDF melts were crystallized based on programmed temperature, changes between two transparent conductive glass electrodes, on which a DC electric field was applied. The observations revealed that without the electric field, crystallizations below 160 °C resulted in only α-form crystals, while, at elevated temperatures, the formation of γ-form crystals also occurred. By applying the electric field at 1.7 kV/cm, γ-form crystals started emerging at the slightly lower temperature of 158 °C. Further examinations showed that both crystals, α-form and γ-form, grew at a greater rate with increasing field strength. A careful calculation of the Avrami parameters supported the data that the electric field enhanced the crystallization kinetics. Careful calculation based on the Laurientz–Hoffmann approach revealed that applying the electric field decreased the required energy for PVDF crystallization. The folding surface free energy of the PVDF crystallization, 1.76 × 10−2 Jm−2, was reduced to 1.57 × 10−2 Jm−2 and 1.43 × 10−2 Jm−2 after applying electric fields of 0.8 and 1.7 kVcm−1, respectively. We suggest that the electric field promoted the polymer chain alignment during the crystallization; as a result, it accelerated the polymer crystallization and lowered the energy requirement for crystallization. [ABSTRACT FROM AUTHOR]

Bio-based poly(butylene succinate-co-dodecylene succinate) (PBDSs) were successfully synthesized by adjusting the content of 1,12-dodecanediol (DD) using melt polycondensation method. The chemical structure, thermal behavior, crystallization properties, mechanical properties, and rheological properties were characterized. FTIR, 1 H NMR, and 13 C NMR showed the successful synthesis of polymers with the expected structure. The synthesized polymers have high number-average molecular weight (32500–64200 g/mol). The copolyesters were random copolymers. The relationship between melting temperatures and composition was basically V-shaped distribution, which is a typical characteristic of isodimorphism behavior. Thermogravimetric analysis (TGA) showed that the thermal stability of the synthesized copolyesters was good, with no significant weight loss until 320 °C. The synthesized polymers were all semi-crystalline polymers. When the amount of dodecylene succinate unit in the product is 80%, the copolyester has good mechanical properties (tensile strength: 34.5 MPa, elongation at break: 3489%) and processing properties, so it may be more suitable for making films. [ABSTRACT FROM AUTHOR]

Direct attainment of the crystal state corresponding to desired performances in processing can improve the productivity of semi‐crystalline polymer products. This work tried to propose the idea to approach the target by exploring the effects of nucleating agent content on non‐isothermal crystallization kinetics, isothermally crystallization morphologies and macroscopic properties of polypropylene (PP). The nucleating agent content varied from 0 to 0.5 phr, and all samples were prepared by melting blending at 180°C as the antioxidant and lubricant ensured fine stability and processing. The differential scanning calorimetry results and non‐isothermal crystallization kinetics indicated that introducing 0.3 phr nucleating agent advanced both initial crystallization and melting about 10°C and improved crystallization rate and crystallinity. Besides, 145°C was determined as an isothermal crystallization condition by setting temperature gradient, and the crystallization kinetics were described by a power‐law equation well. The average crystal size was refined to 40 μm uniformly and crystallization time was reduced to 1.5 min as loading 0.5 phr nucleating agent, contributing to the significant improvements in tensile and physical properties. Thus, adding such a short‐time heat insulation procedure into the non‐isothermal cooling stage during processing can obtain desired crystal state directly with loading adequate nucleating agent. [ABSTRACT FROM AUTHOR]

Copyright of Plastics Science & Technology / Suliao Ke-Ji is the property of Plastics Science & Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The properties, features of thermal behavior and crystallization of copolymers containing various types of valerate monomers were studied depending on the set and ratio of monomers. We synthesized and studied the properties of three-component copolymers containing unusual monomers 4-hydroxyvalerate (4HV) and 3-hydroxy-4-methylvalerate (3H4MV), in addition to the usual 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3HV) monomers. The results showed that P(3HB-co-3HV-co-4HV) and P(3HB-co-3HV-co-3H4MV) terpolymers tended to increase thermal stability, especially for methylated samples, including an increase in the gap between melting point (Tmelt) and thermal degradation temperature (Tdegr), an increase in the melting point and glass transition temperature, as well as a lower degree of crystallinity (40–46%) compared with P(3HB-co-3HV) (58–66%). The copolymer crystallization kinetics depended on the set and ratio of monomers. For terpolymers during exothermic crystallization, higher rates of spherulite formation (Gmax) were registered, reaching, depending on the ratio of monomers, 1.6–2.0 µm/min, which was several times higher than the Gmax index (0.52 µm/min) for the P(3HB-co-3HV) copolymer. The revealed differences in the thermal properties and crystallization kinetics of terpolymers indicate that they are promising polymers for processing into high quality products from melts. [ABSTRACT FROM AUTHOR]

The properties of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) P(3HB-co-3HHx) copolymers with different ratios of monomers synthesized by the wild-type strain Cupriavidus necator B-10646 on sugars, and an industrial sample from Kaneka synthesized by the recombinant strain C. necator NSDG-ΔfadB1 on soybean oil, were studied in a comparative aspect and in relation to poly(3-hydroxybutyrate) P(3HB). The copolymer samples, regardless of the synthesis conditions or the ratio of monomers, had reduced values of crystallinity degree (50–60%) and weight average molecular weight (415–520 kDa), and increased values of polydispersity (2.8–4.3) compared to P(3HB) (70–76%, 720 kDa, and 2.2). The industrial sample had differences in its thermal behavior, including a lower glass transition temperature (−2.4 °C), two peaks in its crystallization and melting regions, a lower melting point (Tmelt) (112/141 °C), and a more pronounced gap between Tmelt and the temperature of thermal degradation (Tdegr). The process, shape, and size of the spherulites formed during the isothermal crystallization of P(3HB) and P(3HB-co-3HHx) were generally similar, but differed in the maximum growth rate of the spherulites during exothermic crystallization, which was 3.5–3.7 μm/min for P(3HB), and 0.06–1.25 for the P(3HB-co-3HHx) samples. The results from studying the thermal properties and the crystallization mechanism of P(3HB-co-3HHx) copolymers are important for improving the technologies for processing polymer products from melts. [ABSTRACT FROM AUTHOR]

The isothermal crystallization behavior of crystalline and amorphous poly(3-hydroxybutyrate-co-4-hydroxybutyrate)[P(3HB-co-4HB)] mixtures are investigated on a differential scanning calorimeter and a polarizing microscope. The crystallization rate of the crystalline P(3HB-co-4HB) is decreased with increase in the amorphous P(3HB-co-4HB) in the mixture and the relative crystallinity also decreases. As with P(3HB-co-4HB), the optimum crystallization of the mixtures also occurs around 60 °C and results in maximum relative crystallinity. At 80 °C, larger spherulites are formed slowly as the number of nuclei formed are smaller compared to the crystallization at 40 °C or 60 °C and the relative crystallinity is similar irrespective of the 4HB content of the copolymer and the composition of the mixture. When the crystallization behavior of P(3HB-co-4HB) copolymer and mixtures of similar 4HB content are compared the mixture exhibits a similar relative crystallinity with P(3HB-co-4HB) copolymer but the crystallization rate is significantly lower. [ABSTRACT FROM AUTHOR]

Analysis of the isothermal crystallization kinetics of polyethylene terephthalate (PET) and reorganized PET was carried out using differential scanning calorimetry (DSC). Reorganization of PET process results in material with widely different organizations, structures, and morphologies of their polymer chains and different material properties. In thermal study of PET and RPET, the Avrami equation explained the primary stage of the isothermal crystallization of both PET and RPET. In the crystallization process of PET and RPET, the secondary crystallization occurred simultaneously with the primary crystallization and the two processes obeyed different Avrami time dependences. Lauritzen–Hoffman's (L-H) secondary nucleation theory and the Lauritzen Z-test explained the microscopic description of the crystallization kinetics. The L-H analysis revealed that both PET and RPET crystallization followed regime I to II transitions at temperatures between 194 and 240 ° C. The folding surface free energies of RPET, determined from the Lauritzen–Hoffman equation, were σ e = 61.2 erg/cm2 and 64.9 erg/cm2; and the works of chain folding were q = 7.38 Kcal/mol and 7.83 Kcal/mol, for regime I and regime II, respectively, whereas for PET they were σ e = 50.2 erg/cm2 and 70.4 erg/cm2; and the works of chain folding were q = 6.06 Kcal/mol and 8.49 Kcal/mol, for regime I and regime II, respectively. Polarized optical microscopy observations showed that different morphologies were developed in RPET than PET when crystallized from the melt. The mechanical properties and morphology of PET and RPET were studied using a universal tensile machine and atomic force microscopy, respectively. The morphological study, the mechanical properties and the thermal behavior of RPET confirmed that the RPET had an enhanced crystallization rate and mechanical parameters. [ABSTRACT FROM AUTHOR]

The raw material of polylactide (PLA) is lactic acid obtained by biological fermentation. PLA is the most promising degradable polymer to replace traditional plastics to address the pollution problems caused by their non-degradability. However, the application of PLA is hindered by its low softening temperature, easy hydrolysis, and poor toughness. Herein, the ternary composites with PLLA, PDLA and Poly (butylene adipate- co -terephthalate) (PBAT) were prepared by melt blending to balance its thermal stability, hydrolysis, and toughness. The effects of PBAT content (3 %, 6 %, 9 % and 12 %) and isothermal crystallization temperature on composite properties were fully investigated. The results show that the composite of stereo-complexed PLA (sc-PLA) with 6 % PBAT crystallized at 110 °C exhibits good comprehensive properties. Its vicat softening temperature (VST), mass loss rate under alkaline (pH = 12) and breaking elongation are 166 °C, 21.6 % and 4.40 %, respectively. Compared with the pure PLLA sample crystallized at same condition, the VST, mass loss rate and breaking elongation are 159 °C, 24.7 % and 3.76 % respectively, which increased by nearly 5 %, 13 % and 20 %. This indicates that this strategy is feasible to balance the heat resistance, hydrolysis resistance and toughness of PLA, while it sacrifices the tensile strength a little. This work provides a new way to modify and improve the PLA properties. Nonetheless, it is also necessary to coordinate the compatibility of PLA and PBAT. [ABSTRACT FROM AUTHOR]

Crystallization of polyamide 12 (PA12) is an essential process requiring thorough investigation for evaluating the mechanical properties after the polymer parts are manufactured. The change in crystallization temperature results in different crystallization behaviors for PA12. Hence, the crystal morphology of PA12 achieved provides important information about crystallization behavior, especially for those produced through additive manufacturing due to its heterogenous cooling rate in a single print bed. Considering the need of investigating PA12 crystallization using phase‐field modeling, this paper aims to simulate the spherulite morphology of PA12 undergoing isothermal crystallization. This model is compared with the spherulite morphologies obtained from the optical microscopy test. The model shows that PA12 spherulites have thicker dendrites when the isothermal temperature is higher. The present phase‐field model can determine the spherulite morphologies of bulk printed PA12 based on the crystallization condition and be used to evaluate the properties of the printed part. [ABSTRACT FROM AUTHOR]

Objects. Due to the polymer waste accumulation, the search for new directions for their utilization is urgent. Chemical recycling methods are of considerable interest, which allow one to obtain the original monomers or change the compositions of the copolymers. From the point of view of building a circular economy, a promising material is polyethylene terephthalate (PET), on the basis of which amorphous copolyesters can be obtained. The study aimed to analyze the simultaneous glycolysis and interchain exchange reactions of PET in the presence of the oligoethylene phthalate modifier with hydroxyl end groups and the study of isothermal crystallization of poly(ethylene phthalate-co-terephthalates) with different phthalate contents obtained in this way.Methods. Oligoethylene phthalate is synthesized by polycondensation. Poly(ethylene phthalateco-terephthalates) were obtained by the interaction of post-consumer PET with oligoethylene phthalate. The composition of the oligomer and copolymers was confirmed using Fourier-transform infrared spectroscopy, thermal characteristics and crystallization half-times were determined by differential scanning calorimetry.Results. In this work, the use of the post-consumer PET chemical recycling process, aimed at obtaining copolyesters under the influence of small modifier amounts was proposed. The process consisted in carrying out the combined interchain exchange and degradation with a complex oligoester different from PET. Poly(ethylene phthalate-co-terephthalate) copolymers were obtained via reaction of post-consumer poly(ethylene terephthalate) flakes and synthesized oligoethylene phthalate resin in the melt phase in the absence of catalyst. The effect of phthalate concentration in polymer on the isothermal crystallization of phthalate substituted poly(ethylene terephthalate) was estimated.Conclusions. The hypothesis about the possibility of using an oligoester modifier to obtain the PET-based copolymer at the high rate and without reducing the molecular weight to values characteristic of a monomer or oligomer has been confirmed. The process can be used to obtain random copolyesters based on post-consumer PET. The phthalate unit concentration increase is followed by decrease in the glass transition temperature, temperature and heat of fusion, and increase in crystallization half-times. Phthalate has a better ability to retard PET crystallization than 2-methyl-1,3-propanediol or furandicarboxylic acid, but is inferior to some of the other modifiers known.

The results of studying the structural features of nanocomposites by electron microscopy, X-ray diffraction analysis, derivatography and stepwise dilatometry are presented. The kinetic regularities of crystallization of nanocomposites based on Exxelor PE 1040-modified high density polyethylene HDPE* and carbon black (CB) are considered by the method of stepwise dilatometry: the dependence of specific volume on temperature. Dilatometric studies were carried out in the temperature range of 20–210 °C. The concentration of nanoparticles was varied within 1.0, 3.0, 5.0, 10, and 20 wt%. In the process of studying the temperature dependence of the specific volume of nanocomposites, it was found that a first-order phase transition occurs for HDPE* samples with 1.0–10 wt% CB content at 119 °C, and for a sample with 20 wt% CB at 115 °C. The study of the process kinetics of nanocomposites isothermal crystallization showed that, for nanocomposites with 1.0–10 wt% CB content, the mechanism of the process is characterized by the formation of a three-dimensional spherulite structure with continuously formed homogeneous and heterogeneous nucleation centers. A substantiated theoretical analysis and interpretation of the discovered regularities of the crystallization process and the growth mechanism of crystalline formations is given. Derivatographic studies of nanocomposites were carried out, according to which the features of changes in the thermal-physical properties of nanocomposites depending on the content of carbon black were established. The results of X-ray diffraction analysis of nanocomposites with 20 wt% carbon black content are presented, according to which there is a slight decrease in their degree of crystallinity.

Copyright of China Plastics / Zhongguo Suliao is the property of Journal Office of CHINA PLASTICS and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The properties, features of thermal behavior and crystallization of copolymers containing various types of valerate monomers were studied depending on the set and ratio of monomers. We synthesized and studied the properties of three-component copolymers containing unusual monomers 4-hydroxyvalerate (4HV) and 3-hydroxy-4-methylvalerate (3H4MV), in addition to the usual 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3HV) monomers. The results showed that P(3HB-co-3HV-co-4HV) and P(3HB-co-3HV-co-3H4MV) terpolymers tended to increase thermal stability, especially for methylated samples, including an increase in the gap between melting point (Tmelt) and thermal degradation temperature (Tdegr), an increase in the melting point and glass transition temperature, as well as a lower degree of crystallinity (40–46%) compared with P(3HB-co-3HV) (58–66%). The copolymer crystallization kinetics depended on the set and ratio of monomers. For terpolymers during exothermic crystallization, higher rates of spherulite formation (Gmax) were registered, reaching, depending on the ratio of monomers, 1.6–2.0 µm/min, which was several times higher than the Gmax index (0.52 µm/min) for the P(3HB-co-3HV) copolymer. The revealed differences in the thermal properties and crystallization kinetics of terpolymers indicate that they are promising polymers for processing into high quality products from melts.

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of China Synthetic Fiber Industry is the property of Sinopec Baling Petrochemical Company and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Laser sintering of polymers (LS) is one of the most promising additive manufacturing technologies as it allows for the fabrication of complexly structured parts with high mechanical properties without requiring additional supporting structures. Semi-crystalline thermoplastics, which are preferably used in LS, need to be processed within a certain surface temperature range enabling the simultaneous presence of the material in both, the molten and solid state. In accordance with the most common processing models, these high temperatures are held throughout the entire building phase. In the state of the art, this leads to high cooling times and delayed component availability.In this paper, process-adapted methods, in-situ experiments and numerical simulations were carried out in order to prove that this drawback can be overcome by material-adapted processing strategies based on a deepened model understanding. These strategies base on the fact, that the crystallization and solidification of polyamide 12 is initiated a few layers below the powder bed surface at high temperature and quasi-isothermic processing conditions. Therefore, isothermal crystallization and consolidation behaviour is analyzed by process-adapted material characterization. The influence of temperature fields during laser processing was analyzed in dependence of part cross-section, layer number and fabrication parameters and correlated to the resulting part properties. Furthermore, the possibility to homogenize the parts thermal history by controlling the part cooling is highlighted by a simulational approach. The authors show that the material-dependent solidification behavior must be taken into account as a function of the geometry- and layer-dependent temperature fields and demonstrate a major influence on the material and component properties. From these findings, new processing strategies for the laser exposure process as well as for the temperature control of the build chamber in z-direction arise, which allow for the acceleration of the LS process and earlier availability of components with more uniform part properties.

Abstract Cocoa butter is one of the most important ingredients in chocolate production as it is responsible for important characteristics of chocolates such as hardness, snap, mold shrinkage, fat bloom stability and melting. It appears that factors such as the geographic area and climate where cocoa is grown directly affect the chemical composition of cocoa butter, so fruits grown in Africa and Asia have greater thermal stability. In this sense, two samples of cocoa butter, a Brazilian one from the south of Bahia and a commercial one (consisting of a mixture of butters from different origins) were studied and compared. The results obtained in this study showed that Brazilian cocoa butter had a higher content of Saturated Fatty Acids (SFA) and a higher content of unsaturated triacylglycerols compared to commercial butter. It also showed a faster polymorphic transition and a higher maximum solids content compared to commercial cocoa butter, indicated by isothermal crystallization analysis. Based on the analyzes carried out, it was found that this cocoa butter studied, from the Forasteiro amelonado species and coming from several farms in the south of Bahia, presented greater thermal stability in relation to commercial cocoa butter, i.e., different from that presented in other studies in the literature.

The crystallization kinetics of semicrystalline polymers is often studied with isothermal experiments and analyzed by fitting the data with analytical expressions of the Avrami and Lauritzen and Hoffman (LH) theories. To correctly carry out the analysis, precautions in both experiments and data fitting should be taken. Here, we systematically discussed the factors that influence the validity of the crystallization kinetics study. The basic concepts and fundamentals of the Avrami and LH theories were introduced at first. Then, experimental protocols were discussed in detail. To clarify the impact of various experimental parameters, selected common polymers, i.e., polypropylene and polylactide, were studied using various experimental techniques (i.e., differential scanning calorimetry and polarized light optical microscopy). Common mistakes were simulated under conditions when non-ideal experimental parameters were applied. Furthermore, from a practical point of view, we show how to fit the experimental data to the Avrami and the LH theories, using an Origin® App developed by us. [ABSTRACT FROM AUTHOR]

The effect of addition of a chain extender (ADR) creating branches on nylon 6 (PA6) by reactive extrusion on the isothermal crystallization behavior is studied. The effect of addition of small amounts of polyketone (PK) capable of forming strong hydrogen bonds with PA6 chains as an additive in reactive extrusion on the isothermal crystallization behavior is also studied. Addition of chain extender to PA6 results in a decrease in the degree of crystallization and the crystallization rate due to the formation of branches, and the increase in the chain extender content or reaction temperature speeds up the reaction forming branches to result in a greater decrease in the degree of crystallization and the crystallization rate. Addition of PK to PA6 results in a decrease in the degree of crystallization and the crystallization rate, and the degree of decrease is dependent on the amount of added PK. Addition of PK along with the chain extender results in a greater decrease in the degree of crystallization and the crystallization rate due to the additional formation of hydrogen bonds between branched PA6 and PK chains. [ABSTRACT FROM AUTHOR]

Copyright of China Synthetic Fiber Industry is the property of Sinopec Baling Petrochemical Company and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Heat resistance poly(lactic acid) PLA/ethylene butyl methacrylate glycidyl methacrylate terpolymer (GEBMA)/talc composites were fabricated by melt mixing. Talc is a high aspect ratio filler that has the potential to substantially enhance the heat resistance of crystalline polymer composites. The heat resistance of PLA/GEBMA/talc composite was remarkably enhanced by incorporating a small amount of talc. GEBMA has been introduced as a compatibilizer to improve the interphase balance between the constituent PLA matrix and talc. GEBMA coated on the surface of talc and lead to closely contact with PLA during the melting process. Well-dispersed talc composites were obtained, as observed by scanning electron microscopy. The polarized optical microscopy and thermal analysis results showed that the talc acted as a heterogeneous nucleating agent promoted the crystallization of the PLA (increased the crystallization rate and reduce the crystal size). However, the high content talc affects the mechanical properties of the composites, the tensile strength and impact strength decreased. Besides, the weakened chemical reaction was found between PLA and GEBMA during melt blending. Therefore, the PLA/GEBMA/talc composites have good heat resistance properties. [ABSTRACT FROM AUTHOR]

The concept of shape memory hybrids (SMHs) has been proposed in recent years as a new kind of shape memory materials. By carefully selecting the actual composition of SMHs, some special features could be realized to meet the requirements of particular engineering applications. However, in terms of simulation, conventional constitutive models for shape memory polymers (SMPs) struggle to precisely characterize certain unique properties of these SMHs. In this study, a constitutive model integrating both rheology and phase transition conceptions is proposed to simulate the mechanical behaviors including shape memory effect of dual-component SMHs. The specific yielding phenomenon at room temperature of SMHs, induced by debonding between two components, is explained by incorporating particle-damage theory. Compared with the experimental and simulated results from a kind of SMH which can be programmed isothermally, it is indicated that the proposed constitutive model effectively captures the mechanical characteristics as well as the shape memory behaviors and the phenomenon of particle debonding damage of these SMHs. Furthermore, the influences of different parameters, such as component proportion, temperature, and isothermal shape fixing time, on these SMHs are discussed as well. This versatile model offers valuable insights for the development of constitutive models in this field as it is not limited to this case only, but could also be promoted to various different kinds of dual-component SMH systems. • A universal thermomechanical constitutive model for two-component shape memory hybrids (SMHs) is proposed. • Thermomechanical responses including shape memory behaviors of SMHs can be accurately simulated utilizing this model. • Unique properties of a reported SMHs, such as isothermal programming and yielding, are accurately replicated by this model. • Influences of component proportion, temperature, and programming time, on SMHs' mechanical properties are discussed. [ABSTRACT FROM AUTHOR]

• Milkfat (MF) crystallization varies with palmitic acid (PA) content. • Cooling induces 1 or 2-step crystallization mechanisms in melted blends. • Low PA concentration maintains MF crystal nanostructure (β' form). • At 10%, PA initiates crystallization, guiding α and β form. We performed a nanoscale study based on X-ray scattering to understand the impact of a promotor of crystallization, palmitic acid (PA), at high concentration, on the networks of triacylglycerols (TAGs) in anhydrous milk fat (AMF). Melted blends containing 10 wt% PA were quenched at 25 °C. X-ray scattering data were compared with those obtained for pure AMF, pure PA, and AMF containing 1 wt% PA. While PA at low concentration did not modify the nanostructure of TAG crystals (direct crystallization in the β'-2L form), a high concentration of this promotor favored the formation of polymorphic forms suggesting that PA first crystallizes and then directs crystallization of AMF TAGs towards α and β forms. [ABSTRACT FROM AUTHOR]

Clarifying the relationship between crystal evolution and the physical foaming behavior of high-hardness thermoplastic polyurethane (HD-TPU) is essential for preparing HD-TPU foams with controllable cellular morphology. In this study, two thermal treatment methods, isothermal annealing and isothermal crystallization, were utilized to control the crystal structure of HD-TPU. The effect of crystals on the physical foaming behavior of HD-TPU foams was examined. The annealing process produced mainly lamellae and Form Ⅰ structure, while isothermal crystallization primarily led to Form Ⅱ spherulites. Foams based on original and pre-treated HD-TPU were prepared by pressure quench foaming. The evolution of foam density and cell morphology was discussed. At low foaming temperatures, crystals induced the heterogeneous nucleation. Realizing a uniform cell structure at high foaming temperatures could be challenging when the spherulite size was large. When the size of the spherulite was small but loosely distributed, larger cells with thinner cell walls could be obtained. However, if the spherulite distribution was dense, the spherulites hindered cell growth, resulting in unevenly distributed and deformed cells. [Display omitted] • HD-TPU samples with crystal structures from lamellae, to Form Ⅰ paracrystals and Form Ⅱ spherulites were generated. • HD-TPU foams with densities of about 0.45–1.1 g/cm3 were fabricated using CO 2 as a foaming agent. • HD-TPU samples with nanoscale crystals developed by the annealing process acted as heterogeneous nucleating sites to enhance the cell nucleation. • Form II spherulites in HD-TPU could be induced by the melt-crystallization process; large spherulites hindered the cell growth. [ABSTRACT FROM AUTHOR]

Raman imaging in the low- and high-frequency regions accomplished visualization the intermolecular interaction and crystallization of polymer blend. [Display omitted] • Low-frequency Raman observed the intermolecular interactions during the phase separation and crystallization of PHB/PLLA. • The changes in the intermolecular interaction of PHB/PLLA were visualized by Raman imaging using the hydrogen bonding of PHB. • The low-frequency Raman spectra show high sensitivity in detection at the start of phase separation and crystallization. The visualization of the variation of the inter/intra molecular interaction (C = O⋯CH 3) between poly[(R)-3-hydroxybutyrate] (PHB) and poly-L-lactic acid (PLLA) in the PHB/PLLA miscible blend during phase separation and crystallization process was successfully investigated using Raman imaging. Images of the blend were developed using high- and low-frequency Raman spectra acquired during the isothermal crystallization of the blend, and both of them were compared. The low-frequency region allowed to observe the changes in the hydrogen bonds between the molecular chains in the blend during phase separation and crystallization via a band at 75 cm−1 derived from PHB. The imaging results obtained using the band at 75 cm−1 due to hydrogen bonding (C = O⋯CH 3) between molecular chains were in good agreement with the results obtained using the C = O stretching band at 1720 cm−1. Herein, we demonstrated that the low-frequency region of the Raman spectrum is more sensitive to detecting the start of the phase separation and crystallization of PHB than the corresponding high-frequency region. [ABSTRACT FROM AUTHOR]

The structural, thermal, and mechanical properties of unreinforced and reinforced polylactic acid (PLA) were investigated. The PLA was a biopolymer that was reinforced with four fillers (i.e., graphene oxide (GO) and silver (Ag); vermiculite (VMT) and silver (Ag); and two organically modified vermiculites). The processing technique for the production of the composite materials were carefully planned. The PLA nanocomposites were investigated by examining their morphological aspects, changes in PLA phases and transitions and, most importantly, the effect on certain final properties. X-ray diffraction and differential scanning calorimetry (DSC) analysis indicated that the sample was completely amorphous. Thermogravimetric analysis (TGA) results indicated that the presence of reinforcing particles in the PLA matrix did not affect the thermal degradation of these composites. Furthermore, the local mechanical properties were investigated using the microindentation method to evaluate the effect of different nanofillers. Scanning electron microscopy (SEM) and a VHX-500 optical digital microscope (Keyence International, Mechelen, Belgium) were also used to examine the surface morphology of the PLA polymer composites. These results can help to select suitable fillers to enhance the PLA performance of biopolymers. [ABSTRACT FROM AUTHOR]

The influence of organic additives on crystallization of polyolefins has not been paid enough attention due to the low dosage, but it may have a significant impact on the properties of polyolefins. In the paper, the organic amphiphilic molecules were introduced into high-density polyethylene (HDPE) through melt blending, and compared with neat HDPE. It is mainly discussed for the following aspects including analysis of crystal structure and morphology using wide-angle X-ray diffraction (WAXD) and polarized optical microscopy (POM), respectively; analysis of crystallinity, crystal rate, crystal growth and crystallization enthalpy, using the differential scanning calorimetry (DSC). The research indicates that the organic amphiphilic molecules may act as an internal lubricant. On the one hand, HDPE molecular chains are easy to fall off from crystal lattices, resulting in lagging crystallization peak, simultaneously reducing the interaction between HDPE molecules should induce the lower activation energy (ΔEm) to increase the crystallinity of HDPE. On the other hand, the amphiphilic molecules should be exclude from HDPE crystal to the amorphous area due to poor compatibility; thus, the HDPE/amphiphilic molecules blends, similar to neat HDPE, conduct homogeneous nucleation, and the growth of monocrystal performs the tendency of the zero-dimension to the two-dimension with increase in temperature of isothermal crystallization and decreasing cooling rate of non-isothermal crystallization. It is hoped that through these studies, people will pay more attention to the impact of organic additives on the performance of HDPE. [ABSTRACT FROM AUTHOR]

The solid–liquid (S–L) phase separation occurs in the polyethylene (PE)/liquid paraffin (LP) blend, which exhibits different characteristics for the molecular weight of PE. Herein, we have studied the S–L phase separation process of PE-500 (molecular weight of 5,000,000)/PE-60 (molecular weight of 600,000)/LP melts by the hot-stage-optical device. It is found that the clarification temperature and cloud temperature of PE-500/PE-60/LP blend decreased with the addition of PE-60. The isothermal crystallization behavior of these ternary blends is explored further using differential scanning calorimetry (DSC). According to the analysis results of Avrami equation and Arrhenius equation, the exponent n increases from 1.23 to 2.42 at higher temperature, indicating that the melt with high PE-60 content have a growth pattern between two and three dimensions, which could lead to larger pore. The activation energy at high temperature increases from 738.568 to 1321.259 kJ / mol with enhancing PE-60 content, while the activation energy decreases from 209.689 to 36.608 kJ / mol at lower temperature. It demonstrates that PE-60 content is not conducive to nucleation at high temperatures, but in favor of growth at low temperature. We believe the pore structure of PE microporous membrane may be controlled by different ratios of PE-500/PE-60 and crystallization temperature. [ABSTRACT FROM AUTHOR]

Methods of NMR relaxation and differential scanning calorimetry (DSC) were used to study the crystallization of anhydrous milk fat (AMF) obtained from milk and subjected to ultrasonic (US) processing. Amongst the changes in the crystallization nature under the influence of ultrasound are the decrease in the crystallization temperature and the increase in the melting enthalpy of the anhydrous milk fat samples. The increase is ∼30% at 20 min of isothermal crystallization and is presumably explained by the additional formation of β'-form crystals from the melt. The parameters of the Avrami equation applied to the description of experimental data show an increase in the crystallization rate in samples with ultrasonic treatment and a change in the dimension of crystallization with a change in melting temperature.

Five coextruded and one blown polyethylene (PE)-based packaging films were analyzed with the aim to determine the number and thickness of the film layers and tensile mechanical properties and to prove composition declared by a producer. They were chosen the most effective methods such as Fourier-transform infrared spectroscopy (attenuated total reflectance and transmission modes), differential scanning calorimetry (DSC), thermogravimetry, wide-angle X-ray diffraction (XRD), and confocal laser scanning microscopy. The latter turned out to be very effective method to show the film layers on its fracture surfaces due to very good contrast and different fracture patterns of each layer. Two to five layers were detected in the films, whereas silicone surface layer with the thickness not higher than 1 µm was very nicely detected in two coextruded films. The type of PE (low density, linear low density and high density) was determined by DSC, whereas miscible types of PE were differentiated only after performance of stepwise isothermal crystallization. This was performed in case of four films at 124, 114, 104, and 94 °C with 30-min dwell at each temperature. Random copolymer of polypropylene was identified by DSC in two films. Infrared spectroscopy revealed polymers present in low content (ethylene–vinyl acetate and silicon) and, in addition, additives such as calcite, which was detected also by XRD. The major polymer components were proved in four films. Mechanical properties varied in machine and transverse direction in case of all films. The methods used are also recommended for quality control of coextruded films. [ABSTRACT FROM AUTHOR]

Nanocomposites of poly(ethylene glycol) (PEG) reinforced with graphene oxide (GO), prepared by drying their ultrasonically homogenized aqueous solution, were incorporated in poly(l-lactic acid) (PLLA) via melt extrusion. Raman spectroscopy revealed that the employed method increased GO's structural defects due to exfoliation and allowed PEG to penetrate its layers. Hydrogen bonding interactions were identified in the hybrids by Fourier transform infrared spectroscopy (FTIR), whereas differential scanning calorimetry (DSC) tests showed that GO promoted PEG's crystallization by increasing its crystallization temperature (Tc) and degree of crystallinity (Xc). The combination of nucleant and plasticizer in the hybrids increased PLLA's Tc and melting temperature and a new band, associated with crystalline domains, appeared in their FTIR spectra. The Avrami kinetic model was implemented on DSC data to understand the isothermal crystallization behavior of PEG/PLLA blend, as well as of the system GO/PEG/PLLA. It was highlighted that GO is an effective nucleating agent for plasticized PLLA since, under the examined conditions, it enhances its crystallization rate and transforms the disk-like to sphere-like crystal formation and the two-dimensional to three-dimensional crystal growth. Furthermore, GO increased the crystallization activation energy values of plasticized PLLA due to segment transportation obstruction and transformed the double-melting peak into single after isothermal crystallization. Thermogravimetric analysis showed that GO did not enhance the heat resistivity of plasticized PLLA. [ABSTRACT FROM AUTHOR]

The structural, thermal, and mechanical properties of unreinforced and reinforced polylactic acid (PLA) were investigated. The PLA was a biopolymer that was reinforced with four fillers (i.e., graphene oxide (GO) and silver (Ag); vermiculite (VMT) and silver (Ag); and two organically modified vermiculites). The processing technique for the production of the composite materials were carefully planned. The PLA nanocomposites were investigated by examining their morphological aspects, changes in PLA phases and transitions and, most importantly, the effect on certain final properties. X-ray diffraction and differential scanning calorimetry (DSC) analysis indicated that the sample was completely amorphous. Thermogravimetric analysis (TGA) results indicated that the presence of reinforcing particles in the PLA matrix did not affect the thermal degradation of these composites. Furthermore, the local mechanical properties were investigated using the microindentation method to evaluate the effect of different nanofillers. Scanning electron microscopy (SEM) and a VHX-500 optical digital microscope (Keyence International, Mechelen, Belgium) were also used to examine the surface morphology of the PLA polymer composites. These results can help to select suitable fillers to enhance the PLA performance of biopolymers.

Poly(ethylene terephthalate) (PET) materials with different molecular weights were isothermally crystallized from melt by systematically varying the temperature and duration of the treatment performed in the differential scanning calorimeter (DSC). Multiple endotherm peaks were observed on the subsequent heating thermograms that were separated from each other on the basis of their melting temperature versus crystallization temperature and melting temperature versus crystallinity function. By this new approach five sub-peak sets were identified and then comprehensively characterised. Wide-Angle X-Ray Diffraction (WAXD) analyses revealed that the identified sub-peak sets do not differ in crystalline forms. By analysing the crystallinity and the melting temperature of the sub-peak sets as a function of crystallization time, crystallization temperature and intrinsic viscosity, it was concluded that below the crystallization temperature of 460 K the sub-peak sets that were formed during primary or secondary crystallization transform partially or completely to a third sub-peak set during the heating run of the measurement, while above this temperature, the sub-peak set formed during primary crystallization gradually transforms to a more stable structure, with higher melting temperature. These formations and transformations are described with mathematically defined parameters as well. [ABSTRACT FROM AUTHOR]

In this work, a series of polypropylene/polyvinyl butyral (PP/PVB) blends were prepared by melt-blending process, at PVB loadings 3 wt%, 10 wt%, and 30 wt%. The effects of PVB on crystallization behavior of PP were investigated by differential scanning calorimetry (DSC), and polarized optical microscopy (POM). The isothermal crystallization kinetics were analyzed by Avrami equations. It was found that the addition of PVB strikingly reduced the overall crystallization rate of PP. The POM results further indicated that the crystallization rate of PP/PVB was significantly reduced by reducing the nucleation density of PP with the addition of PVB. The fractured surface morphology of PP/PVB blends was characterized by scanning electron microscopy (SEM), and the results showed that the PVB was uniformly dispersed in the PP matrix as small spherical particles, with a good dispersion and dimensional stability.

In this article, a facile and efficient isothermal crystallization induction method was proposed to fabricate microcellular poly(butylene succinate) (PBS) foams with supercritical CO2. The good regularity of PE chain segments and high reactive epoxy groups in ethylene‐glycidyl methacrylate copolymer (PE‐g‐GMA) serving as a chain extender were employed to improve the crystallization behaviors, viscoelasticity, and foaming behaviors of PBS through chain extension reaction. The effect of PE‐g‐GMA content on the thermal properties, rheological performances, and cellular morphology of various PBS samples was investigated systematically. When the PE‐g‐GMA content switched from 7.5 to 10 wt %, an interesting transition from fine cells to microcells was observed in PBS/PE‐g‐GMA foams. Microcellular PBS foam modified by 10 wt % PE‐g‐GMA was successfully prepared at the foaming temperature of 87 °C and the induction time of 7 min, in which its cell size and cell density could reach 6.63 ± 1.93 μm and 3.75 × 109 cells cm−3, respectively. The formation of abundant but tiny spherocrystals in chain extended PBS samples made a considerable contribution for preparing microcellular PBS foams. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48850. [ABSTRACT FROM AUTHOR]

Different compound nucleating agents consisting of a highly efficient novel α-nucleating agent N,N'-bis(benzoyl) sebacic acid dihydrazide and three typical β-nucleating agents N,N-dicyclohexylterephthalamide, rare earth compound (WBG-II) and calcium pimelate were incorporated into isotactic polypropylene (iPP), and the isothermal crystallization behavior of iPP nucleated with these compound nucleating agents was investigated by differential scanning calorimetry. Based on the classical Avrami theory and the calorimetric curves under isothermal conditions, the crystallization half-time and the Avrami index can be calculated. The results demonstrate that addition of these nucleating agents reduced the crystallization half-time and speed up the crystallization process of iPP. In addition, the nucleus density of pure and nucleated iPP was further calculated from the Lamberti model and the results illustrate that the nucleus density of iPP after addition of different compound nucleating agents was increased greatly and it was several orders of magnitude higher than that of pure iPP. [ABSTRACT FROM AUTHOR]

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The isothermal and non-isothermal crystallization kinetics of PLA/PBS at the blend ratio of 90/10 by mass containing 0.1% of talc was studied by differential scanning calorimetry. In this study, Avrami and Tobin equations were used to explain isothermal crystallization kinetics. The results of both theoretical models offered the same trend results which were the different crystallization temperatures influenced crystallization rate and the amount of crystallinity. It was found that at 100 °C is the temperature for the fastest of the completion of the crystallization blending process. Both models were also used to calculate the overall kinetic rate constant, n value, half-time of crystallization and growth rate. They indicated that growth dimension was three-dimensional which is the spherulitic growth from instantaneous nuclei of heterogeneous nucleation and occurred from talc. For non-isothermal crystallization kinetics, Jeziorny and Ozawa equations were used to explain. The results from Jeziorny equation show that there are two stages of crystallization at high cooling rate, the straight line in the primary stage followed by the nonlinear line in the secondary stage. It was also found that Jeziorny crystallization rate increased when the cooling rate increased. However, the Ozawa model was inappropriate for describing the non-isothermal crystallization for these blends. [ABSTRACT FROM AUTHOR]

The Poly-Lactic Acid (PLA), the often used material for 3D printing and the rapid prototyping is very important in development process in automotive industry, as well. The commercial PLA filament was chosen and isothermal melt-crystallization and melting behavior was investigated by the DSC (differential scanning calorimetry). The PLA is a semi - crystalline biopolymer but the crystallization process is slow and sensitive to the changing of the cooling rate. Avrami equation was applied to analyze the crystallization. Arrhenius equation was used to calculate the activation energy and the equilibrium melting temperature was determined by the Hoffman-Weeks linear method. These results are the basis for further experiments.

The crystallization kinetics of Cu55Zr45 (at%) glassy alloy is studied under isothermal condition using differential scanning calorimetry (DSC). The plot of correlation between the crystallized volume fraction α and annealing time t shows a sigmoid‐type curve, which is steeper with higher annealing temperature. Furthermore, in isothermal crystallization condition, local activation energy Eα values, determined using the Arrhenius equation, range from 181.1 to 187.8 kJ/mol, which is nearly a constant. The local Avrami exponent n(α) values, obtained by the Johnson‐Mehl‐Avrami equation, which range from 2.2 to 4.0 at different annealing temeperatures, which indicates that the crystallization mechanism is diffusion‐controlled transformation. Moreover, n(α) becomes greater with increasing annealing temperature, which indicates that annealing temperature can affect nucleation rate and growth type. [ABSTRACT FROM AUTHOR]