Search

In bubble assisted vacuum thermoforming, measuring pressure-induced mechanical strains through the stereo-digital image correlation (stereo-DIC) technique while shaping thermoplastic sheet requires consideration of an appropriate reference state of surface deformations. However, when the stereoscopic measurements can be only performed after the heating step, the correlation problem should be well-posed otherwise the reliability of results is limited. This study focuses on stretching by bubble inflation processes following thermal warpage and sagging of initially flat sheets. For this purpose, an experimental rig is instrumented to heat high impact polystyrene (HIPS) sheets and to perform synchronized pressure and stereoscopic measurements during 1.5 s stretching. A two-step method is introduced to separate mechanical strains which are affected by the uncontrollable change of initial conditions from the global stereo-DIC strains. The first step relies on amplification of damped oscillations at the initiation of the inflation process due to sagging. Out-of-plane displacements confirm the existence of a temperature-dependent characteristic time that marks the transition from the sagged to the strained surface shapes. The second step uses these characteristic times to objectively shift the reference of image-correlation computations. To evaluate the effectiveness of the suggested method, inaccuracy levels of global strains are evaluated at a fixed pressure level under different thermal conditions. It is shown that inaccuracy levels are the highest when stereo-DIC measurements followed warpage and they decrease with amplification of sagging. The developed approach extends the use of in-situ stereo-DIC measurements when changes of initial conditions are uncontrollable and thermal strains cannot be measured. [ABSTRACT FROM AUTHOR]

Abstract: Bio‐based polyamide 11 (PA11)–graphene nanoplatelets (GNP) nanocomposites with different filler concentrations were prepared by melt extrusion using a masterbatch dilution process. Graphene platelets are uniformly distributed into the polymer matrix as revealed by scanning electron microscopy. The incorporation of graphene significantly improves the electrical conductivity and dielectric constant of PA11. GNPs favors the matrix crystallization; crystallization temperature and degree of crystallinity of the nanocomposites tend to increase with increase in graphene loading. Tensile properties (strength and modulus) are slightly improved by the incorporation of GNP into the PA11 matrix (up to +25% and +56%, respectively, for 5 wt% GNPs) at the expense of ductility (elongation at break divided by 5 for 5 wt% GNPs). [ABSTRACT FROM AUTHOR]

Key relationships between foam morphologies and melt‐state rheological parameters are here exposed for biobased poly(butylene‐succinate) (PBS) and standard petrobased polyethylene (PE) foams processed by single‐screw extrusion. Scanning electron microscopy followed by image analysis revealed cell diameters and densities in the range of 250–700 µm and 3–4.104 cells/cm3, respectively. PBS and PE have similar morphologies except for cell diameters which are slightly higher for PBS foams. The melt index roughly controls foam microstructures but deeper insights are obtained through correlations with shear/extensional rheology experiments. In particular, the melt strength and the strain hardening control the cell growth mechanisms. Concerning the cell density, the shear viscosity in the die plays a key role and agreements with nucleation theories can be discussed based on simulated pressure–velocity profiles using finite element software. In our extrusion conditions, the residence time comes out to have a crucial role with distinct behaviors between PE and PBS indicating a potential modification of the polymer/CO2 interfacial tension. Consequently, an accurate control of the foam morphology seems achievable via a careful selection of the polymer grades and PBS represents a promising alternative to PE for further developments of biobased foams. POLYM. ENG. SCI., 58:503–512, 2018. © 2017 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

This article aims to investigate the flexural creep behaviour as a function of temperature of long glass fibre polyamide 6.6 taking into account the thermal-oxidative degradation occurring during the test. The mould geometry has been chosen so as to reproduce some geometrical accidents (e.g. sharp frontal and tangential steps) occurring on industrial moulds. The nominal fibre content (10, 40 and 55 wt%), initial fibre length (short glass fibre, long glass fibre), load rate (up to 70%) and creep temperature (23℃, 100℃ and 130℃) have been considered to estimate the Findley’s model coefficients. A first investigation on the polyamide 6.6 degradation under thermo-oxidative environment has been led to understand the mechanisms of thermal-degradation of the polyamide 6.6 composites. The pure polyamide 6.6 matrix has shown a 20% increase of flexural modulus during the first period of ageing attributed to a combined chain scissions and cross-linking reactions. Then, a decrease of properties attributed to predominant chain scission mechanism was noticed after 1000 h of thermal exposure reaching up to 30% after 5000 h. In case of reinforced polyamide 6.6, the flexural properties tend to increase (+6.5%) up to 2000 h of exposure. The least square method has then permitted to evaluate the material coefficients from the experimental data; the instantaneous creep strain has been estimated from a power law representation. In any cases, the calculations are in a good accordance with experimental measurements. [ABSTRACT FROM AUTHOR]

The energy-harvesting efficiency of melt processed polyamide 11 (PA11) films and its nanocomposites have been investigated as a function of filler type and content. In the present work, nanoclays have been used as structural modifiers in a PA11 matrix. The nanocomposites were prepared using layered clays, Cloisite 20A, 10A, and Na+, by extrusion process through varying the filler content, 1, 2, 4, and 5 wt.%. The crystalline structure of these nanocomposites has been studied by X-ray diffractometer. It has been demonstrated that layered silicates are not significant for the structural quality of the obtained nanocomposites. Regarding the interlayer peak of different clays, it has also been revealed that Cloisite 20A is partially exfoliated, whereas 10A and Na+are totally exfoliated in the PA11 matrix. From mechanical and dynamic mechanical analyses, it was found that the addition of layered silicates results in an increase in mechanical properties. The piezoelectric strain coefficientd33and dielectric constantεRhave been measured on polarized films at ambient temperature. Among all the prepared nanocomposites only Cloisite Na+-loaded PA11 nanocomposites showed the best piezoelectric constant. This observation showed that piezoelectric constant not only depends on the crystalline phases but also on the nature of the filler. Cloisite Na+is more polar than other modified clays and high polarity leads to a better polarization response. A specific method for the quantification of energy vibration recovery has been developed for these nanocomposites. The capabilities of vibrational energy recovery were studied on PA11 loaded with Cloisite Na+. [ABSTRACT FROM AUTHOR]

This paper focuses on the development and the validation of flexural modulus and flexural strength predictive models of long glass fibre reinforced polyamide 6.6 (PA66). Based on previous injection moulding optimization of 40 wt% long glass fibre PA66, a microstructure analysis was investigated on glass fibre reinforced PA66 by varying the parameters of the material (fibre length, fibre content, fibre diameter). In a first phase, analytical models established within the framework of the processing condition limits previously determined have been elaborated. These models lead to a good experimental/calculation correlation but remain limited to a mould and part design. In a second phase the flexural modulus and maximal flexural stress have been then estimated from structural models based on a five layer morphological description of the composites (local residual fibre length, local fibre content and fibre orientations). The long glass fibre PA66 composites were characterized in terms of fibre content distribution model and fibre orientation model through the part thickness. The experimental/model correlation was achieved whatever the process variability is (mould, material and processing conditions) both for the flexural modulus or flexural strength. The models have been then validated with an industrial part. Finally, a correlation between the two studied properties has been revealed depending on the nature of the composite matrix (PA66, PA6 or PP). [ABSTRACT FROM AUTHOR]

This paper aims at improving the mechanical behavior of biobased brittle amorphous polylactide (PLA) by extrusion melt-blending with biobased semi-crystalline polyamide 11 (PA11) and addition of halloysite nanotubes (HNT). The morphological analysis of the PLA/PA11/HNT blends shows a strong interface between the two polymeric phases due to hydrogen bonding, and the migration of HNTs towards PA11 phase inducing their selective localization in one of the polymeric phases of the blend. A 'salami-like' structure is formed revealing a HNTs-rich tubular-like (fibrillar) PA11 phase. Moreover, HNTs localized in the dispersed phase act as nucleating agents for PA11. Compared to neat PLA, this leads to a remarkable improvement in tensile and impact properties (elongation at break is multiplied by a factor 43, impact strength by 2, whereas tensile strength and stiffness are almost unchanged). The toughening mechanism is discussed based on the combined effect of resistance to crack propagation and nanotubes load bearing capacity due to the existence of the fibrillar structure. Thus, blending brittle PLA with PA11 and HNT nanotubes results in tailor-made PLA-based compounds with enhanced ductility without sacrificing stiffness and strength. [ABSTRACT FROM AUTHOR]

This work aims at numerically simulating the flow of nanocomposites in a twin-screw mixer so as to develop a prediction tool of nanofiller dispersion and distribution in a polymer matrix during processing. The rheological behaviour of polyamide 6 / carbon nanotubes blends (PA6/MWCNT) containing from 1 to 5 wt.% of MWCNT was investigated over a large range of shear rates (0.1 to 100 s-1) and temperatures (230 to 245 °C). The macroscopic dispersion of the nanotubes was assessed by dynamic rheometry. Viscosity laws of the nanocomposites were characterized and implemented in a finite element software package to compute the velocity, pressure and temperature fields during the mixing process. A good agreement was founded between the calculated and measured torques. The dispersive and distributive capability of the flow was numerically evaluated and compared to the nanotubes dispersion quality experimentally qualified by oscillatory rheometry. Experimental and numerical results are complementary and allow better understanding the mixing capability of the twin-screw mixer used to compound nanocomposites. [ABSTRACT FROM AUTHOR]

This article aims at preparing and characterizing efficiency of melt-extruded polymer nanocomposites-based drug delivery systems with tailored drug release properties. 5-aminosalycylic acid (5-ASA)-loaded halloysite nanotubes (HNT)/plasticized starch nanocomposites were prepared and evaluated for the drug release, swelling characteristics, and degradability. The structure, morphology, and properties of the nanocomposites were characterized by using Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and UV-visible spectrophotometry. The 5-ASA and HNT hybrid formation is confirmed, as well as the presence of 5-ASA within the HNTs and an excellent dispersion of the 5-ASA/HNT hybrid in the thermoplastic starch matrix. The swelling of nanocomposites strongly depends on the temperature but not on pH. The degradability tests yield a stabilized weight loss of 24 wt%, which is ascribed to leaching of plasticizers. The presence of HNTs delays the drug release process. The observed in vitro drug release after 2 h is 37.2% for plasticized starch and 30.0% for the nanocomposites. Overall results indicate that the developed nanocomposite system can be a potential candidate for drug delivery applications. POLYM. ENG. SCI., 55:573-580, 2015. © 2014 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Nanocomposites reinforced with hybrid fillers of carbon nanotubes (CNTs) and clays were developed, aiming at enhancing the dispersion of nanofillers with balanced mechanical properties while lowering the cost of the final product. Polypropylene-based nanocomposites were prepared by the master batch dilution technique with varying combinations of CNTs and clays as fillers by using commercially available highly concentrated master batches of polypropylene/organoclays and polypropylene/multiwalled carbon nanotubes using high-shear twin-screw extrusion. Their mechanical and morphological properties were then evaluated. It was shown that the addition of hybrid filler to polypropylene enhanced the ductility and flexural properties of nanocomposites, confirming the synergistic effect of nanofillers as a multifunctional fillers. The novelty of this work lies in the synergy arising from the combination of two nanofillers with unique dimensions and aspect ratios as well as different dispersion characteristics, which have not been specifically considered previously. [ABSTRACT FROM AUTHOR]

ABSTRACT Immiscible PET/PE blends (80/20 wt %) were prepared on an industrial twin-screw extruder with and without different types of commercially available montmorillonites (Cloisite® C15A, C10A, and 30B), containing organic surfactants differing by their polarities and their thermal stability). XRD and TEM observations evidence an intercalated structure, C15A leading to a better dispersion compared to C30B and C10A. The size of the PE dispersed phase decreases upon addition of organoclays (OMMT), suggesting an efficient compatibilization. The most efficient compatibilizing effect is observed in the case of C15A (smallest droplet size and narrowest size distribution). Nevertheless, elongation at break in tension and impact strength of PET/PE blends drastically decrease upon addition of OMMT, whatever the organoclay added, due to a possible degradation of the clay surfactant during melt compounding, which counteracts the nanofiller compatibilization effect. Furthermore, similar PET/PE/OMMT blends prepared at a lab scale using a microcompounder are ductile contrary to those compounded in the industrial extruder, which show a brittle behavior. This difference was ascribed to the extrusion residence time (much higher in an industrial extruder than in a lab micro-compounder), which appeared to be a key parameter in controlling the clay surfactant degradation and thus the end-use properties of such immiscible blends. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39712. [ABSTRACT FROM AUTHOR]

This article is part of an ambitious project. The aim is to simulate mechanical properties of rotomolded part from microstructure consideration. Main objective here is to consider metallocene polypropylene crystallization kinetic (PP) during cooling stage in rotational molding. Crystallization kinetic of metallocene PP is so rapid that microscopy cannot help to observe nucleation and growth. Crystallization rate can be estimated by a global kinetic. Given that cooling in rotational molding is dynamic with a constant rate, Ozawa law appears more appropriate. Ozawa parameters have been estimated by differential scanning calorimetry. In rotational molding thermal condition, Avrami index identifies a complex nucleation intermediate between spontaneous and sporadic. Ozawa rate constant is 68 times higher than this obtained for Ziegler-Natta PP. By coupling transformation rate from Ozawa model and a thermal model developed earlier, the difference between theory and experimental is less than 1%. To optimize rotational molding, study has been completed by sensitivity to adjustable parameters. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]

Partly bio-based segmented thermoplastic polyurethane (TPU) formulations were developed to fulfill the requirements of the reactive rotational molding process. They were obtained by one-shot bulk polymerization between an aliphatic diisocyanate (1,6-hexamethylene diisocyanate), a polyether polyol as macrodiol (polyethylene glycol) and a biobased corn-derived 1,3-propanediol as chain extender (CE), in presence of a catalyst, at an initial temperature of 45°C. Equivalent TPU formulations with classical petroleum-based 1,3-propanediol were also prepared for a purpose of comparison. TPU with different soft to hard segment (SS/HS) ratios were synthesized by varying the macrodiol and CE concentrations in the formulations. For each formulation, the evolution of the reaction temperature as a function of time was monitored and the kinetics of polymerization was studied by Fourier Transform infrared spectroscopy in attenuated total reflection mode (FTIR-ATR). The morphology, thermal properties, solubility in different solvents and tensile properties of the final products were analyzed. All synthesized polyurethanes are 100% linear polymers and the extent of microphase separation, as well as the thermal and mechanical properties highly depends on the HS content, and glass transition temperature and Young modulus can be tuned by adjustment of the SS/HS ratio. All results indicate that petrochemical CE can be replaced by its recently available corn-derived homologue, without sacrificing any use properties of the final polyurethanes. [ABSTRACT FROM AUTHOR]

Low odour-emissive polylactide/cellulose fibre biocomposites, intended for car interior, were prepared and characterised. The impact of the different stages of processing (drying cycles, compounding, injection moulding) on the extent of polylactide degradation and on biocomposites properties was investigated by size exclusion chromatography, thermogravimetry, differential scanning calorimetry. In parallel, the odour emission of these materials was quantified via dynamic dilution olfactometry and Field of odours® method. The changes in molecular weight and global odour emission indicated that compounding had a strong impact on polylactide degradation and odour emission, while injection moulding had no significant impact. Adding 0.5 wt% of an absorbent agent based on poly(1-methylpyrrol-2-ylsquaraine could) divide the global odour concentration by a factor 2. The morphology, mechanical and thermal properties of injection moulded PLAbiocomposites were not affected by the presence of the absorbent agent [ABSTRACT FROM AUTHOR]

Poly(ethylene terephtalate)/poly(ethylene) (PET/PE) blends (80/20 wt %) were prepared by melt-extrusion and compatibilized by addition of nanoclays. Two commercially available organically modified montmorillonites (Cloisite© 10A and 30B) were chosen as reference and a third one was specially organomodified at lab scale with a thermally stable phosphonium surfactant using conventional cationic exchange reaction. The size of the dispersed polymer phase (PE droplets) and the ductility of the blends depend more on the thermal stability of the surfactant of the organomodified clay than on the enthalpic interactions between the blend components and the surfactants used for the modification of the clays. The highest mechanical properties (yield stress and elongation at break) and the better compatibilization efficiency (smallest dispersed PE droplets) were observed in the presence of phosphonium organomodified montmorillonite compared to other less thermally stable commercial organoclays. The analysis of the thermal stability, morphology, and mechanical properties of PET/PE blends containing the surfactants alone in the absence of clay made it possible to evidence separately the effects of the surfactant and of the nanofiller. The role of the surfactant as compatibilization agent was demonstrated. In the absence of nanofiller, the finest morphological and highest ductility were again obtained with the phosphonium surfactant which is the most thermally stable. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]

Starch-grafted polypropylene (PP-g-starch)/organoclay nanocomposites were melt-compounded using a corotating twin-screw extruder. Homopolymer or copolymer-based polypropylene-grafted maleic anhydrides (PP-g-MA) with different molecular weights and different maleic anhydride (MA) grafting levels were added at different weight contents as compatibilizer. Two organo-modified montmorillonites were used, the first one containing polar functional groups (Cloisite®30B) having affinity to the starch phase, and the other one containing non polar-groups (Cloisite®20A) having affinity to the polypropylene phase of the polymer matrix. Whatever the MA grafting level and the molecular weight and content of PP-g-MA, no significant immiscibility of PP-g-starch/PP-g-MA blends is evidenced. Regarding clay dispersion, adding a low content of ethylene-propylene copolymer-based PP-g-MA compatibilizer having a high MA-grafting level, and a polar organoclay (Cloisite®30B) is the most desirable formulation to optimize clay intercalation and exfoliation in PP-g-starch. Nevertheless, regarding the reinforcement effect, whatever the PP-g-MA compatibilizer, the addition of non polar organoclay (Cloisite®20A) is preferably recommended to reach higher tensile properties (modulus, yield stress, strength) without significant loss of ductility [ABSTRACT FROM AUTHOR]

This paper aims at highlighting the influence of different additives (carbon black and nucleating agents) on both the notched and unnotched Charpy impact properties of long glass fibre reinforced poly(ethylene terephtalate) injection mouldings. The relationship with the polymer matrix and composite microstructure modifications (variations of crystalline morphology and local fibre content) was investigated. Adding carbon black alone decreases the impact performances. This highly conductive additive actually increases the cooling rate, and therefore the fibre 'frettage' effect (higher internal stresses). It also acts as filler, which increases the material brittleness. The nucleating agents allow reducing the mould temperature, but their effect on the impact strength may be favourable or not depending on the processing temperatures. The addition of such additives induces perturbations of the polymer melt rheology in the mould cavity and of the cooling kinetics of the part, which both act on the fibre distribution during mould filling and on the degree of crystallinity of the composite parts. [ABSTRACT FROM AUTHOR]

The effect of injection molding parameters (screw rotational speed, back pressure, injec-tion flow rate and holding pressure) on the nanofiller dispersion of melt-mixed PP/clay nanocomposites was investigated. The nanocomposites containing 4 wt% clay were obtained by dilution of a PP/clay masterbatch into a PP matrix. The evaluation of the dispersion degree was obtained from dynamic rheological measurements. The storage modulus and complex viscosity exhibit significant dependence on the injection molding parameters. PP/clay nanocomposite molded using more severe injection parameters (high shear and long residence time) displays the highest storage modulus and complex viscosity, which illustrates the improved dispersion of clay platelets. This better dispersion leads to better mechanical properties particularly higher Young modulus, tensile strength and unnotched impact strength. A Taguchi analysis was used to identify the influence of individual process parameters. The major individual parameter is the injection flow rate, whose increase improves nanoclay dispersion. The combination of high back pressure and high screw rotational speed is also necessary to optimize the dispersion of clay nanoplatelets. [ABSTRACT FROM AUTHOR]

The article discusses a study regarding the use water-injection as intercalating and exfoliating aid as an efficient one-step melt-compounding of copolyetheramide and pristine clay nanocomposites. The study examines the role of water injected into the melt in the filler dispersion and the prevention of the matrix from degradation during melt-extrusion. It also reveals the effects of the nanofiller dispersion on the mobility of the macromolecules.

Halloysites/polypropylene nanocomposites with different nanotubes contents were prepared by diluting a masterbatch containing 30 wt.% halloysites with polypropylene (PP). Unmodified (HNTs) and quaternary ammonium salt treated (QM-HNTs) halloysite nanotubes were used. Both degree of crystallinity and crystallization temperature increase upon addition of halloysites into PP, thus indicating a potential nucleation effect induced by the nanotubes. An homogeneous distribution and dispersion of nanotubes was observed throughout the PP matrix, with a slightly better dispersion in the case of modified QM-HNTs compared to unmodified HNTs. Mechanical tests in tension, bending and notched impact demonstrated that strength and modulus of the nanocomposites significantly increase with addition of halloysites without significant loss of ductility. An halloysite content of 6 wt.% appears as an optimum. Modified halloysites (QM-HNTs) lead to globally better performances due to strong interfacial interaction between the polymer matrix and the nanotubes. [ABSTRACT FROM AUTHOR]

Different concentrations of multi-wall carbon nanotubes (MWNTs) filled polypropylene (PP) nanocomposites were prepared through PP/MWNT masterbatch dilution process by melt compounding with a twin-screw extruder. Prepared nanocomposites were characterized for their electrical resistivity and dielectric properties. The experimental results revealed that incorporation of MWNTs in PP matrix had decreased the electrical resistivity and increased the dielectric constant at low dielectric loss. The electrical conductivity and dielectric constant of PP/MWNT nanocomposites increased significantly near the percolation thresholds, which is equal to 2 wt.% of MWNTs. The PP nanocomposite containing 5 wt.% MWNT exhibited a high dielectric constant under wide sweep frequencies attended by low dielectric loss. Its dielectric constant is >110 under lower frequency, and remains the same in the entire frequency range. Interestingly, dielectric constant values of the prepared nanocomposite systems have weak or nil frequency dependence in the entire frequency range. Morphological characterization was done using scanning electron microscopy (SEM) and it was observed that nanotubes are distributed reasonably uniformly indicating a good dispersion of nanotubes in the PP matrix. The obtained results indicate that a common commercial plastic with good comprehensive performance, which exhibited the potential for applications in advanced electronics, was obtained by a simple industry benign technique. [ABSTRACT FROM AUTHOR]

The article discusses a study which examined the efficiency of two fatty acid amides in influencing the effect of ethylene vinyl acetate (EVA) addition in multilayer polyethylene (PE)/maleic anhydride grafted (PE) (PEgMAH)/polyamide 6-66 packaging films. It notes that the existence of adjacent layers and the presence of EVA in the PE and PEgMAH layers have contributed to the migration of slip additives toward the PE layer's outermost surface.

The article presents a study on nanocomposites based on polypropylene (PP) and unmodified Montmorillonite. To promote clay dispersion, various aqueous suspensions that have cationic or anionic surfactants, and a compatibilizers were injected during extrusion. According to the study, cationic suspensions ease the dispersion of clay platelets in the PP matrix. Efficiency to disperse clay in the polymer matrix was demonstrated by the mechanical and thermal characterizations of the nanocomposites based on cationic surfactants.

Carbon nanotube reinforcement is a key emerging technology to simultaneously impart enhanced mechanical properties while adding multifunctional characteristics to polymer materials and systems. The promise of extraordinary improvement in-end use properties of polyolefin/carbon nanotube hybrid systems has spurred great interest and intensive activity in academics and industries. This review offers a comprehensive discussion of the preparation, compounding, properties and applications of such nanocomposites. The processing, dispersion and orientation of nanotubes, as well as the Characterisation of physical and mechanical properties of carbon nanotube filled polyolefins are discussed. In particular the scientific principles and mechanisms in relation to the methods of manufacturing are highlighted, with an outlook towards commercial applications. [ABSTRACT FROM AUTHOR]

This paper aims to identify the main parameters that influence the mechanical properties of long-glass-fibre-reinforced poly(ethylene terephtalate) parts in order to optimise the potential of these composites. A Taguchi design of experiments (DOE) was used for this purpose. The shape of the injection-moulded specimen was representative of the complexity of industrial parts (presence of sharp frontal and tangential steps). The mechanical properties (bending and Charpy impact tests) were measured at different locations in the part in order to highlight anisotropy. Variance analysis has shown that holding pressure, injection speed, and mould temperature are the most effective processing parameters. It has also shown that the optimised parameter sets that lead to the highest flexural strength on the one hand and the highest impact strength on the other hand are different, the polymer melt and mould temperatures being opposite. Finally, microstructure analysis has shown a fibre content gradient along the flow axis, which is greatly amplified by the presence of geometrical accidents (frontal and tangential steps) including the reorientation of fibres in the flow direction at the end of the parts. [ABSTRACT FROM AUTHOR]

Examines the evolution of structure in films of polyamide-6 drawn on Cellier tenter frame laboratory tester under conditions of simultaneous equibiaxial stretching and planar uniaxial stretching. Utilization of the tilted film method to obtain trichroic spectra; Observations on the molecular orientation of crystalline structure; Combination of infrared trichroism with the analysis of the structural factor spectra.

Results from systematic gas sensing experiments on polymer coated surface-transverse-wave (STW) and surface-acoustic-wave (SAW) based two-port resonators on rotated Y-cut quartz, operating at the same acoustic wavelength of 7.22 μm, are presented. The acoustic devices are coated with chemosensitive films of different viscoelastic properties and thicknesses, such as solid hexamethyldisiloxane (HMDSO), semisolid styrene (ST), and soft allyl alcohol (AA). The sensor sensitivities to vapors of different chemical analytes are automatically measured in a sensor head, evaluated, and compared. It is shown that thin HMDSO- and ST-coated STW sensors are up to 3.8 times more sensitive than their SAW counterparts, while SAW devices coated with thick soft AA-films are up to 3.6 times more sensitive than the STW ones. This implies that SAWs are more suitable for operation with soft coatings while STWs perform better with solid and semisolid films. A close-to-carrier phase noise evaluation shows that the vapor flow homogeneity, the analyte concentration, its sorption dynamics, and the sensor oscillator design are the major limiting factors for the sensor noise and its resolution. A well designed ST-coated 700 MHz STW sensor provides a 178 kHz sensor signal at a 630 ppm concentration of tetra-chloroethylene and demonstrates short-term stability of 3×10-9/s which results in a sensor resolution of about 7 parts per billion (ppb). [ABSTRACT FROM PUBLISHER]

This paper reports the second part of the results from the round robin test program proposed by the Society of Interfacial Materials Science (SIMS) to characterise the interlaminar fracture behaviour of E-glass woven fabric reinforced vinylester composites. Special emphasis was placed on the study of loading direction (i.e. weft and warp directions) effect on interlaminar shear strength and fracture toughness. Ten laboratories worldwide participated in this test (Table 1). Each laboratory was supplied with composite laminates and conducted the tests according to its own procedure. The results showed that although there were large variations in absolute magnitude between laboratories, a general trend was established with higher interlaminar fracture resistance in the weft direction than in the warp direction for a given silane agent. The larger number of strands running in the warp direction with rougher, more undulating areas perpendicular to the direction of crack propagation was mainly responsible for this result. The results also confirmed the previous finding that the mode I interlaminar fracture toughness increased with increasing silane agent concentration. [ABSTRACT FROM AUTHOR]

A round-robin test programme has been carried out to characterise the mode I interlaminar fracture behaviour of E-glass woven fabric reinforced vinyl ester matrix composites. Special emphasis has been placed on the effect of silane coupling agent on the stability of interlaminar crack propagation and fracture toughness. Sixteen laboratories participated in this programme. Each laboratory was supplied with composite laminates of thicknesses of its own choice and conducted the tests according to its own procedures. The results showed that variations in interlaminar fracture toughness between laboratories were very large in spite of slight differences in the test procedures used, such as specimen dimensions, test speed and data reduction schemes. Nevertheless, the general trends were clearly identified with respect to different silane coupling agents. Other observations and the implications are discussed. [ABSTRACT FROM AUTHOR]

An editorial is presented on the future for polymers in tomorrow's electric and autonomous vehicles. The article discusses that he growing market for electric vehicles and the advanced digital technologies of autonomous driving which are likely to redefine the use of polymers in the auto industry; and electric vehicles emitting less heat than internal combustion engine cars, a broader range of commodity plastics could be used in place of costly engineering plastics.

The article offers information on the Polymer composites were initially adopted and became popular in transportation sectors to manufacture structural and semi-structural parts driven by their superior strength and stiffness-to-weight ratio. It mentions polymer composites are destined to evolve to remain attractive and competitive; and also mentions collaborations between academic and industrial players are the key to develop innovative solutions.

An editorial is presented on the application of eletcro-active polymers, particularly piezoelectric polymers for the design of energy harvesters integrated into wearable connected devices. Topics discussed include application of three-dimensional printing for designing complex architectures, lower cost of using blending polymers and investigation for biobased solutions.

The author reflects on the application of additive manufacturing (AM) or the three-dimensional (3D) printing in polymer and plastic processing. Topics discussed include its advantages in manufacturing industry considering various aspects including design freedom, complexity, and texturing, the several 3D-printing processes which includes laser sintering, fused deposition, and stereolithography, and the several issues related to the application of the process.

The author reflects on the medical plastics being used in healthcare. The author mentions that plastics have been widely used in various medical applications including surgical implants, tubing, and bioresorbable items. She states that medical plastics can be considered as candidate to replace metal in medical services. She adds that manufacturing technologies have been helping medical plastics to become obtain precision, labour cost reduction, and process reliability.