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Agave Tequilana Weber (ATW) is the base ingredient for preparing tequila liquor; tequila production yields tons of waste rich in cellulose representing environmental issues. Cellulose nanocrystals (CNC), the crystalline regions extracted from cellulose microcrystals, were obtained from the waste of ATW as an attractive alternative to reinforce polymeric materials. CNC were grafted with (poly (2-ethyl hexyl acrylate) to improve compatibility with hydrophobic polymers. The CNC pristine (CNCP) and grafted (CNCG) were dispersed in PLA (0.5, 1 and 2 wt.%), employing several melt processing stages. CNC distribution within PLA matrix was followed using SEM and TEM. Also, thermal properties were characterized through differential scanning calorimetry and thermogravimetric analysis. Thermal stability of nanocomposites increased with CNC, CNCG nanocomposites showed better results (Td ~ 370 °C) than CNCP nanocomposites (Td ~ 366 °C). The degree of crystallinity showed for CNCG (25.1%) was higher than for CNCP (21.1%) nanocomposites. The tensile properties were improved with CNCP (0.44 MPa) and CNCG (2.11 MPa) content. The CNC increased the shear properties of PLA melt and exhibited a strain-hardening behavior during elongational rheology test. The CNC and CNCG are an interesting alternative to modify the melt rheological behavior and the mechanical behavior in the solid-state of low melt strength polymers, which could be thermally degraded during processing. Composites could be used to produce films for the food industry through blow-extrusion processing. [ABSTRACT FROM AUTHOR]

Thermoplastic starch, as an eco-friendly alternative to petroleum-based plastics, possesses numerous advantages, including cost-effectiveness, complete biodegradability, and renewable sourcing. Nevertheless, the plasticizer dispersion and starch plasticization efficiency are poor via the processing method dominate by shear deformation. Thus, the aim of this study is proposing a new approach combining ultrasonic treatment and elongational rheology to prepare thermoplastic starch and evaluate its properties. This innovative approach facilitated the production of thermoplastic starch with glycerol as the plasticizer at varying rotor speeds. Furthermore, this study was carried out by using a self-developed ultrasonic-assisted vane mixer (UVM) based on elongational flow. The samples were analyzed using FTIR, WAXD, polarized optical microscope, dynamic rheometer, universal testing machine and thermogravimetric analysis. FTIR and dynamic rheological analysis showed that elongational rheology and ultrasonics stimulate hydrogen bond formation between starch and glycerol, elevating starch thermoplasticity. Tensile tests and thermogravimetric analysis highlighted that high-intensity elongational field improved the mechanical properties and thermal stability of the thermoplastic starch. Additionally, the incorporation of ultrasonic treatment yielded further improvements, yielding remarkable tensile strength (6.09 MPa) and elongation at break (139.3 %). This synergistic interplay between ultrasonics and elongational rheology holds immense potential for advancing thermoplastic starch manufacturing. [ABSTRACT FROM AUTHOR]

Thin films with (nano)fibrillar morphologies were successfully obtained in fully‐biobased poly(butylene succinate‐co‐adipate)/poly(amide‐11) blends (PBSA/PA11, 85/15 wt/wt) using an extrusion‐blowing process. Impacts of PA11 grade and take‐up ratio on the morphology of PBSA/PA11 were particularly highlighted. Scanning electron microscopy analyses indicated that PA11 with high melt volume‐flow rates are beneficial to the development of (nano)fibrillar morphologies in PBSA/PA11 blown film. On the contrary, unstable film blowing processing without fibrillar morphologies was attested for PA11 with low melt volume‐flow rates. Increasing the take‐up ratio during extrusion‐blowing of PBSA/PA11 clearly generates finer PA11 (nano)fibrils into PBSA. Fibril diameters down to 300 nm could be reached with an optimal PA11 grade promoting enhanced mechanical properties (higher ductility and toughness). The formation of stable PA11 (nano)fibrils into PBSA is discussed via rheological assessments of viscosity/elasticity ratio. A specific attention was finally paid to the PBSA strain‐hardening behavior in PBSA/PA11 using elongational rheological tests. PA11 (nano)fibrillation helps maintaining the strong PBSA strain‐hardening and thus play a major role on the processability of PBSA/PA11 blends by extrusion blowing. As a conclusion, the PA11 grade represents a crucial parameter to control the production of PBSA/PA11 blown films with refined (nano)fibrillar structures and enhanced physico‐chemical properties. [ABSTRACT FROM AUTHOR]

Polypropylene random copolymer (PPR) and polybutene-1(PB-1) are blended and long-chain branched (LCB) in the reactive extruder. The optimum amount of PB-1 resin, peroxide (DCP) and trimethylolpropane triacrylate (TMPTMA) for long-chain branching of PPR and probe topology formed by the branches were investigated. Fourier transformed infrared spectroscopy (FTIR) used to measure the branching degree and efficiency as well as obtaining TMPTMA grafts on PPR. Oscillatory shear rheological properties including complex viscosity, storage modulus, loss tangent, and uniaxial elongational rheometry were studied to differentiate the LCB-PPR from unmodified PPR with almost similar molecular weight samples. The LCB structure modified samples with TMPTMA and DCP, prominent higher zero-shear viscosity, longer relaxation time and pronounced strain-hardening behavior. It was found that different amount of DCP and TMPTMA can affect strain-hardening behavior and topology of branches and subsequently the foaming ability. PB-1 resin found to have a positive effect because of more sensibility to β-scission degradation and mobilizing effects. The optimization of PB-1 for the highest zero-shear viscosity, shear, and uniaxial rheological behavior is achieved at 10 wt% PB-1, while 0.08% of DCP and 3% of TMPTMA are optimum amounts of additives needed for long-chain branching process. The optimum blend could be a great alternative for foaming applications. [ABSTRACT FROM AUTHOR]

The properties of polymer matrix composites are related not only to the chemical composition of the materials but also to the processing equipment used for their preparation which has a direct influence on the microstructure of the composites. In this paper polypropylene (PP)/multi-walled carbon nanotubes (MWCNTs) nanocomposites were prepared by melt blending through a self-developed, eccentric rotor extruder (ERE). The structure and elongational deformation mechanism of an ERE were described in detail. The morphological, rheological, thermal and mechanical properties of the resulting PP/MWCNTs nanocomposites were investigated. Scanning electron microscopy (SEM) and rheological analysis showed that the MWCNTs were well dispersed in the PP matrix. The thermal stability was investigated by thermogravimetric analysis (TGA) and indicated that the addition of MWCNTs could effectively improve the thermal stability of pure PP. The percentage of crystallinity and tensile strength of the composites were improved as a result of the heterogeneous nucleation effect of the MWCNTs in the PP matrix. The research results revealed that the enhancement of the properties of PP/MWCNTs composites could be attributed to a better dispersion of the MWCNTs in the matrix as compared to samples prepared by conventional extrusion. [ABSTRACT FROM AUTHOR]

In this work, polypropylene/poly(ethylene-cooctene)/ multiwalled carbon nanotube (PP/POE/MWCNT) nanocomposites with different contents of MWCNTs were prepared by an eccentric rotor extruder to obtain engineering materials with excellent performance capability. Microphotographs (scanning electron microscopy and transmission electron microscopy) and dynamic mechanical analysis indicate that the MWCNTs were well dispersed in the polymer matrix under the elongation flow. The crystallization behavior was explored by X-ray diffraction and differential scanning calorimetry. The results show that MWCNTs promote heterogeneous nucleation and improve the To, Tc and Te values of the composites. On the basis of the rheology analysis, the complex viscosity of the PP/POE/MWCNT composites increased and formed an obvious Newton plat in the low-frequency range; both the G' and G" of all the samples increased monotonically, and a percolation threshold appeared for 1 wt% MWCNTs. Thus, the mechanical properties of the nanocomposites prepared under an elongation flow lead to an effective strengthening of PP/ POE better than under a shear flow. This work provides a novel method based on elongational rheology to prepare engineered materials that possess excellent performance capabilities. [ABSTRACT FROM AUTHOR]

In this work, polypropylene/poly(ethylene-cooctene)/ multiwalled carbon nanotube (PP/POE/MWCNT) nanocomposites with different contents of MWCNTs were prepared by an eccentric rotor extruder to obtain engineering materials with excellent performance capability. Microphotographs (scanning electron microscopy and transmission electron microscopy) and dynamic mechanical analysis indicate that the MWCNTs were well dispersed in the polymer matrix under the elongation flow. The crystallization behavior was explored by X-ray diffraction and differential scanning calorimetry. The results show that MWCNTs promote heterogeneous nucleation and improve the To, Tc and Te values of the composites. On the basis of the rheology analysis, the complex viscosity of the PP/POE/MWCNT composites increased and formed an obvious Newton plat in the low-frequency range; both the G' and G" of all the samples increased monotonically, and a percolation threshold appeared for 1 wt% MWCNTs. Thus, the mechanical properties of the nanocomposites prepared under an elongation flow lead to an effective strengthening of PP/ POE better than under a shear flow. This work provides a novel method based on elongational rheology to prepare engineered materials that possess excellent performance capabilities. [ABSTRACT FROM AUTHOR]

Generally semi-crystalline thermoplastics have an inferior thermoformability compared to amorphous thermoplastics. This is because of their sharp drop in stiffness and viscosity with crystalline melting. Radiation cross-linking of semi-crystalline thermoplastics offers a solution for this limitation. The thermoformability is essential for processing, but the parts properties like the mechanical ones are important for the application of thermoformed parts. In this article the effects of mold geometry and temperature, forming temperature and film thickness on the mechanical properties of thermoformed cross-linked polyamide 12 (PA12) are investigated. The results show the improvement of the thermoformability of semi-crystalline thermoplastics by cross-linking. Concerning the mechanical properties of the parts, a significant enhancement in stiffness and tensile strength can be obtained, while the ultimate strain at break decreases compared to the smooth film's properties. Thermal processing conditions, deformations during forming and the degree of cross-linking of the film material have an influence on these effects. [ABSTRACT FROM AUTHOR]

Commercially available, blended methylhydroxyethyl celluloses with similar weight-average molar masses but varying molar mass distributions were characterized by different techniques like steady shear flow and uniaxial elongation in capillary breakup experiments. The determined relaxation times t were then correlated with the absolute molar mass distribution acquired via SEC/MALLS/DRI (combined methods of size-exclusion-chromatography, multi angle laser light scattering and differential refractometer). In order to describe the longest relaxation time of the polymers in uniaxial elongation via integral mean values of the molar mass distribution, defined blends of polystyrene standards with varying molar mass distributions were characterized. The obtained data was scaled via different moments of the molecular weight distribution and could be correlated with the results obtained for the methylhydroxyethyl celluloses.

Concentrated gypsum slurries used for wallboard production are studied using shear and elongational rheometers. It is shown that the rheological behavior of different slurry compositions can be sufficiently accurately described in the framework of the Ostwald-de Waele power law, which reproduces both shear and elongational experimemtal data with sufficiently close values of the consistency and flow behavior indexes for each slurry composition studied.

The polymer vane extruder, whose plasticating and conveying theory is based on elongational rheology, is a significant development in plastic processing equipment. As a result of its unique structure, it is desirable to use numerical simulation to study it. The results can be useful to set process parameters and optimize its structure. In this paper, numerical simulation of the mixing characteristics of the vane extruder was performed with the finite element computational fluid dynamics program POLYFLOW. To visualize the mixing process of the melts in a vane extruder based on the calculation of the transient flow, a particle tracking method was applied. By using the statistical post-processor program POLYSTAT, dispersive mixing and distributive mixing characteristics were evaluated in terms of shear rate, stretching rate, mixing index, and time average mixing efficiency. The simulation results showed that strong stretching existed in the vane extruder demonstrating that the vane extruder generated a more appropriate flow than a common twin-screw extruder to break material particles into smaller ones. The probability functions of mixing efficiency showed that the position near the outflow had the highest mixing efficiency. Furthermore, the time average mixing efficiency of most particles in the vane extruder were larger than that in a twin-screw extruder, indicating that in the vane extruder more mechanical energy was used to generate stretching. [ABSTRACT FROM PUBLISHER]

Hydrogels of different composition based on the copolymerization of N-isopropyl acrylamide and surfmers of different chemical structure were tested in elongation using Hencky/real definitions for stress, strain, and strain rate, offering a more scientific insight into the effect of deformation on the properties. In a range between $\dot {\varepsilon }=10$ and 0.01 s $^{-1}$, the material properties are independent of strain rate and show a very clear strain hardening with a 'brittle' sudden fracture. The addition of surfmer increases the strain at break $\varepsilon _{\mathrm {H}}^{\max }$ and at the same time leads to a failure of hyperelastic models. The samples can be stretched up to Hencky strains $\varepsilon _{\mathrm {H}}^{\max }$ between 0.6 and 2.5, depending on the molecular structure, yielding linear Young's moduli E $_{0}$ between 2,700 and 39,000 Pa. The strain-rate independence indicates an ideal rubberlike behavior and fracture in a brittle-like fashion. The resulting stress at break $\sigma _{\textrm max}$ can be correlated with $\varepsilon _{\mathrm {H}}^{\max } $ and $E_{0}$ as well as with the solid molar mass between the cross-linking points $M_{\mathrm {c}}^{\textrm {solids}} $, derived from $E_{0}$. [ABSTRACT FROM AUTHOR]

Electron beam-irradiated polypropylene undergoes chain scission initiated by the loss of a proton. The resulting macroradicals can lead to branched molecules. However, the understanding of the influence of irradiation on the branching of polypropylene is still scarce. Therefore, this paper investigates structure-property relationships in such irradiated polymers. In general, irradiation yields long-chain branches, which develop from a star-like into a tree-like branching architecture with increasing dose. These conclusions can be drawn from the relation between the zero shear-rate viscosity η and the weight average molar mass M as well as from the elongational behavior. [ABSTRACT FROM AUTHOR]

Despite substantial progress in analytical techniques for polymer characterization, a realistic picture of branching structure in industrial polymers still remains at large. Using a number of assumptions, structure-based constitutive models can distinguish between linear and branched structures in a qualitative sense. More detail on branching architecture, such as the number and length of side chains, the sequence in which they exist on the backbone and their contribution to polymer chain relaxation is more or less unknown. In the current study, elongational behavior of four commercial polyolefins is compared using the predictions of the MSF (molecular stress function) theory. The results will then be used to analyze the branching in a group of strain-hardening polypropylenes synthesized using single site catalyst. [ABSTRACT FROM AUTHOR]

The Capillary Breakup Extensional Rheometer (CaBER) is the only commercially available elongational rheometer. The CaBER can measure the diameter of a low viscous sample under stretching as a function of time. The analysis of this setup is consequently limited to the time dependent diameter of the capillaries D (t). Some samples do not develop a proper capillary flow, because of, for example, a lack of a substantial surface tension or a cylindrical fluid filament. As a consequence the interpretation of the results based on D (t) is problematic. On the other hand there is a huge fundamental industrial interest in measuring properties like strand formation, stickiness, spreadability, and so on. These properties are related to the extensional properties, specifically the elongational viscosity of a sample. Therefore, additional information beside D (t) is needed. In this publication a newly developed extension of the CaBER is presented and first applications are shown. The viscous sample is placed between two plates and afterward extended quickly by moving the upper plate. The normal force acting on the lower plate is measured as a function of time. To measure these small forces (<0.05 mN) with very short time resolution (e.g., dwell-times down to 0.2 ms) a piezo transducer is used in combination with modern data oversampling techniques to further increase the sensitivity of the transducer. In this article the CaBER modifications are presented in detail to simultaneously measure the diameter and the force down to 5*10-5 N, with 10-3 s time resolution. [ABSTRACT FROM AUTHOR]

A self-developed biaxial eccentric rotor extruder (BERE) based on elongational rheology was adopted to prepare natural rubber (NR)/carbon black (CB) nanocomposites continuously through one-step process in 1.5 min. The micro morphology, rubber processing analysis, binding rubber content, relaxation time, molecular weight and distribution, vulcanization and mechanical properties of the prepared NR/CB nanocomposites were tested. By comparing with NR/CB nanocomposites prepared by internal mixer, it is proved that BERE continuous mixing process can not only greatly shorten the mixing time, reduce unit energy consumption, but also make the prepared NR/CB nanocomposites have good mixing and dispersion morphology, excellent physical and mechanical properties, high molecular weight retention and binding rubber content. A self-developed biaxial eccentric rotor extruder (BERE) based on elongational rheology was adopted to prepare natural rubber (NR)/carbon black (CB) nanocomposites continuously through one-step process in 1.5 min, and the prepared NR/CB nanocomposites have good mixing and dispersion morphology, excellent physical and mechanical properties, high molecular weight retention and binding rubber content. [Display omitted] • A self-developed BERE based on elongational rheology was used to prepare NR/CB nanocomposites. • The BERE can realize one-step continuous mixing of NR/CB compound in an extremely short time of 1.5 min. • The NR/CB nanocomposites prepared by BERE has excellent physical and mechanical properties. • The NR/CB nanocomposites prepared by BERE has high molecular weight retention. [ABSTRACT FROM AUTHOR]

Large amounts of plasticizers were added into natural starch for thermoplastic to make it processable due to the high crystallinity and large amount of intermolecular hydrogen bonds of starch. However, the traditional screw extruders based on shear deformation cannot disperse the plasticizer evenly and plasticize the starch well, which affects the comprehensive mechanical properties. In this paper, a self-developed biaxial eccentric rotor extruder (BERE) based on elongational rheology was introduced to prepare thermoplastic starch (TPS) sheets with glycerol as plasticizer at different speeds. The TPS sheets extruded by BERE all have excellent mechanical properties and optical transparency. Scanning electron microscopy, Fourier transformation infrared spectroscopy, X-ray diffraction, dynamic rheometer and universal mechanical tester were used to reveal the morphology, type and strength of hydrogen bonds, crystal structure, dynamic rheological and mechanical properties of TPS to research the effect of elongational rheology on its plasticization and properties. The results showed that the elongational rheology produced during processing process of BERE could obviously promote the dispersion of glycerol in starch and improve the melt-plasticizing effect of TPS, and the comprehensive mechanical properties of the TPS prepared by BERE is excellent with the elongation at break of 226.1%. • A self-developed extruder based on elongational rheology was used to prepare TPS. • The self-developed extruder can obviously improve the melt-plasticization of TPS. • The prepared TPS sheet has excellent optical transparency. • The prepared TPS sheet has excellent elongation at break of 226.1%. [ABSTRACT FROM AUTHOR]