Recycling EVA Waste: An Opportunity For The Footwear Industry - Rheological Properties of EVA Waste Composites Using Torque Rheometry

Ethylene vinyl acetate blends (EVA-B) (at 19 and 28wt% vinyl acetate) were supplied by the footwear industry, along with an industrial (reference) compound labeled EVA-ref. EVA waste is an industrial sub-product crosslinked (injection sprues and unused midsoles), that was particulate through a micronization process and labeled as EVA-w. The objective of the present work was to evaluate processability and rheological parameters (using torque rheometry) when adding EVA-w to EVA-B. The EVA-w particle size distribution was bimodal, with an average diameter of 53.06 μm, and volume (%) D (10), D (50), and D (90) respectively equal to 12.47, 31.83, and 135.18 μm. However, this ample size distribution did not affect the composite mixing. FTIR-ATR analysis showed that no new crosslinking occurred after processing the composites. Low unit mixing energy (Wu), and mechanical work (as represented by DT values: torque stabilization temperature (Tstab) - test temperature (Ttest)) were required to mix the composites. Consequently, the dispersion of the EVA-w particles within the molten EVA-B occurred during the first 3 min of mixing, making it easier. The sensibility to shear-thinning behavior was more pronounced when adding EVA-w, especially at 25 phr. The m parameter was smaller in the composites as compared to the EVA-ref, and when adding EVA-w at 35 phr, it showed a tendency to increase. The average shear stress (E) of the 15 phr composite was similar to that of the EVA-ref compound. Yet for 25 phr, a higher value was observed. The adding of EVA-w made the non-Newtonian behavior of EVA-B less pronounced. For all samples, the average viscosity (t) decreased with average shear rate (h), revealing a pseudoplastic behavior.

From Waste to Reuse: Manufacture of Ecological Composites Based on Biopolyethylene/Wood Powder with PE-g-MA and Macaíba oil

This work aimed to investigate the biopolyethylene (BioPE)/wood powder (WP) composites compatibilized with polyethylene-grafted maleic anhydride (PE-g-MA), using macaíba oil (OM) as a processing aid. The composites were prepared, initially, in an internal mixer and, later, the crushed flakes were molded by injection. Mechanical properties (impact, tensile, flexural and Shore D hardness), heat deflection temperature (HDT), Vicat softening temperature, differential scanning calorimetry (DSC), thermogravimetry (TG), water absorption, torque rheometry and scanning electron microscopy (SEM) were evaluated. The addition of 30% wood powder to the BioPE matrix increased the elastic modulus (tensile and flexural), Shore D hardness and heat deflection temperature (HDT), compared to neat BioPE. These properties were improved when 10% of the PE-g-MA compatibilizer was added, compared to neat BioPE and the non-compatibilized composite. There was a significant reduction in the torque of the composites with the addition of macaíba oil, indicating that it improved the processability. In addition, the incorporation of macaíba oil into the composites helped to reduce water absorption, as well as to increase impact strength. SEM micrographs illustrated a greater degree of interfacial adhesion when PE-g-MA and macaiba oil were added.

From Disposal to Technological Potential: Reuse of Polypropylene Waste from Industrial Containers as a Polystyrene Impact Modifier

The practice of recycling over the years has been increasingly encouraged, with the aim being the manufacturing of materials that contribute to sustainable development. In light of this, the present work evaluated the potential of mixtures of polystyrene (PS)/recycled copolymer polypropylene (PPr), using styrene-(ethylene/butylene)-styrene (SEBS) as a compatibilizing agent. Initially, the mixtures were prepared in a co-rotational twin-screw extruder, and, afterwards, the extruded granules were molded by injection. The properties of torque rheometry, impact strength, tensile properties, differential scanning calorimetry (DSC), heat deflection temperature (HDT), and scanning electron microscopy (SEM) were evaluated. The formulation PS/PPr/SEBS (70/20/10 %wt.) demonstrated an increase in viscosity, corroborating with an increase of 123% and 227% in the elongation at break and impact strength, respectively, compared to neat PS. Though the elastic modulus and tensile strength suffered losses, the reduction was not drastic. Furthermore, the addition of a semi-crystalline recycled material in the amorphous matrix (PS) contributed to an increase in thermomechanical strength, as seen in the HDT. The morphology revealed that SEBS is effective in making PS/PPr mixtures compatible because the dispersed phase is well adhered to the PS matrix and promotes greater morphological stability. Thus, it is possible to add value to discarded material and reduce the costs of the final product, which can reduce pollution.

Efecto de la adición de copolímeros reactivos a mezclas de PLA/ATP

In this work, the reactive compatibilization of Polylactic Acid/Thermoplastic Starch (PLA/TPS, 80/20% w/w) blends using acrylic copolymers of methyl methacrylate-glycidyl methacrylate (MMA-GMA) was examined. The compatibilization was studied using torque rheometry, thermal analysis (DSC), Scanning Electron Microscopy (SEM) and mechanical properties. During melt mixing, the torque of PLA/TPS blends decreased, this was related to the breakup of starch chains. The addition of MMA-GMA copolymer increased the torque during the mixing period. This torque increasing is evidence of a viscosity increase and it was related to the reactions between the epoxy group present in the acrylic copolymer, the end-groups of the PLA and TPS hydroxyl groups. The morphologies of the compatibilized blends showed a decrease in the particle size of the TPS domains and an increase in elongation of 30%. The reactive compatibilization is an interesting technique to expand the property range of PLA materials, which can potentially substitute oil-based materials.

Rheological, Thermal, and Degradation Properties of PLA/PPG Blends

The work presented herein focuses on simulating the compounding process via a torque rheometer, as well as the relationship between the melt viscosity and the polymer molecular weight (MW). We aim to predict the plasticization of polylactic acid (PLA) using polypropylene glycol (PPG) with different MWs. The rheological properties of the PLA/PPG composites containing PPG with different MWs were systematically studied by capillary rheometry and torque rheometry. The initial degradation of PLA/PPG composites during melt processing was monitored in real time. The results indicate that PPG can significantly reduce the melt viscosity of PLA/PPG composites, leading to obvious pseudoplastic fluid behavior. The lower the MW of PPG, the lower the viscosity of the PLA/PPG composite. The addition of PPG was favorable for the degradation of PLA during processing, and the degradation degree of the composite materials increased as the MW of PPG was decreased.

Effect of acrylonitrile–butadiene–styrene terpolymer on the foaming behavior of polypropylene

To improve the cellular foam structure of common polypropylene (PP), acrylonitrile–butadiene–styrene terpolymer (ABS) and compatibilizer were used to blend with PP, and the foaming behavior of PP/ABS blends was investigated. The solid and foamed samples of the PP/ABS blend with different component were first fabricated by melt extrusion followed by conventional injection molding with or without a blowing agent. The mechanical properties, thermal features, and rheological characterizations of these samples were studied using the tensile test, dynamic mechanical analyzer, differential scanning calorimetry, scanning electron microscopy, X-ray diffraction, and torque rheometry. The results suggest that ABS is a suitable candidate to improve the foamability of PP. The effect of ABS and compatibilizer on the foamability of PP can be attributed to three possible mechanisms, that is, the weak interaction between phases that facilitates cell nucleation, the improved gas-melt viscosity that prevents the escape of gas, and the influence of crystallization behavior that helps to form a fine foaming structure.

Crystallization kinetics of poly (butylene adipate terephthalate) in biocomposite with coconut fiber

ABSTRACT The melt crystallization characteristics of a compound of coconut lignocellulosic fibers dispersed in poly(butylene adipate terephthalate) (PBAT), a fully biodegradable copolyester matrix, was studied by differential scanning calorimetry (DSC). PBAT/coconut fiber compounds with 10% and 20% filler content were prepared in a laboratory internal mixer; torque rheometry showed negligible degradation during processing. Nonisothermal melt crystallization of the matrix was thoroughly studied by DSC in 10% compounds at cooling rates between 2 and 32°C/min, and quantitative information was provided on crystallization temperatures and rates, as well as the crystallinity developed, which turned out to be higher than expected at the high cooling rates. Crystallization kinetic results were correlated using classical macrokinetic Pseudo-Avrami, Ozawa, and Mo models, in order to obtain quantitative analytical expressions appropriate for processing applications. Pseudo-Avrami and Mo models were found to represent well the experimental data. A detailed analysis of the model fitting is presented, in order to assess the expected uncertainties. Despite its failings at the onset and end of the crystallization process, Mo model is recommended as best overall empirical correlation of the experimental data for the intended purpose.

Optimizing torque rheometry parameters for assessing the rheological characteristics and extrusion processability of wood plastic composites

The rheological behavior of wood plastic composites’ (WPCs’) melts is closely associated with extrusion processability, especially in highly filled systems. This study investigated the extrusion processibility and the effects of test conditions and typical WPC additives on the torque rheological behavior of wood flour/high-density polyethylene (WF/HDPE) mixing melts compounded using a twin-screw extruder. Both equilibrium melt temperature ( Te) and equilibrium torque ( Ma) at steady state increased with WF content. Addition of 2% lubricant TPW604 based on the total weight of WF and HDPE matrix resulted in a decrease in measured Te and Ma, showing a reduction in shear heating in mixing chamber. Adding 4% maleic anhydride grafted polyethylene (MAPE) as compatibilizer resulted in an increase in measured Te and Ma. In this study, adding lubricant TPW604 and/or compatibilizer MAPE can improve the extrusion processability of highly filled WF/HDPE melts. For a WPC system with preset compositions, its Ma value can be used to evaluate its extrusion processability. The results provide both knowledge about the compounding procedure and practical methods for evaluating the effectiveness of WPC additives, the flow performance, and extrusion processability of highly filled WPC melts.