Search

Nanocomposites of polylactic acid (PLA) and poly(ethylene‐octene) grafted with glycidyl methacrylate (POE‐g‐GMA) were prepared using multi‐walled carbon nanotubes (MWCNT) as conductive nanofillers. The PLA/POE‐g‐GMA/MWCNT nanocomposites were processed through extrusion and injection molding for rheological, mechanical, electromagnetic, thermal, thermomechanical, and morphological characterization. The carbon nanotubes were dispersed in the PLA/POE‐g‐GMA chain, as seen by Raman spectroscopy. With higher MWCNT content, the complex viscosity (η*) and storage modulus (G') significantly increased in the nanocomposites, suggesting percolation formation. The nanocomposites melt flow index (MFI) results indicated lower fluidity, confirming the trend in η*. Electrical conductivity was optimal for PLA/POE‐g‐GMA/MWCNT (5 phr), reaching a value of 2.21 × 10−6 S/cm and providing electromagnetic shielding of 8 dB across the entire Ku band (12.2–18 GHz). The impact strength of the nanocomposites was higher than that of pure PLA and the PLA/POE‐g‐GMA blend, while the heat deflection temperature (HDT) remained stable at around 56°C. Increased MWCNT content in the nanocomposites promoted recovery of the elastic modulus, tensile strength, and Shore D hardness compared to PLA/POE‐g‐GMA blend. Overall, the results indicate that the PLA/POE‐g‐GMA/MWCNT (5 phr) nanocomposite has potential antistatic applications. [ABSTRACT FROM AUTHOR]

The study aimed to utilize MoO3 catalysts, produced on a pilot scale via combustion reaction, to produce biodiesel from residual oil. Optimization of the process was conducted using a 23 experimental design. Structural characterization of the catalysts was performed through X-ray diffraction, fluorescence, Raman spectroscopy, and particle size distribution analyses. At the same time, thermal properties were examined via thermogravimetry and differential thermal analysis. Catalytic performance was assessed following process optimization. α-MoO3 exhibited a monophasic structure with orthorhombic phase, whereas α/h-MoO3 showed a biphasic structure. α-MoO3 had a larger crystallite size and higher crystallinity, with thermal stability observed up to certain temperatures. X-ray fluorescence confirmed molybdenum oxide predominance in the catalysts, with traces of iron oxide. Particle size distribution analyses revealed polymodal distributions attributed to structural differences. Both catalysts demonstrated activity under all conditions tested, with ester conversions ranging from 93% to 99%. The single-phase catalyst had a long life cycle and was reusable for six biodiesel production cycles. The experimental design proved to be predictive and significant, with the type of catalyst being the most influential variable. Optimal conditions included α-MoO3 catalyst, oil/alcohol ratio of 1/15, and a reaction time of 60 min, resulting in high biodiesel conversion rates and showcasing the viability of MoO3 catalysts in residual oil biodiesel production. [ABSTRACT FROM AUTHOR]

There is a need to develop environmentally friendly materials, especially plastics, that minimize environmental pollution. In this sense, polypropylene (PP) composites were produced with 20 wt% of Macaiba almond powder (MA*) and compatibilized with SEBS-MA and EPDM-MA to carry out a biodegradation investigation of these composites. Mechanical properties (impact, tensile), heat deflection temperature (HDT), scanning electron microscopy (SEM), and Fourier transform spectroscopy (FTIR) experiments were performed. These analyses verified that the best plasticization was reached in the composites with 15% of SEBS-MA and EPDM-MA, indicating an interaction between phases. The impact strength and elongation at break of the PP/MA*/EPDM-MA and PP/MA*/SEBS-MA composites increased significantly, suggesting tough behavior. Biodegradation occurred in the soil for 120 days, and both PP/MA*/10EPDM-MA and PP/MA*/15EPDM-MA demonstrated a mass loss of about 4.68% and 4.0%, respectively. Although PP is not biodegradable, the results show that macaíba almond powder can biodegrade in the PP matrix. [ABSTRACT FROM AUTHOR]

The reactivity of different polyethylene modifiers based on acrylic acid (AA) and maleic anhydride (MA) with polyamide 6 (PA6) is investigated, using several degrees of functionalization. The polymer blends are processed in an internal mixer and injection molded. Mechanical, rheological, infrared spectroscopy, thermal, thermomechanical properties, and morphology are evaluated. The torque rheometry results show that higher functionalization degrees favored a high reactivity with PA6. As a consequence, there is an increase in the viscosity of the polymer blends, which is reflected in the reduction of the melt flow index (MFI), compared to PA6. High impact strength and elongation at break properties confirm the blends' compatibility. The elastic modulus and the tensile strength maintain high values, suggesting a balance of mechanical properties. In addition, the polymer blends' heat deflection temperature (HDT) and thermal stability properties are comparable to neat PA6. The morphology obtained by scanning electron microscopy show dispersed and refined particles in the PA6 matrix, indicating stabilization at the interface. Incorporating only 10% of high‐density polyethylene grafted with acrylic‐acid (HDPE‐g‐AA) is very efficient in optimizing the properties of PA6, contributing to broadening the range of applications for the processing industry. [ABSTRACT FROM AUTHOR]

In this work, polyhydroxybutyrate (PHB) was maleic anhydride (MA)-grafted in the molten state, using dicumyl peroxide (DCP) as a reaction initiator. Tin(II) 2-ethylhexanoate (Sn(Oct)2) and styrene monomer (St.) were used to maximize the maleic anhydride grafting degree. When PHB was modified with MA/DCP and MA/DCP/Sn(Oct)2, viscosity was reduced, suggesting chain scission in relation to pure PHB. However, when the styrene monomer was added, the viscosity increased due to multiple grafts of MA and styrene into the PHB chain. In addition, the FTIR showed the formation of a new band at 1780 cm−1 and 704 cm−1, suggesting a multiphase copolymer PHB-g-(St-co-MA). The PHB (MA/DCP) system showed a grafting degree of 0.23%; however, the value increased to 0.39% with incorporating Sn(Oct)2. The highest grafting efficiency was for the PHB (MA/DCP/St.) system with a value of 0.91%, while the PHB (MA/DCP/St./Sn(Oct)2) hybrid mixture was reduced to 0.73%. The chemical modification process of PHB with maleic anhydride increased the thermal stability by about 20 °C compared with pure PHB. The incorporation of 0.5 phr of the Sn(Oct)2 catalyst increased the efficiency of the grafting degree in the PHB. However, the St./Sn(Oct)2 hybrid mixture caused a deleterious effect on the maleic anhydride grafting degree. [ABSTRACT FROM AUTHOR]

Poly(lactic acid) has been gaining prominence in academia and industry, mainly due to being a biopolymer and biodegradable material. Nevertheless, mainly due to its high fragility, work has been carried out in order to seek alternatives to improve this drawback. Hence, this work aims to evaluate the effect of the vinyl acetate content using two types of EVA (EVA1 with 28% and EVA2 with 19%) in dynamically vulcanized PLA/EVA blends, using several dicumyl peroxide (DCP) contents, that is, 0.3, 0.5, and 0.7 phr. Blends were produced using an internal mixer, and the tensile, impact and HDT specimens were injection molded. By FTIR and torque rheometry, it was verified that, upon DCP addition, there was evidences of reticulation, resulting in crosslinked PLA, crosslinked EVA, as well as PLA‐g‐EVA. Through tensile and impact strength tests, it was observed substantial increases in the elongation at break, and in impact strength, mainly for the compounds with higher content of vinyl acetate (EVA1). Impact specimens made with PLA/EVA120 0.7 DCP, PLA/EVA130 0.5 DCP, and 0.7 DCP, did not completely break, due to the probable development of the in situ PLA‐g‐EVA compatibilizer among the present phases. Therefore, it is believed that a more homogeneous microstructure was obtained, as observed by SEM images, highlighted upon the DCP content increase. It was verified that the highest vinyl acetate content is of paramount importance for obtaining PLA/EVA blends with better compatibility as well as EVA1 being more susceptible to crosslinking using DCP, resulting in blends with greater toughness. [ABSTRACT FROM AUTHOR]

Polypropylene/Syagrus Cearensis fiber composites compatibilized with polypropylene‐graft‐maleic anhydride (PP‐g‐MA) and styrene(ethylene‐butylene)‐styrene copolymer (SEBS‐g‐MA) were successfully produced using a co‐rotating twin‐screw extruder followed by injection molding. The composites were characterized by X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The mechanical properties were determined by Izod impact and tensile testing. Thermal properties were obtained by thermogravimetric analysis (TG) and differential scanning calorimetry (DSC). Heat deflection temperature (HDT) was determined to study the thermomechanical properties of the composites. XRD and DSC indicated the presence of two polypropylene polymorphs: α and β. The unmodified PP/Fiber composites showed an incompatible behavior, presenting low fiber/matrix interaction and poor interfacial adhesion. The poor compatibility led to low elongation at break and impact strength but high tensile strength. PP‐g‐MA coupling agent promoted some adhesion to the PP/fiber interfaces but not enough to improve the impact strength. The composites with PP‐g‐MA exhibited improved tensile modulus and strength. The enhanced PP/fiber interfacial interaction promoted by SEBS‐g‐MA generated a better interplay of mechanical properties, improving impact strength and elongation at break while preserving the elastic modulus and tensile strength. In general, the fibers enhanced the thermomechanical stability of PP, as evidenced by higher HDT values. [ABSTRACT FROM AUTHOR]

Poly (lactic acid) (PLA) is one of the most currently investigated polymers due to its production from renewable sources and biodegradability. Being a brittle polymer, PLA has low toughness, limiting its use for commercial applications. Therefore, the present work aims to produce PLA blends, using the ethylene‐vinyl acetate copolymer (EVA), dynamically vulcanized with dicumyl peroxide (DCP) as a crosslinking agent. A 70/30 mixture of PLA/EVA was produced with 0.2, 0.4, 0.6, 0.8, and 1.0 phr DCP. The produced blends were characterized by torque rheometry, melt flow index (MFI), gel content, thermogravimetry (TG), and differential scanning calorimetry (DSC). Tensile properties, impact strength, heat deflection temperature (HDT), and blends morphologies (SEM) were also studied. The presence of increased dynamically vulcanized systems with added DCP was verified through torque rheometry, MFI, and gel content. Substantial increases in the impact strength and elongation at break were observed in PLA/EVA/DCP, providing super‐tough materials at 0.6, 0.8, and 1.0 phr of DCP, with impact strengths of 829.5, 860.3, and 890.2 J/m and elongation at break of 138.5, 146.8, and 120.4%, respectively. These results are promising when compared with engineering polymers and blends. This is probably due to in situ compatibilizer PLA‐g‐EVA, which resulted in a homogeneous morphology as evidenced by SEM images. [ABSTRACT FROM AUTHOR]