Micromechanical analysis and fracture mechanics of Poly(lactic acid) (PLA)/Polycaprolactone (PCL) binary blends

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.

Section: Methodsmentioning

confidence: 90%

Section: Torque Rheometrymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Tuning the mechanical and thermomechanical properties through the combined effect of crosslinking and annealing in poly(lactic acid)/acrylonitrile‐EPDM‐styrene blends

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Acrylonitrile‐EPDM‐styrene (AES) was applied as an impact modifier for poly(lactic acid) (PLA), and the combined effect of dicumyl peroxide (DCP) crosslinking and annealing heat treatment was investigated. Torque rheometry, melt flow index (MFI), mechanical properties (impact, tensile, and Shore D hardness), X‐ray diffraction (XRD), infrared spectroscopy (FTIR), heat deflection temperature (HDT), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) were investigated. There was a considerable torque increment and fluidity drop in the PLA/AES/DCP blends caused by the crosslinking process and the formation of PLA‐g‐AES. Consequently, the impact strength and elongation at break properties improved. As an engineering terpolymer, AES was decisive in maintaining high elastic modulus, Shore D hardness, and HDT values. The PLA/AES/DCP (0.8 phr) composition leaned towards a synergism of mechanical properties, gaining 505.6% and 264.8% in impact strength and elongation at break, respectively, compared to neat PLA. FTIR and XRD analysis revealed high crystallinity, with samples presenting large crystals. The higher crystallinity had a deleterious effect on the mechanical properties of the PLA/AES/DCP blends. However, there was a marked improvement in HDT and higher toughness compared to PLA. The results before and after annealing the PLA/AES/DCP (0.8 phr) blend are promising for constructing new semi‐biodegradable materials for additive manufacturing.