Diisocyanate-Induced Dynamic Vulcanization and Interfacial Compatibilization toward Mechanically Robust PPC-P/PLA Blends with Enhanced Foamability

Morphology and properties of super-toughened bio-based poly(lactic acid)/poly(ethylene-co-vinyl acetate) blends by peroxide-induced dynamic vulcanization and interfacial compatibilization

Poly(lactic acid) (PLA) is well-known as a biocompatible and biodegradable polymer that can be obtained from natural sources. However, the brittleness of PLA is a significant drawback for its wide application. In this study, a poly(lactic acid) (PLA)/polyurethane elastomer prepolymer (PUEP) dynamically vulcanized system was introduced and studied in detail. The torque, FTIR spectrum, and gel content demonstrated that PUEP was vulcanized and that the isocyanate (−NCO) group in PUEP was successfully reacted with the −OH groups at both sides of the PLA. The scanning electron microscopy (SEM) revealed that a relatively uniform phase morphology and good interfacial compatibilization were achieved in the dynamically vulcanized blends. The interfacial reaction and compatibilization between the component polymers resulted in the formation of supertoughened PLA/PUEP blended materials.

Design of biodegradable PLA/PBAT blends with balanced toughness and strength via interfacial compatibilization and dynamic vulcanization

A fully biobased and supertough thermoplastic vulcanizate (TPV) consisting of polylactide (PLA) and a biobased vulcanized unsaturated aliphatic polyester elastomer (UPE) was fabricated via peroxide-induced dynamic vulcanization. Interfacial compatibilization between PLA and UPE took place during dynamic vulcanization, which was confirmed by gel measurement and NMR analysis. After vulcanization, the TPV exhibited a quasi cocontinuous morphology with vulcanized UPE compactly dispersed in PLA matrix, which was different from the pristine PLA/UPE blend, exhibiting typically phase-separated morphology with unvulcanized UPE droplets discretely dispersed in matrix. The TPV showed significantly improved tensile and impact toughness with values up to about 99.3 MJ/m(3) and 586.6 J/m, respectively, compared to those of 3.2 MJ/m(3) and 16.8 J/m for neat PLA, respectively. The toughening mechanisms under tensile and impact tests were investigated and deduced as massive shear yielding of the PLA matrix triggered by internal cavitation of VUPE. The fully biobased supertough PLA vulcanizate could serve as a promising alternative to traditional commodity plastics.

Presenting a combination of sustainability and environmental friendliness, a new class of green and non-petroleum-based thermoplastic vulcanizates (TPVs) was successfully developed from silica-filled silicone rubber (FSR) and poly(butylene succinate) (PBS) via dynamic vulcanization. The phase morphology, interfacial compatibilization, and microstructural properties of FSR/PBS TPVs were investigated. Notably, a large number of FSR microparticles were observed and were dispersed in the continuous PBS phase, indicating complete phase inversion during the dynamic vulcanization. The fine phase morphology of FSR/PBS TPVs was achieved by a fine phase morphology of the SR/PBS premix, the good interfacial compatibility between the PBS phase and the cross-linked FSR phase, and complete phase inversion. The as-prepared TPVs possessed high tensile strength, good elastic behavior, easy processability, and reprocessability. These novel non-petroleum-based TPVs have potential applications in packagings, biomedical devices, and three-dimensional (3D) printing materials.

Crosslinked bicontinuous biobased PLA/NR blends via dynamic vulcanization using different curing systems

In this work, multi-stimuli-responsive shape memory PLA/epoxidized natural rubber (ENR)/ferriferrous oxide (Fe3O4) thermoplastic vulcanizates (TPVs) with balanced stiffness–toughness were designed via dynamic vulcanization. Regulated by thermodynamic factors and kinetic factors, Fe3O4 was selectively distributed in the continuous ENR phase or at the PLA/ENR interface, which played a crucial role in reinforcing rubber and interfacial compatibilization. Therefore, excellent multi-stimuli-responsive shape memory behavior and significantly improved impact strength were achieved without decreasing its tensile strength. With 30 phr Fe3O4, impact strength reached 90.08 kJ/m2 (without fracture), which was 31 times that of neat PLA. Meanwhile, the TPVs could recover their original shape in merely several seconds along with the shape recovery ratio of 96.63% in the thermal field. Additionally, Fe3O4 also endowed the TPVs with a magnetic-/light-induced shape memory effect in an alternating magnetic field and under t...

Toughened Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/Epoxidized Natural Rubber Blends Fabricated by Dynamic Vulcanization and Interfacial Compatibilization

Shape Memory Effect in Supertough PETG/EGMA Thermoplastic Vulcanizates Obtained through Dynamic Vulcanization and Interfacial Compatibilization

Morphology structure and interfacial interaction are crucial factors for shape memory thermoplastic vulcanizates. In this study, shape memory thermoplastic vulcanizates based on poly(lactic acid) (PLA) and nitrile butadiene rubber (NBR) were prepared through dynamic vulcanization. The influence of acrylonitrile (ACN) content on the morphology, compatibility, shape memory property, and mechanical property was investigated. A co‐continuous structure was observed. The interfacial compatibilization between PLA and NBR phases occurred, resulting in a significantly improved interface adhesion and interfacial interaction, which was confirmed by Fourier transform infrared spectroscopy. With such a novel structure, the PLA/NBR TPVs owned an excellent shape memory property and further improved with increasing ACN content of NBR, which could be explained that the cross‐linked continuous NBR phase provided a stronger recovery driving force. In the meantime, tensile strength and elongation at break of TPVs increased with increase in ACN content. It is concluded that the preparation of dynamically vulcanized thermoplastic vulcanizate with co‐continuous structure and strong interfacial adhesion is beneficial to obtain outstanding shape memory effect.

The toughening of poly(lactic acid) (PLA) often involves the use of nonbiodegradable or petrochemical elastomers owing to the lack of effective renewable alternatives and facile routes to tailor desirable morphologies. In this work, we developed a facile and universal dynamic vulcanization strategy of dual monomers to fabricate mechanically robust PLA blends. By increasing NCO/COOH equivalent ratios between l-lysine diisocyanate (LDI) and hydrogenated dimer acid (HDA) (i.e., nNCO,LDI/nCOOH,HDA) above 1.0:1, the phase structure of the resulting PLA blends transformed from the common “sea-island” morphology to partially or fully co-continuous ones. The extraordinary impact toughness (the maximum impact strength up to 109.8 kJ m–2) in combination with the balanced strength and stiffness was attributed to a continuous biopolyamide elastomer (HDAPA) with the simultaneous improvement in both the cross-linking level and interfacial compatibilization. Atomic force microscopy (AFM)-based nanomechanical mapping results suggested that the cross-linking of HDAPA domains gradually prevailed from the boundaries into the whole domains with the elevated nNCO,LDI/nCOOH,HDA ratios. The mechanisms regarding multiple reactions and co-continuity development at an ultralow concentration of the minor HDAPA phase were elucidated. Intriguingly, the enhanced clustering-triggered emission was observed for the PLA/HDAPA blends with a fully co-continuous structure.

Toughening polylactide by dynamic vulcanization with castor oil and different types of diisocyanates

Magnesium acrylate induced interfacial compatibilization of EPDM/PP thermoplastic vulcanizate and shape memory behavior

In this study, a poly(lactic acid) (PLA) ternary blend system consisting of PLA, an epoxy-containing elastomer, and a zinc ionomer was introduced and studied in detail. Transmission electron microscopy revealed that the “salami”-like phase structure was formed in the ternary blends. While increase in blending temperature had little effects on the tensile properties of the resulting blends, it greatly changed the impact strength. For the blends prepared at 240 °C by extrusion blending, the resulting PLA ternary blends displayed supertoughness with moderate levels of strength and modulus. It was found that the zinc ions catalyzed the cross-linking of epoxy-containing elastomer and also promoted the reactive compatibilization at the interface of PLA and the elastomer. Both blending temperature and elastomer/ionomer ratio were found to play important roles in achieving supertoughness of the blends. The significant increase in notched impact strength was attributed to the effective interfacial compatibilizatio...

A biobased heat-triggered shape-memory polymer (HSMP) consisting of polylactide (PLA) and epoxidized natural rubber (ENR) was fabricated by peroxide-induced dynamic vulcanization. The cross-linked ENR phase exhibits a continuous net-like structure embedded in the PLA phase, which is different from a conventional plastic/rubber system having the typical “sea–island” morphology in which vulcanized rubber particles were dispersed in plastic matrix. In situ interfacial compatibilization was confirmed by FTIR analysis. The shape-recovery ratios of the PLA/ENR HSMPs were significantly improved over 90%, compared to that (60–70%) of PLA. The shape fixing and memorizing capability of PLA/ENR HSMPs was realized by the glass transition of the PLA phase: cross-linked ENR continuous phase at rubbery state offered strong recovery driving force, improved interface provided effective stress-transferring during shape recovery, and PLA continuous phase served as a “control-switch” for recovery. The biobased PLA/ENR HSMP c...