2 research outputs found
Fully Biobased Shape Memory Material Based on Novel Cocontinuous Structure in Poly(Lactic Acid)/Natural Rubber TPVs Fabricated via Peroxide-Induced Dynamic Vulcanization and in Situ Interfacial Compatibilization
Shape
memory polymers (SMPs) based on fully biobased polyÂ(lactide) (PLA)/natural
rubber (NR) thermoplastic vulcanizates (TPVs) were fabricated via
peroxide-induced dynamic vulcanization. Simultaneously, in situ reactive
compatibilization was achieved by PLA molecule grafting onto NR chains.
Differing from the general concept of spherical rubber particles being
formed after dynamic vulcanization, the cross-linked NR was found
to be a ânetlikeâ continuous phase in the PLA matrix.
This novel structure explained the surprising shape memory property
of PLA/NR TPVs well (shape fixities ⌠100%, shape recoveries
> 95%, and fast recovery speed < 15 s at the switching temperature,
âŒ60 °C): the cross-linked NR continuous phase offers strong
resilience and the PLA phase serves as the heat-control switch. We
envision that the âgreenâ raw materials and excellent
shape memory properties of the dynamically vulcanized PLA/NR SMPs
will open up a wide range of potential applications in intelligent
medical devices
Bio-Based PLA/NR-PMMA/NR Ternary Thermoplastic Vulcanizates with Balanced Stiffness and Toughness: âSoftâHardâ CoreâShell Continuous Rubber Phase, In Situ Compatibilization, and Properties
Stiffness and toughness
are two mutually exclusive attributes of
polymer materials that contribute to significant improvements in impact
strength, usually accompanied by a reduction in tensile strength.
In this study, ternary thermoplastic vulcanizates (TPVs) consisting
of polyÂ(lactic acid) (PLA), polyÂ(methyl methacrylate)-grafted natural
rubber (NR-PMMA), and natural rubber (NR) with balanced stiffness
and toughness were successfully prepared via peroxide-induced dynamic
vulcanization. With 10 wt% of NR and NR-PMMA, the PLA/NR-PMMA/NR ternary
TPV displayed an enhanced yield stress of 41.7 MPa (only 38% loss
compared to neat PLA) and a significantly higher impact strength of
91.30 kJ/m<sup>2</sup> (nearly 32 times that of neat PLA). The in
situ compatibilization between PLA and rubber phases was confirmed
by Fourier transform infrared spectroscopy. Interfacial, rheological,
and calorimetric measurements confirmed that the NR was encapsulated
by NR-PMMA in the PLA phase. It was found that the flexibility of
the âsoftâ NR core and outer âhardâ NR-PMMA
shell with excellent PLA/rubber interfacial adhesion are responsible
for the super toughness and considerable tensile strength of the PLA/NR-PMMA/NR
ternary TPVs