Development and Characterization of Thermo‐Responsive Shape Memory Composite of Polybenzoxazine and Modified Ultrafine Fully Vulcanized Natural Rubber (
UFPNR
) Filler
Achiraya Pattulee, Ibrahim Lawan, Nuttinan Boonnao, Reza Gholami, Panyawutthi Rimdusit, Sarawut Rimdusit ABSTRACT
In this study, various types and concentrations of ultrafine fully vulcanized powdered natural rubbers (UFPNR) were evaluated on how they affect the toughness of bisphenol A polybenzoxazine (PBA‐a). UFPNR types were prepared by grafting acrylonitrile (AN), styrene (ST), styrene–acrylonitrile copolymer (ST/AN), or styrene‐methyl methacrylate copolymer (ST/MMA) onto deproteinized natural rubber (DPNR). Testing PBA‐a/UFPNR weight ratios of 100/0, 95/5, 90/10, 85/15, 80/20, and 75/25 revealed that UFPNR grafted with ST/MMA (UFPNR‐g‐(PS‐co‐PMMA)) yielded the most desirable properties. Specifically, the 75/25 PBA‐a/UFPNR‐g‐(PS‐co‐PMMA) composite achieved the highest toughness improvement. At optimum content, UFPNR‐g‐(PS‐co‐PMMA) enhanced toughness by up to 86% and impact strength by 56%. Furthermore, adding 25% of these fillers improved the shape recovery ratio by about 11% (reaching 99% ± 0.8%) and shortened recovery time by 19% (reaching 1450 ± 60 s). These improvements indicate that the fillers' strain recovery and energy storage during deformation outweigh their thermal insulative effects within the matrix. Overall, the study successfully developed a robust PBA‐a/UFPNR‐g‐(PS‐co‐PMMA) composite with enhanced shape memory properties, making it highly suitable for applications requiring materials with high thermal stability.