Development of Benzoxazine/DPNR Shape Memory Polymers via Solvent‐Free Melt‐Blending Method

ABSTRACT Deproteinized natural rubber (DPNR) is a sustainable biopolymer widely used to enhance the performance of polymers. While most studies employ NR to improve toughness in brittle polymer materials, this work uniquely demonstrates its positive influence on the shape‐memory performance of a commercial bisphenol A–aniline polybenzoxazine (PBA‐a) thermoset. An unconventional, green, solvent‐free latex‐blending method was developed to incorporate 0–20 wt% DPNR grafted with 2‐hydroxyethyl acrylate (DPNR‐g‐PHEA) into PBA‐a monomer before curing. Successful grafting and the improvement of interfacial compatibility were confirmed by FTIR, grafting efficiency, and TEM. The interfacial hydrogen bonding between PBA‐a and DPNR‐g‐PHEA promotes uniform dispersion at low to moderate contents, with noticeable agglomeration occurring only at 15–20 wt% of rubber contents. DMA results showed a reduced storage modulus with increasing rubber content, whereas T g increased at 10–20 wt% due to enhanced interfacial interactions. Remarkably, the PBA‐a/DPNR‐g‐PHEA blends maintained excellent shape fixity ( R f = 99%), while the shape recovery ratio significantly improved from 86% to 98%, and the recovery time decreased from 8 to 3 min with higher rubber loading. This study demonstrates a promising, environmentally friendly route for producing high‐performance shape‐memory polymer via a scalable, solvent‐free blending strategy.