CMC-Assisted Peeling and PMMA Grafting of Vermiculite Nanosheets for Reinforced Flexible PVC

Balancing mechanical properties, fire resistance, and barrier properties in flexible polyvinyl chloride (fPVC) has always been a challenge. This study proposes an interface engineering strategy, which uses sodium carboxymethyl cellulose (CMC) to separate vermiculite into two-dimensional nanosheets and combines it with poly(methyl methacrylate) (PMMA) grafting. This structural design overcomes the incompatibility between PVC and vermiculite, promotes the uniform dispersion of nanomaterials and establishes a chemical-mechanical interface phase. The resulting composite material exhibits a tortuous labyrinthine structure, which restricts the movement of polymer chains and the transmission of substances. Therefore, compared with ordinary polyvinyl chloride, merely adding 3% of PMMA-grafted vermiculite nanosheets (P-VNs) increased the tensile strength by 24.53%. The formed physical barrier reduced the oxygen permeability by 35.74%, the peak heat release rate (pHRR) decreased by 21.22%, the smoke production rate (SPR) decreased by 50.00%, and the peak carbon monoxide production rate decreased by 39.29%. At the same time, it also inhibited the release of toxic smoke. In summary, these research results indicate that there is a feasible method to design flexible polyvinyl chloride materials that possess both mechanical properties and barrier properties as well as fire resistance.