Grafting modification of chloroprene rubber (CR) disrupts the regularity of the CR molecular structure, making it less prone to crystallization and preventing low-temperature gelation, thus increasing the adhesive's cold resistance. Grafted adhesives have long tack retention time and low activation temperature, making them suitable for both automated mass production and manual operations, leading to rapid development in Asia. Japan, Eastern Europe, Australia, and Southeast Asian countries primarily use modified grafted CR adhesives for footwear. In my country, 95% of shoe factories use both ordinary and grafted CR adhesives, but the usage of grafted CR adhesives remains relatively small, accounting for only about 10% of all CR adhesives.
Cycloprene rubber/methyl methacrylate (MMA) binary grafted adhesive is currently the most widely used grafted modified CR adhesive. The side chains of PMMA have similar solubility parameters and surface free energy to the bonded material PVC, easily forming a compatible diffusion layer. In terms of acid-base coordination principles, PMMA, containing ester groups, is alkaline, while PVC, due to the presence of Cl atoms, is acidic, which also promotes the affinity of modified CR adhesive for PVC materials. More importantly, homopolymerized PMMA has good compatibility with plasticizers (esters) in flexible PVC, thus solving the long-standing problem of not being able to bond plasticized PVC. Research in this area is currently quite mature.
