Soap-free seeded emulsion copolymerization of MMA onto PU-A and their properties

The polyurethane acrylate (PU-A) containing double bond and COOH group was synthesized by stepwise reaction of 2,4-toluene diisocyanate (TDI), polyetherdiol (PPG), dimethylolpropionic acid (DMPA), and 2-hydroxpropyl acrylate (HPA), and the PU-A was neutralized with triethylamine (TEA) and self-emulsified in water to form the PU-A emulsion seed. Adding methyl methacrylate (MMA) into PU-A seed, the seeded emulsion copolymerization of MMA onto PU-A seed had been carried out at 80 degreesC under the soap-free condition to obtain anionic latex of P(UA-MMA). The kinetic behavior of the seeded emulsion copolymerization, the MMA grafting ratio, and the crosslinking copolymer were investigated. IR spectra showed that it did form the P(UA-MMA) copolymer. The measurements revealed that the structure of the P(UA-MMA) copolymer, its latex properties and the cast film were significantly influenced by the amounts of HPA, DMPA, and MMA. The experimental results indicated that with DMPA increased, the particle size of P(UA-MMA) latex decreased, but the tensile strength of its cast film increased. Adding a small amount of HPA, it could improve the tensile strength of the cast film. With MMA content increased, the distribution of the particle size of P(UA-MMA) latex became narrow, whereas under certain amount of MMA, the tensile strength of the cast film was enhanced. (C) 2001 John Wiley & Sons, Inc.