The effect of particle size on the gelation of tissue conditioners

Tissue conditioner materials comprise a methacrylate polymer powder, usually poly(ethyl methacrylate) (PEM), and a plasticiser that also contains ethanol. The aim of this study was to investigate the effect of ball milling the PEM on gelation time. PEM was used as received and after ball milling for 2, 4, 8 and 16 h. Particle size was measured in each case and gelation time at 37°C when mixed with butyl phthalyl butyl glycollate (BPBG). Gelation time reduced with increasing milling time of the powder, however it was found that increase in the fines initially had a more significant affect than overall reduction in average particle size. The gelation time of unmilled and 16 h milled PEM were also measured when mixed with BPBG and various levels of ethanol. Unmilled PEM with 4% ethanol had a gelation time of 13.5±2.0 min compared to 5.5±1.0 min for the 16 h milled PEM which was similar to that for the commercial material, Viscogel™ (6.0±1.0 min). Ball milling the PEM reduces the level of ethanol required to produce a clinically acceptable gelation time.