Effect of lubricants on the physical properties of poly(butylene terephthalate)

Abstract

Effect of lubricants on the rheological and thermal properties of poly(butylene terephthalate) [PBT] were investigated. Calcium stearate and adipic acid glycol polyester (AAGP) were used as processing lubricants for PBT. Decrease of melt viscosity was accomplished by the addition of 1 wt% of lubricants. It was understood that melt viscosity was affected by the enhancement of chain mobility of PBT with AAGP as an internal lubricant as well as the lubricity on processing equipment developed by calcium stearate as an external lubricant. Lubricants also influenced chain scission of PBT which caused the viscosity drop as well. In addition, lubricants resulted in the lowering of thermal stability, however, this might be minimized by adding less than 3 wt% of calcium stearate as a lubricant. As a consequence, calcium stearate as an external lubricant is more effective to control the melt viscosity of PBT with minimizing of chain scission and thermal instability in PBT.