Study on Warpage of Flame-retardant PA66 Composites.

The warpage of brominated flame-retardant PA66 composites was investigated in terms of the compositions without glass fiber and with the circular and flat glass fibers. The warpage of the composites was analyzed on the basis of their mechanical properties, crystallization properties, shrinkage rate and transverse/longitudinal shrinkage ratio. The results indicated that the composites without glass fiber had the highest crystallinity, transverse shrinkage and longitudinal shrinkage, but the lowest transverse/longitudinal shrinkage ratio and warpage. At the same content of glass fibers, the warpage of the composites with the flat glass fiber was obviously better than that of the composite with the circular glass fiber due to a lower ratio of transverse/longitudinal shrinkage. In the case of mechanical properties, the tensile strength and bending strength of the composites with flat glass fibers were lower than that of the composites with the circular glass fiber. The different types of glass fibers had little effect on the crystallization of the composites, and their crystallinity and crystallization peak temperature were very close to each other. At the same content of flame retardant, both the transverse shrinkage and the longitudinal shrinkage of the composites decreased with an increase in the content of the flat glass fiber. However, their transverse/longitudinal shrinkage ratio increased, leading to an increase in the warpage of the composites. [ABSTRACT FROM AUTHOR]