Commingled poly(butylene terephthalate)/unidirectional glass fiber composites: Influence of the process conditions on the microstructure of poly(butylene terephthalate)

The microstructure of poly(butylene terephthalate) (PBT) has been investiga ted at the different stages of the manufacture of a new generation of compo site materials, i.e., commingled Twintex(R) PBT/glass fiber composites. Fro m differential scanning calorimetry and wide angle X-ray scattering analysi s in addition to density measurements and optical microscopy observations, it was concluded that the different stages of the composite manufacture ind uce some changes in the crystalline forms of PET. In particular, the drawin g of PET can promote the formation of the beta phase. The analysis of the c rystallization kinetics points out the nucleation role played by the fibers . It is concluded that the growth of a transcrystalline region in the vicin ity of fibers is promoted by the elevated pressure and temperature used in the manufacturing process of the composites.