Impact modification of PP with short PET fibers: Effect of heat setting on fiber characteristics and composite properties

Polypropylene (PP) composites containing poly(ethylene terephthalate) (PET) fibers were prepared by injection molding in the temperature range of 190-260 degrees C. Increasing processing temperature led to the shrinkage of the PET fibers caused by the relaxation of orientation and recrystallization. Structural changes in the fibers resulted in the deterioration of composite properties. Decreased fiber length and modified local stress distribution restricted the plastic deformation of the matrix resulting in the very poor impact resistance of about 1 kJ/m2 at 260 degrees C processing temperature. The heat setting of PET fibers resulted in more stable crystalline structure and thus decreased shrinkage and improved composite properties even at high processing temperatures. PP composites impact modified with PET fibers are suitable structural materials for the automotive sector with a sufficiently large stiffness of around 2 GPa and an impact resistance larger than 20 kJ/m2 if processing temperature is kept as low as possible.

Automated summary

Polypropylene composites with poly(ethylene terephthalate) fibers were prepared by injection molding at temperatures ranging from 190 to 260 degrees C. Increasing the processing temperature resulted in shrinkage of the fibers due to relaxation of orientation and recrystallization. These structural changes led to deterioration of the composite properties, reducing impact resistance to about 1 kJ/m2 at 260 degrees C. Heat setting of the PET fibers improved the crystalline structure, reducing shrinkage and improving composite properties even at high processing temperatures. PP composites modified with PET fibers are suitable for automotive structural materials, providing a stiffness of around 2 GPa and an impact resistance of over 20 kJ/m2 if processed at low temperatures.