GF Content Research Articles

Effect of Material Species on Flash Generation of PPS/GF Composites

Abstract Reduction of flash in injection molding is of great concern for manufacturers of electrical parts. In a previous report we have proposed a theoretical model for flash generation. The present study prepares five different poly(phenylene sulfide)/glass fiber composites using three different PPS; linear, branched and crosslinked PPS and measures the length of flash generated in the molding of the composites. Then, we have compared the flash data with a flash parameter defined in the model. This comparison has elucidated that flash length can be related with the flash parameter irrespective of PPS structure, as long as GF content is the same and the clearance of a gas vent is almost identical.

Hybrid PP–EPR–GF composites. Part II: fracture mechanisms

The fracture mechanism of hybrid iPP–EPR–GF composites has been studied by notched Charpy, three- and four-point bending fracture tests. The results of impact tests illustrate that increasing both temperature and EPR/GF ratio increases the impact energy of iPP–EPR–GF. Indeed, with increasing temperature, a brittle, ductile, transition temperature (BDTT) occurs. The results of a three-point bending test show that fracture toughness (KIC) can be improved by addition of both GF and EPR. Since the trend in the fracture toughness values is close to what would be expected by the rule of blends, it can be concluded that the use of both GF and EPR has no significant synergistic effect on toughening. The results of a four-point bending test show that craze-like damage appears in front of the pre-crack and its propagation is dictated by the GF and EPR content. Looking in more detail at the damaged zone by means of cross-polarised light microscopy, evidence of birefringence can be revealed. Briefly, the dominant mechanism of fracture in the iPP–EPR–GF system studied in this work can be related to a craze-like type damage, which includes both highly localised dilatational shear bands, due to cavitation of the EPR particles, and some crazing induced by the stress concentration associated with GF.

The influence of glass fiber on fracture behavior of isotactic polypropylene

Abstract This study is focused on the role of glass fiber on the fracture mechanism in PP/GF composites. Several composites with different amounts of glass fiber were examined. Three-point and four-point bending tests were carried out. The results of three-point bending tests show that the fracture toughness of PP increases with the increase of GF content. The results of four-point bending tests display a wide spread damage zone in front of the pre-crack while optical photographs appears that the damage zone including craze which is initiated from glass fibres. Also, the observation of the damage zone utilizing cross-polarized light illustrates that there is no evidence of shear yielding phenomenon. Looking at this in more detail via scanning electron microscopy shows that the craze propagation can be dictated by glass fiber. The crazes in PP/GF composite, studied in this work, are propagated by moving towards the interface followed by craze thickening and fiber breakage.

The effect of GF/PP matrix interfacial properties on the weldline strength in short glass fiber reinforced polypropylene

The strength of GF/PP injection molded parts is reduced by the existence of a weldline. In this paper, the effect of molecular weight of matrix PP, GF content, GF surface treatment, GF shape (diameter and chopped strand length), MAH-PP content and interfacial properties on the weldline strength in GF/PP has been studied. Since the fibers orient vertically to the flow direction, effective reinforcement cannot be obtained at the weldline. Such fiber direction at the weldline cannot be controlled by the molecular weight of matrix, GF content and GF shapes. On the other hand, strength of the weld specimens increases when the amount of silane coupling agents and the MAH-PP content increase. Therefore, it is suggested that the weldline strength is affected by the strength of interfacial adhesion between GF and matrix.