High flow polypropylene composites reinforced by glass filaments: Manufacturing process and property evaluations

Abstract

High flow (hf)-modified polypropylene (PP) fibers and glass filaments (GFs) were made into webs, which were then laminated orthogonally and needle punched to make GF/PP-hf preforms. These preforms were then hot pressed to produce GF/PP-hf composites. Similarly, GFs and nonmodified PP were made into GF/PP composites with the aforementioned process to serve as the control group. The structure, morphology, and mechanical performances (i.e. tensile, bending, and impact strength) of GF/PP and GF/PP-hf composites were characterized and tested using differential scanning calorimeter and dynamic mechanical analysis. The test results showed that the GF/PP-hf composites are composed of reinforcing filaments at a weight ratio of 43.40% and an average length of 22.9 mm. Consequently, they had advantages of high fiber content, long fiber length, and adjustable fiber orientation. Compared to GF/PP composites, GF/PP-hf composites exhibited good dispersion of GFs in the matrices, good bonding between filaments and the matrix, and a relatively lower porosity factor of 2.92%. Moreover, the glass transition temperature and crystallinity were improved by 15.2°C and 10.42%, respectively. When the temperature was lower than 160°C, GF/PP-hf composites preserved a higher energy storage modulus and a lower loss factor. Furthermore, GF/PP-hf composites exhibited good static mechanical properties, including the tensile strength of 118 MPa, the tensile modulus of 5830 MPa, the bending strength of 180 MPa, the bending modulus of 780 MPa, and the impact strength of 33 KJ m−2, which are 30, 29.6, 78.2, 68.3, and 32%, respectively, higher than those of the control group.