Improving the impact strength of polypropylene/carbon fiber composites via β‐modification and annealing treatment

Abstract

The low impact strength of short carbon fiber (CF) reinforced polypropylene (PP) composites (PP/CF) restricts their practical application. Many studies focus on improving interfacial adhesion strength between PP and CF, while the essential properties of PP matrix are also significant, but rarely investigated for toughening PP/CF composites. In this work, the combination of β‐modification and annealing treatment were adopted to modify the intrinsic toughness of PP matrix, thereby enhancing the impact strength of PP/CF composites, meanwhile their flexural strength and modulus were almost maintained. From the XRD, DSC, POM, DMA and SAXS results, we observed that abundant β‐crystals with small size were produced in PP matrix after β‐modification. In addition, increased overall crystallinity, perfected crystals structure and looser amorphous region were generated after annealing treatment. These microstructure changes resulting from β‐modification and annealing treatment, together triggered the plastic deformation of PP matrix, which was the main reason for toughening PP/CF composites.

Toughness enhancement of PP/EVA/LDH composites by controlling β nucleating agent and annealing treatment

“…The inherent toughness of PP/carbon fiber (CF) composites was improved by means of annealing treatment. 23 In the experiments, thanks to the synergistic effect of β-nucleating agents, the annealed specimens achieve an impact strength of 34.4 kJ/m 2 , which substantially improves the toughness of PP composites. Moreover, for the toughening mechanism of heat treatment, it has been reported in the literature that annealing facilitates local plastic deformation of PP, where the impact section is strain-induced to stress-induced resulting in a brittle-ductile transformation.…”

“…Heat treatment temperature and time is very important due to the extreme sensitivity of PP to temperature especially in low temperatures. The inherent toughness of PP/carbon fiber (CF) composites was improved by means of annealing treatment 23 . In the experiments, thanks to the synergistic effect of β‐nucleating agents, the annealed specimens achieve an impact strength of 34.4 kJ/m 2 , which substantially improves the toughness of PP composites.…”

β-Nucleation of isotactic polypropylene: Chain structure effects on the effectiveness of two different nucleating agents

“…At Budapest, Horváth et al [48] did an extensive molecular weight series with Ca-suberate discovered several years before in the same group [49], while Varga et al [50] tested a trisamide of trimesic acid, obviously soluble in melt state like most of the trisamides evaluated as clarifiers for α-nucleation [7]. Chinese groups have studied the liquid-crystalline polyester PBDPS [51], zinc adipate [52], alkaline salts of 7-oxabicyclo [2,2,1] hept-5-ene-2,3-dicarboxylic acid [53], chromium salt of bicyclo [2,2,1]-5-heptene-2,3-dicarcoxylic acid [54] and most recently polydopamine (PDAP) [55]. In most of the mentioned more recent papers, only one type of iPP has been used for the studies, mostly an iPP homopolymer based on a Ziegler-Natta (ZN) type catalyst.…”