Preparation and characterization of polypropylene homocomposites: Exploiting polymorphism of PP homopolymer

Abstract

In this study, the properties of polypropylene (PP) homocomposites, prepared by film-stacking followed by hot pressing, were investigated. Alpha-and beta-PP served as matrices, whereas highly oriented PP tapes of the alpha form acted as reinforcement in the homocomposites. Tapes with different draw ratios (DR ¼ 6-12) have been produced and characterized by mechanical and wide-angle X-ray scattering measurements. Tapes with a DR ¼ 8 were incorporated in a cross-ply (CP) manner in the corresponding homocomposite laminates. Specimens were subjected to static (tensile, flexural) and dynamic (instrumented falling weight impact, IFWI) tests. The thermal and thermomechanical properties of the PP tapes and homocomposites were studied by differential scanning calorimetry and dynamic mechanical thermal analysis. The homocomposite morphology was probed by polarized light microscopy, which gave evidence of transcrystalline layer at the interface between tape and matrix. The storage modulus of the CP homocomposites was improved prominently by the tape reinforcement. In static tensile tests, the homocomposites exhibited much higher stiffness and strength when compared with the neat PP specimens. However, this was accompanied with a marked reduction in the ultimate elongation. The IFWI tests showed that both alpha-and the beta-PP failed in macroscopically brittle manner, whereas the corresponding homocomposites failed in semiductile way. The homocomposite laminates prepared with beta-PP matrix exhibited higher resistance to penetration than those with alpha-PP.

Development and characterisation of injection moulded, all-polypropylene composites

“…It seems that the all-PP composites are more sensitive to the temperature. The perforation energy of all-PP composite was compared to the conventional polypropylene homopolymer material (Tipplen PP H388F, TVK Nyrt., Tiszaújváros, Hungary,); value obtained is in accordance with the literature [20]. It can be concluded that fibre reinforcement increases the perforation energy significantly compared to the matrix.…”

Injection moulded all-polypropylene composites composed of polypropylene fibre and polypropylene based thermoplastic elastomer

“…Nonetheless, all values exceed that of the conventional random PP copolymer (0.5-1 J/mm) [30]. The processing temperature had a small effect on the perforation energy of the matrix and related composite at both testing temperatures.…”

Fabrication of the self‐reinforced composites using co‐extrusion technique

“…The most important problem that hinders the use of SRP composites (from self‐reinforced polymer) is a “narrow” processing window, due to the small difference in melting temperature of the polymer matrix and reinforcement . For the preparation of SRP composites, the commonly used materials are polypropylene and polyethylene . In the case of polypropylene, the problem of “narrow” processing window is eliminated by the use of low‐melting copolymers of these polymers .…”