The foaming performance evaluation of fibrillated polytetrafluoroethylene and isotactic polypropylene blends

Polypropylene (PP) foamed products have the advantages of heat and chemical resistance, but it is difficult to foam without modified PP. Traditionally, researchers have used chemical modification to increase the melt strength to improve the foaming properties of PP. In this article, we designed four kinds of screw combinations, and five regions are selected for sampling. The polytetrafluoroethylene (PTFE) and isotactic polypropylene (iPP) were blended by one-step fiber forming method, and then we tested the rheological properties and foaming properties. It is found that the rheological properties of the in situ microfiber composite are significantly improved than the iPP, and the crystallization temperature is also increased. The foaming experiment of the composite showed that the foaming performance of the composite with in situ microfiber morphology was significantly improved compared with the pure iPP performance, and the foaming temperature window of iPP was widened from 3°C to more than 6°C.

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Morphological, Rheological, and Mechanical Properties of Polyamide 6/Polypropylene Blends Compatibilized by Electron-Beam Irradiation in the Presence of a Reactive Agent

An immiscible polyamide 6 (PA6)/polypropylene (PP) blend was compatibilized by electron-beam irradiation in the presence of reactive agent. Glycidyl methacrylate (GMA) was chosen as a reactive agent for interfacial cross-copolymerization between dispersed PP and continuous PA6 phases initiated by electron-beam irradiation. The PA6/PP (80/20) mixture containing GMA was prepared using a twin-screw extruder, and then exposed to an electron-beam at various doses at room temperature to produce compatibilized PA6/PP blends. The morphological, rheological, and mechanical properties of blends produced were investigated. Morphology analysis revealed that the diameter of PP particles dispersed in PA6 matrix was decreased with increased irradiation dose and interfacial adhesion increased due to high surface area of treated PP particles. Complex viscosities (η*) and storage moduli (G’) of blends increased with increasing irradiation dose and were higher than those of PA6 and PP. The complex viscosity of the blend irradiated at 200 kGy was 64 and 8 times higher than PA6 and PP, respectively. The elongation at break of blend irradiated less than 100 kGy was about twice that of PA6. Electron beam treatment improved the compatibility at the interface between PA6 and PP matrix in the presence of GMA.

Current Issues and Challenges in Polypropylene Foaming: A Review

Thermoplastic foams have several advantages in comparison with unfoamed polymers such as lightweight, high strength to weight ratio, excellent insulation property, high thermal stability, high impact strength and toughness, as well as high fatigue life. These outstanding properties lead cellular plastics to various industrial applications in packaging, automotive parts, absorbents, and sporting equipment. Nowadays, polypropylene (PP), because of its outstanding characteristics such as low material cost, high service temperature, high melting point, high tensile modulus, low density, and excellent chemical resistance, is a major resin in the foaming industry. However, foaming of conventional PP is limited by its low melt strength leading to poor cell morphology, cell rupture/coalescence and limited density reduction. To improve PP melt strength, several strategies including particle addition as nucleating agent, introduction of long chain branching, blending with high melt strength polymers and crosslinking have been proposed. In this review, these issues are discussed and analyzed in terms of mechanical, thermal, and rheological characterizations.