Thermoplastic foam injection moulding of sandwich structures with short fibre-reinforced skin layers

Abstract

Sandwich structures, consisting of a short glass fibre–reinforced polypropylene film as skin layer and chemically blown polypropylene as the core material, were produced via injection moulding. The skin layers of the sandwich structures, which contain polypropylene as well as 30 wt% and 50 wt% of glass fibres namely polypropylene–glass fibres 30 and polypropylene–glass fibres 50 respectively, were produced by film extrusion using a coat hanger die. The properties of the films were investigated by dynamic mechanical analysis. Furthermore, the influence of different glass fibre contents in the skin layers and chemical blowing agent contents in the core material of sandwich structures was studied to compare them with the compact polypropylene and the polypropylene foams. The sandwich structures were characterized with regard to density, microstructure, weight reduction, surface roughness and bending properties. In general, distinctive reinforcement effect was achieved by use of the short glass fibre with the strong influence of processing direction of the film. For the sandwich structures, it was found that a good adhesion between the skin layers and the core material can be achieved during injection moulding. The microstructure and the bending properties of the sandwich structures depend on the glass fibre–reinforced film and the chemically blown core. It was found that the use of the skin layers led to lower cell intensity in the foam core. Nevertheless, a high modulus and strength to weight ratio could be accomplished by a high stiffness of the glass fibre–reinforced film and a low density of the chemically blown core. Additionally, it was found that the surface roughness of the films could be reduced due to processing in injection moulding.

PP‐GF‐EPP sandwich structures as housing materials for rechargeable energy storage system of electric vehicles: Investigations into flame retardancy

“…For all three SWs, a low maximum temperature of the test specimen reverse side in the range T A B L E 1 0 Bench-scale fuel fire test results of PP-GF-EPP sandwich structures (SWs) equipped with additional thermocouples between the external surface layer and the EPP foam core (T 1 ) and between the EPP foam core and the TL of the reverse side (T F I G U R E 9 Right: Temperature profiles of the thermocouples between the TL exposed to fire and the EPP foam core (1), between the EPP foam core and the TL of the reverse side of the SW (2) and at the reverse side of the SW (3) measured for SW (0*-4) and SW (4*-0) in the bench-scale fuel fire test. Left: Enlargement of the temperature profiles of thermocouple (2) and thermocouple (3) of 70-90 C is observed. The flame-retarded tape layer containing SW (4*-0) shows the lowest T max,reverse side of 76.6 ± 3.8 C. This temperature is reached after 382 ± 7 s, which is about 51 s later than SW (0*-4).…”

“…For automotive applications, sandwich structures (SWs) made of thermoplastic‐fiber‐reinforced face‐sheet laminates and thermoplastic‐polymer‐based cores offer significant potential for weight saving, material performance and cost‐efficiency as well as easy recyclability. [ 3 ] Several manufacturing methods for thermoplastic SWs are reported in literature, and an overview is provided by Gruenwald et al [ 4 ] Fusion bonding processes using the thermoplastic properties to bond the face sheets to the core are of special interest as no additional adhesives are required. [ 5 ] Polypropylene (PP) with glass‐fiber (GF) reinforcement in combination with a PP foam core has been one of the most commonly used material combinations for thermoplastic SWs during the last two decades.…”

“…[5] Polypropylene (PP) with glass-fiber (GF) reinforcement in combination with a PP foam core has been one of the most commonly used material combinations for thermoplastic SWs during the last two decades. [3,6,7] Accordingly, much is known about their production and processing methods as well as mechanical performance.…”

Mechanically Robust Foamed Polypropylene/Bamboo Powder Composite Basketworks by CO2 Extrusion Foaming

“…However, there are some spaces for improvement in the above process, such as easier operation processes, shorter production cycles, and simpler equipment. In addition, the foaming process can introduce cellular structures inside the materials and has the potential to develop sandwich structures. , Typically, foam injection molding can regulate skin–cellular–skin sandwich structures for the polymer foams, but the solid structure on both sides limits its softness and the fixed mold also limits the difficulty of preparing large-size samples. In comparison, supercritical CO 2 continuous extrusion foaming with the advantages of economical and energy-saving can be used to prepare polymer foams with various morphologies, such as foam beads, foam strips, foam boards, and foam sheets .…”