Investigation of the specific adhesion between polyurethane foams and thermoplastics to suited material selection in lightweight structures

Abstract

Lightweight construction combines various materials to create resource efficient components. Thermoplastics (TPs) combined with polyurethane (PUR) foams are increasingly used to create hybrid composites. Optimizing the energy efficiency is one of the main issues in the development of production processes of components. Reducing the number of process steps offers great potential in this respect. PUR foam develops a strong adhesive bond with most materials. This is used for the manufacturing of hybrid composite components by filling complex cavities with PUR foam simultaneously bonded with other TP polymer components. This way, one process step for joining is saved. The interfaces in this composite structures are critical points of the failure. A huge variety of TP is used for the production of hybrid composite components and PUR foam develops varying bonding strengths with all of them. Selecting the suitable TPs for a durable bonding with PUR foam in the desired production process necessarily requires information about the respective specific adhesion. In this investigation, different TPs were processed with PUR foams in order to manufacture sandwich composites. The TP facings are produced in the injection moulding process. Subsequently, the facings are combined with the foam core during reaction injection moulding. The wetting behaviour was examined using the contact angle measurement and the mechanical strength of the interface in the sandwich composite was determined using a tensile test. A precise order of the selected TPs concerning their specific adhesion to PUR foams was achieved with these investigative methods.