The injection moulding process of thermoplastics is a primary moulding process with which plastic parts can be manufactured in a fully automated and cost-effective manner with accurate shapes. Produced parts must then be integrated into the assembly, whereby bonding is a possible joining method. One problem is the low adhesive strength of the material. Pretreatment of the bonding surface can help here, but the resistance to ageing is not always given. Reasons for this can also result from the manufacturing process of the components. In addition, adhesives contain a large number of short-chain organic chemicals which, in combination with component-immanent internal stresses, can damage the substrate surface and thus promote failure of the bonded joint.
The aim of the project is to demonstrate the optimization potential of the parameters used in the injection molding process. Special attention is paid to the environmental stress cracking resistance (ESCR). In the project, the stress cracking tendency of differently produced plastic samples is compared and the differences obtained are shown. For this purpose, easy to perform tests are developed based on existing test standards. Furthermore, the dependence of the cooling rate in the manufacturing process could be shown by means of tensile shear tests.
The transfer of the knowledge gained in the project to real components enables an improvement in the strength of bonded thermoplastic components, which increases the fields of application of the thermoplastics that can be produced at low cost. Damage to the surfaces of the joined parts due to adhesive-induced medial stress corrosion cracking becomes comparable by the developed test methods.
