Process Influences on the Materials Interface of an Injection Molded Hard‐Soft‐Component

Abstract

Combining a soft thermoplastic elastomer with a hard polymeric material by multi‐component injection molding provides a novel and sophisticated alternative for mounting a vulcanized dynamic elastomeric seal part into a rigid housing. Such assembly injection molding is new and challenging, but promises several economic advantages. The main issue within such a development is the assurance of sufficient bond strength between soft and hard component, in order to withstand the service load conditions safely. This paper studies certain process influences on the interface condition between the materials. The strength of the adhesive bond of composite test specimens consisting of a hard outer ring and a soft inner ring with integrated rotary seal lip are evaluated. The injection molded and investigated composite parts consist of glass fiber reinforced polybutylene terephthalate (PBT‐GF30) as hard component and a thermoplastic polyurethane (TPU) as soft component. The required force to reach delamination between hard and soft component is monitored and correlated with the surface structure and properties of differently plasma pre‐treated hard components. Supposed a material combination and the contact temperature are defined the surface conditions of the hard component play the major role with respect to the adhesion bond strength.

Recent developments on the overmolding process for the fabrication of thermoset and thermoplastic composites by the integration of nano/micron-scale reinforcements

“…In one of the studies, Frick et al [15] investigated adhesion bond strength by combining 30 wt% glass fiber reinforced polybutylene terephthalate (PBT) as a hard component and thermoplastic polyurethane (TPU) as a soft component and tailored the surface roughness of hard part by applying atmospheric plasma treatment and changing the processing temperature of TPU. In another work, Dondero et al [16] controlled the adhesion between an insert and overmolded materials by using two different random copolymers having different octene content having a direct effect on the interface temperature.…”

“…The insert overmolding process includes the placement of the fiber-reinforced composites or pre-molded structures as an insert in the mold prior to the injection of the second material [25]. In some variants of this process, the insert is preheated below the melting temperature, and then the second polymeric material (overmolded material) is injected subsequently on this insert [15,26]. The insert molding can also be achieved by injecting the polymer directly onto the substrate without applying any preheat treatment.…”

Study on the processes and warpage of double‐injection‐molded parts containing PP recycled materials

“…1,2 Examples of applications include automotive interiors, medical equipment, telephone keypads, toothbrushes, shaving hardware, household appliances, and hand tools. [3][4][5] However, double-injection molded parts often suffer from defects such as warpage, 6 nonadhesion between the surface and inner layers, 7 and cracks. 8 Among these, warpage is one of the main problems of double-injection molding, which has a significant impact on the dimensional accuracy, performance, and appearance of double-injection-molded parts.…”

“…Double‐injection molding has gained considerable attention owing to its capacity to facilitate the recycling of plastic waste and meet the diverse functionality and aesthetic requirements for plastic products 1,2 . Examples of applications include automotive interiors, medical equipment, telephone keypads, toothbrushes, shaving hardware, household appliances, and hand tools 3–5 . However, double‐injection molded parts often suffer from defects such as warpage, 6 non‐adhesion between the surface and inner layers, 7 and cracks 8 .…”