Method of manufacturing a composite part comprising a core and at least one skin region

Abstract

A method of manufacturing a composite part comprising, a core (16) and at least one skin region (20, 22) formed of a skin polymer attached thereto, the skin polymer being a low-friction thermoplastic polymer, by: a) providing a mold with a heatable mold cavity; b) loading into the mold cavity a core element having a surface with at least one contacting region provided with a plurality of anchoring sites (10), and—previously or subsequently—loading into the mold cavity a layer of the skin polymer in powder form adjacent said contacting region and embedding the anchoring sites; c) applying a heat pressing step melting the skin polymer powder to form a molten skin polymer matrix (20, 22, 32); d) applying a cooling step, solidifying the skin polymer matrix forming a skin region mechanically engaged into anchoring sites of the core element forming the core.

Description

FIELD OF THE INVENTION[0001]The present invention relates to a novel method of manufacturing a composite part comprising a core and at least one skin region formed of a skin thermoplastic polymer attached thereto. Moreover, the invention relates to a composite part comprising a core element and at least one skin region formed of a skin thermoplastic polymer attached thereto.BACKGROUND OF THE INVENTION[0002]Conventional polyethylene polymers, i.e. low and high density polyethylene, are waxy solids not known for exceptional strength properties. Due to their relative softness, while generally lubricious, they are easily abraded. Ultra high molecular weight polyethylene, also known as “UHMWPE”, on the other hand, is an exceptionally strong and durable polymer totally unlike its poorer relatives.[0003]UHMWPE is prepared by special polymerization processes in which the polyethylene chains acquire an exceptionally high molecular weight, typically having number average molecular weights of ...

AI Technical Summary

Benefits of technology

The patent describes a method of making composite parts using a low surface energy thermoplastic polymer and a fiber reinforced core. The skin polymer powder is applied to the core and melts during the heat pressing step to improve mechanical coupling between the skin and the core. This process results in lightweight composite parts with excellent surface properties. The use of a fiber reinforced core with high molecular weight polymers having low flowability is important for achieving high mechanical performance. The term "skin" refers to a surface layer attached to an inner or core structure, and may be applied to one face of the core element in a one-sided configuration. A horizontally closing mold is advantageous for such a configuration.

Problems solved by technology

Due to their relative softness, while generally lubricious, they are easily abraded.

However, this same feature is also the cause of major processing problems.

While ordinary polyethylene even including polyethylene of very high molecular weight can be melt extruded, attempts to melt extrude UHMWPE have been largely unsuccessful, despite much research in this area.

The problems associated with processing of UHMWPE are due in part to the gel-like nature of the polymer above its crystalline melt temperature, roughly 135° C. to 150° C. While ordinary polyethylene is a viscous, molasses-consistency liquid at such temperatures, UHMWPE is a swollen gel which has an extremely high viscosity, and which exerts exceptional frictional stress against the walls of extruders and the like.

As can be seen, compression molding is a cost-intensive and labor intensive method of producing UHMWPE products.

It should be noted that UHMWPE cannot be reinforced simply by incorporating reinforcement fibers, since adhesion of UHMWPE to reinforcement fibers is very poor.

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