Heat resistant molded or extruded thermoplastic articles

Abstract

Disclosed is a molded or extruded thermoplastic article having high heat stability over at least 500 hours at least 170° C. including a thermoplastic composition including a thermoplastic resin; one or more polyhydric alcohols having more than two hydroxyl groups and a having a number average molecular weight (Mn) of less than 2000; one or more reinforcement agents; and optionally, a polymeric toughener; wherein 4 mm test bars prepared from said thermoplastic composition, and exposed at a test temperature at 170° C. for a test period of 500 hours, have, on average, a retention of tensile strength of at least 50 percent, as compared with that of an unexposed control of identical composition and shape. Further disclosed is a molded or extruded thermoplastic article, including a thermoplastic polyamide composition, wherein 4 mm test bars of said thermoplastic polyamide composition, when exposed at 210° C. for a test period of 500 hours, have a retention of tensile strength of at least 70 percent.

Description

CROSS REFERENCE TO RELATED APPLICATION[0001]This application claims the benefit of priority of U.S. Provisional Application No. 61 / 137,345, filed on 30 Jul. 2008 and currently pending.FIELD OF THE INVENTION[0002]The present invention relates to the field of molded and extruded thermoplastic articles having improved long-term high temperature aging characteristics.BACKGROUND OF THE INVENTION[0003]High temperature resins based on polyamides and polyesters possess desirable chemical resistance, processability and heat resistance. This makes them particularly well suited for demanding high performance automotive and electrical / electronics applications. There is a current and general desire in the automotive field to have high temperature resistant structures since temperatures higher than 150° C., even higher than 200° C., are often reached in underhood areas of automobiles. When plastic parts are exposed to such high temperatures for a prolonged period, such as in automotive under-the-...

AI Technical Summary

Benefits of technology

[0100]A significant advantage of the molded or extruded thermoplastic articles of the invention is that high thermal stability is provided without the use of conventional copper heat stabilizers. Copper heat stabilizers tend to act as corrosive agents over long periods of time at elevated temperatures; and in some environments actually cause degradation of semiaromatic polymers. Thus, another embodiment is molded or extruded thermoplastic article wherein said thermoplastic resin is a polyamide and said thermoplastic composition comprises less than 25 ppm copper as determined with atomic absorption spectroscopy.

Problems solved by technology

When plastic parts are exposed to such high temperatures for a prolonged period, such as in automotive under-the-hood applications or in electrical / electronics applications, the mechanical properties generally tend to decrease due to the thermo-oxidation of the polymer.

Existing technologies lead not only to a poor improvement of long-term heat aging resistance, but also the improved heat aging characteristics are insufficient for more demanding applications involving exposure to higher temperatures such as for example in automotive under-the-hood applications and in electrical / electronics applications.

Disclosed compositions exhibit improved mechanical properties such as tensile strength and elongation at break upon long-term heat aging at 215° C. However, such metal powders are not only expensive but they are also highly unstable because they are prone to spontaneous combustion.

Unfortunately, with the existing technologies, molded articles based on polyamide or polyester compositions either suffer from an unacceptable deterioration of their mechanical properties upon long-term high temperature exposure or they are very expensive due to the use of high-cost heat stabilizers.