Materials: New PBT Delivers Excellent Alkali Stress Crack Resistance

Japan’s Polyplastics Group (U.S. office in Farmington Hills, Mich.) has launched a new PBT which reportedly delivers excellent alkali stress crack resistance for a range of automotive applications. Duranex 532AR, has also been shown to exhibit outstanding hydrolysis and heat shock resistance and electrical performance for components in the chassis and engine compartment. It is said to be ideal for use in parts installed in the chassis section and lower areas of vehicles which can be splashed by water and mud, and come into contact with chemicals such as snow melting agents.

As the demand for durability, safety, and reliability in auto parts continues to increase, Duranex 532AR is said to have successfully reduced the risk of cracking in molded articles by preventing alkali (often arising from rust formation in metal parts) from penetrating the inside of the resin, thus imparting toughness that helps generate less stress. Duranex 532AR is treated with a hydrolysis-resistant formula, and boasts greater durability, high reliability and long life even in harsh environments than standard materials.

Recent test evaluations show that when specimens are immersed in alkali, cracking occurs within two hours in standard material Duranex 3300 and in hydrolysis- and heat shock-resistant Duranex 531HS. In contrast, no stress cracking occurs in Duranex 532AR even when immersed for up to 200 hours.

Electrical components and sensors installed near the engine are also often metal insert molded and there are cases when sudden temperature changes can cause heat shock fracture issues. This occurs because the metal and resin have linear expansion coefficients that differ by roughly a factor of 10. Duranex 532AR also has outstanding heat shock resistance and is capable of withstanding these harsh environments.