POM Mechanical Properties

Abstract

Thanks to its high degree of crystallinity, polyoxymethylene (POM) homopolymer exhibits high mechanical properties of strength, stiff ness and creep. In the case of POM copolymer, the strength and stiff ness are slightly lower because of its lower degree of crystallinity. Furthermore, the use domain ranges from -30°C to 150°C which allows various applications. More specifi cally to the POM, friction properties are excellent due to oxygen contained in the POM monomer. Th e major drawback of POM homopolymer is its brittleness at RT compare to polyolefi ns, typically nominal strain at break values are close to 20%. To improve mechanical properties at failure, diff erent strategies can be adopted as POM copolymer have lower crystallinity degree (strain at break close 70%) or added polyurethane in POM matrix (100ST from DuPont for instance). However, we will see that these strategies lead to a decrease in the material’s stiff ness. Lastly, another possible way is the use of specific processing conditions to induce oriented morphology. We will review all these aspects. This chapter is divided in two major parts: the first part is devoted to shortterm mechanical properties as elastic properties as a function of temperature and morphology aspects, failure properties and the diff erent strategies to improve them. The second part aims to present long-term properties such as creep behavior and modifi cations induced by aging, leading to an embrittlement of the POM limiting its lifetime.