Abstract

Advances in engineering polymer technology have created a generation of high strength-to-weight materials for medical applications, with virtually no adverse interactions with body fluids. Polycarbonate is a widely used engineering polymer, and is often used in connection with ultra-violet light (UV) cured adhesives. Because of the chemical complexity of polymers, little is known about their actual aging characteristics. By characterizing the effects of aging, storage environment, and sterilization on medical grade polycarbonate/adhesive system properties, more accurate failure predictions can be made. In this thesis, efforts to better understand the effects of accelerated aging on a medical grade polycarbonate and UV cured adhesive system are presented. A case study in which we applied our findings to improve an existing medical device is also described. The resin investigated was DOW Calibre 2081-15 MFR. The adhesives investigated were Dymax 190-M, Loctite 3311, and Loctite 3921. By adapting ASTM test standards, tests were developed to evaluate the effects one type of accelerated aging method had on the polymers. The polycarbonate resin experienced significant changes in material properties after sterilization. The biggest change was in percent elongation which went from 130% to 40%. The Dymax 190-M had the highest shear break values initially; however, the Loctite 3311 was more consistent. The Loctite material experienced a 15% decrease in shear break value over three years accelerated aging, while the Dymax material experienced a 35% decrease. The use of post sterilization or three year accelerated aging properties for polycarbonate designs is better than using published data. This ensures more accurate evaluation for the safety factor and failure profile. It was found that the accelerated aging method used in this study is reliable for general studies through two years, but accuracy declined significantly after this time. By using our findings we were able to significantly improve the case study assembly. Understanding how material properties change over time helped us identify the major contributors to part failure to create a more robust design and final product.

Degree

MS

College and Department

Ira A. Fulton College of Engineering and Technology; Mechanical Engineering

Rights

http://lib.byu.edu/about/copyright/

Date Submitted

2004-10-26

Document Type

Thesis

Handle

http://hdl.lib.byu.edu/1877/etd571

Keywords

polymer failure, plastics, medical, designs, assembly

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