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A design may be improvable without presenting an unacceptable risk related to safety or performance. However, design-related failures can result from an oversight in performing one of the major design activities or from a failure to balance the competing demands inherent to part design. This article focuses on design-related failures in products utilizing polymeric materials, and reviews important considerations of the design envelope of plastic parts. The article provides a non-exhaustive list and descriptions of design tools that can support the design process and the prevention of design-related failures. It also discusses the most common causes of design-related failures of plastic parts. The article can assist in both failure analysis and in the prevention of failures in which design may be a contributing factor or a root cause.

The ability to predict the service life of materials is central to effective risk assessment for many products. Like the tools and methodologies for the broader evaluation of risk, service life prediction (SLP) is a methodology that is both well established and continuously improving, challenging researchers to increase the insight and accuracy of prediction within acceptable ranges of speed and cost. As our collective understanding of accelerated aging, failure modes, and predictive models improves, so does our ability to elucidate the relationship between environmental variables and a given material’s response. However, formidable challenges—both technical and practical—remain. Understanding failure modes and underlying mechanisms is essential to accurately predicting service life via accelerated testing. Importantly, the real world can be much more complex than accelerating exposure to a single factor. Thus, useful testing in support of lifetime analysis requires that the operative mechanism that governs a given material’s service life is activated in the accelerated test. One of the enduring challenges of successfully implementing SLP into the product development lifecycle is the difficulty of predicting the results of often complex real-world usage. This work provides a roadmap to the SLP process followed by two case studies that highlight the practical intersection of SLP and risk assessment in industry. One study establishes how SLP has been used effectively to describe lithium ion battery performance in an electronic device to facilitate operational choices to extend lifetime. A second study demonstrates the unintended service life reduction due to formulation change in a building sealant.

Key relationships between molecular structure and final properties are reported for standard flow and high flow grades of commercially-available polyetheretherketone (PEEK) resins that differ primarily in molecular weight and molecular weight distribution. Despite similar chemistry and composition, the molecular size-dependent structural differences associated with the PEEK resins in this study are shown to influence the crystallization rate, final crystallinity, and melt rheology during processing, which subsequently affects mechanical properties, including strength, ductility, and impact resistance. These structure-property relationships provide fundamental understanding to aid in the design and manufacturing of industrial and medical devices that leverage both the advantages common to all PEEK resins, including chemical and thermal resistance, mechanical strength, and biocompatibility, as well as more subtle differences in crystallization kinetics, melt rheology, ductility, and impact resistance. POLYM. ENG. SCI., 2016. © 2016 Society of Plastics Engineers

The objectives of this study were three-fold: (1) to determine the applicability of the small punch test to characterize Bionate 80A polycarbonate urethane (PCU) acetabular implants; (2) to evaluate the susceptibility of PCU acetabular implants to exhibit degradation of mechanical behavior following gamma irradiation in air and accelerated aging; and (3) to compare the oxidation of gamma-air sterilized PCU following accelerated aging and 5 years of natural shelf aging. In addition to attenuated total reflectance-Fourier transform infrared spectroscopy, we also adapted a miniature specimen mechanical test, the small punch test, for the deformable PCU cups. Accelerated aging was performed using ASTM F2003, a standard test that represents a severe oxidative challenge. The results of this study suggest that the small punch test is sufficiently sensitive and reproducible to discriminate slight differences in the large-deformation mechanical behavior of Bionate 80A following accelerated aging. The gamma-air sterilized PCU had a reduction of 9% in ultimate load after aging. Five years of shelf aging had little effect on the mechanical properties of the PCU. Overall, our findings suggest that the Bionate 80A material has greater oxidative stability than ultra-high molecular weight polyethylene following gamma irradiation in air and exposure to a severe oxidative challenge.

Tumors related to the implantation of surgical grade polypropylene in humans have never been reported. In this commentary we present a balanced review of the information on what is known regarding the host response to polypropylene and provide data as to why the potential for carcinogenicity of polypropylene mesh is exceedingly small.

Polymers are being used in every day consumer products manufacturing and various engineering applications. They provide design and manufacturing flexibility, as well as desirable combinations of properties. However, successful implementation of any polymer requires a basic understanding of its mechanical behavior and what factors affect that behavior. The chapter overviews the basic principles of polymer mechanical behavior which includes a discussion of the microstructure and morphology of polymers, stress-strain behavior, time–temperature relationships, deformation mechanisms, fracture mechanics, polymer toughening, and reinforced polymers (and composites). The behavior of polymers in load-bearing applications is also described, with introductions to creep, fatigue, and high-strain rate performance. Keywords: crazing; polymethyl methacrylate; polystyrene; semicrystalline materials; viscoelasticity