Effect of Weathering on Material Properties

Wypych, George

doi:10.1016/b978-1-895198-62-1.50015-9

Cited by 3 publications

(8 citation statements)

References 47 publications

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“…A non-pigmented resin that resulted in a natural colored plaque was selected to serve as a baseline to eliminate a potential additional level of complexity, as off-the-shelf outer shells invariably contain additive pigments and colorants that can reportedly alter weathering and degradative properties. 24…”

Section: Methodsmentioning

confidence: 99%

“…3,4 Furthermore, primary polymers used in helmet-grade shell materials are commonly reported to lose critical functional properties over time. 24…”

Section: Introductionmentioning

confidence: 99%

“…Specifically, the weathering of PC and polyethylene terephthalate (PET) each consistently results in material property changes. 24 On the molecular level, degradation pathways such as photodegradation, hydrolysis, and thermal-oxidation lead to chain scission events, cross-linking reactions, and formation of small molecule by-products that disrupt molecular weight, modify morphology and molecular packing, and alter esthetic properties. 24 Microscopically, physical aging from thermal exposure causes structural morphology changes in free volume and crystallinity that macroscopically influence stress–strain behaviors.…”

Section: Introductionmentioning

confidence: 99%

“…24 On the molecular level, degradation pathways such as photodegradation, hydrolysis, and thermal-oxidation lead to chain scission events, cross-linking reactions, and formation of small molecule by-products that disrupt molecular weight, modify morphology and molecular packing, and alter esthetic properties. 24 Microscopically, physical aging from thermal exposure causes structural morphology changes in free volume and crystallinity that macroscopically influence stress–strain behaviors. 25 However, the degree and rate that environmental exposures alter material properties of helmet-grade outer shell PC blends are poorly understood.…”

Section: Introductionmentioning

confidence: 99%

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Quantifying the effects of accelerated weathering and linear drop impact exposures of an American football helmet outer shell material

Krzemiński

Fernando

Gould

et al. 2014

Proceedings of the Institution of Mechanical Engineers, Part P:

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American football helmets are subjected seasonally to a myriad of environmental conditions from expected use and storage and yet are reused without a relational understanding between service life degradation and changes in impact performance. Comprehensive investigations could link rates and degrees of material degradation to scientifically and clinically meaningful changes in helmet performance. Therefore, the purpose of this research was to preliminarily quantify the effects of accelerated weathering on (1) colorimetric, chemical, fluorescent, and thermal properties; (2) surface and bulk mechanical properties; and (3) impact performance of an American football helmet outer shell material. Helmet-grade plaques were exposed to 480 h of accelerated weathering. Surface-specific shifts (p < 0.05) in colorimetric, chemical, fluorescent, thermal, and mechanical properties were observed at the plaque surface. Plaque-derived tensile specimens underwent monotonic tensile testing, and the photodegraded ∼1% of the Weathered plaque surface thickness led to 10%, 12%, and 9% increases (p < 0.05) in Young’s modulus, yield stress, and ultimate tensile stress, respectively. Impact performance was analyzed with a protocol attempting to employ expected on-field impact conditions. Weathered and Non-weathered helmet surrogate systems managed impact energy progressively less effectively across five repetitive trials (p < 0.05); yet the absence of significant Weathered differences demonstrated that the plaque–foam systems performed similarly. Results identified a battery of diagnostic tools to characterize the degradation of outer shell material exposed to accelerated weathering. Thus, the comprehensive approach herein may be used toward the evaluation of additional service life exposures, as well as examine on-field deterioration of full helmet outer shells.

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Section: Methodsmentioning

confidence: 99%

“…3,4 Furthermore, primary polymers used in helmet-grade shell materials are commonly reported to lose critical functional properties over time. 24…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Quantifying the effects of accelerated weathering and linear drop impact exposures of an American football helmet outer shell material

Krzemiński

Fernando

Gould

et al. 2014

Proceedings of the Institution of Mechanical Engineers, Part P:

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“…The EPDM rubber is the fastest growing elastomer and the sealing profiles for many visible and invisible automotive applications such as doors, windows, hoods and trunks are made of it. Despite many good physical and mechanical properties the photo-stability of EPDM is inherently low [13]; therefore, when these materials are exposed to natural or artificial aging, color change, cracking, surface staining and reduction of mechanical properties are observed [14]. The small number of impurities found within the rubber are sufficient to initiate photo-degradation, despite weak UV absorption.…”

Section: Introductionmentioning

confidence: 99%

Effect of ultraviolet stabilizers on rubber-based automotive sealing profiles

Küçük

Gerengi

Güner

2018

Düzce Üniversitesi Bilim Ve Teknoloji Dergisi

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The sealing profiles for many visible and invisible automotive applications such as doors, windows, hoods and trunks are made of synthetic ethylene propylene diene monomer (EPDM) rubber. This combination of ethylene, propylene and unsaturated diene molecules exhibits high mechanical properties and forms a waterproof structure. With the progress of time, color change, cracking and staining can be observed on the surface of the sealing profiles used on the visible regions exposed to the sun due to the effect of high-intensity ultraviolet (UV) radiation and sunlight. The aim of this study was to investigate the effect of the UV stabilizers widely used in the plastics industry on the UV resistance of EPDM rubber. UV stabilizers protect the polymers against to UV radiation by reacting with the free radicals that are formed when a high energy UV photon causes a chemical bond in the polymer to break or by absorbing potentially destructive UV radiation. Plates of EPDM rubber were prepared by adding different types of UV stabilizers at different rates to an available EPDM formula. The effects of the UV stabilizers on the EPDM plates were measured by mechanical tests and the internationally recognized Florida outdoor aging test with climate conditions of high-intensity sunlight, high-intensity UV, and high temperature and humidity levels.

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