Photochemistry of Bisphenol-A-Based Polycarbonate: The Effect of the Matrix and Early Detection of Photo-Fries Product Formation

Hoyle, Charles E.; Shah, Himanshu; Nelson, Gordon L.

doi:10.21236/ada236150

Cited by 1 publication

(2 citation statements)

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“…The generation of fluorescent species in PC 59,69 and PET 55,65,70 due to photodegradation reactions has been reported. Thus, fluorescence microscopy (350 nm laser light source) was used to identify the presence of photodegraded species at the surface of the helmet-grade plaque following AW.…”

Section: Discussionmentioning

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: Discussionmentioning

confidence: 99%

“…53 As a result, photodegradation disrupted the top ∼1% layer of the plaque. We posit that aromatic derivatives 55,59,65,69,70 provided the fluorescence response in the helmet-grade material, but further investigation would be required to determine the precise profile and concentration of fluorescent species created.…”

Section: Discussionmentioning

confidence: 99%