Mechanical Ageing Protocol Selection Affects Macroscopic Performance and Molecular Level Properties of Ethylene Vinyl Acetate (EVA) Running Shoe Midsole Foam

Lippa, Nadine M.; Hall, Elise; Piland, Scott G.; Gould, Trent; Rawlins, James W.

doi:10.1016/j.proeng.2014.06.082

Cited by 11 publications

(20 citation statements)

References 19 publications

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“…The MA input parameters were not estimates or representative impulses, [15][16][17][18][19][20][21][22] but were actual unique impulses measured for each participant during the first running session (Figure 3). Because each of the unaged shoe conditions demonstrated different kinematics and kinetics, [4][5][6][7] the MA input parameters also varied as a function of both shoe type and shoe region (Tables 1 and 2).…”

Section: Ma Input Parametersmentioning

confidence: 99%

“…It may be anticipated that important interactions among shoe type, midsole degradation, and runner biomechanics may occur. [4][5][6][7] Shoe degradation is known to occur [15][16][17][18][19][20][21][22] and has been associated with an increased risk for running injury, 23 yet changes in traditional and minimalist shoe material properties with aging and its consequences on human running biomechanics have not been reported. One study reported that aged shoes affected running kinematics (i.e.…”

Section: Introductionmentioning

confidence: 99%

“…in worn shoes: less maximum lean and less forward lean at toe-off for the torso; reduced maximum dorsiflexion and increased plantarflexion at toeoff), 24 but the degree of shoe degradation was unknown. Conversely, footwear material studies have reported that shoe degradation decreases midsole thickness, compliance, and the shoe's ability to absorb energy, [15][16][17][18][19][20][21][22] but have not examined how these changes influence running biomechanics. For the running athlete, a probable consequence of reduced thickness and compliance is an increased loading rate, 4,25 which has been reported as a risk factor for running overuse injuries.…”

Section: Introductionmentioning

confidence: 99%

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Effect of mechanically aged minimalist and traditional footwear on female running biomechanics

Lippa

Bonacci

Collins

et al. 2019

Proceedings of the Institution of Mechanical Engineers, Part P:

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The purpose of this study was to improve the understanding of human–material interactions by combining polymer engineering and biomechanical approaches. The forefoot and heel of traditional shoes and minimalist running shoes were degraded using a mechanical aging protocol to quantify (1) the effect of subject-specific degradation and (2) human biomechanical effects due to decreased material properties. Four recreational-level female participants ran in the shoes pre-mechanical aging to determine the aging protocol input parameters and post-mechanical aging to evaluate the effect of degradation on kinematics and kinetics. Initial biomechanics translated into different mechanical aging input parameters among conditions: 500 greater number of impact cycles for minimalist shoe, 430 N higher peak force for forefoot, 75 kPa greater peak stress for the heel, 3.1 and 13.7 kN/s greater loading rates for minimalist shoe and the heel, and recovery time 220 ms greater for the heel. From mechanical aging, the shoe types and regions lost 1.2–1.8 mm thickness and 38%–54% energy absorption overall, while drop decreased 0.6 mm for traditional shoe only. Samples degraded at different rates depending on runner-specific input parameters. Human kinematics and kinetics were affected by both shoe type and aging. Aging of the shoes decreased knee flexion velocity (1°/s; p = 0.01), decreased ankle dorsiflexion during stance (3°, p = 0.01), and increased the vertical loading rate (4 BW/s, p = 0.01). The results support previous findings that different footwear influence running biomechanics and concurrently advance footwear science to show running biomechanics are also influenced by shoe degradation rates, such that unique and intuitive human–material interactions are apparent.

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Section: Ma Input Parametersmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Effect of mechanically aged minimalist and traditional footwear on female running biomechanics

Lippa

Bonacci

Collins

et al. 2019

Proceedings of the Institution of Mechanical Engineers, Part P:

Self Cite

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“…Presently, various foam materials derived from synthetic polymers, such as ethylene-vinyl acetate or polyurethane, are routinely employed in footwear products due to their well-known ability to absorb impact force. However, a nontrivial drawback of such foam materials is their relative lack of durability [ 2 , 7 , 8 , 9 , 10 , 11 ]. Therefore, to improve the durability of shoes and retain comfort, parts of many shoes are constructed from both natural rubber (NR) and synthetic materials.…”

Section: Introductionmentioning

confidence: 99%

Optimization of the Rubber Formulation for Footwear Applications from the Response Surface Method

et al. 2020

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Impact force remains the primary cause of foot injury and general discomfort with regard to footwear. The footwear industry traditionally relies on modified elastomers (including natural rubber) whose properties can be physically adjusted by varying the constituents in the rubber formulations. This work aims to investigate the effect of filler/plasticizer fractions on shock attenuation of natural rubber soles. The statistical response surface method (RSM) was used to optimize the loading of natural rubber, fillers (carbon black and china clay) and a plasticizer (paraffinic oil). A novel predictive equation addressing the effects of additives on the physical and mechanical properties of the shoe sole was successfully created using the RSM. Our results demonstrate how the concentrations of these components regulate final properties, such as impact force absorption and hardness, in the commercial manufacture of shoe soles. While a higher loading level of plasticizer promotes reductions in hardness and impact force, as well as energy dissipation, in these modified elastomers, these properties were improved by increasing the filler content.

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“…Ethylene vinyl acetate (EVA) is a kind of copolymer with good elasticity, low temperature resistance, electrical insulating, etc. It has been widely used as foam material, wire and cable, film, etc. Ethylene vinyl acetate is flammable because of its structure, which brings the possibility of fire during its lifetime.…”

Section: Introductionmentioning

confidence: 99%

Preparation of urea formaldehyde microsphere and its effect on flame retardant ethylene vinyl acetate composites

Liu

2018

Polymers for Advanced Techs

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Urea formaldehyde microsphere (UFM) was prepared and used with organic montmorillonite (OMMT) to modify the flame retardant efficiency of ethylene vinyl acetate copolymer (EVA)/intumescent flame retardant (IFR) composites. The results show that single IFR may modify the flame retardancy of EVA, but its efficiency is not good enough. The EVA composite containing 21 wt% IFR is just classified the UL_94 V2 and has a limiting oxygen index (LOI) 24.7 vol%. Combining UFM with IFR does not improve the flame retardancy of EVA/IFR composites, and blending OMMT with IFR only improves its LOI. Adding 2 wt% UFM, 2 wt% OMMT, and 17 wt% IFR into EVA, it obtains the UL_94 V0 without melt dripping and a LOI 29.0 vol%. Also, the peak heat release rate and total heat release decrease a lot. Good synergistic effects among IFR, UFM, and OMMT improve the char residues and modify the char micromorphology of EVA composites, which provide better protect for the underlying resin.

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Mechanical Ageing Protocol Selection Affects Macroscopic Performance and Molecular Level Properties of Ethylene Vinyl Acetate (EVA) Running Shoe Midsole Foam

Cited by 11 publications

References 19 publications

Effect of mechanically aged minimalist and traditional footwear on female running biomechanics

Effect of mechanically aged minimalist and traditional footwear on female running biomechanics

Optimization of the Rubber Formulation for Footwear Applications from the Response Surface Method

Preparation of urea formaldehyde microsphere and its effect on flame retardant ethylene vinyl acetate composites

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