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Cushioning energy dissipation in foam polymers
Author(s) -
Peleg Kalman
Publication year - 1980
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760201107
Subject(s) - cushioning , cushion , materials science , dissipation , composite material , polymer , polyurethane , polyethylene , polystyrene , bushing , expanded polystyrene , deflection (physics) , structural engineering , thermodynamics , physics , optics , engineering
Derivation of dynamic hysteresis loops (force deflection curves) of shock absorbing bushing materials by means of double integration of accelerometer signals is described. The significance of energy dissipation capability of expanded polymers with associated peak deceleration and maximal strain is discussed along with damping characteristics. A “Cushion Efficiency Factor” is introduced, in terms of the ratio of peak acceleration transmitted by a cushion to the energy dissipated per unit cushion area. Three types of expanded polymers commonly used as cushioning materials are evaluated accordingly. Expanded polyethylene (2,2 lb/cu ft), expanded polyurethane (2.1 lb/cu ft) and polystyrene filled polyurethane (1.7 lb/cu ft), all conditioned at 73°F and 50 percent RH. For each of these, two effective drop height tests were conducted, with heights of 12 in. and 42 in. Depending on the polymer type, peak product accelerations were between 33–38 g's in the 12 in. drops and 65–118 g's in the 42 in. drops, with corresponding maximal cushion strains of 0.15–0.20 and 0.39–0.47, respectively. Energy dissipating capabilities of polymers tested during first half cycle following drops were 148–179 lb in. and 477–708 lb in., respectively, depending on polymer type. This approach may facilitate optimal selection of cushioning materials for shock protection in packaging, as well as enable development of improved polymers for cushioning applications.