Back SearchTitle: MORPHOLOGY AND MECHANICAL PROPERTIES OF FOAMED POLYETHYLENE BLENDS
Page Range: p.211-236
Author(s): Yaolin Zhang; Rodrigue D; Ait-Kadi A
File size: 259K
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Issue Year: cp
Volume: 22
Issue No: No. 4
Abstract
Blends of PE (a commercial HDPE and a Ziegler-Natta-synthesised PE) were foamed (593-782 kg/cu m) by compression moulding and their morphology was investigated to examine the effect of polymer molecular structure. It was found that the cell diameter distribution could be approximated by a truncated normal distribution. Torsion, flexural and tensile properties were also measured at different strain rates. It was found that the shear, flexural and Young's moduli of blends and their foams increased with increasing strain rate, while their normalised moduli were almost unchanged. It was also confirmed that thin skins had a definite effect on shear and flexural moduli, but a negligible effect on tensile moduli. Normalised yield strength and strain were almost independent of strain rate while break strain and toughness increased with increasing molec.wt. and decreasing strain rate. 34 refs.
Title: AN INVESTIGATION INTO VOC EMISSIONS FROM POLYURETHANE FLEXIBLE FOAM MATTRESSES
Page Range: p.237-259
Author(s): Hillier K; Schupp T; Carney I
File size: 108K
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Issue Year: cp
Volume: 22
Issue No: No. 4
Abstract
The emissions of volatile species from flexible PU foam mattresses were investigated using large-scale chamber tests designed to replicate the product use as mattress cores. Various trace impurities were identified and their concentrations were measured for input into a human health and toxicity risk assessment, which concluded that none was injurious to health. The raw materials used to make the foam were analysed in order to identify the source of emissions and routes to their reduction or elimination. Several analytical artefacts were identified and some recommendations made for their avoidance. Detailed product knowledge was essential to the reliable interpretation of analytical data. A quantitative risk assessment was carried out on each of the volatiles. No evidence of any human health risk was identified from the 'worst-case' exposure model used. 20 refs.
Title: SECOND EXPANSION CYCLE IN ULTRAMICROCELLULAR FOAMS
Page Range: p.260-268
Author(s): Nawaby A V; Handa Y P
File size: 141K
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Issue Year: cp
Volume: 22
Issue No: No. 4
Abstract
Ultramicrocellular PMMA foams made from the low temperature rubbery phase, obtained by saturating the polymer with carbon dioxide at 0C and 34 atm, was subjected to a second expansion cycle by heating it rapidly to temperatures in the range 30 to 120C. The blowing agent for the secondary expansion was either the residual carbon dioxide in the foam at about 19 wt % level or fresh carbon dioxide re-equilibrated at 0C and 34 atm to a loading level of about 29 wt %. In the former case, the second expansion cycle led to lower foam densities, whereas in the latter case, it led to stretching and re-orientation of the cell walls with no significant gain in further foam density reduction or cell density increase. 9 refs.