Journal of Plastic Film & Sheeting

A panel of 48 assessors evaluated a taint in water, packed in test pouches made of low density polyethylene (LDPE) lined aluminium. This panel agreed upon eight descriptive attributes (in Dutch): metallic (metaal), syn thetic (synthetisch), dry (droog), rough (stroef), astringent (wrang), musty (muf), sickly (wee) and penetrating (doordringend). Fourteen assessors, selected with a standard triangle test, were asked to judge intensities for these attri butes on a visual analogue scale. Factor analysis reduced the original data- matrix to a six dimensional one losing only 6.4% of the original variance. Syn thetic and penetrating loaded high on one factor as well as rough and astringent on another one. Musty, sickly, metallic and dry loaded high on sepa rate factors.

Direct dynamic headspace analysis of the LDPE-lined test pouches gave mainly peaks of branched alkanes of 12 carbon atoms. However, dynamic head space analysis of water in contact with the LDPE layer of the test pouches showed no alkanes but (C₄ - C₁₁) aldehydes and ketones.

Roll coating is at the heart of production of films which can be composed of many layers. The fluids may be Newtonian or shear-thinning, usu ally described by a power law. The fluids' rheology along with operating param eters, such as roll speeds, their size and minimum gap width, must be con sidered in order to achieve a desirable coating thickness. Numerical studies are undertaken based on the Lubrication Approximation Theory (LAT) for the isothermal analysis of forward roll coating of multilayer sheets, which are con sidered as slightly shear-thinning fluids (power-law indices > 0.6). The solu tion process is based on an iterative Newton-Raphson scheme. It provides the unknown a priori flow domain, interface locations for different layer combina tions, layer thicknesses after splitting, pressure and stress distributions, torque and power consumption. A parametric study based on power-law index ratios and consistency index ratios for double-layer sheets is presented. A case of a 3-layer roll-coated sheet is also examined.

Many papers have been written presenting properties expected from different blends of linear low density polyethylene (LLDPE) and high pressure low density polyethylene (LDPE) [1-3]. This paper attempts to corre late the properties obtained from blends with specific end-use markets (i.e., gar ment bags, shrink wrap, ice bags, and general purpose bags). The effect on ex trusion rate, bubble stability and draw down are discussed for blends of butene and hexene LLDPE with fractional melt index (MI), 2 MI, and 6 MI LDPE homopolymers as well as 3% vinyl acetate (VA)-LDPE copolymers.