Although the level of transition‐metal catalyst residues in polyethylene (PE) has been drastically reduced over the years, they can still give rise to discoloration, particularly when associated with other additives such as antioxidants. This first of this series of papers screens a variety of candidate color suppressants featuring a range of functional groups, including alcohols, amine/sulfur compounds, and acid‐containing species. These candidate color suppressants were melt‐blended into a Ziegler‐Natta linear low‐density PE in combination with 2,2′‐isobutylidenebis(4,6‐dimethylphenol) (a highly discoloring hindered bisphenol antioxidant) and zinc stearate antacid. Yellowness index measurements made after multiple extruder passes indicated that dipentaerythritol (DPE) and triisopropylamine (TIPA) gave good color inhibition and, in some cases, outperformed established phosphites. The DPE and TIPA were found (via melt flow rate measurement) not to affect melt stability, and hydroperoxide determination revealed that DPE had no peroxide decomposition activity. The latter results indicate that the color‐suppression mechanism of DPE and TIPA is different from that associated with phosphites. J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers

Backscattered electron scanning electron microscope (SEM) imaging of the distribution of metal hydroxide filler particles in cryo‐cut surfaces of poly(ethylene‐ran‐vinyl acetate)/metal hydroxide composites followed by multifractal analysis of the images has led to a numerical measure of dispersion quality, i.e. the width (D₀–D₄) of the multifractal spectrum. The D₀–D₄ values were then determined for a series of composites that formed a quadratic algorithm screening experimental design where the following four factors: type of filler (magnesium hydroxide or aluminium hydroxide), filler loading (30% w/w–60% w/w), vinyl acetate content (20% w/w and 28% w/w), and isostearic acid coating of the filler, were investigated. Two multiple regression models were constructed to examine the dependence of tensile strength and elongation at break on dispersion quality and composite formulation. Predictions of tensile strength and elongation at break were forecast and the results compared with experimentally measured data. A positive correlation was found between the as measured data and predictions from the multiple regression model. Examination of the models indicated that composite tensile strength and elongation at break decreased as a function of decreasing dispersion quality confirming the importance of dispersion quality in defining ultimate material properties.