Dean Thetford

Evolution of reactive unsaturated interfacial modifiers for polyolefin based composites

The development of a novel reactive unsaturated interfacial modifier for filled (magnesium hydroxide, aluminium hydroxide and calcium carbonate) polyolefins is reviewed. Initial work explored maleimide functional candidate molecules including 1,3-phenylene dimaleimide (1,3-PDM) and a range of linear alkyl dimaleimides. Most of the dimaleimides were very effective interfacial modifiers in polypropylene and poly(ethylene-co-vinylacetate) (18% w/w vinylacetate) based composites. However, the dimaleimides caused the composites to have a distinct pink/brown colouration apart from when the maleimide groups were spaced by a C12 alkyl chain. The problem with colour and high effective dosage prompted a switch to unsaturated carboxylic acid based systems. The performance of a range of unsaturated carboxylic acids and the hexafunctional monomer trimethylolpropane triacrylate are reviewed, together with a novel oligomeric unsaturated carboxylic acid (OUCA) based system developed by the Noveon Division of Lubrizol Limited. The data obtained from this series of interfacial modifiers, and adsorption studies on 1,3-PDM and OUCA, afforded some insight into the competing factors (such as the strength of adsorption versus ability to form a polymerised interfacial layer and the ability to react with matrix chains) that significantly affect the coupling performance of interfacial modifiers.

A novel coupling agent technology

The results from the development of a novel coupling agent technology, which should very soon be launched commercially, will be described. The presentation will particularly focus on the performance of the technology in ATH filled EVA systems, and its benefits over existing coupling agent technologies. In particular a rheological profile, giving the potential for lower energy consumption and/or higher processing speeds, can be demonstrated without any significant diminution in the material properties that would be obtained using conventional coupling agents. Other properties related to the fire resistance and electrical stability will be reviewed, and the processing conditions and formulation modifications required to optimise this performance will also be discussed. Other applications for this coupling technology, including calcium carbonate filled EVA systems and hopefully calcium carbonate filled EPDM rubbers and/or PP homopolymer, will be covered in less detail, but should give some indication of the potential scope of the technology.The results from the development of a novel coupling agent technology are described. The work was particularly focussed on ATH filled EVA systems for wire and cabling applications. After an initial screening of 35 potential coupling agents, 2 were selected for further evaluation on the basis of their ability to increase tensile strength and elongation to break, and to reduce torque during compounding in a Brabender Plasticorder. Low cost, low volatility and low toxicity were also important selection criteria. Brabender Plasticorder results were backed up by twin screw compounding and extrusion studies, leading to the selection of the final candidate, which will be launched commercially. The influences of added peroxide and antioxidant have also been investigated. Finally, a short evaluation has been made of the performance of the candidate coupling agent in calcium carbonate filled EVA and calcium carbonate filled PP homopolymer.