Abstract
“A new non-post treated fine precipitated aluminium-tri-hydrate quality has been developed, offering the basis for the next generation of halogen free flame retardant compounds. The paper outlines the excellent powder handling properties and the outstanding performance of highly filled polymers”
Halogen free flame retardant plastics for cable insulation and sheathing, known as LSFOH (low smoke, free of halogen) compounds became large volume products since the market introduction of fine precipitated aluminium-tri-hydrates (ATH) qualities in the beginning of the 80's. While former ATH improvements focused on product purity and electrical properties, recent developments responded to the growing importance of continuous compounding techniques. The focus on compound output and processing behaviour of fillers was answered by ATH qualities having higher bulk density and better flow properties. These improvements have been achieved by physical and chemical post treatments of the precipitated products. While giving the expected benefits in powder handling, detrimental effects have been observed for mechanical and especially for electrical compound properties.
A new generation of non-post treated fine precipitated ATH has now been developed, offering excellent powder processing, but also outstanding compound properties. The paper outlines filler processing behaviour, presenting results of flow-, conveyance-, metering and dust-behaviour investigations. Special attention is given to compound user's benefits. Low melt viscosities and high extrusion speed in the production of LSFOH cables are identified as core properties of compounds filled with this new ATH quality.