a) 15-40 wt. % of a thermoplastic polymer, preferably EVA; b) 20-40 wt. % of magnesium oxide or hydroxide to reduce flammability and smoking; c) 10-25 wt. % of aluminium oxide trihydrate or hydroxide as flame retardant filler; d) 10-20 wt. % of chlorinated paraffin hydrocarbon, e.g. 70% chlorinated wax, aiding processing; and e) 0-15 wt. % of antimony trioxide.