Expandable compositions containing aromatic vinyl polymers having self-extinguishing properties and improved processability

A molded item formed from an expandable polymeric composition, the composition comprising:

• a) a polymeric matrix containing vinyl aromatic polymers and/or copolymers;
• b) from 0.1% to 20% by weight, calculated on the polymeric matrix (a), of an athermanous agent comprising coke or carbon black;
• c) from 0.01% to 4% by weight, calculated on the polymeric matrix (a), of at least one non-polymeric brominated flame retardant additive;
• d) from 0.01% to 10% by weight, calculated on the polymeric matrix (a), of at least one brominated polymer containing at least 50% bromine;
• wherein said at least one brominated polymer that contains at least 50% bromine, is selected from copolymer Tetrabromobisphenol A 2,2 Bis [4-(2,3 epoxypropoxy)-dibromophenyl]-propane, brominated polybutadiene, and brominated styrene-butadiene block copolymers, and mixtures thereof;
• e) from 0.01% to 5% by weight, calculated on the polymeric matrix (a), of a synergistic flame retardant additive;
• f) from 1% by weight to 10% by weight of at least one blowing agent, wherein said molded item is formed from molded expanded granules comprising the composition, and said molded item has a density of not more than 16.1 g/I, an HBr content of not more than 380 ppm measured by the Method for the Determination of Bromides and a thermal conductivity of not more than 30.8 mW/mK as measured according to method ISO 8301;
• wherein said molded item passes fire requirements of test DIN 4101-B2.