Abstract: The present invention relates to a reaction mixture for manufacturing an inorganic-filler based closed-cell rigid polyurethane or polyisocyanurate (PU or PIR) containing foam having a calorific value below 6 MJ/kg, preferably below 4.5 MJ/kg, more preferably below 3 MJ/kg, measured according to EN ISO 1716, the reaction mixture comprising: At least one polyisocyanate-containing compound; At least one isocyanate-reactive compound; An inorganic filler composition; At least one physical blowing agent; characterised in that said inorganic filler composition has bulk density higher than 2 g/cm3, preferably higher than 2.1 g/cm3, more preferably higher than 2.2 g/cm3, even more preferably higher than 2.4 g/cm3.

Abstract: A reactive mixture comprising a Fire, Smoke and Toxicity retardant (FST) composition for making a polyisocyanurate and/or polyurethane (PIR/PUR) comprising material, said FST composition comprising: a) at least one compound having at least one ethylenically unsaturated moiety having a number average equivalent weight<160 g/mol, and b) optionally one or more radical initiator compound characterized in that the onset temperature for radical polymerization (Tonset) of the ethylenically unsaturated compound with or without the radical initiator is 2° C. up to 40° C. lower than the maximum reaction temperature achieved during the process for making the PIR/PUR material (reaction exotherm (Treaction)).

Abstract: A polyisocyanurate and/or polyurethane (PIR/PUR) comprising material having improved Flame, Smoke and/or Toxicity (FST) retardancy is disclosed and a method for forming said PIR/PUR comprising material. The PIR/PUR material is comprising at least 0.2 wt % of compounds having a number average equivalent weight <160 g/mol and at least one non-polymerized ethylenically unsaturated moiety based on the total weight of the PIR/PUR comprising material, and optionally 0.01 wt % up to 1 wt % of one or more radical initiator compounds based on the total weight of the PIR/PUR comprising material.