laminae described above the composite sheet can then be cut into suitable lengths for thermoforming into any desired configuration one of which is illustrated by fig2 the resulting liner wall 2 is then assembled with the outer cabinet wall 1 and in situ foaming of the insulation material is performed the resulting structure exhibits impact strength and substantial elimination of thermal cracking and of blistering in situ foaming involves admixing an isocyanate with a masterbatch the masterbatch comprises 60 to 70 percent of a polyol 0 3 to 1 5 percent of a surfactant 0 5 to 3 0 percent of a catalyst 0 4 to 2 5 percent of water and 12 to 30 percent of the blowing agent the isocyanates used in applicances include tdi and pmdi tdi comprises an 80 20 mixture of 2 4 and 2 6 isomers of products produced by dinitration of toluene catalytic hydrogenation to the diamines and phosgenation cf kirk othmer encyclopedia of chemical technology vol 23 page 581 third edition pmdi is the reaction product formed by nitration of benzene and reduction to produce aniline reacting aniline with formaldehyde in the presence of hydrochloric acid to produce a mixture of oligomeric amines which are phosgenated to yield pmdi cf kirk othmer encyclopedia of chemical technology vol 23 page 581 third edition the blowing agent can be freon or freon substitutes which are partially halogenated lower hydrocarbon of 1 to 5 carbon atoms usually of 2 to 4 carbon atoms halogenated includes fluorinated and or chlorinated by 34 partially halogenated 34 is.