Oxidation and ignition of flexible polyurethane foams have been investigated by observing the effects of internal and external heating. External temperatures of some 190°C are required to induce combustion. Internal temperatures of 250 −350°C initiate a self‐propagating internal reaction which results in foam ignition when the reaction reaches the foam surface. The stability of a polyurethane foam to such heating increases with the age of the foam.

Polymers of methyl methacrylate, methyl acrylate, vinyl acetate, and acrylonitrile labeled with carbon‐14 in the functional groups have been prepared. The labeled polymers have been subjected to hydrolysis, and the specific activities before and after treatment have been compared. Almost complete hydrolysis of polymethyl acrylate and polyvinyl alcohol is readily achieved. It has been confirmed that polymethyl methacrylate is rather resistant to hydrolysis, but ester endgroups in this polymer are easily detached. During treatment of polyacrylonitrile with acid or alkali, no carbon atoms are lost from the polymer.

14C-azoisobutyronitrile has been used to sensitize the polymerization of acrylonitrile at 60°C. Efficiencies of initiation have been determined for homogeneous reactions in dimethylformamide and for heterogeneous reactions in benzene and carbon tetrachloride. Apparent efficiencies are low in carbon tetrachloride probably because of a reaction between the solvent and the radicals derived from the initiator. This effect may be present to a smaller extent in dimethylformamide. There is further evidence that combination is the predominant method for termination in the polymerization of acrylonitrile at 60'C in dimethylformamide.

No abstract

Caprolactam has been polymerised by sodium hydride in the presence of isocyanate terminated polymers. The latter participate in the initiation reaction and allow the preparation of materials where the prepolymer can amount to 50% of the product.There is evidence that block copolymers are formed, and the properties of polycaprolactam are considerably modified by the use of such activators. Styrene-butadiene or, particularly, caprolactone based isocyanates give materials having properties similar to the harder thermoplastic polyurethanes. The dependence of properties on the nature and amount of the polymeric activators, and the conditions of preparation and processing, have been investigated. Crystalline morphology has also been examined. Tensile strengths of 50 MN/m2 with 550% elongation at break are readily attainable with these materials. ZUSAMMENFASSUNG:Caprolactam wurde, initiiert durch Natriumhydrid, in Gegenwart von Polymeren mit Isocyanatendgruppen polymerisiert. Die Endgruppen nehmen an der Startreaktion teil und ermoglichen die Herstellung von Materialien, die bis zu 50% des Prepolymeren enthalten.Dabei entstehen Blockcopolymere; die Eigenschaften von Polycaprolactam werden durch solche polymere Aktivatoren betrachtlich modifiziert. Aus Styrol-Butadien oder besonders aus Caprolacton aufgebaute Isocyanate ergeben Materialien mit ahnlichen Eigenschaften wie die harteren thermoplastischen Polyurethane. Die Abhangigkeit der Eigenschaften von Art und Menge des polymeren Aktivators und von den Herstellungsbedingungen wurde untersucht. Ferner wurde die Kristallitmorphologie untersucht. Zugfestigkeiten von 50 MN/mZ bei 550% Bruchdehnung werden bei diesen Materialien erreicht.