GB747478A - Improvements in or relating to polymeric substances - Google Patents

Abstract

Polymers of very high molecular weight, i.e. over 25,000, characterised by a chain structure wholly or largely of carbon atoms, a substantial proportion of which have one or two hydrogen atoms attached, e.g. polyethylene having a molecular weight of 40,000 to 50,000, are subjected to the action of up to one unit of ionizing radiation, e.g. high energy neutrons, gamma rays, X-rays, high energy protons, electrons or helium ions, or radiations which give rise to high energy radiations, e.g. thermal neutrons. The irradiation may be carried out as described in Specification 732,047 to give a dose of 0.02 to 1.0 unit or where only gamma rays are used 1.0 X 106 to 50 X 106 roentgens. Oxidation may be prevented by excluding oxidants or adding antioxidants. In an example the polyethylene is enclosed in an aluminium can and irradiated in a thermal nuclear reactor operating at a power level of 3 mega-watts, the thermal neutron flux being about 1012, at a temperature of 80 DEG C. for two hours. The product is insoluble and has a higher tensile strength at above 120 DEG C. than irradiated polyethylene of lower molecular weight.ALSO:Polymeric substances of very high molecular weight, i.e., over 25,000, characterized by a chain structure wholly or largely of carbon atoms, a substantial proportion of which have one or two hydrogen atoms attached, e.g. polyethylene having a molecular weight of 40,000 to 50,000, are irradiated with high energy neutrons, gamma rays, X-rays, high energy protons, electrons or helium ions or other ionizing radiations, or radiations which give rise to high energy radiations, e.g. thermal neutrons. A thermal nuclear reactor may be used giving 2 X 1015 and 1017 thermal neutrons per square centimetre with gamma rays to give a dose of 0.02 to 1.0 unit or where only gamma rays are used 1.0 X 106 to 50 X 106 roentgens. In an example the polyethylene is irradiated in a thermal nuclear reactor operating at a power level of 3 mega-watts, and a thermal neutron flux of about 1012, at a temperature 80 DEG C. for two hours to give insoluble products with a higher tensile strength at above 120 DEG C. than irradiated polyethylene of lower molecular weight. Oxidation during irradiation may be prevented by anti-oxidants or by inclusion of oxidants. Specification 732,047 is referred to.