Ultraviolet light radiation crosslinked silicon rubber and preparation method thereof

- Mar 15, 2019-

Since the silicone rubber has excellent heat resistance, cold resistance, environmental resistance, electrical insulation properties, low compression set resistance and fatigue properties of many aspects like, has been widely used in electronics, appliances, cars, machinery manufacturing, chemicals, food, daily necessities, health and other fields.

Currently, the crosslinking method of the silicone rubber are mainly two: chemical cross-linking method and the high-energy radiation. Silicone rubber vulcanized by chemical cross-linking manner divided into RTV and HTV two major categories, wherein the curing temperature depending on the vulcanizing agent, a peroxide type and addition, the corresponding radical curing mechanism and curing addition cure. The former is produced by high temperature decomposition of peroxide crosslinking radical initiator, since the commercial silicone rubber, silicone rubber products, most are by way of forming a peroxide initiated vulcanization (crosslinking) peroxide, vulcanized maturation process, almost all of the heat required to meet the vulcanized silicone rubber products, but have some toxic substances harmful decomposition of peroxide vulcanizing agent, often require postcure, while for the light-colored or transparent articles vulcanizing after the meeting discoloration. Since the 1970s, addition-cure systems began to be in silicone rubber applications, the reaction mechanism is a hydrosilylation reaction in the presence of a catalyst of Group VIII transition metals, such as Pt, Pd, Ni, Co and the like, the vulcanization (cross-linking) no small molecule during the precipitation, the curing process itself does not produce any by-products; low catalyst amount, a vulcanized article for human safety; atmospheric temperature can be vulcanized and a depth vulcanization. However, the system as molybdenum catalyst system easily with N, organic unsaturated bond P, S and other organic or Sn, Pb, Hg, Bi, As and other heavy metal ions and compounds containing an alkynyl group toxic reactions and loss of activity. Many researchers question for the catalyst is easily deactivated and a lot of research reports, such as molybdenum catalyst microencapsulation, Preparation of Mo - inhibitor complex and the like, but the results are not ideal.

Of silicone rubber)) (Nuclear Instruments and Methodsin Physics Research B 243 in the Masoud Frounchi and Susan Dadbin << Comparison between electron-beamand chemical crosslinking (2006) 354-358) - the text set forth in the need for chemical additives under the conditions, the silicone rubber can well be electron beam radiation crosslinked, silicone rubber properties after crosslinking are superior chemical crosslinking. And high-energy radiation crosslinking reaction can be carried out at room temperature, cross-linking uniformity, and easy control.However, highly cross-linked high-energy radiation crosslinking equipment investment, operation and maintenance complex, demanding protection, high production costs, will lead to high energy structure of the material, resulting in deterioration of performance, etc. These problems become particularly evident. UV cross-linking is a cross-linking method after high-energy radiation crosslinking and chemical crosslinking recent development in recent years has been successfully applied to an optical cross-linked wire and cable industrial production. Compared with high-energy radiation and chemical cross-linking methods, UV cross-linking method has many unique advantages: simple process equipment, less investment; easy operation, safety go not critical, easy maintenance; energy saving, environmental pollution; and ultraviolet radiation damage to the material is small, excellent mechanical properties and electrical properties of the product; the product cost is low.

In China Patent Application No. 200910126729.2 describes a polyorganosiloxane, acrylated silicone oil composition containing diaryl ketone radical photoinitiator is a photo-crosslinkable, the crosslinking the product has good mechanical properties. However, the composition is applicable only to dielectric insulating layer or optical cable and requires a protective outer coating sheath. And the photo-crosslinkable compositions require repeated a plurality of times after irradiation to reach a satisfactory degree of crosslinking, not only increases the production time making the process complicated. Common attraction between molecules is very low silicone rubber, raw rubber elastomer after curing direct tensile strength of no more than 0. 14MPa, without no reinforcement value. Therefore, after the silicone rubber is reinforced necessary to add an inorganic filler to meet the practical production.

In recent years, the applicant invented a novel UV crosslinking (Chinese Patent Publication No.: CN1218963 and CN 1919571), and have been put into industrial production of wire and cable crosslinked material. The new technology has unique advantages: low investment in equipment required for cross-linking, simple process, easy operation and maintenance, energy saving, high efficiency, low cost of the product, excellent high temperature properties and mechanical properties, and because the use of ultraviolet light as irradiation source, applied to the production of different sized photo-crosslinked product.