Study On Properties Of Chlorinated Polypropylene/Epoxy Resin Adhesives And Their Application In Insulators

Chlorinated polypropylene has good adhesion to polyolefin substrates,and is widely used in adhesives,coatings,inks,etc.In order to further improve the adhesion with polar materials,polar groups are introduced into chlorinated polypropylene molecules by blending or grafting,however,there are few studies on epoxy resin-modified chlorinated polypropylene adhesives.In addition,polyolefin composite insulator is a new developed insulator for transmission lines.In order to solve the problem of adhesion between polar epoxy glass fiber core rod and non-polar polyolefin sheath(shed),this paper studied the properties of chlorinated polypropylene/epoxy resin adhesives,and explored the feasibility of their application in the bonding of polyolefin composite insulators.The main work is summarized as follows:1.Study on properties of chlorinated polypropylene/epoxy resin adhesivesThe adhesives with different chlorinated polypropylene/epoxy resin ratios are designed.According to the content of main resin,they are defined as chlorinated polypropylene-toughened epoxy adhesive and epoxy-modified chlorinated polypropylene adhesive,respectively.(1)Chlorinated polypropylene was used as a toughening agent to modify epoxy resin,the effects of chlorine content(19～27%)and dosage(5～15phr)of chlorinated polypropylene on the mechanical properties,thermal properties,electrical insulation and water absorption of epoxy adhesive were studied.The results showed that,compared with the untoughened epoxy adhesive,the toughened epoxy adhesive with 15phr chlorinated polypropylene(chlorine content 24%)exhibited the best overall performance,and its elongation at break increased from 6.0%to 32.6%,the impact strength increased from 13.3k J/m~2 to 46.8 k J/m~2,and the T peel strength of aluminum-aluminum samples increased from0.11 k N/m to 1.20 k N/m.In addition,the water absorption of the toughened epoxy adhesive after being immersed in water for 60 d at 23℃was 2.31%,the water absorption and electrical insulation were all not affected.(2)Chlorinated polypropylene was modified with epoxy adhesive to improve its adhesion,and the effects of the dosage of epoxy adhesive and the type of curing agent on the mechanical properties,electrical insulation and water absorption of chlorinated polypropylene adhesive were studied.The results showed that when 30phr epoxy adhesive(hydrogenated bisphenol A epoxy resin/N-(β-aminoethyl)-γ-aminopropylmethylbimethoxy silane)was used to modify the chlorinated polypropylene resin,the tensile strength increased from 6.0 MPa to 25.4 MPa,the T peel strength of the zinc-zinc and aluminum-aluminum samples increased from 0.30 k N/m and 0.60 k N/m to 2.10 k N/m and 3.0 k N/m,respectively.The surface resistivity and volume resistivity of the modified chlorinated polypropylene were increased by two orders of magnitude than those before modification.The water absorption of the modified chlorinated polypropylene was only 1.02%after being immersed in water at 100℃for 100 h,which is much lower than that before modification(154%).2.Study on application of chlorinated polypropylene/epoxy resin adhesives in polyolefin insulatorsThe prepared chlorinated polypropylene/epoxy resin adhesives were used to bond epoxy core rod and polyolefin sheath,and the interface tightness,bonding strength and water resistance of the epoxy core rod-polyolefin sheath samples were studied.The results showed that the core rod-sheath samples bonded with epoxy-modified chlorinated polypropylene adhesive exhibited good interface tightness and excellent bonding strength,and the highest bonding strength of the core rod-sheath samples was up to 7.4 MPa;After dye penetration test,there was no dye rising from the bonding interface;After the core rod-sheath samples were boiled for 100 h,the leakage current of water diffusion was only 40.6μA(12 k V voltage),meeting the requirement of less than 100μA of the national standard.Finally,the practical application effect of chlorinated polypropylene/epoxy resin adhesives in 35 k V polyolefin composite insulators was explored.