| Polyethylene terephthalate(PET)is one of the most widely used polymers.Nevertheless,PET is bonded with great difficulty as a result of the characteristics of low surface energy,low polarity and crystallinity.Commonly,in order to overcome this drawback,various surface pretreatment methods have been developed.However,surface pretreatment can also cause many problems.Therefore,the aim of this work is to enhance the bonding strength between self-made adhesive and untreated PET substrate.In this work,polyurethane acrylate(PUA)was synthesized from isophorone diisocyanate(IPDI),polycaprolactone diol(PCL),and 2-hydroxyethyl methacrylate(HEMA),and the test result of FT-IR demonstrated the success of the reaction.Optimal UV curing formula was developed using PUA acted as oligomer;tetrahydro furfuryl alcohol(THFA),N,N-dimethylacrylamide(DMAA),and 1,6-Hexanediol diacrylate(HDDA)acted as reactive diluents;1-Hydroxy-Cyclohexylphenyl-Ketone(C-184)acted as photoinitiator,and the lap shear strength bonding untreated PET substrate reached 3.4 MPa in accordance with ASTM D1002.Additionally,it was found that the shear strength of the formula which used polyester resin(CN7001)as oligomer can reach 5.2 MPa.Further,silicone was introduced into the synthesis of PUA,and silicone-modified poly(urethane-acrylate),including SiPUA-1 and SiPUA-2,were prepared successfully by replacing PCL-2000 with hydroxypropyl silicone oil(JHY-20).The formulas which used SiPUA-1 as oligomer showed excellent adhesion to untreated PET substrate,and the shear strength reached 6.5 MPa.And the issue of oxygen inhibition was resisted by adding active amines or micronized waxes into silicone-modified formulas.Finally,the properties of self-made UV-curable adhesive was conformed to the requirements of application,and the product has been put into production.In order to solve the problem that UV curing technology is only effective on transparent substrate and cannot reach shadow region,a novel UV/moisture dual-curable silicone-modified poly(urethaneacrylate)(SiPUA)was synthesized successfully.The SiPUA oligomer contains C=C bond which is used to carry out photo-curing reaction and isocyanate group which is used to carry out moisture-curing reaction.It was found that UV/moisture dual-curable formulations showed higher bonding strength to untreated PET substrate in comparison to UV-curable formulations.In depth,this work investigated the influence of moisture curing agent(3390)on properties of UV/moisture dual-curable adhesives.It was found that the issue of oxygen inhibition can be solved and mechanical properties can be improved further by adding suitable 3390.Specifically,by addition of 3390 to formulas in the range of 0-6 wt%,the shear strength increased gradually from 5.65 to 7.73 MPa;at 3390 > 6 wt%,the shear strength tended to weaken gradually.When the addition of 3390 range of 3-6 wt%,optimal mechanical performance can be obtained.The bonding strength of self-made UV/moisture dual-curable adhesive to untreated PET substrate exceeded most UV-curable adhesives in the market.The contact angle measurements and the SEM micrographs provided effectively support for high bonding strength between silicone-modified formulas and untreated PET substrate.The result of TGA showed that thermal stability of cured films can be enhanced efficiently by means of silicone-modified or secondary moisture cure. |
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