Study On Bonding Properties Of PVC Wood Plastic Composites

The thesis described bonding properties of glued blocks of PVC wood plastic composites (WPC) with epoxy resin adhesive and J-39 acrylic adhesive. The results showed that compressing shear strength of glued blocks with epoxy resin adhesive was the best, dry compressing shear strength of glued blocks with J-39 acrylic adhesive was the second.To compared with WPC materials itself, compressing shear strengths of glued blocks with epoxy adhesives and J-39 acrylic adhesive can reach the material itself 72% and 57%. The bonding effect of two kinds of adhesive was obvious for PVC WPC; Increaseing curing time also had affect on the shear strength of epoxy resin adhesive, as the spicemans lied in room for long, the value was more than up to 8.07MPa. Curing time had a significant effect on the bonding strength of glued blocks with epoxy resin.After surface treatment with acetone, compressing shear strengths of glued blocks with J-39 acrylic adhesive was increased greatly. Compressing shear strength of the glued specimen with J-39 acrylic adhesive increased from 5.97 MPa up to 7.14 MPa, compressing shear strength increased 19.6%. As for the epoxy adhesive, there was little difference before and after acetone surface treatment.Aging test including boiled aging and UV aging were also tested. Through comparing the compressing shear strength before and after aging test, it is found that the aging properties of epoxy resin adhesive was better than J-39 Acrylic adhesive. Observed bonding interface of epoxy resin adhesive after the aging by SEM, it was found that adhesive layer were changed, but combination degree between the epoxy adhesive and PVC WPC was unchanged.Surface free energy of PVC WPC was 40.3mN/m calculated by the contact angle methods, and it was lower than the wood. This was why that PVC WPC was difficult to adhesive. The penetration of different adhesive into PVC WPC was studied by SEM. By observing the bonding interface, it could found that adhesive penetrate into the holes and pores, and this could form strong mechanical interlocking, which increased bonding strength of bonding joints. We could see by SEM that the combination between interface was high close, there was no gap between the interface, adhesives and materials is very good fusion.The bonding interface of glued blocks of PVC WPC was studied by FTIR. It was found that epoxy adhesive formed the C=O stretching vibration, ester group was formed after the curing reaction. C=O stretching vibration peak which was caused by esterification of acrylic ester and hydroxyl from materials could be seen in FTIR of bonded blocks with J-39 Acrylic adhesive.The dynamic mechanical properties of PVC WPC were studied by dynamic mechanical thermal analysis system(DMA). The results showed that using DMA determined the bonding effect of temperature for curing reaction. After bonding the PVC WPC, the storage modulus decreased with increasing frequency, the strength after the bonding was not strong. DMA tests in the initial phase of thermodynamics, material storage modulus was higher, but with increasing temperature, their storage modulus decreases rapidly. Therefore, the temperature had a great effect on storage modulus; at the same temperature, the storage modulus of glued blocks was lower than that of PVC WPC. Loss modulus (E") and loss tangent of glued blocks and PVC WPC were increased rapidly with the increase of test temperature; glass transition temperature of glued blocks with the epoxy adhesive and J-39 Acrylic adhesive were 58℃,84℃.