Synthesis And UV Irradiation Properties Of PVC Based UV Absorber

Polyvinyl chloride(PVC) is widely used in our daily life as one of the five general resins. It’s popularity come from the characteristics such as wear resistance, corrosion resistance, high strength, easy to process and modified, excellent insulating property and flame retardancy as well as the low price. However, the stability of polyvinyl chloride is poor especially when it exposure to the sun for a long time. Under the effect of ultraviolet, polyvinyl chloride degraded to a different degree, appearing the photo-aging phenomenon accompanied with the performance degradation, resource waste and environmental pollution. 2, 4-dihydroxy diphenyl ketone is a kind of uv absorber, which can defense PVC photo-aging phenomenon effectively. However, 2, 4-dihydroxy diphenyl ketone is a kind of small molecular uv absorber. It will appear the phenomenon of volatile and migration inevitably, which restrict the longevity of the light stability. Therefore, it is significant to make a modification of 2, 4-dihydroxy diphenyl ketone small molecule uv absorber and to improve its service time in polyvinyl chloride.In this paper, the first job was the preapration of PVC based uv absorber PUH with the method of click reaction, and then the characterizations of elemental analysis, nuclear magnetic, FTIR and UV spectrum were also carried out. Secondly, PVC/PUH membranes werre prepared and artificial accelerated aging test was carried out. Yellow index, mass loss and mechanical properties test were employed to study the macroscopic photo-aging phenomenon of polyvinyl chloride and to explore the influence of grafting rate and adding amount. Finally, UV spectrum, FTIR, thermogravimetric, GPC and XPS characterizations were employed to analysis the microstructure during the photo-aging process. The influence of PVC based uv absorber PUH on the photo-aging process of polyvinyl chloride was investugated, and got correspond ing conclusions.1. Firstly, azide group was introduced through the replacement of chlorine atoms in PVC chain with NaN3, then alkynyl was linked to the hydroxyl groups in the No.4 position of 2, 4-dihydroxy diphenyl ketone, finally the PVC based uv absorber PUH with different grafting rate of 3.5%, 9.6% and 29.9% were prepared successfully via click reaction, which bonding alkynyl with azide group together.2.The experimental results of yellow index, mass loss and mechanical properties showed that PUH could reduce the yellow index, mass loss and increase the mechanical properties of the material to a certain extent. Compared with small molecular UV absorber UV-531, the durability of PUH improved significantly. The optimum adding amount and grafting rate of PUH were 0.4 phr and 9.6%, respectively.3. UV spectrum results showed that PUH could inhibit the formation of conjugated double bond with different length especially for n=2-3. The variation of carbonyl index and crosslinking index suggested that PUH could inhibited oxidation reaction and captured the free radicals to some degree. Compared with pure PVC, TG analysis indicated that PUH could improve the thermal stability of material to a certain extent. PUH could reduce the chain rupture reaction, thus reducing the descending degree of number average molecular weight and weight average molecular weight, as well as the rising degree of molecular weight distribution. XPS results also proved that PUH could reduce the oxidation reaction and increase the crosslinking reaction slightly.4. Compared with the widely used small molecular UV absorber UV-531, the light stability effect of PUH enhanced further. The most essential reson ia that t he depletion of small molecule uv absorber caused by the volatile and migration was reduced. The service life of uv absorber increased significantly, so the resistance ability to light degradation become more durable.