Study On Aging Behavior And Anti-aging Measures Of Unsaturated Polyester Heat-reflective Coating For Asphalt Pavement

As the heat stability disease of asphalt pavement and urban heat island effect which are caused by high temperature in summer is growing,the asphalt pavement heat reflecting coating which can decrease the temperature of pavement is gradually getting people's attention.The unsaturated heat reflecting coating material made by our own group can effectively reduce the high temperature of asphalt pavement around 10? in summer season.However,the coating may become yellow,brittle because of the polymer material aging,and this can affect its performance and cooling effect.According to the above problem,this paper explores the aging behaviors under the condition of natural aging and artificial accelerated aging and puts forward some measures to improve heat reflecting coating aging performance on the basis of analyzing the mechanism of coating material aging and stabilization.Using the methods of natural aging and artificial accelerated aging to test the aging performance of unsaturated polyester heat reflecting coating.At the same time,this paper sets up relationship between reflectance and cooling effect by observing its surface appearance,chemical structure,tensile strength,reflectivity,cooling effect with the change of the aging time.The outdoor aging research shows that the surface of coating begin to appear bleached and tiny cracking phenomenon after 270 days.The increase of carbonyl content and decrease of carbon carbon double bond content in coating along with the time significantly result from the generation of lots of carboxyl radicals produced by the polymers in coating under the action of light,oxygen,a chain reaction and the fracture of molecular bonds under the high energy ultraviolet.The tensile strength of the coating drops with the aging time,and the speed increases with the amount of solar irradiance accelerating.The tensile strength after 360 days is 77%of the maximum strength at the beginning.The reflectivity and cooling effect of coating appear first slow back quick downtrend with aging time,the reflectivity of heating coating dropped by 22.17%and the cooling value dropped by 6.2? after 360d natural aging.And the solar irradiation is the key factors influencing the coating reflectivity and the cooling effect decay.Reflectance values a 10%drop in temperature values fall about 2.6? after the fitting between coating reflectivity and cooling value.Indoor aging researches shows that the surface roughness of the coating decreases with aging time which performs as the decline of gloss.The content of carbonyl increase with the aging time.The content of carbon-carbon decrease with the aging time.The further crosslinking and curing of coating at the early stage of the aging result in the increase of tensile strength.The degradation at the late stage of the aging can result in the decrease of the tensile strength.The tensile strength after aging is 73.5%of the maximum tensile strength.The reflectivity and cooling effect of coating appear first slow back quick downtrend,the reflectivity of heating coating dropped by 26.4%and the cooling value dropped by 5.5? after 28d artificial accelerated aging.The cooling effect and the reflectivity of the coating appear slowly first and fast afterwards,and a 10%drop in reflectivity can lead to cooling value falling about 2.1? with the linear fitting.To improve the anti-aging properties of the heat reflecting coating,the anti-aging measures of unsaturated polyester resin has been put forward.This paper choses four common light stabilizersUV-531,UV-327,UV-292 and Nano ZnO and analyses their ultraviolet-visible absorption spectrum.Six groups of anti-aging measures are designed.The light transmittance,gloss,resistance to impact strength being were evaluated.Through these experiments,this paper choses the anti-aging measure that UV-573 compositing UV-292 as the best one and the optimal contend of the light stabilizer is 7%.