应力作用下聚氯乙烯涂层膜结构材料的光氧老化性能研究

发布时间：2018-03-14 15:43

本文选题：PVC涂层膜结构材料　切入点：人工加速老化　出处：《东华大学》2015年硕士论文　论文类型：学位论文

【摘要】：随着聚氯乙烯（PVC）涂层膜结构材料的不断发展，因其空间形式独特、价格低廉、能源损耗低、使用性能优良等特点，现已被广泛应用于展览、体育、交通、休闲等建筑中。国外学者研究发现，PVC涂层膜结构材料在户外使用条件下易受阳光中紫外线的作用而发生老化，且外界机械应力的作用也会引起材料内部物理、化学结构发生变化，从而改变材料的光氧老化速度、破坏材料的强力、缩短材料的老化时间，最终导致膜结构材料失去使用性能。因此，有必要对应力作用下PVC涂层膜结构材料的老化性能进行研究。本课题采用了人工加速老化和大气自然老化两种试验方法，研究了不同应力作用下PVC涂层膜结构材料的光氧老化性能。本课题分别在无应力（0%）以及5%、10%、20%三种应力载荷作用下，采用人工加速老化和大气自然老化方法对老化试样进行了光氧老化试验。并对老化试样进行了表观颜色（黄度指数、白度值）、力学性能（断裂强力、断裂伸长）等宏观检测，对试样整个老化过程中性能的变化有了较整体的了解。同时也对老化试样进行了扫描电镜（SEM）、傅里叶变换红外光谱（FTIR）等微观检测。既研究了不同应力作用下膜结构材料的光氧老化性能，又比较了不同应力作用下人工加速老化和大气自然老化之间的相关性。研究发现，随着老化时间的增加，黄度指数逐渐增加，白度值逐渐下降，且应力载荷水平越大，黄度指数增加的越多，白度值下降的也越多，即老化程度越大。结合扫描电镜观察可知，随着老化时间和应力载荷作用的增加，试样涂层表面龟裂现象愈发明显，又在人工加速老化试验中，5%应力作用下老化达到1000h时，PVC涂层表面就出现了剥离现象，这更加说明应力作用加速了表面涂层的开裂。在力学性能方面，无论人工加速老化还是大气自然老化，不同应力作用下断裂强力保持率和断裂伸长保持率变化都不是很显著，而表观颜色和表面形态变化却相当显著，这说明应力作用下PVC涂层膜结构材料的老化首先发生在表面PVC涂层，其次为基布。红外光谱分析表明，不同应力作用下PVC涂层膜结构材料的光氧老化机理没有发生变化。由于人工加速老化方法可以缩短老化试验周期，但人工加速老化得到的老化试验结果与大气自然老化的结果是否一致呢？为此，我们进行了应力作用下PVC涂层膜结构材料人工加速老化和大气自然老化试验结果之间的相关性分析。分析发现，两种老化形式下断裂强力保持率、断裂伸长保持率、羰基指数的变化趋势基本一致，但在累积紫外辐照能相同条件下，老化性能存在一定的差异，即不符合互易定律，从而验证了互易定律的失效性。然而两种老化形式白度值的变化差异最明显，即互易定律对此不适用，由此以白度值为例建立了人工加速老化与大气自然老化之间的相关性。Schwarzschild定律是在互易定律的基础上引入了常数p，即Ipt常数（当紫外辐照强度I的p次方与老化时间t的乘积一定时，，材料的光氧老化效果是等效的）。试验发现：在两种老化形式下,当p=0.87时,人工加速老化和大气自然老化之间有较好的相关性。然后根据Schwarzschild定律对两种老化形式下试样的白度值进行拟合并进行修正,再对修正后的白度值进行了线性拟合,最终得到试样白度值与紫外辐照强度以及老化时间之间的关系方程：y=78.23-0.23x式中,x=I0.87t,I为紫外辐照强度,t为老化时间。上述方程反映了拟合修正后白度值与紫外辐照强度以及老化时间的关系,通过方程可以看出,当p=0.87时,应力作用下PVC涂层膜结构材料的人工加速老化与大气自然老化间具有较好的相关性。
[Abstract]:With the continuous development of polyvinyl chloride (PVC) coated membrane material, because of its unique space form, low cost, low energy consumption, the use of excellent performance characteristics, has been widely used in the exhibition, sports, traffic, leisure and other buildings. Foreign researchers found that the PVC coated membrane material used in the open air condition by ultraviolet light in sunlight and effect of aging, and the effect of external mechanical stress can also cause physical material, chemical structure changes, thus changing the aging speed of the material, the fracture strength, shorten the aging time of the material, resulting in membrane structure lose performance. Therefore, it is necessary to study the aging performance of PVC coated membrane material under different loads. This paper adopts two kinds of test methods of natural aging and artificial accelerated aging atmosphere, studied the stress under the action of PVC coating The optical oxygen aging properties of the film structure material.
This paper respectively in non stress (0%), 5%, 10%, 20% and three kinds of effects of stress load, using artificial accelerated aging and natural aging methods of atmospheric photooxidation aging test on aging and the aging of specimens. The specimens were apparent color (yellow index, whiteness, mechanical) properties (tensile strength, elongation at break) macro detection, change of the whole sample in the process of aging performance have a more overall understanding. At the same time were analyzed by scanning electron microscope (SEM), the aging of Fourier transform infrared spectroscopy (FTIR) micro detection. Not only studies the different light aging properties of membrane structure the material under the action of stress, and compare the different aging and natural aging of the correlation between the atmosphere accelerated under the action of force.
The study found that with the increase of aging time, the yellowness index increased gradually, the whiteness values decreased gradually, and the stress load level increases, the yellowness index increased, whiteness values decreased more and more, the aging degree is greater. Observation with scanning electron microscope, with the aging time and increase the role of force load, specimen coating surface cracking phenomenon more obvious, and in the accelerated aging test, 5% stress aging at 1000h PVC coating surface appeared peeling phenomenon, which further indicates that stress accelerated the cracking of surface coatings. In terms of mechanical properties, both artificial accelerated aging or atmospheric ageing under different stresses, breaking strength and breaking elongation rate changes are not very significant, and the apparent change of color and surface morphology is quite significant, indicating that PVC coated membrane material under the action of force The aging process first occurred on the surface PVC coating, followed by the base cloth. The infrared spectrum analysis showed that the mechanism of photooxidative aging of PVC coated membrane structure did not change under different stress.
Because the artificial accelerated aging method can shorten the aging period, but accelerated aging aging test results obtained with atmospheric ageing results are consistent? Therefore, we analyzed the correlation between the stress of PVC coated membrane material of artificial accelerated aging and atmospheric ageing test results. Analysis showed that the two kinds of aging under the form of breaking strength retention rate, breaking elongation, the change trend of carbonyl index is consistent, but when the cumulative UV radiation energy under the same conditions, there are some differences between the aging performance, that is not in conformity with the law of reciprocity, which verified the failure law of reciprocity. However, two aging changes form white value difference the most obvious, namely the law of reciprocity are not applicable, the accelerated aging.Schwarzschild correlation between aging and natural atmosphere of the establishment as an example to white value The law is a constant P is introduced based on the reciprocity law, namely Ipt (product of P square constant when ultraviolet irradiation intensity I and t aging time when light oxygen material aging effect is equivalent). Experiment results showed that: in the two kinds of aging form, when p=0.87, the accelerated aging and between atmospheric ageing have good correlation. Then according to the Schwarzschild law of whiteness of two kinds of aging form values of samples were fitted with modified, the whiteness of the corrected values are linear fitting, finally obtained the relationship between the whiteness value and ultraviolet irradiation intensity and aging time. X=I0.87t y=78.23-0.23x, I, UV radiation intensity, t as the aging time.
The above equation reflects the relationship between the corrected whiteness value and the UV irradiation intensity and aging time. It can be seen from the equation that when p=0.87 is applied, the accelerated aging of PVC coated membrane structure material has good correlation with the natural weathering.

【学位授予单位】：东华大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TS106;TB33

【参考文献】