Andrady A L, Hamid S H, Hu X, Torikai A
Research Triangle Institute, Research Triangle Park, NC 27709, USA.
J Photochem Photobiol B. 1998 Oct;46(1-3):96-103. doi: 10.1016/s1011-1344(98)00188-2.
Synthetic polymers such as plastics, as well as naturally occurring polymer materials such as wood, are extensively used in building construction and other outdoor applications where they are routinely exposed to sunlight. The UV-B content in sunlight is well known to affect adversely the mechanical properties of these materials, limiting their useful life. Presently their outdoor lifetimes depend on the use of photostabilizers in the case of plastics and on protective surface coatings in the case of wood. Any increase in the solar UV-B content due to a partial ozone depletion would therefore tend to decrease the outdoor service life of these materials. It is the synergistic effect of increased UV radiation with other factors such as the temperature that would determine the extent of such reduction in service life. The increased cost associated with such a change would be felt unevenly across the globe. Those developing countries that depend on plastics as a prime material of construction and experience high ambient temperatures are likely to be particularly affected in spite of the relatively small fractional decrease in ozone at those locations. Assessment of the damage to materials, associated with ozone depletion, requires a knowledge of the wavelength dependence as well as the dose-response characteristics of the polymer degradation processes of interest. While the recent literature includes some reliable spectral sensitivity data, little dose-response information has been reported, so it is difficult to make such assessments reliably at the present time. This is particularly true for the naturally occurring materials popularly used in construction applications. To maintain polymers at the same useful lifetime in spite of increased solar UV-B content, the amount of photostabilizers used in the formulations might be increased. This strategy assumes that conventional stabilizers will continue to be effective with the spectrally altered UV-B-enhanced solar radiation. While the present understanding of the degradation chemistry suggests the strategy to have merit, its effectiveness, in an altered solar radiation environment, has not been demonstrated for common polymers. The availability of these data is crucial for reliably estimating the cost of mitigating the increased damage to materials as a result of a possible partial depletion of the ozone layer using this approach.
合成聚合物如塑料，以及天然存在的聚合物材料如木材，广泛用于建筑施工和其他户外应用，在这些应用中它们经常暴露于阳光下。众所周知，阳光中的UV-B含量会对这些材料的机械性能产生不利影响，从而限制其使用寿命。目前，对于塑料来说，其户外使用寿命取决于光稳定剂的使用；对于木材来说，则取决于保护性表面涂层。因此，由于部分臭氧消耗导致的太阳UV-B含量增加往往会缩短这些材料的户外使用寿命。UV辐射增加与温度等其他因素的协同作用将决定使用寿命缩短的程度。与这种变化相关的成本增加在全球范围内的感受并不均衡。那些依赖塑料作为主要建筑材料且环境温度较高的发展中国家，尽管当地臭氧减少的比例相对较小，但可能会受到特别大的影响。评估与臭氧消耗相关的材料损害，需要了解感兴趣的聚合物降解过程的波长依赖性以及剂量响应特性。虽然最近的文献包含了一些可靠的光谱敏感性数据，但很少有剂量响应信息被报道，因此目前很难可靠地进行此类评估。对于建筑应用中广泛使用的天然材料来说尤其如此。为了在太阳UV-B含量增加的情况下使聚合物保持相同的使用寿命，可能会增加配方中使用的光稳定剂的量。该策略假定传统稳定剂在光谱改变的UV-B增强太阳辐射下仍将有效。虽然目前对降解化学的理解表明该策略有可取之处，但其在改变的太阳辐射环境中对常见聚合物的有效性尚未得到证实。这些数据的可用性对于可靠估计使用这种方法减轻由于可能的部分臭氧层消耗而对材料造成的增加损害的成本至关重要。
