Novel flat panel reactor for monitoring photodegradation
Novel flat panel reactor for monitoring photodegradation
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用于监测光降解的新型平板反应器
DOI：
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发表时间：
2004
期刊：
影响因子：
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通讯作者：
David A. Worsley
中科院分区：
文献类型：
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作者：
A. J. Robinson;J. Searle;David A. Worsley
本文介绍了一种封闭的系统，该系统采用FTIR连续监测气相和一种新颖的气室，用于有机涂层平板的紫外辐照。这已被用来探测在UVA照射下的TiO 2着色聚合物膜的光催化降解的各个方面。平板单元由一块铝加工而成，专门设计用于最大限度地减少死体积，实现快速气体混合，并适用于研究尺寸达220 × 100 mm的材料平板试样。该单元在其底部进料中包含气体输入和输出通道，并且通过以这样的方式钻出的小钻孔进料，以使对单元内容物的穷举效果最大化。为了证明该设计的有效性，报道了TiO 2颜料光活性对使用商业光稳定TiO 2等级的商业丙烯酸乳胶漆的降解速率的影响。在使用这种新的反应堆配置的测试中，已经可以关联在数千小时的氙弧暴露期间获得的光活性，这是目前可用的最可靠的测试。该测试单元还用于评估其他涂层组分。使用未增塑的PVC膜，我们发现，当简单分子UV吸收剂（2羟基二苯甲酮）以高达1.5%/100树脂（PHR）的水平加入时，光生CO2的速率福尔斯下降高达40%。除此之外，光活性几乎没有进一步降低。最后，测试单元已被用来调查的影响，二氧化钛负载量的CO2从辐照未增塑PVC膜着色与0-70 PHR二氧化钛的演变率。光降解的初始速率（超过100分钟）遵循线性趋势，以增加CO2的释放速率高达50 PHR TiO 2。在产生1.8 mmol m-2的CO2后，存在向二级速率的过渡，这表明在设定量的降解后，反应速率发生变化。该速率仍然与TiO 2的浓度成比例。这可能是由于酸催化和在辐照表面中产生孔隙的组合，后者使更多的氧气进入辐照的TiO 2。
A closed system incorporating FTIR continuous monitoring of the gas phase and a novel gas cell for the UV irradiation of flat panels of organic coatings is described. This has been used to probe various aspects of the photocatalysed degradation of TiO2 pigmented polymer films under UVA illumination. The flat panel cell is machined from a single block of aluminium and is specifically designed to minimise dead volumes, enable rapid gas mixing and be suitable for the investigation of flat coupons of material up to 220 × 100 mm in size. The cell incorporates a gas input and output channel in its base feeding and fed by small bore holes drilled in such a way as to maximise the exhaustive effects on the contents of the cell. To demonstrate the effectiveness of the design the effect of TiO2 pigment photoactivity on the rates of degradation of a commercial acrylic emulsion paint using commercial photostable TiO2 grades is reported. In testing using this new reactor configuration it has been possible to correlate photoactivities obtained over periods of several thousand hours Xenon Arc exposure, which is the most reliable test currently available. The test cell has also been used to evaluate other coating components. Using unplasticised PVC films we have found that the rate of photogenerated CO2 falls by up to 40% when a simple molecular UV absorber (2 hydroxybenzophenone) is added at levels of up to levels of 1.5% per hundred resin (PHR). Beyond this there is little further reduction in photoactivity. Finally the test cell has been used to investigate the effects of TiO2 loading on the rates of CO2 evolution from irradiated unplasticised PVC films pigmented with 0–70 PHR TiO2. The initial rate of photodegradation (over 100 min) follows a linear trend to increased CO2 evolution rates up to 50 PHR TiO2. There is a transition to a secondary rate after the production of 1.8 mmol m-2 of CO2 suggesting that after a set amount of degradation there is a change in the reaction rate. This rate is still proportional to the concentration of TiO2. It is likely that this is due to a combination of acid catalysis and the generation of porosity in the irradiated surface, the latter enabling greater oxygen access to the irradiated TiO2.