《UV及抗氧》.ppt

A clear improvement in UV absorption for polymers透明性大为改性的紫外线吸收剂 Ultra-Violet 紫外线 Why is UV important? 为什么紫外线如此重要？ As the wavelength decreases the energy imparted by the radiation increases. More energy = more chemical reactions – Photo-oxidation, photodegradation 波长越短，射线的能力越强。越多的能量-?越活跃的化学反应—光氧化、光降解。 Each photon of UV light at 250 nm has 4 times more energy than Infrared at 1000 nm 每一个250 nm 的UV光子的能量相当于4个1000 nm红外光光子的能量。 Vacuum UV is stopped by air and UVC is blocked by the ozone layer, but UVB and UVA from the sun reach the earths surface. UVB is more damaging but there is less of it than the UVA 太空射线被大气阻隔了，UVC也被臭氧层吸收了，但UVB和UVA可以到达地球表面。UVB的破坏性比UVA强，但UVB也较UVA少。 UV exposure at earth’s surfaceUV 在地球表面的分布 Why is UV important to Plastics?为什么UV对塑料如此重要？ Damage to the packaging 对包装材料的破坏 Degradation (chain scission, cross-linking and oxidation) 降解（ 链的断裂，交联和氧化） loss of mechanical properties leading to failure of package integrity 丧失了机械性能从而失去了包装的完整性 Change in colour: yellowing or fading颜色的改变：变黄 或 褪色 Generation of “off taste and odour” 产生异味 Print fading 印刷的图案褪色 Damage to the contents of the package对包装内容物的破坏 Loss of Vitamin content in fruit juice and milk 果汁和牛奶中维他命的流失 Accelerated oxidation of fats – rancidity 加速脂肪的氧化-?恶臭 Colour fading in food, personal care and home products 食品，个人护理品，及家居用品等的褪色 Strategies to reduce the effects of UV减少UV影响的方法（1） UV stabilisers 光稳定剂 Work in a similar manner to anti-oxidants by interrupting the breakdown pathway of the substrate material 工作机理和抗氧剂类似，即通过阻断基材分子链的断裂（反应） Most commonly used are Hindered Amine Light Stabilisers (HALS) 最常用的就是 受阻胺类光稳定剂（HALS) Will only protect the packaging material to which they are added 只保护添加了这类助剂的包装材料 Strategies to reduce the effects of UV减少UV影响的方法（2） UV absorbers 紫外线吸收剂 Absorb or scatter the UV radiation reducing its penetration into the material 吸收或散射UV光，减少UV穿透材料 Two main types 2个主要类型 Organic usually aryl compounds 有机类---通常是芳基化合物 Ultra-fine particle size me