- 作者: 李敏達
- 作者服務機構: 國立臺灣大學化工系
- 中文摘要: 利用浸漬法或接枝法,將光劣化促進劑引入聚合體中,由抗張強度,伸長率與平均分子量等性質之變化,研討光氧化劣化作用。由實驗結果得知,酮與醛等對於聚合體之劣化速率有顯著之促進效果“在所試10種碳化合物中,以二苯甲酮與苯乙酮之效果為最佳。聚氯乙烯薄片經5%二苯甲酮一丙酮溶液浸漬處理者,以高壓汞燈照射20小時,即變成硬脆,伸長率降至零,稍加力捏和則破碎,其劣化速度高出未處理者約5倍。浸漬液中添加氯化鐵時,光劣化促進效果更為顯著。在照射之初期,分子量稍見上昇,表示主鏈之交聯與斷裂同時發生“酮類對於聚苯乙烯之光劣化促進作用,大致與聚氯乙烯相似,惟對於聚乙烯則效果較低。聚苯乙烯上接枝碳基者,對於光劣化作用亦有顯著之效果。由凝膠體生成分數得知,聚氯乙烯與接枝聚苯乙烯在劣化過程中,主鏈斷裂之或然率稍高於交聯之或然率。聚氯乙烯布在自然環境下之光劣化亦加以試驗。 近年來隨著塑膠材料之大量利用,其廢物所引起之公害日趨嚴重。都市垃圾中塑膠廢棄物所佔比率達數%,除部份可回收再利用外,在焚燒處理時,由於發生有毒氣體及高熱量,不但使焚燒爐發生局部之腐蝕,且能引起空氣之污染“此種塑膠廢棄物若不加以妥善之處理,在不久之將來勢必在聚合體工業上之發展上成為一大阻礙。 塑膠廢棄物之處理,現今所研究之方法有(1)加以焚燒處理而利用其所生之熱能,(2)粉碎後用於鋪路或填平土地,(3)經加熱變形,成形後再度利用,(4)分解後回收低分子量單體或液態物質等。年來由於全世界石油需要量之急激增加與資源之枯竭,塑膠廢棄物之回收處理與有效再利用,逐漸受人重視“目前所用之分解回收法,大都以熱分解為主,其裝置有接觸式熱分解裝置,流動層熱分解裝置,熔解浴等,所需設備較為龐大。利用光氧化作用,以分解聚合體亦為一值得考慮之方法,其效能,除可回收低分子物質外,尚能防止廢棄物焚燒處理時之二次公害。例如,塑膠廢棄物在太陽光之曝露下,若能分解而成為粉末,則可均勻分散於垃圾中,焚燒時可避免爐壁之局部過熱,所生有毒氣體亦易被吸附於無機系垃圾中。 聚合體之光氧化劣化作用研究,已屢見於文獻。 Stephensen等(1,2)將數種塑膠加以紫外線照射後,研討其物理性質,分子量之變化及主鏈之交聯與裂開作用。Osborn(3)由聚對苯二甲酸乙二酯(polyethylene terephthalate, PET)之光氧化反應,討論聚合體鏈之裂開率與能量吸收率之關係,並研討光化學過程之總量子收率。Marcotte,Campbell, Cleaveland 與Turner (4)等曾經研究PET在真空下,受單色光照射時 ,所起之化學變化“Day與Wiles (5)使用兩種不同之光源照射PET,由紅外線吸收及螢光發射光譜之測定,確定PET劣化過程中表面反應之機構。 由處理塑膠廢棄物之觀點,研究製造光氧化分解性聚合體,近數年來逐漸受入重視。
- 英文摘要: The photooxidative degradation of polymeric materials by ultraviolet light inthe presence of some promoters were studied for the purpose of looking for anapproach to make plastic more degradable. The extent of degradation was estima-ted by measuring the changes in tensile strenght at rupture, elongation, and numberaverage molecular weight of polymers. Ten different ketones and aldehydes weretested as promoter. The results showed that the rate of degradation is increased byimmersing the material into a solution of promoter before irradiation. Benzophenoneand acetophenone are found to be the effective promoter. The rates of degradationof PVC films treated with benzophenone or acetophenone are about 3 to 5 timeshigher than those of untreated films. Addition of ferric chloride to immersingsolution causes higher degradation rate. The molecular weight measurements showa slight increase in molecular weight at the initial stage of irradiation, indicatingthe occurrence of crosslinking between polymer chains other than scission. Theeffects of promoter on polystyrene are similar to those on polyvinyl chloride, whilein polyethylene the effects are relatively small·Graft of carbonyl group onto poly-styrene is another method for accelerating degradation rate. The scission-to-cross-linking ratios were determined for some materials including PVC film treated withbenzophenone and grafted PS.The degradation of commercial PVC sheet by expo-sure to the sun was also tested.
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