丙烯腈與醋酸乙烯共聚物之溶解參數，紅外線光譜組成分析及熔融流動性

Solubility Parameter, IR Spoctrometric Composition Analysis and Flow Testing of Acrylonitrile and Vinyl Acetate Copolymers

吳澄清(Cheng-Ching Wu) ； 謝文淇(Wen-Chyi Hsieh)

《化學》 63年3期 (1974/09) Pp. 85-92

https://doi.org/10.6623/chem.1974016

摘要

丙烯腈與醋酸乙烯共聚合物各組成之溶解參數可用混濁滴定法測定及由Small之經驗式求得理論預測值。此兩法結果相近。但前法所得之溶解參數比後法所得者高些。此點可用定性解釋之。丙烯腈與醋酸乙烯共聚合物之溶解參數為其組成之函數，其各組成之溶解參數理論預測值可表為δ=(720+571k)/(74.229+51.04k)其中δ為溶解參數，k為共聚物中丙烯腈對醋酸乙烯之莫耳比。丙烯腈與醋酸乙烯共聚物之紅外線定量組成分析可表為(A_(1725)/A_(2225))=19.682-0.1986X其中A_(1725)及A_(2225)分別為在波數(wave number)1725cm^(-1)及2225cm^(-1)處之吸收。X為共聚物中丙烯腈之莫耳百分率。隨著丙烯腈在共聚物中之莫耳百分率增加，流動溫度及開始流動溫度均增加。於丙烯腈莫耳百分率為85%以上時，前二溫度均急速上升。溫度達到某聚合物之玻璃轉移溫度(glass transition temperature, Tg)時，外界所供給之熱能恰能克服分子主鏈小節(molecular main chain segment)運動障礙。又此種運動障礙常由聚合物分子之凝集能(cohesive energy)所控制，因而凝集能成為決定Tg之重要因素。但諸如分子幾何形狀、立體阻礙等因素有時也扮演著重要角色。因溶解參數(solubility parameter)被定義為凝集能密度之平方根^1，故溶解參數亦為決定Tg之主要因素。Boyer^2，Tobolsky^3, Hayes^4等均曾分別指出具有高溶解參數之聚合物其Tg亦高。聚合物為不揮發性物質。不似一般液體溶劑可藉測其蒸發熱決定凝集能密度進而求其溶解參數。通常測定聚合物溶解參數之方法有Small法^5，極限黏度法^6 (intrinsic viscosity method)，膨潤法^6(swelling method)及新發展之混濁滴定法^(7,8)(turbidimetric titration method)等。考前人用Small法時，聚合物體積項是根據實驗結果。本文亦採用Small法求聚合物各組成之溶解參數理論值，唯聚合物體積是根據Sewell^9所表列各原子及構造對聚物體積之加成性而得。如此所得之理論值完全不涉及實驗，故甚為簡便。另以混濁滴定法測定共聚物各組成之溶解參數實驗值，並比較兩者結果。丙烯腈與醋酸乙烯共聚合物之紅外線吸收光譜中有四個特性吸收帶^(10)(characteristic absorption band)，即波數為2225cm^(-1), 1725cm^(-1),1360cm^(-1)及1220cm^(-1)；分別由C=N, C=O, CH_3及C-O鍵之伸縮振動(stretching vibration)所引起之吸收。特性吸收強度除與該組成含量有關外，亦與薄膜厚度成正比^(11)。為消除薄膜厚度因素而採吸收比與丙烯腈在共聚合物中莫耳百分率之關係圖形。

並列摘要

The Solubility parameters of AN-VAc copolymers have been determined by the turbidimetric titration method and predicted by Small's emperical eqnation considering atomic and structural contributions tabulated by Sewell. The results of both methods agree well, but the solubility parameters determined by the former method are higher than the latter one. A qualitative explanation of these is suggested. The predicted parameters of AN-VAc copolymers are function of copolymer composition and can be expressed by the formula δ= (720+571 K)/(74.229+5 1.04 K) whereδis solubility parameter and k is the molar ratio of AN to VAc in the copolymer. The quantiative relationship of IR spectrometric analysis of AN-VAc copolymer ＂map can be expressed by (Al1725/A2225) = 19.683- 0.1986 X where A1725 and A2225 are the absorbance at 1725 cm^(-1) and 2225 cm^(-1) respectively. X is the ＂molar percentage of AN in the copolymers. Temperature of flow and tewperature of beginning flow increase with AN increasing in the copolymer. As molar percentage of AN in the copolymer is above 85%, the increasing of both temperatures are very quickly.