Copolyesters

Mixed dicarboxylic acids are usually used to form copolyesters. For instance, terephthalic and isophthalic acids are reacted together with 1,4-dimethylol cyclohexane to form copolyester. The product is amor- phous and transparent. Another copolyester is manufactured from terephthalic, isophthalic, and an aliphatic dicarboxylic acid like adipic with either 1,4 butanediol or 1,6-hexanediol. The aliphatic dicarboxylic acid is used in minor quantities. Many such copolyesters are used as high-strength adhesives. In addition, there are thermoplastic polyester elastomers. These are produced by equilibrium melt transesterification of dimethyl terephthalate, 1,4-butanediol, and a poly(tetramethylene ether) glycol (molecular weight about 1,000). Because equilibrium conditions exist in the melt, the products are random copolymers:

Wholly aromatic polyesters are produced for high temperature applications. The materials must also have good abrasion resistance. One such commercial polyester is prepared from p hydroxybenzoic acid:

Another one is a copolyester prepared from p-hydroxybenzoic acid, p,p0-biphenol, and terephthalic or isophthalic acids:

The above shown polyester does not melt and decomposes at 550C. Turner et al. [38] reported preparation of triptysene containing polyesters. These polyesters were illustrated as follows:

where x ¼ 2,4, or 6. The polyester was prepared by melt-phase synthesis by a transesterification reaction. Higher thermal stability was claimed for the polyesters containing triptysene than the analogous polyesters without it. The properties of various polyesters were summarized by Wilfong [15]. Table 7.1 presents Tm and Tg values of some polyesters based on information from Wilfong and other sources in the literature. Among new methods of forming polyesters is a preparation of completely aromatic polyesters by direct condensation of hydroxyaromatic acids (like hydroxybenzoic) with the aid of triphenylpho sphorous compounds or dichlorophenylphosphine [38]:

Hexachlorotriphosphatriazine can also be used to attain direct polycondensations of hydroxybenzoic acid [43].

اخر الاخبار

اخبار العتبة العباسية المقدسة

بيان صادر عن العتبة العباسية المقدسة

قسم التطوير يقيم دورة تدريبية عن الهندسة النفسية لملاكاته

تضررت في الانتفاضة الشعبانية.. الكشف عن قطع تاريخية من الإيوان الذهبي لمرقد أبي الفضل العباس (عليه السلام)

قسم الصناعات ينهي أعمال صيانة منظومة التهوية في مجمع أبي الفضل العباس (عليه السلام)

المزيد

الآخبار الصحية

عادات يومية تدمر قلبك بصمت.. خبراء يطلقون التحذير

خبراء تغذية يكشفون "أفضل وقت لتناول الإفطار"

أطعمة تزيد فرص وفاة مرضى السرطان 60 بالمئة.. ما هي؟

اختبار ثوري جديد يكشف مبكرا عن سرطان البنكرياس

المزيد

الآخبار التكنلوجية

الذكور أم الإناث؟ دراسة "تنسف الشائع" بشأن التوحد

خبير يكشف عن اقتراب العلماء من فك شفرات "لغات الحيوانات" !

دراسة تدفعك لشراء ساعة ذكية "فورا".. هذا ما تقوله عن قلبك

علماء حاصلون على "نوبل": الذكاء الاصطناعي لن يستبدل الإنسان

المزيد

مواضيع ذات صلة

Linear Unsaturated Polyesters

Synthetic Methods

Linear Saturated Polyesters

Techniques of Polymer Preparation

Ring Formation in Step-Growth Polymerizations

Kinetic Considerations

Reactions of Functional Groups

Poly (vinyl alcohol) and Poly (vinyl acetal) s

Poly (vinyl acetate)

Poly (vinylidine chloride)

Copolymers of Vinyl Chloride

Poly (vinyl chloride)