Poly (vinyl acetate)

Vinyl acetate monomer can be prepared by reacting acetylene with acetic acid:

The reaction can be carried out in a liquid or in a vapor phase. A liquid phase reaction requires 75–80C temperatures and a mercuric sulfate catalyst. The acetylene gas is bubbled through glacial acetic acid and acetic anhydride. Vapor phase reactions are carried out at 210–250C.

Typical catalysts are cadmium acetate or zinc acetate. There are other routes to vinyl acetate as well, based on ethylene. Commercially, poly (vinyl acetate) is formed in bulk, solution, emulsion, and suspension polymerizations by free-radical mechanism. In such polymerizations, chain transferring to the polymer may be as high as 30%. The transfer can be to a polymer backbone through abstraction of a tertiary hydrogen:

It can also take place to the methyl proton of the acetate group:

The polymer has a head to tail structure and is highly branched. It is quite brittle and exhibits cold f low. This makes it useless as a structural plastic. It is, however, quite useful as a coating material and as an adhesive for wood. The polymer is soluble in a wide range of solvents and swells and softens upon prolonged immersion in water. At higher temperatures or at extended exposures to temperatures above 70C, the material loses acetic acid. A number of copolymers are known where vinyl acetate is the major component. In coatings, vinyl acetate is often used in copolymers with alkyl acrylates (line 2-ethylhexyl acrylate) or with esters of maleic or fumaric acids. Such copolymers typically contain 50–20% by weight of the comonomer and are usually formed by emulsion polymerization in batch processes. They are used extensively as vehicles for emulsion paints. Shaver and coworkers [319] investigated the mechanism of bis(imino)pyridine ligand framework for transition metal systems-mediated polymerization of vinyl acetate. Initiation using azobisisobu-tyronitrile at 120C results in excellent control over poly (vinyl acetate) molecular weights and polymer dispersities. The reaction yields vanadium-terminated polymer chains which can be readily converted to both proton-terminated poly (vinyl acetate) or poly(vinyl alcohol). Irreversible halogen transfer from the parent complex to a radical derived from azobisisobutyr onitrile generates the active species.

اخر الاخبار

اخبار العتبة العباسية المقدسة

خدمات صحية متكاملة قدَّمها قسم الشؤون الطبية لزائري ليلة النصف من شعبان في مجمَّع الشيخ الكليني

خدمات صحية متكاملة قدَّمها قسم الشؤون الطبية لزائري ليلة النصف من شعبان في مجمَّع الشيخ الكليني

في ذكرى ولادة الإمام المهدي (عجّل الله فرجه).. قسم الشؤون الفكرية يصدر عددًا خاصًّا من مجلة العقيدة

للاطّلاع على خدماته المقدمة للزائرين مركز السيد جعفر الحلي يستقبل المدير العام لمديرية العمليات والخدمات الطبية في وزارة الصحة

المزيد

الآخبار الصحية

دراسة تكشف "سر الوسادة".. ودورها في حماية البصر

بالأشعة تحت الحمراء.. "ثورة علمية" في علاج اللاعبين

مشروب أحمر يخفض ضغط الدم "بشكل ملحوظ"

الصحة العالمية تكشف حقيقة انتشار فيروس نيباه خارج الهند

المزيد

الآخبار التكنلوجية

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

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

وانغ هو: القمة العالمية للعلماء تجسد تقدير الإمارات للعلم

رئيس رابطة كبار العلماء يعلن تأسيس مقر في الإمارات

المزيد

مواضيع ذات صلة

Kinetic Considerations

Reactions of Functional Groups

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

Poly (vinylidine chloride)

Copolymers of Vinyl Chloride

Poly (vinyl chloride)

Miscellaneous Fluorine Containing Chain-Growth Polymers

Copolymers of Fluoroolefins

Poly chloro tri fluoro ethylene

Poly tetra fluoro ethylene

Polyacrylamide, Poly(acrylic acid), and Poly(methacrylic acid)

Acrylonitrile and Methacrylonitrile Polymers