ی وه ٨٩٠٩٠٨٣ ودیع ٣ کار م یھ سا صاد رپ

ش م آزما تات ز پ ل ا ی و پش جام آزما ر ا ٢٢/١/٩١

:هدف

به صورت امولسيونيPVAcينيل استات سنتز پلي و

[1]

:تئوري

Polyvinyl acetate (PVA or PVAc) is a thermoplastic polymer with a chemical formula of (C4H6O2)n. It is normally manufactured by the free radical polymerization of vinyl acetate. The procedure involves the reaction of monomer molecules of vinyl acetate by submerging them into water. This results in the formation of a polyvinyl acetate emulsion that is milky white in color. The emulsion fluid can then instantly be processed as a polyvinyl acetate polymer in products comprising the PVAc as a constituent element.

PVAc is primarily a synthetic resin polymer, which, due its non-polar nature, is insoluble in water, oils, fats, or gasoline. On the other hand, it is soluble in alcohols, ketones, and esters. It has a molar mass of 86.09 grams per mole (g/mol). The ester groups in the structural lattice of polyvinyl acetate render it reactive with alkalis, and lead to the formation of polyvinyl alcohol (PVOH, PVA, or PVAL) and acetic acid (CH3COOH). Boron compounds like borax and boric acid also react with the polymer, under alkaline settings, leading to the formation of a complex borate-slime-precipitate.

Polyvinyl acetate was first discovered by a German scientist Dr. Fritz Klatte in 1912. Since its discovery, it has been employed widely as a binding material, due to its adhesive properties for porous materials like wood and paper. Other than its use as polyvinyl acetate glue, it is also used in paper and textile industry to produce PVA coatings that lend a shiny touch to surfaces. PVAc is commonly used in the manufacture of latex paints, where it helps in forming a tough coating and a supportive film. It is also widely used for the production of

polyvinyl acetate adhesives, which are more commonly known as Elmer's glue, carpenter's glue, or white glue.

Industrial applications of PVAc normally use it in the form of a liquefied emulsion. Polyvinyl acetate polymer exhibits sound resistance to UV rays and oxidation. This renders it an effective polymer with good aging characteristics, yet its water sensitivity can be a problem. This is typically taken care of by formulating it with plasticizers to increase its reliability and stability.

When PVAc is incorporated into emulsion coatings and adhesives, it is normally converted to polyvinyl alcohol first, which is a water-soluble polymer. This is done by means of partial hydrolysis. On a lesser level, it is also used as a protective coating for cheese to render it safe from humidity and fungi.[2]

:نحوه انجام آزمايش

روي هيتر حرارت ميدهيم تا حل 90ºCدرون حمام آب ) آب مقطر 1.5g PVA + 45cc(تهيه امولسي فاير - ۱

)حجم تغيير نکند(شود

درصد و يکبار با آب مقطر شستشو مي ۲ بار با سود ۳ وينيل استات را 12cc(جداسازي بازدارنده از مونومر - ۲

)داخل دکانتور زير هود (مر بدون بازدارنده را اندازه مي گيريم دهيم و بعد از جداسازي حجم مونو

داخل فونل دوم) آب مقطر15cc استات سديم در g 0.05+ پرسولفات آمونيوم g 0.1(تهيه آغازگر - ۳

)همراه مگنت و گذاشتن دو درپوش (بستن دستگاه مبرد - ۴

اضافه کردن مونومر و آغازگر طي - ۵ ) ساعت ۱

دقيقه بماند۱۵ - ۶

)درون بشر آب سرد( سرد ميکنيم 40ºCتا - ۷

تعيين درصد پليمر خشک - ۸

:محاسبات g 44.18= وزن پتري ديش

g 75.28= وزن پتري ديش و التکس

g 45.9= وزن پتري ديش و پليمر خشک

g 31.1= وزن التکس

g 1.72= وزن پليمر خشک

%53.5100latex ofweight

polymerdry ofweight =رصد خشکد

% 5.53= درصد پليمر خشک

بحث و بررسي نتايج

وزن خشک پليمر را مقادير مختلفي Latex-Modified Concretes and Mortarsدر منابع مختلف مثل کتاب

حدود درصد وزني مي باشد که ما اين عدد را۲۰ تا ۱۰براي مصارف مختلف معرفي کرده اما معموالن اين عدد بين

. درصد به دست آورديم۵

پاسخ به سواالت

۱-

۲ –

%53.5100latex ofweight

polymerdry ofweight =درصد خشک

0.934 × 5 = 4.6 g = وزن مونومر وينيل استات= چگالي ×حجم

%4.37100monomer ofweight

polymerdry ofweight = راندمان

۳-

Polymerization of vinyl acetate in bulkand emulsion by gamma irradiation [3] The vinyl acetate polymerization to produce poly(vinyl acetate) was carried out in bulkand emulsion using a 60Co

gamma irradiator Gammacell-220 type. Irradiations were carried out with gamma rays coming from a 60Co irradiator, Gammacell-220 of Atomic Energy of Canada Limited, with a dose rate of 5.25 and 5.30 kGy/h. For the

irradiation of samples a polymerization reactor was used. This reactor has two paths (inlet and outlet), for the circulation of the monomer solution, located at the center of a tube for the introduction of the thermocouple that is

used to control the temperature of the polymerization reaction. Bulk polymerization was carried out with the

pure monomer, which was irradiated for 1 h and 45 min corresponding to a radiation dose of

9.18 kGy. After irradiation the polymer obtained was precipitated with distilled water. The precipitate was washed three times with distilled hot water, for the

elimination of residual monomer. After that, the sample was dried in stove at 140_C for 2 h until constant weight

was reached. In emulsion polymerization, monomers and the

sodium lauryl sulfate surfactant were used, which were irradiated for 34 min corresponding to a radiation dose

of 3.00 kGy. After the irradiation the polymer obtained was precipitated with ethanol and the excess

ethanol was removed. The precipitate was washed three times with distilled hot water, for the elimination of

residual monomer. After that, the sample was dried in stove at 140_C for 2 h, until consistent weight was

reached.

suspension polymerization[4] To obtain high molecular weight (HMW) poly(vinyl acetate) (PVAc) with high conversion and high linearity for a precursor of HMW poly(vinyl alcohol) (PVA), vinyl acetate (VAc) was suspension-poly-merized using a low-

temperature initiator, 2,2′-azobis (2,4-dimethyl-valeronitrile) (ADMVN), and the effects of polymerization conditions on the polymerization behavior and molecular structures of PVAc and PVA prepared by saponifying

PVAc were investigated. On the whole, the experimental results well corres-ponded to the theoretically predicted tendencies. Suspension polymerization was slightly inferior to bulk polymerization in increasing molecular weight of PVA. In contrast, the former was absolutely superior to the latter in increasing conversion of the

polymer, which indicated that the suspension polymerization rate of VAc was faster than the bulk one. These effects could be explained by a kinetic order of ADMVN concentration calculated by initial-rate method and an activation energy difference of polymerization obtained from the Arrhenius plot. Suspension polymerization at

30 °C by adopting ADMVN proved to be successful in obtaining PVA of HMW (number-average degree of polymerization (P n)): (4200–5800) and of high yield (ultimate conversion of VAc into PVAc: 85–95%) with

diminishing heat generated during polymerization. In the case of bulk polymerization of VAc at the same conditions, maximum P n and conversion of 5200–6200 and 20–30% was obtained, respectively. The P n,

lightness, and syndiotacticity were higher with PVA prepared from PVAc polymerized at lower temperatures.

۴-

بسيار کمک ) است که بسيار گرمازا(وجود آب در سيستم به کاهش گرماي ناشي از واکنش بسپارش

.شود کند و بنابراين موجب افزايش سرعت واکنش مي مي

قابليت توليد التکس با ويسکوزيته پايين در اين نوع واکنش وجود دارد.

سرعت اين نوع پليمريزاسيون باالست.

تواند در طول واکنش ثابت ي پليمر وجود دارد، چون متوسط تعداد راديکالها ميقابليت کنترل وزن مولکول

.باشد

است واکنش و محصول به محيط زيست صدمه کمتري از آنجائيکه آب به عنوان محيط واکنش استفاده شده

.زنند مي

است محصول پليمريزاسيون امولسيوني معموالً بدون فرايندهاي ديگر قابل استفاده.

قابليت افزايش وزن مولکولي پليمر همزمان با افزايش سرعت واکنش وجود دارد.

به سرعت بهم زدن و درجه حرارت، سرعت نفوذ منومر، سرعت پليمريزاسيون ، انتقال و درجه پليمريزاسيون

پخش ماده

عوامل خطادر زمان جداسازي مونومر از بازدارنده روي داد اما خطاهاي ديگري مثل خطاي اندازه گيري توزين و بيش

.حرارت دادن نيز بي تاثير نبود

ترين خطا

خطا در ميزان

منابع [1] www.epi.lyckeby-industrial.com [2] www.wisegeek.com/what-is-polyvinyl-acetate.htm

www.ipen.br/biblioteca/2004/09935.pdf [3]

www.springerlink.com/content/lxu4ql4p3nw0ntmp [4]