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Poly(viny1 acetate) and its Derivatives

Poly(viny1 acetate) and its Derivatives

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CHrCH



+



CH,COOH



-



Poly(viny1 acetate) 387



CH,=CH



I



- 118 kJ/mole



OOC .CH,



CH,=CH



I



+



CH,COOH



CH, . COO



OOC . CH,

CH, . COO



\



CH .CH,



/



Figure 14.1



In a typical system the reaction vessel is at 75-80°C and the vinyl acetate

formed is swept out into a condenser at 72-74°C by means of circulating excess

acetylene. This prevents distillation of higher boiling components but allows the

vinyl acetate and acetylene through. The former is separated out by cooling and

the acetylene recycled.

Vapour phase synthesis may be carried out by passing a mixture of acetylene

and acetic acid through a reaction tube at 210-215°C. Typical catalysts for this

reaction are cadmium acetate, zinc acetate and zinc silicate. The monomer in

each of the above mentioned processes is purified by distillation.

Purified monomer is usually inhibited before shipment by such materials as

copper resinate, diphenylamine or hydroquinone, which are generally removed

before polymerisation. The monomer is a sweet-smelling liquid partially miscible

with water and with the following properties: boiling point at 760mmHg,

72.5"C; specific gravity at 20"C, 0.934; refractive index nD20, 1.395; vapour

pressure at 20°C 90mmHg.

In 1953 the Celanese Corporation of America introduced a route for the

production of vinyl acetate from light petroleum gases. This involved the

oxidation of butane which yields such products as acetic acid and acetone. Two

derivatives of these products are acetic anhydride and acetaldehyde, which then

react together to give ethylidene diacetate (Figure 14.2.)



OC-CH,



OOC . CH,



Figure 14.2



Exposure of the ethylidene diacetate to an aromatic sulphonic acid in the

presence of five times its weight of acetic anhydride as diluent at 136°C will

yield the following mixture: 40% vinyl acetate; 28% acetic acid; 20% acetic

anhydride; 4% ethylidene diacetate; 8% acetaldehyde.

The latter four products may all be reused after separation.

In recent years vinyl acetate has been prepared in large quantities by oxidation

of ethylene. If ethylene is passed into a solution of palladium chloride in acetic

acid containing sodium acetate, then vinyl acetate, ethylene diacetate and

acetaldehyde are produced, the vinyl acetate being obtained in good yields by the

reaction shown in Figure 14.3



388 Poly(viny1 acetate) and its Derivatives

CH,=CH,



-



+



+



2CH,COONa



PdC1,



CH, COOH



CH,= CH



I



+



Pd



+



2NaC1



+



CH, COOH



OOC . CH,

Figure 14.3



The ethylene oxidation process can be carried out in either a liquid or a vapour

phase but the latter method is often preferred because it avoids corrosion

problems and the use of solvents.

A one-stage process for producing vinyl acetate directly from ethylene has also

been disclosed. In this process ethylene is passed through a substantially

anhydrous suspension or solution of acetic acid containing cupric chloride and

copper or sodium acetate together with a palladium catalyst to yield vinyl

acetate.



14.2.2 Polymerisation

Vinyl acetate may be easily polymerised in bulk, solution, emulsion and

suspension. At conversions above 30%, chain transfer to polymer or monomer

may occur. In the case of both polymer and monomer transfer two mechanisms

are possible, one at the tertiary carbon, the other (illustrated in Figure 14.4) at the

acetate group.

H



+ ---CH,-C--



---CH, -CH -



I



OOC .CH,

Polymer



OOC . CH,

Radical



-



I

I



H



wCH, -CH,



I



+ ---CH,-C--



OOC .CH,

Polymer



I



I



OOC . CH,Radical



Figure 14.4



The radical formed at either the tertiary carbon atom or at the acetate group

will then initiate polymerisation and form branched structures.

Since poly(viny1 acetate) is usually used in an emulsion form, the emulsion

polymerisation process is commonly used. In a typical system, approximately

equal quantities of vinyl acetate and water are stirred together in the presence of

a suitable colloid-emulsifier system, such as poly(viny1 alcohol) and sodium

lauryl sulphate, and a water-soluble initiator such as potassium persulphate.

Polymerisation takes place over a period of about 4 hours at 70°C. The

reaction is exothermic and provision must be made for cooling when the batch

size exceeds a few litres. In order to achieve better control of the process and to



Poly(viny1 alcohol) 389

obtain particles with a smaller particle size, part of the monomer is first

polymerised and the rest, with some of the initiator, is then steadily added over

a period of 3-4 hours. To minimise the hydrolysis of vinyl acetate or possible

comonomers during polymerisation, it is necessary to control the pH throughout

reaction. For this purpose a buffer such as sodium acetate is commonly

employed.



14.2.3 Properties and Uses

Poly(viny1 acetate) is too soft and shows excessive 'cold flow' for use in

moulded plastics. This is no doubt associated with the fact that the glass

transition temperature of 28°C is little above the usual ambient temperatures and

in fact in many places at various times the glass temperature may be the lower.

It has a density of 1.19g/cm3 and a refractive index of 1.47. Commercial

polymers are atactic and, since they do not crystallise, transparent (if free from

emulsifier). They are successfully used in emulsion paints, as adhesives for

textiles, paper and wood, as a sizing material and as a 'permanent starch'. A

number of grades are supplied by manufacturers which differ in molecular

weight and in the nature of comonomers (e.g. vinyl maleate) which are

commonly used (see Section 14.4.4)

The polymers are usually supplied as emulsions which also differ in the

particle size, the sign of the charge on the particle, the pH of the aqueous phase

and in other details.

Being an amorphous polymer with a solubility parameter of 19.4 MPa'12, it

dissolves in solvents with similar solubility parameters (e.g. benzene 6 =

18.8MPa1", chloroform 6 = 19.0MPa'/2, and acetone 6 = 20.4MPa'12.

14.3 POLY(V1NYL ALCOHOL)

Vinyl alcohol does not exist in the free state and all attempts to prepare it have

led instead to the production of its tautomer, acetaldehyde.



+CH,CHO



CH,=CH



I



OH

Poly(viny1 alcohol) is thus prepared by alcoholysis of a poly(viny1 ester) and in

practice poly(viny1 acetate) is used (Figure 14.5).



-



CH,- CH-



I



+



CH,OH --CH,-CH*



OCC .CH,



I



+



OH

CH,COOCH,



Figure 14.5



The term hydrolysis is sometimes incorrectly used to describe this process. In

fact water does not react readily to yield poly(viny1 alcoho1)s and may actually

retard reaction where certain catalysts are used.

Either methanol or ethanol may be used to effect alcoholysis but the former is

often preferred because of its miscibility with poly(viny1 acetate) at room



390 Poly(viny1 acetate) and its Derivutives

temperature and its ability to give products of better colour. Where methanol is

employed, methyl acetate may be incorporated as a second solvent. It is also

formed during reaction. The concentration of poly(viny1 acetate) in the alcohol is

usually between 10 and 20%.

Either acid or base catalysis may be employed. Alkaline catalysts such as

caustic soda or sodium methoxide give more rapid alcoholysis. With alkaline

catalysts, increasing catalyst concentration, usually less than 1% in the case of

sodium methoxide, will result in decreasing residual acetate content and this

phenomenon is used as a method of controlling the degree of alcoholysis.

Variations in reaction time provide only a secondary means of controlling the

reaction. At 60°C the reaction may takes less than an hour but at 20°C complete

‘hydrolysis’ may take up to 8 hours.

The use of acid catalysts such as dry hydrochloric acid has been described in

the literature but are less suitable when incompletely ‘hydrolysed’ products are

desired as it is difficult to obtain reproducible results.

Commercial poly(viny1 alcohol) (e.g. Gelvatol, Elvanol, Mowiol and Rhodoviol) is available in a number of grades which differ in molecular weight and in

the residual acetate content. Because alcoholysis will cause scission of branched

polymers at the points where branching has proceeded via the acetate group,

poly(viny1 alcohol) polymer will have a lower molecular weight than the

poly(viny1 acetate) from which it is made.



14.3.1 Structure and Properties

Poly(viny1 acetate) is an atactic material and is amorphous. Whilst the structure

of poly(viny1 alcohol) is also atactic the polymer exhibits crystallinity and has

essentially the same crystal lattice as polyethylene. This is because the hydroxyl

groups are small enough to fit into the lattice without disrupting it.

The presence of hydroxyl groups attached to the main chain has a number of

significant effects. The first effect is that the polymer is hydrophilic and will

dissolve in water to a greater or lesser extent according to the degree of

‘hydrolysis’ and the temperature. Polymers with a degree of ‘hydrolysis’ in the

range of 8 7 4 9 % are readily soluble in cold water. An increase in the degree of

‘hydrolysis’ will result in a reduction in the ease of solubility and fully

‘hydrolysed’ polymers are only dissolved by heating to temperatures above

85°C.

This anomalous effect is due to the greater extent of hydrogen bonding in the

completely ‘hydrolysed’ polymers. Hydrogen bonding also leads to a number of

other effects, for example, unplasticised poly(viny1 alcohol) decomposes below

its flow temperature. The polymer also has a very high tensile strength and is

very tough. Films cast from high molecular weight grades, conditioned to 35%

humidity, are claimed2 to have tensile strengths as high as 180001bf/in2

( I 25 MPa).

The properties will be greatly dependent on humidity; the higher the humidity,

the more the water absorbed. Since water acts as a plasticiser there will be a

reduction in tensile strength but an increase in elongation and tear strength.

Figure 14.6 shows the relationship between tensile strength, percentage

‘hydrolysis’ and humidity.

Because of its high polarity, poly(viny1 alcohol) is very resistant to

hydrocarbons such as petrol. Although the polymer will dissolve in lower alcoholwater mixtures, it does not dissolve in pure alcohols. As it is crystalline as well as



The Poly(viny1 acetals) 39 1



I



DEGREE OF HYDROLYSIS IN



o/r



50



40



Figure 14.6. Relation between tensile strength and degree of ‘hydrolysis’ for unplasticised poly(viny1

alcohol) film. (After Davidson and Sittig’)



highly polar only a few organic solvents, such as diethylenetriamine and

triethylenetetramine, are effective at room temperature. As might be expected, the

hydroxyl group is very reactive and many derivatives have been prepared.

The polymer may be plasticised by polar liquids capable of forming hydrogen

bonds with the hydroxyl groups. Glycerin has been used for this purpose.



14.3.2 Applications

Poly(viny1 alcohol) is employed for a variety of purposes. Film cast from

aqueous alcohol solution is an important release agent in the manufacture of

reinforced plastics. Incompletely ‘hydrolysed’ grades have been developed for

water-soluble packages for bath salts, bleaches, insecticides and disinfectants.

Techniques for making tubular blown film, similar to that used with

polyethylene, have been developed for this purpose. Moulded and extruded

products which combine oil resistance with toughness and flexibility are

produced in the United States but have never become popular in Europe.

Poly(viny1 alcohol) will function as a non-ionic surface active agent and is

used in suspension polymerisation as a protective colloid. In many applications

it serves as a binder and thickener is addition to an emulsifying agent. The

polymer is also employed in adhesives, binders, paper sizing, paper coatings,

textile sizing, ceramics, cosmetics and as a steel quenchant.

Japanese workers have developed fibres from poly(viny1 alcohol). The

polymer is wet spun from warm water into a concentrated aqueous solution of

sodium sulphate containing sulphuric acid and formaldehyde, the latter

insolubilising the alcohol by formation of formal groups.

14.4 THE POLY(V1NYL ACETALS)

Treatment of poly(viny1 alcohol) with aldehydes and ketones leads to the

formation of poly(viny1 acetals) and poly(viny1 ketals), of which only the former

products are of any commercial significance (Figure 14.7).



392 Poly(viny1 acetate) and its Derivatives



wCH,-CH-CH,-CH-CHz-CH-CHz-CH-CHz-CH~



I



I



I



OH



OH



I



OH



OH



0



0



C



C



II



I



OH



II



wCH,-CH-CH,-CH-CH,-CH-CH,-~~-~~z-~~w



I



I



I



I



I



A Poly(Viny1 Acetal)

Figure 14.7



The products are amorphous resins whose rigidity and softening point depend

on the aldehyde used. Poly(viny1 butyral), with the larger side chain, is softer

than poly(viny1 formal). Since the reaction between the aldehyde and the

hydroxyl groups occurs at random, some hydroxyl groups become isolated and

are incapable of reaction. A poly(viny1 acetal) molecule will thus contain:



(1) Acetal groups.

(2) Residual hydroxyl groups.

(3) Residual acetate groups, due to incomplete 'hydrolysis' of poly(viny1

acetate) to poly(viny1 alcohol).



14.4.1 Poly(viny1 formal)

The poly(viny1 acetals) may be made either from poly(viny1 alcohol) or directly

from poly(viny1 acetate) without separating the alcohol. In the case of poly(viny1

formal) the direct process is normally used.

In a typical process, 100 parts of poly(viny1 acetate) are added to a mixture of

200 parts acetic acid and 70 parts water, which has been warmed to about 70°C,

and stirred to complete solution. Sixty parts of 40% formalin and 4 parts

sulphuric acid (catalyst) are added and reaction is carried out for 24 hours at

70°C. Water is added to the mixture with rapid agitation to precipitate the

granules, which are then washed free from acid and dried.

A number of grades of poly(viny1 formal) are commercially available

(Formvar, Mowital) which vary in degree of polymerisation, hydroxyl content

and residual acetate content.

Table 14.13 shows the influence of these variables on some properties. The

residual hydroxyl content is expressed in terms of poly(viny1 alcohol) content

and residual acetate in terms of poly(viny1 acetate) content.



The Poly(viny1 acetals) 393

Table 14.1 Influence of structure variables on the properties of poly(viny1 formal)

Various grades of poly(vinyl formal)



ASTM test

Av. D. of P.

Poly(viny1 alcohol) (%)

Poly(viny1 acetate) (%)

Flow temperature (“C)

Deflection temperature

under load

Tensile strength (lo-’

Ibfhn’)

(MPa)

Elongation (%)

Impact strength (hod f in

X f in) (ft lbf in -’)

Water absorption (%)



-



350



500

5-6

9.5-13

160-170

88-93



500

7-9

9.5-13

160-170

88-93



350

7-9

9.5-13

140-145

88-93



430

5-7

20-27

145-150

75-80



40-50



D.638-41T

D.256-43T



10

69

7-20

1.2-2.0



10

69

10-50

1.2-2.0



10

69

10-50

1.0-1.4



10

69

4-5

0.5-0.7



10

69

3-4

0.4-0.6



D.570-40T



0.75



1.1



1.1



1.5



1-5



D.569-48T

D.648-49T

D.638-41T

-



5 -7

-



50-60



It will be observed that molecular weight has little effect on mechanical

properties but does influence the flow temperature.

The hydroxyl content of commercial material is kept low but it is to be

observed that this has an effect on the water absorption. Variation in the residual

acetate content has a significant effect on heat distortion temperature, impact

strength and water absorption. The incorporation of plasticisers has the usual

influence on mechanical and thermal properties.

The polymer, being amorphous, is soluble in solvents of similar solubility

parameter, grades with low residual acetate being dissolved in solvents of

solubility parameter between 19.8 and 22 MPa’”.

The main application of poly(viny1 formal) is as a wire enamel in conjunction

with a phenolic resin. For this purpose, polymers with low hydroxyl (5-6%) and

acetate (9.5-13%) content are used. Similar grades are used in structural

adhesive (e.g. Redux) which are also used in conjunction with phenolic resin.

Poly(viny1 formal) finds some use as a can coating and with wash primers.

Injection mouldings have no commercial significance since they have no features

justifying their use at current commercial prices.



14.4.2 Poly(viny1 acetal)

Poly(viny1acetal) itself is now of little commercial importance. The material may

be injection moulded but has no particular properties which merit its use. It is

occasionally used in conjunction with nitrocellulose in lacquers, as a vehicle for

wash primers and as a stiffener for fabrics.

14.4.3 Poly(viny1 butyral)



As a safety glass interleaver, poly(viny1 butyral) (Butacite, Saflex) is extensively

used because of its high adhesion to glass, toughness, light stability, clarity and

moisture insensitivity.

It also finds miscellaneous applications in textile and metal coatings and in

adhesive formulations. Where it is to be used as a safety glass interleaver, a

very pure product is required and this is most conveniently prepared from



394 Poly(viny1 acetate) and its Derivatives

poly(viny1 alcohol) rather than by the direct process from poly(viny1

acetate).

In a typical process 140 parts of fully ‘hydrolysed’ poly(viny1 alcohol) are

suspended in 800 parts of ethanol; 80 parts of butyraldehyde and 8 parts of

sulphuric acid are added and the reaction is carried out at about 80°C for 5-6

hours.

The solution of poly(viny1 butyral) is diluted with methanol and the polymer

precipitated by the addition of water during vigorous agitation. The polymer

is then stabilised, washed and dried.

Highly ‘hydrolysed’ poly(viny1 alcohol) is normally used as a starting point.

For safety glass applications about 25% of the hydroxyl groups are left

unreacted. In this application the polymer is plasticised with an ester such as

dibutyl sebacate or triethylene glycol di-2-ethyl butyrate, about 30 parts of

plasticiser being used per 100 parts of polymer. The compound is then

calendered to a thickness of 0.015 in and coated with a layer of sodium

bicarbonate to prevent blocking. To produce safety glass the film is washed

and dried and then placed between two pieces of glass which are then

subjected to mild heat and pressure. Bulletproof glass is made by laminating

together several layers of glass and poly(viny1 butyral) film.

Laminated safety glass has now become standard for automobile windscreens and is used for aircraft glazing.

14.5 ETHYLENE-VINYL ALCOHOL COPOLYMERS

If ethylene is copolymerised with vinyl acetate, and the vinyl acetate

component ‘hydrolysed’ to vinyl alcohol, a material is produced which is in

effect a copolymer of ethylene and vinyl alcohol.

The material is produced by Kurardy and Nippon Gohsei in Japan and was

also produced up until 1993 by Du Pont. Global nameplate capacity has

increased from about 30 000 t.p.a. early in the 1990s to 60 000 t.p.a. at the end

of the millenium. The material is commonly referred to in the abbreviated form

EVOH but occasionally also as EVAL and EVOL.

Certain copolymers of this type have been found to have excellent gas

barrier properties, with the dry polymer having an oxygen permeability only

about 1/ I 0th that of polyvinylidene chloride. Unsurprisingly, the copolymer has

a high moisture absorption and a high moisture vapour transmission rate.

Where the material is swollen by water, gas permeability is also higher.

For reasons explained below, the effect of increasing the ‘vinyl alcohol’

content in EVOH is quite different to that of increasing the vinyl acetate

content in EVA. In the case of ethylene-vinyl acetate (EVA) copolymers,

increasing the vinyl acetate content up to about 50% makes the materials less

crystalline and progressively more flexible and then rubbery. In the range

40-70% vinyl acetate content the materials are amorphous and rubbery, whilst

above 70% the copolymers become increasingly rigid and brittle.

Commerical grades of EVOH typically have ‘vinyl alcohol’ contents in the

range 56-71%, but in contrast to the corresponding EVA materials these

copolymers are crystalline. Furthermore, an increase in the ‘vinyl alcohol’

content results in an increase in such properties as crystalline melting point,

tensile strength and tensile modulus together with a decrease in oxygen

permeability. This is a reflection of the fact that the ethylene and vinyl alcohol

units in the chain are essentially isomorphous (see Sections 4.4 and 14.3.1).



Poly(viny1 cinnamate) 395

Table 14.2 Typical properties of EVOH copolymers (For purposes of comparison the grades

selected all have a MFI (2.16kg, 190OC) of 1.7-1.8. Grades with other MFI values are also

available)



I

Specific gravity

r, (by D W ("C)

Tg (by DSC) ("C)

Tensile strength (MPa)

Elongation at break (%)

Tensile modulus (MPa)

Oxygen permeability cc.20 p/m2 24 h atm.

0% RH, 20°C

25% RH, 25°C



Ethylene content (mole %)



1.21

188



62

96

75-150

3900

0.23

0.8



100-200

3700

0.30



1.17

173

58

75

>180

3100



1.14

164

55

62

>280

2700



0.53

1.4



1.20

2.6



Some typical properties of some commercial EVOH polymers (SoamolNippon Gohsei) are given in Table 14.2.

As is to be expected, the table shows that as the humidity is increased,

causing swelling and an increase in the interchain separation, so the oxygen

permeability increases. Also, as expected, the percentage increase is greater the

higher the vinyl alcohol content.

Because of the excellent gas barrier properties, EVOH is of interest as a

packaging material. However, because of its high water absorption it is usually

used as an internal layer in a co-extruded film, sheet, bottle or tube. For

example, the system HDPE-EVOH-EVA may be used as a barrier film for

packaging cereals, and the system polystyrene-EVOH-polystyrene for packaging coffee and cream, whilst the system polystyrene-EVOH-polyethylene has

the additional advantage of heat sealability.

In the case of EVOH being used as an interlayer with polyethylene or

polystyrene, it is necessary to use additional adhesive layers such as

an ethylene-vinyl acetate-maleic anhydride terpolymer (e.g. OrevacAtochem).

While EVOH is of interest primarily for food packaging applications attention

is now being turned to non-food outlets such as automotive fuel tanks, floor

heating pipes and toothpaste tubes.



14.6 POLY(V1NYL CINNAMATE)

Poly(viny1 cinnamate) is not used in the traditional areas of plastics technology

but its ability to cross-link on exposure to light has led to important applications

in photography, lithography and related fields as a photoresist.

The concept of a Photoresist is of great antiquity and has a number of features

of interest relating to plastics. In Ancient Egypt mummies were wrappted in linen

cloths dipped in a solution of oil of lavender containing high molecular mass

bituminous material (Chapter 30) which was known variously as Syrian Asphalt

or Bitumen of Judea. On exposure to light the product hardened and became

insoluble. The evidence is that some form of cross-linking occurred.



396 Poly(viny1 acetate) and its Derivatives

At the beginning of the nineteenth century, an amateur Egyptologist, J.

Nictphore Niepce, became interested in the process and in 1822 he adapted it to

produce the first permanent photograph. It also played an important role in the

development of lithography. In essence surfaces exposed to light become

insoluble and cannot be removed by solvents whilst unexposed surfaces remain

soluble and can be so removed. This is the concept of a negative photoresist.

(There also exist positive photoresists, including some phenolic resins, which

become more soluble on exposure to light). Today photoresists are used in the

fabrication of solid-state electronic components and integrated circuits and

poly(vin1y cinnamate) is one of the longest established materials of this type.

As with poly(viny1 alcohol), poly(viny1 cinnamate) is prepared by chemical

modification of another polymer rather than from ‘monomer’. One process is to

treat poly(viny1 alcohol) with cinnamoyl chloride and pyridine but this is rather

slow. Use of the Schotten Baumann reaction will, however, allow esterification

to proceed at a reasonable rate. In one example4 poly(viny1 alcohol) of degree of

polymerisation 1400 and degree of saponification of 95% was dissolved in water.

To this was added a concentrated potassium hydroxide solution and then

cinnamoyl chloride in methyl ethyl ketone. The product was, in effect a vinyl

alcohol-vinyl cinnamate copolymer Figure 14.8)

+CH2



-CH-ft

I



CH,-



OH



+



KOH



CHj



I



OH



+CH2-



-



+ @-CH=CH.COCI



CH-ftCH,-



CH+



OH



0



I



I

I



Unchanged

Vinyl

Alcohol

Units



co

I



CH



+



KCI



+ H,O



II



Cinnamoyl Chloride



Figure 14.8



To make a photoresist poly(viny1 cinnamate), or a high vinyl cinnamate

copolymer, is dissolved in a solvent such as methylene dichloride and the

solution is coated uniformly over the substrate by a process such as spin casting.

After evaporation of the solvent a masking material (which in the case of a

simple demonstration could be a paper clip) is placed on the resist and the

assembly is exposed to ultraviolet light. The exposed surfaces are then

insolubilised. After exposure the mask is removed and soluble matter dissolved

in a solvent such as cellosolve acetate and this exposes the substrate in the shape

of the mask. This may then be etched or otherwise treated as required. By the use

of appropriate sensitisers such as, 1,2-benzanthraquinone or Michler ’s ketone the

cross-linking may be brought about by visible light. The cross-linking is believed

to involve the production of a four-membered cyclobutane ring (Figure 14.9).



Figure 14.9



Bibliography



397



14.7 OTHER ORGANIC VINYL ESTER POLYMERS

Polymers from many other vinyl esters, such as vinyl propionate, vinyl caproate,

vinyl benzoate, vinyl stearate and vinyl laurate, have been prepared on a

commercial scale. As is to be expected, increasing the length of the side chain

reduces the softening point of the polymer so that polymers similar in many ways

to the higher acrylates and methacrylates may be obtained. It is also of interest

to note that, as with acrylates and methacrylates, the glass transitions of the

polymers go through a minimum with about twelve carbon atoms in the side

chain, side-chain crystallisation becoming important with higher homologues.

Of the higher vinyl ester homopolymers only poly(viny1 propionate) is

currently believed to be of commercial value, being marketed as Propiofan

(BASF) for surface coating application where greater alkali resistance is possible

than with the normal vinyl acetate based copolymers.

Whilst vinyl acetate is reluctant to copolymerise it is in fact usually used today

in copolymers. Two of particular interest to the plastics industry are ethylenevinyl acetate (Chapter 11) and vinyl chloride-vinyl acetate copolymers (Chapter

12). In surface coatings internal plasticisation to bring the Tg to below ambient

temperatures and thus facilitate film forming is achieved by the use of ethyl

acrylate, butyl acrylate, 2-ethylhexyl acrylate and dialkyl maleates and

fumarates.



References

1.

2.

3.

4.



Chem. Ind., 1749 (1955)

and SITTIG, M., Water-soluble Resins, Reinhold, New York (1962)

FITZHUGH, A.F., and LAVIN, E., J. Electrochem. Soc., 100 (8), 351 (1953)

DELZENNE, G.A., Encyclopaedia of Polymer Science and Technology, Supplement, Vol. 1, p.401,

Wiley, New York (1976)

HORN.O.,



DAVIDSON, R.L.,



Bibliography

General



Polyvinylakohole, Enka, Stuttgart (1949)

c. (Ed.), Vinyl and Diene Monomers (High Polymers Series Vol. 24). Wiley-Interscience,

New York (1971)

SCHILDKNECHT, c.E., Vinyl and Related Polymers, John Wiley, New York (1952)

Encyclopaedia of Polymer Science and Technology Vols. 14 and 15, Wiley-Interscience, New York

(1971)

KAINER, F.,



LEONARD, E.



Polyvinyl Acetate

WHEELER, o.L., LAVIN. E.,



and



CROZIER, R.N.,



J. Polymer Sci., 9. 157 (1952)



Polyvinyl Alcohol

Brit. Plastics. 16, 77, 84, 122 (1944)

DAVIDSON. R.L., and SITI-IG, M., Water-soluble Resins (2nd Ed.), Reinhold, New York (1968)

RNCH, C.A. (Ed.), Polyvinyl alcohol: Properties and Applications, Wiley New York (1973)

PRITCHARD, J.c., Poly(Viny1 alcohol): Basic Properties and Uses, Macdonald, London (1970)

Properties and Applications of Polyvinyl Alcohol (SCI Monograph No. 30), Society of the Chemical

Industry, London (1968)

Polyvinyl Acetals

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Poly(viny1 acetate) and its Derivatives

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