Progress in Organic Coatings 52 (2005) 144–150

Synthesis and characterization of pure poly(acrylate) latexes

R. Seda Tıglı∗, Vural Evren

Hacettepe University, Chemical Engineering Department, 06532 Ankara, Turkey

Received 27 May 2004; received in revised form 13 September 2004; accepted 5 October 2004

Abstract

Aqueous emulsions used as binders in solvent-free paint formulations have to cope with the challenge to guarantee an excellent filmformation and appearance as well as good mechanical properties. One strategy to fulfill these contradictory requirements is the employmentof pure poly(acrylate) resins synthesized by emulsion polymerization.

For the production of acrylic resin, homo and copolymers were synthesized by emulsion polymerization using methyl acrylate (MA), ethylacrylate (EA), butyl acrylate (BA) monomers. The film structures of homo and copolymers were investigated and three of them [P(MMA/BA)1:1, P(MMA/EA) 1:1.5, P(MMA/MA) 1:3] were indicated as appropriate binders for paint production.

rmined andt oss and UVr was foundt chanicalc©

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For latex characterization and determination of film formation properties, particle size and surface charge densities are detehermal analyses were made. The films were characterized by their mechanical properties like hardness, flexibility, adhesion, glesistance. Mechanical analysis test results clearly show that among other selected copolymers P(MMA/EA) 1:1.5 copolymero have satisfactory mechanical properties with excellent film forming ability. As AFM studies were in good agreement with meharacterization, P(MMA/EA) 1:1.5 copolymer was suggested as a binder that can be used in the paint industry.2004 Elsevier B.V. All rights reserved.

eywords:Emulsion polymerization; Latex; Acrylic resin; Methyl methacrylate; Butyl acrylate; Ethyl acrylate

. Introduction

Under the volatile organic compounds (VOC) regulationstrengthened from the viewpoint of environmental protection,aterborne paints has been an important research topic allver the world. The result of this effort is, among others,aterborne coatings such as acrylic emulsions.Acrylic resins, which have an important commercial appli-

ation in paint industry, are prepared through the polymeriza-ion of acrylic and methacrylic acids or their correspondingsters. Among binders, acrylic resins find use in a varietyf paint and coatings that support the automotive, appliance,nd coil industries. The key attribute of acrylic coatings is

heir resistance to hydrolysis during extended exterior expo-ure (weathering), high block resistance, hardness, gloss andigh alkali and oxidation resistance[1].

∗ Corresponding author. Tel.: +90 312 2977402; fax: +90 312 2992124.E-mail addresses:stigli@hacettepe.edu.tr (R.S. Tıglı),

ural@hacettepe.edu.tr (V. Evren).

However, all classes of traditional paints are currentlying converted into waterborne paints, and all new waterbpaints require new aqueous resins. One strategy to fulfillcontradictory requirements is the employment of pure acresins, synthesized by emulsion polymerization process

One of the most important processes to manufaacrylic resin is emulsion polymerization[2]. In order to obtaina well-defined latex, it is important to optimize polymerition process with regard to emulsifiers, initiator and wasoluble monomers[3]. However, particle size, glass transittemperature (Tg), surface charge density of latex particlestype of monomers change the properties of polymers, sysized by emulsion polymerization.

In the present study, it was aimed to investigate the uof pure waterborne poly(acrylate) resins, in which memethacrylate (MMA) was used as the main monomebinder in paint industry. The film formation structure aproperties of resins, which were synthesized systematiwere investigated in order to determine the propertiemonomers in acrylic resin structure which characterize p

300-9440/$ – see front matter © 2004 Elsevier B.V. All rights reserved.oi:10.1016/j.porgcoat.2004.10.004

R.S. Tıglı, V. Evren / Progress in Organic Coatings 52 (2005) 144–150 145

erties of binders. Consequently, a resin production guide sys-tem was developed for the users’ needs.

2. Experimental

2.1. Materials

Methyl methacrylate (MMA), ethyl acrylate (EA), butylacrylate (BA), methyl acrylate (MA), which were suppliedfrom Roehm Company (Germany), were purified by treatingwith 10% sodium hydroxide solution followed by washingswith deionized water to remove inhibitor. They were fur-ther distilled under vacuum before use. Potassium persulfate(KPS) (Analar grade, BDH Chemicals Ltd., Poole, UK) ofextra pure grade was used as initiator without further pu-rification. Sodium dodecyl sulfate (SDS; Sigma, Germany),which was used as emulsifier, was of analytical grade andused as received. Deionized water was used throughout theexperimental work.

2.2. Emulsion polymerization

The emulsion polymerization was performed in a sealedcylindrical reactor (Pyrex®, USA; volume: 500 ml) placedin a shaking water bath equipped with a temperature controls tioni withr ersw withb edi ctor.T ath atr rriedo e of7

2c

te)( eres hichw la-t A,M yc moa car-r

2

C)w

M

Table 1Receipts for polymerization process

Polymer Monomer(w/v%)

SDSconcentration(w/v%)

KPS concentration(w/v%, waterbased)

PMMA 25 0.16 0.10PEA 25 0.16 0.10PBA 25 0.33 0.10P(MMA/MA) 3:1 40 0.16 0.27P(MMA/MA) 1:1 40 0.16 0.27P(MMA/MA) 1:3 40 0.16 0.27P(MMA/EA) 3:1 40 0.16 0.27P(MMA/EA) 1:1 40 0.16 0.27P(MMA/EA) 1:1.5 40 0.16 0.27P(MMA/EA) 1:2 40 0.16 0.27P(MMA/EA) 1:3 40 0.16 0.27P(MMA/BA) 3:1 44 0.33 0.27P(MMA/BA) 2:1 40 0.33 0.27P(MMA/BA) 1:1 43 0.33 0.27P(MMA/BA) 1:2 40 0.33 0.27P(MMA/BA) 1:3 44 0.33 0.27

TSC (%)= m2

m1× 100 (2)

wherem0 is the total weight of monomer used in the synthesis,m1 the weight of latex emulsion,m2 the weight of dry sampleof latex,VL, volume of latex.

The particle sizes and distributions were determined withMalvern Instruments Zetasizer 1000 particle size analyzer byusing dynamic light scattering principle.

The charge density of latex particles was determined by apotentiometric titration method[4]. The 5 wt.% latex emul-sion (30 ml) was treated with 6 g of ion exchange resin mix-ture consisting of equal mass of Dowex, SBR-P anion ex-change resin (OH type) and Dowex, HCRS-S cation exchangeresin (H type; Abac1 Kimya, Turkey) in a magnetic stirrer.After the ion exchange, pH of latex emulsion was brought to3.0 by adding 0.01 N HCl solution. The resulting emulsionwas titrated with 0.025 N NaOH solution, potentiometrically.By using inflection points observed in the titrations, the masscharge density (Qm, mequiv./g) and surface charge density(Qs, �C/cm2) of produced latex particles were calculated[5].The mass charge densities and surface charge densities aredetermined from:

Qm = CNaOHVNaOH

mp(3)

Q

w u-t -fl n,F(

mersw eter(

ystem. A typical procedure for the emulsion polymerizas presented here. The micellar solution (SDS solution)espect to the total emulsifier in the recipe and monomere charged into the reactor. The reactor was purgedubbling nitrogen for 5 min. The initiator (KPS), dissolv

n a minimum quantity of water, was added into the reahe sealed reactor was placed into a shaking water boom temperature. The emulsion polymerization was caut for 3 h with 200 cpm shaking rate at a temperatur0± 1◦C.

.3. Latex production by emulsion homo andopolymerization of acrylates

Poly(methyl methacrylate) (PMMA), poly(butyl acrylaPBA) and poly(ethyl acrylate) (PEA) homopolymers wynthesized according to polymerization conditions were determined from preparatory work. The different

ex formulations (co-acrylate formulations) like MMA-EMA-BA and MMA-MA copolymers were synthesized b

hanging monomer ratios from 3:1 to 1:3 (by volume). Hond copolymerization reactions for latex production wereied out using recipes given inTable 1.

.4. Polymer latex characterization

Total solid content (TSC) and monomer conversion (Mere determined by gravimetric analysis method from:

C (%) = m2

m0/VL× 100 (1)

s = QmF

Sp(4)

here CNaOH (N) is the concentration of NaOH solion, VNaOH (ml) the volume of NaOH solution at inection point,mp (g) the particle mass in latex solutio

(96485314�C/mequiv.) the Faraday’s constant, andSpcm2/g) the specific surface area.

Thermal analyses of synthesized homo and copolyere performed by using differential scanning calorim

DSC, Du Pont Instruments) at a rate of 10◦C/min. Glass

146 R.S. Tıglı, V. Evren / Progress in Organic Coatings 52 (2005) 144–150

transition temperatures (Tg) of polymers are determined fromDSC thermograms.

2.5. Film formation and mechanical characterization

Films were prepared by deposition of a small amount of la-tex on glass plates and air-dried at room temperature in orderto determine the physical properties of the films. Emulsionfilms were cast at room temperature with a wet thickness of150�m on aluminium plates for mechanical characterizationof the films.

2.5.1. Hardness testHardness of the dry latex film was determined accord-

ing to DIN 53153 with Bucholz indentation hardness tester(Sheen 605, UK). For the measurement of Buchholz indenta-tion resistance the procedure is presented below: The inden-ter, which is a rectangular metal block of 1000± 5 g massfitted with a spirit level and two pointed feet and a circu-lar indenter manufactured from hardened steel, was carefullyplaced vertically on to the coated test panel and removed after30 s. The indentation was viewed through an illuminated mi-croscope with 20× magnification and was determined fromthe indentation length on microscope lens with 10 mm scale.Results were expressed as Buchholz indentation resistancea

B)

2d

g toA en,U pro-c ver am pres-s 180a di-a ce oft Thee ndreld

2ing

t n oft

2DIN

6 testm a re-fl

intended to give improved differentiation between low-glossfilms. Consequently, prepared acrylic films, which have thecharacteristic of low-gloss, were tested under 85◦ geometry.

2.5.5. UV resistanceIn order to determine the UV resistance of the dry latex

film, samples were exposed to UV light with 360 W power for16 h. Then hardness, adhesion, gloss and deformation testswere repeated.

2.5.6. Atomic force microscopy (AFM)AFM experiments were carried out in order to photo-

graph film forming properties of synthesized MMA/EA 1:1.5copolymer film and to obtain detailed information about thestructure of the polymer film. Film to be imaged was pre-pared by placing a drop of latex onto a freshly cleaved micaplate. The film was allowed to air-dry at ambient temperaturefor 24 h prior to imaging. AFM images were obtained underambient conditions while operating the instrument in contactmode with silicon nitride cantilevers. Scanned images wereof size 4�m× 4�m. The principles of AFM are describedin detail elsewhere[6].

3. Results and discussion

3

ro-dP te)( eres eter-mm BAm izedb ms ationi . Ina ersc uiredm rm a-c t lowc tionw latexp de-c abilityo sta-b se ini

tex,m . Ath ulumf f thel ous

nd calculated from the formula:

uchholz indentation resistance= 100

indentation length (mm

(5)

.5.2. Dry film elasticity (cylindrical mandrel test,eformation test)

Elasticity of the dry latex film was measured accordinSTM D522 with cylindrical Mandrel test apparatus (SheK). For the measurement of elongation of the films theedure is presented below: the test panel was placed oandrel with uncoated side in contact. Using a steady

ure of the fingers the panel was bended approximately◦round the mandrel at a uniform velocity. Mandrels ofmeters 3.2, 6.4 and 9.5 mm were used and the surfa

he film was observed whether cracking has occurred.longation percent was determined according to the maiameter.

.5.3. Adhesion testAdhesion of the dry latex film was determined accord

o ASTM D3359 (cross-cut technique). The classificatiohe samples was made according to EN ISO 2409.

.5.4. Gloss testGloss of the dry latex film was measured according to

7530 with microgloss (Sheen 160, UK) which specifies aethod for determining the specular gloss of films using

ectometer geometry of 20◦, 60◦ or 85◦. The 85◦ geometry is

.1. Latex polymerization

Homo and copolymerization reactions for latex puction were carried out using recipes given inTable 1.oly(methyl methacrylate) (PMMA), poly(butyl acryla

PBA) and poly(ethyl acrylate) (PEA) homopolymers wynthesized according to polymerization conditions dined from preparatory work. According toTable 1, requiredinimum surfactant concentration with latexes usedonomer was 0.33 vol.%. Latexes, which were synthesy using EA, MA and MMA monomers, have the minimuurfactant concentration of 0.16%. Surfactant concentrncrease was due to the low polarity of BA monomercrylic latex emulsions, differences in polarity of monomhange the adsorption area of the surfactant and the reqinimum surfactant concentration[7]. MMA is a more polaonomer than BA[9,11]. Consequently, it has low interf

ial tensions and high adsorption area. For both groups, aoncentration of the anionic surfactant, coagulum formaas observed as a result of electrostatic instability of thearticles. A decrease in the double layer thickness withreased surfactant concentration results in decreased stf latex particles. At higher surfactant concentration, theility of the latex may be reduced because of an increa

onic concentration of the continuous phase[8,10].To improve the percentage of the solid in the la

onomer concentration was varied from 25% to 45%igher concentrations of monomers, above 45%, coag

ormation was observed because of reduced stability oatex with increase in ionic concentration of the continu

R.S. Tıglı, V. Evren / Progress in Organic Coatings 52 (2005) 144–150 147

Table 2The total solid content (TSC) and monomer conversion (MC)

Polymer Monomer (w/v%) MC (%) TSC (%)

PMMA 25 88.0 22.0PEA 25 98.0 24.5PBA 25 91.6 22.9P(MMA/MA) 3:1 40 92.2 36.9P(MMA/MA) 1:1 40 86.7 34.7P(MMA/MA) 1:3 40 83.2 33.3P(MMA/EA) 3:1 40 95.2 38.1P(MMA/EA) 1:1 40 94.5 37.8P(MMA/EA) 1:1.5 40 92.5 37.0P(MMA/EA) 1:2 40 97.5 39.0P(MMA/EA) 1:3 40 93.5 37.4P(MMA/BA) 3:1 44 85.6 37.6P(MMA/BA) 2:1 40 92.5 37.0P(MMA/BA) 1:1 43 96.0 41.3P(MMA/BA) 1:2 40 97.5 39.0P(MMA/BA) 1:3 44 86.0 37.8

Table 3Average particle size and polydispersity index values

Polymer Average particlesize (nm)

Polydispersityindex values

PMMA 78.4 1.100PBA 177.7 1.097P(MMA/MA) 1:3 93.1 1.097P(MMA/EA) 1:1.5 110.3 1.086P(MMA/BA) 3:1 84 1.077P(MMA/BA) 1:1 127.6 1.077

phase. As monomer concentration was increased, initiator(KPS) concentration was increased to 0.27 vol.% in water.

The total solid content (TSC) and monomer conversion(MC) of the polymerization are given inTable 2as wt.%. Asit is seen fromTable 2, monomer conversion is high.

3.2. Latex characterization

The particle sizes and distributions were determined withMalvern Instruments Zetasizer 1000 particle size analyzerby using dynamic light scattering principle. Average particlesize and polydispersity index values are given inTable 3. Theparticle size in the latex (Table 3) was observed to be 78.4 and177.7 nm for PMMA and PBA as minimum and maximumaverage particle sizes, respectively. The copolymeric micro-spheres were observed to have high average particle size dueto the molecular weight and percent of the second monomer(EA, MA, BA). From the polydispersity index values parti-cle size distribution of these microspheres was found to bevery narrow. So, synthesized latex particles were found to bemonodisperse.

Electrostatic repulsive forces between particles, causedby charged groups on particle surface, play an important roleduring latex formation and film formation processes. Latexsolutions which were prepared by using SDS as surfactant,h taticr t co-

Table 4Surface charge (Qs, �C/cm2) and mass charge densities (Qm, mequiv./g) ofthe synthesized latex particles

Polymer Qm (mequiv./g)× 103 Qs (�C/cm2)

PMMA 32.5 4.30PBA 13.0 3.90P(MMA/MA) 1:3 14.3 2.25P(MMA/EA) 1:1.5 15.4 2.88P(MMA/BA) 3:1 27.8 3.95P(MMA/BA) 1:1 17.4 3.74

Table 5Tg values of synthesized latex polymers, determined from DSC thermograms

Polymer Glass transition temperature,Tg (◦C)

PMMA 103P(MMA/MA) 1:3 21P(MMA/EA) 1:1.5 32.5P(MMA/EA) 1:2 –P(MMA/BA) 2:1 42.5P(MMA/BA) 1:1 37.5

agulation. Influence of surface charge densities of latex par-ticles on film formation process cannot be neglected. It ishard to control the interaction between particles due to theincrease in the number ofSO4

− groups and this can pre-vent the film formation process. The repulsive force origi-nated from the negative charges on latex surface should beweakened so that particles can make contact with each other[10]. Surface charge and mass charge densities of the syn-thesized latex particles are presented inTable 4. As it is seenfrom Table 4, surface charge densities are varied between2.25 and4.30�C/cm2 and coagulation was not observed.Tg values, determined from DSC thermograms, are pre-

sented inTable 5. The results from thermograms, shown inFig. 1, suggested that all synthesized polymers are amor-phous. Thus, only secondary transitions, e.g. the glass transi-tion temperatures (Tg), are observed. Glass transition tem-peratures of synthesized polymers are related with usedcomonomers and ratio. As it is seen fromTable 5, the glasstransition temperature decreased with increasing percent ofMMA. Polymer chain flexibility and interaction energy be-tween molecules, attraction forces, have an important role onTg. All structural properties which reduce molecular flexi-bility increase theTg value of the polymer. If a comonomerwith low Tg is added, theTg value of the main structure willdecrease. As it is seen from thermograms, the effect of MMAo

3l

tem-p malla es oftA er-t ers

ave SO4− groups on microsphere surfaces. Electros

epulsive forces, originated from these groups, preven

n synthesized copolymers is clear.

.3. Film formation characterization of the synthesizedatex films

Synthesized acrylic emulsions were air-dried at roomerature and films were prepared by deposition of smounts of latex on glass plates. The physical properti

he latex films were determined and are presented inTable 6.s it is seen fromTable 6, the observed physical prop

ies of the latex films are affected by the type of monom

148 R.S. Tıglı, V. Evren / Progress in Organic Coatings 52 (2005) 144–150

Fig. 1. DSC thermograms of (a) P(MMA/MA) 1:3, (b) PMMA, (c) P(MMA/EA) 1:1.5, (d) P(MMA/EA) 1:2, (e) P(MMA/BA) 1:1, (f) P(MMA/BA) 2:1.

R.S. Tıglı, V. Evren / Progress in Organic Coatings 52 (2005) 144–150 149

Table 6The observed physical properties of synthesized latex polymer films

Polymer Observed propertiesof polymer films

Substrateattachment(adhesion)

PMMA Hard Fragile White −PEA Soft Sticky Transparent +PBA Soft Sticky Transparent +P(MMA/MA) 3:1 Hard Fragile White −P(MMA/MA) 1:1 Hard Fragile Transparent −P(MMA/MA) 1:3 Hard Elastic Transparent +P(MMA/EA) 3:1 Hard Fragile White −P(MMA/EA) 1:1 Hard Fragile Transparent −P(MMA/EA) 1:1.5 Hard Elastic Transparent +P(MMA/EA) 1:2 Hard Elastic Opaque +P(MMA/EA) 1:3 Soft Elastic Opaque +P(MMA/BA) 3:1 Hard Fragile White −P(MMA/BA) 2:1 Hard Fragile Transparent −P(MMA/BA) 1:1 Hard Elastic Transparent +P(MMA/BA) 1:2 Hard Elastic Opaque +P(MMA/BA) 1:3 Soft Sticky Opaque +

and monomers’ ratio used during polymerization. PMMAhomopolymer forms hard and fragile films, while PBA andPEA homopolymers form soft and sticky films. In order tohave satisfactory physical properties, resins used in paint in-dustry should give films both hardness and flexibility proper-ties. PMMA, PBA and PEA homopolymers cannot be usedas binders in paint industry due to the insufficient physicalproperties of their films.

Synthesized copolymers overcome the insufficient phys-ical properties. As MA, EA and BA monomer ratios in-crease, film elasticity increases. Consequently, as it is seenfrom Table 6, P(MMA/MA) 1:3, P(MMA/EA) 1:1.5 andP(MMA/BA) 1:1 copolymers were considered to have sat-isfactory physical properties to be used as resins in paintindustry.

3.4. Atomic force microscopy (AFM)

Atomic force microscopy (AFM) was used to image mor-phology and topography of the surfaces of P(MMA/EA) 1:1.5latex and to obtain detailed information about the structureof the polymer film. In the case of P(MMA/EA) 1:1.5 sampleexamined here, the soft phase can be differentiated from thehard phase (Fig. 2). The fact that the hard phase in AFM imageseems to have different shapes is due to the random orienta-t agev theri FMps tly,a inglep de-t re oft rdp

Fig. 2. Contact mode AFM image of P(MMA/EA) 1:1.5 latex film.

Knowing the latex film structure, the question ariseswhether it can be correlated to its properties. Therefore, themechanical properties of the films were determined.

3.5. Mechanical characterization

3.5.1. Hardness testHardness of the dry latex films (P(MMA/MA) 1:3,

P(MMA/EA) 1:1.5 and P(MMA/BA) 1:1) were determinedaccording to DIN 53153 with Bucholz indentation hardnesstester (Sheen 605, UK). Results are presented as Bucholzhardness inTable 7. As it is seen fromTable 7, P(MMA/EA)1:1.5 polymer film has high Bucholz hardness compared toothers.

3.5.2. Dry film elasticity (cylindrical mandrel test,deformation test)

Elasticity of the dry latex film was measured accordingto ASTM D522 with a cylindrical Mandrel test apparatus(Sheen, UK). The scope of the test is the determination of

Table 7Hardness, adhesion, gloss and elasticity properties of emulsion latex films

Polymer Buchholzhardnessa

Adhesionb Glossc (85◦) Elongationd,εB (%)

P(MMA/MA) 1:3 76.9 5B 32.7 >28PP

ster(

byc

etus

(

ion of particles. As a consequence, the different AFM imiews from different angles of the same structure. Anomportant statement which can be derived from the Aicture is that the soft phase cannot be detected[12]. As it iseen fromFig. 2, hard/soft phase ratio is high. Consequens AFM results demonstrate that the structure of the sarticles is maintained during film formation, and that it

ermines the film structure, it can be said that the structuhe P(MMA/EA) 1:1.5 polymer film is mainly made of hahase.

(MMA/EA) 1:1.5 111.1 5B 69.5 >28(MMA/BA) 1:1 41.6 2B 76.6 >28

a According to DIN 53153 with Bucholz indentation hardness teSheen 605, UK).

b According to ASTM D3359 with cross-cut technique, estimatedross-cut classification according to EN ISO 2409.

c According to DIN 67530 with microgloss (Sheen 160, UK), 85◦ geom-try.

d According to ASTM D522 with cylindrical Mandrel test apparaSheen, UK).

150 R.S. Tıglı, V. Evren / Progress in Organic Coatings 52 (2005) 144–150

Table 8Hardness, adhesion, gloss and elasticity properties of emulsion latex filmsafter UVa treatment

Polymer Buchholzhardnessb

Adhesionc Glossd (85◦) Elongatione,εB (%)

P(MMA/MA) 1:3 71.4 5B 35.6 >28P(MMA/EA) 1:1.5 100.0 5B 78.4 >28P(MMA/BA) 1:1 47.6 4B 79.9 >28

a Exposed to UV light with 360 W power for 16 h.b According to DIN 53153 with Bucholz indentation hardness tester

(Sheen 605, UK).c According to ASTM D3359 with cross-cut technique, estimated by

cross-cut classification according to EN ISO 2409.d According to DIN 67530 with microgloss (Sheen 160, UK), 85◦ geom-

etry.e According to ASTM D522 with cylindrical Mandrel test apparatus

(Sheen, UK).

the resistance to cracking (flexibility) of coatings attachedon substrates. P(MMA/MA) 1:3, P(MMA/EA) 1:1.5 andP(MMA/BA) 1:1 latex films were bended over 3.2, 6.4 and9.5 mm diameter mandrels and the surface of the film wasobserved whether cracking has occurred. Cracking was notobserved for any of the mandrels. The elongation percentwas determined according to the mandrel diameter and re-sults were presented inTable 7. Elongation percent for allpolymer films was determined as >28%.

3.5.3. Adhesion testPolymer films were determined to have excellent adhesion

properties except P(MMA/BA) 1:1 (seeTable 7).

3.5.4. Gloss testResults are presented inTable 7.

3.5.5. UV resistanceResults are presented inTable 8. ComparingTable 8with

Table 7shows that the values are almost the same, and thatthe synthesized latex resins were not affected by UV light.UV resistance is a measure of extended exterior weather-ing. As a result, P(MMA/MA) 1:3, P(MMA/EA) 1:1.5 andP(MMA/BA) 1:1 polymer films are found to have excellentUV resistance. In fact, pure acrylic resins are known to havet

4

wa-t cry-

late (MMA) was used as the main monomer, can beused as binder in the paint industry. Acrylic monomersthat control the flexibility of the resin include ethyl acry-late and butyl acrylate. Consequently, after optimizationof emulsion polymerization process with regard to emulsi-fiers, initiator and water-soluble monomers, P(MMA/MA)1:3, P(MMA/EA) 1:1.5 and P(MMA/BA) 1:1 copolymerswere considered to have satisfactory appearance and phys-ical properties to be used as resins in the paint indus-try. The selected copolymers were found to give neatfilms.

The film formation properties are influenced by the la-tex particle size. Small particles can easily combine dur-ing film formation. However, very small particles lead toincrease emulsifier and initiator concentrations meaning in-crement in hydrophilic groups. Particle size of the selectedpolymers was determined between 93.1 and 127.6 nm. Sur-face charge densities of the selected three copolymers werevaried between 2.25 and 3.74�C/cm2 and coagulation wasnot observed. The selected polymers have lowTg values (be-tween 21 and 37.5◦C) showing that synthesized polymershave moderate flexibility. As P(MMA/EA) 1:1.5 copolymerwas found to have satisfactory mechanical properties (AFMstudies were in good agreement with mechanical charac-terization) and excellent film forming ability, this copoly-m painti

R

sel,

.

nd-tatege,

99)

185

[ er.

[ 40.[ 000)

his property.

. Conclusion

In the present study, it was demonstrated that pureerborne poly(acrylate) resins, in which methyl metha

er was suggested as a binder that can be used in thendustry.

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