Organosilicone modified styrene-acrylic latex:preparation and application

Xiaoyan Qian • Aiping Zhu • Lijun Ji

Received: 27 May 2012 / Revised: 4 January 2013 / Accepted: 6 March 2013 /

Published online: 15 March 2013

� Springer-Verlag Berlin Heidelberg 2013

Abstract In this paper, organosilicone modified styrene-acrylic (OSA) latexes for

waterproof coating were synthesized through core–shell emulsion polymerization.

The influence of emulsifier type and dosage on the size, size distribution and mor-

phology of the latex was systematically investigated. The water absorbance and

thermal decomposition behavior and the mechanical properties of the waterproof

coating depending on the organosilicone introduced on the latex shell were also

studied. Transmission electron microscopy and dynamic light scattering results indi-

cated that the particles had a regular spherical morphology with different diameters

and distributions. Thermal gravimetric analysis results revealed that the thermal sta-

bility of the latex films was improved with the introduction of organosilicone. The

waterproof property of the OSA latex film was obviously increased as compared to

that of the styrene-acrylic latex film. The tensile strength and fracture elongation of the

elastic waterproof building coating made of the OSA latex and cement powder were

significantly greater than that made of the styrene-acrylic latex and cement powder.

Keywords Organosilicone � Styrene-acrylic latex � Waterproof coating

Introduction

Degradation of cement caused by the penetration of moisture is a serious problem in

building materials. Mixing cement with waterproof latex is an effective strategy to

X. Qian � A. Zhu (&) � L. Ji

College of Chemistry and Chemical Engineering, Yangzhou University,

Yangzhou 225002, People’s Republic of China

e-mail: apzhu@yzu.edu.cn

X. Qian � L. Ji

YAPP Automotive Parts Co., Ltd., Yangzhou 225009,

People’s Republic of China

123

Polym. Bull. (2013) 70:2373–2385

DOI 10.1007/s00289-013-0958-4

prevent or control the degradation of cement [1–3]. In order to prepare cement

composites with excellent waterproofness, weather resistance and high mechanical

properties, waterproof latexes for cement composites must have low water

absorbance and good mechanical properties, and low glass transition temperature

that can endow the composites good elasticity.

Styrene-acrylic (SA) latexes are widely used for paints and adhesives because of

their specific properties such as good film-forming, gloss and transparency and

integrate mechanical properties [4–6], but their complex components and structures

also cause some problems in application. The mechanical properties of SA latex

films are temperature dependent, and their water and weather resistance are highly

influenced by the emulsifiers used in the emulsion polymerization of the SA

latexes. These weaknesses bring about a series of disadvantages when they are

mixed with cements and used as coatings for exterior walls of a building [7]. It has

been confirmed that SA latex-modified gypsum composite has a clear improve-

ment in flexural strength comparing with unmodified gypsum, but the mechanical

properties reduced about 70 % after immersion in water for 7 days [8]. Improving

the integrate properties of SA latexes is important for their applications in building

materials.

The macroscopic properties of SA latex/cement composites depend on the

components and structures of the SA latexes synthesized by emulsion copolymer-

ization and the size distribution and volume fraction of the latexes [9]. For example,

the incorporation of two different emulsifiers can lower the stability of the styrene-

acrylic latexes due to a decrease in the amount of emulsifiers used for stabilizing the

latexes, and cause several problems such as a reduction in water resistance or in

calcium ion stability in film applications [10, 11]. In contrast, organosiloxane/

polymer composite films have excellent water repellency, weather resistance and

thermal stability properties because the hydrolysis and condensation of Si(OR)3

groups result in the formation of a crosslinked silica network [12–15]. Polyacrylate

silicone core–shell particles have been synthesized using hydrophilic acrylic

monomers in the first stage and siloxanes in the second stage of the seeded emulsion

polymerization [16, 17]. It has been confirmed that the integrate performances of the

acrylic latexes can be enhanced by modifying the shells of the latex particles with

polysiloxane [18, 19]. Therefore, modifying the surface of SA latexes with

polysiloxane could be an effective approach to improve their physicochemical

properties.

In this paper, organosilicone surface modified styrene-acrylic (OSA) latexes in

the shell structure were synthesized through emulsion polymerization (the synthesis

mechanism of the OSA latexes was shown in Scheme 1), to improve the waterproof

property and the mechanical properties of the SA building materials. To decrease

the negative effect of the emulsifiers on the integrate properties of the SA latexes,

the influences of emulsifier type and dosage on the particle size, size distribution,

particle morphology, viscosity and waterproof property of the latexes were

systematically studied. The OSA latexes were mixed with cement powder and the

tensile strength and fracture elongation were used to evaluate the OSA/cement

building coating.

2374 Polym. Bull. (2013) 70:2373–2385

123

Experimental

Materials

Technical grade monomers, wn-butyl acrylate (BA) and styrene (St), were

purchased from Guangzhou Langri Chemical Co., Ltd., China. The monomers

were used without purification. c-Methacryloxypropyltrimethoxysilane (MPS) was

purchased by Shanghai Chemical Reagent Co., Ltd. The emulsifiers [nonyl phenol

polyoxyethylene ether (OP-10) and sodium dodecyl sulfate (SDS)], sodium

bicarbonate (NaHCO3), acrylamide (AM) and ammonia persulfate (APS) were

used as received. Doubly deionized water (DDI water) was used throughout the

work.

Preparation of latexes

The reagents for the preparation of the SA latexes and OSA latexes were given in

Table 1. In a typical synthesis, 0.4 g of SDS, 0.8 g OP-10 and 0.19 g NaHCO3 were

dissolved with 20-mL water in a round-bottom glass flask. Styrene (13.0 g), n-butyl

acrylate (33.0 g) and acrylamide (0.8 g) were added into the round-bottom glass

flask and stirred for 30 min for pre-emulsion. APS (0.35 g) was dissolved in 5-mL

DDI water.

To prepare SA latex, the reaction was carried out in a 250-mL four-necked

round-bottom glass flask, which was equipped with a reflux condenser, a mechanical

Scheme 1 The synthesis mechanism of the OSA latex

Polym. Bull. (2013) 70:2373–2385 2375

123

stirrer, a dropping funnel and a nitrogen gas inlet. NaHCO3 (0.06 g) and 20 mL of

DDI-water were added and stirred. When the NaHCO3 aqueous solution was heated

to 75 �C, 7.0 g pre-emulsion and 1/3 initiator solution were injected into the reactor.

After 10 min, the residual pre-emulsion mixed with the initiator solution was

dropwisely added into the reactor at the same time. After 4 h of feeding, the reaction

system was heated to 90 �C and stirred for another 1 h. The polymerization system

was cooled to 40 �C, and the pH value was adjusted to 7–8. For preparation of OSA

latex, after feeding the residual pre-emulsion and initiator solution for 3 h, MPS was

added into the pre-emulsion. After stirring, the above pre-emulsion was dropped

into the reaction system.

Preparation of OSA latex/cement composites

The OSA latexes or SA latex, cement (YaFei Co., Ltd.) and 400 mesh calcium

carbonate (YaFei Co., Ltd.) were mixed uniformly and casted into a mold. The

sample was dried for 14 days at room temperature. The recipes were shown in

Table 2.

Characterization

FTIR was used to characterize the chemical structures of the OSA latex films

(0.1 mm). A transmission electron microscope (TEM, Tecnai 12–120 kV, Philips)

was used to observe the morphology of OSA latexes. For sample preparation, a drop

Table 1 The synthesis recipes for preparation of the SA and OSA latex

Components SA latex OSA latex

H2O g-1 52 52

NaHCO3 0.25 0.25

ST 15 15

BA 33 33

APS 0.35 0.35

AM 0.8 0.8

SDS 1 1

OP-10 0.5 0.5

MPS / 0.5

Table 2 The recipes for preparation of the elastic building waterproof coatings

Components Emulsion:powder = 1.3:1 (wt.%) Emulsion:powder = 1:1 (wt.%)

Latex 56.50 50.00

Cement 21.75 25.00

400 Mesh calcium carbonate 21.75 25.00

2376 Polym. Bull. (2013) 70:2373–2385

123

of sample solution (1 mg mL-1 in distilled water) was placed on a 300-mesh copper

grid coated with carbon. Subsequently, the sample was dried and negatively stained

by a 2 % (w/w) phosphorus tungsten acid solution. Thermal gravimetric analysis

(TGA) measurements were performed on a NETZSCH STA 409PC thermogravi-

metric analyzer under the flow of anhydrous air from 25 to 800 �C at a heating rate

of 10 �C min-1 to measure the silicone content in the SA latex films. The mean

diameter and size distribution of the latexes were measured by a dynamic light

scattering (DLS) system (DLS-5022F). Before measurement, the latex samples were

diluted to an appropriate concentration.

Water absorbance property of the OSA latex film

Static immersion test of a latex film is considered as a standard method for

evaluating waterproof property of films. In brief, film samples were immersed in

distilled water at 25 �C. At specific time intervals, the samples were removed and

blotted with a piece of paper towel to absorb excess water on the surface. The

weight change was calculated by Eq. (1) and expressed as a function of time

Esw ¼We �Wo

Wo

� 100 % ð1Þ

where ESW is the water absorbance ratio of the film, We denotes the weight of the

film at equilibrium state and Wo is the weight of the dried sample.

Mechanical properties of the OSA latex films

The tensile tests were carried out according to ASTM D-256 using a Universal

Testing Machine (Hualong Co., Ltd., P. R. China) at a crosshead speed of

10 mm min-1. All measurements were repeated on at least five nominally identical

samples to obtain a statistical average.

Results and discussion

Characterization of the OSA latex films

Ftir

Figure 1 shows the FTIR spectra of the SA (a) and OSA (b) latex films. In the

spectrum of Fig. 1a, the peaks at 2,952 and 2,854 cm-1 are assigned to the

characteristic vibration of hydro-carbon bond. The peak at 1,735 cm-1 is assigned

to carbonyl (C=O) and the peaks at 761 and 675 cm-1 are attributed to ethyl (CH2),

methyl(CH3) and phenyl groups, respectively. In the spectrum of Fig. 1b, besides

the characteristic peaks of Fig. 1a, the band at 1,021 cm-1 is attributed to the Si–O

stretching modes, whereas the bands at 1,447 and 843 cm-1 are due to the Si–C

rocking normal vibrations [20]. These results suggest that the organosilicone has

been copolymerized onto SA latex through the unsaturated bond.

Polym. Bull. (2013) 70:2373–2385 2377

123

TGA and DTA

Figure 2a illustrates the pyrolytic behavior of the SA and OSA latex films. TGA is

widely used for the determination of the composition of inorganic/organic phases. In

order to exclude the formation of non-volatile oxidative degradation products that

may cause some uncertainties in calculations, TGA analysis was carried out in the

flow of anhydrous air. Figure 2 shows the curves of TGA and DTA of SA and OSA

latex film. In the TGA thermograms, the weight loss between 190 and 400 �C

corresponded to the thermal oxidation and pyrolysis of polymer. The silica content

in the composites could be measured to be 1.11 wt.%, which was estimated by the

balance value of 2.31, and 1.20 wt.% for OSA and SA latex film respectively.

The silica content was similar to that of the initial design, suggesting that the

organosilicone has high polymerization conversion. From the DTA curve, the

pyrolytic temperatures were determined to be 403 �C for the SA latex film and

408 �C for the OSA latex film. The increase of the pyrolytic temperature of the OSA

latex film indicated that the thermal stability of the SA latex could be improved

through copolymerization with organosilicone. The hydrolysis and condensation of

Si(OR)3 groups in organosilicone can construct a crosslinked silica network

immobilizing tightly on the surface of the latex particles.

DLS

Figure 3 and Table 3 show the diameters and size distributions of the SA and OSA

latexes depending on the organosilicone introduction and the ratio of the anionic to

non-ionic emulsifier with fixed total emulsifier amount. As shown in Fig. 3a, b, the

average diameters of the SA and the OSA latexes are 78.4 nm with a polydispersity

index of 0.015 and 89.3 nm with a polydispersity index of 0.029, respectively. This

result suggests that copolymerizing organosilicone on the shell of SA latex can

Fig. 1 ATR–FTIR spectra of the SA and OSA latex films. a SA, b OSA latex film

2378 Polym. Bull. (2013) 70:2373–2385

123

increase the size of the latex. The low value of the polydispersity indexes confirms

that the latex particles are dispersed uniformly. Figure 3b–d indicates that the latex

sizes increase and their distributions broaden with the decrease of the ratio of

anionic to non-ionic emulsifier. These results suggest that the type and quantity of

the emulsifiers can influence the size and distribution of the latexes.

TEM

Typical TEM micrographs of the SA and the OSA latexes depending on the ratio of

anionic to non-ionic emulsifier are shown in Fig. 4. Both the SA and the OSA latexes have

regular spherical morphology and uniform size distributions (Fig. 4a [anionic:nonionic

(wt.%) = 2:1, SA] and b [anionic:nonionic (wt.%) = 2:1, OSA]), but the size increased

and the size distributions became broaden when the ratio of the anionic to non-ionic

0 100 200 300 400 500 600 700 800 900

0

20

40

60

80

100

Temperature /

Mas

s/%

OSA SA 2.31

1.32

a

340 360 380 400 420 440 460

-30

-25

-20

-15

-10

-5

0

DT

G/(

%/m

in)

Temperature /

OSA SA

403

408

b

Fig. 2 TGA and DTA curves of the SA and OSA latex films. a TGA, b DTA

Polym. Bull. (2013) 70:2373–2385 2379

123

emulsifier decreased (Fig. 4c [anionic:nonionic (wt.%) = 1:1, SA] and d [anionic:non-

ionic (wt.%) = 1:1, OSA]), which was consistent with the DLS results (Table 3).

Rheology

Viscosity of the SA latexes is an important factor for their applications in building

materials. The variation of the steady state viscosity (g) as a function of the shear

rate ð _cÞ is presented in Fig. 5. The viscosity of the OSA latex evidently decreased

when the relative amount of the non-ionic emulsifier increased. It suggests that

latexes with bigger size and broaden size distribution have much lower viscosity

a b

c d

Fig. 3 Diameters and diameter distributions of the SA and OSA latexes. a Anionic:non-ionic(wt.%) = 2:1, SA latex; b anionic:non-ionic (wt.%) = 2:1, OSA latex; c anionic:non-ionic (wt.%) = 1:1,OSA latex; d anionic:non-ionic (wt.%) = 1:2, OSA latex

Table 3 Results of DLS analysis

Ratio of emulsifiers Mean diameter PDI

Anionic:non-ionic (wt.%)

2:1 (a) 78.4 0.015

2:1 (b) 89.3 0.029

1:1 (c) 130.7 0.093

1:2 (d) 315.2 0.240

2380 Polym. Bull. (2013) 70:2373–2385

123

according to the TEM and DLS results. The viscosity of the OSA latex decreased

only a little under throughout shear rate when comparing with that of the SA latex

with the same ratio of anionic to non-ionic emulsifier. These results suggest that the

components of the emulsifiers have more significant influence on the viscosity of the

latexes than the components and structure of the latexes.

Formation mechanism of the OSA latex

The formation mechanism of the OSA with silica-containing shell is a size

controlled core–shell seed emulsion polymerization (Scheme 1). It is proposed that

the seed latexes are initially formed via the formation of the SA copolymers. After

that styrene and acrylic diffuse into the seed latexes and polymerize on the seed

latex surface to form SA core before organosiloxane (MPS) addition. When MPS is

added into the pre-emulsion, polymerization takes place on the surface of the SA

Fig. 4 TEM morphologies of the SA and OSA latexes. a Anionic:non-ionic (wt.%) = 2:1, SA latex;b anionic:non-ionic (wt.%) = 2:1, OSA latex; c anionic:non-ionic (wt.%) = 1:1, OSA latex;d anionic:non-ionic (wt.%) = 1:2, OSA latex

Polym. Bull. (2013) 70:2373–2385 2381

123

core, forming organosilicone modified SA shells. Hydrolysis and condensation of

the Si(OR)3 groups in the organosilicone happen simultaneously and form

crosslinked silica network in the shells [21], which can improve the thermal

stability, water resistant property and toughness of the latex film. This core–shell

emulsion polymerization provides a novel material with outstanding performance

combining the unique properties of both SA and organosiloxane materials.

The waterproof properties of the OSA latex film

Water uptake

The water absorbance and the water contact angle of the OSA latex film are shown

in Fig. 6 and Table 4. The water absorbance of the SA and the OSA latex films after

48 h were 5.63 % ± 0.11 (w/w) and 1.70 % ± 0.09 (w/w), and increased to

9.15 % ± 0.89 (w/w) and 3.5 % ± 0.07 (w/w) after 7 days (Fig. 6; Table 4). The

water contact angles were 60.3 ± 0.5� and 73.7 ± 0.3� for the SA and OSA latex

films, respectively. Generally, the surface water contact angle of measurements is

surface-sensitive, responding to the outermost monolayer of surface. The increase of

contact angle could be attributed to the low-energy of organosiloxane. The OSA

latex film has much lower water absorbance than the SA film due to the formation of

cross-linked structure with the shell layer modified with organosiloxane (KH-570),

thus much better waterproof property.

Mechanical properties

The tested values of the tensile strength and elongation of the silicone–styrene acrylic

elastic building coatings are listed in Table 5. rb and d represent the tensile strength

and the elongation of the elastic building coating material (latex:powder = 1.3:1

w/w), respectively; rb* and d* the values of the elastic building coating material

Fig. 5 The viscosity of the SA and OSA latexes

2382 Polym. Bull. (2013) 70:2373–2385

123

(latex:powder = 1:1 w/w), respectively. From Table 5, it can be found that the

tensile strength and the elongation of the OSA elastic building coating material are

better than those of the SA elastic building coating material and meet the China

Industry Standard (JC/T894-2001). This could be due to the enhancement of the

compatibility on the interface between the OSA latex and the cement powder

according to the ‘‘similar dissolve mutually’’ theory.

Conclusions

In this study, OSA latexes with shell containing organosilicone for waterproof

coating were successfully prepared by core–shell emulsion polymerization. The size

Fig. 6 The water absorbance of the SA and OSA latex films

Table 4 The water absorbance of the SA and OSA latexes [anionic:non-ionic (wt.%) = 1:2]

Sample After 48 h After 7 days Water contact angle

SA latex film 5.63 ± 0.11 % 9.15 ± 0.89 % 60.3 ± 0.5

OSA latex film 1.70 ± 0.09 % 3.5 ± 0.07 % 73.7 ± 0.3

Table 5 Tensile strength and elongation of the elastic waterproof building coating made from SA or

OSA latex and cement powder [anionic:non-ionic (wt.%) = 1:2]

Sample SA latex OSA latex

Tensile strength, rb (MPa) 1.01 2.9

Elongation, r (%) 185 202.0

Tensile strength, rbł (Mpa) 0.9 3.8

Elongation, rł (%) 74.5 94.0

rb and d Emulsion: powder = 1.3:1 (w/w)

rbł and dł Emulsion: powder = 1:1 (w/w)

Polym. Bull. (2013) 70:2373–2385 2383

123

and its distribution can be well controlled by emulsifier type and dosage, affecting

the viscosity of the resulting latex. The OSA latex film has higher water contact

angle and lower water absorbance in comparison with the SA latex film, suggesting

better waterproof property. The building coating made of the OSA latex and cement

powder has better tensile strength and fracture elongation than that made of the SA

latex and cement powder. This enhancement could be due to the formation of the

silica network in the shells of the latexes and the improvement of the compatibility

between the latexes and the cement powder.

Acknowledgments This research was supported by a National Natural Science Foundation of China

(No. 51073133), a China Jiangsu Provincial Natural and Scientific Grant (Project SBK200930208), China

Jiangsu Provincial Innovative Grant (Project SBC200910282), and was supported by Jiangsu Province,

Project No. 08KJA430003 (China).

References

1. Deleuil M (1979) Gypsum construction parts. Chem Abstr 91:145114d

2. Bijen JC (1992) Polymer-modified glass fibre reinforced gypsum. Mater Struct 25:107–114

3. Murayama S, Toko A (1976) High-strength gypsum products with good waterproofness. Chem Abst

84:78793q

4. Zou MX, Wang SJ, Zhang ZC, Ge XW (2005) Preparation and characterization of polysiloxane-

poly(butyl acrylate-styrene) composite latices and their film properties. Eur Polym J 41:2602–2613

5. He WD, Cao CT, Pan CY (1996) Formation mechanism of silicone rubber particles with core–shell

structure by seeded emulsion polymerization. J Appl Polym Sci 61:383–388

6. He WD, Cao CT, Pan CY (1996) Study of the preparation of silicone rubber particles with core–shell

structure by seeded emulsion polymerization. Polym Int 39:31–36

7. Kan CY, Liu DS, Kong XZ, Zhu XL (2001) Study on the preparation and properties of styrene–butyl

acrylate–silicone copolymer lattices. J Appl Polym Sci 82:3194–3200

8. Colak A (2001) Characteristics of acrylic latex-modified and partially epoxy-impregnated gypsum.

Cem Concr Res 31:1539–1547

9. Zaragoza-Contreras EA, Navarro-Rodrıguez D (2003) On the role of an unconventional rigid rodlike

cationic surfactant on the styrene emulsion polymerization. Kinetics, particle size and particle size

distribution. Polymer 44:5541–5546

10. Chaiyasat A, Kobayashi H, Okubo M (2007) Incorporation of nonionic emulsifier inside methacrylic

polymer particles in emulsion polymerization. Colloid Polym Sci 285:557–562

11. Chaiyasat A, Yamada M, Kobayashi H, Suzuk T, Okubo M (2008) Incorporation of nonionic

emulsifiers inside styrene–methacrylic acid copolymer particles during emulsion copolymerization.

Polymer 49:3042–3047

12. Lin MT, Chu FX, Guyot A, Putaux JL, Lami EB (2005) Silicone–polyacrylate composite latex

particles. Particles formation and film properties. Polymer 46:1331–1337

13. Dai Q, Zhang ZC, Wang F, Liu J (2003) Preparation and properties of polydimethylsiloxane/poly-

acrylate composite latex initiated by 60Co c-ray irradiation. J Appl Polym Sci 88:2732–2736

14. Marcu I, Daniels ES, Dimonie VL, Hagiopol C, Roberts JE, El-Aasser MS (2003) Incorporation of

alkoxysilanes into model latex systems: vinyl copolymerization of vinyltriethoxysilane and n-butyl

acrylate. Macromolecules 36:328–332

15. Ren SZ, Sun GQ, Li CN, Liang ZX, Wu ZM, Jin W, Qin X, Yang XF (2006) Organic silica/Nafion

composite membrane for direct methanol fuel cells. J Membrane Sci 282:450–455

16. Kong XZ, Kan CY, Yuan Q (1996) Preparation of polyacrylate–polysiloxane core–shell latex par-

ticles. Polym Adv Technol 7:888–890

17. Kan CY, Kong XZ, Yuan Q, Liu DS (2001) Morphological prediction and its application to the

synthesis of polyacrylate/polysiloxane core/shell latex particles. J Appl Polym Sci 80:2251–2258

18. Cui XJ, Zhong SL, Wang HG (2007) Emulsifier-free core–shell polyacrylate latex nanoparticles

containing fluorine and silicon in shell. Polymer 48:7241–7248

2384 Polym. Bull. (2013) 70:2373–2385

123

19. Kan CY, Kong XZ, Yuan Q, Liu DS (2001) Morphological prediction and its application to the

synthesis of polyacrylate/polysiloxane core/shell latex particles. J Appl Polym Sci 80:2251–2258

20. Wu YM, Duan HD, Yu YQ, Zhang CG (2001) Preparation and performance in paper coating of

silicone–modified styrene–butyl acrylate copolymer latex. J Appl Polym Sci 79:333–336

21. Ha JW, Park IJ, Lee SB, Kim DK (2002) Preparation and characterization of core–shell particles

containing perfluoroalkyl acrylate in the shell. Macromolecules 35:6811–6818

Polym. Bull. (2013) 70:2373–2385 2385

123