A new core–shell typefluorinated acrylic and siliconated polyurethane hybrid emulsion
Jia Bing Dai,Xing Yuan Zhang,Jing Chao,
Chen Yan Bai
ÓFSCT and OCCA2007
Abstract A novel core–shell typefluorinated acrylic and siliconated polyurethane(FSiPUA)hybrid emul-sion was prepared by seeded emulsion polymerization using siliconated polyurethane(SiPU)as a seed and forming the structure with SiPU as a shell and the copolymer of butyl acrylate(BA)with2,2,2-trifluoro-ethylmethacrylate(TFEMA)as a core.SiPU was synthesized using isophorone diisocyanate(IPDI), polytetramethylene ether glycol(PTMG),polypro-pylene glycol(PPG),dihydroxybutyl-terminated poly-dimethylsiloxane(PDMS),dimethylol propionic acid (DMPA),1,6-hexanediol(HDO)and triethylamine (TEA).The contents of siloxane andfluorine were determined according to the feed ratio.Fourier trans-form infrared spectroscopy(FTIR)was used to identify the chain structure of SiPU and FSiPUA.Investigation of transmission electron microscopy(TEM)confirmed the core–shell structure of FSiPUA emulsion and gave the particle size at about50nm.The measurement results of water contact angles and the solvent absorp-tions in water and n-octane for curedfilms showed that the water and the
oil repellency for FSiPUA had been improved significantly with a suitable content of fluorine and siloxane.
Keywords Core–shell,Fluorinated acrylate, Siliconated polyurethane Introduction
Aqueous acrylic–polyurethane dispersions have become one of the major types of materials used in the coating,paint,and adhesive industries due to excellent properties and environmental advantages.1–7Some properties for curedfilm,however,such as water and oil resistances need to be improved further for this type of polyurethane.Recently,some work has been done on the synthesis and characterization of siliconated poly-urethane(SiPU),8–11andfluorinated polyurethane (FPU),12–15respectively.SiPU demonstrates superior flexibility,resistance to humidity,thermal stability and resistance to solvent and acid/base conditions,but poor oil resistance.Fluorinated polymers possess a whole range of very interesting bulk and surface properties, such as excellent environmental stability,water and oil repellency,low coefficient of friction,biocompatibility, excellent thermal stability and chemical resistance,as well as low interfacial free energy.The price offluori-nated monomers is rather high,however,which leads to a limitation of large-scale use for FPU products.
In this paper,we report the synthesis of a novel core–shell type FSiPUA hybrid emulsion in which fluori
ne and siloxane were both incorporated into the polymer chains.Through the controlling of suitable feed ratios and the content of Si and F embedded in the chain,the resulting FSiPUA proved to possess not only good water and oil repellency,but also cost less to produce.The prepared emulsion can be applied to the coating and the paint industrially.
reactor core教程Experimental
Materials
Polytetramethylene ether glycol(PTMG,M n=1000, Mitsubishi Chemical Corporation),polypropylene
J.B.Dai,X.Y.Zhang(&),J.Chao,
C.Y.Bai
Department of Polymer Science and Engineering,
University of Science and Technology of China,
Hefei230026,P.R.China
e-mail:zxym@ustc.edu
J.B.Dai
Institute of Chemistry and Chemical Engineering,
Anhui University,Hefei230039,P.R.China
C.Y.Bai
e-mail:chybai@mail.ustc.edu
DOI10.1007/s11998-007-9042-z
283
glycol(PPG,M n=2000,Tianjin Petrochemical Co.,Ltd.),and dihydroxybutyl-terminated poly-dimethylsiloxane(PDMS,M n=2000,self-made)were vacuum-distilled before use.Dimethylol propionic acid (DMPA)and isophorone diisocyanate(IPDI,Aldrich Chemical Company),butyl acrylate(BA),and 1,6-hexanediol(HDO,Shanghai Chemical Reagent Co.,Ltd.),and2,2,2-trifluoroethylmethacrylate(TFE-MA,H
arbin Xeogia Fluorine-Silicon Chemical Co., Ltd.)were used as received.Triethylamine(TEA, Shanghai Chemical Reagent Co.,Ltd.)was used as neutralization agent.The initiator,ammonium persul-fate(APS,Shanghai Chemical Reagent Co.,Ltd.),was purified with heating.
Synthesis of SiPU and FSiPUA
The hybrid emulsion with core–shell structure was prepared according to the procedure shown in Fig.1. As a seed emulsion and a comparison,SiPU was synthesized by a prepolymer mixing process and acetone process using IPDI,PTMG,PPG,PDMS, DMPA and HDO.IPDI,PTMG,PPG,and PDMS werefirst added into a dry vesselfitted with a reflux condenser,a mechanical stirrer,and a thermometer according to the mass ratio of PDMS and IPDI ranging from0/100to30/70(the mass ratio of PTMG and PPG also changed with that of PDMS and IPDI).The prepolymerization of polyurethane was carried out at 90°C under N2atmosphere for2h until the NCO content reached the theoretical value(Prepolymer1). After being diluted with a suitable amount of acetone, the chain extenders HDO and DMPA were added into the system and reacted at70–80°C for5h.Then,TEA was used as a neutralization agent and reacted with the carboxylic group in the side chain of Prepolymer2. Next,the deionized water was added and the solution was emulsified by high-speed stirring.After removal of acetone from the emulsion by rotary vacuum evapo-ration,aqueous dispersions SiPU with different sil-
oxane content of0,1.0%,2.6%,4.0%,5.8%,8.0%, 12.1%,16.0%,and20.0%were prepared.These samples were named as SiPU0,SiPU1,SiPU2,SiPU3, SiPU4,SiPU5,SiPU6,SiPU7,and SiPU8,respectively.
Anionic FSiPUA emulsions with different siloxane content but the samefluorine content(A-series), and those with differentfluorine content but the same siloxane content(B-series)were prepared by copolymerization of suitable amounts of BA and
284
TFEMA in the SiPU dispersions via seeded emulsion polymerization.The compositions of core–shell FSi-PUA emulsions are shown in Table1.One hundred grams of said polyurethane emulsion(solid content of 25wt%),12.5g of distilled water,and some emulsifier were added to a reactor,and the system was stirred at high speed to form a stable emulsion.The mixture of BA,TFEMA and APS aqueous solution was then added to the reactor.The reaction was carried out at 85°C for about3h.After the pH value of the emulsion was adjusted to9with ammonia,the emulsion was cooled down to room temperature and a core–shell type of FSiPUA was synthesized.The resulting product was a stable dispersion with solid content of about 30%,which was composed of40wt%polyurethane and60wt%acrylic polymer.
Sample preparation and characterization
A thin latexfilm(thickness less than20l m)for FTIR
analysis wasfixed directly on a sample frame and measured in the range from4000to400cm–1by a FTIR spectrometer(MAGNA-IR750,Nicolet Instru-ment Co.,U.S.).
The size and morphology of emulsion particles were characterized on a transmission electron microscope (TEM,JEM-100SX,Japan)using2%aqueous phos-phortungstic acid as a staining agent.
Thefilm samples for contact angle measurement and investigation of water resistance(WR)and oil resis-tance(OR)properties were prepared by casting the aqueous dispersions on a leveled PTFE surface and curing at room temperature for5days,and then keeping in an oven at50°C for2days in a vacuum. The contact angle of water droplets on the curedfilm was measured with a contact angle goniometer (JC2000C1,PowereachÒ,Shanghai Zhongchen)using the sessile-drop method at25°C,and the reported results were the mean values of three replicates.The WR and OR properties of the curedfilm were characterized by the solvent absorptions in water and in n-octane,respectively.The weighed curedfilm was dipped in deionized water or n-octane at room temperature for24h.The solvent absorption was calculated using the formula:
Solvent absorptionðwt%Þ¼ðW1ÀW0Þ=W0Â100% where W0and W1were thefilm weights before and after absorbed water/n-octane,respectively.
Results and discussions
The structure of SiPU and FSiPUA by FTIR
The chain structure of SiPU and FSiPUA was confirmed by FTIR analysis.As an example,the FTIR spectra of SiPU0,SiPU4,SiPU6and SiPU8are shown in Fig.2.The absorption peaks of typical polyurethane at3330cm–1[m(NH)],2855–2955cm–1[m(CH2)and m(CH3)],1720–1780cm–1[m(C=O)],1540cm–1 [d(NH)]and1110cm–1[m(C–O–C)]can be seen clearly in the spectra.Compared with the pure poly-urethane sample,SiPU0(the content of siloxane and
Table1:Compositions of core–shell FSiPUA emulsions
Sample code A-series(fixedfluorine content of15%)Sample code B-series(SiPU6as a seed) Seed PDMS,%PDMS,%Fluorine,% A0SiPU00B1  5.1220
A1SiPU10.42B2(A6)  5.1215
A2SiPU2  1.06B3  5.1210
A3SiPU3  1.72B4  5.125
A4SiPU4  2.48B5  5.120
A5SiPU5  3.48
A6SiPU6  5.12
A7SiPU7  6.65
A8SiPU88.36
J.Coat.Technol.Res.,4(3)283–288,2007
285
fluorine is zero in FSiPUA),the peaks at1259cm–1 [m(CH3)in Si–CH3],1026cm–1[m(Si–O)]and805cm–1 (CH3–Si rocking)can be clearly detected in the spectra of SiPU,indicating that siloxane groups had been successfully introduced into the polyurethane chain.In addition,Fig.2also shows that the strength of absorption peaks at1259,1026and805cm–1increases markedly with increasing the content of PDMS.
Figure3shows the FTIR spectra of SiPU7and some FSiPUA samples.In the spectra of FSiPUA,the characteristic absorption of C=C bond at1640cm–1 disappeared,indicating that BA and TFEMA mono-mers had been copolymerized.The absorption peak of C–F bond at658cm–1(CF3rocking),1171cm–1 [m s(CF3)+d(CF3)]and1287cm–1[m a(CF3)+c(CF3)] demonstrated further that TFEMA had been incor-porated into the polymer chains.In addition,a distinct absorption peak at961cm–1presenting the absorption of C–H(CH2CF3)also appeared in the spectra of FSiPUA.Compared to the pure PU and SiPU samples, the absorption peak of m C=O in FSiPUA moved to the region of higher wave number(from1718to1748cm–1), showing a strong interaction around C=O group in FSiPUA.The morphology of emulsion particles by TEM
The morphology and size of emulsion particles were observed by a TEM.Figure4shows the TEM images of Sample A6under two magnifications.TEM photo-graphs indicated that the particles were sph
erical and the average particle size was around50nm.The boundary between core and shell regions could be well-distinguished under a higher magnification of 2.0·105.Since the emulsion was aqueous and poly-urethane had hydrophilic groups–COOH,the shell region was occupied by SiPU while the core region was hydrophobicfluorinated polyacrylate.3The morphol-ogy and size of emulsion particles for other samples were similar to that of Sample A6.
The water contact angle analysis
The water contact angle of thefilm for SiPU and FSiPUA was measured by the sessile-drop method. Figure5shows the dependency relationships between the contact angle of SiPU,FSiPUA and siloxane content.It was clearly observed that the contact angle of SiPU increased with increasing siloxane content. Generally,the surface water–air contact angle mea-surements are more surface-sensitive,probably responding to the outermost monolayer of the surface. The increase in contact angle could be attributed to the surface activity of hydrophobic siloxane.The contact angle became nearly constant,however,when the content of siloxane increased to about10%,indicating that the siloxane surface enrichment had a limited value.
Figure5also shows that the contact angle of FSiPUA was higher than that of SiPU when the siloxane c
ontent was lower than2.8%,yet it was lower when the siloxane content was higher than2.8%.This may be explained by the lower PDMS distribution density on the surface in smaller concentrations and the accessorial effect of afluorinated segment that migrated to the surface from the core to shield the polymer chain with high surface energy,and substan-tially lowered the surface free energy.When the siloxane content increased,there was enough siloxane
Fig.4:TEM Photographs of sample A6.Staining acid:2%aqueous phosphortungstic acid J.Coat.Technol.Res.,4(3)283–288,2007
286
at the surface,but due to their low surface free energy, somefluorinated segments still migrated to the surface and replaced the siloxane.The water repellency of fluorinated segments with short chains was not very good and even worse than the siloxane.As a result,the contact angle of FSiPUA was a little lower than that of SiPU when the siloxane content was high.It should be noted that when the contact angle was up to about90°, the siloxane content in FSiPUA was lower than that in SiPU.
The WR and OR properties
Water and oil resistances of curedfilm for SiPU and FSiPUA were investigated by the solvent absorption in water and in n-octane,respectively.As shown in Figs.6 and7,the relationship curves between the content of siloxane andfluorine and solvent absorption exhibited some differences in a wide range.Compared with SiPU,FSiPUA demonstrated much lower water and oil solvent absorptions due to the common effect of hydrophobic siloxane chains and amphiphobicfluori-nated chains.Figure6shows that the solvent absorp-tions of SiPU and FSiPUA in water decrease with increasing the content of PDMS[SiPU and FSiPUA (A-series)]andfluorine[FSiPUA(B-series)].For SiPU,the solvent absorption decreases from3.4%to 2.6%as the content of PDMS increases from0%to 20%.For FSiPUA,however,the solvent absorption is lower though the content of PDMS is less than that of SiPU due to the introduction offluorine.The linear relationship shown in Fig.6for FSiPUA(B-series)also provides information that increasing the content of fluorine can improve the WR property more efficiently.
Figure7shows the solvent absorptions of SiPU and FSiPUA in n-octane.In opposition to the WR pro-perty,the solvent absorptions in n-octane for SiPU and FSiPUA(A-series)increase as the siloxane content increases,and the value of solvent absorption is much higher than that in water.For FSiPUA(B-
series), however,the solvent absorption decreases significantly from26.5%to4.7%as the content offluorine increases from0%to20%.These phenomena suggest the influence of siloxane andfluorinated component on the solvent absorption in the core–shell structure and may be explained by the morphology and the structure of thefilm surface.
When the amphiphobicfluorinated components existed in the core phase,relatively fewfluorinated components were placed on thefilm surface.In addition,the siloxane in the shell was hydrophobic but oleophilic,which was the main factor when the fluorine content was relatively small.Therefore,the solvent absorptions of SiPU and FSiPUA in water(shown in Fig.6)decrease,while the solvent
J.Coat.Technol.Res.,4(3)283–288,2007
287

版权声明：本站内容均来自互联网，仅供演示用，请勿用于商业和其他非法用途。如果侵犯了您的权益请与我们联系QQ:729038198，我们将在24小时内删除。