Characterisation and Properties of Fluorinated Acrylic Latex Prepared With Mixed Surfactants of SDS and APG

Transcription

1 Characterisation and Properties of Fluorinated Acrylic Latex Prepared With Mixed Surfactants of SDS and APG Characterisation and Properties of Fluorinated Acrylic Latex Prepared With Mixed Surfactants of SDS and APG Wei Jiang, Wen Li, and Lijun Chen School of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou , China Received: 22 October 2013, Accepted: 31 January 2014 Summary The nonionic emulsifier of OP-10 is often used in preparing the latex. OP-10 belongs to a type of NPEOs. However, NPEOs are bioaccumulative and persistent in the environment while nonylphenol, the breakdown product of NPEs, is an endocrine disruptor. Therefore, the EU Commission has recommended implementing a risk reduction strategy, which foresees the ban of all applications leading to direct emissions to waste water and strict emission controls for all other technical processes using NPEOs as surfactants. The aim of the research is to study the possibility that OP-10 is replaced by APG to prepare the fluorinated acrylic latex. The fluorinated acrylic latex was prepared successfully via semicontinuous seeded emulsion polymerization of butyl acrylate (BA), methyl methacrylate (MMA) and hexafluorobutyl methacrylate(hfma) in water phase initiated with potassium persulfate (KPS) and emulsified with the aid of mixed surfactants of sodium dodecyl sulfonate (SDS) and alkyl polyglucosides (APG). The structure of the resultant latex is confirmed by Fourier transform infrared spectroscopy (FTIR) spectrum. The influences of the amount of APG on the properties of the resultant latex and its film were investigated in detail. Results show that the particle size is decreased with the increase amount of APG. However, the calcium ion stability of the latex is increased with the increase of amount of APG. Keywords: Fluorinated acrylic latex; Emulsion polymerization; APG; Properties Corresponding author: Lijun Chen. chenlj@zjut.edu.cn. Tel: Smithers Rapra Technology, 2014 Polymers from Renewable Resources, Vol. 5, No. 2,

2 Wei Jiang, Wen Li, and Lijun Chen INTRODUCTION Fluorinated acrylate latex has the good performance of both acrylate polymer latex and fluoropolymer. It possesses the hydrophobic, oleophobic, and antifouling surface behavior. It has been widely used in the field of coatings, fabric finish, leather, and packing [1-4]. Presently, acrylic monomers and fluorine monomers are extensively used to produce latex, and usually two or more monomers are copolymerized via a seeded semi-batch approach to provide lattices with desirable properties. The monomers are often emulsified with the mixture of anionic and nonionic emulsifiers, such as SDS/OP-10 [5, 6] or LAS/OP-10 [7] or SDBS/OP-10 [8]. The nonionic emulsifier of OP-10 belongs to a type of NPEOs. However, NPEOs are bioaccumulative and persistent in the environment while nonylphenol, the breakdown product of NPEs, is an endocrine disruptor. Therefore, the EU Commission has recommended implementing a risk reduction strategy, which foresees the ban of all applications leading to direct emissions to waste water and strict emission controls for all other technical processes using NPEOs as surfactants [9]. Alkyl polyglycosides (APG) are nonionic surfactants which are synthesized from renewable raw materials such as fatty alcohol and sugars [10, 11]. They present low toxicity, excellent biodegradability and outstanding properties [12, 13]. APG have received considerable research interest and have been used in many fields in recent years [14-18]. However, the fluorinated acrylic latex prepared with APG has not been reported previously. The main objective of this study was to prepare the fluorinated acrylic latex emulsified without OP- 10. This paper tried to prepare fluorinated acrylic latex emulsified with SDS and APG via semi-continuous seeded emulsion polymerization. The emphasis is put in the present work on the characterisation of the resultant latex and the influence of the amount of APG on the properties of the resultant latex. EXPERIMENTAL Materials Butyl acrylate (BA) and methyl methacrylate (MMA) were obtained from Shanghai Chemical Reagents Supply Procurement of Five Chemical Plants (China) and were distilled under reduced pressure prior to polymerization. Hexafluorobutyl methacrylate (HFMA) was supplied by Shanghai Haorui Chemical Co., Ltd (China). Alkyl polyglucosides (APG1214) were obtained from Guangzhou Meike Chemical Co., Ltd (China). Sodium dodecyl sulfonate (SDS) was purchased from Shanghai Yingpeng Chemical Reagent Co., Ltd 62 Polymers from Renewable Resources, Vol. 5, No. 2, 2014

3 Characterisation and Properties of Fluorinated Acrylic Latex Prepared With Mixed Surfactants of SDS and APG (China). Potassium persulfate (KPS) was bought from the Second Chemical Reagent Factory in Yixin (China). The water used in this experiment was distilled followed by deionization. Preparation of Latexes The fluorinated acrylic latex was synthesized by the semi-continuous seeded emulsion polymerization technique. The seeded emulsion polymerization was carried out in a 250 ml four-neck flask equipped with a mechanical stirrer, a reflux condenser and two dropping funnels and heated with the water bath. In the study, the mixed monomers were composed of g of BA, 5.00 g of MMA and 5.00 HFMA. The concentration of KPS aqueous solution was 0.30 g of KPS that was dissolved in the g of deionised water. First, all the mixed emulsifier of SDS and APG and NaHCO 3 was introduced into the four-neck flask charged with 40 ml of deionized water. Then the flask was placed in a water bath at 80 C with a stirring rate of 200 rpm. After all of the mixed emulsifier and NaHCO 3 was dissolved in the deionised water completely, 5.00 g of mixed monomers and 1.50 g of the KPS aqueous solution were dropped into the above flask within 15 min via two different dropping funnels at the same time. The reaction was maintained for another 15 min. Then the seeded emulsion was obtained. Then the mixture of the residual monomer and the rest of the KPS aqueous solution were fed into the flask containing seeded latex under starved-feed addition simultaneously within 3.0 h by two dropping funnels. When the mixed monomers and KPS aqueous solution were completely fed, the temperature was raised to 90 C and maintained for another 45 min. Finally, the latex was cooled to 40 degrees and its ph was adjusted to 8.0 with ammonia water and filtered. Thus, the fluorinated acrylic latex was obtained. Characterization Fourier infrared (FTIR) spectrometric analyzer (Thermo Nicolet AVATAR370, USA) was used to analyze the chemical structures of the latex films. Conversion percentage of the mixed monomers was calculated according to the following equation: w 3 w w 2 0 w w1 w 4 x% = 0 100% w 5 Polymers from Renewable Resources, Vol. 5, No. 2,

4 Wei Jiang, Wen Li, and Lijun Chen where X is the conversion ratio; W 0 is the weight of weighing bottle; W 1 is the weight of the latex and bottle; W 2 is the weight of the dried latex and bottle; W 3 is the weight of the total materials in the reactor; W 4 is the weight of the total non-volatile ingredients in the recipe; W 5 is the weight of the total monomer in the recipe. The average particle size of the latexes was determined by Zetatrac dynamic light scattering detector (Microtrac Limited Corporation, USA) at 25 C. The power and the wavelength of the diode laser used in the dynamic light scattering measures were 3mV and 780 nm, respectively. The differential scanning calorimetry (DSC Q100, USA) was applied to determine the glass transition temperature (Tg) of the film of the latex. The heating temperature was in the range from -30 to 60 degrees. The heating rate was 10 /min. RESULTS AND DISCUSSION FTIR and DSC Curve of Film FTIR of the film of the fluorinated acrylic latex, which is emulsified with the aid of mixed surfactants of SDS and APG, is given in Figure 1. In Figure 1, 2958 cm -1, and 2874 cm -1 were the characteristic stretching peaks of C H(CH 3,CH 2 ), and 1728 cm -1 was stretching vibration of C=O, and 1452 cm -1 was bending vibration peak of CH 2, and 1384 cm -1 was the flexural vibration peak of C-H in CH 3, and 1234 cm -1 was the stretching vibration of C-F bond. 1161cm -1 was the stretching vibration peak of C-H. 839 cm -1 was the stretching vibration absorption peak of C=O in the acrylic group. 755 cm -1 was the deformation vibration absorption peak of C-F. The stretching vibration of C=C disappeared within the range of 1500 and 1700 cm -1. The FTIR spectrum shows that all the mixed monomers take part in the copolymerization reaction and the latex has been prepared successfully. In addition, DSC curve of the film is presented in Figure 2. In Figure 2, it can be seen that the latex has only one glass transition temperature which shows that the latex is a type of random copolymer and the consistency among the chain is fairly good [19]. This also confirms that the fluorinated acrylic latex has been prepared successfully. Conversion Influence of the amount of APG on the conversion is shown in Figure 3. In Figure 3, it can be found that the conversion percentage of mixed monomers is increased with the increase of the amount of APG when it is lower than 4%. In addition, Figure 2 also indicates that the conversion percentage is 64 Polymers from Renewable Resources, Vol. 5, No. 2, 2014

5 Characterisation and Properties of Fluorinated Acrylic Latex Prepared With Mixed Surfactants of SDS and APG Figure 1. FTIR of film Figure 2. DSC of film decreased with the increase of the amount of APG when it is more than 4%. This phenomenon can be explained by the following facts. The solubilization is more significant and the more of micelles is formed when the emulsifier concentration is increased, which leads to the increased number of latex Polymers from Renewable Resources, Vol. 5, No. 2,

6 Wei Jiang, Wen Li, and Lijun Chen particles. Thus, the polymerization rate is increased and the conversion of the mixed monomers is increased. However, the latex particles are completely covered by an emulsifier, and the free radical of initiator is difficult to enter inside the reaction of latex particles, which results in incomplete reaction and low conversion, when the amount of APG is increased further [20]. Figure 3. Effect of amount of APG on conversion Particle Size of Latex The effect of the amount of APG on the average particle size of latex is given in Figure 4. Figure 4 shows that the average particle of latex is decreased with the increase amount of APG. It may be related to the nucleation mechanism of emulsion polymerization. The nucleation mechanism of the emulsion prepared with emulsifiers is the mechanism of micelle nucleation, i.e. the emulsifiers are formed to micelles and the site of the emulsion polymerization is formed after the part of the micelles obtains the free radicals decomposed from the initiator. Usually, the number of the micelles and the probability of forming the reaction center are almost constant when the amount of emulsifiers is fixed. Thus, the average particle size of latex in decreased with the increase in the amount of APG. There are more chances to form more micelles when the amount of APG is increased further. 66 Polymers from Renewable Resources, Vol. 5, No. 2, 2014

7 Characterisation and Properties of Fluorinated Acrylic Latex Prepared With Mixed Surfactants of SDS and APG (a) (b) (c) (d) Figure 4. Effect of APG amount on average particle size of latex( (a): m(apg) = 0 g, Mv = 76.8 nm; (b) m(apg) = 0.20 g, Mv = 55.2 nm; (c) m(apg) = 0.50 g, Mv = 50.5 nm; (d): m(apg) = 0.70 g, Mv = 49.9 nm) Polymers from Renewable Resources, Vol. 5, No. 2,

8 Wei Jiang, Wen Li, and Lijun Chen Stability of Latex Influence of the amount of APG on the stability of latex is shown in Table 1. Table 1 indicates that all the prepared latexes have good mechanical stability which is tested by the centrifugal machine with the rotation speed of 3000 r.min -1. This may be explained by the fact that the emulsion particles are covered with static charges when the anionic emulsifier is used, which can prevent the ions from gathering effectively. In addition, the ionic stability of latex is of much importance when the latex is mixed with other materials containing electrolytes. Otherwise, the latex becomes useless due to de-emulsification. Table 1 also indicates that the ionic stability of the latex is increased with the increase in the amount of APG. This may be caused by the fact that the electrostatic or steric stabilization of the latex particles is strengthened because of more coverage on the surface of the latex particles when the amount of APG is increased. Table 1. Influence of amount of APG on stability of the latex Amount of APG/g Mechanical stability Pass Pass Pass Pass Pass Calcium ion stability represents no coagulation after salt addition; represents little coagulation after salt addition; represents some coagulation after salt addition CONCLUSIONS The fluorinated acrylic latex was prepared successfully via semicontinuous seeded emulsion polymerization of BA, MMA and HFMA in water phase initiated KPS when nonylphenol ethoxylates are replaced with APG surfactant. The structure of the fluorinated acrylic latex is confirmed with a FTIR spectrum. DSC confirms that the latex is a kind of random copolymer and the consistency among the chain segment is fairly good. The particle size of the latex decreases with the increase in the amount of APG. The ionic stability of latex is also improved with an increase in the amount of APG. Acknowledgements This work has been supported by the Science & Technology Innovation Foundation of Ministry of Science & Technology for Small-Medium Enterprises, China (No. 12C ). In addition, the financial support of Zhejiang Provincial Natural Science Foundation of China (No. Y ) and Zhejiang University of Technology Natural Science Foundation (No ) are gratefully acknowledged. 68 Polymers from Renewable Resources, Vol. 5, No. 2, 2014

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