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Procedia Engineering
Procedia Procedia Engineering 00 (2011) Engineering 18000–000 (2011) 353 – 357 www.elsevier.com/locate/procedia
The Second SREE Conference on Chemical Engineering
Effect of Temperature on Emulsion Polymerization of n-Butyl Acrylate Guangfeng WU a, Chunyan WANG, Zhiyong TAN, Huixuan ZHANG Synthetic Reins and Special Fiber Engineering Research Center, Ministry of education, Changchun University of Technology, Changchun, 130012, China a
[email protected]
Abstract Poly (n-butyl acrylate) was synthesized by emulsion polymerization using CHP-Ferrous sulfate redox system as initiator. The effect of reaction temperature on the polymerization rate and particle size (D) was studied. The reaction showed a relatively high rate and reached high conversion in short time. The particle size was dependent on the reaction temperature. The size of particle reduced from 95nm to 65nm when the reaction temperature changed from 20oC to 70oC with fixed polymerization conditions. The activation energy is 29.80kJ/mol.
© 2010 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of Society for Resources, Environment and Engineering Keywords: Emulsion polymerization, n-butyl acrylate, redox initiator, kinetics.
1. Introduction Acrylates are usually used as the polymerization monomer. And n-butyl acrylate is one of the most widely used acrylates. Emulsion polymerization is the widely used synthesis method. Acrylic latexes are intensively used as varnishes, paint or adhesives. The rubber was applied in all kinds of high temperature, or oilness environment. It is necessary to control the molecular weight distribution, the gel fraction and other characters because the structure performances affected the application. The molecular weight distribution can be controlled by injecting chain-transfer agent [1～3] and the changing of temperature and the initiator concentration [4～5] during the emulsion polymerization of nbutyl acrylate. At present, potassium persulphate is widely used to be the initiator for emulsion polymerization of n-butyl acrylate in high temperature. However, the knowledge of the kinetics, molecular weight distribution, gel fraction, and branching [6～8] is scarce.
1877-7058 © 2011 Published by Elsevier Ltd. doi:10.1016/j.proeng.2011.11.056
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In this work, the effect of the temperature on the rate of polymerization, particle size during the emulsion polymerization of n-butyl acrylate with the redox system as initiator was investigated. 2. Experimental Section 2.1. Materials n-Butyl acrylate (BA) for analysis was purified by distilling in vacuum before use. Sodium lauryl sulfate (SDS), ferrous sulfate (FeSO4·7H2O), sodium formaldehyde sulfoxylate (SFS), ethylene diamine tetraacetic acid(EDTA), Diisopropylbenzene hydroperoxide(CHP) and hydroquinone used were analytical grade. These were used without any further purification. Deionized water was used to prepare all solutions. 2.2.Polymerizations The polymerization was carried out in a glass reactor fitted with a reflux condenser, a sampling device and a nitrogen inlet. The experimental procedure was as follows: the aqueous solution of EDTA and FeSO4·7H2O were initially charged into the reactor together with the solution of SDS and SFS. The reactor was heated to the set temperature. Keeping the nitrogen inlet for about 30 min to deaerated the oxygen from the system. The monomer and oxidizing agent were injected at the same time. The poly (BA) latex was coagulated by aluminum muriate aqueous, and dried at 60oC in an oven. The recipe was shown in Table 1. Table 1. Recipe of polymerization
Initial part
Incremental feeding part
Ingredient
Dosage/(g)
DDI
300
SDS
1.4
EDTA
0.1
FeSO4
0.01
CHP
0.2
SFS
0.5
BA
100
2.3.Characterization Samples were withdrawn from the reactor at appropriate intervals aliquots, and inject a small amount of hydroquinone, to prevent further polymerization. The conversion was measured gravimetrically and using the following formula:
x(%)
( M 2 M 3 ) /( M 1 - M 3 ) 100% Wm
(1)
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Where the M1, M2, M3 are the amount of the sample, the weight of dried sample and the buffer in the sample; Wm is the monomer fraction for the monomer percentage in the reactor. The rate of polymerization was calculated from the slope of the conversion-time curve.
R p M 0
dx dt
(2)
Plus-90 Laser Particle Size Analyzer was used for particle size measurement. 3.Results and Discussion Fixed the polymerization condition, the effect of the temperature on the polymerization rate and the particle size were studied. 3.1.Effect of temperature on the polymerization rate Four experiments were carried out at different temperature and Fig. 1 presents the polymerization conversion versus time at different temperature. The range is from 20oC to 70oC. All the runs showed high polymerization rates. The conversion reached the high value of about 95% within 20 min. Then the conversion increase leveled down. The higher the temperature is, the sooner the conversion reached the high value. The redox system used is a diffusion controlled system but not temperature controlled system. So the runs at different temperature show no different polymerization rate. But the increase of temperature reduced the induction period. The run at higher temperature reached the high value for sooner. 100
Conversion(%)
80 60 20℃ 30℃ 50℃ 70℃
40 20 0
0
20
40
60 t (min)
Fig. 1, Effect of temperature on polymerization conversion
80
100
120
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2.0
lnRp (mol/L min)
1.5 1.0 0.5 0.0 2.8
2.9
3.0
3.1 -1
3.2
3.3
3.4
3.5
-1
T × 10-3(K )
Fig. 2, Relationship between reaction rate and temperature
The rate of polymerization was calculated by the formula (2). [M0] is the initial monomer concentration and dx/dt is the slope of the conversion-time curve. Construct the relationship between ㏑ Rp and T-1 (Fig. 2), in accordance with the Arrhenius relation expression, the activation energy is 29.80kJ/mol. 3.2.Effect of temperature on the particle size Fig. 3 shows the particle size of poly n-butyl acrylate at different temperature. The higher the temperature is, the smaller the particle size is. The size of the latex particle decreased from 95nm to 65nm, when the temperature increased from 20oC to 70oC. The speed of the free radical creating increased because of the higher temperature, lead to the augment of the free radical concentration in the aqueous phase. The increase of the rate that free radical spread to the emulsion particle from the aqueous phase induced the enhanced nucleation rate. The number of the particles increased and the particle size decreased.
Guangfeng WU et/ al. / Procedia Engineering 18 (2011) 353 – 357 Author name Procedia Engineering 00 (2011) 000–000
100
Particle size (nm)
80 60 40 20 0
20
30
50
70
T (oC) Fig. 3, Particle size of poly n-butyl acrylate latex at different temperature
4.Conclusions Emulsion polymerization of n-butyl acrylate initiated by CHP-Ferrous sulfate redox system was investigated. With the fixed polymerization condition, the particle size decreased with the increase of temperature. When the temperature increased from 20oC to 70oC, the particle size decreased from 95nm to 65nm, and the activation energy is 29.80kJ/mol. References [1] Plessis C, Arzamendi G, Jose R J. Seeded semi batch emulsion polymerization of butyl Acrylate: effect of the chain-transfer agent on the kinetics and structural properties [J]. Polym Sci Part A:Polym Chem, 2001, 39:1106-1119. [2] Plessis C, Arzamendi G, Leiza J R, et al. A decrease in effective acrylate propagation rate constants caused by intramolecular chain transfer [J]. Macromolecules, 2000, 33: 4-7. [3] Salazar A, Gugliotta L M, Vega J R, et al. Molecular weight control in a starved emulsion polymerization of styrene [J]. Ind Eng Chem Res, 1998, 37: 3582-3591. [4] Jang S H, Lin P H. Discontinuous minimum end-time temperature/initiator policies for batch emulsion polymerization of vinyl acetate [J]. Chem Eng Sci, 1991, 46: 3153-3163. [5] Tsen A Y D, Jang S S, Wong D H W, Babu J. Predictive control of quality in batch polymerization using hybrid ANN models [J]. AIChE J, 1996, 42: 455-466. [6] Plessis C, Arzamendi G, Leiza J R, et al. Seeded semibatch emulsion polymerization of n-Butyl acrylate: Kinetics and structural properties [J]. Macromolecules, 2000, 33: 5041-5047. [7] Sajjadi S, Brooks B W. Semibatch emulsion polymerisation reactors: polybutyl acrylate case study [J]. Chem Eng Sci, 2000,55: 4757-4781. [8] Julien Chauvet, Jose M Asua, Jose R Leiza. Independent control of sol molar mass and gel content in acrylate polymer/latexes [J]. Polymer, 2005, 46: 9555-9561. [9] Shivakumar K, Veeraiah M K, Rai K S, et al. Kinetics of polymerization of acrylonitrile initiated by the vanadium (V)-bisulphite redox system in sulphuric and perchloric acid media [J]. Journal of Molecular Catalysis A: Chemical, 2007, 273: 218-223.
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