(Laboratory of Fiber Materials and Modern Textiles,The Growing Base for State Key Laboratory,College of Chemical and Environmental Engineering, Qingdao University,Qingdao Shandong 266071,China)
【Abstract】The objective of this work was to analyze the effects of the polymerization temperature on the kinetic features (instantaneous and overall conversions) and colloidal characteristics [mean particle diameter, stabilities] in the semicontinuous seeded cationic emulsion polymerization of styrene and butyl acrylate. Azobis is obutyl amidine hydrochloride was used as an initiator.The surfactants wascetyl trimethyl ammonium chloride. The results showed that the final instant when the polymerization temperature of 85℃ emulsion highest conversion rate, and the temperature of the emulsion particle size, centrifugal stability is the best, 85℃ emulsion in the emulsion anti-dilution and acid salt stability also showed excellent stability.
【Key words】Semicontinuous seeded emulsion polymerization；Kinetic；Emulsion properties
It was known that there has a strong adsorption capacity between cationic latex particles with a positive charge and the substrate with the opposite charges. Cationic polymer has a wide range of applications in various industries in recent years, because it can neutralize the negative charge on the material surface[1-3].Semicontinuous seeded emulsion polymerization offers a great degree of operational flexibility, which permits both colloidal and polymeric characteristics to be controlled[4-5].
Many studies h论文范文e been carried out to analyze the effect of the polymerization methods, emulsifier, monomer ratio, initiator in an emulsion polymerization, but a particular temperature was setted. However, the effect of the reaction temperature in a cationic emulsion polymerization is reported in but a few cases.[3,6]
The aim of this work was to study the effect of the reaction temperature on the kinetic features (overall conversion) and colloidal stability (mean particle diameter, centrifugal stability, salt stability, dilution stability, freeze-thaw stability) of a semicontinuous seeded cationic emulsion polymerization of styrene(St) and butyl acrylate(BA). to study the effect of the reaction temperature on the growth of the particles starting from the same initial particle number. In addition, the stabilities of emulsion were studied deeply.
１．１ Preparation of latex particles
Figure 1 Reaction equation of emulsion polymerization
We employed five PS latex samples.They were synthesized by semicontinuous seeded emulsion polymerization in different temperature using the same procedure. They were all performed under nitrogen with mechanical stirring at 250rmp.Deionized water (80g)and part of emulsifier were added into 250mL reactor and left for degassing approximately 5min .then part of distilled St and BA mixed monomer were added for pre-emulsification process about 30min at room temperature. A part of initiator (V50)was then added. When the reactor was heated at reaction temperature, residual mixed monomer were added by dropwise. Residual emulsifier and initiator were added, after Completion of dropwise addition. After thermal insulation for 3h, the system was cooled to room temperature.Preparation of cationic latex particles were prepared at different temperature by means of a semicontinuous emulsion polymerization with the recipe given in Table1. Preparation of cationic latex particles of the reaction, such as figure 1.
Table 1 Recipes Used in the Semicontinuous seeded
１.2 Characterization of latex particles
The instantaneous conversion was dened as the ratio of the polymer formed to the monomer fed at that time. The conversions was determined gr论文范文imetrically. The particle diameter dn was measured by dynamic light scattering with an Auto Sizer Loc-FC-963 (Malvern Instruments, UK). The polydispersity of the particle diameters is calculated automatically. The density of latex particle was examined with density bottles. Centrifugal stability of polymer emulsion was determined by centrifuge with 2000 r/min for 20 minutes.Electrolyte resistance stability was evaluated by adding some electrolyte. Stability of frost thawing was determined by freezing at-10℃ for 20h.
２ Results and Discussion
２．１ Polymerization Features
Table 2 Properties of cationic emulsion
Table 2 shows the X T values and dn were obtained by examination. The results shows that the higher polymerization temperature, the 论文范文aller diameter. When it reaches a certain temperature, the particle size increases again. We can obtain the 论文范文allest diameter(PS4). The reason is that reaction temperature is increased, free radical generating rate increased, concentration of free radicals in the aqueous phase was increased. So, nucleation rate is increased. More and more latex particles can be generated.Therefore, the particle size decreased in according to the polymerization temperature increased.
We can also obtain that the effect of polymerization temperature on the final conversion of emulsion from table 2. With the temperature increases, the reaction rate is increased. So, conversion of emulsion is increased. That is because that, with the temperature increases, initiator decomposition was accelerated, Speed of chains growth rate constant is increased. Therefor, final conversion of emulsion was increased.
２．２ Emulsion stabilization
２．２．１ Centrifugal stability
Under the action of mechanical force, centrifugal stability is one of the important indicator for investigating emulsion is stable or not. It is showed that the centrifugal stability of all emulsion were very well except the PS5, which has a little precipitation.
２．２．２ Dilution stability
As we known, dilution stability of the emulsion will directly related to application performance. The result shows that the five samples h论文范文e a excellent dilution stability.
２．２．３ freeze-thaw stability
All the cationic emulsions h论文范文e formed cottony solid through reeze-thawed after 20h. It can be concluded that Freeze-thaw stability of cationic emulsion are poor.
２．２．４ Electrolyte resistance stability
Electrolyte resistance stabilities of cationic emulsion were determined by added H+, OH_ ,Mg2+,Respectively. The results are shown in Table 3.
Table 3 H+, OH_ Mg2+ resistance stabilities of cationic emulsion
Notes：×：Transparent, stability is good；－：Slight precipitation；*precipitation；＋：Emulsion turbid
Table 3 shows that the most stable emulsion is, which was prepared at 85℃, especially the Salt resistance stability. Acid, alkali, and salts resistance stabilities of others cationic emulsion(PS1, PS2, PS3) were not as good as PS4.
The features of the cationic seeded polymerizations were analyzed by the consideration of the polymerization temperature and the final conversion of latex particles obtained from the polymerizations. Through a comparison of the effects of polymerization temperature on the evolution of the colloidal characteristics of the latex particles obtained, some observations can be made. With the increasing of polymerization temperature, the conversion of the emulsion was increased, the particle size was also decreased.Furthermore, it is concluded that the dilution stability of all the cationic emulsion were excellent, expect the freeze-thaw stability are poor.
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