Styrene acrylic second-stage

Table VII - 35//65 - Two Stage Latexes Using Styrene/acrylate Second Stage Monomer...

Table X - Complete Set of Styrene-acrylic Second Stage Results...

The present paper demonstrates that for polystyrene seed latexes and styrene-acrylic or all acrylic second stage monomers, complete association can take place when S>100%, if certain mixtures of anionic and nonionic surfactant are used. The morphology of some of the two-stage latexes is described. 

ASA structural latexes have been synthesized in a two stage seeded emulsion polymerization. In the first stage, partially crosslinked poly(n-butyl acrylate) and poly( -butyl acrylate-sfaf-2-ethylhexyl acrylate) rubber cores are synthesized. In the second stage, a hard styrene acrylonitrile copolymer (SAN) shell is grafted onto the rubber seeds (16). 

At the end of the first stage (190 min), a constant average composition exists. During the second stage (involving only the addition of styrene) from 220-390 min, the butyl acrylate content decreases, although the overall distribution of the chemical composition remains constant. 

As expected, a single sharp transition is observed characteristic of a reasonably uniform copolymer. Figure 8 shows the dynamic mechanical spectrum for a two-stage process in which the first stage feed was ethyl acrylate and the second stage feed was styrene. This time, two well-defined transitions are observed characteristic of the hard and soft homopolymers. 

Besides two-component LIPNs, three-component LIPNs have also been studied through three-stage emulsion polymerization processes (Zhang et al. 1991, 1994 Isao et al. 1992). These authors synthesized poly(n-butyl acrylate) cross-linked with ethylene glycol dimethacrylate as the seed latex. Styrene and divinylbenzene were added at the second stage. The third stage was linear poly(methyl methacrylate). Starved polymerization conditions resulted in more regular-shaped latex particles than batch addition of monomer. 

The composition and quantity of styrene-maleic anhydride (SMA) copolymer resins were varied in emulsion copolymerisation of methyl methacrylate and n-butyl acrylate conducted by both batch and semicontinuous processes. The resulting particle sizes and levels of coagulum were measured to determine the optimum conditions for incorporation of the SMA resins into the resulting latexes. A semicontinuous process, in which no buffer was included and the SMA was added in a second stage comonomer emulsion, was found to produce coagulum-free latexes. 13 refs. 

A recent study (49) of 50 50 polybutyl acrylate core-poly-styrene shell polymerization has shown the importance of the grafting reaction which occurs in the second-stage polymerization. 

Table IX gives the recipe used for these pol3nnerizations. The polybutyl acrylate seed latex was prepared by heating the ingredients for 24 hours at 70° the styrene, water, and potassium persulfate were then added and polymerized for another 8 hours at 70°. Three methods of adding the styrene monomer were used in the second-stage polymerization (i) batch polymerization (ii) equilibrium swelling of the seed latex particles followed by batch pol3nneriza-tion (iii) starved semi-continuous pol3nnerization. The particle growth was essentially stoichiometric, i.e., no new particles were initiated. All three latexes formed transparent continuous films upon drying, whereas a 50 50 mixture of polybutyl acrylate and...

Core-shell nanoparticles can also be fabricated using microemulsions. This was performed using a two-stage microemulsion polymerization beginning with a polystyrene seed [62]. Butyl acrylate was then added in a second step to yield a core-shell PS/PBA morphology. The small microlatex led to better mechanical properties than those of similar products produced by emulsion polymerization. Hollow polystyrene particles have also been produced by microemulsion polymerization of MMA in the core with crosslinking of styrene on the shell. After the synthesis of core-shell particles with crosslinked PS shells, the PMMA core was dissolved with methylene chloride [63]. The direct cross-... 

The second important observation for the data in Figure 1 is that interdiffusion occurs even at the early stages of annealing time, in the all films. This result is very different from that reported by Joanicot et al. b for a different latex film. They found that polyacrylic acid [PAA] at the surface of a poly(styrene-co-butyl acrylate) latex effectively suppressed interdiffusion until the film temperature exceeded the Tg of the PAA, at which point the polar membranes ruptured. The essential difference in... 

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