Latex synthesis

Latexes can be synthesized by emulsion pol5mierization. Originally this meant emulsifying an aqueous-insoluble monomer in water with a surfactant and then using a water-soluble free radical initiator to cause polymerization. The term emulsion polymerization is still used, despite the fact that an emulsion is not alwa needed to produce polymer colloids. 

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The synthesis of latexes for adsorption titration was conducted in a thermostated glass reactor provided with a stirrer and an attachment for feeding in inert gas. The polymerization tempei ature is 328 K in the case of UA, and increases to 333 K, when EA. BA and St are used. Phase ratio was 1 4 (by weight). Ccuaposltions used for latex synthesis and latex characteristics are listed in Table I. 

In this study we describe a meftiod used to measure the reactions that silylated latexes can undergo in coatings formulations. Si NMR is shown to reveal crosslinking by silanol condensation occurring in silylated latex synthesis and cured films. In addition, a complementary method for quantitative determination of degree of alkoxysilane hydrolysis is described. Low-temperature separation of the latex solids from the volatile components followed by gas chromatographic analysis of the distillate can provide accurate and reproducible measurement of the alcohol generated by the hydrolysis of the alkoxysilanes used in the formulation. 

Fig. 1. Si NMR spectrum of solids from three mole percent MTIPS (Methaciyl Tri Aopropoxy Silane) latex synthesis.

Fig. 4. Si NMR spectrum of cured film from three mole percent VTIPS latex synthesis.

In summary, this pioneering work clearly demonstrated the possibility of aqueous catalytic insertion polymerization of acyclic and cyclic olefins, as well as aqueous ROMP. On the other hand, metal salts without any additional ligands to control the properties of the metal centers were utilized, and activation to the active species was probably also relatively ineffective in most cases. Consequently, catalyst efficiencies were moderate at best. Most of the polymerizations also afforded low molecular weight materials, or employed rather special monomers. The possibility of polymer latex synthesis appears not to have received much attention, although free-radical emulsion polymerization of styrene and butadiene was already a large-scale process at the time. 

The strategy of using a catalyst miniemulsion for latex synthesis offers two advantages (a) catalyst precursors do not have to be modified hydrophilically, often reducing synthetic effort [77] (b) somewhat water-sensitive precursors can be applied [82]. 

Figure 6a. The effect of anionic surfactants used in latex synthesis on the viscosity of 2% solution of HEUR 270. Key A, ammonium salt of nonylphenol ethoxylate average 20 oxyethylene units) sulfate O, ammonium salt of nonylphenol ethoxylate average 9 oxyethylene units) sulfate.

A series of latex copolymers were prepared using a typical emulsion polymerization recipe and procedure only the monomer composition was varied. The control composition (80/20 vinyl acetate/butyl acrylate) is similar to that used for interior latex paint. Table V lists the compositions and properties of the latexes. Percent solids, pH, and particle size are similar for all the latexes. Viscosity varies somewhat, but is within limits for this type of latex. The only unreacted monomer detected was the vinyl acetate. Thus, the incorporation of VEC into the emulsion polymerization via the monomer mixture did not affect the latex synthesis. The Tg and minimum film formation temperature (MFFT) of the latexes increase with increasing VEC content, which is expected based on the previous results. 

The relative reactivities of the monomers are important in establishing the strategy for latex synthesis [3]. The monomer water solubility is another important factor in the synthesis of latexes. This not only is a variable related to polyma-polarity, but also directly impacts on particle nucleation during polymer synthesis (see Chapter 5). 

Although there have been a number of studies of the mechanical properties of latex films, a detailed discussion of this topic is beyond the scope of this review. Thoe are several excellent reviews on the mechanical properties of coatings in gennal [65]. One of the main focus points in these reviews is the influence of CTosslinking in the polymer on its mechanical properties. In flie area of latex films, Larntda [66] has shown, for copolymer latex, how sensitive the mechanical propoties are to the details of latex synthesis (e.g. batch, sani-c itinuous or power-feed). Here the key feature is that different synthesis strat es give rise... 

Uses Carboxyiated comonomer for PVAc latex synthesis of resins, polymers, plasticizers, paints, drugs stabilizer in cosmetics flavoring agent in foods fragrance... 

The method of latex synthesis for thiol autoxidation catalysts was different from that used for the phenol autoxidation catalysts. Surface active quaternary ammonium ion monomers were used. Latexes were prepared by emulsion copolymerization of 96.2 mol % styrene, 1.0 mol % divinylbenzene (technical 55% active), 0.8 mol % ethylvinylbenzene, and 2.0 mol % of monomer 4, 3 5 or 6 with azo(bisisobutyronitrile) as initiator. The conductivity of an aqueous solution of 4 before polymerization was 440 x 10" ohm l cm l. Ultrafiltration of the copolymer latex gave an initial filtrate with condutivity of 20 x 10 ohm l cm l and a... 

S.K. Ooi, S. Biggs, Ultrasonic initiation of polystyrene latex synthesis. Ultrason. Sonochem. 7,125-133 (2000)... 

Keywords Ultrasound Acoustic cavitation Sonochemistry Functional materials Nanoparticles Polymer latex Synthesis of functional materials ... 

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