Crosslinked latex

Using magnesium ether carboxylates as emulsifier a porous polyvinylchloride can be made [218] and a propoxylated ether carboxylate is described as emulsifier to make an ethyl acrylate-styrene copolymer [219]. A crosslinked latex with a three-dimensional network is achieved by polymerizing an ethylenically unsaturated monomer with a reactive saturated monomer using ether carboxylate as emulsifier [220]. 

Bradford and Vanderhoff (20) have also prepared films from crosslinked latex particles. These authors studied a 65 35 styrene-butadiene copolymer crosslinked with varying amounts of divinylbenzene and found that although the incorporation of divinylbenzene retarded the coalescence of latex particles, these particles did indeed coalesce, presumably due to a similar interdiffusion of polymer chain ends. 

Pre-crosslinked Latex Blends. In these materials the individual latexes are crosslinked during synthesis, then blended, and a film is formed. Because of limited deformation and/or interdiffusion capabilities, such films tend to be weak, and only used for special purposes [Zosel and Lay, 1993 Lesko and Sperry, 1997], However, light crosslinking, as occurs in SBR latexes, may be tolerated. Pre-crosslinked latex blends materials are actually not IPNs, because the definition requires that at least one of the polymers be polymerized and/or crosslinked in the immediate presence of the other. An application of pre-crosslinked suspension-polymerized blends, in anionic and cationic form, is as ion-exchange resins. In suspensions, the particles are larger, usually of the order of 10-200 pm. 

As defined in Section 6.1 and above, the compositions described in Table 6.5 are all latex lENs, where two latexes are blended, then crosslinked. Latex IPNs are described in Section 6.4.7. 

Richard at Rh6ne-Poulenc [67] and Zosel at BASF [68] have carried out extensive studies on the dynamic mechanical properties of latex films. They examined latex made from monomers (like butyl acrylate and butadiene) that crosslink spontaneously during emulsion polymerization. Here crosslink density was reduced through the use of chain transfer agents. Alternatively, with monomers like BMA which form non-crosslinked latex, crosslinking was induced through the addition of bifimctiona] monomers such as methallyl methacrylate (MAMA). Richard has recently published a review of his work in this area [75]. 

The efect of crosslinking on the dynamic mechanical properties of polymers has been studied for many years. But one should note a clear distinction in the case of film formation from disposions of crosslinked latex particles. Each particle is a microgel. The crosslinks are confined to the particle itself without any additional ctosslinking across the particle boundaries [68]. Of course in some systems, like those formed from butadiene-containing latexes or from other latexes containing reactive functional groups, cross-boundary crosslinking can occur subsequent to film formation. 

Two of the most common difunctional monomers used to prepare homogeneously crosslinked latex particles are c inylbenzene (DVB) for non-acrylic systems and ethylene glycol dimethacrylate (EGDMA) for acrylic systems. DVB is available in solution at concentrations of 55.5% and 80.0% (Dow Chemical Co., DVB-55 and DVB-HP, respectively). DVB is a clear to yellow liquid with a boiling point of 195 °C (at 1 atm). The addition of DVB increases the solvent... 

Synthesis of (crosslinked) latex particles via emulsion polymerization... 

Figure 2.8. Stress-relaxation data for a PVAc/PMMA 50/50 polyblend. The PMMA portion was prepared from a lightly crosslinked latex to suppress flow at high temperatures. Numbers at right are temperatures in °C. (Takayanagi et ai, 1963.)...

Fabrics that are woven together from thread or yam are referred to as textiles, whereas shorter fibres bound together in a random, porous fashion are called nonwovens. In either case, crosslinkable latexes are extensively used as binders to improve stability, durability, and chemical resistance (205), and flame retardance (413). Acrylic copolymers are the most common class of binders, although other copolymers, such as styrene-butadiene or ethylene-vinyl acetate (242, 255) copolymers are often used when required by cost (247) or performance. The softness (flexibility) or hardness (strength) of the fabric is controlled through the glass transition temperature of the latex binder. 

The use of one-dimensional magnetic resonance imaging(MRI) to provide information on concentration and molecular mobility (as revealed by the spin-spin relaxation time) as a function of depth into crosslinking latex coatings during their film formation was studied. MRI profiles, with a pixel resolution of 9 micrometres, were obtained at regular time intervals from a vinyl... 

Journal of Coatings Technology 72, No.903, April 2000, p.45-61 POLYMER DIFFUSION AND MECHANICAL PROPERTIES OF FILMS PREPARED FROM CROSSLINKED LATEX PARTICLES Pinenq P Winnik M A Ernst B Juhue D Toronto.University Elf Atochem... 

An interesting exception, then, is the blending together of two separately polymerized and crosslinked latexes or suspensions. 

Vollmert presented 31 examples of multipolymer compositions, some of which were IPNs, (see Table 8.1). In example 20, a crosslinked poly(n-butyl acrylate) makes up network I. Poly(n-butyl acrylate-co-acrylonitrile) crosslinked with 1,4-butane-diol diacrylate makes up network II on a separate latex. A linear poly(styrene-co-acrylonitrile) latex makes up polymer III for a third latex. The three latexes are blended to form an impact-resistant polystyrene. This particular product, however, is not an IPN, because the two crosslinked latexes were polymerized and crosslinked separately and then mechanically blended together. 

Polymer Areas For the preparation of very fine particle size vinyl acetate, acrylic and styrene-acrylic latexes. Superior emulsifier for Zn-crosslinking latexes for floor finishes. Extremely low surfactant use levels that result in superior water-resistant and wet adhesion properties. 

Uses Dispersant, emulsifier, wetting agent, dispersant, foaming agent for acrylic and vinyl acetate emulsions, self-crosslinking latexes, textiles Regulatory Canada DSL listed... 

Ceral 165 Ceral CK Ceral LE Ceral MA Ceral ME Ceral MET Ceral MEX Ceral ML Ceral TN emulsifier, seafood Soda Phos (FG) emulsifier, seal coatings lndulin ISE emulsifier, sealants Dapro DF 7005 Dapro DF 7010 Isode-cyloxypropylamine acetate Niaproo Anionic Surftictant4 emulsifier, sec. oil recovery Duoquad T-50 Tallowdimonium propyl-trimonium dichloride Triton RW-20 Triton RW-50 Triton RW-150 emulsifier, selenium sulfide Dihydrogenated tallow phthalic acid amide HallSta TAB-2 Flake emulsifier, self-crosslinking latexes Aerosol 501... 

Calsuds A Ufaryl DL 80 CW Ufaryl DL 85 Ufaryl DL 90 C foam builder, scrub soaps Sodium nonoxynol-4 sulfate foam builder, self-crosslinking latexes Aerosol 501... 

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