| The preparation of hybrid polymer latexes is an area of greatindustrial interest in recent years. These latexes, with heterogeneous particle structures as well as precisely tailored physical and chemical properties, creates a more versatile class of materials. A wide range of available monomers and polymerization processes allows the formulator to design a large number of structures to meet a variety of molecular and colloidal requirements. Acrylic (AC) emulsions and aqueous polvurethane (PU) dispersion are two kinds of major materials used in paint, ink, adhesives and coatings industries. Both systems have some disadvantages such as reduced film formation, lower chemical resistance, coarse mechanical properties of acrylic, a high cost, low pH stability, and limited outdoor durability of PU. To improve the properties of an individual polymer system it is common to mix them. Better mechanical stability, solvent and chemical resistance, and toughness could be obtained from the PU portion. Outdoor resistance, pigmentability, and lower cost are the benefit from the AC component. How direct blending of AC emulsion and PU dispersion usually gives the resulted emulsion inferior properties than those predicted by the "rule of mixtures," because of limited compatibility between PU and polyacrylate.When a polymer is soluble in the monomer, which is to be polymerized in miniemulsion, the resulting latex does contain in the polymer particles a mixture of polymers. This kind of latex is called hybrid latex. Its preparation is specially useful when the said polymer cannot be polymerized directly in emulsion; even ifthe said polymer can be emulsified in solution, the miniemulsion procedure can be an important progress, because, after polymerization of the miniemulsion, provided that the monomer conversion has been completed, there is no more volatile organic compound to be able to pollute the atmosphere. It may result hi a big progress for the environment.In this paper, polyurethanes were prepared by condensation polymerization of Isophorone diisocyanate (IPDI) and polypropylene glycol (PPG), with as a chain extender butanediol (BDO). The foundation was so designed that the PU obtained different end groups that is NCO end groups, methoxy end groups, or methacrylic end groups. Then, using the acrylic monomers and PU carried out miniemulsion polymerizations. The kinetic of this kind of miniemulsion polymerization and properties of hybrid polymer were studied. The results show that, polyurethane is hydrophobe enough to stabilize miniemulsion of styrene or MMA or mixtures of acrylic monomers, against Ostwald ripening. The droplet sizes are in the range 80-300 nm in the presence of moderate amounts of SDS. The droplet size depends chiefly on the initial viscosity of the solution of PU hi the monomer(s).These monomer droplets can be polymerized by using either water-soluble initiator, such as KPS, or oil-soluble initiator such as AIBN or BPO, leading to polymer particle sizes very close to those of the initial droplets of the miniemulsion. There is occasionally some homogeneous nucleation, when both the monomer and the initiator display significant water solubility. In the most cases the polymerization is rapid and complete, provided that the polymerization temperature is high enough, with adequate initiator concentrationIn the case of BA/MMA copolymers, the use of a batch process causes a composition drift due to the difference of reactivity of the two monomers. Themore reactive MMA is polymerized preferentially. In addition acceleration, is observed sooner when the composition of the monomer mixture is richer in BA. A few of these copolymers were characterized by GPC and DSC. The data of DSC confirm the composition drift.It was found that the polymerization rate of PU-acrylate hybrid miniemulsion stabilized with methacryl endgroups PU e was low at the early stag and then increased rapidly. The polymerization rate decreased with increasing PU content and an increase in the soft segment length reduce...
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