Seeds emulsion polymerisation

The concept of surface imprinting by the use of seed emulsion polymerisation... 

Surface rearrangement of latex (latex obtained from seeded emulsion polymerisation)... 

Acrylonitrile is also commonly found in impact modifiers, such as the acrylonitrile-butadiene-styrene (ABS) type, produced by emulsion polymerisation. Polybutadiene seed latex particles are grafted onto styrene and acrylonitrile in a seeded emulsion polymerisation process. As the styrene-acrylonitrile copolymer shell forms, polybutadiene domains are spontaneously separated within. The resulting impact modifier particles are subsequently compounded with polystyrene to product high impact polystyrene (HIPS). The impact modification properties of the latex particles may be optimised through varying the butadiene content, the particle size and structure, and the shell molecular weight. A basic formulation for an ABS impact modifier is given in Table 6. 

Journal of Applied Polymer Science 76, No.7, 16th May 2000, p.186-96 SEEDED EMULSION POLYMERISATION OF STYRENE INFLUENCE OF ACRYLIC ACID ON THE PARTICLE GROWTH PROCESS Slawinski M Schellekens M A J Meuldijk J van Herk A M German A L Eindhoven,University of Technology... 

SEMIBATCH SEEDED EMULSION POLYMERISATION OF ACRYLIC MONOMERS BIMODAL PARTICLE SIZE DISTRIBUTION... 

No.3,1997, p.249-54 LATEX STABILITY IN SEMIBATCH SURFACTANT-FREE SEEDED EMULSION POLYMERISATION OF BUTYL ACRYLATE Chem C-S Lin C-H Chen T-J Taiwan,National Institute of Technology... 

Journal of Applied Polymer Science 63, No.12, 21st March 1997, p.1543-55 MORPHOLOGY OF POLYISOPRENE-CO-STYRENE-CO-METHACRYLIC ACID LATEX PREPARED BY TWO-STAGE SEEDED EMULSION POLYMERISATION Karlsson O Hassander H Wesslen B Lund Institute of Technology... 

Heterogeneous latices were prepared by a two-stage seeded emulsion polymerisation process at 80C using potassium persulphate as initiator and sodium dodecyl sulphate as emulsifier. Styrene-methacrylic acid (MAA) copolymer latices containing varying amounts of MAA were used as seeds. The second stage polymerisation was performed either as a seeded batch process or as a seeded... 

The packing efficiency of a monodisperse latex may be increased by the addition of one or more latices of smaller particle size. Hence certain blends of PVC latices can be used to produce plastisols with low viscosity over a wide range of shear rates (5). However it is more usual to produce multi-disperse particle size distributions at the polymerisation stage in a seeded emulsion polymerisation process. 

An emulsion polymerisation system comprises water, an initiator (usually water soluble), a water-insoluble monomer and a colloidal stabiliser, which may be added or maybe formed in situ. The main locus of polymerisation is within the monomer-swollen latex particles, which are either formed at the start of polymerisation or may be added initially (in which case one has a seeded emulsion polymerisation). The term emulsion polymerisation is a misnomer (arising for historical reasons the process was originally developed with the aim of polymerising emulsion droplets, although, in fact, this does not occur). The starting emulsion is not thermodynamically stable. An inverse emulsion polymerisation is one where the continuous phase is organic in combination with an aqueous discrete phase containing a water-soluble monomer (e.g. acrylamide). Two variants of emulsion polymerisation are... 

An ab initio emulsion polymerisation involves the emulsification of one or more monomers in a continuous aqueous phase and stabilisation of the droplets by a surfactant. In a seeded emulsion polymerisation, one starts instead with a preformed seed latex. Usually, a water-soluble initiator is used to start the free-radical polymerisation. The locus of polymerisation is within the submicron polymer particles (either formed during the process or added at the start), which are swollen with monomer during the polymerisation process, and dispersed in the aqueous phase. The final product is a latex comprising a colloidal dispersion of polymer particles in water. Ab initio emulsion polymerisation differs from suspension, mini- and microemulsion polymerisations in that the particles form as a separate phase during the polymerisation process. The particle size is much smaller than those formed in a suspension polymerisation. 

Composite latex particles are usually prepared by seeded emulsion polymerisation. In the first stage well-defined particles are prepared, while in the second stage other monomer... 

The characterisation of the particle morphologies is very important in order to control seeded emulsion polymerisations and is described in Chapter 8. 

Batch to batch variations due to irreproducible particle nucleation may jeopardise product consistency. In order to avoid this problem, seeded emulsion polymerisation may be employed. 

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