TWO-STAGE POLYMERISATION

In their reply, Doty and Lundberg (39) question the purity of Bamford s samples, which, they pointed out, were not recrystallised from methylene chloride at —30° C — a procedure considered by Blout as essential to ensure the purity of NCA. They correctly stressed that the "simple kinetic scheme cannot account for a broad molecular weight distribution produced by a two-stage polymerisation. This result seems to be indisputable, e. g. a sample produced by such a polymerisation had DPn = 20 and DPW = 170. 

A monomer preemulsion, used for miniemulsion polymerisation, was prepared by stirring a mixture of epoxy resin, acrylic monomers, surfactants, costabiliser and water. Miniemulsion polymerisation produced the composite latex. Methacrylic acid and/or dimethylaminoethyl methacrylate were added to introduce the functional groups into the composite latices. The functional groups were introduced either by batch polymerisation or two-stage polymerisation, the latex produced by the two-stage polymerisation method had good polymerisation stability, storage stability and solvent resistance. 11 refs. 

A foamable isotactic polypropylene homopolymer is obtained by metallocene catalysis and has a molecular weight distribution and density, which fall within broad ranges. It may be prepared in a multiple stage polymerisation process nsing the same metallocene component in at least two stages. 

The kinetics of y-benzyl-D.L-glutamate NCA polymerisation (17) resembles that of the L-isomer. Again, two stages are discerned in the... 

Nair and co-workers [203] reported polycyanate esters of an imide-modified novolac of different maleimide content. The resins underwent a two-stage independent thermal curing through trimerisation of the cyanate groups, as well as addition polymerisation of maleimide moieties. On heating, cyanate esters were transformed into an imido-phenolic-triazine network polymer. The cured resins exhibited a higher initial decomposition temperature compared with the cured maleimide novolacs. However, the thermal stability was found to be inferior to the conventional phenolic-triazine resin. 

New Orleans, La., August 1999, p.829-30 SYNTHESIS OF TWO-STAGE COMPOSITE LATEX PARTICLES BY DISPERSION POLYMERISATION IN CARBON DIOXIDE Young J L Spontak R J DeSimone J M North Carolina,Chapel HiU University North Carolina,State University (ACS,Div.of Polymer Chanistry)... 

Polybutyl acrylate/polyglycidyl methacrylate core-shell latex was prepared by a two stage emulsion polymerisation. The formation of core-sheU morphology was confirmed by contact angle measuremoits. The impact properties of blends of polybutyl acrylate/polyglycidyl methacrylate core-shell composite particles with epoxy resin is discussed. 15 refs. 

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... 

This comprehensive article describes the properties of acrylic dispersions including high-solids aaylic dispersions and reactive dispersions, and explains the advantages of using heterogeneous tailor-made morphology, built up directly within the polymer particle. This can be achieved by a two-stage emulsion polymerisation. 

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