Encapsulation of inorganic filler particles by emulsion polymerization

Emulsion polymn. of styrene in the presence of CaCO3 modified with titanate AT52 was carried out; particles were covered with a polymer layer consisting of small particles. The amt. of encapsulating polymer in the isolated product was detd. 80% Of the polymer in the product was extd. with toluene and its mol. wt. was det

The Importance of Chain-Length Dependent Kinetics in Free-Radical Polymerization: A Preliminary Guide

The effect of chain-length dependent propagation at short chain lengths on the observed kinetics in low-conversion free-radical polymerization (frp) is investigated. It is shown that although the values of individual propagation rate coefficients quickly converge to the high chain length value (at chain lengths, i, of about 10), its effect on the average propagation rate coefficients, kp, in conventional frp may be noticeable in systems with an average degree of polymerization (DPn) of up to 100. Furthermore it is shown that, unless the system is significantly retarded, the chain-length dependence of the average termination rate coefficient, kt, is not affected by the presence of chain-length dependent propagation and that there exists a simple (fairly general) scaling law between kt and DPn. This latter scaling law is a good reflection of the dependence of the termination rate coefficient between two i-meric radicals, kt i,i, on i. Although simple expressions seem to exist to describe the dependence of kp on DPn, the limited data available to date does not allow the generalization of these expressions

On-line extraction of polymers, oligomers, additives and monomers by multiple solvents on packed HPLC columns

Extn. of monomers, additives, oligomers, and polymers from a blend is very time-consuming and labor intensive. Using a special guard column and multi-solvent gradient liq. chromatog. (HPLC), the extn. and anal. can be performed in one ste

The effect of composition drift and copolymer microstructure on mechanical bulk properties of styrene-methyl acrylate emulsion copolymers

In order to determine the influence of composition drift and copolymer microstructure on the mechanical bulk properties of styrene methyl acrylate copolymers, several copolymers were produced by emulsion copolymerizalion. Three different average compositions were used. By perforrming the copolymerizations under batch and semicontinuous conditions with two different monomor addition strategies (starved conditions and optimal addition) it was possible to control composition drift and to produce copolymers with different microstructures (chemical composition distributions). All these copolymers were processed in a way that ensured that the original particle structure was lost before the polymers were tested. It was found that composition drift had an influence on the mechanical properties (Young's modulus, maximum stress, elongation at break). This influence could be understood very well on the basis of present knowledge about structure-mechanical properties relationships. In the case of homogeneous copolymers maximum stress and elongation at break arc dependent on the molecular weight, and only weakly dependent on the chemical composition, and Young's modulus is independent of chemical composition and molecular weight in the range of compositions investigated, as expected. ln the case of heterogeneous copolymers, the influence of copolymer microstructure on Young's modulus, maximum stress and elongation at break is very large. Depending on the extent of control of composition drift during the polymerizations, phase separation was observed in the processed polymers, and the presence of a rubber phase affected the properties profoundly

Pulsed-laser studies on the free-radical polymerization kinetics of styrene in microemulsion

A mean value of 339 L mol-1 s-1 was obtained for the propagation const. derived from pulsed-laser polymn. (PLP) of styrene in aq. AOT microemulsions. For accurate detns., simulations accounting for the esp. high radical concn. after the laser pulse in microemulsions were recommended. PLP with microemulsions apparently permitted specific kinetic aspects such as transfer to monomer and influence of droplet size on bimol. termination to be studied in detai