Semi‐suspension polymerization process

Abstract

A novel heterogeneous polymerization process for synthesizing particulate with a wide range of properties has been developed. This process, which is called semi ‐ suspension polymerization (SSP), consists of two steps. In the first step a mixture of monomer, polymer, initiator, and other required ingredients is prepared by means of a non‐ suspension polymerization process. In the second step, this mixture is suspended in the continuous phase and is polymerized to complete conversion. The properties of the semi‐polymerized mixture prepared in the first step as well as the rate of polymerization in the second step can be used to control inter‐droplet and/or intra‐particle mass transfer. This unique capability allows control of the mass transfer between and within particles during the suspension polymerization, thereby enabling synthesis of particulate with a wide range of molecular properties and morphologies unattainable by conventional suspension polymerization. The characteristics of this process and its advantages/limitations will be discussed.

SP–PLP–EPR Investigations into the Chain‐Length‐Dependent Termination of Methyl Methacrylate Bulk Polymerization

“…, exceeds previous k n-BMA k 1;1 t values, by about a factor of 3, is understood in terms of the differences in bulk viscosity h n-BMA /h MMA % 1.7 and hydrodynamic radius [24] r s,n-BMA /r s,MMA % 1.6, which, according to Equation (3), results in the diffusion coefficient of MMA being above the one of n-BMA by approximately a factor of 3.…”

A kinetic study of butyl acrylate free radical polymerization in benzene solution

“…Dilution of monomers produces a decrease of the average degree of polymerization and, consequently, an increase of the overall termination rate coefficient. [46,47] When the monomer concentration decreases, the frequency of propagation, k p [M], decreases considerably. Assuming that there is a dead formation by termination, this must mean that the growth probability of the radical is reduced which, indeed, must lead to the living radical distribution becoming weighted toward lower chain lengths.…”

“…Changes of monomer concentration may affect the termination rate constant through the changes in the thermodynamic properties of the polymer-solvent system or changes in the medium viscosity or, generally, in the frictional properties of the polymer chains. [46] Considering that it is well documented [46] that k t is proportional to the medium fluidity, k k = k t 0 /g, the results obtained and collected in Tab. 1 show that monomer dilution decreases the viscosity of the medium and it increases the overall termination rate coefficient.…”

Supermicron polymer particles with core‐shell type morphologies

“…This procedure of partially polymerizing the monomer prior to particle formation enhances latex stability and enables preparation of smaller particles. 6 The aqueous phase was a 0.75 wt % solution of methylhydroxycellulose in water.…”