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The distribution of unsaturations in the prepolymer of a typical unsaturated polyester (UP) resin (maleic anhydride, phthalic anhydride and 1,2‐propylene glycol) has been shown to influence the kinetics of the cure process with styrene monomer. Segments containing double bonds in close proximity appear to lower the reactivity of the resin due to steric hindrance, as indicated by the fact that the rate of cure and the final degree of cure, measured by differential scanning calorimetry (DSC), increase as the average sequence length (SL) of maleic units decreases. This implies that the reactivity of UP resins may be improved by synthesis of prepolymers with certain reactant sequence‐length distributions. The copolymer formed by the melt condensation process of maleic anhydride, phthalic anhydride and 1,2‐propylene glycol in the absence of a transesterification catalyst has a non‐random structure with a tendency towards blockiness. This was established using 1H NMR analysis in tandem with deterministic and Monte Carlo modelling techniques. Copyright © 2003 Society of Chemical Industry

In Part I of this work (Gosden et al., 1996) a novel algorithm has been described for the fast calculation of complex molecular weight distributions (MWD) produced in living anionic polymerisation conducted in periodically perturbed continuous stirred tank reactor (CSTR). Here it is shown by rigorous derivation that the new formula of Gosden et a! gives the correct solution of the sets of differential equations which describe living polymerisation reactions in CSTR reactors where mixing can be regarded as perfect. A numerical validation of the algorithm is also reported where computed solutions have been compared with the results obtained by traditional numerical integration methods and perfect agreement has been found. Experiments are also reported which have been carried out with a computer controlled laboratory-scale polymerisation reactor in an attempt to validate the simulation predictions.Results are presented which show that, for a simple square-pulse input perturbation in monomer and initiator feed concentrations, there is good agreement between theory and practice. In order to make realistic comparisons between theory and the gel permeation chromatography data obtained with samples taken from the reactor, the simulated data has been deliberately broadened with a Gaussian function in an attempt to mimic reactor and any other broadening effects which might stem from the method of analysis. Some wider issues relating to polymerisation reactor control using pulsed feeds and the wider application of the algorithm are briefly reviewed. 45

The quantification of the relationship between physical properties of polymeric products and the sequence distribution of comonomer units in a polymer chain is not an easy task. In this work, detailed consideration is given to the sequence lengths and sequence length distributions to be expected in unsaturated polyesters formed by the reaction of maleic anhydride, phthalic anhydride and a diol, a reaction which gives rise to the low molecular weight precursors used in unsaturated polyester resins. Monte Carlo methods are used to explore the effects of rate constants, reactant stoichiometry and extent of reaction on the microstructure of the chain. Attention is also given to structural asymmetry of the diol component and the influence of the dynamics of the ring opening of the anhydride coreactants on the products. The approach is generic and can be readily adapted for any copolymerization which proceeds by a stepwise kinetic mechanism.© 2003 Society of Chemical Industry

In a study of the technology of the melt spinning of 6.6 nylon filaments of diameter in the range 30–100 μ, some new crystallisation phenomena have been noted. Because of the geometrical form of the filaments, cooling from the melt is extremely rapid. Solidification takes place in a fraction of a second, and further cooling to room temperature is also rapid. The polymer can be observed at various stages during its quenching, either by taking samples from the running filaments, or by examining it whilst it is running. Under these conditions, the solid polymer is seen to have a structure not very different from that of the melt. This structure is stable at room temperature for long periods in the absence of moisture. However, on exposure to moisture, diffusion of water into the filament may result in elongation with accompanying changes in the crystalline character. The effects of temperature and moisture concentration on the diffusion process have been studied. X‐Ray diffraction, depolarisation of light and microscopical techniques have been used to examine the crystallisation process in the filament as it is being spun and during the subsequent process of equilibration with water. X‐Ray and optical results show changes of structure to occur on different time scales: the implications of this on the concepts of polymer morphology are discussed. The important röle played by atmospheric moisture in the crystallisation of 6.6 nylon is established, and the likely dependence on water content of second‐order transition data is examined.

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