SynopsisThis study explored the effects of chemical composition, extent of polyesterification and possible side-reactions upon the rheological behavior of a variety of oil-modified, glyceryl phthalate alkyds in both melt and in dilute solutions with several solvents. Correlative data were obtained on molecular weight and on other aspects of solubility and drying properties important to paint technology. Viscometric data proved very useful in relating variances of reaction degree with usage properties of these polymeric materirtls. Those data suggest a viewpoint of the gel point, mechanism which enhances practical utility of polyesterification theory. This hypothesis proposes that alkyd synthe& is not a homogeneous reaction throughout, and that phase separation creates a colloidal dispersion in the reacting mass long before gelatification occurs. Classical polyeaterification theory can predict the event of initial phase separation; other process variables affect the relative stability of the transition colloid which ultimately coalesces into the final gel structure. Practical properties of alkyds in paint vehicles can be adjusted to satisfy varying requirements by arresting the reaction at different levels before or in the transition region. Measurements of melt viscosity and intrinsic viscosity are especially sensitive and convenient probes for control of process and product in terms of this concept.

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It is possible to generate, in specially formulated styrene emulsion polymerizations, latices in which the monomer—polymer particles are uniform through all stages of growth. These latices are kinetically similar to their polydispersed counterparts and can therefore be used as model systems in generalized kinetic studies of emulsion polymerization. The most important feature of these systems is the fact that the particles are uniform throughout the reaction with regard to all intrinsic properties and rate processes, and the particles can be characterized by this complete, continuous uniformity. Certain remarkably simple, but precise, relationships exist between the overall, measurable kinetic parameters and the individual particle kinetic parameters, thereby resulting in a heretofore unrealized analytic accessibility. Molecular weight kinetic analyses are an order of magnitude more accurate than in non‐uniform systems. Application of these continuously uniform systems in actual kinetic studies indicates an inconsistency in the current concepts of emulsion polymerization, i.e., the generation of polymer at a constant molecular weight is predicted while an increase of several fold is observed. Before the situation can be clarified, further studies with continuously uniform systems are needed to evaluate molecular weight development, molecular weight distribution, and molecular structure and also to re‐evaluate the rate and diffusion processes which control these structural features.

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SynopsisSyntheses are described where dimer fatty acid (C36), or anhydrides of trimellitic, or pyromellitic, or dodecenylsuccinic acids are substituted in part for components of a model polymer derived from 1 mole each phthalic anhydride and glycerol, and 0.4 mole of linoleic acid. These polymers are compared at several degrees of polyesterification with respect to endgroup analysis, melt and intrinsic viscosity, and fractionation and emulsification behavior in water-solvent mixtures. The data suggest that predictions of the gel point in terms of functionality concepts are of general value only for defining the reaction degrees where insoluble molecules can first appear. The experimental event of gelatification can be delayed to varying degrees by different types and concentrations of inert solvent. The extent of reaction where molecular complexity can give a gellable polymer in the absence of solvency retardation occurs near the theoretical gel point and can be located by inspection of functions relating either melt or intrinsic viscosity to molecular weight. Significant differences in polymer structure have a very small effect on this parametei, nor is there much evidence to show preferential reactivity of eimilar functional groups associated with different structures. Other data here cited demonstrate some practically useful facts regarding how composition and molecular weight affect solvency behavior; however, no general correlations were found which relate solubility behavior to quantities here measured.In common usage in the paint industry, the term "alkyds" identifies a large class of polymers derived by es'terification of mixtures of mono and dibasic acids with simple or mixed polyols having an average b.ydroxy1 functionality greater tb.an two. The m.onobasic acid may be abietic, benzoic, or a variety of synthetic acids. Most commonly it is an l&carbon, vegetable oil, fatty acid, either saturated or unsaturated.For these polyesters, the theory of polyesterification as developed by Carothers,' Kienle,2 and Flory3s4 has not been used extensively to give guidance to polymer design or process control. To apply th.ese theories for purposes like predicting gel point and molecular weight, the chemical reactions producing the polymer must be clearly defined and side reactions should play an insignificant role. For many years, apparent failures in applying the theory were attributed to complications produced by uncontrollable side reactions, such as varying degrees of olefinic polymerization.