spopsiaThe most important assumptions underlying the Smith-Ewart theory are that the locus of chain propagation is the monomer-swollen latex particle, polymeric chains are initiated by radicals entering from the water phase into the particles, chain termination is an instantaneous reaction between two radicals within one particle, and particles are nucleated by radicals absorbed intQ, monomer-swollen soap micelles. Right or wrong, these and other assumptions used by Smith and Ewart are retained in this paper. The newly derived and experimentally verifiable equations contain only such parameters which can be determined by experiments not involving emulsion polymerization. The proportionality constant between the particle number and the appropriate powers of soap and initiator concentrations is defined in terms of these independent parameters. Absolute rate equations are presented for the intervals before and after the completion of particle nucleation. To calculate these rates it is not necessary to have prior knowledge of the experimental particle number. The conversion at which particle nucleation is complete is calculated. The molecular weight is defined in terms of independent parameters.It is shown that the validity of the theory is confined to specifiable intervals of conversion, to a certain range of monomer/water ratio, and to soap concentrations whose upper and lower limits are given.Predictions are made for the particle size distribution.

SynopsisNonpolymerizing latex particles surrounded by an aqueous phase saturated with monomer absorb only a finite amount of monomer, even if the monomer is a good solvent for the polymer, because the surface energy of each particle increases on swelling. At equilibrium the change in surface energy and the free energy of mixing exactly balance. Equations based on this thermodynamic principle predict with good accuracy the saturation swelling of crosslinked and uncrosslinked latex particles and the partitioning of monomer between the aqueous phase and latex particles at partial saturation. The available experimental data on swelling of latex polymers with monomers are reviewed. Earlier papers assumed that during emulsion polymerization the monomer concentration in the latex particles is independent of conversion as long as monomer droplets are present.The thermodynamics of the swelling of latex particles with a blend of two monomers is presented. The calculations indicate that copolymerization in emulsion should define reactivity ratios differing from those of homogeneous copolymerization by not more than 40% if the solubility of the comonomers in water is low. The reactivity ratio scheme is strictly applicable to emulsion copolymerization if the solvent properties of the two comonomers are identical.This assumption is shown to be a justifiable approximation.In the first four papers of this series (Parts I-IVl-3, it was assumed that the sole locus of chain propagation during emulsion polymerization is in the latex particles swollen by monomer. The purpose of the present paper is to review the theoretical considerations and experimental facts related to the swelling of the latex particles by monomers. THERMODYNAMIC THEORYThe monomer is assumed to have limited solubility in water. Such a monomer (or other suitable solvent) is added to a dead, nonpolymerizing latex so that the aqueous phase should become saturated with monomer. Even if the monomer is a good solvent for the polymer and is miscible with the polymer at any ratio in bulk, only a limited amount of monomer is absorbed by the latex particles because the surface energy increase on swelling partially compensates for the free energy of mixing. It is assumed that water does not dissolve in the latex particles or in the pure monomer. 2859

synopsisTables are presented for convenient calculation of the basic parameters of the revised Smith-Ewart theory. For the methyl methacrylate (MMA)/sodium lauryl sulfate (SLS)/K2S208, and for the styrene/SLS/K&O8 reaction mixtures parameters are presented from which the absolute values of the following quantities can be conveniently calculated for any temperature, soap, and initiator concentration: particle number, particle radius, conversion where particle nucleation stops, rate and molecular weight in interval XI, the interval after completion of particle nucleation and before the disappearance of monomer droplets. The theoretical predictions are compared to new experimental data and to those from the literature. The available data con6rnt the theoretical prediction that particle nucleation stops after a very small amount of polymer is formed, of the order of 0.01 cc. polymer/cc. water in most recipes. The theory and experiments are in good qualitative agreement for the conversion rate prior to completion of particle formation: the conversion rate rises with time and, when particle nuclea tion stops, it levels off. Excellent quantitative agreement can be obtained between theoretical and experimental particle size values. In the experiments of this laboratory the SLS concentration was varied Wfold, the K&Os concentration was varied 140-fold and the difference between theoretical and experimental poly(MMA) particle radii was always Iess than about 20%. Similar good agreement was obtained for polystyrene over the temperature range 30-90°C. Some polystyrene data from the literature with carboxylic soaps give just as good fit as the data with SLS of this laboratory. The predicted proportionality between particle number and the product of 0.6 power of soap concentration and of 0.4 power of initiator concentration was observed for several monomers. The theoretical predictions for the rate and molecular weight obtained in interval I1 are valid only for relatively low initiator and high soap recipes. For recipes for MMA and styrene the rate data are in good agreement with those calculated from the theory. The theory also correctly predicts the order of magnitude of the experimental molecular weights. For several monomers the rate and molecular weight vary with initiator and soap concentrations in a manner close to theoretical predictions. TABLE IValues of the Parameter R of K&Oe Solutions at pIi 3.5 and at Concentration C I

In the peel test the results strongly depend on some variables related to the teat method such as the thickness of the substrate and of the adhesive, rate of testing, geometrical arrangement in the test, testing temperature, composition of the surrounding medium, and method of sample prepam tion. Generally, these variables will change the effective rheological properties of the substrate or the adhesive and may also influence the effective interfacial bond strength. The present study concentrates on the rate of testing and the thickness of the adhesive layer. The chosen testing arrangement is that where two flexible substrate films are peeled apart so that the plane of the inperturbed portion of the laminate is at a right angle to the plane in which the peeling force is applied. Some observations will also be presented concerning the effect of sample preparation. The effects of substrate thickness, testing temperature and the composition of the surrounding medium are not investigated experimentally and these variables are held constant.The substrate film used is cellophane and the binders are acrylic polymers which are applied to the cellophane from aqueous dispersions. These materials were chosen for study because it was desired to learn more about the specific interaction between cellulose and polymers which are used in finishing or bonding of textiles.In the present first part of this study it is shown how the peeling force varies with the peeling rate and the adhesive layer thickness. The nature of the variability of the steady-state force when all testing variables are held constant is also discussed. The following paper, referred to hereafter as Part 11, contains a theoretical analysis of the dependence of the peeling force upon the thickness of the adhesive layer for the case where the force is rate independent. Suitable results of the present report will be discussed in terms of this theory in Part 11.

SynopsisA series of core-and-shell latex particles were made from methyl methacrylate/butyl acrylate copolymers. All latexes were almost monodisperse in particle size. The polymer hardness was varied by changing the methyl methacrylate/butyl acrylate ratio between the limits of 40/60 and 60/40 parts by weight. The minimum film temperatures (MFTs) of these particles were expected to vary with core and shell characteristics in the following order: soft/hard > medium/medium hard/soft. In fact, this order was observed only if the shell thickness was greater than a certain minimum value that depends on the diameter of the core polymer. Thinner, softer shells on harder cores may require higher drying temperatures than thicker shells with the same composition because the former are required to deform more to produce void-free films.