Film Formation Temperature Research Articles

‘Internal plasticisation’ efficiency of a series of acrylic esters with styrene in emulsion copolymers

AbstractThe properties of polymer emulsions are described in which styrene is copolymerised with a range of acrylic esters, together with a minor quantity of acrylic acid. Properties examined included viscosity and minimum temperature of film formation of the emulsions, and the brittle point, rigidity modulus, tensile strength at maximum elongation, and elongation of the air‐dried films. The increase in chain length of the alkyl ester and the quantity of acrylate comonomer both gave more flexible and softer polymers. While approximately equivalent properties may be obtained by replacing one acrylate comonomer by an appropriate quantity of another, each copolymer is unique in its combination of properties.

The relationship between emulsion freeze‐thaw stability and polymer glass transition temperature. I. A study of the polymers and copolymers of methyl methacrylate and ethyl acrylate

AbstractEmulsion polymers and copolymers of ethyl acrylate‐methyl methacrylate containing varying amounts of methacrylic acid were subjected to three freeze‐thaw cycles, following adjustment to a pH of about 9.5 with NH3. The minimum amount of acid required to obtain resistance to freezing and thawing was determined. Values for the glass temperature, (Tg) and minimum film formation temperature (MFT) of the polymer were correlated with the minimum required acid content, indicating that more acid is required as the glass temperature decreases. If a polymer is exceptionally hard so that its particles resist irreversible contact under large forces, it would be expected that little or no acid would be required to obtain freeze‐thaw stability. On the other hand, if the polymer particle is so soft (low Tg) as to readily form aggregates, then very high acid amounts would be required. A plot of minimum weight per cent of acid versus Tg or MFT should, therefore, be hyperbolic approaching zero acid at very high Tg values and approaching very high acid levels at very low Tg values. This is indeed the characteristic of the plot of the experimental data.

Light-Scattering Characterization of Polyvinyl Acetate Latex Films

Light scattering from solid films of polyvinyl acetate latices was studied as a function of particle size distribution, surfactant and stabilizer content, as well as temperature of film formation. The two basic structural parameters from the Debye-Bueche theory were obtained: 〈η2〉, the mean square fluctuation in dielectric constant, and a, the average distance between fluctuations. It was shown that 〈η2〉 was due only to density fluctuations and increased with polyvinyl alcohol stabilizer content. Generally, increasing the temperature of film formation also caused 〈η2〉 to increase. When stabilizer was present the a parameter was of the same order of magnitude as the particle diameter. Over the range of film-forming temperatures, a was relatively constant for a given latex sample. For two of the four systems studied a distinct maximum in the angular scattering was observed. By means of surface replication and electron microscopy, observed packing periodicities in the films could be correlated with the first-order spacings calculated for the angular maxima from the Bragg equation. The data indicate that 〈η2〉 is a useful measure of latex film texture. The polymeric stabilizer seems to form a continuous matrix in which particles are embedded. It is a major factor determining film heterogeneity.

Mechanism of the formation of fluoride films on nickel and their properties

1. In the fluorination of metallic nickel with the interval 540–810°, NiF2 is formed. The kinetics of the formation of the fluoride film within the investigated temperature interval is determined by a diffusion mechanism. 2. The activation energies of the process of formation of NiF2 comprise 59.0 kcal/mole within the temperature interval 540–600° and 18.5 kcal/mole within the interval 720–810°. 3. The dielectric properties of the fluoride film on nickel are determined both by the thickness and by the structure of the film, which is related to the temperature of film formation. 4. The electric strength of the fluoride film on nickel at the same thickness is considerably better in the case of films formed at lower temperatures (540–600°), which is in good agreement with the data on the activation energy and the electron microscopic data. 5. A film of NiF2 is stable to hydrolysis up to the temperature 410°.

Acrylic latex film formation in the critical temperature range

AbstractA shear wave of 15 megacycle frequency and four microsecond duration was made to impinge on the under‐side of a series of ethyl acrylate‐methyl methacrylate copolymer films on fused quartz. Reduction in the reflection coefficient of the pulse provided a direct measure of the increased viscosity and elasticity of the film as it dried, as well as the loss in adhesion which occurred in some cases. Upon reducing the minimum film‐forming temperature (MFT) from 54 to 32°C. by increasing the ethyl acrylate content from 35 to 50%, the adhesion loss was reduced, eventually to zero, depending on the drying rate. Despite the fact that elasticity of the latex particles is the controlling parameter in film quality, a dependence on their viscosity was revealed by this work.

The mechanical properties of latex‐treated papers

AbstractThe effect of the amount and type of latex on the mechanical properties of the paper‐polymer combinations is described in detail. The treatment with latex increases the wet and dry strength properties of the paper considerably, together with improving the folding and tearing resistance. If the polymer in latex is below its film‐forming temperature, however, the beneficial effects of latex treatment are absent. Limitations to varying the rheological properties of plasticpaper combinations are imposed by the comparatively inextensible nature of the paper matrix. Methods of improving the extensibility of paper, including the use of synthetic fiber papers, are discussed, and the time‐dependent nature of the properties are outlined.