Dynamic Mechanical Properties Of Films Research Articles

Application of the Hofmeister series to the structure and properties of poly(vinyl alcohol) films containing metal salts

The effects of ions on the structures and properties of poly(vinyl alcohol) films were systematically studied using various metal salts. Although cations play an important role, the data obtained in this study demonstrated that the strong ion–dipole interactions between anions and poly(vinyl alcohol) chains also have a significant impact on crystallinity and glass transition temperature. For the first time, the study revealed that the impact of the added salts follows the Hofmeister series. Investigations of various bromine salt cations revealed that Li+ is more effective at disrupting the water structure than either Na+ or K+. Further experiments using lithium salts with various anion species verified that lithium salts play an important role in determining the crystallinity and hydrogen bonding within aqueous poly(vinyl alcohol) and therefore affect the dynamic mechanical properties of films. This phenomenon clearly follows the order LiClO4 > LiI > LiBr > LiNO3 > LiCl, which corresponds to the Hofmeister series. The salt addition affects the structure and properties of poly(vinyl alcohol) films as it reduces the hydrogen bonding in PVA chains and decreases the crystallinity. Consequently, the Tg shifts to low temperatures, and the modulus beyond Tg decreases markedly. This study confirmed that the impact of bromine salts on the structure and properties followed the order of Hofmeister series, i.e., Li+ > Na+ > K+. Although cations play an important role, the data obtained also demonstrated that the strong ion–dipole interactions between anions and PVA chains have a significant impact on the crystallinity and Tg.

Dynamic mechanical analysis of multiblock (segmental) polyesterimides

Thermal, deformation-strength, and dynamic mechanical properties of films of segmental polyesterimides prepared from pyromellitic anhydride, aromatic diamines, and poly(butylene adipate) (M n = 1000) with hydroxy terminal groups were studied. The glass transition points T g of the samples obtained are below 0°C. The dynamic elastic modulus curves at temperatures higher than T g are characterized by a portion in which the modulus only weakly depends on temperature.

Thermal analysis of fibres and films in solvents and vapours

The thermomechanical and dynamic mechanical properties of films and fibres in vapour laden atmospheres and simulated dye baths were investigated in order to understand their processing behaviour. Acetone and water vapour acted as plasticisers for cellulose acetate film. 2-phenoxyethanol was found to penetrate poly(ethylene terephthalate) film above its glass transition temperature and consequently depress its glass transition temperature. The use of “carriers” to enhance the rate of dyeing of acrylic fibre was investigated. The increase in coloration was found to be proportional to the degree of plasticisation caused by the candidate compounds.

Dynamic Mechanical and Thermal Analysis for the Determination of RFL Morphology

Abstract From dynamic mechanical and DSC studies, we have concluded that resorcinolformaldehyde-latex (RFL) adhesive systems are two-phase materials. This is consistent with the limited electron microscopy work published on these polymers. However, while finer details of RFL morphology have never been resolved by electron microscopy, a comparison of the dynamic mechanical results with theoretical models provides evidence that the RFL has an interpenetrating network (IPN) morphology. The resorcinol-formaldehyde thermoset provides a continuous glassy network, while the butadienestyrene-vinyl pyridine terpolymer latex forms a continuous rubbery phase at ordinary use temperatures. The mechanical properties of the IPN are dominated by the volume fraction, chemistry, and thermal history of the RF thermoset. The dynamic mechanical properties of films made from ammonia-containing RFL adhesives are particularly sensitive to thermal history. This is consistent with the long-accepted belief that ammonia forms therma...

Dynamic Response of Viscoelastic Solids in Liquid Media

A theoretical and experimental investigation of the dynamic mechanical properties of polymeric films in liquid media has been conducted. In an analytical development the effect of a viscous medium surrounding the specimen on the dynamic mechanical measurement is determined by calculating the viscous drag on the specimen which is subjected to a sinusoidal oscillation; this result is incorporated with the dynamic modulus analysis. The resulting expressions are demonstrated to predict the effective dynamic mechanical properties of films in liquid media by knowing the dimensions, viscosity, and density of the liquid and the frequency of oscillation. In order to separate the viscous drag from any polymer-solvent interactions, a series of experimental studies using the Vibron instrument was conducted to measure the effective dynamic mechanical properties of films in a variety of noninteracting liquid media and dry conditions. The resultant dry measurements were used along with the theory to show the effect of viscous drag on the dynamic mechanical properties of a film in a liquid medium.