Rolf Buchdahl

Mechanical and Electrical Properties of Plasticized Vinyl Chloride Compositions

The temperature dependence of the dynamic mechanical and a.c. electrical properties of a given polyvinyl chloride plasticizer composition can be characterized by two quantities: (a) the transition temperature which is defined as the temperature of maximum dissipation factor and (b) the half‐widths of the loss factor‐temperature curve. A simple relationship exists between the transition temperature determined mechanically or electrically and the volume fraction of a compatible plasticizer. The modification of this relationship for non‐compatible plasticizer has been indicated. The half‐width is a function of the volume fraction of the plasticizer, although this relationship is not as simple as the one obtained for the transition temperature. A simple correlation exists between the electrical and mechanical half‐width. The compliance measured in tensile creep has been found to be a function of the applied load and the compliance‐load relationship varies depending on the region in which the material finds it...

Mechanical Properties of Oriented Polystyrene Film

Cast films of polystyrene were oriented by stretching at temperatures above the softening temperature of the material and then cooled. A factorially designed experiment was carried out in which the amount of stretching, temperature of stretching, time held in the stretched state before cooling, and effect of several cycles of stretching before cooling were investigated as they affect the birefringence, the stress‐strain properties, dynamic modulus and damping, and the softening temperature of polystyrene.The values of many of the mechanical properties are more closely related to the birefringence than to the amount of hot stretching. In general, the value of the stress‐strain properties in the direction of hot stretch, the dynamic modulus, and the birefringence all increase with an increase in the amount of stretching, a decrease in temperature, an increase in rate of cooling after stretching, and a decrease in the number of times the film was stretched before finally cooling. The softening temperature is...

Dynamic Mechanical Properties of a Number of Elastomers and Related Polymers from 4 to 250 °K

Youngs modulus and mechanical damping have been measured down to 4 °K for cis‐ and trans‐polybutadienes, cis‐ and trans‐polyisoprenes, butyl rubber, and random SBR copolymers. Trans‐polybutadiene has two large damping peaks below Tg, trans‐polyisoprene one peak, while the cis‐polymers and butyl rubber show either no damping peaks or only very small ones below Tg. The low‐temperature damping peaks of the trans‐polymers might be explained by a type of crankshaft motion and by a special motion of the trans‐monomeric unit which involves a simultaneous libration and bond angle deformation. The high Youngs moduli of the polybutadienes compared to the polyisoprenes and the SBR copolymers are explained by the good molecular packing of the polybutadienes.

The Application of Nutting's Equation to the Viscoelastic Behavior of Certain Polymeric Systems

The Nutting equation e=ψ×σβ×tn, where e=strain, σ=stress, t=time, and ψ, β, and n are material constants, is applicable to a large number of polymeric systems, such as plasticized polyvinyl chloride, styrene‐butadiene copolymers, polystyrene. It has been shown that the material constant n is closely related to the damping coefficient as obtained from dynamic mechanical measurements The temperature dependence of n and δ (damping coefficient) are about the same; and, in some cases, there exists a simple quantitative relationship between the two constants. A mathematical derivation of the relationship between n and δ is given and a physical interpretation of the dimensional changes in the Nutting equation, in terms of complex moduli, is presented. Furthermore, it is shown that, in the case of styrene‐butadiene copolymer, n varies with the differences in gel content and gel structure.

Viscoelastic and photoelastic properties of polystyrene above its softening temperature

Abstract Creep, recovery, and stress-relaxation experiments with simultaneous measurements of birefringence have been carried out on polystyrene films above their softening temperature. The ratio of birefringence to stress is a constant independent of the stress, elongation, temperature, and molecular weight of the polystyrene. The data indicate that polystyrene has a semipermanent network structure. The network is most likely caused by the strong intertwining of the polymer molecules.

The Relationship Between the Rheological Properties and Working Properties of Printing Inks

It is shown that the working properties of a printing ink, i.e., its performance during the printing operation, can be interpreted in terms of the rheological properties as measured in a rotational viscosimeter. The instrument used in this investigation is a viscosimeter of the Stormer type. Data are presented to show that it is necessary to distinguish between time‐dependent and time‐independent flow phenomena. Various theories suggested to explain the time‐independent flow phenomena are discussed briefly. The flow of a printing ink over the main mechanical elements of a typographic printing press is analyzed and correlated with simple flow phenomena which can be measured in a rotational viscosimeter.