Changes In Dynamic Mechanical Properties Research Articles

Interaggregate Interaction in Filled Rubber

Abstract Measurements of the dynamic properties of carbon-black-filled rubber can be carried out on most instrumentation at strains within the limits of linear behavior; thus, assessments of acoustic performance can readily be made. The equivalence of small-strain dynamic-mechanical testing and acoustic measurements has been demonstrated herein. Blends of NR with a high concentration of 1,2-BR are attractive candidates for damping applications because of the extended frequency range of the glass to rubber transition. One approach to improving the magnitude of the damping is to incorporate high levels of carbon black into the material. Significant interaggregate interaction, promoted for example by a low degree of carbon-black dispersion, will amplify the energy dissipation. The strain dependence of the dynamic properties implicit in such an approach can result in a damping performance sensitive to deformation. The loss tangent rises significantly after such a deformation, while the loss modulus experiences a barely measurable decline. This sensitivity to deformation will thus impact more on constrained layer damping applications than on simple extensional damping. For the materials tested in the present study, complete recovery of the damage to the carbon-black network (which engenders the changes in dynamic mechanical properties) required more than a day at room temperature.

Variation of dynamic mechanical properties of polycarbonate as a result of deformation

AbstractA combination of different experimental apprati has allowed dynamic mechanical spectroscopic measurements to be made as function of variable, constant offset stress, as well as during creep of bisphenol‐A‐polycarbonate. The deformation system was calibrated with aluminum and by comparison of low‐stress dynamic mechanical spectra with literature data of polycarbonate. Dynamic mechanical spectra acquired at high offset stress result in an apparent shift in sub‐Tg relaxation processes to higher temperatures at differing rates, resulting in separation of the various relaxation processes. This observed phenomenon is analogous to similar effects that are observed viathe application of pressure. The creep process can be clearly monitored by changes in dynamic mechanical properties, with these changes being dependent upon the stress and temperature utilized.

Property‐morphology relationships of polymethylmethacrylate/polyvinylidenefluoride blends

AbstractAn investigation was conducted to establish property‐morphology relationships in polymethylmethacrylate/polyvinylidenefluoride (PMMA/PVDF) blends. All blends were compounded in a twin‐screw extruder and then processed by injection molding Mechanical properties of blends of various compositions were studied by dynamic mechanical and impact strength measurements. The presence of crystalline regions in blends was determined by Differential Scanning Calorimetry (DSC). Morphology of fracture surfaces of blends was studied by Spinning Electron Microscopy (SEM). PMMA/PVDF blends were found to form compatible mixtures over a wide range of blend composition. Changes in dynamic mechanical properties upon annealing were found to be a direct function of blond morphology. Electron microscopic evidence showed no signs of phase separation. DSC measurements detected crystalline regions in all blends containing 40 percent or more (by weight) PVDF.

Dynamic mechanical properties of the Russet Burbank potato as related to temperature and bruise susceptibility

An electro-mechanical vibration exciter and a dropped weight impact device were utilized to determine changes in dynamic mechanical properties of the Russet Burbank potato as influenced by temperature. The vibration exciter was utilized to study the compressive stress-strain relationship for core samples of tuberin the frequency range of 50 to 300 Hz and for temperatures from 35 to 85°F (2 to 30°C)