Antiplasticization and transition to marked nonlinear viscoelasticity in poly(vinyl chloride)/acrylonitrile–butadiene copolymer blends

A series of PVC/NBR blends with varying acrylonitrile (AN) content in the NBR has been studied in uniaxial tension creep tests. The tests have been carried out at 21.5 ± 0.5°C covering creep times from 10 to 1000 sec. NBR with low AN content, having poor compatibility with PVC, gives the blends with higher compliance and increased time dependence of the compliance. A higher AN content in the NBR gives the blends with the opposite properties when the NBR is added in small amounts. NBR with 40 wt-% AN is found to act as an antiplasticizer giving minimal creep compliance when 7 wt-% NBR is added. The antiplasticization reveals a considerably increased stress level at which the transition from approximatively linear to marked nonlinear viscoelasticity occurs and a decreased stress dependence of the creep compliance in the nonlinear viscoelastic range. Since the antiplasticization is also associated with a suppression of the β-transition mechanism, the results provide a demonstration of the importance of β-mechanism in the stress activated processes responsible for the appearance of nonlinear viscoelasticity in solid polymers.     

A liquid autocollimation refractometer

A liquid refractometer based on a digital autocollimator is described. The results of an investigation, estimates of the errors in measuring the refractive index of liquids, and an example of its use to determine the concentration of aqueous solutions of sodium chloride are presented. __________ Translated from Izmeritel’naya Tekhnika, No. 8, pp. 50–53, August, 2006.     

Transferred electron effects in n-GaAs and n-InP under hydrostatic pressure

Experimental results are presented showing the variation of the peak velocity, electric field at peak velocity and saturated velocity of the velocity-field curve for bulk n-GaAs under hydrostatic pressure. Similar data are presented for the field at peak velocity for bulk n-InP. The extraction of the data from the current-voltage characteristics is based on an exploitation of the influence of boundary conditions on the manifestation of transferred-electron induced (Gunn) current instabilities. Our results, which differ from those of other investigations, are compared with our Monte Carlo calculations of the velocity-field curves for these materials. We find that ionized impurity scattering plays an important role in the understanding of our data.