Influence of degradation process on rheological characteristics of polymer materials

Rheological properties of thermoplastic polymer materials before and after exposure in chemical solution were evaluated using Frequency sweep test, which monitors changes in viscoelastic properties of polymers with respect to their molecular structure and their behavior in thermoplastic processes. As experimental material thermoplastic polyethylene and polypropylene samples were used and subjected to influence of n‑hexane solution for period of 3 and 6 months. Measurements were performed using oscillating rheometer Physica Rheometer MCR 301 and carried out at the temperature of 160 °C and 180 °C. Degradation process resulted in changes of complex dynamic viscosity, storage and loss modulus, changes in molar mass and its distribution which sufficiently prove the rheological changes.</p

CORROSION OF COPPER PIPES JOINTS IN SIMULATED OPERATING CONDITIONS

<em>Joining of copper pipes used for liquid media transport are made as demountable and fixation joints. This work deals with corrosion behavior of the joints made by soft soldering, hard soldering and fitting. Corrosion properties of the joints were studied after 11 month exposition in conditions simulated the operating environment. The experiment was made in the 3% NaCl solution, at temperature 20° C for 16 hours and at 80° C for 8 hours per day, the solution was flowing 8 hours by the average rate 0,27 m.s^-1. Evaluation of the joints corrosion attacks was made visually, by light and electron microscopy with chemical analyses of corrosion products.</em><span> </span