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In studying the crack resistance and weathering characteristics of polyethylene, considerable data have been collected which are presented here. The controlling factors and their practical significance are described.

The unusual physical properties of polybutylene are ascribed to details of morphology and a unique crystalline transformation. Inherent properties important for industrial film uses include toughness, low creep, relatively high temperature resistance, stress crack resistance and flexibilty. Four types of packaging applications are described for a new polybutylene resin based on butene-1 monomer. These include industrial film, easy opening tear packages, shrink film, and rotationally molded tanks. A polybutylene shrink film is described having a combination of optical and shrink properties similar to vinyl shrink film, but with mechanical properties typical of polyolefin shrink films. Rotationally molded parts exhibit an unusual degree of toughness, stress crack resistance, and low crystallization stresses in thick parts.

1. Dry grading of sand-gravel mixes during the winter, in combination with special hydraulic stockpiling, is an effective procedure for construction in the northern regions. 2. The quality of the concrete prepared during the winter, with temperatures of the coarse fraction as low as −10°C, is not inferior to the quality of the concrete prepared during the summer. 3. Thermal resistance of the “warm” formwork of 1.5 (m·h·°C)/kcal is sufficient to ensure crack resistance os structures concreted during the winter. For blocks measuring 11×12m, concreted during the summer, it is possible to use “cold” forms to provide additional cooling of the concrete down to temperatures of 10–15°C, before the approach of the winter. 4. To reduce the labor costs involved in the concreting work during the winter, it is necessary to improve and unify the formwork and tent elements.

1. The low strength of glass-fiber ware in tension across reinforcement is a consequence of the low strength of adhesive bonds between the binder and the reinforcing fibers. 2. With increase in tensile load, glass-fiber ware sequentially passes through the states of monolithic character, crack formation in the transversely reinforced layers, and, with further increase in load, separation of the orthogonally reinforced layers. 3. The factor of time substantially lowers crack resistance of glass-fiber ware and amplifies the crack-forming processes. 4. In the biaxial stress state the nature of the crack-forming process depends on the pattern and procedure of loading.