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D. M. Bieliński, M. Kajzer, L. Ślusarski, Ł. Kaczmarek

Gradient structure of polymer materials

Polimery 2005, No 4, 298



Summary

Occurrence of surface gradient of physical or chemical structure of polymeric material has been characterized using selected examples of polyolefin blends [low density polyethylene (PE-LD) and ethylene/propylene copolymers (EPM) with either styrene-butadiene rubber (SBR) or ethylene-propylene-butadiene rubber (EPDM)] as well as sulfuric vulcanizates [SBR or cis-1,4-polyisoprene (IR)]. The results obtained using microscopic methods (AFM, SEM) as well as by microindentation confirm the segregation of low molecular weight PE fraction on the surface of PE blend with rubber. Kinetics of the phenomenon, morphology and structure of a surface layer depend on physico-chemical properties of both components of a blend. Sulfuric vulcanizates show surface gradient of crosslinking density (analysis of chemical structure of space lattice nodes) which results from gradient of temperature in a mold, surface migration of low molecular weight components of crosslinking system and so-called "maturing" of space lattice forming. Possibility of controlling of the courses of phenomena mentioned at the step of plastics processing has been mentioned. The results of microtribological investigations were also presented. They confirm a great importance of surface gradient of the structure from the point of view of operating properties of machine elements made of these materials.


Key words: rubbers, polyolefins, blends, structure gradient, surface layer, functional properties


D. M. Bieliński, M. Kajzer, L. Ślusarski, Ł. Kaczmarek

Gradient structure of polymer materials