Propriedades mecanicas e termicas, morfologia e reologia de blendas de poliamida-6 e elastomeros

AUTOR(ES)
DATA DE PUBLICAÇÃO

1999

RESUMO

Blends of polyamide-6 (PA-6) and elastomers is the central subject of this thesis. The work can be subdivided in three parts according to the type of rubber used, each part has specific objectives. In the first part, the mechanical properties and phase morphology of ternary blends of polyamide 6 with rubber, e.g., maleated ethylene-propylene random copolymer (EPR-g-MA) or maleated styrene-(ethylene-ran-butylene)- styrene (SEBS-g-MA), and a rigid but brittle imidized acrylic polymer (IA) are explored. The objective was to investigate blends which have independently dispersed rubber and rigid polymer particles in a polyamide 6 matrix. The amount of rubber was fixed at 20%, while the IA to polyamide 6 ratio was varied. Addition of imidized acrylic polymer particles to nylon 6 toughened by EPR-g-MA particles leads to increased stiffness and room temperature impact strength and does not change the ductile-to-brittle transition temperatures up to a critical level. Similar improvements on stiffness and room temperature impact strength were found for nylon 6 toughened by SEBS-type rubber, however the same good low temperature impact properties were not observed. In the second part, the rheology, thermal and dynamic-mechanical properties and phase morphology of blends of polyamide 6 with natural rubber are explored. The objective was to investigate in situ formation of a graft copolymer between natural rubber and polyamide 6 during processing. Addition of maleic anhydride to the rubber phase was done prior to blending with polyamide 6. During processing maleic anhydride can react with both natural rubber and polyamide 6 leading to a graft copolymer formation. Molau test was used to confirm the graft copolymer formation. Rheology and thermal properties as well as dynamic-mechanical analysis also indicated the graftization. Blend morphology analysis showed a significant reduction in particle size with the addition of maleic anhydride to the rubber phase. In the last part, the copolymer poly(ethylene oxide-b-amide 6), PEBAX®, was tested as a compatibilizer agent for blends of PA-6 and a core-shell copolymer formed by a n-butyl acrylate core and an acrylic shell. At this time, there are only two chemical strategies to obtain core-shell modifiers effective for toughening PA-6: (i) addition of a compatibilizers that are able to interact with the acrylic shelI and chemically react with PA-6 or (ii) modifying the shell so that it can react with the matrix. The objective in this part of the work was to investigate if good core-shell dispersions could be obtained by physical interactions. Mechanical properties and rheology of the PA-6/core-shell blends were studied. Morphology analysis of these blends indicated that the dispersion of the core-shell particles was improved with the addition of PEBAX, which can interact physically with both matrix and shell through its poly(ethylene oxide) blocks.

ASSUNTO(S)

borracha elastomeros

ACESSO AO ARTIGO

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