Processability of raw elastomers and its relation to deformational and failure behavior

Mill Processability, Rheology and Structure Differences of Polyacrylate Elastomers

Two commercial polyacrylate elastomers, one having epoxide (EP) crosslinking sites and the other ethylidene norbornene (ENB) were selected. It was demonstrated that the former was more difficult to mill-process than the latter. The viscoelastic properties measured at very small strain in shear oscillation indicated that the ENB polymer was more branched than the EP polymer. The gel determination by filteration confirmed this. The tensile stress-strain measurements were conducted at four different deformation rates. These data were treated according to the strain-time correspondence principle to see if this principle applies to the data of these samples. The data of EP polymer did not form a master curve, thus, the above principle is not applicable; at the larger deformation the strain-hardening tendencies were observed. This indicates that the EP polymer has a rather extensive long branching, a type of which usually results from a chain transfer reaction.

The data of the ENB polymer, on the other hand, form a master-curve; that is, the strain-time correspondence principle is applicable, in spite of the presence of the large amount of gel. This means that the gel in the ENB polymer is microgel. The micro-gel in this case is polymer-latex particle, crosslinked during emulsion polymerization with a difunctional comonomer.

Thus, in this work polymer rheology was effectively used to find a major difference in the polymer chain structure. In this way it was shown that the results of polymerization may be related to mill processability.

Influência das características estruturais sobre a processabilidade do polibutadieno alto cis

Características físicas, tais como peso molecular, distribuição de peso molecular e ramificações, têm importância significativa na processabilidade do polibutadieno. Assim, deve haver um balanceamento dessas características a fim de se obter boas propriedades mecânicas e boa processabilidade. Este Trabalho apresenta uma breve revisão sobre a influência das características estruturais na processabilidade do polibutadieno produzido por diferentes sistemas catalíticos. São apresentadas também algumas técnicas encontradas na literatura para melhorar a processabilidade desse elastômero.