Papers by Author: H. Valentova

Abstract: This paper describes DSC, dielectric and dynamic mechanical behavior of linear and crosslinked liquid crystalline (LC) polyurethanes based on LC diols with a mesogenic group in the side chain, diisocyanates of various flexibility and two triols. From our investigations it follows: a) Linear polymers prepared from diols with simple end side chain substituents (as hydrogen, nitro and nitril group) exhibit only amorphous behavior regardless of the structure of used diisocyanate; generally, the most pronounced LC behavior exhibited polymers prepared from a diol with phenyl substituent. b) Investigation of the curing reaction showed that rheological power-law parameters, which are characteristic of the structure at the gel point, are dependent on the initial ratio of the reactants (amount of LC diol in EANCs). c) Strong physical interactions between the mesogens support the cyclization in the course of crosslinking reaction. d) Introduction of chemical junctions (amount of triols) suppresses LC ordering in the networks.

Abstract: This paper deals with the control of the adhesion strength in metal-elastomer joints by fillers and the use of rubber blends to produce advanced high performance adhesive systems. The curing behavior of rubber compounds and dynamic mechanical properties of crosslinked rubber composites were considered in this technologically applicable study. The effects of two types of reinforcing filler, used to increase the adhesion strength between steel and rubber matrix based on acrylonitrile-butadiene rubber (NBR) and chlorosulfonated polyethylene rubber (CSM) was investigated. Precipitated silica (with the average size of primary particle 15 nm) and diatomaceous earth (with the average size of primary particle 28 µm) were used for both rubber and its blend (NBR/CSM). The filler loading range was from 0 to 35 phr. The determination of curing characteristics was estimated by Monsanto Rheometer. The crosslink density of the rubber composites was determined by swelling measurement. Dynamic mechanical behavior was measured by mechanical spectroscopy (in a single cantilever bending mode).