Thermoplastic elastomers from chlorinated polyethylene/nylon terpolyamide blends

Blends of chlorinated polyethylene (CPE) and Nylon terpolyamide (PA) were prepared with different ratios. It is generally known that CPE has intrinsic properties of heat, oil and oxidation resistance, so the obtained materials are well suitable in the hose, pipe and seal industry. CPE was strengthened by a 6,6-6,12 co-polyamide with the glass transition temperature slightly above room temperature and a particularly low melting temperature, that allowed to obtain the blends by typical industrial processes of mixing, milling and injection molding. Mechanical and rheological properties were investigated both with tensile tests and dynamic mechanical analysis: the results showed that CPE and PA form phase separated systems with excellent compatibility as the strength and modulus were improved. The thermal and mechanical behavior of the blends is that typical of thermoplastic elastomers. The comparison of the FTIR spectra of the blends in respect of linear combination of those of the component polymers allowed the detection of differences attributed to the existence of interactions at the interface responsible of the enhanced mechanical properties. These results were corroborated by time-domain proton NMR experiments, with an improved method for the measurement of the hard/soft ratio in phase separated systems. With the aim to resolve the morphology of the blends, samples were studied with laser scanning confocal fluorescent microscopy (LSCFM). CPE rubber was homogeneously labeled with a fluorescent dye by solution treatment and then blended with PA in order to increase the contrast between phases in fluorescent microscopy. Scanning Electron Microscopy and Atomic Force Microscopy techniques were used to confirm the data collected with LSCFM. A continuous and interpenetrating structure of the two phases is finally revealed for the blend with the best mechanical properties.Blends with co-continuous structures may combine the properties of both components in a favorable way. For example, a co-continuous structure leads to the maximum contribution of the mechanical modulus from each component simultaneously. Synergistic effects have also been shown in mechanical properties. Constituting a stable co-continuous morphology just mixing two polymers it is not that easy, and even more difficult is to detect such microstructure within the bulk of the material. For these two reasons, cocontinuous polymer blends are an interesting and challenging research topic. In addition, these co-continuous structures offer promising opportunities for improving properties and creating tailor-made materials. For these reason, and also as very few examples of Thermoplastic elastomers based on Chlorinated polyethylene and Nylon are present in the literature, the project for this thesis came to life. This work is aimed at the achievement of a material with thermoplastic elastomeric mechanical and processing properties, for which the structure properties relationships would be completely understood and explained as due to synergistic interfacial interaction between phases and cocontinuous morphology within them.