Advances in Manufacturing a New Cable Coating Resistant to Thermal Aging and γ Rays by Cobalt-60 up to 50 KGy

Poly(vinyl chloride) (PVC) is widely used for covering electrical cables, but a decrease in its physicochemical, thermal, and mechanical properties has been observed over time. Poly(nitrile butadiene) rubber (NBR), due to its certain properties, was chosen to be blended with PVC to improve its specific properties, when used as insulation for electrical cables installed in nuclear power plants. Thus, this work focuses on the effect of γ radiation at doses ranging from 10 to 50 KGy on the physicochemical, thermal, morphological, and mechanical properties of PVC, as well as on the improvement of its properties by the incorporation of NBR in the PVC matrix as a blend. A series of PVC/NBR blends containing 10, 20, 30, 40, and 50 wt % NBR was prepared and subjected to thermal aging at 80 °C after adding appropriate additives. The results obtained reveal that thermal aging at 80 °C and exposure of the PVC/NBR blend to γ radiation up to 50 KGy do not practically affect the properties of this material.

Phase-Separated Structure of NBR/PVC Blends with Different Acrylonitrile Contents Investigated Using STEM-EDS Mapping Analysis

We investigated the phase-separated structure of nitrile butadiene rubber (NBR)/polyvinyl chloride (PVC) blends with different acrylonitrile (AN) contents in the NBR, using dynamic mechanical analysis measurements and scanning-transmission-electron-microscopy (STEM)-energy-dispersive-X-ray-spectroscopy (EDS) elemental analysis. Two separate sharp tan δ peaks were observed in the blend at the lower AN content of 18.0%, whereas a broad peak was observed in the blends with the higher AN contents of 29.0 and 33.5%, due to the increase in miscibility, as expected from the decrease in the solubility parameter difference with the increasing AN content. The STEM-EDS elemental analysis for the concentration distribution showed that the NBR was mixed in the large PVC domains with a diameter of several micrometers, and the excluded PVC existed around the interface of the domain-matrix phases in the blend with the lower AN content, whereas small domains with a diameter of several tens of nanometers were dispersed in the blend with the higher AN content. The concentration difference in PVC between the PVC domain and the NBR matrix became smaller with increasing miscibility as the AN content increased although the blends contained the same PVC content of 40 wt%.

Partial Miscibility and Concentration Distribution of Two-Phase Blends of Crosslinked NBR and PVC

We found that the blends of nitrile butadiene rubber (NBR) and polyvinyl chloride (PVC) exhibited lower critical solution temperature (LCST)-type phase behavior in which a single-phase blend tends to phase separate at elevated temperatures when the acrylonitrile content of NBR was 29.0%. The tan δ peaks, which originated from the glass transitions of the component polymers measured by dynamic mechanical analysis (DMA), were largely shifted and broader in the blends when the blends were melted in the two-phase region of the LCST-type phase diagram, suggesting that NBR and PVC are partially miscible in the two-phase structure. The TEM-EDS elemental mapping analysis using a dual silicon drift detector revealed that each component polymer existed in the partner polymer-rich phase, and the PVC-rich domains consisted of aggregated small PVC particles the size of several ten nanometers. The partial miscibility of the blends was explained by the lever rule for the concentration distribution in the two-phase region of the LCST-type phase diagram.

In Situ Zirconia: A Superior Reinforcing Filler for High-Performance Nitrile Rubber Composites

Zirconia particles are generated into a nitrile rubber (NBR) matrix via a solution sol-gel method in a controlled manner. Formation of zirconia particles from their precursor (zirconium(IV) propoxide) occurs under optimized reaction conditions. As a result, the nanoparticles are embedded and well dispersed in the NBR matrix that results in a remarkable improvement in mechanical and thermal properties of the composite. Such reinforcement is not realized when the composites are prepared following the conventional technique of filler loading by physical mixing, although the filler content remains the same. Use of a surface active coupling agent TESPT (bis-(3-triethoxysilylpropyl) tetrasulfide) in the reactive sol-gel system is found to further boost the mechanical performance of the composites. In order to ensure the practical application of the developed composites, a series of studies have been performed that consist of dynamic performance, swelling, thermal degradation, and resistance to oil, ozone, and abrasion. Analysis of the results reveals that in situ zirconia could be an excellent filler for the NBR composites to withstand in a harsh and adverse environment.

Polyisoprene-Silica Nanoparticles Synthesized via RAFT Emulsifier-Free Emulsion Polymerization Using Water-Soluble Initiators

Polyisoprene-silica (PIP-co-RAFT-SiO₂) nanoparticles were prepared via reversible addition⁻fragmentation chain-transfer (RAFT) emulsifier-free emulsion polymerization using water-soluble initiators, 4,4'-Azobis (4-cyanopentanoic acid) (ACP) and 2,2'-Azobis (2-methylpropionamidine) dihydrochloride (V50). The particle size of emulsion prepared using ACP initiator was smaller than that using V50 initiator because the V50 initiator was more active toward decomposition than the ACP initiator. A high monomer conversion (84%), grafting efficiency (83%) and small particle size (38 nm) with narrow size distribution were achieved at optimum condition. The PIP-co-RAFT-SiO₂ nanoparticles exhibited core⁻shell morphology with silica encapsulated with polyisoprene (PIP). The new PIP-SiO₂ nanoparticles could be applied as effective filler in rubber composites that possess good mechanical and thermal properties.

Controlled growth of in situ silica in a NR/CR blend by a solution sol–gel method and the studies of its composite properties

Controlled loading of in situ silica in NR/CR blend by solution sol–gel method for enhancing the reinforcement.