| Polyvinyl chloride(PVC)/acrylonitrile–butadiene rubber(NBR) thermoplastic elastomer(TPE) prepared by the method of dynamic curing possesses the elasticity and oil resistance of NBR, and the processability and weather resistance of PVC to some extent. It is used in many fields such as electrical wires and cables, seals and gaskets, etc. The types of PVC and NBR play an important role on properties of TPE. Therefore, it is important to study on the effect of the acrylonitrile(AN) content of NBR and the degree of polymerization(DP) of PVC on the stucture and properties of TPE. Besides, the addition of carbon nanotube(CNT) and other functional fillers can endow TPE with microwave absorbing property and thermal conductivity, which is an effective way to broaden the applications of TPE.The effect of AN content of NBR and DP of PVC on the properties of PVC/NBR TPE are investigated. The higher the AN content is, the better the dispersion of NBR in PVC becomes. As the AN content of NBR increases, the tensile strength and the elogation at break of TPE increase, while the crosslink density of NBR in TPE decreases. As the AN content of NBR increases from 26% to 29%, the tensile strength of TPE increases from 3.3 MPa to 9.0 MPa, and the elogation at break increase from 308% to 517%. As the DP of PVC increases, the tensile strength and stress at 100% extension of TPE increase, while the compression permanent set decreases. The hardness and the resilience have slight change. As the DP of PVC increases from 800 to 2000, the tensile strength of TPE increases from 9.3 MPa to 12.3 Mpa, and the elongation at break decreases from 675% to 425%.PVC/NBR/MWCNT composites are prepared by premixing MWCNT with PVC and premixing MWCNT with NBR, respectively. The dispersion of MWCNT in the composite with premixing with PVC is better than that in the composite with premixing with NBR, resulting in the composite with premixing with PVC shows higher DC conductivity than the composites with premixing with NBR at the same MWCNT content. Compared with premixing MWCNT with PVC, Premixing MWCNT with NBR is preferable to improve the mechanical properties, for the composites. The effect of two different processing methods on the dielectric and microwave absorbing properties of PVC/NBR/MWCNT composites are studied. Premixing MWCNT with PVC is more beneficial to increase the real part and the imaginary part of permittivity and microwave absorbing performance than premixing MWCNT with NBR at the same MWCNT content. PVC/NBR/MWCNT(35.9/35.9/6) composite with premixing with PVC has the minium reflection loss(RLmin) of-49.5 d B and-10 d B absorbing bandwidth of 3.0 GHz, while PVC/NBR/MWCNT(35.9/35.9/6) composite with premixing with NBR has the RLmin of-4.2 dB.The effect of SiC on the properties of PVC/NBR/MWCNT composite is studied. Incorporating SiC into the PVC/NBR/MWCNT(35.9/35.9/8) composites can increase the real part and imaginary part of permittivity of the composites, leading to impedance mismatch at air-material interface and the decrease of the microwave absorbing property of the composite. Adding SiC into PVC/NBR/MWCNT(35.9/35.9/4) composite decreases the imaginary part of permittivity of the composite, while the real part of permittivity have slight change, leading to the decrease of dielectric loss and microwave absorbing property.The effects of hybrid fillers including MWCNT/boron nitride(BN), MWCNT/flake graphite(FG), MWCNT/ acetylene black, MWCNT/ zinc oxide(Zn O) on the properties of PVC/NBR TPE are studied. Compared with other hybrid fillers, MWCNT/FG is favorable to increase the thermal conductivity of TPE. The thermal conductivity of the PVC/NBR/MWCNT/FG(35.9/35.9/8/60) composite is 0.90 W/(m·K). Silane coupling agent is used for the surface treatment of BN. Compared with PVC/NBR/MWCNT/BN composite, the thermal conductivity of PVC/NBR/MWCNT/modified BN composite is lower, while the tensile strength is higher. |
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