Thermoplastic vulcanizates with an integration of good mechanical performance and excellent resistance to high temperature and oil based on HNBR/TPEE

Abstract

Thermoplastic vulcanizates (TPVs), with a combination of excellent resilience of conventional elastomer and re-processibility of thermoplastic, have been widely explored both in academia and industry in recent years. Herein, a new type of thermoplastic vulcanizates with good mechanical performance, excellent resistance to high temperature and oil has been successfully developed based on hydrogenated acrylonitrile butadiene rubber (HNBR) and thermoplastic polyester elastomer (TPEE) by the masterbatch procedure of dynamic vulcanization. The effect of composition ratio of rubber phase/plastic phase (R/P ratio) on the mechanical properties, rheological properties, micromorphology, thermal stability, high temperature-and oil-resistance of HNBR/TPEE TPV was systematically investigated. The results show that all HNBR/TPEE TPVs exhibit good tensile strength, low hardness, superior stretchability (≥880% elongation at break) and high elasticity (only 13% residual strain when stretched at 50% strain). Interestingly, with the increase in R/P ratio, the hardness of TPVs is decreased linearly and the elasticity increases. Besides, by combining the morphology study and rubber processing analyzer suggest that size of the dispersed rubber phase domains increases significantly as R/P ratio increases, which strengthen the rubber network, creating a better elasticity but reduces the rheological properties of TPVs. In addition, the thermogravimetric analysis shows that the thermal stability of TPV improved with the increase of R/P ratio. HNBR/TPEE TPV shows excellent high temperature-and oil-resistance after aging which is expected to be used in automotive applications.

Effect of dynamic vulcanization time on the performance of thermoplastic vulcanizates based on hydrogenated acrylonitrile butadiene rubber/thermoplastic polyester elastomer

“…The duration of dynamic vulcanization time is directly related to the cross‐linking time and shear action time of the rubber, therefore the different DV times inevitably have a significant effect on the rubber network strength formed in the TPV system 1 . Previous studies and our recent works have shown that due to the unique “sea‐island” phase structure of TPV composite, the cross‐linked rubber particles can be regarded as fillers dispersed within the continuous thermoplastic matrix 38,39 . Therefore the difference in the rubber network strength formed in TPVs with different DV times can be investigated by RPA strain scanning mode, with the results shown in Figure 2.…”

“…Figure 1 shows the process for preparing HNBR/TPEE‐TPVs with the HNBR/TPEE mass ratio of 60/40, an optimum composition demonstrated by our previous work 38 . The first step was to thoroughly mix HNBR and DBPH (an effective peroxide cross‐linking agent, the dosage is 1.5 phr with regard to HNBR) in the internal mixer equipped with two counter‐rotating rotors (HAAKE PolyLab OS and Rheomix OS, Thermo Fisher Scientific) at room temperature to obtain the HNBR masterbatch, an optimum procedure 39 .…”

“…To investigate the variation in the network structure of HNBR rubber particles formed in the TPV system during the DV process, the rubber particles network strength of HNBR/TPEE‐TPVs with different DV times was characterized by a rubber processing analyzer (RPA 2000, Alpha Technologies, US), and the detailed test procedures refer to our previous works 38,39 …”

“…Oil aging tests were conducted on rectangular TPV test specimens using IRM903 reference oil at 125°C for 72 h by ISO 1817:2011. Referring to previously reported studies, 22,38,39 the change in weight (Δ W ) and volume (Δ V ) of the specimens before and after oil immersion was measured to assess the oil resistance of HNBR/TPEE‐TPVs.…”

“…To develop high‐performance HNBR/TPEE‐TPVs with a homogenous phase structure in a more efficient way, the investigation into the dynamic vulcanization time (DV time), which is one of the processing conditions for TPV preparation, is the focus of this paper. Building on our previous works, 38,39 five different DV times were selected in the masterbatch preparation procedure of HNBR/TPEE‐TPVs. The effect of DV time on the mechanical properties, rheological characteristics, thermal stability, heat resistance, and oil resistance of TPVs was systematically investigated.…”