Search

In order to investigate the influence of a hot-pressing process on the mechanical properties of ultra-high molecular weight polyethylene (UHMWPE) fiber non-woven fabrics with stretch and in-plane shear, UHMWPE non-woven fabric samples were prepared by adjusting the temperature, time, and pressure of the hot-pressing process, and mechanical property tests were carried out so as to clarify the influence of the hot-pressing process on the mechanical properties of the samples. The results show that the hot-pressing process mainly affects the silk–glue bonding strength of the samples; in the test range, with the increase in hot-pressing temperature and time, the tensile strength and in-plane shear strength of the samples increase and then decrease, and the best mechanical properties are obtained at 130 °C and 7 min of hot pressing, respectively; at 130 °C, the in-plane shear strength is 39.94 MPa and the tensile strength is 595.43 MPa; at 7 min, the in-plane shear strength is 63.0 MPa and the tensile strength is 643.30 MPa; with the increase in the hot-pressing pressure, the in-plane shear strength of the samples increases and then decreases, and the highest is 52.60 MPa, achieved at 8 MPa; in the range of 5–8 MPa, the tensile strength of the specimens did not change significantly, and increased significantly at 9 MPa, reaching a maximum strength of 674.55 MPa. [ABSTRACT FROM AUTHOR]

The physical blending method was used in order to prepare nitrile-butadiene rubber/polyamide elastomer/single-walled carbon nanotube (NBR/PAE/SWCNT) composites with better thermal-oxidative aging resistance. The interactions between SWCNTs and NBR/PAE were characterized using the Moving Die Rheometer 2000 (MDR 2000), rheological behavior tests, the equilibrium swelling method, and mechanical property tests. The 100% constant tensile stress and hardness of NBR/PAE/SWCNT composites increased from 2.59 MPa to 4.14 MPa and from 62 Shore A to 69 Shore A, respectively, and the elongation decreased from 421% to 355% with increasing SWCNT content. NBR/PAE/SWCNT composites had improved thermal-oxidative aging resistance due to better interactions between SWCNTs and NBR/PAE. During the aging process, the tensile strength and elongation at break decreased with the increase in aging time compared to the unaged samples, and the constant tensile stress gradually increased. There was a more significant difference in the degradation of mechanical properties when aged in a variety of oils. The 100% constant tensile stress of NBR/PAE/SWCNT composites aged in IRM 903 gradually increased with aging time while it gradually decreased in biodiesel. The swelling index gradually increased with increasing SWCNT content. Interestingly, the swelling index of the composites in cyclohexanone decreased with the increase in SWCNT content. The reasons leading to different swelling behaviors when immersed in different kinds of liquids were investigated using the Hansen solubility parameter (HSP) method, which provides an excellent guide for the application of some oil-resistant products. [ABSTRACT FROM AUTHOR]

The study on swelling behaviors of rubber products in liquid media is of great value for life prediction and practical application guidance. In this work, changes in the mechanical properties of hydrogenated nitrile rubber/ethylene propylene diene monomer (HNBR/EPDM) blends caused by swelling in aviation hydraulic oil YH‐15 were studied. Effects of two kinds of carbon black, N220, and N990, on the tensile properties of HNBR/EPDM blends at both unswollen and swollen states were investigated. The results turned out that N220 exhibited better reinforcing effects than N990 on HNBR/EPDM blends. The tensile properties of unfilled and filled HNBR/EPDM blends decreased rapidly at first and then tended to stabilize with the extension of swelling time in YH‐15, while the modulus at 100% declined firstly and then increased. After swelling for 72 h, the tensile strength of HNBR/EPDM blends filled with N220 decreased by more than 35%, and by comparison, it decreased by about 20% for the N990‐filled HNBR/EPDM blends. The cross‐sections of the tensile samples after swelling changed greatly compared with the unswollen samples. In addition, the effect of swelling on the hardness of the HNBR/EPDM blends was not obvious. [ABSTRACT FROM AUTHOR]

Equilibrium swelling and rheological tests were adopted to systematically investigate the effects of softener type and dosage on the crosslink densities. The results turned out that the chemical crosslink density could be distinguished from the physical crosslink density by comparing the results of equilibrium swelling and rheological tests. The liquid butadiene (LB) as a softener leads to the greatest reduction in crosslink density, followed by polyethylene wax (PW) and paraffinic oil (PO). The tensile strength decreases with increasing PO content while shows peak values with increase of LB and PW contents. The dependencies of chemical crosslink density on the aging time under 150°C are quite different for the three softeners, which can be expected from the double crosslinking networks consisting of small softener and large main crosslinking networks. Further investigation has been performed to correlate the tensile strength with chemical crosslink density of ethylene propylene diene monomer elastomer vulcanizates. Three different linear relationships can be obtained for the softeners independent of the aging time. It can now be expected from this study that the role of some new softeners in rubber compounds is not only confined to plasticization but also forms crosslinking networks in the peroxide‐cured rubbers. [ABSTRACT FROM AUTHOR]

• Change in tensile strength of NBR/PAE improves from −28% to −6% aged at 110 ℃/168 h. • NBR/PAE exhibits higher retention of tensile strength after thermo-oxidative age. • Possible crosslink network of NBR/PAE is analyzed based on mechanical properties. • The swelling behavior of NBR/PAE in oils can be well predicted by the HSP method. Temperature-induced degradation of nitrile butadiene rubber (NBR) can negatively affect its mechanical properties. Further improvement in the aging resistance of the elastomer is required in view of the stringent application requirements. Polyamide elastomers (PAE) were used as reinforcing agents of NBR to prepare NBR/PAE blend by physical blending. Interaction between NBR and PAE was investigated using FTIR, DMA, SEM and swelling test. After aging at 110 and 130 °C for 7 days, NBR/PAE blend exhibited the minimum change of tensile strength. The reason why NBR/PAE blend could maintain excellent tensile strength retention during thermo-oxidative aging was investigated. Finally, the swelling behavior of rubbers in biodiesel and IRM 903 was measured and validated in combination with the Hansen solubility parameter (HSP) method. FTIR and swelling mass changes were also used to explain the reduction of the mechanical properties of NBR/PAE blend in biodiesel. This work presents useful guidelines for the development of thermo-oxidative aging resistance rubber products. [ABSTRACT FROM AUTHOR]