Study on supercritical CO₂‐assisted modification of aramid pulp and properties of its reinforced EPDM composites

Abstract

Aramid pulp (AP) is often used as a composite reinforcement due to its excellent properties, but poor dispersion and interfacial adhesion restrict its application in composite materials. In this work, tetraethyl orthosilicate (TEOS) was carried on the surface of AP by supercritical CO2 (scCO2) and hydrolyzed to synthesize the nano‐silica, which improves the dispersion of AP in ethylene‐propylene‐diene elastomer (EPDM). The nano‐silica particles were deposited on the AP surface, and th modified AP was evenly dispersed in the EPDM composites based on the SEM results. Moreover, a silane coupling agent (KH‐560) was brought by scCO2 to further modify the nano‐silica on the surface of the AP to improve the interfacial adhesion. Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy results show that after KH‐560 modification, active epoxy groups were introduced on the surface of AP. The tensile strength and tear strength of the KH‐560‐nano‐silica‐AP/EPDM composites were significantly improved, reaching 8.98 and 42.06 MPa, which increased by 26% and 88.10%, respectively, compared with untreated‐AP/EPDM composites. Dynamic mechanical analysis shows that the storage modulus of KH‐560‐nano‐silica‐AP/EPDM composites increased to 2456 MPa compared with the pure EPDM for 1873 MPa, and the loss factor decreased. When the AP was modified in scCO2 with nano‐silica and KH‐560, the composites' oil resistance was also improved.

Preparation and properties of the aramid pulp/nitrile butadiene rubber composites with compatibilization of ionic liquids

“…To solve this problem, a series of methods has been applied to reduce the tangles and improve the compatibility between the AP and the matrix. Especially, for the rubberbased composites, methods such as pre-dispersion [16,17] and pre-treatment by inorganic powder or coupling agents [18][19][20] have been reported. Li et al [19] introduced tetraethyl orthosilicate (TEOS) on the surface of AP by supercritical CO 2 .…”

“…Especially, for the rubberbased composites, methods such as pre-dispersion [16,17] and pre-treatment by inorganic powder or coupling agents [18][19][20] have been reported. Li et al [19] introduced tetraethyl orthosilicate (TEOS) on the surface of AP by supercritical CO 2 . The TEOS was hydrolysed to synthesize the nano-silica to improve the AP dispersion in the ethylenepropylene-diene elastomer (EPDM), and silane coupling agent was applied to further enhance the interfacial bonding strength.…”

Aramid fiber coated with aramid nanofiber coating to improve its interfacial properties with polycarbonate

“…The smooth, inert surface of aramid fiber also prevents it from attaching well to resin. [1,4,21] Many surface modifications were reported, including chemical etching, [4,[22][23][24][25] acid-base hydrolysis, [26,27] plasma treatment, [28][29][30] and ultrasonic treatment, [31,32] rougher surfaces and functional groups such as hydroxyl and carboxylic acids were made, which are useful for improving the bonding strength. Recently the method for covalent bonding between fibers and substrates by grafting specific molecular segments requires harsh conditions such as high temperature, highly reactive catalyst and strong acid-base environment.…”