Remarkable Improvement in the Mechanical Properties of Epoxy Composites Achieved by a Small Amount of Modified Helical Carbon Nanotubes

Abstract

Helical carbon nanotubes (HCNTs) were functionalized to fabricate HCNT/epoxy composites. Acid oxidation and a silane coupling agent, glycidoxypropyltrimethoxysilane (KH560), were used to modify the HCNTs. Remarkably, the flexural strength and the flexural strain were enhanced by 72.0% and 325.0%, respectively, compared to pure epoxy after adding a small amount of the KH560 modified HCNTs (K-HCNTs). Simultaneously, the tensile strength and Young’s modulus of K-HCNTs/epoxy composites were 51.3% and 270.9% higher than those of pure epoxy. It is found that the presence of silane molecules improved the dispersion of HCNTs in epoxy and the interfacial interaction. Moreover, it has been found that the mechanically interlocking effect from the helical shape of HCNTs also contributes to the improved mechanical properties of epoxy composites, compared to their straight multi-walled carbon nanotube (MWCNT) counterparts. This work provides a low-cost and efficient approach to strengthen and toughen epoxy composites.

Mechanical Properties and Characterization of Epoxy Composites Containing Highly Entangled As-Received and Acid Treated Carbon Nanotubes

“…As expected, the D/G ratio increased the most to 1.58 (showing the highest disorder of crystalline structure likely due to the addition of oxygen containing functional groups) for the most aggressive acid treatment (10 M nitric acid at 120 °C for 6 h). As expected, higher temperatures and longer treatment times correlate with increased disordering of the graphitic structure [ 32 , 33 , 34 , 35 , 36 ].…”

“…For O=C–O, the percentage increased from 0.9 to 1.9%. These results show that the acid treatment resulted in the addition of functional groups containing oxygen (i.e., C=O, C–O, and O=C–O) and the decrease in sp 2 character of sample surface [ 32 , 34 , 35 , 36 ].…”

Enhancing the Mechanical and Thermal Properties of Epoxy Resin via Blending with Thermoplastic Polysulfone

“…Epoxy resins (EP) have been widely used in construction, machinery, aerospace and other related fields due to their low cost, excellent bonding performance, outstanding mechanical properties, easy processability, dimensional stability, superior thermal and chemical resistance [1,2,3]. Unfortunately, the high crosslinking density, large internal stress, poor brittleness and poor impact resistance of the epoxy resins after curing has greatly limited their application in some high-tech fields.…”

Flexible Epoxy Resins Formed by Blending with the Diblock Copolymer PEO-b-PCL and Using a Hydrogen-Bonding Benzoxazine as the Curing Agent

“…Two main factors that affect the flexibility of modified epoxy resins are the size distribution and concentration of the additive components. As a result, two major approaches have been developed to enhance the flexibility of epoxy resins: (i) adding a soft segment (e.g., siloxane unit) into the main structure of the epoxy resin [ 6 , 7 ], and (ii) blending with a polymer or nanofiller (e.g., clay [ 8 , 9 ], polyhedral oligomer silsesquioxane [ 10 , 11 , 12 ], carbon nanotubes [ 13 , 14 ], liquid rubber [ 15 ], poly(ethylene oxide) (PEO) [ 16 ], poly(ε-caprolactone) (PCL) [ 17 ]) as a toughness agent. Blending an epoxy resin with a homopolymer or nanofiller in the absence of specific interactions will, however, usually result in macrophase separation through reaction-induced phase separation [ 18 ].…”