JOURNAL OF COMPOSITE MATERIALS Article Fabrication and characterization of microwave cured high-density polyethylene/carbon nanotube and polypropylene/carbon nanotube composites Gaurav Arora , Himanshu Pathak and Sunny Zafar Abstract Carbon nanotubes have been used as reinforcements in polymers due to their high elasticity, flexibility, and thermal conductivity. In this study, pellets of high-density polyethylene þ20 wt% carbon nanotube and polypropylene þ20 wt% carbon nanotube were cured using microwave energy. X-ray diffraction, differential scanning calorimetry, thermogravi- metric analysis, uniaxial tensile test, and scanning electron microscopy was used to study morphology, thermal stability, and mechanical performance of the microwave-cured composites. X-ray diffraction analysis confirmed the bonding between the polymer and carbon nanotube as the peaks shifted and intensified. From the thermal study, it was observed that melting point of the composites is affected by microwave curing and the crystallinity of high-density polyethylene/ carbon nanotube and polypropylene/carbon nanotube changed by 57.67% and 47.28%, respectively. Results of the uniaxial tensile test indicated that Young’s modulus of microwave cured high-density polyethylene/carbon nanotube and polypropylene/carbon nanotube composites were improved by 295% and 787.8%, respectively. Scanning electron microscopic fractography shows the stretching of polymer over-lapped on carbon nanotubes in the direction of the applied load. Keywords Microwave curing, carbon nanotube, polymer composites, thermal analysis, tensile strength Introduction Arc discharge method used to produce needle-like tubes was introduced by Iijima, 1 which are known as carbon nanotubes (CNTs). CNTs are the form of carbon having a diameter in nano range and length in micro range. The common types of CNTs are single- and multi-walled CNTs. A graphene layer rolled into a seamless cylinder produces a single-walled carbon nanotube (SWCNT), whereas two or more concentric SWCNTs with different diameters when rolled together forms a multi-walled carbon nanotube (MWCNT). CNTs become potential fillers due to their excellent mechanical characteristics to enhance the strength of polymer composites. Specifically, high stiffness and strength of CNTs motivated towards the develop- ment of nanotube-based polymer composites. 2 High tensile strength, stiffness, aspect ratio, and electrical conductivity make them intriguing for a wide variety of engineering applications. Applications such as insu- lators (electrical and thermal) and high-performance composites (aerospace and automobile) have raised the demand for CNT–polymer nanocomposites. The structure, dispersion technique, alignment of CNTs in polymer matrix, and interaction between CNT and polymer matrix are the significant factors School of Engineering, Composite Design & Manufacturing Lab, Indian Institute of Technology Mandi, India Corresponding author: Gaurav Arora, School of Engineering, Composite Design & Manufacturing Lab, Indian Institute of Technology Mandi, Mandi 175005, Himachal Pradesh, India. Email: aroraiitr@gmail.com Journal of Composite Materials 0(0) 1–14 ! The Author(s) 2019 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/0021998318822705 journals.sagepub.com/home/jcm