STUDY ON IMPROVEMENT OF MECHANICAL PROPERTIES OF MWCNT/EPOXY NANOCOMPOSITE UP TO 5 %wt MWCNT THROUGH INTERFACE BONDING ENHANCEMENT AND AGGLOMERATES SIZE REDUCTION

• Main Author: HANIF DAWAM ABDULLAH (NIM : 33710002), AKBAR
• Format: Dissertations
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/20890
• Institution: Institut Teknologi Bandung

Multi-wall Carbon Nanotubes (MWCNT) have a very high mechanical properties and could potentially serve as reinforcement in polymer composites. However, several studies reported that mechanical properties of MWCNT/ polymer nanocomposites tend lower than conventional composites eg, carbon- fiber/epoxy. For comparison, modulus of elasticity and tensile strength of MWCNT/polymer are 1-2 GPa and less than 100 MPa respectively, whereas modulus of elasticity and tensile strength of carbon-fiber/epoxy are 5-10 GPa and more than 100 MPa. <br /> The efforts to improve mechanical properties of MWCNT/polymer nanocomposites by simply adding fraction of MWCNT are not possible. In MWCNT/epoxy nanocomposite, mechanical properties increased linearly when MWCNT content less than 2%wt, and tend to deviate from rule of mixture (RoM) or decreased when MWCNT content more than 2%wt. The decrease of mechanical properties caused by two main problems, namely dispersion and bonding interface. Low MWCNT dispersion is due to its tendency to form <br /> agglomerates. Agglomerate in matrix is able to form void and reduce area of interface. In addition, the MWCNT difficult to react with epoxy and weaken its interface bond strength, resulted load transfer becoming ineffective. Therefore, to increase mechanical properties of MWCNT/epoxy nanocomposite, improvement the dispersion and interface are necessary. <br /> This study was conducted to assess several methods to increase mechanical properties of MWCNT/epoxy nanocomposite up to 5%wt MWCNT by improving interface bonding and reducing size of agglomerates. These are carried out by four phases of research. The first stage was purification to remove impurities (metal catalyst, amorphous carbon) and ultrasonication to reduce agglomerates. The second stage increases interface bonding through amine functionalization and precuring. The third stage was carried out to overcome manufacturing problems such as Degree of Cure (DoC) and competition reaction by post-curing. The fourth stage was prevention of re-agglomeration by rapid cooling and sorting agglomerates by sieving. <br /> Purification by using acid solution (H2SO4 / HNO3) has succesfully reduced impurities in MWCNT. In addition, the purification process also resulted in an active carboxylic group (-COOH) on the MWCNT walls of which were beneficial <br /> in improving interface bonding. Ultrasonication caused better MWCNT dispersion and reduced agglomerates size, lead to higher interface area which also resulted in increased the interface bonding. Ultrasonication and purification resulted in mechanical properties of MWCNT/epoxy improvement. <br /> Formation of amine group (-NH2) on the MWCNT walls was successfully carried out by functionalization with acrylamide. Precuring cause amine groups react with oxiran (epoxy) produces interface bonding. Therefore, acrylamide functionalization and/or precuring improved mechanical properties of MWCNT/epoxy nanocomposite especially in the 5%wt MWCNT. Post-curing method succeeded in improving mechanical properties of nonprecuring nanocomposite. This was due to longer time span of interface bonding formation. This condition lead to increase the amount of interface bonding and furthermore improved mechanical properties of MWCNT/epoxy nanocomposite. Rapid cooling reduced the effect of re-agglomeration but has not yet managed to improve the mechanical properties of nanocomposite. This was due to the low of agglomerates size reduction. In addition, sieving treatment was successfully reduce diameter of agglomerates significantly. The smaller size of the agglomerates caused extensively MWCNT - epoxy interface which improved the interface bonding and furthermore increased mechanical properties of MWCNT/epoxy nanocomposite.