Polymer matrix nanocomposite thermochromic materials

• Main Author: Dhaulathnisha Mohamed Ziaudeen
• Other Authors: Long Yi
• Format: Final Year Project
• Language: English
• Published: 2014
• Subjects: DRNTU::Engineering::Materials::Composite materials
• Online Access: http://hdl.handle.net/10356/60739
• Institution: Nanyang Technological University

Vanadium dioxide (VO2) has a great potential to be used in smart and safe thermochromic windows, which have the ability to reduce energy consumption arising from cooling and heating appliances in buildings. VO2 can respond to temperatures near room temperatures by undergoing metal-insulator transition (MIT). This study will explore an environmentallyfriendly dissolution method of PMMA crystals by using ethyl acetate as the solvent and solution casting the mixture. Furthermore, it will explore the use of thermochromic VO2 in a polymer matrix, poly (methyl methacrylate) (PMMA). It will also study other forms of PMMA-VO2 composites such as cast and laminate structures on both synthesized PMMA sheets and Acrylic. In the VO2-dispersed PMMA nanocomposites, thermochromism of VO2 is proved to exist (20vol% VO2 in PMMA/ethyl acetate, after drying, produced average Tlum=20.7% and 7Tsol=3.12). However, low visible transmittance is observed in pure synthesized PMMA sheet (PMMA crystals dissolved at 700 rpm stirring speed, 70°C stirring temperature for different times depending on amount of PMMA and solvent casting in aluminium container at room temperature) and it is further reduced when thicker PMMA sheet is produced and even when VO2 nanoparticles are added even in small amounts. As alternatives, cast and laminate composite structures were formed using various formulation of PMMA-VO2, which were dried at room temperature. In the laminate structures, PMMA-EA/VO2 interlayer mixture was made in the ratios 1:1 and 10:1. The ratio of 10:1 gave better average Tlum=69.09% but a poor 7Tsol. Silica alumina gel, Si-Al/VO2 interlayers failed because of poor dispersion in between Acrylic pieces. But in between synthesized PMMA, thermochromism was observed as positive 7Tsol was obtained and was increased from 1.42 to 4.88 as VO2 concentration doubled from the ratio Si-Al/ VO2 1:1 to 1:2. However, homogenous dispersion of the nanoparticles and enhancement in Tlum became a challenge as concentration increased. Upon casting PMMA-EA/VO2 in the ratios 1:1 and 10:1, 10:1 gave better results of average Tlum=41% but lower average 7Tsol=0.955. To reduce the problem of low transmittance in cast samples, Si-Al gel was used to mix with VO2 in the ratio 1:1 and was casted onto Acrylic, which gave enhanced average Tlum of 55.92% and higher 7Tsol of 3.78, which seems like a promising candidate for smart and safe thermochromic windows. Future experiments could explore production of bulk PMMA samples using solution casting with high transparency through additives and chemicals that aid in better dispersion of VO2 nanoparticles. Compatibility of dopants with the polymer matrix can also be studied so as to induce the MIT response at temperatures closer to room temperature.