Effect of graphene loading on thermomechanical properties of poly(vinyl alcohol)/starch blend Jobin Jose, 1,2 Mamdouh A. Al-Harthi, 1,3 Mariam Al-Ali AlMa’adeed, 4 Jolly Bhadra Dakua, 4 Sadhan K. De 1 1 Department of Chemical Engineering, King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi Arabia 2 Center for Engineering Research (CER), King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi Arabia 3 Center for Research Excellence in Nanotechnology (CENT), King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi Arabia 4 Center for Advanced Materials, Qatar University, Doha, Qatar Correspondence to: M. A. Al-Harthi (E - mail: mamdouh@kfupm.edu.sa) ABSTRACT: Polymer nanocomposites based on poly(vinyl alcohol) (PVA)/starch blend and graphene were prepared by solution mixing and casting. Glycerol was used as a plasticizer and added in the starch dispersion. The uniform dispersion of graphene in water was achieved by using an Ultrasonicator Probe. The composites were characterized by FTIR, tensile properties, X-ray diffraction (XRD), thermal analysis, and FE-SEM studies. FTIR studies indicated probable hydrogen bonding interaction between the oxygen containing groups on graphene surface and the –OH groups in PVA and starch. Mechanical properties results showed that the optimum loading of graphene was 0.5 wt % in the blend. XRD studies indicated uniform dispersion of graphene in PVA/starch matrix upto 0.5 wt % loadings and further increase caused agglomeration. Thermal studies showed that the thermal stability of PVA increased and the crystallinity decreased in the presence of starch and graphene. FE-SEM studies showed that incorporation of graphene increased the ductility of the composites. V C 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41827. KEYWORDS: biopolymers and renewable polymers; blends; composites; mechanical properties; properties and characterization Received 28 June 2014; accepted 1 December 2014 DOI: 10.1002/app.41827 INTRODUCTION The decline in the petroleum resources and an exponential increase in the usage of nonbiodegradable plastic films pose a great threat to the environment. Development of polymer blends and composites, which are amenable to biodegradation, has attracted wide attention in the recent years. Reinforcement of polymer matrices by nanofillers has been widely studied in the last two decades and lately graphene has emerged as a strong competitor for conventional nanofillers such as carbon nanotubes and nanoclays because of its outstanding mechanical and electrical properties, high aspect ratio, low density, and low cost. 1–4 Biodegradable polymer nanocomposites are usually weak in strength and susceptible to water and moisture. Provid- ing adequate mechanical strength and structural integrity for their usage in packaging applications is a great challenge and is the motivation behind undertaking this research work. Poly(vinyl alcohol), abbreviated as PVA, is a bio-degradable polymer whose properties are mainly governed by the degree of hydrolysis, molecular weight, and crystallinity. 5 PVA is widely used in the packaging and textile industries for its excellent properties such as film forming and biodegradability. Even though, PVA is considered to be a biodegradable material, the rate of its biodegradability is less than that of other biopoly- mers such as poly(hydroxyalkanoate) (PHA) or poly(lactic acid) (PLA). 6 Starch is a renewable, biocompatible, and biode- gradable natural polymer, which is widely used to develop envi- ronmental friendly materials and can be easily blended with different polymers. 7,8 However, it lacks dimensional stability, physical strength, moisture resistance, thermal stability, and processability. PVA/starch blend is a widely studied biodegrad- able polymer blend because the rate of biodegradation of PVA can be improved with reduction in overall cost of the mate- rial. 9–11 Furthermore, the processability of this blend can be enhanced by using conventional plasticizers such as glycerol, 12 water, urea, 13 or citric acid 14 and the poor mechanical and ther- mal properties of the PVA/starch blend can be improved by irradiation, 15 chemical crosslinking, 16 physical crosslinking, 17 post curing, 18 modification of starch, 19 and incorporation of nanofillers. 20 V C 2015 Wiley Periodicals, Inc. WWW.MATERIALSVIEWS.COM J. APPL. POLYM. SCI. 2015, DOI: 10.1002/APP.41827 41827 (1 of 8)