Carbohydrate Polymers 83 (2011) 303–305 Contents lists available at ScienceDirect Carbohydrate Polymers journal homepage: www.elsevier.com/locate/carbpol Short communication Determination of thermal stability and activation energy of polyvinyl alcohol–cassava starch blends Lee Tin Sin ∗ , W.A.W.A. Rahman, A.R. Rahmat, M. Mokhtar Department of Polymer Engineering, Faculty of Chemical Engineering, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor, Malaysia article info Article history: Received 19 February 2010 Received in revised form 2 July 2010 Accepted 28 July 2010 Available online 6 August 2010 Keywords: Thermogravimetry Activation energy Polyvinyl alcohol Cassava starch abstract The thermal degradation and activation energy of polyvinyl alcohol (PVOH) blends with cassava starch (CSV) were investigated by thermogravimetry method. Neat PVOH, CSV and PVOH–CSV specimens were prepared by solution casting method. Thermogravimetry is able to provide a clear description about the thermal resistance of PVOH–starch by comparing the onset degradation temperatures and activation energies of neat PVOH, CSV and PVOH–CSV blends (20–50 wt.% of PVOH). The results showed that neat CSV has better thermal resistance than neat PVOH. This is probably due to the presence of cyclic hemiacetal structure in starch is sustainable to thermal attacks. PVOH–CSV blend exhibits enhancement in thermal stability at 40–50 wt.% of PVOH. The activation energies of 40 and 50 wt.% of PVOH loading in CSV are 149.64 and 175.49 kJ/mol, which are 5.47% and 23.69% higher than CSV, respectively. In short, blending of cassava starch with PVOH significantly improved the thermal stability of PVOH. © 2010 Elsevier Ltd. All rights reserved. 1. Introduction Polyvinyl alcohol (PVOH)–starch blends have been recognized as potential biodegradable polymeric materials for biomedical and environmental-friendly packaging applications (Chen, Imam, Gordon, & Grèene, 1997; Liu, Feng, & Yi, 1999; Rahmat, Rahman, Lee, & Yussuf, 2009). PVOH–starch hydrogel is compatible with liv- ing cells and able to promote tissues growth (Zhai, Yoshii, Kume, & Hashim, 2002). PVOH–starch packaging materials are consumable by microorganisms when disposed without leaving harmful sub- stances to the natural environment (Chen et al., 1997; Mao, Imam, Gordon, Cinelli, & Chiellini, 2000). PVOH possesses good mechan- ical properties, water soluble and highly crystalline. In contrast, native starch is built up of d-glucose repeating units in amylose and amylopectin structures (Wade, 1999). Native starch does not pos- sess good mechanical strength but is available abundantly at cheap cost, globally. When PVOH and starch are blended together, the presence of hydroxyl groups (–OH) tends to form hydrogen bonding among the molecules and subsequently leads to localized stabil- ity and better system integrity (Sin, Rahman, Rahmat, & Samad, 2010a). In the recent work, Sin, Rahman, Rahmat, and Khan (2010b) postulated that blending of 25–35 wt.% of cassava starch in PVOH blend has physical bonding equivalent to neat PVOH. PVOH–starch blend was also reported compatible with higher physicomechani- cal properties (Mao et al., 2000; Siddaramaiah, Raj, & Somashekar, 2004). ∗ Corresponding author. Tel.: +60 7 5535841; fax: +60 7 5581463. E-mail address: direct.tinsin@gmail.com (L.T. Sin). This paper aims at investigating the thermal degradation kinet- ics of PVOH–cassava starch blends using thermogravimetry (TG) method as disclosed by Ozawa (1965) and Flynn and Wall (1966). This thermal kinetics strategy has been well applied by inter- national standard testing method (British Standard Institutions, 2005). Up to date, very few studies about the thermal stability of PVOH–starch have been conducted. Although, a thorough study of thermal degradation of neat PVOH and starch have been car- ried out separately by Holland and Hay (2001) and Stojanovi ´ c, Katsikas, Popovi ´ c, Javanovi ´ c, and Jeremi ´ c (2005). This is unlikely to predict the direct interaction of PVOH–starch composite sys- tem because every polymer blend system has different thermal stabilities. The interpretations of TG data of polymer blends are important to provide information about the composition of mate- rials, thermal induced reaction kinetics, and radical formations (Conesa, Marcilla, Font, & Caballero, 1996). When TG is coupled with infrared spectroscopy (IR) and mass spectrometry (MS), it will further help to understand the polymer degradation mecha- nism such as main-chain scission, side group scission, elimination and depolymerization through detection of volatile products evo- lution with an accompanying of mass changes (Price, Hourston, & Dumont, 2000). In this study, the reported thermal stability of PVOH–starch is important to provide an understanding about the extent of molecular stability in PVOH–starch as well as providing preliminary information about the stability of PVOH–starch blend. 2. Experimental Fully hydrolyzed PVOH grade BF-17H (viscosity 25–30 cps, hydrolysis 99.4–99.8 mole%, ash <0.7%) manufactured by Chang 0144-8617/$ – see front matter © 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.carbpol.2010.07.049