Macromolecular Research, Vol. 18, No. 6, pp 566-570 (2010) www.springer.com/13233 DOI 10.1007/s13233-010-0611-0

Preparation and Physical Properties of the Biocomposite, Diacetate/ Sized with Poly(vinyl alcohol)

Chang-Kyu Lee, Mi Suk Cho, In Hoi Kim, and Youngkwan Lee* Department of Chemical Engineering, Sungkyunkwan University, Suwon 440-746, Korea Jae Do Nam Department of Polymer Engineering, Sungkyunkwan University, Suwon 440-746, Korea

Received November 2, 2009; Revised February 5, 2010; Accepted February 9, 2010

Abstract: Cellulose diacetate (CDA)/kenaf fiber biocomposites were prepared using a melting process. In order to increase the fiber density and compatibilize the kenaf fiber with CDA, the fiber was sized with poly(vinyl alco- hol)(PVA). The sized kenaf fiber was compounded with the plasticized CDA using a twin screw extruder, and the opti- mal processing conditions were determined. The incorporated kenaf fiber improved the mechanical and thermal properties of CDA. In the case of the composites containing 30 wt% kenaf , the tensile strength and modulus increased almost 2 and 3 fold, which were 85.6 MPa and 4831 MPa, respectively. The PVA treated kenaf fiber showed better adhesion to the CDA matrix. Keywords: cellulose diacetate, kenaf fiber, PVA, sizing.

Introduction CDA, its processability is improved, whereas its unique mechanical properties and thermal stability are deteriorated. Synthetic polymers are widely used in everyday life and In order to increase the physical strength of CDA, the use of are increasingly being used in more diverse areas due to various reinforcing agents were generally accepted.7-9 Natu- their easy processability, permanent stability, low price, and ral fiber is completely biodegraded in the natural environ- antibacterial properties. These advantages of synthetic poly- ment. Unlike or , is mer products, however, in turn cause environmental prob- fully sustainable and does not increase the CO2 concentra- lems when they are discarded or buried in the sea or in tion in the air even during the incineration process. Composites riverside soil. With the increasing interest on environmental containing natural fiber also have a reinforcing effect as problems, the sustainability or biodegradability of resources those containing an inorganic mineral or metal reinforcing is becoming more important.1 Cellulose, a natural polymer agent and are widely applied to car parts, construction/engi- is the main component of the plant cell wall and the most neering, and home appliances.10-14 In this study, plasticized abundant natural polymer on earth. Industrially used cellu- CDA was compounded with kenaf fiber to produce the new losic plastic materials are cellulose derivatives that are made class of high strength biocomposite materials. The aim of by modifying the hydroxyl groups of cellulose in order to this research was to prepare composites in which both the remove the hydrogen bonds. Cellulose derivatives have dif- matrix and fiber are cellulose-based. Kenaf, a natural fiber, ferent characteristics and biodegradabilities according to their is a cellulose-containing plant that is mainly grown in South- degree of substitution.2 The most frequently used derivative east Asia. It grows so fast that as many as three harvests a is cellulose diacetate (CDA). CDA has been used in the fiber year are possible and a large quantity of it can be harvested industry, medical membrane, photographic film, and ciga- at a very low cost. In particular, it is known that a 1 ha kenaf 3,4 rette filter. CDA fiber was generally produced by solution cultivation area can absorb about 30-40 tons of CO2 during spinning method using acetone. Melting process was also one cultivation cycle.15,16 The natural fiber was not easily recently employed with the introduction of the effective mixed due to its low density, and the filling content of the plasticizer.5,6 CDA is decomposed at a higher processing fiber could not be increased. In order to increase the filling temperature than common plastics, due to its high glass content of kenaf in the CDA and to compatibilize the kenaf transition temperature (Tg). Through the plasticization of and CDA, the kenaf was sized with poly(vinyl alcohol)(PVA) solution. PVA is a water soluble polymer with a high tensile 17 *Corresponding Author. E-mail: [email protected] strength, which is expected to interact with the hydrophilic

The Polymer Society of Korea 566