J. Renew. Mater., Vol. 6, No. 7, December 2018 © 2018 Tech Science Press 707 Microwave Synthesis of Inulin Acetate as Potential Bio- Based Additive for Poly(Vinyl Chloride) D. Vassilev 1* , N. Petkova 2 , M. Koleva 1 and P. Denev 2 1 Department “Physics, Chemistry and Ecology”, Technical University of Gabrovo, 4 Hadji Dimitar str., 5300 Gabrovo, Bulgaria 2 Department of Organic Chemistry and Inorganic Chemistry, University of Food Technologies, 26 Maritza blv., 4002 Plovdiv, Bulgaria ABSTRACT: The paper presents the findings of an experimental study on the microwave synthesis (MW) of inulin acetate and its possible application as bio-additive in poly(vinyl chloride) (PVC). The obtained inulin acetate has been identified and characterized by spectroscopic methods. Advantages of the MW compared with the conventional synthesis were defined. In order to evaluate possible application of the product as bio-based additive for polymers, effect of the inulin ester on PVC behavior and characteristics has been investigated by differential scanning calorimetry (DSC) and deformation upon extension. Experimental results show that in concentration range up to 30.0 wt. % the inulin ester influences positively the properties of PVC causing effect similar to plasticizing one. At concentration over 30 wt.% the ester shows more specific behavior, which will be further investigated. Conclusions about potential application of MW synthesized inulin acetate as bio-based additive for PVC have been drawn. KEYWORDS: Inulin esters, microwave-assisted, esterification, poly(vinyl chloride), bio-based additive, tensile properties INTRODUCTION Poly(vinyl chloride) is a rigid-chain polymer that forms the basis of materials with wide application. Its production, processing and application, however, generate problems directly affecting human health and the environment. Some of them are related to the generation of toxic chlorine-containing compounds throughout the PVC lifecycle - from polymer synthesis to waste disposal of PVC products. The use of special additives-plasticizers that facilitate processing and increase its plasticity - poses a serious problem-in recent years almost 90% of the plasticizer products produced worldwide are intended for PVC [1]. The most widely used plasticizers and additives for PVC are low- molecular compounds such as phthalates, trimellitate, citrates, sebacates and adipates. Since they are not chemically bonded to the polymer and have a low molecular weight, plasticizers have a tendency towards migration from the inside to the surface of the product. A number of conventional plasticizers used, such as phthalates have a proven toxicity and harmful effects on human health and the environment [2]. One of the research approaches is related to the reduction of plasti- cizer migration - for example, PVC chemical crosslinking or the blending of PVC with polymeric plasticizers [3]. Another approach is the use of phthalate replacement compounds which combine low toxicity with plasticizing *Corresponding author: dvasilev@tugab.bg DOI: 10.32604/JRM.2018.00015 efficiency close to that of phthalates-for example di-(2- ethylhexyl) terephthalate, diisononyl cyclohexane-1,2- dicarboxylate; Dibenzoates; Acetylated monoglycerides of fully hydrogenated castor oil; isosorbide diesters, etc. [4]. Studies on replacement of classical plasticizers with biodegradable compounds resulting from the processing or modification of natural biodegradable raw materials in accordance with the principles of “green chemistry” have been developing rapidly [5-7]. There has been a significant interest in vegetable oil esters - soybean oil [8], canola oil, castor oil [9], linseed oil or tall oil [10], palm oil or mixtures thereof [11-13] and etc. Over the recent years, the focus is on carbohydrate esters as “green” PVC plasticizers. Renewable oligoesterisosorbide has been synthesized and successfully applied as plasticizer with good plasticizing efficiency for PVC [14]. Carbohydrate esters and polyols esters were successfully applied as plasticizers to cellulose esters, PVC and polylactide [15, 16]. Large potential as “green” PVC plasticizers indicated synthesized by Yin et al. glucose hexanoate esters and sucrooctaacetate [17]. The disadvantages of conventional methods of esterification and environmental problems they pose have been well known. The number of studies conducted resulted in the development of environmentally friendly technologies based on the principles of “green chemistry”. MW as promising “green technology” for modification of polysaccharides was successfully applied also [18-21]. The advantages of microwave-assisted chemistry include high efficiency, improvement of reproducibility of the chemical process, reduction of the unwanted side