The Effect of Microwave Irradiation on Poly(vinyl alcohol) Dissolved in Ethylene Glycol Andres Bernal, 1,2 Ivo Kuritka, 1,2 Vera Kasparkova, 3 Petr Saha 1,2 1 Polymer Centre, Faculty of Technology, Tomas Bata University in Zlin, 762 72 Zlin, Czech Republic 2 Centre of Polymer Systems, University Institute, Tomas Bata University in Zlin, 760 01 Zlin, Czech Republic 3 Department of Fat, Tenside and Cosmetic Technology, Faculty of Technology, Tomas Bata University in Zlin, 762 72 Zlin, Czech Republic Correspondence to: I. Kuritka (E-mail: ivo@kuritka.net) ABSTRACT: Poly(vinyl alcohol) (PVA) dissolved in ethylene glycol is subjected to microwave (MW) irradiation for 1 h to determine possible degradation. Fourier transform infrared spectroscopy results show that MW treatment produces a minor effect on the solu- tions. Ultraviolet–visible spectroscopy suggests that PVA could undergoes loss of hydroxyl groups followed by formation of unsatu- rated conjugated bonds although the extent of degradation is limited, whereas size exclusion chromatography indicates that MW irra- diation do not cause significant changes in PVA molar mass and neither chain cleavage nor crosslinking reactions are observed. Hence, polymer degradation induced by MWs in solution can be considered as negligible for prospective applications. V C 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 000: 000–000, 2012 KEYWORDS: degradation; spectroscopy; microwave irradiation; poly(vinyl alcohol) Received 5 April 2012; accepted 3 June 2012; published online DOI: 10.1002/app.38133 INTRODUCTION Nowadays, material science is interested in production of biode- gradable, biocompatible, and workable polymers with a broad range of properties closely related to their advanced uses as multifunctional materials. One of those materials, widely known is poly(vinyl alcohol) (PVA). This polymer is used in adhesives, cosmetics, textile and pharmaceutical industry, paints, and even as a colloid protector in emulsion polymerization. 1 Numerous advantageous properties of PVA have lead to its broad practical applications due to its chemical resistance, favorable physical properties, and complete biodegradability. 2 Furthermore, it is water soluble and has broad industrial application as a result of its high capability of water absorption. 3 During shelf life, polymers can be degraded by numerous ways including action of chemical substances, mechanical forces, and/ or radiation. IUPAC has defined polymeric degradation as chemi- cal changes in a polymeric material that usually result in undesir- able changes in the in-use properties of the material. 4 In most of the cases, degradation is accompanied by worsening of physico- chemical properties, such as a decrease in molar mass, whereas in some circumstances, degradation also includes changes in chemi- cal structure of the backbone or elimination of polymer side groups. It can also be accompanied by crosslinking. Frequently, degradation results in the loss of, or deterioration in, useful properties of the material. 4 This concept is valid for this study, in which degradation caused by microwave (MW) irradiation is examined. Thermal degradation of PVA on the other hand, has been investigated in more detail than other degradation ways. Thermogravimetry, thermal analysis Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry tech- niques have been used for this purpose. 5 The mechanism of ther- mal degradation of PVA comprises two steps. The first one involves elimination reactions, whereas the second is dominated by chain scission and cyclization. Additionally, highly hydrolyzed PVA shows a better thermal stability than PVA with a low degree of hydrolysis. 6 Degradation of PVA bulk material has been stud- ied by several authors, 1,2,5,6 and it was concluded that the elimi- nation of hydroxyl side groups is present and considerable amounts of isolated and conjugated polyenes in the degradation residue and small amounts of carbonyl groups could appear. Moreover, Ultraviolet–visible (UV–vis) spectroscopy has shown that the unsaturated double bonds produced by elimination do not lead to the formation of noticeable amounts of conjugation. 5 In two related studies, 7,8 solid PVA films were heated by MW irradiation, and it was found that irradiation heating at moder- ate temperature (100–150  C) tends to cause polymer V C 2012 Wiley Periodicals, Inc. WWW.MATERIALSVIEWS.COM WILEYONLINELIBRARY.COM/APP J. APPL. POLYM. SCI. 2012, DOI: 10.1002/APP.38133 1