Influence of Water and Magnesium Ion on the Optical Properties in Various Plasticized Poly(vinyl butyral) Sheets Michael Tupy ´, Dagmar Mer ˇinska ´, Petr Svoboda, Josef Zvonı´c ˇek Faculty of Technology, Tomas Bata University in Zlin, Zlin 762 72, Czech Republic Received 25 January 2010; accepted 17 March 2010 DOI 10.1002/app.32555 Published online 11 June 2010 in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: The study is focused on influences of opti- cal properties change of poly(vinyl butyral) (PVB) sheets determined for safety glass preparing. Optic measure- ments were evaluated itself and after, the laminated glass was observed. The study deals with a cognizance of cau- sation of the optical properties change in different PVB sheets in dependence on adsorbed water content into the polymer matrix. Results of this work describe the influ- ence of AOH group content on PVB chain and type and amount of additives adjusting adhesion of PVB towards glass. However, the most important discovery of this work is evaluation of critical water content that leads to haze generation. The evaluation of various types of sheets was performed. At the same time the artificial addition of Mg 2þ salts of organic acids (with various polarity of the molecule) was evaluated to assess their influence on haze generation. It was found that haze caused by Mg 2þ salt is possible to eliminate when there is certain water content in PVB. Obtained values and comparisons are very important for PVB sheets industry and for industry dealing with lamination of PVB between glasses. Influence of these factors and comparison of haze generation for various PVB sheets has not been published yet. V C 2010 Wiley Periodicals, Inc. J Appl Polym Sci 118: 2100– 2108, 2010 Key words: laminated glass; poly(vinyl butyral); water absorbability; haze; adhesive agent INTRODUCTION Generally, polyvinyl materials possess excellent acoutooptical properties which allow using them for acoutooptical modulators. 1 Acoutooptical property relates to the use of ultrasound to modulate or change the direction of light in solids. In particular, plasticized poly(vinyl butyral) (PVB) is extensively used as PVB sheet for the production of laminated safety glass. The function of PVB sheet is gluing two or more glass surfaces together, rendering an excel- lent mechanical resistance to the break of the lami- nate. 2–7 The result of the autoclave process of lay- ered materials is adhesive bond between the glass and the PVB. Laminated ‘‘safety’’ glass is required to have the high PVB adhesion to the glass together with excellent optical properties, which are: high light transmission of visible day-light and ‘‘zero haze’’. The main requirement of light transmission (LT) of standard virgin PVB sheet in common lami- nated glass is to be in the range 90.5–90.9% 8 . It was found that the reprocessing degrades PVB and reduces the light transmission, per every reprocess cycle the LT decreases for about 0.2%. Therefore, companies producing PVB sheets specify a minimal LT value to be 89.5% 9 . Even if the LT reduces for only several tenths of % it is extremely important for safety glass production. The PVB sheet with lower LT value could result decreased visibility through the laminated glass, in particular in dark environ- ment. For example, darker strip on the top of the safety glass has LT about 80%. Very important parameter describing laminated glass quality is haze of PVB sheet. Haze is caused by foreign particles, e.g. by poorly homogenized addi- tives, dust, fibers, PVB degradation by-products, or by increased water concentration in the sheet. Most of these foreign particles are caught on the screens in the extruder. However, if the concentration of particles that went through the screens (with dimen- sions smaller than 50–100 lm) is elevated then the human eye can detect them as a haze with critical value being 0.6%. 9,10 Moreover, haze growing can be caused by blending process of PVB materials with different content of AOH group in PVB chain. The specific case of haze generation is increased level of water content (above critical value) in PVB matrix. 11 And this work focuses on finding this Correspondence to: M. Tupy ´ (michael.tupy@email.cz). Contract grant sponsor: Ministry of Education of the Czech Republic; contract grant number: VZ MSM 7088352102. Journal of Applied Polymer Science, Vol. 118, 2100–2108 (2010) V C 2010 Wiley Periodicals, Inc.