boric acid solution on the solubility of a pvoh film the following experiment was conducted films of 15 mil 0 038 cm wet thickness were separately cast from vinol 205 and vinol 540 pvoh and dried at room temperature strips of 1 u00d7 6 inches about 2 54 u00d7 15 24 cms were then immersed in a 5 boric acid solution at selected temperatures to determine film stability and shelf life at the elevated temperatures that may be experienced under storage conditions the results are reported in table 1 table 1______________________________________80 u00b0 f 26 7 u00b0 c 130 u00b0 f 54 4 u00b0 c 160 u00b0 f 71 1 u00b0 c ______________________________________vinol205 300 days 30 days 16 hoursvinol540 300 days 30 days 3 days______________________________________ the vinol 205 strip stored in 5 boric acid solution at ambient temperature for one year showed no observable change in tensile strength as determined by finger pull vinol 540 is a high viscosity 40 50 cps partially hydrolyzed pvoh 87 89 hydrolyzed marketed by air products and chemicals inc 80 hydrolyzed pvoh is commonly known to have reverse solubility i e insoluble in water at temperatures above 20 u00b0 c but soluble at room temperature for this reason a treated film from such a grade would tend to have an even greater shelf life than the films exemplified above prepared from pvoh which had been hydrolyzed to higher than about 80 to determine flushability characteristics some of the dried paper sheets which were treated with pvoh as in example 1 above were immersed in 5 boric acid solution for two minutes followed by immersion in plain water for two minutes the wet tensile strength was then determined by.