| Abstract: | SUMMARIES. Wood pulp paper sheets were dipped in polyvinyl alcohol (PVA) of different grades [i.e., degree of hydrolysis and molecular weight; e.g., Vinarol(R) (DV) and Mowiol(R) (4-80, 40-88)] and different chain lengths, as well as at different concentrations (1-5%) for different time intervals (10-60 sec). The retained polymer (grams per square meter of paper sheet) on the paper sheets was highly affected by the chain length, degree of hydrolysis, polymer concentration, and dipping time. The effect of Schoper regular (°SR) of the dipped paper sheets on the retained polymer was studied. Mechanical properties of treated sheets were increased by increasing polymer concentration and dipping time. The effect of thermal treatment of treated sheets at different temperatures (100-12C°C) for half an hour was studied. Also, the effect of thermal treatment at 100°C for different time intervals (0.5-2 h) was clarified. Generally, the mechanical properties of treated paper sheets were highly affected by thermal treatment. It was seen that the mechanical properties were increased by increasing temperature up to 100°C, and then decreased with increasing temperature. Also, the mechanical properties of thermally treated sheets at 100°C increased with increasing heating time to half an hour, and then decreased with increasing time. On the other hand, the percent of improvement of dipped paper sheets of low °SR in polymer solution was higher than of high °SR dipped paper sheets. |
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