The Effect of spray coating and freezing of brown liner paper on its physical and mechanical properties

This research was conducted with the aim of studying the effect of spraying with nano-polyurethane and freezing the treated samples on the physical and mechanical properties of brown liner paper. For this purpose, 128 g.m-2 paper was prepared and its characteristics were evaluated. To coat the surface of the paper, nano-polyurethane is first sprayed using a sprayer in an amount of about 15 grams per square meter for each surface. Then, the coated paper is placed in the environment and the oven (temperature of about 70 οC) to dry, so that the coating material stabilizes on its surface. Then the samples were placed inside the freezer for two and four months, before the tests of the control and coated samples, they were placed in standard environmental conditions (temperature of 20 οC and relative humidity of 65 %). The results showed that spraying increased thickness, decreased water absorption, and increased burst streangth, increased tear streangth. Also, there was no specific change in tensile strength and ring crush test. In sprayed and frozen samples, with the increase in thickness, water absorption and tensile strength decrease, burst streangth and tear streangth compared to non-frozen control samples, an increase was observed. Ring crush test against the was also not significant. The sprayed samples showed very few pores. The thickness and tear streangth in the machine direction of the one-time sprayed brown liner paper increased by 8.96% and 2.3%, respectively, compared to the control sample. water absorption, tensile strength and tear streangth, burst streangth and ring crush test against the ring in the machine direction of one-time sprayed brown liner paper compared to the control sample showed decreased as 19.53, 3.83, 2.4 and 3.14, respectively.