Influence of pH on Copy-Paper Mechanical Properties Such as the Tensile Strength and Printability

Abstract

Nine series of experiments were conducted on nine different copy paper samples to determine whether there is a correlation between their pH values, their tensile strengths, and printability with statistical tests which confirmed the connection. Ιn this work, all statistical tests were performed via SPSS software. The regression analysis and statistics have confirmed that there was a connection. In more detail the ANOVA with significant value 0.001 led us to reject the null hypothesis that there was no connection between the parameters of the pH value the tensile force MD, the pick picking IGT MD and the ratio MD/ CD tensile strength. In coefficients the predictor variable pick-picking IGT was significant because its p-value was 0.000. The p-value for the ratio MD/CD tensile strength was lower than 0.05, i.e., 0.011 which indicated that it was statistically significant too. The Kruskal-Wallis test confirmed also the connection between the mean values of tensile force MD and pH value and pick-picking IGT and ratio MD/CD tensile strength. From the test of normality, the p=0.019 suggested an evidence of non-normality for the data set of pH and ratio MD/CD tensile strength. Also, the ANOVA with significant value 0.000 led us to reject the null hypothesis that there was no connection between the parameters of the pH, the tensile force CD, the pick picking IGT MD and the ratio MD/CD tensile strength. From the Kruskal-Wallis H test again a p-value of 0.118 confirmed the null hypothesis that the group medians were all equal when the pH value, the CD tensile strength, the pick-picking IGT MD and ratio MD/CD tensile strength were concerned. A boxplot was produced from the descriptive statistics, for the latter parameters i.e., the pH value, the CD tensile strength, the pick picking IGT MD and the ratio MD/CD tensile strength. The dataset had a negative kurtosis i.e., -0.916 and was considered to be a “light-tailed” dataset. From the one-sample t-test we concluded in a level of importance α=0.01 that there was a difference between all the average pH values measured. Finally, the optimal pH values were identified during the analysis of the nine samples of copy paper at the beginning of the year 2021, to be 10.7 when measuring the tensile strength MD, and 10.5 when measuring tensile strength CD, pick picking IGT and the ratio MD/CD tensile strength.