From the results in Fig. 5 it is shown that the 15 lm samples, stored at 23 _C, have a higher increase in Rq than the other samples after week 4 and onward, whereas the other samples follow each other to a great extent.
Further, the roughness values for the samples stored at 23 _C increase to higher values than for the samples stored at 20 _C.
Oscillations in Rq values, mainly observed at 20 _C storage temperature, are due to the presence of protrusions that appear, disappear and reappear over time, which have been reported in recent studies.
Statistical significance of the difference between the means of the samples could be determined (p < 0.05) using analysis of variance (ANOVA).