The intensity of this broad
peak increases with increasing concentration of rubber latex, i.e.,
the 5 wt% sheet (Fig. 3b) exhibits the lowest intensity compared
with the 10 wt% and 15 wt%, respectively. The XRD of pristine rubber
sheet has been shown in our previous work elsewhere which
shows only a large broad peak near 2 = 19◦ [26] due to the fact
that the rubber matrix is composed of low atomic number (low Z)
elements. The matrix of 5 wt% sheet has the highest content of TiO2
particles than those of the other sheets, therefore, the highest average
Z-value of matrix resulting in the lowest X-ray scattering and
the lowest intensity peak at 2 = 19◦ as shown in Fig. 3b.