Chlorine anions or HCl molecules will be readily trapped by
either Ca(OH)2 or CaO in the aqueous solution, yielding different
Ca salts (such as Ca(OH)Cl, already acknowledged by various other
publications). Furthermore, the nanometallic CaO may adhere as a
coating on the PVC surface, which would also further enhance the
hydrophilicity [59].
3.4. XPS characterization of PVC surface hydrophilicity
Contact angle and SEM-EDS measurements showed that the
nanometallic Ca/CaO treatment made the PVC surface more
hydrophilic. To verify and supplement these findings, X-ray photoelectron
spectroscopy (XPS) analysis was also conducted to
determine the elemental composition of and hydrophilic functional
groups on the untreated and treated PVC surfaces. Table 3 shows
the atomic percentages and elemental ratios of PVC plastics before
and after treatment. Compared with the Cl/C elemental ratio of the
control PVC, that of the treated PVC was decreased considerably.
The Cl/C ratio of the surface PVC before treatment was approxi