Fully hydrolyzed PVA, where all the acetate groups have been hydrolyzed, is more moisture resistant than partially hydrolyzed PVA due to the lower probability of further hydrolysis of the acetate groups. Fully hydrolyzed PVA has higher surface tension than partially hydrolyzed PVA, however, fully hydrolyzed PVA modified with ethylene groups in the polymer structure has lower surface tension (see the section on foaming for the effect of surface tension on the behavior of the EPI). According to Schilling [11] partially hydrolyzed PVA may offer an advantage in that fewer hydroxyl groups are available for reaction with isocyanate [11] to enhance the cross-linking reactions betweenthe latex polymers (cf. previous section). However, a high degree of hydrolysis is reported to be preferable to obtain a more water resistant glueline [4, 11].