The Type I tensile bars injection molded for each composite were dried in an oven for 24 h at 100 ± 2°C and weighed. Tests were conducted in an incubator at 25 ± 2°C under a photosynthetic photon flux density of 180 pmolm2s-1 using a photoperiod of 12 h light/12 h dark. Tensile bars were placed in distilled water at room tempera­ture for 872 h. At predetermined time intervals the specimens were removed from the distilled water, the surface water was blotted off with paper towels, and their wet masses were determined. Water absorption, measured as weight gain percentage, was computed using the following formula,

Weight gain (%) = (mt — mo)/mo x100 (3)

where mo denotes the oven-dried weight and mt denotes the weight after soak time t. Thickness swelling (TS) was calculated using the following formula,

where TS is the thickness swelling (%) at time t, To is the initial thickness of the specimen, and Tf is the thickness at end of soak time t (872 h).