EFFECT OF WATER-CONTENT ON STICKING DURING

A rotary type tablet machine (Correct 12 HUK-AW, Kikusui, Co., Ltd.) f itted with flat-faced punches 8 mm in diameter was used to measure the scraper pressure (SCR), a kind of shear stress, as a direct means of evaluating sticking, The shear stress between the tablet and lower pun ch surface was determined using a system of SCR detection (strain gaug e type, Okada Seiko Co., Ltd.). SCR increased with increasing compress ion pressure for samples at all water contents tested, The SCR had a t endency to increase up to a water content of 3%, then showed a decreas e at a high water content, This suggests that the adhesive force betwe en particles increases with increasing water content, but for high wat er content, shear stress decreased due to the effect of water as a lub ricant, It is assumed that the sticking ratio increases proportionally with water content until about 3%. Mean surface roughness (R-a) of ta blets due to sticking showed the same relationship between SCR and wat er content, The SCR increased with an increasing value of R-a. Thus, i t was suggested that the adhesive force between particles and the punc h surface plays an important role in sticking.