The glass transition temperature of polyurethane shape memory polymer reinforced with treated/non-treated attapulgite (playgorskite) clay in dry andwet conditions

Attapulgite (playgorskite), a kind of nanosized fibrous clay mineral, may provide a simple and cheap alternative to improve the stiffness and actuation stress of shape memory polymers (SMPs). As a first step, in this paper, we investigate the glass transition temperature of a polyurethane SMP reinforced with treated/non-treated attapulgite in wet and dry conditions. In addition to confirming the strong influence of moisture, the results reveal that non-treated clay significantly reduces the glass transition temperature (T_g) of the composites, while the influence of treated clay on T_g is limited. However, for composites mixed with non-treated clay, after drying, the well pre-wetted samples have a much higher T_g than that of the dry ones. A partial detachment mechanism is proposed to explain this interesting phenomenon.