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

Abstract

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.

Mechanisms of the Shape Memory Effect in Polymeric Materials

“…[4,7,9,10,25,37,43,139,148,149], based on the principles of the above discussed working mechanisms, the performance of existing materials can be optimized by means of controlling the processing parameters in programming [113,126,150]. Figure 30 illustrates the influence of the programming temperature on shape fixity ratio (R f ) and shape recovery ratio (R r ).…”

Water-responsive programmable shape memory polymer devices

“…We demonstrate the advantages of utilizing this polymer for novel applications, which are difficult to be realized by other materials. By mixing the polyurethane SMP with, for instance, attapulgite clay [20], we can improve the strength of the polymer and increase the water absorption speed. Hence, fast reaction and high actuation stress can be achieved.…”

Thermal-Mechanical Properties of Polyurethane-Clay Shape Memory Polymer Nanocomposites

“…The attapulgite clay was heat-treated in an furnace (in air) at 850 °C for 2 hours [20,21], and then held in an oven at 100 °C for 12 hours. High resolution transmission electron microscopy (HR-TEM, JEOL 2010F) showed that the treated nano-clay formed a three-dimensional bundled network structure in which the length of single clay fibre varied from sub-micrometer to a few micrometers and the diameter was in the order tens of nanometres (see Figure 1(a)).…”

“…The ring-like scattered diffraction spots reveal the nanocrystalline feature of the treated fibres as shown by the inset electron diffraction pattern in Figure 1(a). The corresponding HR-TEM images in Figure 1 A Haake Rheocord 90 Torque Mixer was used for the mechanical mixing of the PU and attapulgite clay at 200 °C and the SMP nanocomposite sheets (about 3 mm thickness, with nanoclay contents of 10, 20 and 30 wt.%) were prepared by a hot-pressing method [21]. TEM was used to study the microstructure of the nanocomposites.…”

“…At a very shallow indentation depth, the hardness is very high because of the indentation size effect (ISE) [22][23][24]. Several explanations have been used to explain the origin of the ISE, including limitations in experimental conditions (low resolution of the objective lens, work hardening or softening generated during the surface preparation, intrinsic structural factors of the material such as work hardening during indentation, friction at the interface, indentation elastic recovery, and grain size effect) [21][22][23]. In this study, the LSE is probably from work hardening of the polymer and nanocomposites.…”