Multiresponsive Shape Memory Blends and Nanocomposites Based on Starch

Abstract

Smart multiresponsive bionanocomposites with both humidity- and thermally activated shape-memory effects, based on blends of ethylene-vinyl acetate (EVA) and thermoplastic starch (TPS) are designed. Thermo- and humidity-mechanical cyclic experiments are performed in order to demonstrate the humidity- as well as thermally activated shape memory properties of the starch-based materials. In particular, the induced-crystallization is used in order to thermally activate the EVA shape memory response. The shape memory results of both blends and their nanocomposites reflect the excellent ability to both humidity- and thermally activated recover of the initial shape with values higher than 80 and 90%, respectively.

Humidity‐Activated Shape Memory Effects on Thermoplastic Starch/EVA Blends and Their Compatibilized Nanocomposites

“…Moreover, in order to define how many hours are needed to activate both programming and recovery steps in the humidity‐mechanical cycles used for the evaluation of the humidity‐activated shape memory behavior, the dependency of moisture loss as well as of the absorption as a function of time were studied. In our previous work, we performed the recovery step of the humidity‐activated cycles at 37 °C in order to shorten the recovery time of the humidity‐activated cycles . In particular, our objective is to lower the T g below RT by means of only humidity and then accelerate the recovery process thanks to the human body temperature.…”

“…Two different blends with different TPS content, i.e., 40 and 50 wt%, were processed and characterized, as well as their nanocomposites reinforced with 1 wt% of CLNa + . The processing method used was reported elsewhere . Briefly, first, the thermomechanical destructuration of native starch granules with liquid glycerol and distilled water (in the wt ratio of 100:25:20) was performed in a Brabender internal kneader (for 3 min at 110 °C with a rotor speed of 100 rpm) in order to obtain thermoplastic starch.…”

“…In particular, in our previous communication we reported the ability of bionanocomposites based on blends of EVA and TPS reinforced with natural bentonite (CLNa + ) to present dual‐responsive shape memory effects. In fact, they were designed in order to present both thermally activated shape memory effects due to the EVA‐induced crystallization as well as humidity‐activated shape memory behavior due to the presence of TPS demonstrated in preliminary tests.…”

“…The continuous demand for new engineering materials with high performance and different functionalities is leading to the development of new smart multifunctional materials, more particularly the so-called "shape memory" materials, including shape memory polymers (SMPs), metal alloys, hybrids, ceramics, and gels. [1,2] SMPs are polymeric smart materials capable to memorize temporary shapes and recover their original shape upon external stimulation, including temperature, light, humidity, pH, electric or magnetic field, etc. [3] In general, SMPs are strongly affected by the molecular structure of the polymer and they can be programmed in order to exhibit shape memory properties, i.e., combining the effect of two polymer domains/segments or phases.…”

Effect of pine resin derivatives on the structural, thermal, and mechanical properties of Mater‐Bi type bioplastic

“…The test specimens were standard rectangular specimens (80 × 10 × 4 mm 3 ) and standard tensile specimens “1BA” (length ≥ 75 mm, width of 10 mm, and thickness ≥ 2 mm) according to UNE‐EN ISO 527 . Starchy materials are water sensitive and it has been observed that TPS‐based materials performances are influenced by the humidity (i.e., mechanical and thermal properties). Therefore, all samples were conditioned 24 h at 25 ± 1 °C and 50 ± 5% HR previous to be characterized.…”