Effects of temperature, strain and strain rate on shape memory thermoplastic polyurethane processed by injection molding

Abstract

Shape memory polymers (SMPs) represent a materials class capable of recovering their initial shape, when submitted to deformations, through an external stimulus. This paper focuses on a Shape Memory Thermoplastic Polyurethane (SMPU), characterized by a one-way shape memory effect (SME) activated by temperature. The material was characterized by Differential Scanning Calorimetry (DSC) to find transition temperature; then, it was manufactured by an injection molding machine to perform a campaign of characterization tests. Thermomechanical tests were conducted varying the prescribed strain (up to 25%, 50%, and 80%), imposed at both different strain rates ([Formula: see text], [Formula: see text], and [Formula: see text] s−1), and temperatures (50°C, 60°C, and 70°C); the results were investigated in terms of shape fixity and shape recovery ratios. An excellent memory capability was observed for all the tested conditions; otherwise, the shape recoverability is strongly influenced by all investigated parameters, especially by the strain rate, resulted to be the most effective one. In fact, the shape recovery ratio can increase as much as 20%, when the strain rate is increased from [Formula: see text] to [Formula: see text] s−1. An opposite effect was observed with the variation of prescribed strain and temperature, the increase of which reduces the ability of the material to return to its original shape.

Mechanical and Shape Recovery Characterization of MWCNTs/HNTs-Reinforced Thermal-Responsive Shape-Memory Polymer Nanocomposites

“…The thermomechanical and electroactive properties of styrene-based SMP with conductive elastic fabric were studied by [ 18 ] and the authors observed a stability in the results even after 50 cycles at 40% tensile strain. The influence of temperature, strain and rate on the shape recovery of thermoplastic polyurethane were investigated by [ 19 ] using injection moulding. It was observed that all the above three parameters were significantly affecting the shape recovery.…”

Preparation, shape memory properties and application research of PLA/PCL‐based shape memory polymers doped with Al2O3 and lignin

“…Delgado‐Aguilar et al 31 verified that the mechanical properties could be significantly improved when different proportions of PCL were added into PLA matrix. Coccia 32 et al minutely investigated and analyzed the effects of different temperatures, strain, and strain rate on the properties of the shape memory thermoplastic polyurethane. Although existing studies have improved the performance of PLA and PCL blends by improving the processing technology, there is still a lack of comparative studies on the influence of different performance parameters (such as molecular weight, melt flow rate, etc.)…”

“…In terms of synthesis technology, SMP material blending methods of PLA and PCL can be divided into chemical cross‐linking blending method 25 and physical cross‐linking blending method 26 . Compared with chemical crosslinking method, physical crosslinking method has the advantages of fast processing speed and high efficiency, such as fused deposition modeling, 27–29 hot pressing technology 19 and injection molding 30–32 . At presents, many researchers obtained shape memory polymer by blending multiple thermal‐plastic materials (such as PLA and PCL), and the effects of mass ratio and processing parameters on the mechanical properties and thermodynamic behaviors of blended SMP are analyzed in detail 33 .…”

“…26 Compared with chemical crosslinking method, physical crosslinking method has the advantages of fast processing speed and high efficiency, such as fused deposition modeling, [27][28][29] hot pressing technology 19 and injection molding. [30][31][32] At presents, many researchers obtained shape memory polymer by blending multiple thermal-plastic materials (such as PLA and PCL), and the effects of mass ratio and processing parameters on the mechanical properties and thermodynamic behaviors of blended SMP are analyzed in detail. 33 Delgado-Aguilar et al 31 verified that the mechanical properties could be significantly improved when different proportions of PCL were added into PLA matrix.…”

Poly(Urea-Urethane) Elastomers with Fire-Retardant and Tensile Properties Enhanced by a Built-In Phosphorus Derivative

“…PURs have very diverse properties, depending on the type of raw materials and modifying additives used, as well as on their morphology, i.e., a presence of the solid or foamed structure. Their advantages undoubtedly encompass a relatively inexpensive component manufacturing process and a wide range of processing methods, including the reactive ones, for various PUR forms, such as injection molding, , extrusion, − 3D printing, , foaming, and calendering . Research on PUR focuses mainly on improving existing products’ properties and creating structurally new materials whose specific, distinctive properties would extend their use in everyday life or allow specific applications.…”