Studies of 4,4′-diphenylmethane diisocyanate (MDI)/1,4-butanediol (BDO) based TPUs by in situ and moving-window two-dimensional correlation infrared spectroscopy: Understanding of multiple DSC endotherms from intermolecular interactions and motions level

Synthesis and properties of bio-based thermoplastic poly(ether urethane) for soft actuators

In this study, bio-based thermoplastic polyurethane (TPU) for use in soft actuators is bio-based poly(ether-urethane) made using fermented corn, along with bio-derived compounds such as propane-1,3-diol (PDO) as a chain extender. Bio-based TPUs were obtained through a solvent-free one-shot synthesis method, and the effects of varying the [NCO]/[OH] molar ratio and type of isocyanates on chemical structure, thermal stability, and mechanical properties were investigated. The degree of phase separation (DPS) and state of hard segment (HS) / soft segment (SS) of TPU are important factors affecting the thermal and physical properties of the prepared film. These properties depend on the [NCO]/[OH] molar ratio and the type of isocyanates used for polymerization. The results showed that, when aromatic isocyanate was used, the degree of separation of the HS/SS was improved as the molar ratio increased. The average molecular weight and DPS as well as thermal and mechanical properties of 1-isocyanato-4-[(4-isocyanatophenyl)methyl]benzene (MDI)-based TPU samples are all higher than those of 1,1’-methylenebis(4-isocyanatocyclohexane) (H12MDI)-based TPU samples in spite of the lower HS content. These findings of this study are expected to contribute to the preparation of fused deposition modeling (FDM) 3D printing or 4D printing for shape memory polymer from bio-based TPU filaments for use in soft actuators with a shore hardness range of 59~84A.

Tactile Sensing Using Magnetic Foam

For biomedical applications, smart materials that are used as sensors or actuators have to match some criteria, especially bio-compatibility and softness. Smart polymers are candidates that fulfill these two criteria. A sensitivity to compression is created by adding magnetic particles to a compressible foam polymer. A foam-based composite is fabricated for its small Poisson’s ratio, which enables significant compression, up to 50%. This large compression induces a change in its magnetic properties, which can be detected using coils. By setting the sensing coils as a compact array of 3 × 3, the sensor successfully detected and localized an applied deformation.

Design and Performance of Polyurethane Elastomers Composed with Different Soft Segments

Thermoplastic polyurethane elastomers (TPUs) are widely used in a variety of applications as a result of flexible and superior performance. However, few scholars pay close attention on the design and synthesis of TPUs through the self-determined laboratory process, especially on definite of chemical structures and upon the influence on properties. To investigate the properties of synthesized modifier based on chemical structure, firstly each kind of unknown structure and composition ratio of TPUs was determined by using a new method. Furthermore, the thermal characteristics and mechanical properties of modifiers were exposed by thermal characteristics and mechanics performance tests. The experimental results indicate that TPUs for use as an asphalt modifier can successfully be synthesized with the aid of semi-prepolymer method. The linear backbone structure of TPUs with different hard segment contents were determined by micro test methods. The polyester-based TPUs had thermal behavior better than the polyether-based TPUs; conversely, the low temperature performance of polyether-based TPUs was superior. Most importantly, it was found that the relative molecular mass of TPUs exhibited a weak effect on the mechanical properties, whereas the crystallinity of hard segment showed a significant influence on the properties of TPUs.

Preparation of Thermoplastic Polyurethane (TPU) Perforated Membrane via CO2 Foaming and Its Particle Separation Performance

The way in which a perforated structure is formed has attracted much interest in the porous membrane research community. This novel structure gives materials an excellent antifouling property as well as a low operating pressure and other benefits. Unfortunately, the current membrane fabrication methods usually involve multi-step processes and the use of organic solvents or additives. Our study is the first to offer a way to prepare perforated membrane by using a physical foaming technique with CO2 as the blowing agent. We selected thermoplastic polyurethane (TPU) as the base material because it is a biocompatible elastomer with excellent tensility, high abrasion resistance, and good elastic resilience. Various processing parameters, which included the saturation pressure, the foaming temperature, and the membrane thickness, were applied to adjust the TPU membrane's perforated morphology. We proposed a possible formation mechanism of the perforated membrane. The as-prepared TPU membrane had good mechanical properties with a tensile strength of about 5 MPa and an elongation at break above 100%. Such mechanical properties make this novel membrane usable as a self-standing filter device. In addition, its straight-through channel structure can separate particles and meet different separation requirements.

Least Squares Moving-Window Spectral Analysis

Least squares regression is proposed as a moving-windows method for analysis of a series of spectra acquired as a function of external perturbation. The least squares moving-window (LSMW) method can be considered an extended form of the Savitzky-Golay differentiation for nonuniform perturbation spacing. LSMW is characterized in terms of moving-window size, perturbation spacing type, and intensity noise. Simulation results from LSMW are compared with results from other numerical differentiation methods, such as single-interval differentiation, autocorrelation moving-window, and perturbation correlation moving-window methods. It is demonstrated that this simple LSMW method can be useful for quantitative analysis of nonuniformly spaced spectral data with high frequency noise.

Analytical and Numerical Characterization of Autocorrelation and Perturbation-Correlation Moving-Window Methods

Moving-window (MW) approaches to two-dimensional correlation spectroscopy (2D-COS) make it possible to characterize spectral changes occurring in a narrow range of perturbation variable (e.g., time, temperature, and concentration). Despite the wide range of application, the physical meanings of MW correlation intensities have been only qualitatively associated with the direction and curvature of spectral intensity change with regard to a perturbation variable. Here are full and simplified analytical expressions of autocorrelation moving-window (ACMW) and synchronous and asynchronous perturbation-correlation moving-window ( s-PCMW and as-PCMW) intensities. When the window is set sufficiently narrower than the bandwidth of spectral change, the square root of ACMW intensity and s-PCMW intensity becomes proportional to the first order derivative, and as-PCMW intensity becomes proportional to the negative of the second order derivative. This paper demonstrates that both ACMW and PCMW profiles can be significantly altered by non-uniform perturbation spacing. It is also found that intensity noise can cause ACMW to display a false offset drift. This analytical and numerical characterization of the two MW correlation intensities elucidates their physical meanings and ascertains the analysis conditions for reliable interpretation.

Bio-based polyurethanes with shape memory behavior at body temperature: effect of different chain extenders

The chain extenders are used to adjust the transition temperatures and shape memory properties of bio-based shape memory polyurethanes.

Two-dimensional asynchronous spectrum with auxiliary cross peaks in probing intermolecular interactions

A new approach called “asynchronous spectrum with auxiliary peaks (ASAP)” is proposed for generating a 2D asynchronous spectrum to investigate the intermolecular interaction between two solutes (P and Q) dissolved in the same solution.

Hydrogen bond breaking of TPU upon heating: understanding from the viewpoints of molecular movements and enthalpy

Hydrogen bond breaking of TPU based on 4,4′-methylenediphenyl diisocyanate (MDI)/1,4-butanediol (BDO) upon heating was studied and elucidated from molecular movements and enthalpy.