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

Shape memory nanocomposites of polyurethane (PU)-clay were fabricated by melt mixing of PU and nano-clay. Based on nano-indentation and microhardness tests, the strength of the nanocomposites increased dramatically as a function of clay content, which is attributed to the enhanced nanoclay–polymer interactions. Thermal mechanical experiments demonstrated good mechanical and shape memory effects of the nanocomposites. Full shape memory recovery was displayed by both the pure PU and PU-clay nanocomposites.

Mechanical performance of auxetic polyurethane foam for antivibration glove applications

In this study the static and dynamic characteristics of conventional open cell polyurethane (PU), of auxetic (negative Poisson’s ratio) and of iso-density foams were analysed. The specimens were produced from conventional gray open-cells polyurethane foam with 30-35 pores/inch and 0.0027 g/cm3 density, by means of process which has been previously defined by the authors. Poisson’s ratio measurements were performed under quasi-static conditions using an MTS 858 servohydraulic test machine and a video image acquisition system. For the auxetic foams the results suggested similar behaviour to that previously reported in the literature, with significant increases in stiffness during compressive loading, and a significant dependence of the Poisson’s ratio on the applied strain. Transmissibility tests, performed in accordance with the ISO 13753 procedure for antivibration glove materials, suggested a strong dependence of the transmissibility on the foam manufacturing parameters. Within the frequency range from 10 to 31.5 Hz the transmissibility was found to be greater than 1, while it was less than 1 at all frequencies greater than 31.5 Hz. The transmissibility results were similar to the mean values for 80 resilient materials tested by Koton et. al., but were higher than the five best materials (not all polymeric) identified by the same researchers. In this study it has been suggested that the resilient behaviour of glove isolation materials should also be evaluated in terms of the indentation characteristics. A simple, linear elastic, Finite Element simulation was therefore performed, and the indentation results suggested that auxetic foams offer a significant decrease in compressive stresses with respect to conventional PU foams

Open-celled polyurethane foam

Open-celled polyurethane foam has a density of 8.3 pounds per cubic foot and a compressive strength of 295 to 325 psi. It is useful as a porous spacer in layered insulation and as an insulation material in vacuum tight systems

Efficient design of piezoresitive sensors based on carbon black conductive composites

Flexible and stretchable sensors are widely investigated taking into account their potential for wearable electronics, such as electronic skin, healthcare monitoring, human-machine interfaces, and soft robotics. In this contribution, highly sensitive conductive polymer composites (CPCs) for piezoresistive sensing are summarized, considering a straightforward manufacturing process based on extrusion of thermoplastic polyurethane (TPU) and/or olefin block copolymer (OBC), carbon black (CB), and additionally polyethylene-octene elastomer (POE) grafted with maleic anhydride (POE-g-MA). The design of the formulation variables is successfully performed to enable both low and high strain sensing, as highlighted by both static and dynamic testing

Magnetic properties of materials for MR engineering, micro-MR and beyond

We present the results of a systematic measurement of the magnetic susceptibility of small material samples in a 9.4 T MRI scanner. We measured many of the most widely used materials in MR engineering and MR micro technology, including various polymers, optical and substrate glasses, resins, glues, photoresists, PCB substrates and some fluids. Based on our data, we identify particularly suitable materials with susceptibilities close to water. For polyurethane resins and elastomers, we also show the MR spectra, as they may be a good substitute for silicone elastomers and good casting resins.Comment: 18 pages, 7 tables, 4 figures. Final author manuscript, accepted in JM

Dynamic behavior and damping capacity of auxetic foam pads

A novel set of auxetic (negative Poisson's ratio) open cell polyurethane foam has been developed and tested under dynamic loading conditions to assess the viscoelastic response under white noise random excitation and compressive cycling. Foam pads normalized to standard ISO 13753 have been tested at room temperature and frequency bandwidth 10-500 Hz to assess transmissibility characteristics for possible antivibration glove applications. The results show that the ISO 13753 normalized transmissibility for these foams falls below 0.6 above 100 Hz, with lower peak maximum stresses under indentation compared to conventional open cell solids. These results suggest possible use of the auxetic foam for pads or linens against « white fingers« vibration applications. Further tests have been conducted on cyclic compressive loading up to 3 Hz and loading ratios of 0.95 for loading histories up to 100000 cycles. The damping capacity of the auxetic foams showed and increase by a factor 10 compared to the conventional foams used to manufacture the negative Poisson's ratio ones, and stiffness degradation stabilized after few tens on cycles

On-ground tests of LISA PathFinder thermal diagnostics system

Thermal conditions in the LTP, the LISA Technology Package, are required to be very stable, and in such environment precision temperature measurements are also required for various diagnostics objectives. A sensitive temperature gauging system for the LTP is being developed at IEEC, which includes a set of thermistors and associated electronics. In this paper we discuss the derived requirements applying to the temperature sensing system, and address the problem of how to create in the laboratory a thermally quiet environment, suitable to perform meaningful on-ground tests of the system. The concept is a two layer spherical body, with a central aluminium core for sensor implantation surrounded by a layer of polyurethane. We construct the insulator transfer function, which relates the temperature at the core with the laboratory ambient temperature, and evaluate the losses caused by heat leakage through connecting wires. The results of the analysis indicate that, in spite of the very demanding stability conditions, a sphere of outer diameter of the order one metre is sufficient. We provide experimental evidence confirming the model predictions.Comment: 18 pages, 5 figures, LaTeX2e (compile with pdflatex), sumbitted to CQG. This paper is a significant extension of gr-qc/060109

Experimental research of a new generation of support systems for the transport of mineral raw materials

Within the transportation of materials in mining using the belt conveyor systems, a conveyor belt is particularly the component with the highest wear rate. The development trends in the field of conveyor belt wear, in terms of disruption damage, are mostly focused on the innovation of damping components of buffer beds with impact rubber bars. Impact bars are an essential component of innovative buffer beds suitable for several types of belt conveyors. In mining, these bars are also used in buffer beds of bucket wheel excavator used for the extraction of overlying soils. The most important attribute of this support system is the impact resistance. Therefore, the output of the present paper is the determination of the limit impact dynamic loading based on the quantification of the force effect. The buffer bed eliminates the shortcomings of classic constructions, above all a point contact, and it allows better sealing-off of the whole place of an impact if required. Construction of the buffer bed should provide sufficient stiffness, flexibility, ability to direct conveyor belts at the direction of conveying, absorb the kinetic energy of the transported material, and ensure a surface contact between the material and the conveyor belt by increasing the surface friction drag. This paper deals with the experimental measurement of three kinds of impact rubber bars with different frameworks. Impact characteristics of the bars are significantly affected by the material and the type of metallic framework. The examined impact bars were exposed to the effects of the dynamic impact loading that is of great importance and facilitates the simulation of the belt conveyor system operation. The entire loading process was documented and impact load curves in time were analysed. The depth of penetration and the values of impact load were determined.Web of Science22438537

Synthesis of bio-based thermoplastic polyurethane elastomers containing isosorbide and polycarbonate diol and their biocompatible properties.

A new family of highly elastic polyurethanes (PUs) partially based on renewable isosorbide were prepared by reacting hexamethylene diisocyanate with a various ratios of isosorbide and polycarbonate diol 2000 (PCD) via a one-step bulk condensation polymerization without catalyst. The influence of the isorsorbide/PCD ratio on the properties of the PU was evaluated. The successful synthesis of the PUs was confirmed by Fourier transform-infrared spectroscopy and (1)H nuclear magnetic resonance. The resulting PUs showed high number-average molecular weights ranging from 56,320 to 126,000 g mol(-1) and tunable Tg values from -34 to -38℃. The thermal properties were determined by differential scanning calorimetry and thermogravimetric analysis. The PU films were flexible with breaking strains from 955% to 1795% at from 13.5 to 54.2 MPa tensile stress. All the PUs had 0.9-2.8% weight lost over 4 weeks and continual slow weight loss of 1.1-3.6% was observed within 8 weeks. Although the cells showed a slight lower rate of proliferation than that of the tissue culture polystyrene as a control, the PU films were considered to be cytocompatible and nontoxic. These thermoplastic PUs were soft, flexible and biocompatible polymers, which open up a range of opportunities for soft tissue augmentation and regeneration