[en] The use of polyurethane foams has been under investigation to see if they can be used in DOE decontamination and decommissioning (D&D) operations, specifically to fixate and shield any remaining contamination that is left in any voided structure such as a glovebox. To fix this problem, SRNL attempted to characterize different commercial epoxy foams to evaluate their foam characteristics in different environments, temperature profiles, viscoelastic behavior, shielding capability, and any changes to these characteristics when different weight percent additives were included in the foam matrix. The use of these foams has not been realized yet because of excessive heat generation and flammability concerns during thecuring process.

No abstract available

[en] This paper presents an experimental study on dynamic compressive properties of rigid urethane foams under high deformation velocities realized by means of an impulsive shock device. Two kind of rigid foams are studied within the impulse range: 500 pa. s to 1.200 pa.s. Experimental results are analysed and a comparison between static and dynamic behaviour is made

[en] The immogilzer for control the patient movement during the radiation beam on was made of the polyurethane foam. The time consumption is abut 8 minutes for completely making the immobilizer. In this experimental study, the effects of using the individual immobilizer have shown that the patients have had always a same position with comfortable and high reproducibilities. Furthermore, it has shown the time for patient setup was decreased by using the individual patient immobilizer.

[en] Two approaches to minimize the randomization have been proposed. One is to use crosslinking method and the other is to use high T_g polymers such as polyimides. Polyurethane matrix forms extensive hydrogen bond between urethane linkage and increases rigidity preventing the relaxation of induced dipoles. In this work we prepared new T-type polyurethanes containing dioxynitrostilbenyl group as a NLO-chromophore. We selected 2,5-dioxynitrostilbenyl group as NLO-chromophore because it will have a large dipole moment and is rather easy to synthesize. Furthermore 2,5-dioxynitrostilbenyl group constitutes a novel T-type NLO polyurthanes, in which the NLO chromophores are parts of polymer backbones. These T-type NLO polyurethanes are not shown in the literature. After confirming the structure of the resulting polymers we investigated the properties such as T_g and second harmonic generation (SHG) activity (d₃₃). We now report the results of the initial phase of the work

[en] Four patients with malignant obstruction of the common bile duct had been treated with uncovered Wallstents and suffered from a reobstruction after 2-13 months (mean 5.3 months). Repeat cholangiography revealed severe stenosis of the stent lumen caused by tumor ingrowth through the mesh. A Wallstent with a self-made polyurethane-cover was inserted through the uncovered stent in these patients. The four patients were followed for 3-13 months (mean 6.3 months) until death. There was good drainage with no evidence of recurrent obstruction in all patients. We conclude that a covered Wallstent may extend patency of stented bile ducts, preventing tumor ingrowth in patients with neoplastic obstruction. Further observations are needed.

[en] Gas-permeable polymeric membranes containing carboxyl groups which are suitable for enzyme immobilization were investigated in order to use them as gas electrode membranes in biosensors. Carboxylated polyurethane (CPU) was synthesized via a reaction between 2,2-bis(hydroxymethyl)propionic acid as a chain extender and prepolymers prepared from polycarprolactone (Mn=2,000) and 4,4'-diphenylmethane diisocynate. It was difficult to prepare membranes from the pure CPU because of its high elasticity and cohesion. However, transparent free-standing membranes were easily prepared from the blend solutions of CPU and carboxylated poly(vinyl chloride) (CPVC) in tetrahydrofuran. Both elasticity and cohesion of the CPU/CPVC membranes were decreased with increasing the content of CPVC. DSC experiment suggests that CPU and CPVC may be well mixed. Permeability coefficients for O₂ and CO₂ (P_O2 and P_CO2) in the membranes increased as the proportion of CPU increased. The addition of dioctyl phthalate (DOP), a plasticizer, significantly enhanced the P_O2 and P_CO2 which were 4.4 and 30 Barrer, respectively, in the CPU/CPVC (80/20 wt/wt) membranes containing 20% of DOP at 25 .deg. C and 100 psi. Thus this type of membranes may have a potential for the use as gas electrode membranes in biosensors

[en] During the last few years several research groups have focused on the fabrication of artificial gecko inspired adhesives. For mimicking these structures, different polymers are used as structure material, such as polydimethylsiloxanes (PDMS), polyurethanes (PU), and polypropylene (PP). While these polymers can be structured easily and used for artificial adhesion systems, the effects of repeated adhesion testing have never been investigated closely. In this paper we report on the effect of repeated adhesion measurements on the commercially available poly(dimethylsiloxane) polymer kit Sylgard 184 (Dow Corning). We show that the adhesion force decreases as a function of contact cycles. The rate of change and the final value of adhesion are found to depend on the details of the PDMS synthesis and structuring.

No abstract available

[en] This paper introduces the braided helically wrapped yarns with negative Poisson’s ratio (NPR) exhibiting a stable structure and good practicability to avoid slippage of wrapped component from the core. The geometry and auxetic behavior of the braided helical structure for two different combinations of core materials with similar combination of wrap materials and different braiding angles have been analyzed. Two elastomeric materials i.e. Polyurethane (PU) and Polyester, were used as monofilament cores whereas two stiffer multifilament wrap yarns employed were, ultra-high molecular weight polyethylene (UHMWPE) and polyethylene terephthalate (PET). Multiple braided yarns were investigated to analyze materials’ behavior towards NPR. It was observed that the NPR strongly depended on the inherent properties of the core and wrap materials in addition to the braiding angle. The NPR value was higher for a core with relatively higher elasticity (e.g., PU elastomer compared with polyester). It was also noticed that a lower wrap angle and lower braiding speed exhibited higher NPR. The maximum NPR value using PU core wrapped at a low angle of 9° was - 1.70, when tested at a low strain rate of 0.5%. (author)