Polyurethane dynamic mechanical properties

Extensive dynamic mechanical property studies have been carried out on hydrogen-bonded (81) and nonhydrogen-bonded (60,82) polyurethanes. Several secondary relaxations were found in addition to the major hard- and soft-segment transitions. Molecular mechanisms could... 

Dynamic Mechanical Properties of Poly(tetramethylene ether) Glycol Polyurethanes... 

Dynamic mechanical property (DMP) measurements are used to evaluate the suitability of a polymer for a particular use in sound and vibration damping. Since the dynamic mechanical properties of a polyurethane are known to be affected by polymer morphology (4), it is important to establish the crystallization and melting behavior as well as the glass transition temperature of each polymer. Differential scanning calorimetry (DSC) was used to determine these properties and the data used to interpret the dynamic mechanical property results. 

A more selective approach consists in trying to influence the kinetics of formation of at least one network in this case, the two networks are formed more or less simultaneously, and the resulting morphology and properties can be expected to vary to some extent without changing the overall composition. The same system as previously studied, PUR/PAc, has been utilized in order to prepare a series of in situ simultaneous IPNs (SIM IPNs), by acting essentially on two synthesis parameters the temperature of the reaction medium and the amount of the polyurethane catalyst. Note that the term simultaneous refers to the onset of the reactions and not necessarily to the process. The kinetics of the two reactions are followed by Fourier transform infra-red (FTIR) spectroscopy as described earlier (7,8). In this contribution, the dynamic mechanical properties, especially the loss tangent behavior, have been examined with the aim to correlate the preceding synthesis parameters to the shape and temperature of the transitions of the IPNs. 

For this purpose, the dynamic mechanical properties of a series of 25/75 in situ SIM IPNs have been investigated (Figure 5). With 1% OcSn, the tan 8 vs temperature curve shows a classical shape, as for in situ SEQ IPNs and corroborates the kinetic results two separated transitions, broadened and damped, exist (10). The lower transition corresponding to the polyurethane phase, is shifted... 

Figure 8. Comparison of dynamic mechanical properties for polyurethanes made from symmetric and asymmetric MDI isomers. Key , based on 4,4 -MDI , based on 2,4 -MDI.

A polyurethane (PU)/poly(n-butyl methacrylate) (PBMA) system has been selected for an investigation of the process of phase separation in immiscible polymer mixtures. Within this system, studies are made of the XX, lx, xl, and the 11 forms. In recognition of the incompatibility of PBMA with even the oligomeric soft segment precursor of the PU, no attempt was made to equalize the rates of formation of the component linear and network polymers. Rather, a slow PU formation process is conducted at room temperature in the presence of the PBMA precursors. At suitable times, a relatively rapid photopolymerization of the PBMA precursors is carried out in the medium of the slowly polymerizing PU. The expected result is a series of polymer mixtures essentially identical in component composition and differing experimentally only in the time between the onset of PU formation and the photoinitiation of the acrylic. This report focuses on the dynamic mechanical properties cf these materials and the morphologies seen by electron microscopy. 

Figure 1. Dynamic mechanical properties of linear polyurethane encapsulants at 11 Hz. Formulation nomenclature the first number refers to the weight ratio of polyether (ET) in the soft segment and the remainder is assumed to be the polyester the second number designates the overall weight percent of the diisocyanate.

To examine the effect of various HER chain extenders on the physical, mechanical and dynamic mechanical properties of cast polyurethanes made with MDI-terminated prepolymers. 

Busfield, W.K. (1982) Dynamic mechanical properties of some polycaprolactone-based, crosslinked, crystallizable polyurethanes. J. Macro-mol. Set, Chem., A17 (2), 297-309. 

J. L. Illinger, N. S. Schneider and F. E. Karasz, "Low Temperature Dynamic Mechanical Properties of Polyurethane-Polyether Block Copolymers", Poly. Eng. Sci. 1, 25 (1972). 

Dynamic mechanical properties of T -type high performance shape memory polyurethane... 

Abstract This chapter introduces the moisture-induced shape memory effect (SME) observed in supramolecular shape memory polymers, particularly shape memory polyurethane (SMPU), containing pyridine moieties. The moisture absorption of polyurethane networks containing pyridine moeties (PUPy) is discussed followed by an investigation into the effect of relative humidity (RH), temperature, BINA content and MDI-BDO content. The induence of moisture absorption on both the thermal properties and the dynamic mechanical properties of SMPUs is also described, along with the moisture-induced SME mechanism. 

Effect of moisture absorption on the dynamic mechanical properties of polyurethane... 

Rosthauser J W, Haider K W, Steinlein C and Eisenbach C D (1997) Mechanical and Dynamic Mechanical Properties of Polyurethane and Polyurethane/Polyurea Elastomers Based on 4,4 -Diisocyanatodicyclohexyl Methane, J Appl Polym Sci 64 957-970. 

The dynamic mechanical properties of polyurethanes as a function of the MDI block content are shown in Figure 11. Regardless of the MDI block content, a... 

Thermal and thermomechanical analyses44 are very important for determining die upper and lower usage temperature of polymeric materials as well as showing how they behave between diose temperature extremes. An especially useful thermal technique for polyurethanes is dynamic mechanical analysis (DMA).45 Uiis is used to study dynamic viscoelastic properties and measures die ability to... 

Mechanical properties. See also Dynamic mechanical analysis (DMA) of polyamides, 138 of polyester LCPs, 52 of polyurethanes, 242-244 of semicrystalline aromatic-aliphatic polyesters, 45 Mechanical recycling, 208 Medical applications, for polyurethanes, 207... 

In an NMR analysis of the effects of /-irradiation induced degradation on a specific polyurethane (PU) elastomer system, Maxwell and co-workers [87] used a combination of both H and 13C NMR techniques, and correlated these with mechanical properties derived from dynamic mechanical analysis (DMA). 1H NMR was used to determine spin-echo decay curves for three samples, which consisted of a control and two samples exposed to different levels of /-irradiation in air. These results were deconvoluted into three T2 components that represented T2 values which could be attributed to an interfacial domain between hard and soft segments of the PU, the PU soft segment, and the sol... 

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