Development of SHI 1.0 W 4 K Two-stage Pulse Tube Cryocoolers

Xu, Mingzhi; Gao, J. L.; Seitz, E.; Longsworth, R. C.; Saito, Motokazu; Ikeya, Y.

doi:10.1063/1.2202493

Cited by 9 publications

(9 citation statements)

References 5 publications

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“…As shown in Figure 7, three samples show similar broad diffused diffraction peaks at around 208 and 438, respectively, indicating that the SMPU includes two phases, and is typical of amorphous polymeric materials. 23 Further, the large and broad amorphous peak at around 208 suggests that there is a large amount of amorphous or microcrystals in the SMPU. This may be due to the fact that the crystals are usually microcrystalline structures, and their crystallite sizes are small.…”

Section: Phase Structure Analysismentioning

confidence: 99%

Microstructural and mechanical property evolutions of shape memory polyurethane during a thermodynamic cycle

Shi

Shen

2017

J of Applied Polymer Sci

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To better understand the shape memory behaviors of synthesized shape memory polyurethane (SMPU) sealant with a tailored transition temperature (Tt) for concrete pavement joints, the thermal and dynamic mechanical properties of SMPU were first characterized to determine the shape memory switching temperature of SMPU. Then the microstructural and mechanical property evolutions of SMPU in the original, programmed, and recovered states during a five‐step thermodynamic cycle were discussed, respectively. The results indicate that the tailored Tt of prepared SMPU can be used as the shape memory switching temperature to match its working temperature. Further, the programming causes the phase separation in SMPU, leading to an obvious anisotropy. The SMPU has satisfactory shape memory performance. The orientation of molecular chains in soft segments is confirmed along the stretching direction. The oriented molecular chains can restore to the naturally curled state during the free recovery. Finally, the programming improves the mechanical properties of SMPU. The recovered SMPU shows a slight decrease in mechanical properties because of the partially impaired crystal structures and broken molecular segments during the programming and recovery. It is concluded that the synthesized SMPU with the specially tailored Tt is suitable to use as a sealant of concrete pavement joints. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45703.

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Section: Phase Structure Analysismentioning

confidence: 99%

Microstructural and mechanical property evolutions of shape memory polyurethane during a thermodynamic cycle

Shi

Shen

2017

J of Applied Polymer Sci

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“…Therefore, most recent studies aimed at increasing the recovery forces of shape memory polymer. The strategy includes: post-spinning methods; 38,39 adding carbon nanotubes; 47,48 tailoring the hard segment properties by synthesizing hybrid diol; 49 etc. In our previous study, 50 we have proven that programing process can change the mechanical, dynamic, and shape memory properties of SMPU fibers.…”

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confidence: 99%

Investigation into stress recovery behavior of shape memory polyurethane fiber

Yang

2014

J Polym Sci B Polym Phys

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In this work, the stress recovery behavior of shape memory polyurethane (SMPU) fiber was investigated. The as‐spun SMPU fibers were subjected to various programing‐recovery conditions. It was observed that recovering at 100 °C generated higher recovery stress than recovering at 150 °C. It was also found that, while hot‐drawn programed fiber has higher recovery stress than cold‐drawn programed fiber if recovered at 100 °C, cold‐drawn programed fiber has higher stabilized recovery stress than hot‐drawn programed counterpart when recovered at 150 °C. A morphological model was proposed based on the results from differential scanning calorimetry, Fourier transform infrared spectrometry, and X‐ray diffraction to understand the physics behind the different stress recovery behaviors. It is found that SMPU experiences different phase transitions and phase separations under different programing and stress recovery conditions. It is concluded that the two sequential phase separations taking place at 100 and 150 °C are primarily responsible for the differences in the stress recovery behavior. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 1429–1440

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“…Due to differences between the two techniques, T g values measured by DMA are typically higher than the ones measured by DSC; however, the trends agree with each other. [ 40 ] As illustrated in Figure 3 , all of the samples showed a well-defi ned rubbery plateau ranging from 0 to 100 °C or higher. In addition, the storage modulus of PTMG1K-PU is higher than the other samples in the region of the rubbery plateau.…”

Section: Thermomechanical Analysismentioning

confidence: 86%

Synthesis and Properties of Segmented Polyurethanes with Triptycene Units in the Soft Segment

Chang

Fahs

Hudson

et al. 2015

Macromol. Chem. Phys.

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Segmented polyurethanes based on poly(tetramethylene glycol) soft segments (SS) containing aromatic units are synthesized. Hydroquinone bis(2‐hydroxyethyl) ether and 4,4′‐methylenebis(phenyl isocyanate) are used as the chain extender and the diisocyanate, respectively. Effects of incorporation of hydroquinone (HQ) and triptycene hydroquinone into the soft segments on the morphology and properties of the undeformed segmented polyurethanes are investigated. Differential scanning calorimetry and dynamic mechanical analysis indicate that the incorporation of triptycene units leads to an increased glass transition temperature (Tg) and an elimination of the crystallization of soft segments. The tensile analysis shows there is no strain hardening for the polymer films with triptycene‐containing soft segments. Wide‐angle x‐ray diffraction demonstrates that the absence of strain hardening in triptycene‐containing segmented polyurethane likely arises from the suppressed strain induced crystallization. In contrast, the less bulky HQ units show little effect on either thermally or strain induced crystallization of the soft segments. Morphology studies, including small angle x‐ray scattering on the compression molded films and atomic force microscopy on the solvent cast film, reveal that polyurethanes with HQ and triptycene containing soft segments maintain distinct microphase separated morphology.

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Development of SHI 1.0 W 4 K Two-stage Pulse Tube Cryocoolers

Cited by 9 publications

References 5 publications

Microstructural and mechanical property evolutions of shape memory polyurethane during a thermodynamic cycle

Microstructural and mechanical property evolutions of shape memory polyurethane during a thermodynamic cycle

Investigation into stress recovery behavior of shape memory polyurethane fiber

Synthesis and Properties of Segmented Polyurethanes with Triptycene Units in the Soft Segment

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