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Research Papers

Characterization of Creeping and Shape Memory Effect in Laser Sintered Thermoplastic Polyurethane

[+] Author and Article Information
Shangqin Yuan

Singapore Centre for 3D Printing,
School of Mechanical
and Aerospace Engineering,
Nanyang Technological University,
Singapore 639798, Singapore
e-mail: YUAN0057@e.ntu.edu.sg

Jiaming Bai

Singapore Institute
of Manufacturing Technology,
Singapore 638075, Singapore
e-mail: baijm@SIMTech.edu.sg

Chee Kai Chua

Singapore Centre for 3D Printing,
School of Mechanical and Aerospace
Engineering,
Nanyang Technological University,
Singapore 639798, Singapore
e-mail: mckchua@ntu.edu.sg

Kun Zhou

Singapore Centre for 3D Printing,
School of Mechanical and Aerospace
Engineering,
Nanyang Technological University,
Singapore 639798, Singapore
e-mail: kzhou@ntu.edu.sg

Jun Wei

Singapore Institute
of Manufacturing Technology,
Singapore 638075, Singapore
e-mail: jwei@SIMTech.edu.sg

1Corresponding author.

Contributed by the Computers and Information Division of ASME for publication in the JOURNAL OF COMPUTING AND INFORMATION SCIENCE IN ENGINEERING. Manuscript received April 2, 2016; final manuscript received June 16, 2016; published online November 7, 2016. Assoc. Editor: ChiKit Au.

J. Comput. Inf. Sci. Eng 16(4), 041007 (Nov 07, 2016) (5 pages) Paper No: JCISE-16-1908; doi: 10.1115/1.4034032 History: Received April 02, 2016; Revised June 16, 2016

Thermoplastic polyurethane (TPU) powders were successfully processed in a selective laser sintering (SLS) system. The laser-sintered polyurethane products with viscoelastic behaviors exhibit high flexibility and elongation at break at room temperature. Moreover, the creeping and the thermoresponsive shape-memory effects (SME) were also characterized. The influences of the time-temperature relevant parameters on the shape-fixity and shape-recovery ratios were investigated quantitatively. The creeping and SME were time–temperature dependent phenomena, and the shape recovery mechanism is associated to the microsegments thermal transitions within the polymer matrix.

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Figures

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Fig. 1

DSC diagram of TPU powders from −50 °C to 200 °C at the rate of cooling and heating at 10 °C/min

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Fig. 2

Specimen dimensions (in mm; thickness is 2 mm) in the ASTM D638 standard, type IV

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Fig. 3

Illustration of a typical SME cycle for TPU [21]

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Fig. 4

Powder shape and surface morphology of TPU powders (DESMOSINT X92) by field-emission scanning electron microscopy (FESEM)

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Fig. 5

(a) The powder bed of SLS process at 96 °C and (b) the sintered specimen (Tensile bar in ASTM D638)

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Fig. 6

Strain versus stress curves of sintered TPU specimens upon stretching to different maximum strains of 100%, 200%, and 300%, at the room temperature of 25 °C

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Fig. 7

Typical strain versus stress curves obtained at three different temperatures of 25 °C, 60 °C, and 95 °C, upon stretching to a maximum programming strain of 100%

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Fig. 8

Evaluation of the instant shape fixity ratio (Rfi, black line) and the long-term shape fixity ratio (Rfl, blue line) upon stretching for 0, 30, and 60 min at the maximum programming strains of 200% and 300%, at the room temperature

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Fig. 9

Shape-recovery ratio (Rr) of specimens prestretched to the maximum programming strains of 200% and 300% for 0 and 30 min, under different recovery temperatures of 35 °C, 60 °C, and 95 °C

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Fig. 10

Strain versus stress curves of the sintered TPU over four cycles of stretching–creeping–thermal stimulation (a) upon stretching to 200% strain for 0 min and (b) upon stretching to 200% strain for 30 min, and (c) final fixity ratios of the sintered TPU over four cycles with respect to different holding durations

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