Flexible crosslinking of polyurethane using grafted poly(dimethylsiloxane) with Epichlorohydrin and Bisphenol A end groups and its impact on the mechanical properties and low-temperature flexibility

Poly(dimethylsiloxane) (PDMS) was grafted onto polyurethane (PU), and Epichlorohydrin and Bisphenol A were attached to the free ends of PDMS groups and used to link the grafted PDMS to thereby introduce flexible crosslinks between the PU chains. The flexible crosslinks enhanced the crosslink density and solution viscosity of PU but did not change the melting and crystallization behaviors of the soft segments of PU. In particular, the flexible PDMS crosslinks increased the maximum tensile stress by up to 300% and the maximum tensile strain up to 180%. The shape recovery capability at 10°C and the shape retention capability at −25°C were maintained above 90% with the flexible crosslinking. Grafted PDMS moderately improved the low-temperature flexibility of PU due to its flexibility at low temperature. The flexible crosslinks of grafted PDMS successfully improved the tensile strength, shape recovery, and low-temperature flexibility of the PU.

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The graft polymerization of vinyl benzoate and trans-stilbene onto polyurethane to control its mechanical and shape memory properties

Textile Research Journal ◽

10.1177/0040517516676058 ◽

2016 ◽

Vol 88 (2) ◽

pp. 121-132

Author(s):

Yong-Chan Chung ◽

Jin Cheol Bae ◽

Byoung Chul Chun

Keyword(s):

Tensile Strength ◽

Low Temperature ◽

Shape Memory ◽

Low Temperatures ◽

Shape Recovery ◽

Graft Polymerization ◽

Control Series ◽

Trans Stilbene ◽

Shape Retention ◽

Low Temperature Flexibility

Vinyl benzoate (VB series) and trans-stilbene (SB series) were added onto polyurethane (PU) via graft polymerization, and the spectroscopic, thermal, tensile, shape memory, and low-temperature flexibility properties of the resulting polymers were compared with those of unmodified PU. The melting temperature ( Tm) and glass transition temperature ( Tg) of the soft segments are not significantly different for the VB and SB series compared with unmodified PU. The tensile strengths of the VB and SB series sharply increase with increasing vinyl polymer content, whereas the control series does not exhibit an increase in tensile strength. The VB series exhibits excellent shape recovery at 10℃ compared with unmodified PU, and the shape recovery of the SB series remains above 90% at 45℃. The shape retention values of the VB (−45℃) and SB series (–25℃) are not less than 90%. The selected PUs demonstrate better flexibilities at extremely low temperatures compared with unmodified PU. Therefore, the graft polymerization of vinyl benzoate or trans-stilbene onto PU improves the tensile strength, shape recovery at low temperatures, and low-temperature flexibility of the polymer without decreasing the tensile strain or shape retention.

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Control of the water compatibility and shape recovery of polyurethane using the graft polymerization of poly(ethylene glycol) methyl ether acrylate

Journal of Elastomers & Plastics ◽

10.1177/0095244320933707 ◽

2020 ◽

Vol 52 (5) ◽

pp. 453-468

Author(s):

Yong-Chan Chung ◽

Ha Youn Kim ◽

Jae Won Choi ◽

Byoung Chul Chun

Keyword(s):

Low Temperature ◽

Ethylene Glycol ◽

Methyl Ether ◽

Shape Recovery ◽

Graft Polymerization ◽

Vapor Permeability ◽

Poly Ethylene Glycol ◽

Poly Ethylene ◽

Low Temperature Flexibility ◽

Glycol Methyl Ether

Graft polymerization of poly(ethylene glycol) methyl ether acrylate (PEGA) onto polyurethane (PU) was conducted to improve its water compatibility, tensile mechanical strength, shape memory, and low-temperature flexibility properties, as well as to control its water vapor permeability (WVP). Control PUs containing free poly(PEGA) were also prepared to compare with the poly(PEGA)-grafted PUs. The water compatibility of PU notably improved due to the grafting of poly(PEGA) based on water contact angle results. The soft segment melting temperature and glass transition temperature were not changed with the increase in the PEGA content. The tensile strength of PU sharply increased due to the grafting of poly(PEGA), whereas the free poly(PEGA) in the control PUs did not cause a similar increase. The maximum strain of PU was not affected by the grafting of poly(PEGA). The shape recovery at 0°C significantly increased compared with the unmodified PU. The low-temperature flexibility of PU improved, and the WVP through the PU membrane was reduced by the grafting of poly(PEGA) onto PU.

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Graft polymerization of norbornene onto polyurethane and the characterization of its effect on the shape recovery and low-temperature flexibility of polyurethane

Polymer Bulletin ◽

10.1007/s00289-017-2168-y ◽

2017 ◽

Vol 75 (6) ◽

pp. 2459-2474 ◽

Cited By ~ 2

Author(s):

Yong-Chan Chung ◽

Yong Gap Kim ◽

Jae Won Choi ◽

Byoung Chul Chun

Keyword(s):

Low Temperature ◽

Shape Recovery ◽

Graft Polymerization ◽

Low Temperature Flexibility

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Preparation of hybrid polyurethane–silica composites by a lateral sol-gel process using tetraethyl orthosilicate

Journal of Composite Materials ◽

10.1177/0021998317704279 ◽

2017 ◽

Vol 52 (2) ◽

pp. 159-168 ◽

Cited By ~ 4

Author(s):

Yong-Chan Chung ◽

Kyung Hoon Chung ◽

Jae Won Choi ◽

Byoung Chul Chun

Keyword(s):

Tensile Strength ◽

Shape Recovery ◽

Soft Segment ◽

Sol Gel ◽

Tetraethyl Orthosilicate ◽

Cross Linking ◽

Sol Gel Process ◽

Shape Retention ◽

Low Temperature Flexibility ◽

Hybrid Polyurethane

Hybrid polyurethane–silica composites were prepared using a sol-gel reaction between tetraethyl orthosilicate and triethoxysilyl groups grafted onto polyurethane. The TS series contained the same polyurethane composition but the tetraethyl orthosilicate content varied. Soft segment Tm and Tg values were not affected by the tetraethyl orthosilicate content, while ΔH for soft segment melting and crystallization increased with the tetraethyl orthosilicate content. The tensile strength sharply increased from the cross-linking of the grafted silica at low tetraethyl orthosilicate concentrations but decreased with the increase of tetraethyl orthosilicate content because excess silica inhibited cross-linking. The shape recovery of the TS series improved during cyclic tests, and shape retention slightly decreased as the test cycles repeated. Low temperature flexibility moderately improved with the formation of grafted silica. Therefore, the grafted sol-gel silica formation demonstrated a tensile strength improvement and reproducible shape recovery.

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Designing of new hydrophilic polyurethane using the graft-polymerized poly(acrylic acid) and poly(2-(dimethylamino)ethyl acrylate)

Journal of Polymer Engineering ◽

10.1515/polyeng-2021-0107 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Yong-Chan Chung ◽

Gyo Young Gu ◽

Ji Eun Park ◽

Byoung Chul Chun

Keyword(s):

Acrylic Acid ◽

Shape Recovery ◽

Soft Segment ◽

Strong Acid ◽

Ethyl Acrylate ◽

Maximum Tensile Stress ◽

Polymer Chains ◽

Solution Viscosity ◽

Cross Linking ◽

Poly Acrylic Acid

Abstract Poly(acrylic acid) and poly(2-(dimethylamino)ethyl acrylate) chains were grafted to polyurethane (PU) using the graft-polymerization method in order to enhance the water compatibility of PU. The grafted chains were ionized into cationic or anionic form depending on the addition of strong acid or base. The grafted polymer chains did not affect the melting, crystallization, and glass transition of the soft segment of PU due to the softness of the chain. The cross-link density and solution viscosity increased due to the linking between the grafted chains, but the slight cross-linking did not disturb the solvation of PU. The slight cross-linking notably enhanced the maximum tensile stress and shape recovery capability, and the water compatibility of PU could be notably enhanced by the grafted ionized chains. Overall, the grafting of ionized polymeric chains onto PU could enhance the hydrophilicity of PU surface, tensile strength, and shape recovery capability.

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