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1.
Yong-Chan Chung Duy Khiem Nguyen Jae Won Choi Byoung Chul Chun 《Fibers and Polymers》2010,11(7):952-959
Effect of glucose cross-linking on the shape memory and mechanical properties of polyurethane (PU) block copolymer was investigated.
Glucose was selected due to its large number of free hydroxyl groups, easy availability, miscibility with other reactants,
and cyclic structure. The glycerol cross-linking did not affect the molecular interaction and phase separation of hard and
soft segments in polyurethane structure as judged from IR and DSC analysis. Viscosity of glucose cross-linked PU increased
after cross-linking due to the cross-linked structure. Maximum stress drastically improved with the adoption of glucose as
a cross-linker together with a slight increase in strain at break. Shape recovery also increased with the adoption of glucose
as a cross-linker, and shape recovery was not diminished after four cyclic shape recovery tests. In contrast, shape retention
significantly decreased if glucose was included for two different hard segment contents. Finally, glucose cross-linking was
compared with other cross-linkers used in shape memory polymer and the advantage of glucose cross-linking was discussed. 相似文献
2.
Poly(ethylene terephthalate) (PET) and poly(ethylene glycol) (PEG) copolymers cross-linked with pentaerythritol, a four-way
cross-linker, are prepared to compare their mechanical and shape memory properties with the one cross-linked by glycerol.
Composition of PEG and pentaerythritol is varied to search for the one with the best mechanical and shape memory properties.
The highest shape recovery rate is observed for the copolymer composed of 30 mol% PEG-200 and 2.5 mol% pentaerythritol. Four-way
cross-linking by pentaerythritol significantly improves shape recovery rate and retention of high shape recovery rate after
repeated use compared to the one cross-linked by glycerol, a three-way cross-linker, and difference and advantage of additional
cross-linking point are discussed. 相似文献
3.
Jong Shin Park Yong-Chan Chung Sang Do Lee Jae Whan Cho Byoung Chul Chun 《Fibers and Polymers》2008,9(6):661-666
The shape memory polyurethane (PU) copolymers cross-linked by celite, a porous inorganic material with enormous surface area
and hydroxyl groups on the surface, were prepared to see if the shape memory effect and the mechanical properties were improved.
The PU copolymers with different celite contents were compared and characterized by IR, DSC, DMA, and UTM. The melting temperatures
of PU soft segment were around 20 oC independent of celite content. The shape memory effect and mechanical properties were
dependent on the celite content, and the celite addition into the reaction mixture should be made in the middle of polymerization
to get the best shape memory and mechanical properties. The best mechanical properties were found at 0.2 wt% celite content
and its shape retention rate went up to 98 %. The inclusion of celite as a cross-linker increased both shape memory effect
and mechanical properties. The reasons underlining the improvements by adopting celite as a cross-linker are discussed in
this paper. 相似文献
4.
Effect of the pendant n-butyl group on shape recovery and tensile properties of polyurethane (PU) block copolymer was investigated. The grafted n-butyl group was intended to keep PU chains away and to deter molecular interaction between PU chains by its flexible chains,
and thus improve shape recovery at subzero temperature while maintaining high and reproducible tensile properties and shape
recovery at ambient temperature. The attachment of n-butyl group did not make any change in the molecular interaction and phase separation of hard and soft segments in PU structure
as judged from IR and DSC analysis. Cross-link density and intrinsic viscosity increased with the increase of n-butyl content due to the partial cross-linking by the linking reagent. Shape recovery and shape retention were not diminished
after cyclic shape memory tests. Finally, the effect of n-butyl group on low temperature shape recovery was compared with linear ones and the potential application of this finding
was discussed. 相似文献
5.
Tae Keun Cho Mi Hwa Chong Byoung Chul Chun Hye Ran Kim Yong-Chan Chung 《Fibers and Polymers》2007,8(1):7-12
Polyurethane block copolymers chemically cross-linked by pentaerythritol, a four-way cross-linker, are tested for the shape
memory effect. One of the copolymers shows higher shape recovery than any other shape memory copolymer synthesized by us so
far. The copolymer maintains a surprising 94 % shape recovery after the third cyclic test. The four-way cross-linking by pentaerythritol
and interaction between hard segments are mainly responsible for the very high shape recovery. Tensile mechanical properties
also significantly improve by cross-linking. Glass transition temperature (T
g
) slightly increases with cross-linking content. Other characterization such molecular weight, IR, and X-ray diffraction is
also carried out to understand the arrangement of copolymer chains. 相似文献
6.
Alizarin-series dyes (alizarin, alizarin red S, alizarin yellow GG, or mordant orange) are grafted onto shape memory polyurethane (PU) through an allophanate bonding, and the photoluminescence and the low-temperature flexibility of the resulting PUs are tested. The PU is mainly composed of 4,4′-methylenebis(phenylisocyanate) (MDI), poly (tetramethyleneglycol) (PTMG), and 1,4-butanediol (BD), and the dye is connected, through another MDI, to the carbamate moiety of the PU chain. The PUs with different dye contents are characterized, and their shape recovery and photoluminescence properties are compared. With respect to the tensile mechanical properties, the maximum stress increases up to 50 MPa, and the strain remains above 1000 % even after the dye is grafted onto the PU. The shape recovery is as high as 99 %, and the shape retention improves as the dye content increases. Finally, the photoluminescence of the PUs is demonstrated by the luminescent light emission test, and the dye-grafted PU shows excellent low-temperature flexibility compared with that of linear PU. 相似文献
7.
Yong-Chan Chung Sang Hyeon Kim Jin Cheol Bae Byoung Chul Chun 《Fibers and Polymers》2018,19(6):1157-1165
The bulky and rigid triphenylmethyl group was grafted onto polyurethane (PU) to reduce the molecular attractions between hard segments and to improve the mobility of the PU chain under freezing conditions. The triphenylmethyl-grafted PU exhibited improvement in the cross-link density, solution viscosity, maximum tensile stress, shape recovery at 10 °C, and low temperature flexibility compared with the plain PU. The soft segment melting was not affected by the grafted triphenylmethyl group, whereas the soft segment crystallization disappeared with the increase of the triphenylmethyl group content. The glass transition temperature (Tg) increased with the increase of the triphenylmethyl group content. The rapid increase of the tensile strength and shape recovery at 10 °C resulted from the cross-linking effect, whereas the strain at break and shape retention at -25 °C slightly decreased with the increase of the triphenylmethyl group content. The triphenylmethylgrafted PU displayed an excellent low temperature flexibility even at -50 °C due to the improved mobility of the PU chain compared to ordinary PU. 相似文献
8.
A series of shape memory polyurethane (PU) copolymers synthesized from 1,4-phenyldiisocyanate (PDI), poly(tetramethyleneglycol)
(PTMG), 1,4-butanediol (BD) as a chain extender, and glycerol as a cross-linking agent were tested for the mechanical properties
and the shape memory effect at the temperature 20 °C above melting temperature (T
m), and were compared with other PUs synthesized from 4,4′-methylene-bis-phenyldiisocyanate (MDI), PTMG, and BD. Mechanical
properties and shape memory effect were improved substantially by adopting both PDI and glycerol. Interestingly, enthalpy
of melting and T
m were not affected by the glycerol content. Vibration and shock absorption ability was investigated by measuring both loss
tan δ and storage modulus with dynamic mechanical analyzer (DMA). 相似文献
9.
Flexible linking of shape memory polyurethane (SMPU) was tried with a long polyethyleneglycol (PEG) spacer (PEG-600 or PEG-1000)
longer than the one tested before (PEG-200). The SMPU was composed of MDI, polytetramethyleneglycol (PTMG), 1,4-butanediol
(BD), glycerol, and PEG as a spacer. PEG connected the glycerol hydroxyl group of polyurethane chain via MDI as a connecting
agent. Significant increase in both maximum stress and strain at break was attained simultaneously, because of the flexible
structure of PEG. Especially, it was shown in the stress-strain curve that the PEG-linked SMPU showed similar behavior and
superior tensile mechanical properties to natural rubber. Shape recovery of the PEG-linked SMPU went up to 96 %, and shape
retention remained low compared to linear one. PEG-1000 was better than PEG-600 in enhancing the overall tensile strength
and shape memory of SMPU. 相似文献
10.
Recycled polyols from waste polyurethane (PU) foams were grafted onto PU to improve the properties such as tensile strength, shape recovery, low-temperature flexibility, and water compatibility. The recycled polyol was either purified by column chromatography before grafting or was used directly for grafting. The soft segment melting temperature of PU did not notably increase with the addition of polyol, whereas the glass transition temperature increased with increased polyol content. The tensile strength sharply increased at low polyol content and decreased at high polyol content, while the strain at break did not significantly change with an increase in polyol content. The shape recovery at 10 oC notably improved compared with unmodified PU and remained high after four cyclic tests. Polyol-grafted PU demonstrated better lowtemperature flexibility and reduced the water vapor permeability of PU membranes. Overall, grafting recycled polyol onto PU significantly improved the tensile stress, shape recovery, and low-temperature flexibility of PU. 相似文献
11.
The prepolymer and the final polyurethane (PU) block copolymer were synthesized by reacting 4,4-methylene bis(phenylisocyanate)
with poly(tetramethylene glycol) and the prepolymer with 1,4-butanediol as a chain extender, respectively, to investigate
the relation between phase separation and it’s resulting properties. According to FT-IR data, the phase separation of hard
and soft segments in the prepolymer and the PU block copolymer grew bigger by increasing the hard segment content, and the
PU showed more dominant phase separation than the prepolymer. The heat of fusion due to soft segments decreased in both the
prepolymer and the PU by increasing the hard segment content, whereas the heat of fusion due to hard segments increased in
the PU did not appear in the prepolymers. The breaking stress and modulus of the prepolymer increased by increasing the hard
segment content, and the elongation at break decreased gradually, and the PU showed the highest breaking stress and modulus
at 58 % hard segment content. However, the best shape recovery of the PU was obtained at 47 % hard segment content due to
the existence of proper interaction among the hard segments for shape memory effect. Consequently, the mechanical properties
and shape memory effect of the PU were influenced by the degree of phase separation, depending on the incorporation of chain
extender as well as the hard segment content. 相似文献
12.
The core-sheath nanofibers consisting of polyurethane (PU) core and PU composites sheath with multi-walled carbon nanotubes
(MWNTs) were prepared by electrospinning. At low MWNT concentration, MWNTs appeared highly aligned along the fiber axis with
some curving in nanotubes, whereas in case of high concentration, some aggregation of MWNTs appeared due to difficulty in
full dispersion of nanotubes. In comparison of the single component nanofiber webs, the core-sheath nanofiber webs showed
much better mechanical properties of modulus and breaking stress, including an exceptional elongation-at-break. It indicates
that the CNT-incorporated core-sheath structure is very effective for enhancing the mechanical properties of nanofiber webs.
In addition, the core-sheath nanofibers demonstrated the fast shape recovery, compared with one component fibers of pure shape
memory PU and PU/MWNTs, which provides the possibility of fabricating more sensitive intelligent materials. 相似文献
13.
This study is the first step to investigate usability of shape memory polyurethane (SMPU) fibers for smart garment applications. SMPU fibers were spun by wet spinning process and chemical/mechanical characterization was carried out. SMPU solutions were prepared with two different concentrations (20 % and 25 %) and three different coagulation bath concentrations (0 %, 1 % and 3 %) were used for determining optimum spinning parameters. For investigating influences of spinning process on crystal structure, mechanical, thermal and shape memory performances of fibers, X-ray diffraction (XRD), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), scanning electron microscopy (SEM) and mechanical tests were conducted. DSC and DMA analysis results show that shape memory polyurethane fibers have a glass transition temperature about 35-40 oC which is suitable for body temperature. Moreover, SMPU fibers showed good tensile performance with an average tenacity of 1.38 cN/dtex and elongation at break of 350 %. Thermo mechanical test results showed that, all shape memory fibers have good shape memory effect with recovery and fixity ratios up to 91 % and 71 % respectively. 相似文献
14.
Yong-Chan Chung Jae Won Choi Young Jae Jung Samsook Han Byoung Chul Chun 《Fibers and Polymers》2013,14(12):2069-2076
Polyurethane (PU) copolymer is laterally linked with three kinds of metal ion indicator (calcein, calmagite, or eriochrome black T), with which free metal ion in aqueous solution is intended to be detected by PU color change. Metal ion detection by the indicator-PU fails due to the poor permeation of hydrophilic metal ion into hydrophobic PU layer. Instead, three surfactants with different ionic head groups, aerosol OT (AOT), cetyltrimethylammonium bromide (CTAB), and sodium dodecylsulfate (SDS), are tested for metal ion. Cationic CTAB exhibits an instant PU color change, but anionic AOT and SDS do not respond at all. Reason for the selective detection of cationic surfactant is the complex formation between cationic surfactant and indicator. Molecular interactions between PUs are affected by the laterally linked indicators based on the results by infrared spectra and differential thermal analysis. UV-vis spectra reveal that extra peak arising from the linked indicator appears compared to plain PU. The lateral linking of indicator to PU demonstrates, as well as the selective surfactant detection, a 454 % increase in tensile strength and reproducible shape recovery as high as 99 % compared to plain PU. 相似文献
15.
Linear shape memory polyurethane (SMPU) copolymers synthesized from 4,4′-methylene bis(phenylisocyanate) (MDI), poly(tetramethyleneglycol)
(PTMG), and 1,4-butanediol (BD), and cross-linked SMPU by glycerol were being tested under the severe hydrolysis conditions
for the tensile mechanical properties and the shape memory effect for 6 months. Tensile mechanical properties and shape memory
effect were not substantially decreased after 6 months of storage, and SMPU structure was not affected during the long-term
hydrolysis test as evidenced by IR, DSC, contact angle, and viscosity. Hydrolysis test was important in proving the durability
of SMPU before application of SMPU in aqueous surrounding. 相似文献
16.
Hydrogels, possessing high biocompatibility and adaptability to biological tissue, show great usability in medical applications. In this research, a series of novel cross-linked chitosan quaternary ammonium salt loading with gentamicin sulfate (CTMCSG) hydrogel films with different cross-linking degrees were successfully obtained by the reaction of chitosan quaternary ammonium salt (TMCS) and epichlorohydrin. Fourier transform infrared spectroscopy (FTIR), thermal analysis, and scanning electron microscope (SEM) were used to characterize the chemical structure and surface morphology of CTMCSG hydrogel films. The physicochemical property, gentamicin sulphate release behavior, cytotoxicity, and antibacterial activity of the CTMCSG against Escherichia coli and Staphylococcus aureus were determined. Experimental results demonstrated that CTMCSG hydrogel films exhibited good water stability, thermal stability, drug release capacity, as well as antibacterial property. The inhibition zone of CTMCSG hydrogel films against Escherichia coli and Staphylococcus aureus could be up to about 30 mm. Specifically, the increases in maximum decomposition temperature, mechanical property, water content, swelling degree, and a reduction in water vapor permeability of the hydrogel films were observed as the amount of the cross-linking agent increased. The results indicated that the CTMCSG-4 hydrogel film with an interesting physicochemical property, admirable antibacterial activity, and slight cytotoxicity showed the potential value as excellent antibacterial wound dressing. 相似文献
17.
Segmented polyurethane (PU) polymers are known to have shape memory function, i.e., when they reach certain temperatures,
they deform into the memorized shape from any temporary one. In the present study, PU polymers were spun into fibers using
the conventional extrusion process to investigate the feasibility of producing smart fibers with shape memory function. The
shape memory polymers (SMPs) and their spun fibers were characterized using DSC, DMTA, and tensile test. In particular, the
thermo-mechanical deformation behavior, which enables to evaluate the shape memory performance of the SMPs, was characterized
using DMTA. Then, the linear viscoelastic theory was utilized for mathematical modelling of the thermo-mechanical behavior
of the SMPs. For the shape memory fibers, the large deformation characteristics were also investigated using the thermo-mechanical
test, necessitating the development of nonlinear viscoelastic theory to formulate a constitutive equation and to provide an
effective tool for designing smart textile structure. 相似文献
18.
Polyurethane (PU) films containing different amounts of fly ash particles (FAPs) were prepared by simple solution casting method. The morphological, thermal, and mechanical properties of the composite films were investigated by several characterization methods. Results show that sufficient amounts (up to 40 wt%) of FAPs can be incorporated throughout the film. The presence of FAPs within PU film not only acts as filler to increase the mechanical strength of the film but also increases its volatile organic compounds (VOCs) adsorption capacity. The VOCs adsorption capacity of FAPs/PU composite films were investigated on three different compounds (chloroform, toluene, and benzene). It showed consistent trend in the order of toluene > benzene > chloroform for all the samples. The VOCs adsorption capacity of PU film was found to be increased by two fold when 20 wt% of FA was incorporated through it. The present results suggest the potential use of FAPs as filler materials for PU films with improved VOCs adsorption from outdoor and indoor air. 相似文献
19.
The polyurethane (PU) copolymer was laterally crosslinked with an extra MDI, in which a more rigid polycarbonatediol replaced the conventional poly(tetramethyleneglycol) as a soft segment. What is the impact of the possible molecular interaction between polycarbonate soft segments and lateral crosslinking. The structural change after crosslinking and the impact of new soft segment were followed by infrared spectra, crosslink density, UV-VIS spectra, and relative viscosity. The tensile stress could improve as much as 554 % by selecting the polycarbonate soft segment and the lateral crosslinking. Shape recovery was over 90 % for the entire series and reproducible for four test cycles. The adoption of polycarbonate soft segment and lateral crosslinking significantly could improve the tensile strength and shape recovery compared to PU with polyetherdiol or polyesterdiol soft segment. 相似文献
20.
Nanocomposites of polyurethane (PU) and multi-walled carbon nanotubes (MWNTs) were prepared via in-situ polymerization of
poly(ɛ-caprolactone)diol (PCL)-grafted-MWNTs, 4,4′-methylene bis(phenyl isocyanate), and 1,4-butanediol. The grafting of PCL
onto MWNTs was confirmed by Fourier transform infrared (FT-IR) spectroscopy and transmission electron microscopy (TEM). The
nanocomposites showed more improved mechanical properties compared to conventional nanocomposites with the same MWNT loading.
The thermo-responsive shape recovery as measured in a cyclic tensile test was observed to be approximately 80 % for in-situ
nanocomposites, though it showed a reduced trend as the wt% of MWNTs increased. X-ray diffraction investigation also showed
that the addition of MWNTs into the polyurethane increased the crystallinity. Scanning electron microscopy and TEM measurements
showed better dispersion of MWNTs in the nanocomposites synthesized using in-situ method. Consequently, the presence of PCL-g-MWNTs
made an important contribution to the enhancement of the mechanical and shape memory properties of polyurethane. 相似文献