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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.

Melamine was grafted to a polyurethane (PU) frame and utilized for cross-linking PU via amino groups. The degree of crosslinking and the solution viscosity increased notably after grafting melamine due to the formation of crosslinks. The thermal transition of the soft segment was not significantly affected, but the glass transition was observed at a slightly higher temperature in case of the grafted melamine. Melamine-mediated crosslinking increased not only the breaking tensile stress but also the shape recovery performance of PU. In addition, crosslinked PU was more flexible at low temperature than unmodified PU. Overall, melamine-mediated crosslinking improved the tensile resistance to stress, the recovery tendency to the initial shape, and the flexibility with minor changes in the thermal transition, tensile strain, and shape retention at a low temperature.

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.

2,4,6-Tris(dimethylaminomethyl) phenol (TDMP) was used as a grafted functional group to modify the hydrophilicity of polyurethane (PU) and to enhance the mechanical properties and low-temperature flexibility of PU. The grafted TDMP after conversion to the ionic form notably enhanced the hydrophilicity of PU, as confirmed by the water contact angle, water swelling, and water vapor permeability results. The light crosslinking that occurred during the grafting step increased the crosslink density and solution viscosity but did not disturb the solvation of PU. The melting of the soft segment was not affected by the grafted TDMP, but the crystallization of the soft segment was significantly reduced. The breaking tensile stress and shape recovery capability were notably enhanced, but the breaking tensile strain and shape retention capability were not impaired. In addition, the grafted TDMP notably improved the flexibility of PU at very low temperature compared with that of plain PU and control series PU. Overall, it is worth grafting TDMP onto PU considering the simple preparation method, the novelty of the modification mechanism, the notable enhancement in hydrophilicity, and the potential applications in fiber and biomedical fields.

Ionic cross-linking of polyurethane (PU) was performed using grafted glutaric acid (GA) or dimethylamino propanol (DAP) to enhance the mechanical properties and control the degree of interaction using acid or base. The effect of ionic cross-linking on the water compatibility, thermal phase transition of soft segments, tensile mechanical strength, and shape memory properties were determined by comparison with ordinary PU. The water compatibility of PU could be improved by grafted acidic or basic functional groups. The breaking tensile stress and shape recovery capability increased significantly relative to ordinary PU due to ionic cross-linking but notably decreased upon the addition of acid or base due to the disruption of ionic cross-linking. It was demonstrated that the water compatibility and mechanical properties of PU could be controlled using ionic cross-linking and the disruption of ionic cross-linking by adding acid or base.

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.

Epoxy polymers composed of bisphenol A (BPA) and epichlorohydrin (ECH) were grafted onto polyurethane (PU) using the graft-polymerization method to prepare the epoxy PU hybrid polymer. The main series contained the epoxy polymer grafted onto PU; however, the epoxy polymer was not bound to PU in the control series. The breaking tensile stress steeply increased at low BPA and ECH contents and then decreased as more BPA and ECH were included in the main series, whereas the control series did not display an incline in the breaking tensile stress irrespective of the BPA and ECH contents. The percent shape recovery also steeply increased after the grafting of epoxy polymer in the main series but increased at a slower rate in the control series. The flexibility of the main series at a freezing temperature was not enhanced compared with the plain PU because the grafted epoxy polymers did not effectively disrupt the molecular interaction between PUs. Therefore, the grafting of epoxy polymers noticeably enhanced the breaking tensile strength and percent shape recovery of PU.

The antifungal agent carbendazim and the water-compatible functional group 2,4,6-tris(dimethylaminomethyl)phenol (TDMP) were jointly grafted to polyurethane (PU) to develop a water-compatible antifungal PU. The water compatibility of the PU surface improved strikingly after the protonation of TDMP, as confirmed by water contact angle tests. The combined grafting of carbendazim and TDMP affected the melting and glass transition of soft segments and sharply increased the tensile stress and shape recovery capability. Carbendazim was selected as a grafted antifungal functional group due to its wide effective range of antifungal activity and its large production volume. PUs with grafted carbendazim and TDMP completely suppressed the growth of a mixture of fungi, unlike ordinary PU. Therefore, the joint grafting of both carbendazim and TDMP led to improved water compatibility, breaking tensile stress, shape recovery capability, and antifungal activity.

The poly(ethylene glycol) phenyl ether acrylate (PEPA) monomers are graft-polymerized onto polyurethane (PU), and its impacts on water compatibility, chain packing, tensile stress, and shape recovery capability are evaluated. The grafted poly(PEPA)s slightly increase the degree of cross-linking due to the linking between themselves. The water compatibility (water contact angle, water swelling, and water vapor permeation) are affected slightly by the grafted poly(PEPA). The grafted poly(PEPA) does not notably influence the melting of soft segments, but the crystallization of soft segments is reduced significantly. The grafted poly(PEPA) does not significantly affect the glass transition of soft segments. The grafted poly(PEPA) notably increases the breaking tensile stress with the increase in PEPA content, but the breaking tensile strain decreases slowly with increasing PEPA content. The grafted poly(PEPA) rapidly improves the shape recovery capability of PU and slowly decreases the shape retention capability with the increase in PEPA content. Therefore, the grafted poly(PEPA) slightly modifies the water compatibility but notably enhances the breaking tensile stress and shape recovery capability of PU.

Perpendicular cardo structural units were inserted into a polyurethane (PU) framework from the pH indicator (phenolphthalein (PP), phenol red (PR), or bromocresol green (BG)) sharing a triphenylmethyl group. The thermal transitions, mechanical properties, pH-sensitive color change, and low temperature flexibility of the PU modified with the cardo structural units were compared with those of the ordinary PU. Slight cross-linking between PU chains was performed because the insertion of the indicator moieties deteriorated the mechanical properties. The breaking tensile stress and shape recovery capability at 0 °C of the BG-PU series surpassed those of the PP-PU and PR-PU series. The inserted pH indicator moieties did not show the color change under different pH conditions because the isomerization under basic conditions was blocked. Among the three series of PUs, the BG-PU demonstrated the best low temperature flexibility compared with that of the PP-PU and PR-PU due to the functional groups on the phenyl rings of BG. Insertion of a cardo structural unit from the pH indicator reduced the molecular interaction between PU chains.

A hydrophobic polyurethane (PU) was altered to obtain a hydrophilic characteristic using the graft polymerization of 2-(dimethylamino)ethyl methylmethacrylate (DAMA) onto the PU surface and the subsequent ionization of the dimethylamino group on poly(DAMA). The grafted poly(DAMA) chain influenced numerous properties, such as the cross-link density, thermal transitions of soft segments, and tensile and shape memory characteristics. The grafting of poly(DAMA) noticeably enhanced the breaking tensile stress and shape recovery capability through the cross-linking between the grafted poly(DAMA)s, but the breaking tensile strain and the shape retention did not noticeably decline after the grafting of poly(DAMA). Additionally, the poly(DAMA)-grafted PU exhibited a significant enhancement in its low temperature flexibility and antifungal effectiveness against a mixture of fungi.

Phthalic acid (PA) was grafted onto polyurethane (PU) in the PA series due to its rigid aromatic structure and carboxyl groups, but PA was simply blended with PU in the control CPA series. The cros...

The surface of polyurethane (PU) was modified by the graft polymerization of N,N-dimethylaminoethyl methacrylate (DAMA) and acrylic acid (AA) to enhance its water compatibility. Portions of poly(DAMA) and poly(AA) could be ionized by mutual acid–base neutralization and could notably improve the surface hydrophilicity of PU. The water contact angle, water absorption, and water vapor permeation test results jointly demonstrate the increase in water compatibility resulting from the inclusion of poly(DAMA) and poly(AA) in PU. The melting and glass transition temperatures of PU were not significantly influenced by the grafting of poly(DAMA) and poly(AA) onto PU. Small portions of the grafted poly(DAMA) and poly(AA) were involved in the cross-linking of PU, which sharply increased the shape recovery and the breaking tensile stress while maintaining high shape retention and breaking tensile strain.

Poly(N-isopropylacrylamide) (poly(NIPAM)) was grafted onto polyurethane (PU) using a graft-polymerization method to develop a thermo-responsive PU and to investigate the impact on cross-link density, solution viscosity, soft segment thermal transitions, tensile properties, shape memory effect, and water vapor permeation through PU membrane. The soft segment crystallization peak sharply decreased with the increase in NIPAM content, whereas the glass transition temperature (Tg) slightly increased with the increase of NIPAM content. The breaking tensile stress rapidly increased with the increase in NIPAM content due to the cross-linking effect between the grafted poly(NIPAM) chains, whereas the strain at break did not significantly decreased as the NIPAM content increased. The shape recovery at 10°C rapidly increased from 46.9% for plain PU to above 90% after the grafting of poly(NIPAM) onto PU, and the shape retention at −25°C slightly decreased with the increase in NIPAM content. Finally, the graft...

Grafting of niclosamide or salicylanilide onto polyurethane (PU) was executed to develop antifungal effectiveness and barnacle repelling capability in seawater compared with underivatized PU. The PU surface was simultaneously modified to improve the surface hydrophilicity by inserting dimethylolpropionic acid into PU frame or by grafting recycled polyols onto PU. Surface modifications of PU significantly affected its properties, such as cross-link density, tensile and shape memory properties, and flexibility under freezing conditions relative to the unmodified PU. The modification of PU surface also notably influenced the glass transition and the melting and crystallization related to soft segments. The breaking tensile stress and the shape recovery were enhanced significantly after the grafting of polyol due to chemical cross-linking, whereas the breaking tensile strain was not reduced. Some PU samples demonstrated complete antifungal effectiveness against a mixture of fungi, and barnacle growth on PU films was limited in the specifically modified PUs.

The aliphatic dicarboxylic acid, glutaric acid or dodecanedioic acid, were used for the grafting onto polyurethane (PU) or cross-linking of PUs to gauge its impact on the hydrophilicity, tensile stress, and shape recovery properties of PU. The cross-link density and solution viscosity gradually increased, but the maximum tensile stress and shape recovery sharply increased with the increase of diacid content due to the chemical linking using the grafted diacid. The soft segment melting and glass transition were not substantially affected by the grafting of diacid. The water swelling of the diacid-grafted PUs gradually improved with time. The low temperature flexibility of PU slightly improved by the grafted glutaric acid compared with the control series PU. Therefore, the grafted dicarboxylic acid could enhance the hydrophilicity, maximum tensile stress, shape recovery, and low temperature flexibility of PU.

Reduced graphene oxide (RGO) or graphite is functionalized with hydroxyl groups for linking to the sides of polyurethane (PU) chains. Blended PU with RGO or graphite is prepared as a control for comparison. The PU composites are compared with respect to their spectroscopic, thermal, mechanical, shape memory, and sheet resistance properties. Scanning electron microscopy images demonstrate the good distribution of functionalized graphene oxide (FGO) or functionalized graphite (FG) particles on the inner surface of the PU. The linking of FGO or FG onto PU does not significantly affect the thermal behavior or shape memory properties but sharply improves the tensile strength of the PU composites without a noticeable decrease in tensile strain. The shape recovery of PU composites remains at approximately 90%, regardless of the FGO or FG content. The FG-linked PU composites exhibit a sharp decrease in sheet resistance as the FG content increases, whereas the sheet resistance of the FGO-linked PU composites does not decrease with increasing FGO content. The control PU composites with blended RGO or graphite show significant reductions in their sheet resistance. Considering the ease of functionalization of the graphite surface and the significant improvement in tensile strength, linking FG onto PU is advantageous for the development of PU composites with low sheet resistance.

Bis(2-hydroxyethyl) terephthalate (BHETPA) was grafted onto polyurethane (PU) to investigate the effects of BHETPA, which contains a rigid aromatic group and flexible hydroxyethyl groups, on the ph...

Phenolphthalein (PP series) or 4-tritylaniline (TA series) was used for grafting onto polyurethane (PU), and the effects of two grafted groups on the soft segment glass transition, tensile strength, recovery to original shape, and flexibility at freezing temperature were investigated. The soft segment melting of PP series and TA series was not significantly affected with increases in phenolphthalein or tritylaniline content. The soft segment glass transition temperature (T g ) of PP series clearly increased as the PP content increased, whereas TA series exhibited a little increase in T g with increases of TA. Solution viscosity, degree of cross-linking, shape recovery at 10 °C, and tensile strength of PP series clearly increased with increases in PP because of cross-linking in the grafted phenolphthalein, whereas TA series did not demonstrate the same degree of enhancement with increases in TA. In contrast to plain PU and TA series, PP series displayed outstanding flexibility below 0 °C. Therefore, compared to plain PU, the grafting of phenolphthalein clearly enhanced the tensile strength, flexibility under freezing, and recovery to original shape of the polymer.

Dimethylphenyl groups were grafted onto polyurethane (PU) to investigate its disrupting effects on the intermolecular attractions, but the dimethylphenyl-grafted PU required fortification by cross-linking with 4,4'- methylenebis(phenyl isocyanate) (MDI) to compensate for the decrease in the PU’s physical properties. The cross-link density, solution viscosity, maximum tensile stress, and shape recovery initially increased due to the chemical cross-linking with MDI but decreased with the increase in dimethylphenyl groups due to its disrupting effects: maximum tensile stress and shape recovery increased up to 57.1 MPa and 98.5 %, respectively, but finally decreased to 17.2 MPa and 66.2 % with the increase of dimethylphenyl group content. Low temperature flexibility was not observed due to the poor shape recovery with the increase in dimethylphenyl groups. Therefore, the grafted dimethylphenyl groups disrupted the intermolecular attractions between PUs and resulted in a significant reduction in the tensile stress and shape recovery properties of PU compared to plain PU.

The graft polymerization of tert-butyl acrylate (TBA) onto polyurethane (PU) was conducted to prepare a series of samples that was compared to a control series comprising a physical mixture of poly(TBA) and PU. Maximum tensile stress sharply increased because of chemical cross-linking via poly(TBA), whereas tensile breaking strain slightly diminished by the grafted poly(TBA). Percent shape recovery at 10°C rapidly increased by the additional grafting of poly(TBA), whereas control series decreased with increases in TBA monomer content. Chemical cross-linking from the grafted poly(TBA) was responsible for the enhancement of shape recovery. Low-temperature flexibility tests from −35°C demonstrated that a proper composition of grafted poly(TBA) could enhance the flexibility of PU below 0°C. Overall, the grafted poly(TBA) greatly stepped up the maximum tensile stress, recovery capability to original form, and flexibility of PU at very low temperature.

Graft polymerization of norbornene monomers onto polyurethane (PU) was tested to reduce the intermolecular attractions between PUs using the rigid bicyclic ring structure of norbornene, to control the soft segment thermal properties, and to enhance the tensile, shape memory, and low-temperature flexibility properties compared with those of unmodified PU. The soft segment crystallization temperature (T c) sharply decreased with the increase in norbornene, whereas the soft segment melting temperature (T m) was not significantly changed by the norbornene content. However, the glass transition temperature (T g) increased with the incorporation of norbornene. The tensile strength sharply increased with the increase in norbornene due to the chemical cross-linking between the grafted poly(norbornene), whereas a significant decrease in the maximum strain was not observed. The shape recovery at 10 °C sharply increased from 47% to approximately 90% after the graft polymerization of norbornene, and the shape retention at −25 °C decreased with the increase in norbornene. Finally, the graft polymerization of norbornene onto PU demonstrated enhanced low-temperature flexibility due to the reduced restrictions of rotational and translational mobility.

We have researched the functionalized polyurethane (PU) that can exhibit a wide range of interesting performances unattainable from the ordinary PU. We found that the grafted Phenol Red sharply increased the tensile mechanical strength due to the chemical crosslinking by Phenol Red. In addition, shape recovery at 0°C improved from 24% up to 84%, and the shape retention at −30°C decreased as the Phenol Red content increased. The Phenol Red-grafted PU demonstrated flexibility, even at −50°C, and a full recovery at −5°C. Therefore, Phenol Red-grafted PU exhibited a sharp improvement in tensile stress, shape recovery, and low-temperature flexibility, which was not attainable in ordinary PU. The Phenol Red-grafted PU performed better than other functionalized PU we have developed.

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.

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.

A pH indicator (Bromocresol Green, Bromocresol Purple, or Thymol Blue) is grafted onto polyurethane (PU) using 2,2-dimethylolpropanoic acid (DMPA) to enhance water compatibility. The indicator-grafted, water-compatible PU is analysed for soft-segment thermal, tensile, and shape recovery properties, fast colour change depending on various pH conditions, and low-temperature flexibility. The PU surface becomes water compatible as DMPA content increases, and the characteristic UV-vis absorbance is observed for each grafted indicator. The PU series exhibits a sharp increase in tensile stress and crosslink density at low DMPA content, but a decrease with increased DMPA content. The glass transition temperature increases significantly with increased DMPA content. Shape recovery remains high, but shape retention sharply decreases after an indicator is grafted. The grafting of pH indicator onto PU improves the low-temperature flexibility and imparts an immediate colour change according to the solution pH and grafted indicator.

Two series of polyurethane (PU) containing 2,2-bis(hydroxymethyl)propanoic acid (DMPA) and the grafted benzimidazole (BI) were prepared to compare their antifungal activities. The DMPA carboxyl group of BN series was completely ionized using a strong base (NaOH) and the DMPA carboxyl group of BT series was partly ionized by a weak base (trimethylamine). The BN series exhibited a faster decrease in maximum tensile strength and strain at break compared to the BT series. The fully ionized DMPA carboxyl group of BN series severely affected the thermal and mechanical properties. Finally, the BN series demonstrated a complete suppression of fungal growth (Chaetomium globosum) whereas unmodified PU and the BT series could not fully suppress the growth of fungi at the same BI content. Therefore, the complete ionization of DMPA carboxyl group played an important role in the antifungal activity.

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.

Polycaprolactam or polycaprolactone was graft-polymerized onto polyurethane (PU) to control the water vapor permeation and improve the tensile strength of PU. The tensile strength of the PU sharply increased with the grafting of polycaprolactam or polycaprolactone, without a decrease in the tensile strain. The soft segment melting properties did not significantly change with the increase in the lactam or lactone content. The shape recovery and shape retention of the PU series remained high after the grafting. The water vapor permeability (WVP) was reduced by the grafting of the polycaprolactam, whereas the WVP was increased by the grafting of polycaprolactone.

Lateral cross-linking of polyurethane (PU) was used in this study to improve the tensile strength, thermal stability, and shape memory effect of PU. The hard segment in the middle of PU was used as the cross-linking site to attain high tensile stress and reproducible shape recovery without a significant decrease in tensile strain. Specifically, we investigated whether lateral cross-linking of PU using isophorone diisocyanate (IPDI) is feasible by linking the carbamate bonding or glycerol hydroxyl groups of PU. Therefore, the effects of the IPDI cross-linking site and the cross-linker content were examined by comparing the thermal, tensile, and shape memory properties as well as the cross-link density and water swelling with those of unmodified PU.

Citric acid (CA) was used as a grafted group onto polyurethane (PU) to form a CA-grafted PU series, with a control PU series containing free CA prepared for comparison. With an increase in the CA content, the enthalpy change during the melting increased for the PU and CPU series, and the glass transition temperature increased with the increase in CA content for the PU series but not for the CPU series. The tensile strengths of the PU series sharply increased with the CA content, whereas those of the CPU series did not. The PU series demonstrated better low-temperature flexibility and water permeability than the unmodified PU.

Polyurethanes containing polycaprolactone diol or poly(tetramethylene ether)glycol as a soft segment and 4,4′-methylenebis(phenyl isocyanate) as a hard segment were used as a polymer frame. Polydimethylsiloxane was grafted onto polyurethanes to reduce the molecular interactions and to improve the mobility of polyurethanes, and the plasticizing groups, n-butyl and 2-ethylhexyl, were attached to polyurethanes by graft polymerization. With an increase in the polydimethylsiloxane content, the Tg of the polydimethylsiloxane–polyurethanes gradually increased, whereas the Tg of the n-butyl and 2-ethylhexyl-attached polyurethanes was not affected by a change in their composition. The polydimethylsiloxane-grafted polyurethanes demonstrated excellent tensile strength, shape recovery, and low-temperature flexibility.

Polydimethylsiloxane (PDMS) was grafted onto polyurethane (PU) to form a P series, and 2-ethylhexyl acrylate (EHA) was graft-polymerized onto PU to form an E series. The spectroscopic, thermal, tensile, shape memory, and low-temperature flexibility properties of the P and E series were compared. With an increase in the PDMS content, the Tg of the P series gradually increased, whereas the Tg of the E series was not affected by an increase in the EHA content. The tensile strength of the P and E series sharply increased with the PDMS or EHA content without a significant decrease in tensile strain. The shape recovery of the P and E series remained high after four repeated tests. However, shape retention of the P series significantly decreased with an increase in the PDMS content. Finally, the P series demonstrated excellent low-temperature flexibility from −35°C compared with the E series and control PUs.

Epichlorohydrin (ECH) was used as a cross-linking agent for a series of polyurethanes (PU series). The spectroscopic, thermal, tensile, shape memory, low-temperature flexibility, and water vapor permeability properties of these PUs were compared with those of a control polyurethane series (CPU series) without ECH cross-linking. In the thermal test, the soft segment crystallization of the PU series disappeared as the ECH cross-linking increased. The glass transition temperature (Tg) of the PU and CPU series slightly increased with the increase in ECH content. The tensile strength of the PU series sharply increased at a critical ECH content, whereas that of the CPU series did not. The breaking strain of the PU and CPU series remained the same with the increase in ECH content. The shape recovery of the PU series remained above 90% at 45°C but increased moderately with the increase in ECH content at 0°C. Finally, the PU series with ECH cross-linking demonstrated better low-temperature flexibility and lower water vapor permeability than the unmodified PU.

Polyurethane was grafted with benzoic acid (BA series) or a phenyl group (C series) to compare the impact of the grafted groups on water contact angle, tensile strength, shape memory, and low temperature flexibility. Benzoic acid is different from a phenyl group because it has both a rigid phenyl ring and a carboxyl group. The tensile strengths of the BA and C series substantially increased compared to that of the unmodified polyurethane. The BA series with the grafted benzoic acid exhibited excellent low temperature flexibility compared to the C series with the grafted phenyl group.

Polyurethane (PU) was graft polymerized with poly(acrylic acid) (PA) to form a PA-grafted PU (UA) series, and a control PU (C) series containing free PA was also prepared for comparison. The grafted PA could be ionized, and an ionized PA-grafted PU (IUA) series was separately prepared. The spectroscopic, thermal, tensile, shape memory, low-temperature flexibility, and water permeability properties of the polymer series were compared. With an increase in the PA content, the T m did not change, but ΔH m decreased for the UA, IUA, and C series. The T g did not significantly change with the increase in PA content for the UA, IUA, and C series. The tensile strengths of the UA and IUA series sharply increased with the PA content, whereas that of the C series did not. The breaking strain of the UA, IUA, and C series remained the same with the increase in PA content. The shape recovery and shape retention of the PU–PA series remained high after four repeated tests. Finally, the IUA series PU demonstrated better low-temperature flexibility and water compatibility than the unmodified PU.

Polyacrylonitrile (PAN) or poly(methyl methacrylate) (PMMA) was graft-polymerized onto polyurethane (PU) to form the urethane-acrylate polymers grafted with PAN (UA series) or PMMA (UM series). With an increase in the acryl content, the T m, ΔH m , and T g did not significantly change for the UA and UM series. The tensile strengths of the UA and UM series increased with the acryl content, whereas those of the control PUs did not. The breaking strain of the UA and UM series, and control PUs remained the same with the increase in the acryl content. The shape recovery and shape retention of the UA and UM series remained high after four repeated tests. The UA and UM series demonstrated better low-temperature flexibility and water permeability than the unmodified PU.

A series of polyurethanes (PUs) grafted with poly(isobornyl acrylate) (PIBA) was prepared to form a series (denoted the I series), which was compared with the PUs containing free PIBA (denoted the C series). The bulky and rigid bicyclic isobornyl groups attached to the PIBA chains were intended to hinder the molecular interactions between PU chains and improve the low temperature flexibility of the PUs. The soft segment melting temperature (Tm) was not changed by the increase of the isobornyl acrylate (IBA) content; however, the enthalpy change of melting (ΔHm) sharply decreased. The C series PUs did not exhibit similar differences in response to the IBA content change. The tensile strength of the I series sharply increased at low IBA content due to the physical crosslinking and decreased at high IBA content due to the repulsion between PU chains. The I series demonstrated an improved low temperature flexibility compared with the unmodified and the C series PUs.

A polyurethane series containing grafted polystyrene and a Control series with free polystyrene were prepared, and their spectroscopic, thermal, tensile, shape-memory, and low-temperature flexibility properties were compared. The grafted polystyrene significantly reduced the ΔHc and also reduced the crystallization peaks of the polyurethane series. The tensile strength of the polyurethane series sharply increased with polystyrene content, whereas the Control series did not. The shape recovery of the polyurethane series remained high but the shape retention gradually decreased after four repeated tests. Lastly, the polyurethane series grafted with polystyrene demonstrated excellent low-temperature flexibility.

Cellulose derivatives were grafted to polyurethane (PU), and the effect of grafting on water vapor permeation was evaluated. The cellulose derivative grafting did not significantly change the soft segment melting temperature; however, the grafting affected the enthalpy change for the soft segment melting. The light cross-linking by the grafted cellulose derivatives significantly increased PU tensile strength but did not affect tensile strain. Unexpectedly, water vapor permeability (WVP) at 50°C was decreased by the grafted cellulose derivative, and the decrease in WVP was particularly severe for the cellulose acetate-PU. The molecular weight and capping group of the cellulose derivative affected PU membrane WVP. In addition, the PU layer became less permeable to water vapor with the increase of cellulose derivative content because the water vapor path was restricted.

End groups with different structures were grafted to polyurethane (PU) using poly(dimethylsiloxane) (PDMS) as a spacer. The low-temperature toughness of the PUs was tested at −30°C, and the structure selectivities of the end groups for low-temperature toughness were compared. The PDMS functioned as a flexible linker that connected the end groups to the PUs. The tensile strength of the PU generally improved despite the grafting of PDMS and end groups. The conventional shape recovery ratio at 45°C remained greater than 90%, regardless of the content and structure of PDMS and the end group. The PU that contained an adamantyl group (cubic) or a naphthyl group (planar rectangle) showed instant recovery, even at −30°C, but the PU that contained a phenyl (planar square) or phenoxyphenyl (bent squares) group required warming to 0°C for a similar degree of recovery but showed improvement over a linear PU without any end group. The characteristic structure of the end group was responsible for the selective low-temperature toughness. The low-temperature toughness results and the thermal and mechanical properties of the PUs are discussed. POLYM. ENG. SCI., 55:1931–1940, 2015. © 2014 Society of Plastics Engineers

Photo-polymerization of the acrylate monomers, butylacrylate or 2-hydroxyethyl methacrylate, was initiated by polyurethane (PU) grafted benzophenone to prepare a series of urethane acrylate (UA) polymers. The UA polymers were characterized based on their thermal, spectroscopic, mechanical, and low temperature flexibility properties. In this system, poly(acrylate) chains grew from the grafted benzophenone by photo-polymerization and affected the molecular interactions between PU polymers. The soft segment glass transition temperature (T g ) and melting temperature (T m ) were unaffected by the grafted poly(acrylate) chains. The tensile mechanical strength and the tensile strain of the UA series increased significantly with the attachment of the poly(acrylate) chains. Furthermore, shape recovery and shape retention remained high as the test cycle was repeated. Low temperature flexibility testing demonstrated that the synthesized UA was more flexible at a lower temperature than the unmodified PU.

The production of waste bottom ash (BA) from coal power plants in the west coast of South Korea has been a serious environmental problem to resolve. In this investigation, waste BA was recycled to prepare BA/polypropylene and BA/polyethylene composites, and their mechanical properties were compared. The hazardous metal content in the waste BA was minimal, and the waste BA was not contaminated by sea water. The surface of the BA was coated with one of three cationic surfactants, cetylpyridinium chloride, benzethonium chloride, or benzalkonium chloride, to improve the interface compatibility between the polymer matrices and BA surface. The mechanical properties of the BA composites decreased as the BA content increased and were dependent on the content of BA rather than on particle size. Coating surfactants onto BA significantly improved the mechanical properties, especially the compressive strength, of the BA composites. Finally, the BA composites were successfully applied in the fabrication of a car parking safety product that satisfied the required safety standards.