Siloxane‐based segmented poly(urethane‐urea) elastomer: Synthesis and characterization

A series of segmented poly(urethane‐urea) block copolymers were synthesized with varying proportions of polydimethylsiloxane diols in combination with polytetramethylene ether glycol (PTMG) using 4,4'‐methylenediphenyl diisocyanate followed by chain extension with a (50:50 mol %) mixture of 4,4'‐methylene‐bis(3‐chloro‐2,6‐diethylaniline) (M‐CDEA) and 1,4‐butanediol (BD). The molecular structures of polydimethylsiloxane urethane‐ureas were characterized by ATR‐FTIR and ¹H‐NMR spectroscopic techniques. Distribution of siloxane domain and its influence on surface roughness were investigated by scanning electron microscopy (SEM) and atomic forced microscopy (AFM), respectively. The mechanical and thermal properties of the elastomers were studied by thermogravimetric analysis, dynamical mechanical thermal analysis, and tensile measurement. The results showed that by incorporation of polydimethylsiloxane diol and M‐CDEA chain extender in polyurethane formulation, some improvements in thermal stability, fire resistance and surface hydrophilicity were achieved. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1743–1751, 2013     

Synthesis and characterization of calcium‐containing poly(urethane‐urea)s

A calcium salt of mono(hydroxyethoxyethyl)phthalate [Ca(HEEP)2] was synthesized by the reaction of diethylene glycol, phthalic anhydride, and calcium acetate. Four different bisureas like hexamethylene bis(ω,N‐hydroxyethylurea), tolylene 2,4‐bis(ω,N‐hydroxyethylurea), hexamethylene bis(ω,N‐hydroxypropylurea), and tolylene 2,4‐bis(ω,N‐hydroxypropylurea) were prepared by reacting ethanolamine or propanolamine with hexamethylene diisocyanate (HMDI) or tolylene 2,4‐diisocyanate (TDI). Calcium‐containing poly(urethane‐urea)s (PUUs) were synthesized by reacting HMDI or TDI with 1:1 mixtures of Ca(HEEP)2 and each of the bisureas using di‐n‐butyltin dilaurate as a catalyst. The PUUs were well characterized by Fourier transform infrared, 1H‐ and 13C‐NMR (nuclear magnetic resonance), solid‐state 13C cross‐polarization–magic angle spinning NMR, viscosity, solubility, elemental, and X‐ray diffraction studies. Thermal properties of the polymers were also studied by using thermogravimetric analysis and differential scanning calorimetry. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3488–3496, 2003     

Thermal and mechanical properties of polyisobutylene‐based thermoplastic polyurethanes

We investigated thermal and mechanical properties of thermoplastic polyurethanes (TPUs) with the soft segment comprising of both polyisobutylene (PIB) and poly(tetramethylene)oxide (PTMO) diols. Thermal analysis reveals that the hard segment in all the TPUs investigated is completely amorphous. Significant mixing between the hard and soft segments was also observed. By adjusting the ratio between the hard and soft segments, the mechanical properties of these TPUs were tuned over a wide range, which are comparable to conventional polyether‐based TPUs. Constant stress creep and cyclic stress hysteresis analysis suggested a strong dependence of permanent deformation on hard segment content. The melt viscosity correlation with shear rate and shear stress follows a typical non‐Newtonian behavior, showing decrease in shear viscosity with increase in shear rate. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 891‐897, 2013     

Synthesis and characterization of polyhydroxylated polybutadiene binding 2,2′‐thiobis(4‐methyl‐6‐tert‐butylphenol) with isophorone diisocyanate

A macromolecular hindered phenol antioxidant, polyhydroxylated polybutadiene containing thioether binding 2,2′‐thiobis(4‐methyl‐6‐tert‐butylphenol) (PHPBT‐b‐TPH), was synthesized via a two‐step nucleophilic addition reaction using isophorone diisocyanate (IPDI) as linkage. First, the ? OH groups of PHPBT reacted with secondary ? NCO groups of IPDI to form the adduct PHPBT‐NCO, then the PHPBT‐b‐TPH was obtained by one phenolic ? OH of 2,2′‐thiobis(4‐methyl‐6‐tert‐butylphenol) (TPH) reacting with the PHPBT‐NCO. The PHPBT‐b‐TPH was characterized by Fourier transform infrared spectroscopy, ¹H nuclear magnetic resonance (¹H‐NMR), ¹³C‐NMR, and thermogravimetric analysis, and its antioxidant activity in natural rubber was studied by an accelerated aging test. Influences of reaction conditions on the two nucleophilic reactions between ? OH group and ? NCO group were investigated. In addition, catalytic mechanism for the reaction between PHPBT‐NCO and TPH was discussed. The results showed that the adduct PHPBT‐NCO could be obtained by using dibutyltin dilaurate (DBTDL) as catalyst, and the suitable temperature and DBTDL amount were 35°C and 3 wt %, respectively. However, triethylamine (TEA) was more efficient than DBTDL to catalyze the reaction between PHPBT‐NCO and TPH because of steric hindrance effect. In addition, it was found that the thermal stability and antioxidant activity of PHPBT‐b‐TPH were higher than those of the low molecular weight antioxidant TPH. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40942.     

An imidazolium‐functionalized isobutylene polymer having improved mechanical and barrier properties: Synthesis and characterization

Brominated poly(isobutylene‐co‐p‐methylstyrene) (BIMS) is of great use to industries because of its extremely good permeability properties. However, it lacks strength and adhesion necessary to make it amenable to various processing techniques. To overcome the limitations of BIMS, ionic modification via nucleophilic substitution of bromine by 1‐methylimidazole through a facile synthetic route is presented. The modified ionic product was characterized by various techniques such as solubility, Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy (NMR), thermogravimetric analysis, and dynamic mechanical analysis. The FTIR spectrum of the obtained samples showed a distinct peak around 1261 cm^?1 corresponding to C? N stretching vibration and reduction in peak intensity around 695 cm^?1 corresponding to C? Br stretching vibration. NMR also clearly showed the occurrence of a singlet peak corresponding to the methyl protons of imidazole in the region of 4.1 ppm and a shift in the methylene protons adjacent to the benzene ring confirming the substitution of bromine atom by imidazole ring. The reaction at reflux temperature of 130°C for 48 h yielded the highest level (3.1 wt %, 1.18 mol %) of modification while optimizing the reaction parameters. The modified ionic polymers displayed greater thermal stability, greater flexibility, improved tensile strength, and higher barrier properties compared to the unmodified BIMS. A 1.8‐fold increase of elongation at break was achieved with 1.18 mol % (3.1 wt %) of modification. The modified polymers also showed remarkable drop in oxygen transmission rate values from 10^?16 to 10^?18 m³ m/m²/s/Pa, which further highlights their improved properties. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis and application of hyperbranched poly(urethane‐urea) finishing agent with amino groups

The isocyanate‐terminated linear polyurethane prepolymer (LPPU) was successfully synthesized via step‐by‐step polymerization, with isophorone disocyanate (IPDI) and polytetramethylene ether glycol (PTMG, M_n = 2000 g/mol) used as raw materials, dibutyltin dilaurate (DBTDL) as the catalyst, 1,4‐butanediol (BDO) as the chain extender and anhydrous ethanol (EtOH) as the blocking agent. Then the hyperbranched poly (urethane‐urea) (HBPU) containing amino groups was synthesized by grafting LPPU on amino‐terminated hyperbranched polymers (NH₂‐HBP). The molecular structure of LPPU and HBPU were characterized by means of FT‐IR and ¹H‐NMR. It was founded that LPPU and HBPU were successfully synthesized as anticipated. The thermal stability and crystalline morphology of LPPU and HBPU were characterized and analyzed by TG and XRD. Additionally, it was also found that, after addition of 10% HBPU, the water absorption rate, water vapor transmission rate, and water vapor permeability increased markedly by 162.02%, 400.00%, 260.00%, respectively. The tensile strength of membrane decreased by 24.57% and the elongation at break increased by 26.92%. Compared with the leather finished by commercial PU finishing agent, the leather finished by HBPU presented better properties. The water vapor permeability of the leather finished by increased by 13.0%, and the dry‐ and wet‐rub resistances and the physical and mechanical performances were excellent. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44139.     

Thermal analysis and mechanical characterization of maleimide‐functionalized benzoxazine/epoxy copolymers

Maleimide‐functionalized benzoxazine is copolymerized with epoxy to improve toughness and processibility without compromising the thermal properties. The incorporation of maleimide functionality into the benzoxazine monomer results in a high performance polymer. All three possible polymerization reactions are confirmed using Fourier transform infrared (FT‐IR) spectroscopy. While maleimide‐functionalized benzoxazine has a glass transition temperature, T_g, of 252°C, a further 25°C increase of T_g is observed when copolymerized with epoxy. The flexural properties are also measured, and the copolymers exhibit a flexural modulus of 4.2–5.0 GPa. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1670–1677, 2006     

Synthesis and thermomechanical properties of allyl‐functionalized polycaprolactone urethane‐co‐2‐hydroxylethyl methacrylate networks

PCL‐segmented multiallyl‐functionalized poly (ester urethane) prepolymers (PEUs) were prepared in a two‐step process. First, hydroxyl‐terminated PCL and glycerol simultaneously reacted with an excess of a diisocyanate, the obtained isocyanate functionalized prepolymers then reacts with allyl amine. PEUs structure choice mainly focused on two aspects: the PCL segments concentration and the allyl functionality that, respectively, affects the biodegradability and the density of the issued networks. The concentrations of the different reactants were fixed, taking into account the desired mean structure and also to prevent crosslinking during the synthesis of the prepolymers. FTIR was principally used to monitor the synthesis of allyl functionalized PEUs. The carbonyl absorption of PCL, initially located at 1720 cm^?1, reaction of the PCL and shifted toward 1730 cm^?1, due to a decrease in crystallinity as confirmed by DSC. The structure of allyl‐functionalized PCL‐segmented PEU analyzed by ¹H NMR, double bond content was between 0.2 and 1.2 mmol g^?1. Networks were obtained by UV‐initiated radical copolymerization of allyl‐functionalized PEUs and HEMA. The effects of PCL concentration and molar mass on their thermomechanical and thermal properties were analyzed. Particular damping properties were obtained. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41295.     

Synthesis and characterization of main‐chain,second‐order,nonlinear optical polyurethanes with isolation moieties and zigzag structures

In this study, two main‐chain second‐order nonlinear optical (NLO) polyurethanes were successfully prepared with indole‐based chromophores. The introduced phenyl isolation group and the continuous zigzag polymer backbone were found to be helpful for effectively decreasing the intermolecular dipole–dipole interactions and enhancing the NLO properties of the resulting polymers. The studied polymers exhibited good optical transparency, high thermal stability, and excellent NLO effects; this indicated that the nonlinearity–stability trade‐off and nonlinearity–transparency trade‐off could be alleviated by this newly designed polymer system. Poly{4‐anilinocarbonyl[N‐ethoxyl‐5‐phenyl‐3‐azo(2′‐oxyethylene‐4′‐nitrobenzene)indole]carbonylimino} with a zigzag backbone showed a large second harmonic generation coefficient (d₃₃) value of 88.4 pm/V. However, poly{5‐naphthyliminocarbonyl[N‐ethoxyl‐5‐phenyl‐3‐azo(2′‐oxyethylene‐4′‐nitrobenzene)indole]carbonylimino} (PUAZN) with a continuous zigzag structure exhibited a higher d₃₃ value of 116.2 pm/V, which was attributed to the unique rigid and zigzag linkage of 1,5‐naphthalene as the isolation spacer. The enhanced NLO efficiency and relatively longer term temporal stability made PUAZN as a promising candidate for practical applications in photonic devices. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42974.     

Heat‐triggered poly(siloxane‐urethane)s based on disulfide bonds for self‐healing application

Polydimethylsiloxane (PDMS) is one of the most widely employed silicon‐based polymers for its high flexibility, low usage temperature, excellent water resistance, outstanding electrical insulting property, and physiological inert, etc. However, the covalent‐bonded Si? O bonds are unable to heal automatically when damaged, which would result in the failure of the materials and devices. Disulfide bond based polymers show high healing efficiency at moderate temperature and have been investigated intensively. Herein, we report a PDMS‐based polyurethane self‐healing polymer (PDMS‐PU) modified with disulfide bonds, which exhibited a reinforced thermal stability, excellent stretchability, and satisfactory self‐healing ability. The effect of different ratio of PDMS and disulfide bond contents on the elastomer properties was investigated. With the increase of PDMS content, the decomposition temperature of the PDMS‐PU‐3 (332 °C) elastomer with highest content of PDMS was increased by 34 °C compared to PDMS‐PU‐1 (298 °C) with lowest content of PDMS and exhibited a largest elongation at break of 1204%. PDMS‐PU‐1 with highest content of disulfide bond possessed a highest healing efficiency of 97%. The results indicated the PDMS‐PU elastomers can be used as self‐healing flexible substrate for flexible electronics. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46532.     

Thermal and mechanical properties of epoxy resin reinforced with modified iron oxide nanoparticles

Epoxy polymers, having good mechanical properties and thermal stability, are often used for engineering applications. Their properties can be further enhanced by the addition of iron oxide (Fe₃O₄) nanoparticles (NPs) as fillers to the resin. In this study, pristine Fe₃O₄ NPs were functionalized with polydopamine (PDA), (3-glycidoxypropyl)trimethoxysilane (GPTMS), and (3-aminopropyl)trimethoxysilane (APTES). X-ray diffraction and scanning electron microscopy (SEM) were used to study any changes in the crystal structure and size of the NPs while Fourier-Transform Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis (TGA) were used to ensure the presence of functional groups on the surface. The mechanical properties of the Fe₃O₄-based nanocomposites generally improved except when reinforced with Fe₃O₄/PDA. The maximum improvement in tensile strength (∼34%) and fracture toughness (∼13%) were observed for pristine Fe₃O₄-based nanocomposites. Dynamic mechanical analysis (DMA) showed that the use of any of the treated NPs improved the material's initial storage modulus and had a substantial impact on its dissipation potential. Also, it was observed that the glass transition temperature measurements by DMA and differential scanning calorimetry were below that of pure epoxy. SEM of the cracked surfaces shows that the incorporation of any NPs leads to an enhancement in its thermal and mechanical properties.     

Thermal and antimicrobial evaluation of cotton functionalized with a chitosan–zeolite composite and microcapsules of phase‐change materials

Antimicrobial cotton was developed with silver zeolites (SZs). Three different application approaches for the cotton surface functionalization were followed: (1) SZ alone, (2) SZ combined with chitosan film, and (3) chitosan–zeolite (CS–SZ) composites previously synthesized by a gelation process with sodium tripolyphosphate. All finishes were applied to the textile materials through conventional pad–dry–cure processes, and the obtained results were then compared. The resulting materials were characterized with Fourier transform infrared spectroscopy, scanning electron microscopy with energy‐dispersive X‐ray spectroscopy, differential scanning calorimetry, IR thermography, and contact angle measurements, and the antimicrobial activity was evaluated. The results suggest that the application of CS–SZ should be recommended for the production of textiles with antibacterial properties because the materials showed activity against Escherichia coli, Staphylococcus aureus, Candida albicans, and Trichophyton rubrum. In addition, the finishing can be combined with the application of microcapsules of phase‐change materials to obtain textiles with thermoregulating properties. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46135.     

Thermo‐responsive polyurethane hydrogels based on poly(ethylene glycol) and poly(caprolactone): Physico‐chemical and mechanical properties

In this work, we present the synthesis and characterization of chemically crosslinked polyurethanes (PU) composed of poly(ethylene glycol) (PEG) and poly(caprolactone) diol (PCL‐diol), as hydrophilic and hydrophobic segments respectively, poly(caprolactone) triol (PCL‐triol), to induce hydrolysable crosslinks, and hexamethylene diisocyanate (HDI). The syntheses were performed at 45 °C, resulting in polyurethanes with different PEG/PCL‐diol/PCL‐triol mass fractions. All the PUs are able to crystallize and their thermal properties depend on the global composition. The water uptake capacities of the PU increase as the PEG amount increases. The water into hydrogels is present in different environments, as bounded, bulk and free water. The PU hydrogels are thermo‐responsive, presenting a negative dependence of the water uptake with the temperature for PEG rich networks, which gradually changes to a positive behavior as the amount of poly(caprolactone) (PCL) segments increases. However, the water uptake capacity changes continuously without an abrupt transition. Scanning electron microscopy (SEM) analyses of the hydrogel morphology after lyophilization revealed a porous structure. Mechanical compression tests revealed that the hydrogels present good resilience and low recovery hysteresis when they are subject to cycles of compression–decompression. In addition, the mechanical properties of the hydrogels varies with the composition and crosslinking density, and therefore with the water uptake capacity. The PU properties can be tuned to fit for different applications, such as biomedical applications. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43573.     

Thermal and mechanical properties of microwave‐ and heat‐cured poly(methyl methacrylate) used as dental base material

The thermal and mechanical properties of dental base materials cured by microwave and conventional heat methods were studied. The commercial dental base poly(methyl metacrylate) (PMMA) powder and liquid were mixed in a 3/1 ratio. They were polymerized by a peroxy catalyst at 65°C, then cured with a boiling water temperature and microwave radiation for periods of 5, 10, 15, 20, 25, 30, and 35 min for heat curing and 1, 2, 3, 5, and 7 min for microwave radiation. The microwave radiation outputs used were 500 and 700 W. The products of 5‐min heat curing and 1‐, 2‐, and 7‐min microwave curing were soluble in chloroform. All the others were partially soluble. The viscosity‐average molecular weights of the soluble samples were about 1 × 10⁶. The thermal properties of the polymer samples were studied by differential scanning calorimetry (DSC). For the samples that were not cured completely, broad exothermic peaks at around 125°C were obtained in the DSC thermograms. The glass‐transition temperatures for completely cured samples were 110–120°C. The mechanical properties of the samples were determined from tensile and three‐point bending tests. The elastic modulus was highest for samples obtained by the conventional method with a 30‐min curing period. However, the bending modulus was highest for 7‐min cured samples in a 700‐W microwave. The mechanical strengths of the 700‐W output were higher than those at 500 W. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 251–256, 2003     

New copoly(urethane‐methacrylate)s obtained by adjusting the content of the poly(1,2‐propanediol ortho‐phthalate): Transparent,thermal, and mechanical properties

A series of new crosslinked copoly(urethane‐methacrylate)s (CPUAs) were synthesized by the polymerization of new urethane–methacrylate macromonomers with double bonds at the end of the chain, which were prepared from isophorone diisocyanate, β‐hydroxyethyl methacrylate, different content of poly(1,2‐propanediol ortho‐phthalate) (PPP), and poly(ethylene glycol) 600. The properties of CPUAs were measured by dynamic mechanical analysis, thermogravimetric analysis, wide‐angle X‐ray diffraction, water uptake, and optical properties testing, and mechanical performance measurements. The results revealed that the greater PPP contents in the CPUAs lead to the higher glass transition temperature, hardness, lower thermal stability, and water uptake. Obtained CPUAs present the good transparence. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Ionic conductivity and dielectric behavior of novel poly(vinyl formal)‐based single‐ion‐conductor polymer electrolytes

Novel single‐ion‐conductor polymer (SCP) electrolytes based on oxalate‐chelated‐borate‐structure‐grafted poly(vinyl formal) (PVFM) were synthesized via a solution casting technique. The influence of the molar ratio of ? OH and boron atoms in PVFM on the ionic conductivity (σ) of the SCP electrolytes at different temperatures was investigated with alternating‐current impedance spectroscopy in the frequency range of 0.01 Hz to 1 MHz. The results show that σ of the SCP electrolytes at 15–60 °C was about 10^?6–10^?5 S/cm, and temperature dependence of the conductivity of the electrolytes followed the Vogel–Tamman–Fulcher relationship. The dielectric behaviors of the SCP electrolytes were analyzed in view of the dielectric permittivity and dielectric modulus of the electrolytes. Dielectric analysis revealed that the transport of Li⁺ ions in the PVFM‐based SCP electrolytes mainly followed a hopping mechanism coupled with the segmental motion of the polymer chain. Additionally, a dielectric relaxation was found in the high‐frequency region; this was a thermally activated result and also implied the appearance of carrier hopping. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43510.     

Film formation from pigmented latex systems: Mechanical and surface properties of ground calcium carbonate/functionalized poly(n‐butyl methacrylate‐co‐n‐butyl acrylate) latex blend films

The mechanical and surface properties of films prepared from model latex/pigment blends were studied using tensile tests, surface gloss measurements, and atomic force microscopy. Functionalized poly(n‐butyl methacrylate‐co‐n‐butyl acrylate) [P(BMA/BA)] and ground calcium carbonate (GCC) were used as latex and extender pigment particles, respectively. The critical pigment volume concentration of this pigment/latex blend system was found to be between 50 and 60 vol % as determined by surface gloss measurement and tensile testing of the blend films. As the pigment volume concentration increased in the blends, the Young's modulus of the films increased. Nielsen's equations were found to fit the experimental data very well. When the surface coverage of carboxyl groups on the latex particles was increased, the yield strength and Young's modulus of the films both increased, indicating better adhesion at the interfaces between the GCC and latex particles. When the carboxyl groups were neutralized during the film formation process, regions with reduced chain mobility were formed. These regions acted as a filler to improve the modulus of the copolymer matrix and the modulus of the resulting films. The carboxyl groups on the latex particle surfaces increased the surface smoothness of the films as determined by surface gloss measurement. When the initial stabilizer coverage of the latex particles was increased, the mechanical strength of the resulting films increased. At the same time, rougher film surfaces also were observed because of the migration of the stabilizer to the surface during film formation. With smaller‐sized latex particles, the pigment/latex blends had higher yield strength and Young's modulus. Higher film formation temperatures strengthen the resulting films and also influence their surface morphology. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4550–4560, 2006     

Synthesis,characterization, and pervaporation properties of segmented poly(urethane‐urea)s

Poly(urethane‐urea)s (PUUs) from 2,4‐tolylene diisocyanate (2,4‐TDI), poly(oxytetramethylene)diols (PTMO) or poly(butylene adipate)diol (PBA), and various diamines were synthesized and characterized by Fourier transform infrared spectroscopy, gel permeation chromatography, differential scanning calorimetry, and density measurements. Transport properties of the dense PUU‐based membranes were investigated in the pervaporation of benzene–cyclohexane mixtures. It was shown that the pervaporation characteristics of the prepared membranes depend on the structure and length of the PUU segments. The PBA‐based PUUs exhibit good pervaporation performance along with a very good durability in separation of the azeotropic benzene–cyclohexane mixture. They are characterized by the flux value of 25.5 (kg μm m⁻² h⁻¹) and the separation factor of 5.8 at 25°C, which is a reasonable compromise between the both transport parameters. The PTMO‐based PUUs display high permeation flux and low selectivity in separation of the benzene‐rich mixtures. At the feed composition of 5% benzene in cyclohexane, their selectivity and flux are in the range of 3.2 to 11.7 and 0.4 to 40.3, respectively, depending on the length of the hard and soft segments. The chemical constitution of the hard segments resulting from the chain extender used does not affect the selectivity of the PUU membranes. It enables, however, the permeability of the membranes to be tailored. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1615–1625, 1999     

Thermal,mechanical, and shape‐memory properties of nanorubber‐toughened,epoxy‐based shape‐memory nanocomposites

Epoxy‐based shape‐memory polymers (ESMPs) are a type of the most promising engineering smart polymers. However, their inherent brittleness limits their applications. Existing modification approaches are either based on complicated chemical reactions or done at the cost of the thermal properties of the ESMPs. In this study, a simple approach was used to fabricate ESMPs with the aim of improving their overall properties by introducing crosslinked carboxylic nitrile–butadiene nanorubber (CNBNR) into the ESMP network. The results show that the toughness of the CNBNR–ESMP nanocomposites greatly improved at both room temperature and the glass‐transition temperature (T_g) over that of the pure ESMP. Meanwhile, the increase in the toughness did not negatively affect other macroscopic properties. The CNBNR–ESMP nanocomposites presented improved thermal properties with a T_g in a stable range around 100 °C, enhanced thermal stabilities, and superior shape‐memory performance in terms of the shape‐fixing ratio, shape‐recovery ratio, shape‐recovery time, and repeatability of shape‐memory cycles. The combined property improvements and the simplicity of the manufacturing process demonstrated that the CNBNR–ESMP nanocomposites are desirable candidates for large‐scale applications in the engineering field as smart structural materials. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45780.     

Shape‐memory property and characterization of epoxy resin‐modified Mesua ferrea L. seed oil‐based hyperbranched polyurethane

Modification of existing polymers leads to enhancement of many desirable properties. So, a hyperbranched polyurethane (HBPU) of monoglyceride of Mesua ferrea L. seed oil, poly(ε‐caprolactone)diol (M_n = 3000 g mol^?1), 2,4‐toluene diisocyanate, and glycerol with 30% hard segment (NCO/OH = 0.96) has been modified with different amounts of bisphenol‐A based epoxy resin. The system is cured by poly(amido amine) hardener at 120°C for specified period of time. Improvement of thermostability, scratch hardness, and impact strength are observed by this modification of HBPU. The differential scanning calorimetry (DSC) results show improvement of melting temperature of the modified systems. The enhancement of tensile strength is about 2.4 times compared with that of the unmodified one. The morphology and structural changes due to variation of epoxy content was studied by scanning electron microscopy (SEM) analysis and Fourier transform infrared (FTIR) spectroscopy. The rheological properties of the epoxy‐modified HBPU show the dependence on the amount of epoxy resin. Shape memory study of the crosslinked HBPUs shows 90–98% thermoresponsive shape recovery. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010