Enhanced adhesion force based on microphase separation induced by complexation of ferric ions and polyurethane matrix

Waterborne polyurethane elastomer (WPU) has been widely used as a glue, but it still has some drawbacks, including a long cure time and weak adhesive force. In order to overcome these drawbacks, a new composite [PU/ferric ion complexation (Fe/PU)] with high adhesive strength was successfully prepared using ferric ion (Fe³⁺) as a complexing agent. Fourier transform infrared spectroscopy, differential scanning calorimetry, dynamic mechanical analysis, and tensile testing were used to characterize the chemical structure and mechanical properties of the as‐obtained composites. Introduction of the ferric ion induces a certain degree of microphase separation, resulting in better mechanical strength and interfacial adhesion. The mechanical properties of the PU composite with ferric ions are higher than that of pure PU. The adhesive strength of the 25%‐Fe/PU composite is 32.46 ± 3.1 MPa, exhibiting superior adhesive strength. The tensile strength was enhanced 34%, and the elongation was enhanced 23.6% compared to pure PU. Furthermore, the Fe/PU composite, coordinated with ferric ions, exhibits an enhanced storage modulus and reduced loss coefficient compared to PU. We can foresee that Fe/PU composites will play an important role in the building and engineering areas. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46069.     

Toughening of polylactide via in situ formation of polyurethane crosslinked elastomer during reactive blending

Polylactide (PLA)/polyurethane (PU) composites were prepared by reactive blending method with in situ formation of PU particles via the reaction between polyester polyol (PPG) and toluene‐2,4‐diisocyanate (TDI). The interfacial compatibility and adhesion between the PLA and PU phases were greatly improved by the reaction of the terminal hydroxyl groups of PLA and N?C?O groups of TDI forming graft copolymer, as confirmed by FTIR spectroscopy. The elongation at break and notch impact strength of PLA/PU composites increased considerably with increasing PU content, and the tensile strength of PLA/PU composites decreased slightly compared with that of pure PLA. Upon addition of 12 wt % PU, the elongation at break and notch impact strength increased to 175.17% and 10.96 kJ/m², respectively, about 27 times and 5.4 times greater than the corresponding values for the pure PLA. The tensile strength decreased only slightly to 48.65 MPa. The excellent interfacial adhesion, the dispersed PU elastomeric particles acting as stress concentration areas, and the triggering of large matrix shear yield as well as many fibrils by internal cavitation were the main mechanical toughening mechanisms. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44383.     

Effects of Temperature on Morphology and Properties of Films Prepared from Poly(ester‐urethane) and Nitrochitosan

Summary: Novel elastic materials were prepared by mixing semicrystalline polyester‐based polyurethane (PU) synthesized at 100 °C with nitrochitosan (NCH) and 1,1,1‐tris(hydroxylmethyl)propane as crosslinker, and then by curing the mixture at 18, 25, 40, 60, and 80 °C. The effects of cure temperature on the crystallization behavior, miscibility, and mechanical properties of the PUNCH materials were studied by attenuated total reflection Fourier transform IR, wide‐angle X‐ray diffraction, scanning electron microscopy, dynamic mechanical analysis, X‐ray photoelectron spectroscopy, and tensile test. The results indicated that the crystalline structure of the blend films was more easily interrupted as the cure temperature increased, leading to a decrease of the degree of crystallinity. With an increase of cure temperature, the blend films exhibited high crosslinking density and tensile strength, and the phase separation between hard and soft segments of PU enhanced, resulting in a decrease in the glass transition temperature (T_g) of soft segment. Interestingly, the composite films keeping high elongation at break possessed tensile strength higher than that of the native poly(ester‐urethane). The enhanced mechanical properties of the blend films can be attributed to the relatively dense crosslinking network and strong intermolecular hydrogen bonding between NCH and PU. Therefore, this study not only provided a novel way by adding NCH into PU matrix to prepare elastic materials, which would remain functional characteristic of chitosan, but also expanded the application field of chitosan.

The cure temperature dependence of the tensile strength and elongation at break for the PEPU‐100 and PUNCH‐100 films.     

Thermomechanical properties and morphology of interpenetrating polymer networks of polyurethane–poly(methyl methacrylate)

Interpenetrating networks (IPNs) of polybutadiene‐based polyurethane (PU) and poly(methyl methacrylate) (PMMA) were synthesized. The effect of the incorporation of 2% glycidyl methacrylate (GMA) and 2‐hydroxyethyl methacrylate (2‐HEMA) on the thermal, mechanical, and morphological properties of IPNs was investigated. Both 2‐HEMA and GMA led to improvements in these properties. However, 2‐HEMA‐containing IPNs showed somewhat better tensile strength, elongation, and damping characteristics. The morphology of IPNs containing 2‐HEMA showed better mixing of the components. The improvement in the properties was observed for up to 40% PMMA in the IPNs. Differential scanning calorimetry thermograms showed the presence of three glass transitions. The third glass‐transition temperature was explained by possible grafting of methyl methacrylate onto PU. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1576–1585, 2002     

Durability of green polyurethane adhesive bonded aluminum alloy in dry and hydrothermal ageing conditions

Polyurethane (PU) adhesives were prepared from the reaction of polycaprolactone (PCL) polyols based on palm kernel oil based polyesteramide (PPKO) with an aromatic and cycloaliphatic diisocyanate. Four different formulations of PU adhesives were prepared by varying the NCO : OH ratio, in order to investigate the effects of NCO : OH ratios on adhesion strength. The adhesive strength of metal–metal bonding both in dry and hydrothermal ageing—was determined by single lap shear joint testing. The resistance to hydrolysis of the PU adhesives was determined by performing water absorption tests. The water absorption test samples suggested that the durability of the adhesives correlated to lower water absorption due to higher NCO content. The correlation between the crosslinking of the PU network and adhesive strength was also studied by performing swelling tests. The higher NCO content showed that, the higher crosslink density of PUs led to higher cohesion and adhesion strengths. PU1.7 showed optimal properties in terms of durability and resistance to hydrolysis, whereas PU2.0 revealed deterioration in durability and resistance to hydrolysis due to the presence of greater micro‐voids content in the PU2.0 matrix. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41151.     

Effect of polymer architecture and hard/soft segment ratio on the surface morphology and mechanical properties of polyurethane films for potential orthodontic treatment

In this study, polyurethane (PU) films are prepared by using 1,4-butanediol and trimethylolpropane as chain extender and crosslinking agent, respectively. A series of prepolymers are synthesized by varying the feeding molar ratios of methylene diisocyanate to polytetramethylene ether glycol, which are hard and soft segments, respectively. The influence of polymer architecture, chemical composition, and artificial saliva treatment on the surface morphology and mechanical strength of PU films are studied. The crosslinking polymer architecture and higher content of hard segment correlates with enhanced tensile strength and less decrease of tensile strength in the condition of artificial saliva, but reduced elongation at break. The in vitro cytotoxicity study demonstrates that PU films have excellent cytocompatibility.     

Biobased chain extended polyurethane and its composites with silk fiber

The biobased chain extended polyurethane (PU) was synthesized by reacting castor oil based polyol with different diisocyanates [toluene‐2,4‐diisocyanate (TDI) and hexamethylene diisocyanate (HMDI)] and chain extender such as glutaric acid. Biocomposites have been fabricated by incorporating the silk fiber into both TDI‐ and HMDI‐based PUs. The effect of incorporation of silk fiber into TDI‐ and HMDI‐based neat PU on the physicomechanical properties such as density, surface hardness, tensile strength, and percentage elongation have been investigated. The dynamic mechanical properties and the thermal stability of neat PUs and the silk fiber incorporated PU composites have been evaluated. The TDI‐based neat PU has showed higher mechanical properties compared to HMDI‐based PU. The incorporation of 10% silk fiber into TDI‐ and HMDI‐based PU resulted in an enhancement of tensile strength by 1.8 and 2.2 folds, respectively. The incorporation of silk fiber into biobased chain extended PU increased the glass transition temperature (T_g) of the resultant biocomposites. The morphology of tensile fractured neat PUs and their biocomposites with silk fiber was studied using scanning electron microscope (SEM). POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Designing Biomimetic Microphase‐Separated Motifs to Construct Mechanically Robust Plant Protein Resin with Improved Water‐Resistant Performance

Plant protein, as a sustainable alternative to petroleum‐derived resin, has exhibited notable potential for engineering wood products without formaldehyde emission, while the poor mechanical and water‐resistant performances limit its practical applications. Inspired by mussel chemistry and structure, a dopamine‐functionalized polyurethane (D‐PU) elastomer is synthesized in this work acting as a bio‐inspired crosslinking unit to improve the properties of soy protein (SP) resin. It is found that the catechol groups of the incorporated D‐PU not only triggers polyurethane to interact with SP matrix giving rise to a stable crosslinking network with excellent load‐bearing capacity, but also serves as a water‐resistant barrier to reduce the water erosion effect on resin. Moreover, a desired microphase‐separated morphology is observed within the continuous protein phase after introducing D‐PU. The microphase‐separated structure simultaneously strengthens and toughens SP adhesive layer, thus achieving high‐efficiency stress transfer and energy dissipation as well as accelerating SP to further permeate into the substrate forming more mechanical adhesion nails. As a result, the modified SP‐D‐PU resin presents an impressive improvement in dry and wet adhesion strength up to 70.5% and 133.9% compared to the pristine SP resin, respectively. The proposed biomimetic design may offer a workable strategy for preparing of high‐performance bio‐based composites.     

TIPA/BDO扩链的聚氨酯弹性体力学性能的研究

以聚酯(PEA、PEPA)或聚醚(PTMG)和TDI为原料合成聚氨酯(PU)预聚体,用三异丙醇胺(TIPA)和1,4-丁二醇(BDO)的混合物作扩链剂制备PU弹性体。讨论了软段相对分子质量、弹性体交联点相对分子质量和扩链剂的种类对PU弹性体性能的影响。结果表明,PU弹性体的硬度、拉伸强度、300%模量和撕裂强度随软段相对分子质量的增加而下降,而伸长率和冲击弹性随软段相对分子质量的增加而增加;交联点相对分子质量为6600时,PTMG2000为软段的PU弹性体的拉伸强度最高,达到28.44MPa;与TMP/BDO扩链的聚酯型PU弹性体相比,TIPA/BDO扩链的弹性体的拉伸强度、伸长率和撕裂强度均较高,而硬度、300%模量和冲击弹性差异不大。     

Water vapor‐permeable polyurethane ionomer

The reaction of toluene diisocyanate with 2,2,3,3‐tetrafluoro‐1‐propanol (fluoro compound) or 3‐glycidoxypropyl trimethoxysilane(siloxane compound) and other additives to form the structure of the fluoro‐based or siloxane‐based polyurethane (PU) ionomer has been proven by infrared spectra. Experimental results indicated that the amount of water vapor permeability of the film made by fluoro‐based or siloxane‐based PU ionomer appeared to gradually increase with increasing concentration of the siloxane compound or fluoro compound, as a result of the formation of more porosities. Our experimental results also showed that the water vapor absorption was seen to be larger for the film made by siloxane‐based PU ionomer film than for the film made by fluoro‐based PU ionomer film, as a result of increased hydrophilic groups attached to the backbone of the PU ionomer molecule. For the film prepared by siloxane‐based PU ionomer, both tensile strength and elongation appeared to increase with an increase in the concentration of siloxane compound. This may be the result of the intermolecular interaction between siloxane‐based PU ionomer molecules themselves, thus enhancing the crosslinking capability of the ionomer molecules. On the other hand, both tensile strength and elongation for the film prepared by fluoro‐based PU ionomer decreased with increasing concentration of the fluoro compound, as a result of intramolecular interaction greatly reducing the crosslinking capability of the ionomer molecules. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3767–3773, 2006     

A novel approach to prepare PBT nanocomposites with elastomer‐modified SiO2 particles

Poly(butylenes terephthalate) (PBT)/SiO₂ nanocomposites with uniform dispersion, strong interfacial adhesion, and improved mechanical properties have been prepared by a novel approach. Ethylene‐methyl acrylate‐glycidyl methacrylate (E‐MA‐GMA) elastomer chains were first chemically grafted onto the surface of SiO₂ nanoparticles. Fourier transform infrared spectra result shows that elastomer‐modified SiO₂ nanoparticles exhibit absorption at 2963–2862 cm⁻¹ of the stretching modes of C H, which suggests the reaction between the hydroxyl groups of SiO₂ surface and epoxy groups of E‐MA‐GMA. And the binding energy of Si2p and O1s of the elastomer‐modified SiO₂ shifts to lower binding energy, which further confirms the formation of Si O C bonds. This surface treatment allows SiO₂ nanoparticles homogeneously dispersing in PBT matrix. The morphology with loose aggregates contains networked SiO₂ particles with an interparticle distance ranging from 0 to 30 nm. As a result, the storage modulus and the tensile properties of PBT/E‐MA‐GMA‐SiO₂ nanocomposites are higher than those of pure PBT and PBT with untreated SiO₂. The incorporation of E‐MA‐GMA‐modified SiO₂ particles increases the tensile strength and modulus to 58.4MPa and 2661MPa respectively, which is 8% and 16% higher than those of pure PBT. POLYM. COMPOS., 2009. © 2009 Society of Plastics Engineers     

Thermally Reversible Crosslinked Polyurethanes Based on Blocking and Deblocking Reaction

New self‐healing crosslinked bisphenol‐S polyurethane (BPS/PU) including thermal reversible urethane bonds is prepared to balance the mechanical and self‐healing properties. BPS/PU is synthesized with BPS as chain extender to improve the mechanical property in the effect of high molecular regularity of BPS and extra stronger physical crosslinking in BPS/PU. The crosslinked structure of BPS/PU is confirmed by Fourier transform infrared spectra and swelling‐dissolution test. BPS/PU demonstrates great thermal reversability after three heating and cooling cycles and exhibits shorter relaxation time (3.3 min). The tensile strength and the tensile elongation of BPS/PU are up to 14.54 MPa and 877.12%, respectively, which are much higher than the value reported in literature. The qualitative self‐healing analysis of BPS/PU confirms that the cracks can be healed largely after healing progress, and the quantitative self‐healing analysis exhibits great healing properties with the healing efficiency of up to 77.92%.     

Effects of reaction and cure temperatures on morphology and properties of poly(ester‐urethane)

Poly(ester‐urethane) was synthesized from poly(ethylene glycol adipate) (PEG) and 2,4‐toluene diisocyanate (TDI) to study the effects of reaction temperature and cure temperature on the crystallization behavior, morphology, and mechanical properties of the semicrystalline polyurethane (PU). PEG as soft segment was first reacted with TDI as hard segment at 90, 100, and 110°C, respectively, to obtain three kinds of PU prepolymers, coded as PEPU‐90, PEPU‐100, and PEPU‐110. Then the PU prepolymers were crosslinked by 1,1,1‐tris (hydroxylmethyl) propane (TMP) and were cured at 18, 25, 40, 60, and 80°C. Their structure and properties were characterized by attenuated total reflection Fourier transform infrared, wide‐angle X‐ray diffraction, scanning electron microscopy, dynamic mechanical analysis, and tensile testing. With an increase of the reaction temperature from 90 to 100°C, the crystallinity degree of soft segment decreased, but interaction between soft and hard segments enhanced, leading to the increase of the glass transition temperature (T_g) of soft domain and tensile strength. When the cure temperature was above 60°C, miscibility between soft and hard segments of the PEPU films was improved, resulting in relatively low crystallinity and elongation at break, but high soft segment T_g and tensile strength. On the whole, all of the PEPU‐90, PEPU‐100, and PEPU‐110 films cured above 60°C possessed higher tensile strength and elongation at break than that of the films cured at other temperatures. The results revealed that the reaction temperature and cure temperature play an important role in the improvement of the crosslinking structure and mechanical properties of the semicrystalline PU. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 708–714, 2006     

Micromorphology and mechanism of polyurethane/polyacrylate membranes modified with epoxide group

Polyurethane/polyacrylate (PUA) composite emulsions were synthesized based on the presence of preformed polyurethane chains. Glycidyl methacrylate (GMA), an acrylate monomer, was introduced into the system. Surface tension measurements assured the surface activities of the polyurethane emulsion. Dynamic light scattering (DLS) result showed that the average diameters and polydispersity were increased with the increment of GMA content. X-ray photoelectron spectroscopy (XPS) result indicated that the upper surface was rich in PU phase. The peak deconvolution results of XPS also confirmed the formation of PUA. The crosslinking degree and tensile strength were both enhanced due to the reaction between the carboxyl groups and the epoxide groups. Thermo gravimetric analysis (TGA) of the membranes showed that the thermal stability enhanced and the decomposition temperature was much higher than the pure PU membrane. X-ray diffraction (XRD) analysis, together with differential scanning calorimetry (DSC) results, demonstrated the amorphous nature of the PU matrix. Atomic force microscopy (AFM) observation performed the extremely flat membrane.     

New approach for preparation of dry natural rubber nanocomposites through acid‐free co‐coagulation: Effect of organoclay content

Natural rubber (NR) vulcanizates exhibit good mechanical properties compared to vulcanizates of synthetic rubbers. Incorporation of a conventional filler at higher loadings to NR enhances its modulus, while reduction in tensile strength and elongation. This paper presents a new strategy for development of a NR‐clay nanocomposite with enhanced mechanical properties by incorporation of lower loadings (2–8 phr) of cetyl trimethyl ammonium bromide modified montmorillonite clay (OMMT‐C) under acid‐free environment. The effect of OMMT‐C loading on cure characteristics, rubber‐filler interactions, crosslink density, dynamic mechanical thermal properties, and mechanical properties were evaluated. Incorporation of OMMT‐C accelerated the vulcanization process and enhanced mechanical properties. X‐ray diffraction analysis and scanning electron microscopy images revealed that the formation of intercalated clay structures at lower OMMT‐C loadings, and clay aggregates at higher loadings. A nanocomposite at OMMT‐C loading of 2 phr exhibited the best balanced mechanical properties, and was associated with highest crosslink density and rubber–filler interactions. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46502.     

Structure and properties of semiinterpenetrating polymer networks based on polyurethane and nitrochitosan

Two semiinterpenetrating polymer networks (semi‐IPNs) based on trihydroxyl methylpropane–polyurethane (T‐PU) or castor oil–polyurethane (C‐PU) were prepared by curing the mixed solution of the polyurethane prepolymer and nitrochitosan (NCH). During the curing process, crosslinking and grafting reaction between the molecules of the PU prepolymer and NCH occurred, because of the high reactivity of remaining hydroxyl groups in the NCH with ? NCO groups of PU. The structure of the original semi‐IPN sheets and the sheets treated with acetone were studied by infrared, ¹³C‐NMR, scanning electron microscopy, and dynamic mechanical analysis, showing interpenetration of NCH molecules into the PU networks. When nitrochitosan content (C_NCH) was lower than 10 wt %, the semi‐IPN sheets T‐PU and C‐PU had higher density and tensile strength (σ_b) than the systems with C_NCH more than 20%. The trihydroxymethyl propane‐based PU reacted more readily with nitrochitosan to form the semi‐IPNs than castor oil‐based PU. The semi‐IPN coatings T‐PU and C‐PU were used to coat cellophane, resulting in intimate interfacial bonding. The mechanical strength and water resistivity of the cellophane coated with T‐PU coating were improved remarkably. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3109–3117, 2001     

甲基丙烯酸缩水甘油酯对大豆蛋白塑料改性作用研究

用模压的方法制备了甲基丙烯酸缩水甘油酯(GMA)改性大豆分离蛋白质(SPI)塑料。表征了GMA改性SPI塑料的力学性能、耐水性,并分析了GMA与SPI之间的相互作用。结果表明GMA在模压过程中,环氧基与蛋白质分子间发生接枝和交联反应,同时自聚,在GMA含量较低时可以同时对SPI塑料起到增强和增塑作用,但是随着GMA含量增加,交联作用增强,塑料的断裂伸长率下降。     

Study of nanoreinforced shape memory polymers processed by casting and extrusion

Multi‐walled carbon nanotubes (CNTs) and cellulose nanofibers (CNFs) reinforced shape memory polyurethane (PU) composite fibers and films have been fabricated via extrusion and casting methods. Cellulose nanofibers were obtained through acid hydrolysis of microcrystalline cellulose. This treatment aided in achieving stable suspensions of cellulose crystals in dimethylformamide (DMF), for subsequent incorporation into the shape memory matrix. CNTs were covalent functionalized with carboxyl groups (CNT‐COOH) and 4,4′‐methylenebis (phenylisocyanate) (MDI) (CNT‐MDI) to improve the dispersion efficiency between the CNT and the polyurethane. Significant improvement in tensile modulus and strength were achieved by incorporating both fillers up to 1 wt% without sacrificing the elongation at break. Electron microscopy was used to investigate the degree of dispersion and fracture surfaces of the composite fibers and films. The effects of the filler (type and concentration) on the degree of crystallinity and thermal properties of the hard and soft segments that form the PU sample were studied by calorimetry. Overall, results indicated that the homogeneous dispersion of nanotubes and cellulose throughout the PU matrix and the strong interfacial adhesion between nanotubes and/or cellulose and the matrix are responsible for the enhancement of mechanical and shape memory properties of the composites. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Semi‐interpenetrating networks based on poly(N‐isopropyl acrylamide) and poly(N‐vinylpyrrolidone)

Three series of novel semi‐interpenetrating polymer networks, based on crosslinked poly(N‐isopropylacrylamide), PNIPA, and different amounts of the linear poly(N‐vinylpyrrolidone), PVP, were synthesized to improve the mechanical properties and thermal response of PNIPA gels. The effect of the incorporation of the linear PVP into the temperature responsive networks on the temperature‐induced transition, swelling/deswelling behavior, and mechanical properties was studied. Polymer networks with four different crosslinking densities were prepared with varying molar ratios (25/1 to 100/1) of the monomer (N‐isopropylacrylamide) to the crosslinker (N,N′‐methylenebisacrylamide). The hydrogels were characterized by determination of the equilibrium degree of swelling, the dynamic shear modulus and the effective crosslinking density, as well as tensile strength and elongation at break. Furthermore, the deswelling kinetics of the hydrogels was studied by measuring their water retention capacity. The inclusion of the linear hydrophilic PVP in the PNIPA networks increased the equilibrium degree of swelling. The tensile strength of the semi‐interpenetrating networks (SIPNs) reinforced with linear PVP was higher than that of the PNIPA networks. The elongation at break of these SIPNs varied between 22% and 55%, which are 22 – 41% larger than those for pure PNIPA networks. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

High‐molecular‐weight polyurethanes prepared by one‐step miniemulsion polymerization

Through one‐step miniemulsion polymerization, hydrophobic polyurethane (PU) dispersions were prepared, with hexadecane (HD) as costabilizer in the oil phase and sodium dodecyl sulfate (SDS) as surfactant in the water phase. The oil phase, including isophorone diisocyanate, poly(oxytetramethylene) glycol, a costabilizer HD, a chain extender 1,4‐butanediol, a crosslinking agent trimethylol propane, and a catalyst dibutyltin dilaurate (SnDBL), was dispersed in the water phase containing SDS. The influences of experimental parameters, such as SnDBL, NCO/OH equivalents, and concentrations of surfactant, were discussed. The particle size and the molecular weight of PU polymer were measured by light scattering and gel permeation chromatography, respectively. With the addition of SnDBL and higher NCO/OH ratio, PU films with higher molecular weights were produced. The chemical structure of the PU polymer was identified by Fourier transform infrared spectrometer, and the adsorption of urethane group was observed. Thermal gravimetric analysis was used to characterize the thermal stability of PU. Furthermore, mechanical property was also investigated and characterized by tensile strength and elongation at break. With a higher NCO/OH ratio and the existence of SnDBL, the tensile strength of PU films was significantly increased. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008