Curing of silylated polyurethane with BF3‐monoethylamine complex as moisture‐curable adhesives and their properties

Boron trifluoride monoethylamine complex (BF₃‐MEA) was evaluated as one of the curing catalyst, for the moisture‐curable adhesive based on the polyurethane end‐capped with trimethoxysilane (silylated polyurethane). BF₃‐MEA worked as the catalyst of condensation reaction of trimethoxysilyl groups in silylated polyurethane to give the corresponding networked polymer. The curing speed, the bond strength, and the heat resistance of the crosslinked adhesives with BF₃‐MEA were compared with dibutyltin dimethoxide. It was found that BF₃‐MEA was a good curing catalyst, which showed the same performance in the bond strength and remarkable advantages in the curing speed and the heat resistance, compared with organotin compound. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Bamboo tar‐based polyurethane wood coatings

Bamboo tar is a natural resource of aromatic polyol obtained from a residue of by setting or distilling crude bamboo vinegar. In this study, the two‐packed polyurethane (PU) coatings were prepared by blending bamboo tar and castor oil varying with different weight ratios and polymeric toluene diisocyanate (PTDI) was used as a hardener at the NCO/OH molar ratio of 1.0. Six kinds of PU coatings were formulated and the viscosity, pot‐life, drying time, mechanical properties (hardness, tensile strength, impact resistance, adhesion, and abrasion resistance), gel content, durability, lightfastness, FTIR, thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA) were characterized. The results indicated that the bamboo tar containing PU film appearance is semitransparent yellow‐brown color and the wood texture could be kept after finishing. All PU films possessed excellent adhesion as well as durability. The increase in bamboo tar content led to shorten drying time of coatings and to increase in hardness, tensile strength, lightfastness, and thermal stability of films. From these results and due to a light smell flavor, it is suggested that the bamboo tar‐based PU coatings is suitable to be used as an exterior wood coatings. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effects of artificial weathering on the mechanical properties of paper‐based materials consolidated with polymeric materials

The study of polymer behavior over time represents the crucial stage in the setup of innovative methodologies for paper restoration. In this research, a series of laboratory simulations by accelerated aging and characterization tests by chemical and physical measurements were carried out on paper samples consolidated both by grafting polymerization with acrylic copolymers and by coating with waterborne polyurethanes with the aim of determining their harmlessness and long‐term effectiveness. In this way, our purpose was not only to verify possible risks for the paper materials but also to determine the advantages and potentialities of new restoration methods through an appropriate and essential working plan of investigations. From our evaluation, both the selected consolidation methods appeared unsuitable to be used in paper restoration because of the damage that they could cause on the paper materials because of their limited durability over time. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

A novel alkoxysilane‐modified high solids hydroxyl acrylic polyurethane: Preparation and surface properties

Alkoxysilane‐modified high solids hydroxyl acrylic polyurethane was prepared by solution polymerization. Its structure, surface, and thermal properties were investigated by ¹H NMR, device of contact angle, thermo gravimetric analysis (TGA), atomic force microscopy (AFM), and X‐ray photoelectron spectroscopy (XPS). Research showed that alkoxysilane modified high solids hydroxyl acrylic polyurethane has superior properties that can be used for automotive paints. The contents of silicone in the alkoxysilane‐modified high solids hydroxyl acrylic polyurethane were 1.25, 1.5, 2, and 2.5 wt %. In this study, γ‐methacryloxypropyltrimethoxysilane (MPTS) was chosen as the modifier. Results showed that the contact angles of water and surface roughness on the film of MPTS modified high solids hydroxyl acrylic polyurethane increased, and thermal stability of the film at high temperatures improved with the increasing of the silicone content in the resins. MPTS modified high solids hydroxyl acrylic polyurethane with 2.5 wt % silicone content had better water resistance, better acid resistance, higher hardness, and excellent weatherability. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1866–1871, 2006     

Linking of oligoesters hydrolysis to polyurethane coatings

The hydrolytic stability of a series of oligoesters comprised of three and four different monomers was evaluated. The hydroxyl terminal oligoesters were prepared from adipic acid (AA) and isophthalic acid (IPA), with six different diols and one triol, which included: 1,4‐butanediol, 1,5‐pentanediol, 1,6‐hexanediol, neopentyl glycol, 2‐methyl‐1,3‐propanediol, trimethylolpropane, and 2‐butene‐1,4‐diol. The hydroxyl terminated oligoesters were reacted with phenyl isocyanate to form telechelic urethane groups. Hydrolysis rate constants were obtained from plots of acid number vs. time. It was observed that ternary oligoester systems had lower hydrolysis rates than quaternary systems. In addition to investigating the hydrolytic stability of the synthesized oligoesters, polyurethane coatings were produced by reacting the hydroxyl‐terminated oligoesters with an aliphatic polyisocyanate (1,6‐hexanediisocyanate trimer). Model oliogester hydrolysis was then correlated to the weatherability of a crosslinked polyurethane film. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40198.     

Effect of nanosilica on the properties of polyester‐based polyurethane

Polyester‐based polyurethanes with embedded nanosilica particles were prepared. The viscosity of polyester resins without and with nanosilica was determined by rheoviscometry. The morphology and mechanical and optical properties of the polyurethane coatings were studied intensively with a transmission electron microscope, a pendulum hardness tester, a scanning probe microscope, an Instron testing machine, an abrader and an ultraviolet–visible spectrophotometer. The viscosity of the polyester resins increased as the nanosilica content increased. Nanosilica could basically be dispersed into the polyester and its polyurethane on a nanoscale. The addition of a small amount of nanosilica increased the hardness, abrasion resistance, and tensile properties of the polymer films. However, these mechanical properties could be worsened at higher nanosilica contents. The ultraviolet–visible spectra showed that the absorbance and reflection of ultraviolet–visible light by the polyurethane films increased as the nano‐SiO₂ content increased, especially at wavelengths of 290–400 nm. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 189–193, 2003     

Effect of oleic acid content and chemical crosslinking on the properties of palm oil‐based polyurethane coatings

Polyurethanes (PU) were prepared by reacting palm oil‐based polyols and aromatic diisocyanate (toluene 2, 4 diisocyanates). The content of oleic acid was varied in the polyester polyols and the hydroxyl value was fixed to be 140 mg KOH g^?1. The NCO/OH ratios were varied to 1.2, 1.4, and 1.6. Crosslinking density of the PU was measured by swelling in toluene at room temperature. It was found that the crosslinking increased with decreasing oleic acid content and increasing NCO/OH ratio. The samples were assessed by thermogravimetric analysis, differential scanning calorimetric, and short‐term creep measurements. The highest rupture strength of the PU films was 36 MPa and thermostability improved as the oleic acid content and the NCO/OH ratios were increased in the sample. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Preparation and surface properties of silicone-modified polyester-based polyurethane coats

A series of novel silicone-modified polyesters (SPE) were prepared by substituting part of diol with low molecular weight hydroxyl-terminated poly(dimenthylsiloxane) (PDMS). Then, isophorone diisoclanate (IPDI) as hard segments and 1,4-butanediol as chain extender were added to SPE to prepare a silicone-modified polyurethane (SPU). The effects of the type of diol, diacid, and hydroxyl-terminated PDMS, and the amount of hydroxyl-terminated PDMS on the preparation and surface properties of SPU were investigated. It was found that the amount of PDMS incorporated into a polyester chain was relatively higher when 1,6-hexanediol (HDO) and 1,10-decandiol (DDO) were used as diol and the PDMS with lower molecular weight was used as organosilicone compound. Consequently, the SPU coats with HDO as diol, adipic acid (AA) as diacid, and short chain PDMS as silicone segment had the lowest surface-free energy since it had the highest and most homogeneous distribution of silicone segments at its top layer surfaces.     

Synthesis and characterization of polyurethane urea based on fluorine‐containing bisphenoxydiamine

A fluorine‐containing bisphenoxydiamine, 2,2‐bis[4‐(4‐aminophenoxy)phenyl]hexafluoropropane (BAPF₆P), was synthesized and characterized by means of Fourier transform infrared spectrometry (FTIR), NMR, and elemental analysis. The obtained BAPF₆P was used as a chain extender to prepare polyurethane urea (PUU), whose morphology and properties were measured through FTIR, differential scanning calorimetry, thermogravimetric analysis, tensile measurements, and atomic force microscopy. The results show that the PUU elastomers based on BAPF₆P exhibited good mechanical properties and thermal stability. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1863–1869, 2006     

Mechanical properties of crosslinked polyurethane elastomers based on well‐defined prepolymers

This article presents research findings for selected mechanical properties of polyurethane elastomers. The studied elastomers were synthesized with the prepolymer‐based method with the use of controlled molecular weight distribution (MWD) urethane oligomers and with the classical single‐stage method. Prepolymers with defined MWDs were obtained with the use of a multistage method, that is, step‐by‐step polyaddition. To produce elastomers, isocyanate oligomers were then crosslinked with triethanolamine, whereas hydroxyl oligomers were crosslinked with 4,4′,4′′‐triphenylmethane triisocyanate (Desmodur RE). The tensile strength of the obtained elastomers ranged from 1.0 to 7.0 MPa, the ultimate elongation approached 1700%, the Shore A hardness varied from 40 to 93°, and the abrasion resistance index fell within 15–140. The effects of the types of raw materials used, the chemical structures, the production methods, and the supermolecular structures on the mechanical properties of the obtained polyurethane elastomers were examined. When the obtained findings were generalized, it was concluded that the structural changes in the polyurethanes, which were favorable for intermolecular interactions, improved the tensile strength, hardness, and abrasion resistance of the materials and impaired their ultimate elongation at the same time. More orderly supermolecular structures and, therefore, superior mechanical properties were found for polyurethane elastomers produced with the prepolymer method. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of difunctional acids on the physicochemical,thermal, and mechanical properties of polyester polyol‐based polyurethane coatings

Polyester polyol (PP)‐based polyurethanes (PUs) consisting of two difunctional acids [1,4‐cyclohexanedicarboxylic acid (CHDA) and 1,6‐adipic acid (AA)] and also two diols [1,4‐cyclohexanedimethanol (CHDM) and 1,6‐hexanediol (HDO)] were synthesized by a two‐step procedure with a variable feed ratio of CHDA to AA but fixed ratio of CHDM and HDO. The prepared PPs and/or PUs were characterized by Fourier transform infrared spectroscopy, X‐ray diffraction spectroscopy, and atomic force microscopy. The effects of difunctional acids on the thermal, mechanical, and dynamic mechanical thermal properties of PPs or PU films were investigated by thermogravimetry analysis, differential thermogravimetry and dynamic mechanical thermal analysis. The results show that PP exhibits a lowest viscosity with the mole fraction of CHDA and AA at 3 : 7 whereas it delivers a lowest melting point with the mole fraction at 9 : 1. After PPs being cross‐linked by isocyanate trimers, the impact resistance, shear strength and glass transition temperature increase the mixed‐acid formulations with increasing the content of CHDA. In detail, the resultant PU almost simultaneously exhibits the best mechanical and thermal properties when the mole fraction of CHDA and AA is kept constant at 9 : 1, thus giving rise to a high glass transition temperature of 56.4°C and a onset decomposition temperature of 350°C, and also delivering a balanced toughness and hardness with an impact resistance of 100 J/g and storage modulus as high as 10⁹ Pa. This path for synthesis of PP‐based PU provides a design tool for high performance polymer coatings. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41246.     

Thermal stability of chemically crosslinked moisture‐cured polyurethane coatings

Polyurethane prepolymers are widely used in reactive hot melt adhesives and moisture‐cured coatings. The segmented moisture‐cured formulations, based on polytetramethylene glycol (PTMG‐1000)/trimethylol propane (TMP)/isophorone diisocyanate (IPDI) and PTMG/TMP/toluene diisocyanate (TDI), were prepared with NCO/OH ratio of 1.6 : 1.0. The excess isocyanate groups of the prepolymers were chain extended in the ratio of 2 : 1 (NCO/OH) with different aliphatic diols and 4 : 1 with different aromatic diamines. The surplus isocyanate groups of the formulations were completely reacted with atmospheric moisture, and the thermal stability of the postcured materials obtained as cast films were evaluated by thermogravimetric (TG) analysis. It was observed that initial degradation temperatures were above 270°C, with two‐ or three‐step degradation profiles. The degradation parameters were evaluated using the Broido and Coats–Redfern methods. The thermal resistance of moisture‐cured formulations using diisocyanates with the cycloaliphatic structures (IPDI) and the aromatic TDI, at the same NCO/OH ratio (1.6), and TMP content were compared from the isothermal TG experiments at different temperatures and dynamic TG experiments at different heating rates in nitrogen and oxygen environments. The observation suggests that polyurethane‐containing sulfone groups and straight‐chain diol chain extenders were more stable. It was also observed that at lower temperature polyurethane, prepared from aliphatic diisocyanates (IPDI), was more stable than the aromatic diisocyanate (TDI) containing polyurethanes. At high temperature, the stability order follows the reverse trend. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1509–1518, 2005     

Effect of microphase‐separation promoters on the shape‐memory behavior of polyurethane

A series of segmented polyurethanes (PUs) with novel thermosensitive shape‐memory behavior were synthesized via the in situ addition of a small amount of 1‐octadecanol (ODO) to a PU system. For comparison, liquid paraffin (LP) modified PUs were also synthesized. The effects of a small amount of ODO or LP on the PU suprastructure and the thermosensitive shape‐memory properties were studied with X‐ray diffraction, differential scanning calorimetry, dynamic mechanical analysis, and shape‐memory studies. The results indicated that the in situ addition of a small amount of ODO (e.g., 0.3 wt %) remarkably promoted microphase separation, facilitating the ordered packing of soft segments and the formation of perfect hard‐segment domains and thus significantly improving the shape‐memory properties. In contrast, LP had less significant influence on the shape‐memory behavior because of the macrophase separation of these nonpolar alkyl chains from the PU system. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:5224–5231, 2006     

Hydrophobic and oil‐resistant coatings based on advanced green polyurethane dispersions

In recent years, there have been significant interests among scientists around the world to design smart coatings that combine the standard desirable mechanical and chemical resistance properties with additional functionalities such as oil and water repellency, hydrophobicity, self‐cleaning and gas barrier properties. In the present research work, advanced aqueous polyurethane dispersion (PUD) systems have been designed and developed using three different types of polyols as soft‐segments. These polyols differ in their chemical structure, functionality, polarity, and interfacial properties. The effects of soy‐based polyol, hydroxy‐terminated perfluoropolyether, and hydroxy‐terminated polydimethylsiloxane—on various mechanical properties of their uncross‐linked and cross‐linked films, and more specifically on their hydrophobicity and oil‐resistance (oleophobicity) have been studied. Hydrophobicity of these coatings has been characterized by their Dynamic Contact Angle measurements and their oleophobicity by n‐octane absorption method. The investigations showed that presence of fluorine and siloxane structures significantly improve the hydrophobicity and oil resistance of these coatings and it is possible to optimize these properties using suitable composition of PUDs. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3874–3884, 2013     

Poly(propylene carbonate) polyurethane self‐polishing coating for marine antifouling application

In this contribution, a series of environmentally friendly thermoplastic poly(propylene carbonate) polyurethane (PPCU) were prepared by two‐step condensation polymerization and used to fabricate antifouling coatings. The poly(propylene carbonate) (PPC) segments served as degradable moieties. Quartz crystal microbalance with dissipation (QCM‐D) measurements revealed that the polyurethane could degrade in the presence of enzyme and the degradation rate increases with the decrease of the molecular weight of the polyurethane. Investigation on the hydrolytic degradation behavior and the release rate test of the antifoulants in artificial seawater also demonstrated that the hydrolysis rate and the release rate increased as the molecular weight decreased, which makes the coating controllable at the hydrolysis rate range of 0.012–0.051 g/(m²d). Marine field tests and algae settlement assay tests revealed that the polyurethane coating possessed antibiofouling ability due to its self‐renewal property and the release of antifoulants. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43667.     

Gloss and degradation of hydroxyl polyacrylic resin/hexamethylene‐1,6‐diisocyanate coatings under ultraviolet and natural‐exposure aging

Reactive coatings of hydroxyl polyacrylic resin (HPAR) with hexamethylene‐1,6‐diisocyanate were carried out under accelerated 313‐nm ultraviolet (UV) aging for 2000 h and under natural exposure in Lhasa, Tibet, for 24 months. With UV irradiation and exposure time, the gloss changes in coatings with HPAR containing 3.0% or less hydroxyl groups decreased exponentially, whereas the gloss decay of coatings with HPAR containing over 4.5% hydroxyl groups decreased linearly. During 254‐nm UV aging, the gloss changes in coatings with HPAR containing 1.4% or less hydroxyl groups decreased as a Gaussian function. The weather resistance of a coating was correlated to the HPAR, UV irradiation, temperature, and humidity. Scanning electron microscopy indicated that there were degradation reactions and that some substance was lost in the matrix polymer during accelerated UV aging; then, uneven surfaces appeared and caused decreased gloss. Accelerated UV aging was faster than natural‐exposure aging, and the aging velocity of 254‐nm UV was 3–5 times faster than that of 313‐nm UV. Through the changes in the gloss, the aging tolerance of a coating could be monitored, and its aging resistance could also be predicted. The dynamic mechanical thermal analysis results showed that the coatings had good properties. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1271–1278, 2007     

Effect of organoclays on the properties of polyurethane/clay nanocomposite coatings

Linear, one‐binding‐site or two‐binding‐site (N⁺) organifiers with two hydroxyl end groups were synthesized, and novel organoclays were prepared through a cation‐exchange reaction between pristine sodium montmorillonite and the synthesized organifiers. After sonication of the as‐prepared organoclay in N,N′‐dimethylformamide for 10 min, the average size of the clay decreased to about 1 μm. The X‐ray diffraction patterns confirmed that the d‐spacing of the silicate layers of the organoclay expanded from 1.1 to about 1.9 nm and the peak intensity decreased with the molecular weight of the organifier increasing. Polyurethane/clay nanocomposites were synthesized by a one‐shot polymerization method. Both intercalated and exfoliated structures of the layered silicates in the polyurethane matrix were observed from transmission electron microscopy micrographs, and the d‐spacing ranged from 4 to 10 nm. The thermal and mechanical properties of the nanocomposite were enhanced by the introduction of the organoclay into the polyurethane matrix. An approximately 40–46°C increase in the onset decomposition temperature, a 200% increase in the tensile strength with a 0.5 wt % clay loading, and a 49% increase in Young's modulus with a 3 wt % clay loading were achieved. The effects of the molecular weight and the number of binding sites of the organifier on the properties of the nanocomposites were also evaluated. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation and properties of UV‐curable fluorinated polyurethane acrylates containing crosslinkable vinyl methacrylate for antifouling coatings

To obtain highly effective antifouling coatings, a series of UV‐curable polyurethane acrylates containing diluents [heptadecafluorodecyl methacrylate (PFA, 6 wt %)/isobornyl acrylate (IBOA, 34 wt %)/methyl methacrylate (MMA, 20‐5 wt %)/vinyl methacrylate (VMA, 0–15 wt %)] were prepared. This study examined the effect of bulky MMA (20‐5 wt %)/crosslinkable VMA (0–15 wt %) weight ratio on the properties of the UV‐curable polyurethane acrylates. The fluorine concentration in UV‐cured film surface increased with increasing VMA content up to 9 wt % and then decreased. The T_gα, transparency, elasticity, and mechanical properties of the UV‐cured film samples increased with increasing VMA content. The water/methylene iodide contact angles and surface tension of samples increased from 107/79 to 121/91° and decreased from 17.8 to 12.7 mN/m with increasing VMA content up to 9 wt % and then decreased/increased, respectively. From these results, it was found that the optimum VMA content was 9 wt % to obtain a high‐performance antifouling coating. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42168.     

Thermal degradation of carboxylate‐based polyurethane anionomers

With the purpose of elucidating the thermal degradation process of carboxylated polyurethane anionomers (PUAs), characterization of PUAs containing potassium and magnesium salts was conducted using thermogravimetry and FTIR spectroscopy. Potassium salt in PUA induced pronounced acceleration on the thermal degradation of urethane linkage in the hard segment as well as ester and carbonate linkages in the soft segment. The absorption bands of ν(N? H), ν(C=O), δ(N? H), ν (C? N), and ν(C? O? C) in FTIR spectra of PUAs recorded as a function of increasing temperature demonstrated abrupt changes around the initial thermal decomposition temperature, making possible comprehensive studies of the thermal degradation process of PUAs. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 573–579, 2006     

New intumescent flame‐retardant agent: Application to polyurethane coatings

The first part of this investigation focused on the synthesis and characterization of a new type of intumescent flame‐retardant (IFR) agent. Four steps were used in the synthesis process. The structure was characterized by FTIR, magic‐angle spinning nuclear magnetic resonance (MAS‐NMR) ¹³C spectroscopy, and elemental analysis. The addition of an IFR agent into polyurethane (PU) varnish led to an improvement in its carbonization and flame‐retardant (FR) properties. The second part focused on the evaluation of such characteristics as FR property, thermal stability of IFR/PU‐based coatings, rheology of IFR/PU‐based coating solutions, and mechanical properties such as hardness, adhesion, and flexibility of IFR/PU‐based dry coating films. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1193–1206, 2004