Synthesis of anionic water‐borne polyurethane with the covalent bond of a reactive dye

We successfully synthesized an anionic water‐borne polyurethane (PU) capable of reacting with a reactive dye to form a covalent bond with the dye molecule. The anionic water‐borne PU was synthesized and grafted with the reactive dye to form a dyed PU. First, the PU prepolymer was synthesized from 4,4′‐methylene bis(isocyanatocyclohexane), poly(tetramethylene glycol), 2,2′‐bis(hydroxymethyl) propionic acid (as an anionic center), and triethyleneamide (as a neutralizer). Then, pure water was added to emulsify and disperse the prepolymer to form an anionic water‐borne PU prepolymer. Finally, the extender N‐(2‐hydroxyethyl) ethylene diamine was used to extend the anionic water‐borne prepolymer to form a PU polymer with hydroxyl groups that could further react with the reactive dye molecule. With respect to the heating properties, the dyed PU polymers exhibited higher glass‐transition temperatures of the hard segment than those without dye molecules. However, neither the glass‐transition temperature of the soft segment nor the melting temperature of the soft segment varied in the presence of dye molecules, but they were changed with various chain lengths of the soft segment. As for the mechanical properties, the modulus and strength of the dyed PU polymers decreased because of the bulkiness of their dye molecules, but the breaking elongation increased. Moreover, the inherent viscosity decreased in the presence of the dye molecules. As for the dyeing properties, the percentage of dye grafting was greater than 90%. The dye‐grafted PU exhibited a lower percentage of migration than PU extended with ethylene diamine (without hydroxy groups) and also showed a higher grade of colorfastness to light. © 2002 John Wiley & Sons, Inc. J Appl Polym Sci 84: 797–805, 2002; DOI 10.1002/app.10336     

A novel synthesis of reactive nano‐clay polyurethane and its physical and dyeing properties

This study is about polyurea prepolymer, which was synthesized from the extender (N‐(2‐hydroxyethyl) ethylene diamine, HEDA or ethylene diamine, EDA) with 4,4′‐diphenylmethane diisocyanate (MDI), as an intercalative agent to intercalate the organic modified montmorillonite clay. Then, it is further reacted with the polyurethane prepolymer, which is polymerized from the polytetramethylene glycol (PTMG) and MDI, to proceed the intercalative polymerization to form a polyurethane/clay nanocomposite polymer. The experimental parameters contain the use of polyurea intercalative prepolymer extender and also the contents of organo‐clay in the prepolymer etc. We expect to get better mechanical property and also to improve the dyeing properties of nano‐clay polyurethane. The polyurethane/clay polymer is synthesized using two‐step method: synthesizing the polyurethane prepolymer from PTMG and MDI and then extended with the polyurea prepolymer modified with the organo‐clay. Because the extender HEDA contains side chain of hydroxyl groups, the modified PU can further react with the reactive dye. From the experimental results of the fine structure (X‐ray and FT‐IR) and mechanical analysis, it is found that the intercalation is successfully achieved. Thedistance of interlayer spacing is manifestly enlarged. The mechanical properties are significantly improved as the content of organo‐clay is increased. Besides, although thedye up‐take is decreased with the increasing content oforgano‐clay, but the water‐resistant fastness is improved. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Poly(urea-urethane) polymers with multi-functional properties

Polyurea-urethanes with multifunctional properties were synthesized by reacting 4,4′-diphenylmethane disocyanate (MDI) with a two diol mixture of polytetramethylene glycol (PTMG (1000, 2000) and biocidal quaternary ammonium monomer ((N-benzyl-N-dodecyl-N-bis2-hydroxyethyl) ammonium chloride (BDAC)), and extended with N-(2-hydroxyethyl) ethylene diamine (HEDA) to form PU polymers. The PU polymer was then grafted with a disperse dye via a coupling agent of epichlorohydrin to form a dye grafted polyurethane with biocidal and covalent bond dyeing properties. In consideration of the mechanical properties, it is found that both the modulus and the strength of the dye grafted PU polymer films are lower than those of pure PU polymers due to the bulkiness of their dye molecules. For thermal properties, the dye grafted PU polymers exhibit higher T_gh than those without dye molecules. However,neither the T_gs nor the T_ms vary in the presence of BDAC or dye molecules, but they are changed with various chain lengths of the soft segment. For dyeing properties, the effective dyeing efficiency of dye grafted PU is over 85%. Moreover, the dye grafted PU polymers exhibit lower dye migration (M_p%) than those of simple mixtures of PU and dyestuff, and they show a higher grade of color fastness when exposed to light. In the shake method of antibacterial testing, the modified PU polymers exhibit a long lasting biocidal activity.     

Alkali reduction and reactive dye dyeing of T/N nonwoven fabrics dipped into silicon‐containing,water‐borne polyurethane

Two series of anionic water‐borne polyurethanes with alkali resistance and covalent bonds of a reactive dye were synthesized with different molar ratios of poly(tetramethylene glycol) (PTMG). They were classified with respect to PTMG 1000 and PTMG 2000. The fiber blends of polyester/nylon nonwoven fabrics were dipped into silicon‐containing, water‐borne polyurethane and squeezed to an 80% pickup ratio. Finally, the manmade leather was treated with alkali reduction and dyed with a reactive dye. The alkali reduction and the thermal, mechanical, and dyeing properties of the manmade leather were studied. For alkali reduction, different ratios of NaOH and Na₂CO₃ concentrations were used. Na₂CO₃ was used because of its better spreading and buffering properties. The softness and breaking load were measured and related to the weight reduction. For the dyeing properties, a reactive dye with vinyl sulfone groups was found to bond with the OH group of water‐borne polyurethane by covalent bonding. On the basis of alkali reduction, a mixture of NaOH and Na₂CO₃ with a concentration ratio of 0.1N/0.2N could lead to better softness and alkali reduction of leather. For the mechanical properties, leather of the PTMG 1000 series showed a higher breaking load than leather of the PTMG 2000 series. However, less elongation in the PTMG 1000 series resulted. Differential scanning calorimetry showed an endothermic peak at 50–100°C. This indicated that the glass‐transition temperature of the hard segment decreased with an increasing amount of the soft segment in leather; meanwhile, both the glass‐transition temperature of the soft segment and the melting temperature of the hard segment also decreased as the content of the soft segment increased. For the dyeing properties, the reactive blue dye could reach up to 96.1% dye uptake in the polyurethane part of the leather. Moreover, the washing fastness could be graded as high as 4–5, and the light resistance was also graded to 4–5, in the dyed leather. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2324–2335, 2005     

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.     

Curing reaction of amino‐terminated aqueous‐based polyurethane dispersions with triglycidyl‐containing compound

Amino‐terminated anionic aqueous‐based polyurethane (PU) dispersion was obtained from NCO‐terminated PU prepolymer, which was neutralized with an excess triethylamine (TEA) and chain extended by ethylenediamine (EDA) during water dispersion process. That PU prepolymer was obtained from a polyaddition reaction of isophorone diisocyanate (IPDI), polypropylene glycol‐2000 (PPG‐2000), and 2,2′‐dimethylol propanoic acid (DMPA). This aqueous‐based PU dispersion was treated with trimethylolpropane triglycidyl ether (TMPTGE) as a latent curing agent and resulted in a self‐cured PU resin on drying. A model ring‐opening curing reaction between oxirane group of TMPTGE with terminal amino group of PU was demonstrated by glycidol with n‐butyl amine. The physical and mechanical properties as well as thermogravimetric analyses of these self‐cured PU resins were evaluated in this article. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis,thermal properties,and morphology of blocked polyurethane/epoxy full‐interpenetrating polymer network

Blocked polyurethane (PU)/epoxy full‐interpenetrating polymer network (full‐IPN) were synthesized from blocked NCO‐terminated PU prepolymer, with 4,4‐methylene diamine as a chain extender and epoxy prepolymer, with 4,4‐methylene diamine as a curing agent, using simultaneous polymerization (SIN) method. From FTIR spectra analysis it was found that the major reactions in the blocked PU/epoxy IPN system are the self‐polymerization of block PU/chain extender and the self‐polymerization of epoxy/curing agent. Meanwhile, from reaction mechanisms the copolymerization of IPN may have occurred at the same time. The weight loss by thermogravimetric analysis decreased with increasing epoxy and filler content. It was confirmed from scanning electron micrography (SEM) that when the blocked PU content increased, the microstructure of IPN became rougher. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 323–328, 2006     

Curing and combustion properties of a PU‐coating system with UV‐reactive phosphazene

A UV‐curable polyurethane (PU)‐coating system containing phosphorus is formulated by the combination of photoinitiator, PU acrylate oligomer, and UV‐reactive phosphazene monomer. PU acrylate oligomer is prepared by the addition of 2‐hydroxyethylmethacrylate (HEMA) to NCO‐terminated PU prepolymer. UV‐reactive phosphazene monomer is derived from the HEMA substitution reaction to hexachlorocyclotriphosphazene (NPCl₂)₃. The curing reaction of this PU‐coating system is carried out by UV irradiation. The resultant UV‐cured PU‐coated films demonstrated better performance properties than those of original UV‐cured PU acrylate (UV‐PU) without UV‐reactive phosphazene monomer. Furthermore, their thermal properties are investigated by a thermogravimetric analyzer and a dynamic mechanical thermal analyzer, respectively. The combustion behaviors of these UV‐cured PU‐coated films are evaluated by the measurements of a limiting oxygen index and a cone calorimeter. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1980–1991, 2002     

High‐performance waterborne coatings based on epoxy‐acrylic‐graft‐copolymer‐modified polyurethane dispersions

Polyurethane dispersions (PUDs) have been an active area of research since the early 1940s because of legislative restrictions on the use of organic solvents in conventional solvent‐based products and also because PUDs exhibit almost the same high performance levels as solvent‐borne polyurethanes. In the present study, properties of conventional waterborne PUDs are modified with epoxy‐acrylic graft copolymer blocks. The epoxy‐acrylic graft copolymers were first modified with ethylene diamine to give amine‐terminated blocks which in turn reacted with isocyanate‐terminated prepolymer (prepolymer mixing process) to give modified PUDs. Several experimental sets were prepared with varying compositions. The experimental sets were also prepared using conventional poly(ethylene glycol) blocks and ethylene diamine chain‐extenders. The physico‐chemical properties and film characteristics of the experimental sets show the dramatic improvement in important mechanical properties of PUDs due to grafting with epoxy‐acrylic copolymer blocks. Copyright © 2004 Society of Chemical Industry     

Possibilities of polymer‐aided dyeing of cotton fabric with reactive dyes at neutral pH

Water‐soluble polymers have versatile application, viz., water‐soluble polyacrylates have been widely used in the reactive dyeing of cellulosic fibers and the related soaping as an important component of the leveling and washing agent. In this article, one such water‐soluble polymer, polyacrylic acid has been synthesized, characterized, and applied in conjunction with various types of reactive dyes, namely triazinyl, vinyl sulfone, high exhaustion, and bifunctional reactive dyes, along with crosslinking agents, namely glycerol 1,3‐dichlorohydrin and hexamethylene tetramine‐hydroquinone, respectively. One of the crosslinking agents (the former one) has been synthesized in the laboratory. Crosslinking agent is necessary to adhere the dye molecule onto the cellulose macromolecule. Different process sequences have been formulated and explored for dyeing purpose. All such dyeings were carried out at neutral pH. The dyed samples were assessed through color strength in terms of K/S values and their fastness properties were assessed by standard methods. All such dyeings were compared with conventional dyed samples. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Self‐curable system of an aqueous‐based polyurethane dispersion via a ring‐opening reaction of azetidine end groups

An azetidine (AZT) containing compound, 3‐azetidinyl propanol was synthesized from methyl acrylate with 3‐amino‐1‐propanol in a four‐step reaction. It was introduced into an isocyanate‐terminated carboxylic acid containing polyurethane (PU) prepolymer as the end group. A single‐component, AZT‐terminated self‐curable aqueous‐based PU dispersion was obtained from the water dispersion process after it was neutralized with triethylamine. Its carboxylic groups served not only as the internal emulsifier stabilizing the aqueous PU dispersion but also as PU self‐curing sites toward its AZT end groups via a ring‐opening reaction. The curing reaction took place on drying and resulted in polymeric network structure formation among the polymers. The performance properties of this self‐cured PU were evaluated in this study. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4383–4393, 2006     

Copolymers based on poly(butylene terephthalate) and polycaprolactone‐block‐polydimethylsiloxane‐block‐polycaprolactone

A series of novel thermoplastic elastomers, based on poly(butylene terephthalate) (PBT) and polycaprolactone‐block‐polydimethylsiloxane‐block‐polycaprolactone (PCL‐PDMS‐PCL), with various mass fractions, were synthesized through melt polycondensation. In the synthesis of the poly(ester‐siloxane)s, the PCL blocks served as a compatibilizer for the non‐polar PDMS blocks and the polar comonomers dimethyl terephthalate and 1,4‐butanediol. The introduction of PCL‐PDMS‐PCL soft segments resulted in an improvement of the miscibility of the reaction mixture and therefore in higher molecular weight polymers. The content of hard PBT segments in the polymer chains was varied from 10 to 80 mass%. The degree of crystallinity of the poly(ester‐siloxane)s was determined using differential scanning calorimetry and wide‐angle X‐ray scattering. The introduction of PCL‐PDMS‐PCL soft segments into the polymer main chains reduced the crystallinity of the hard segments and altered related properties such as melting temperature and storage modulus, and also modified the surface properties. The thermal stability of the poly(ester‐siloxane)s was higher than that of the PBT homopolymer. The inclusion of the siloxane prepolymer with terminal PCL into the macromolecular chains increased the molecular weight of the copolymers, the homogeneity of the samples in terms of composition and structure and the thermal stability. It also resulted in mechanical properties which could be tailored. Copyright © 2010 Society of Chemical Industry     

Chemorheology and thermomechanical characteristics of benzoxazine‐urethane copolymers

In this research, processability and some important thermomechanical properties of polybenzoxazine (BA‐a) modified with a highly flexible urethane elastomer (PU) are discussed. This copolymer has been reported to show synergy in its glass transition temperature and some mechanical properties thus provides a fascinating group of high temperature polymers with enhanced flexibility. The results reveal that a processing window of the BA‐a/PU mixtures is widened with the increasing urethane prepolymer fraction, that is, the liquefying temperature is lowered and the gel point shifted to higher temperature with the amount of the PU. Synergism in glass transition temperature (T_g) of this copolymer was clearly confirmed, i.e., T_g's of the BA‐a/PU alloys were significantly greater than those of the parent resins, i.e., BA‐a (T_g = 166°C) and PU (T_g = ? 70°C). In addition, flexural modulus was found to systemically decrease from 5.4 GPa of the neat polybenzoxazine to 2.1 GPa at 40% by weight of the PU. Flexural strength of the alloys also shows a synergistic behavior at the BA‐a/PU ratio of 90/10. Coefficient of thermal expansion of the polymer alloys were also found to show a minimum value at BA‐a/PU = 90/10. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Electrostatic self‐assembly dyeing of cotton fabrics

A new approach to the dyeing of cotton fabrics using an electrostatic self‐assembly method was evaluated. Cotton fabrics were pretreated with 2,3‐epoxypropyltrimethylammonuium chloride and cationic charges were produced on the fabric surfaces. For the dyeing of cotton fabric, reactive and acid dyes were used. Oppositely charged anionic reactive/acid dyes and cationic poly(diallyldimethylammonium chloride) were alternately deposited on the surface of cationised cotton fabrics. Ten multilayer films of dye/poly(diallyldimethylammonium chloride) were deposited on the cotton fabric surfaces using a padder. The build‐up of the multilayer films and the level of colour strength (K/S) achieved are discussed. Samples of cotton fabrics were also dyed with the same dyes, but using the exhaust method, and both types of dyed samples were compared. The washing, rubbing and light fastness properties were evaluated for the dyed fabrics.     

Synthesis and application to cellulose of reactive dye precursor of anti‐bacterial N‐halamine

To achieve textile dyeing and functional finishing in one process, a bleach‐resistant reactive dye precursor to anti‐bacterial N‐halamine was synthesised by reacting a type of dichlorotriazine reactive dye with 4‐amino‐2,2,6,6‐tetramethylpiperidine. The synthesised compound, which can be transformed to an N‐halamine molecule by exposure to dilute bleach solution, was used to dye cotton fabrics. After exposure to a dilute sodium hypochlorite solution, dyed cotton fabrics showed excellent anti‐bacterial properties against Staphylococcus aureus and Escherichia coli O157:H7, facilitating a ca. 6‐log reduction in bacteria within a short period of contact. Compared with the dichlorotriazine reactive dye, the reactive dye precursor demonstrated comparable dyeing properties including exhaustion and fixation values. No differences in rub fastness, wash fastness or bleach fastness were detected between fabrics dyed with, respectively, dichlorotriazine reactive dye and the reactive dye precursor to N‐halamine.     

A molecularly imprinted polymer via a salicylaldiminato‐based cobalt(III) complex: A highly selective solid‐phase extractant for anionic reactive dyes

A novel molecularly imprinted polymer based on tert‐butyl acrylate (MIP‐BA) was fabricated with the assistance of a cobalt(III)‐based catalyst bearing an N‐salicylidene isopropylamine ligand [(SPA)₂CoCl]. After initiation with methyl aluminoxane, the catalyst system was found to be active toward the polymerization of tert‐butyl acrylate (t‐BA) in the presence of a polar template (Cibacron reactive red dye) and divinylbenzene (DVB) as a crosslinker. Polymerization experiments, including those of t‐BA, t‐BA, and DVB and t‐BA and dye, were also carried out. Isolated blank polymers and MIP‐BA were analyzed with a variety of techniques, including differential scanning calorimetry, thermogravimetric analysis, gel permeation chromatography, infrared spectroscopy, nuclear magnetic resonance, and ultraviolet–visible spectroscopy. In general, the complex showed moderate polymerization activity and produced high‐molar‐mass poly(tert‐butyl acrylate); however, a decrease in the monomer conversion was observed upon the addition of the dye and/or the crosslinker. The effect of imprinting was obvious when the adsorption capacity of MIP‐BA measured at pH 6 for red dye (the imprinted molecule) was increased from 9.2 to 90.4 mg/g after imprinting. Competitive adsorption studies revealed that the dye‐imprinted polymer enabled the efficient uptake of red dye, even in the presence of blue and yellow dyes that had similar chemical structures to the imprinted molecule. The selectivity coefficients were 43 and 36 with respect to the blue and yellow dyes, respectively. The proposed polymerization procedure could be extended to other anionic polar reactive dyes and polar reactive polymers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Single component self‐curable aqueous‐based PU system with new aziridinyl curing agent

The self‐emulsified aqueous‐based polyurethane (PU) consists of carboxyl group, which is an ionic center not only stabilizing the aqueous polymer dispersion but also serving as the curing site toward aziridinyl curing agent. Two new aziridinyl curing agents, HDI‐AZ and ADA‐AZ, are prepared from an addition reaction of aziridine to hexamethylene diisocyanate (HDI) and adipic acyl chloride (ADA), respectively. These curing agents are added separately into NCO‐terminated PU prepolymer before or after the water dispersion process. The resulting PU dispersion becomes a single component self‐curable aqueous‐based PU system. The cured PU is obtained from this single component PU dispersion on drying at ambient temperature. The improved PU properties demonstrate the feasibility of this convenient single component self‐curable aqueous‐based PU system. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91:1997–2007, 2004     

Synthesis and properties of polyurethane‐urea‐based liquid bandage materials

To obtain ideal liquid bandage polymer materials, a series of polyurethane‐urea dispersions were synthesized from 4,4′‐diisocyanato dicyclohexylmethane (H₁₂MDI) and ethylene diamine with different molar ratio of polyol blend [polyethylene glycol (PEG, M_n = 2000 g/mol)/hydroxy terminated poly(dimethylsiloxane) (PDMS, M_n = ～ 550 g/mol)] and acetone/ethanol as a solvent. The effect of PDMS content in PEG/PDMS on the viscosity, mechanical properties, water contact angle/surface energy, insolubility in water (%), water absorption (%), equilibrium water content (%), and water vapor transmission rate (g m^?2 day^?1) of polyurethane‐urea films was investigated. As PDMS content increased, the water contact angle, insolubility in water, and tensile strength/elastic recovery of film sample increased; however, the surface energy, water absorption (%), equilibrium water content (%), and water vapor transmission rate (g m^?2 day^?1) of film sample decreased. By a wound‐healing evaluation using a full‐thickness rat model experiment, it was found that a wound covered with a typical polyurethane‐urea liquid bandage film (PD2 sample) was filled with new epithelium without any significant adverse reactions. These results suggest that the polyurethane‐urea‐based liquid bandages (samples: PD2 and PD3) prepared in this study may have high potential as new wound dressing materials, which provide and maintain the adequate wet environment required to prevent scab formation and dehydration of the wound bed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and characterization of polyurethane hybrids: Influence of the polydimethylsiloxane linear chain and silsesquioxane cubic structure on the thermal and mechanical properties of polyurethane hybrids

The structural effects of polydimethylsiloxane (PDMS) or polyhedral oligosilsesquioxanes (POSSs) on the thermomechanical properties of polyurethane (PU) networks were studied. An ester–amine‐functionalized silsesquioxane and a PDMS macromer were synthesized, and the macromer (10 wt %) was crosslinked with the PU prepolymer to obtain PU networks. The synthesized macromers and hybrids were characterized with Fourier transform infrared, ¹H‐NMR, ¹³C‐NMR, and ²⁹Si‐NMR spectroscopy techniques. The influence of POSS cubes on the thermal and mechanical properties of the polymer network films was studied comparatively with the similarly functionalized PDMS linear chain via thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA) measurements. The degradation pattern of the POSS‐incorporated PU nanocomposites was almost the same as that of the PU network synthesized from the linear PDMS macromer. The differences in the char yields and activation energies of the hybrids reflected the enhancement of the thermal properties of the nanohybrids. The TGA and DSC curves of the macromers suggested that the thermal properties of the macromers not only depended on either the PDMS or POSS inorganic core but also depended on the organic peripheral attached to the inorganic core. The glass‐transition temperatures of the nanohybrids were higher than those of the linear‐PDMS‐incorporated hybrids. The storage modulus values increased 3‐fold upon the incorporation of POSS rigid groups into the PU hybrids in comparison with the flexible PDMS‐chain‐incorporated PU hybrids. The DMA measurements showed a long‐range rubbery plateau region for all the PU hybrids, with high storage modulus and tan δ values showing the structural homogeneity of the crosslinked networks. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Polyurethane‐solid wood composites prepared with various catalysts. I. Mechanical properties and dimensional stabilities

Polyurethane (PU)‐solid wood composites were prepared by impregnating PU prepolymer into low‐density fast‐growing poplar solid wood and controlling the prepolymer cured or foamed within wood voids in the presence of the catalysts triethanolamine (TEA), diethylenetriamine (DETA), triethylenediamine (TEDA), and N‐methyl morpholine (NMM), respectively. A scanning electron microscope (SEM) was used to observe the morphologies of the cured PU resin and the wood voids, and the effects of catalyst species on the mechanical properties and dimensional stabilities of PU‐wood composites were evaluated. The results indicated that the PU prepolymer cured in the presence of various catalysts resulted in different morphologies and distributions within wood voids, and therefore led to various mechanical properties and dimensional stabilities of the PU‐wood composites. Because of the fact that wood cell walls in the surface layer had apparently collapsed in the presence of catalyst DETA and therefore the wood was densified, the PU‐wood composite prepared with DETA had the best mechanical properties and dimensional stabilities. The PU prepolymer was well impregnated and evenly foamed within the wood in the presence of catalyst NMM, giving the PU‐wood composite prepared with NMM much better dimensional stability as the foamed PU blocked the water transfer between the cells. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009