Terminated Polyurethane Prepolymer Research Articles

Characteristics of Self-Healable Copolymers of Styrene and Eugenol Terminated Polyurethane Prepolymer.

With limited biomass that can be currently utilized as a renewable resource, it is important to develop a method to convert biomass into materials that can replace fossil fuel product. In this paper, eugenol, a bio-based allyl chain-substituted guaiacol, was used to synthesize self-healable copolymers. Eugenol terminated polyurethane prepolymer (ETPU) was synthesized from eugenol and polyurethane prepolymers terminated with isocyanate groups. ETPU contained two allyl groups. Self-healing copolymer networks were obtained by copolymerization of ETPU and styrene monomer via free radical polymerization. Effects of ETPU content on the properties of copolymers were then studied. These copolymers containing ETPU exhibited good thermal stability and mechanical properties. These copolymers showed higher tensile strength and elongation at break than PS. Their maximum tensile strength reached 19 MPa. In addition, these copolymers showed self-healing property at elevated temperature due to the reversible nature of urethane units in ETPU.

Development of biobased polyurethane‐imides from maleinized cottonseed oil and castor oil

An eco‐friendly coating system, which is largely biobased, has been developed from castor and cottonseed oil. Cottonseed oil was functionalized with maleic anhydride by “ene” reaction to give maleinized cottonseed oil (MACSO); the anhydride groups were reacted with isocyanates to yield –NCO terminated polyurethane prepolymer. The prepolymer was further chain extended with hydroxyl groups of castor oil to give polyurethane‐imides (PUIs). The cross‐linked films thus obtained had good mechanical properties, and the imide groups in the backbone improved the corrosion resistance of PUIs as revealed by potentiodynamic polarization study. With increasing content of MACSO, thermal stability, glass transition temperatures (Tg), tensile strength, and corrosion resistance of resulting PUIs significantly increased.

2-Ethy-4-methylimidazole terminated polyurethane prepolymer as functional latent curing agents for epoxy resin crosslinking

Three kinds of 2-ethyl-4-methylimidazole (EMI)-terminated polyurethane prepolymer were prepared through the reaction between diethylene glycol (DEG), polyethylene glycol 400 (PEG-400) and different isocyanates (toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), hexamethylenediisocyanate (HDI)). The storage stability, curing temperature and curing time of diglycidyl ether of bisphenol A (DGEBA) with EMI derivatives have been investigated by viscometer, DSC, and FTIR, respectively. It was proved that DGEBA/EMI derivatives exhibited superior storage stability than that of DGEBA/EMI. And the DGEBA can be effectively cured by the EMI derivatives at 120–140 °C without the generation of harmful species. Moreover, the higher impact strength and lower glass transition temperature (Tg) suggested an improvement of stiffness. The results of tensile test and TGA indicated that the excellent bonding strength with steel and unconspicuous compromise in thermal stability were simultaneously achieved.

Utilizing dextran to improve hemocompatibility of antimicrobial wound dressings with embedded quaternary ammonium salts.

Dextran, a polysaccharide with interfering effects on coagulation hemeostasis was utilized to compensate the hostile effects of quaternary ammonium salts (QAS) embed in the backbone of a wound dressing membrane as an antimicrobial agent. Despite the high antimicrobial efficiency of QAS, their adverse hemolytic effect on red blood cells is a challenging problem for using them as an active antiseptic agent in wound dressings. To this end, wound dressings made through the sol-gel hydrolysis and polycondensation reaction of a methoxysilane-functionalized quaternary ammonium compound (Si-RQ) and a methoxysilane terminated polyurethane prepolymer (Si-PPU), at different compositions, were surface modified with dextran. The final dressings were then subjected to various biological and physico-mechanical assays. The low hemolysis rate and prolonged clot formation on dextran-modified dressings confirmed their excellent hemocompatibility. Meanwhile, the optimized dressings preserved their excellent antimicrobial activity against both Gram-positive and Gram-negative bacteria and a fungal strain up to 100% killing efficiency. In addition, they exhibited very good cytocompatibility since the fibroblast cells could grow and proliferate efficiently on their surface. The recorded results confirmed the effectiveness of surface anchored dextran for regulation of hemocompatibility of QAS containing wound dressings without deterioration of their basic physical and biological properties.

Preparation and characteristics of poly(benzoxazine-urethane)/graphene oxide composites: Toughness, mechanical and thermal properties

ABSTRACTPoly(benzoxazine-urethane)/graphene oxide [poly(Bz-PU)/GO] composites were successfully prepared by blending benzoxazine (Bz) with graphene oxide (GO) and isocyanato (NCO)-terminated polyurethane prepolymer (PU), followed by thermally activated polymerization of the blends. The network was formed via the mutual reaction and intermolecular interaction among the hydroxyl of GO, NCO groups of PU and phenolic hydroxyl of Bz. The toughness shown from SEM images and tensile properties of polybenzoxazine (PBz) plastic composites can effectively be improved by alloying with PU and GO. The onset curing temperature and exothermic peak maximums of the polymerization obtained from differential scanning calorimetry decreased resulted from the GO addition. The thermogravimetric analysis showed that the incorporation of 0.5 wt% of GO slightly improved the thermal stability of poly(Bz-PU)/GO composites. Additionally, the storage modulus improved and the glass transition temperature (Tg) increased gradually as the increasing GO content not beyond a certain amount. Finally, the exothermic peaks of the polymerization were shifted to lower temperature, and the thermal stability increased for the ternary composites as the number average molecular weights (Mn) of polyol decreased.

EFFECT OF INCREASING NCO/OH MOLAR RATIO ON THE CHEMICAL AND MECHANICAL PROPERTIES OF ISOCYANATE TERMINATED POLYURETHANE PREPOLYMER DERIVED FROM BIO-MASS

The study deals the effect of increasing NCO/OH molar ratio on the physico-mechanical properties of isocyanate terminated polyurethane prepolymer. The prepolymer was prepared using castor oil and toluene-2,4-diisocyanate. The NCO/OH molar ratio has been varied from 1.6 to 2.0. The formation of the prepolymer was confirmed by UV and FTIR spectroscopy. The results reveal that the curing time of the prepolymer decreased with increase in NCO/OH molar ratio. When NCO/OH molar ratio increased, the tensile strength of the polyurethane film increased, while percent elongation decreased due to increase in hard segment content.

On the strategies for incorporating nanosilica aqueous dispersion in the synthesis of waterborne polyurethane/silica nanocomposites: Effects on morphology and properties

In this work the synthesis of waterborne polyurethane/nanosilica nanocomposites by using two different strategies is presented, starting from a vinyl terminated polyurethane prepolymer (PUP) based on isophorone diisocyanate and polypropylene glycol, and varying the nanosilica content. In one case, the PUP was dispersed in an aqueous solution containing glycerol-functionalized colloidal nanosilica particles and the dispersion was further polymerized; in the other case, the PUP was dispersed in an aqueous media, then colloidal nanosilica was added to the dispersion and then polymerized. A physical mixture was also prepared for comparative purpose. Films were prepared by casting of the aqueous dispersion. The morphology of the dispersions and films depended on the incorporation route of nanoparticles as was observed by SAXS, SEM and TEM. While the blends had significantly less hydrogen bonding between the hard segments of the PU and nanosilica particles, samples prepared by the two different methods proposed in this work showed an strong interaction between both materials in agreement with FTIR and DSC results. Synthesis pathway plays an important role in order to obtain high performance waterborne polyurethane/nanosilica composites, since final properties of the films also depended on the nanoparticle incorporation strategy.

Effect of increasing NCO/OH molar ratio on the physicomechanical and thermal properties of isocyanate terminated polyurethane prepolymer

The study investigates the effect of increasing NCO/OH molar ratio on the physico-mechanical and thermal properties of isocyanate terminated polyurethane prepolymer. The prepolymer was prepared using methylene diphenyl diisocyanate and difunctional polypropylene glycol. The NCO/OH molar ratio has been varied from 1.2:1 to 3:1. The formation of the prepolymer was confirmed by FTIR spectroscopy. The results reveal that the viscosity, weight average molecular weight and curing time of the prepolymer decreased with increase in NCO/OH molar ratio. When NCO/OH molar ratio increased, the tensile strength of the polyurethane film increased, while percent elongation decreased due to increase in hard segment content. The glass transition temperature of the prepolymer decreased with increase in NCO/ OH molar ratio of the prepolymer. Keywords : Polyurethane Prepolymer, Viscosity, Molecular Weight, Curing Time, Glass Transition Temperature.

Ionic polyurethane materials for enhanced platelets adhesion and biocompatibility

Polyurethane ionomers (PUI) are employing as one of the prominent materials in the field of biomedical applications. PUI materials have been synthesized from the reaction of poly(ethylene glycol) (PEG) with diisocyanate reagent followed by the addition of dihydroxyl benzoic acid (DHBA) salt by two-step polymerization process. PUI material generated from NCO terminated polyurethane prepolymers bonded with ionomer fragment exhibit bio and haemocompatibility. All of these PUI films were characterized by FTIR and FT-NMR for structural identifications. Study of molecular weights and size analysis of PUI obtained were determined by Gel permeation chromatography and particle size analysis. Essentially, haemocompatibile nature of these PUI have been studied by thrombogenicity, haemolysis and platelet adhesion test. As such polyurethane linked with ionomer fragment exhibits better platelets adherence to soft or biological tissue.

EFFECT OF SOFT SEGMENT CHAIN LENGTH ON TAILORING THE PROPERTIES OF ISOCYANATE TERMINATED POLYURETHANE PREPOLYMER, A BASE MATERIAL FOR POLYURETHANE BANDAGE”

Isocyanate terminated polyurethane prepolymer, a ba se material for water curable polyurethane bandage was prepared from diphenylmethane diisocyanate and poly (propylene ox ide) glycol. In polyurethanes, the diisocyanate ac t as hard segment and provides dimensional stability, whereas the polyol which forms the soft segment gives elastomeric char acter. Due to its segmented structure, polyurethane’s with a wide range of phys ico-mechanical properties can be obtained by varyin g its monomers types and content. In this paper, the effect of different soft segment length on influencing the structure prop erty relationship of polyurethane prepolymer was studied. The soft segment length was varied by using poly (propylene oxide) glycol havi ng different molecular weight and also by blending two polyols having similar che mical composition but of different molecular weight . The formation of the prepolymer was investigated by Fourier transform in frared spectroscopy (FTIR). The results reveal that with increasing soft segment length, the weight average molecular weight and sto rage time of the prepolymer increases, whereas the Brookfield viscosity decreases due to higher content of soft segment. The curing time was found higher in prepolymer having longer s oft segments due to lower isocyanate content. With increasing molecular weigh t of the soft segment, the phase separation between the hard and soft segment increases due to which the prepolymer produce low T g. The tensile strength of the polyurethane film dec reases whereas percent elongation increases with increase in soft segment length. The findings of the study will be beneficia l for understanding the role played by soft segment length on tailoring the stru cture and ultimately the properties of isocyanate t erminated polyurethane prepolymer.

Synthesis and characterization of triazole rich polyether polyols using click chemistry for highly branched polyurethanes

The present work describes development of moisture cured polyurethane–urea coatings based on 1,2,3-triazole rich polyether polyols. In this paper, two polyether polyols were synthesized by using 1,3-dipolar azide–alkyne cycloaddition reaction and they were named as PL-1 and PL-2 where PL-1 is 9 terminal hydroxyl groups and PL-2 is 6 terminal hydroxyl groups. These polyols were reacted with 4, 4′-diisocyanatodicyclohexylmethane (H12MDI) at OH:NCO ratio of 1:1.2 in order to obtain isocyanate terminated polyurethane prepolymers. The resulted prepolymers were casted on tin foil and cured under atmospheric moisture in order to get completely cured polyurethane–urea free films. The free films were characterized by using Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and dynamic mechanical thermal analysis (DMTA) techniques. The TGA and DMTA results showed that these films have good thermal and mechanical stability. Anti-microbial studies proved that these polyurethane films show good resistance towards different bacterial and fungal attacks. These polymers were also coated on mild steel panels in order to evaluate corrosion resistance properties by using salt spray and electro chemical polarization studies.

Waterborne hybrid polymer particles: Tuning of the adhesive performance by controlling the hybrid microstructure

Hybrid polyurethane/acrylic waterborne pressure sensitive adhesives were synthesized by miniemulsion polymerization. The free radical polymerization of a mixture of acrylic and methacrylic monomers, containing 2-hydroxyethyl methacrylate, was carried out in the presence of a diisocyanate terminated polyurethane prepolymer and a diol. The resulting polymer microstructure was varied by altering the PU content and the number of links between the PU and the acrylic chains. The structure of the hybrid polymer was characterized by a combination of macroscopic measurements (gel fraction, swelling ratio, and sol molecular weight distribution) and computer simulations. A detailed study of the relationship between structure and adhesive properties was carried out.

아크릴 단량체 종류 변화가 수분산 Polyurethane Dispersion의 물성에 미치는 영향

Isophorone diisocyanate(IPDI), polycarbonate diol(PCD), dimethylol propionic acid(DMPA)를 출발물질로 하여 NCO terminated prepolymer가 합성되었다. 이 prepolymer의 NCO기를 아크릴 단량체로 capping하기 위해 다양한 아크릴 단량체인 2-hydroxyethyl methacrylate(HEMA), 2-hydroxyethyl acrylate(HEA), pentaerythritol triacrylate(PETA)가 첨가되었다. 제조된 용액의 평균 입경은 아크릴 단량체가 첨가되면서 증가하였다. 또한 제조된 코팅 막의 연필경도 및 내마모성은 순수한 수분산 폴리우레탄보다 우수하였으며, 아크릴 단량체 중에서 PETA가 가장 우수한 물성을 보였다. NCO terminated polyurethane prepolymers were synthesized from isophorone diisocyanate(IPDI), polycarbonate diol(PCD) and dimethylol propionic acid(DMPA). Subsequently, acrylic terminated polyurethanes were prepared by capping the NCO groups of polyurethane prepolymers with different types of acrylate monomers, such as 2-hydroxyethyl methacrylate(HEMA), 2-hydroxyethyl acrylate(HEA) and pentaerythritol triacrylate(PETA). The average particle sizes of the acrylic terminated polyurethane solutions were increased by capping acrylate monomers. Also, the prepared coating films showed better abrasion resistance and pencil hardness than those of pure waterborne polyurethanes. The coating film with PETA exhibited the best abrasion resistance and pencil hardness of coating films prepared with three acrylate monomers.

Modification of cellulosic fiber with polyurethane acrylate copolymers. Part I: Physicochemical properties.

Polyurethane (PU) prepolymers were prepared by using two different diisocyanates i.e., toluene-2,4-diisocyanate (TDI) and or isophorone diisocyanate (IPDI), and poly (2-methyl-1,3-propylene glutarate), hydroxyl terminated group. PU prepolymer was reacted with 2-hydroxyethylacrylate (HEA) to form vinyl terminated PU prepolymer. Vinyl terminated PU prepolymers were further copolymerized with butyl acrylates (BuA) by emulsion process. The structure of proposed PUACs samples was confirmed by FT-IR, and their physicochemical properties were studied determining solid contents (%), emulsion stability and its appearance, tackiness and film appearance. Their acids and base chemical resistance was also studied and discussed. The synthesized PUACs samples were applied using dip-padding techniques on mill un-desized poly-cotton plain weave fabrics. The results emphasis that PUACs based on toluene-2,4-diisocyanate (TDI) have shown excellent performance against physical and chemical resistance as compared to isophorone diisocyanate (IPDI) based PUACs, however vice versa results were found in some studies.

수분산 폴리우레탄의 물성에 미치는 Pentaerythritol Triacrylate의 첨가 효과

Isophorone diisocyanate(IPDI), polycarbonate diol(PCD), dimethylol propionic acid(DMPA)를 출발물질로 하여 NCO terminated prepolymer가 합성되었다. 이 prepolymer의 NCO기를 아크릴 단량체로 capping하기 위해 0~0.024 mole로 첨가량이 조절된 pentaerythritol triacrylate (PETA)가 첨가되었다. 제조된 acrylic terminated polyurethane 용액의 평균입경은 PETA의 첨가량이 증가함에 따라 증가하였다. 또한 제조된 코팅 필름의 연필경도 및 내마모성은 순수한 수분산 폴리우레탄보다 우수하였다. NCO terminated polyurethane prepolymers were synthesized from isophorone diisocyanate(IPDI), polycarbonate diol(PCD) and dimethylol propionic acid(DMPA). Subsequently, acrylic terminated prepolymers were prepared by capping the NCO groups of polyurethane prepolymers with different moles of pentaerythritol triacrylate (0~0.024 moles) as a acrylate monomer. The average particle size of the acrylic terminated polyurethane solutions was increased with increasing PETA contents. Also, the prepared coating films showed better abrasion resistance and pencil hardness than pure waterborne polyurethane.

실란커플링제 종류 변화가 수분산 폴리우레탄의 특성에 미치는 영향

NCO terminated polyurethane prepolymers were synthesized from isophorone diisocyanate(IPDI), poly (tetramethylene glycol)(PTMG) and dimethylol propionic acid(DMPA). Subsequently, waterborne polyurethanes were prepared by capping the NCO groups of polyurethane prepolymers with different types of silane coupling agents, such as methyltrimethoxysilane(MTMS), glycidoxypropyl trimethoxysilane(GPTMS), methacryloxypropyl trimethoxysilane (MPTMS) and aminopropyl triethoxysilane(APS). The average particle size of the waterborne polyurethane solutions was increased by adding silane coupling agents. Also, the coating films prepared from GPTMS, MPTMS and APS, exhibited better pencil hardness than those from pure waterborne polyurethane. On the other hand, the coating films from MTMS did not show an improved pencil hardness than those from pure waterborne polyurethane.

Improvement of performance behavior of cellulosic fiber with polyurethane acrylate copolymers

Polyurethane acrylate (PUA) copolymers were synthesized following three step synthesis using toluene-2,4-diisocyanate, poly (2-methyl-1,3-propylene glutarate) diol terminated, 2-hydroxyethylacrylate (HEA) and butyl acrylate (BuA) via emulsion polymerization technique. The conventional spectroscopic characterization of the samples with FT-IR was in accordance with proposed PUA copolymer structure. The synthesized PUA copolymer samples were applied using dip-padding techniques on mill desized, scoured, bleached, printed, 100% cotton combed satin, striped weave fabrics. The emulsion stability evaluation and pilling rating showed reciprocal dependence on the percentage of butyl acrylate (BuA) and dual dependence on the concentration of vinyl terminated polyurethane prepolymer. The results revealed that by decreasing the mole ratio of polyol the emulsion stability and pilling rating drastically increased.

Effect of nano ZnO on the phase mixing of polyurethane hybrid dispersions

In the present study series of aqueous polyurethane (PU)/ZnO hybrid dispersions were prepared using dimethylolpropionic acid (bis-MPA) as an ionic center. For this, NCO terminated PU prepolymers with pendent acid groups were prepared first, then different concentrations of nano ZnO powder was incorporated into the PU matrix. The hybrid dispersions were prepared by adding required amount of triethylamine (TEA), water and chain extender. The prepared PU/ZnO hybrid dispersions were casted in a Teflon petri dish and the dried films were used for TGA, DMTA, SEM, gel content and contact angle measurements. The phase mixing behavior was studied from FT-IR peak deconvolution technique and DMTA analysis and the result suggests that phase mixing increases with ZnO content. The DMTA data suggest that the phase mixing and soft segment glass transition increases but storage modulus decreases with increasing with ZnO content. The FT-IR deconvolution result supports to the DMTA analysis. The coating properties like adhesive strength, water absorption, contact angle, gel content and corrosion resistance of the hybrid coatings were also evaluated.

Synthesis and properties of poly(urethane‐imide) diacid/epoxy composites cured with an aziridine system

AbstractA poly(urethane‐imide) diacid (PUI), a diimide‐diacid with a soft structure unit, was directly synthesized from the reaction of trimellitic anhydride and isocyanate terminated polyurethane prepolymer. FT‐IR and NMR were used to characterize its chemical structure. Then PUI was blended with two types of epoxy resins with different chemical structures, diglycidyl ether of bisphenol A (DGEBA) and novolac epoxy (EPN). After curing the blends with polyfunctional aziridine CX‐100, novel polyurethane/epoxy composites were obtained as transparent yellowish films. Thermal, chemical, and morphological properties of the cured composites were investigated using thermal analysis, SEM, TEM, chemical resistance, respectively. All experimental data indicated that epoxy modified PUI composites possessed higher thermal stability than that unmodified PUI, and that modified PUI had much better chemical resistance. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Effect of isocyanate structure on deblocking and cure reaction of N-methylaniline-blocked diisocyanates and polyisocyanates

Two series of N-methylaniline-blocked isocyanates based on monomeric diisocyanates such as 4,4′-methylene bis(phenyl isocyanate), toluene-2,4-diisocyanate, isophorone diisocyanate and 1,6-diisocyanato hexane and their NCO terminated polyurethane prepolymer (polyisocyanates) were prepared and characterized thoroughly by FTIR, 1H NMR, 13C NMR and EI-Mass spectroscopic methods. The blocking reaction of N-methylaniline with aromatic isocyanates and aromatic polyisocyanates occur faster when compared to the aliphatic isocyanates. The deblocking reactions of blocked isocyanates were carried out under dynamic and isothermal conditions using hot-stage FTIR spectrophotometer. The dynamic method was used to determine the deblocking temperature, and the isothermal method was used to calculate kinetics and thermodynamics parameters. Cure reactions of blocked isocyanates with hydroxyl-terminated polybutadiene were also followed to establish the structure–property relationship of the N-methylaniline-blocked isocyanates. The deblocking studies of blocked isocyanates reveal that the aromatic isocyanates undergo deblocking easily compared to aliphatic isocyanates. The rate of deblocking reaction of N-methylaniline-blocked aromatic polyisocyanates was found to be higher compared to N-methylaniline-blocked aromatic monomeric diisocyanate adducts. On the other hand, this trend was just reverse in the cure-reaction studies. The dissolution behavior of N-methylaniline-blocked isocyanates in Terathane-2000, polypropylene glycol-2000, polycaprolactone diol-2000 and hydroxyl-terminated polybutadiene-2500 was also studied and found that all adducts are soluble in these polyols.