Effects of poly(methyl methacrylate)‐based low‐profile additives on the properties of cured unsaturated polyester resins. I. Miscibility,curing behavior,and glass‐transition temperatures

The effects of three series of self‐synthesized poly(methyl methacrylate) (PMMA)‐based low‐profile additives (LPAs), including PMMA, poly(methyl methacrylate‐co‐butyl acrylate), and poly(methyl methacrylate‐co‐butyl acrylate‐co‐maleic anhydride), with different chemical structures and MWs on the miscibility, cured‐sample morphology, curing kinetics, and glass‐transition temperatures for styrene (ST)/unsaturated polyester (UP) resin/LPA ternary systems were investigated by group contribution methods, scanning electron microscopy, differential scanning calorimetry (DSC), and dynamic mechanical analysis, respectively. Before curing at room temperature, the degree of phase separation for the ST/UP/LPA systems was generally explainable by the calculated polarity difference per unit volume between the UP resin and LPA. During curing at 110°C, the compatibility of the ST/UP/LPA systems, as revealed by cured‐sample morphology, was judged from the relative magnitude of the DSC peak reaction rate and the broadness of the peak. On the basis of Takayanagi's mechanical models, the effects of LPA on the final cure conversion and the glass‐transition temperature in the major continuous phase of ST‐crosslinked polyester for the ST/UP/LPA systems was also examined. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3369–3387, 2004     

Effects of chemical structure of polyurethane‐based low‐profile additives on the miscibility,curing behavior,volume shrinkage,glass transition temperatures,and mechanical properties for styrene/unsaturated polyester/low‐profile additive ternary systems. I: Miscibility,curing behavior,and volume shrinkage

The effects of chemical structure and molecular weight of three series of thermoplastic polyurethane‐based (PU) low‐profile additives (LPA) on the miscibility of styrene (ST)/unsaturated polyester (UP) resin/LPA ternary systems prior to reaction were investigated by using the Flory‐Huggins theory and group contribution methods. The reaction kinetics during the cure at 110°C and the cured sample morphology were also studied by differential scanning calorimetry (DSC) and scanning electron microscopy (SEM), respectively. The phase‐separation characteristics of ST/UP/LPA systems during the cure, as revealed by the cured‐sample morphology, and the DSC reaction‐rate profile, could be generally predicted by the calculated upper critical solution temperature for the uncured ST/UP/LPA systems. Finally, based on the measurements for volume change and microvoid formation, volume shrinkage characteristics for the cured ST/UP/LPA systems have been explored. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 543–557, 2000     

Effects of poly(vinyl acetate) and poly(vinyl chloride‐co‐vinyl acetate) low‐profile additives on properties of cured unsaturated polyester resins. II. glass‐transition temperatures and mechanical properties

Three series of self‐synthesized poly(vinyl acetate)‐based low‐profile additives (LPAs), including poly(vinyl acetate), poly(vinyl chloride‐co‐vinyl acetate), and poly(vinyl chloride‐co‐vinyl acetate‐co‐maleic anhydride), with different chemical structures and molecular weights were studied. Their effects on the glass‐transition temperatures and mechanical properties for thermoset polymer blends made from styrene, unsaturated polyester, and LPAs were investigated by an integrated approach of the static phase characteristics, cured sample morphology, reaction kinetics, and property measurements. Based on Takayanagi mechanical models, the factors that control the glass‐transition temperature in each phase region of the cured samples and the mechanical properties are discussed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3347–3357, 2003     

Effects of poly(methyl methacrylate)‐based low‐profile additives on the properties of cured unsaturated polyester resins. II. Volume shrinkage characteristics and internal pigmentability

The effects of three series of self‐synthesized poly(methyl methacrylate) (PMMA)‐based low‐profile additives (LPAs), including PMMA, poly(methyl methacrylate‐co‐butyl acrylate), and poly(methyl methacrylate‐co‐butyl acrylate‐co‐maleic anhydride) with different chemical structures and MWs on the volume shrinkage characteristics and internal pigmentability for low‐shrink unsaturated polyester (UP) resins during curing were investigated by an integrated approach of static phase characteristics of the ternary styrene (ST)/UP/LPA system, reaction kinetics, cured‐sample morphology, microvoid formation, and property measurements. The relative volume fraction of microvoids generated during the cure was controlled by the stiffness of the UP resin used, the compatibility of the uncured ST/UP/LPA systems, and the glass‐transition temperature of the LPAs used. On the basis of the Takayanagi mechanical model, the LPA mechanism on volume shrinkage control, which accounted for phase separation and microvoid formation, and factors leading to both a good volume shrinkage control and acceptable internal pigmentability for the molded parts are discussed. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3388–3397, 2004     

Effects of reactive low‐profile additives on the properties of cured unsaturated polyester resins. II. Glass‐transition temperature and mechanical properties

The effects of reactive poly(methyl methacrylate) (PMMA) and poly(vinyl acetate)‐block‐poly(methyl methacrylate) (PVAc‐b‐PMMA) as low‐profile additives (LPAs) on the glass‐transition temperature and mechanical properties of low‐shrink unsaturated polyester resin (UP) were investigated by an integrated approach of determining static phase characteristics, reaction kinetics, cured sample morphology, and property measurements. The factors that, according to Takayanagi mechanical models, control the glass‐transition temperature in each phase region of the cured samples, as identified by both the thermally stimulated currents method and dynamic mechanical analysis, and the mechanical properties are discussed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 867–878, 2006     

Effects of poly(vinyl acetate) and poly(vinyl chloride‐ co‐vinyl acetate) low‐profile additives on properties of cured unsaturated polyester resins. I. Volume shrinkage characteristics and internal pigmentability

Three series of self‐synthesized poly(vinyl acetate)‐based low‐profile additives (LPAs) with different chemical structures and molecular weights, including poly(vinyl acetate), poly(vinyl chloride‐co‐vinyl acetate), and poly(vinyl chloride‐co‐vinyl acetate‐co‐maleic anhydride), were studied. Their effects on the volume shrinkage characteristics and internal pigmentability for low‐shrink unsaturated polyester (UP) resins during cure were investigated. The experimental results were examined with an integrated approach involving measurements of the static phase characteristics of the ternary styrene/UP/LPA system, the reaction kinetics, the cured sample morphology, and microvoid formation by using differential scanning calorimetry, scanning electron microscopy, optical microscopy, and image analysis. Based on the Takayanagi mechanical model, factors leading to both good volume shrinkage control and acceptable internal pigmentability for the molded parts were explored. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3336–3346, 2003     

Effects of crosslinking on thermal and mechanical properties of polyurethanes

The effects of chemical crosslinking on the thermal and dynamic mechanical properties of a polyurethane system were examined. The polyurethanes were prepared from poly(propylene glycol), a diol; trimethylolpropane propoxylate, a triol; and poly(propylene glycol), tolylene 2,4‐diisocyanate terminated, a diisocyanate monomer. The crosslink density was controlled by varying the triol concentration from 10 to 70 mol % and the isocyanate‐to‐hydroxyl (NCO/OH) ratio from 1.0 to 1.3. All the samples had one glass‐transition temperature and no crystalline regions. In addition, there were larger increases in glass‐transition temperature over the range of triol concentrations studied than over the range of NCO/OH ratios studied. For all samples, the Dibenedetto equation relating glass‐transition temperature to extent of crosslinking fit the data very well. Also, samples with higher crosslink densities had much larger elastic moduli for temperatures above the glass‐transition temperature. By assuming the system was a phantom network, approximate crosslink densities for stoichiometric samples were obtained from the dynamic mechanical data and these agreed fairly well with theoretical predictions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 212–223, 2002     

Effects of reactive low‐profile additives on the volume shrinkage and internal pigmentability for low‐temperature cure of unsaturated polyester

The effects of reactive poly(vinyl acetate)‐block‐poly(methyl methacrylate) (PVAc‐b‐PMMA) and poly(vinyl acetate)‐block‐polystyrene (PVAc‐b‐PS) as low‐profile additives (LPA) on the volume shrinkage characteristics and internal pigmentability for low‐shrink unsaturated polyester resins (UP) during the cure at 30°C were investigated. These reactive LPAs, which contained peroxide linkages in their backbones, were synthesized by suspension polymerizations, using polymeric peroxides (PPO) as initiators. Depending on the LPA composition and molecular weight, the reactive LPA could lead to a reduction of cyclization reaction for UP resin during the cure, and would be favorable for the decrease of intrinsic polymerization shrinkage after the cure. The experimental results have been explained by an integrated approach of measurements for the static phase characteristics of the styrene (ST)/UP/LPA system, reaction kinetics, cured sample morphology, and microvoid formation by using differential scanning calorimetry (DSC), scanning electron microscopy (SEM), optical microscopy (OM), and image analysis. Based on the Takayanagi mechanical model, factors leading to both a good volume shrinkage control and acceptable internal pigmentability for the molded parts have been explored. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 967–979, 2006     

Effects of chemical composition and structure of unsaturated polyester resins on the miscibility, cured sample morphology and mechanical properties of styrene/unsaturated polyester/low-profile additive ternary systems: 2. Mechanical properties

The effects of three series of unsaturated polyester (UP) resins with different chemical composition or structure on the mechanical properties of three low-shrink UP resins containing thermoplastic polyurethane, poly(vinyl acetate) and poly(methyl methacrylate) respectively have been investigated by an integrated approach of static phase characteristics–cured sample morphology–reaction conversion–property measurements. The three series of UP resins synthesized include: maleic anhydride (MA)–neopentyl glycol (NPG)–diethylene glycol (DEG) types, with various molar ratios of NPG and DEG; MA–1,2-propylene glycol (PG) types with and without modification by a saturated dibasic aromatic anhydride or acid, such as phthalic anhydride (PA) or isophthalic acid; and MA–PA–PG types modified by a second glycol, such as DEG, 2-methyl-1,3-propanediol or NPG, to partially replace PG. Based on the Takayanagi mechanical models, the effects of glycol ratios, saturated dibasic aromatic acid modification, second glycol modification, C=C unsaturation of UP and molecular weight of UP on the mechanical properties will be discussed.     

Effects of reactive low‐profile additives on the properties of cured unsaturated polyester resins. I. Volume shrinkage and internal pigmentability

The effects of reactive poly(methyl methacrylate) (PMMA) and poly(vinyl acetate)‐block‐PMMA as low‐profile additives (LPAs) on the volume shrinkage characteristics and internal pigmentability for low‐shrink unsaturated polyester (UP) resins during curing at 110°C were investigated. These reactive LPAs, which contained peroxide linkages in their backbones, were synthesized by suspension polymerization with polymeric peroxides as initiators. Depending on the LPA composition and molecular weight, the reactive LPAs led to a considerable volume reduction or even to a volume expansion after the curing of styrene (ST)/UP/LPA ternary systems; this was attributed mainly to the expansion effects of the LPAs on the ST‐crosslinked polyester microgel structures caused by the reduction in the cyclization reaction of the UP resin during curing as well as to the repulsive forces between the chain segments of UP and LPAs within the microgel structures. The experimental results were explained by an integrated approach of measurements for the static phase characteristics of the ST/UP/LPA system, reaction kinetics, cured sample morphology, and microvoid formation with differential scanning calorimetry, scanning electron microscopy, optical microscopy, and image analysis. With the aid of the Takayanagi mechanical model, the factors leading to both a good volume shrinkage control and acceptable internal pigmentability for the molded parts were also explored. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 264–275, 2005     

Toughening of epoxy resin by functional‐terminated polyurethanes and/or semicrystalline polymer powders

Hydroxyl‐, amine‐, and anhydride‐terminated polyurethane (PU) prepolymers, which were synthesized from polyether [poly(tetramethylene glycol)] diol, 4,4′‐diphenylmethane diisocyanate, and a coupling agent, bisphenol‐A (Bis‐A), 4,4′‐diaminodiphenyl sulphone (DDS), or benzophenonetetracarboxylic dianhydride, were used to modify the toughness of Bis‐A diglycidyl ether epoxy resin cured with DDS. Besides the crystalline polymers, poly(butylene terephthalate) (PBT) and poly(hexamethylene adipamide) (nylon 6,6), with particle sizes under 40 μm were employed to further enhance the toughness of PU‐modified epoxy at a low particle content. As shown by the experimental results, the modified resin displayed a significant improvement in fracture energy and also its interfacial shear strength with polyaramid fiber. The hydroxyl‐terminated PU was the most effective among the three prepolymers. The toughening mechanism is discussed based on the morphological and the dynamic mechanical behavior of the modified epoxy resin. Fractography of the specimen observed by the scanning electron microscopy revealed that the modified resin had a two‐phase structure. The fracture properties of PBT‐particle‐filled epoxy were better than those of nylon 6,6‐particle‐filled epoxy. Nevertheless, the toughening effect of these crystalline polymer particles was much less efficient than that of PU modification. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2903–2912, 2001     

Thermal and dynamic mechanical characterization of polyurethane–urea–imide coatings

A series of NCO terminated polyurethane (PU)–imide copolymers were synthesized by a systematic three‐step process and were chain extended with different diol/diamine chain extenders. In the first step, isocyanate terminated PU prepolymers were prepared by reacting soft segments such as polyester (PE) polyols and polyether polyols such as polypropylene glycol (PPG‐1000) with hard segments like 2,4‐tolylene‐diisocyanate (TDI) or isophorone‐diisocyanate (IPDI) with NCO/OH ratio 2:1. In the second step, thermally stable heterocyclic imide ring was incorporated using isocyanate terminated PU prepolymers by reacting with pyromellitic dianhydride (PMDA) in a excess‐NCO:anhydride ratio of 1:0.5. The surplus NCO content after imidization was both moisture cured or partially reacted with chain extender and moisture cured. The films were characterized by thermogravimetric (TG), differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) instruments. The adhesion strength of these coatings on mild steel (MS), copper (Cu), and aluminum (Al) is dependent on the nature of the substrate. The TGA analysis show good thermal stability. The DMTA results show the microphase separation between the different hard and soft segments. Finally, a structure to property correlation was drawn based on the structure of the soft, hard, and chain extender and the observed properties are useful for understanding and design of intelligent coatings. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3158–3167, 2006     

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     

Water‐soluble poly(vinyl alcohol) grafted with propylene oxide and epichlorohydrin: Characterization,mechanical properties,and model reactions

Poly(vinyl alcohol) (PVA) prepared by full hydrolysis of poly(vinyl acetate) was etherified with propylene oxide and epichlorohydrin. The reaction was done in water with sulfuric acid or sodium hydroxide. Previously, model reactions were carried out on propan‐2‐ol, pentan‐3‐ol, and pentan‐2,4‐diol in order to make the NMR characterization of grafted PVA easier. The new materials were also characterized by DSC and mechanical tests. A determination of their solubility in cold water was done as well. Generally, the prepared polymers showed excellent solubility in water at 10°C and a very low glass‐transition temperature. Consequently, the properties of tension, elongation, elasticity, and resistance were improved. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2868–2874, 2001     

Thermal and mechanical properties of multiple‐component aliphatic degradable polyurethanes

Macroscopic thermal and mechanical properties of complex aliphatic polycarbonate‐based polyurethane (PU) films containing degradable ester units in PU backbone were studied by a combination of several experimental techniques. Differential scanning calorimetry (DSC) revealed that the synthesized oligomeric diol (DL‐L) contributes (in addition to polycarbonate diol) to the formation of soft‐segment domains, while the hard‐segment domains are formed from 1,6‐diisocyanatohexane (HDI) and butane‐1,4‐diol (BD). Three main phase transitions were detected by DSC and by dynamic mechanical thermal analysis. Thermogravimetric analysis (TGA) of two‐component PUs showed that the PU made from DL‐L and HDI is the least thermostable product, while the PU made from polycarbonate diol and HDI is the most stable one. The differences in the thermal stability of different four‐component PUs are not important. Tensile properties very sensitively reflect the changes in composition and in microstructure of PU samples; the best tensile properties exhibits the degradable sample containing the equimolar ratio of hydroxyl groups of macrodiol, oligomeric diol DL‐L and butane‐1,4‐diol. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41872.     

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

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

Synthesis and characterization of poly(urethane‐co‐imidine)s having pendent phenyl and benzylidene groups using bisphthalides,bislactones and blocked polyurethane prepolymers

Poly(urethane‐co‐imidine)s were prepared using amine blocked polyurethane (PU) prepolymer. The PU prepolymer was prepared by the reaction of poly(propylene glycol) (PPG₂₀₀₀) and 2,4‐tolylene diisocyanate (TDI) and end capped with N‐methyl aniline. The PU prepolymer was then reacted with bisphthalides and bislactones, until the evolution of carbon dioxide ceased. Polymerization reactions with bispthalides and bislactone took more time than with dianhydrides. Polymers were characterized by FTIR, GPC, TG and DSC analyses. Molecular weights of the poly(urethane‐co‐imidine)s were found to be lower than that of poly(urethane‐co‐imide)s. Compared to poly(urethane‐co‐imide)s all poly(urethane‐co‐imidine)s showed high glass transition temperature and crystallization peak in DSC. The thermal stability of the polyurethanes was found to increase with the introduction of imidine component. © 2001 Society of Chemical Industry     

Synthesis and characterization of new functional poly(urethane‐imide) crosslinked networks

To synthesize new functional poly(urethane‐imide) crosslinked networks, soluble polyimide from 2,2′‐bis(3,4‐dicarboxyphenyl) hexafluoropropane dianhydride, 4,4′‐oxydianiline, and maleic anhydride and polyurethane prepolymer from polycaprolactone diol, tolylene 2,4‐diisocyanate and hydroxyl ethyl acrylate were prepared. Poly(urethane‐imide) thin films were finally prepared by the reaction between maleimide end‐capped soluble polyimide (PI) and acrylate end‐capped polyurethane (PU). The effect of polyurethane content on dielectric constant, residual stress, morphology, thermal property, and mechanical property was studied by FTIR, prism coupler, Thin Film Stress Analyzer (TFSA), XRD, TGA, DMTA, and Nano‐indentation. Dielectric constant of poly(urethane‐imide) thin films (2.39–2.45) was lower than that of pure polyimide (2.46). Especially, poly(urethane‐imide) thin films with 50% of PU showed lower dielectric constant than other poly(urethane‐imide) thin films did. Lower residual stress and slope in cooling curve were achieved in higher PU content. Compared to typical polyurethane, poly(urethane‐imide) thin films exhibited better thermal stability due to the presence of the imide groups. The glass transition temperature, modulus, and hardness decreased with increase in the flexible PU content even though elongation and thermal expansion coefficient increased. Finally, poly(urethane‐imide) thin films with low residual stress and dielectric constant, which are strongly affected by the morphological structure, chain mobility, and modulus, can be suggested to apply for electronic devices by variation of PU. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 113–123, 2006     

Morphology and properties of poly(benzoxazine‐co‐urethane)s based on bisphenol‐S/aniline benzoxazine

Poly(benzoxazine‐co‐urethane) was prepared by melt‐blending bisphenol‐S/aniline‐type benzoxazine (BS‐a) with isocyanate‐terminated polyurethane (PU) prepolymer based on 2,4‐toluene diisocyanate and poly(ethylene glycol), followed by thermally activated polymerization of the blend. The copolymerization reaction between BS‐a and PU prepolymer was monitored using Fourier transform infrared spectroscopy. The morphology, dynamic mechanical properties, and thermal stability of the poly(benzoxazine‐co‐urethane) were studied using scanning electron microscopy, dynamic mechanical analysis, and thermogravimetry. Homogeneous morphology is shown in scanning electron micrographs of the fracture surfaces of poly(benzoxazine‐co‐urethane)s with different urethane weight fractions, and the roughness of the surface increases with urethane content increasing. Correspondingly, a single glass transition temperature (T_g) is shown on the dynamic mechanical analysis curves of the poly(benzoxazine‐co‐urethane)s, and the T_g is higher than that of the polybenzoxazine. With increase in the urethane content, the T_g and water absorption of poly(benzoxazine‐co‐urethane) increase, whereas the storage modulus and thermal stability decrease. POLYM. ENG. SCI., 53:2633–2639, 2013. © 2013 Society of Plastics Engineers     

Synthesis and properties of nanosilica‐reinforced polyurethane for grouting

A polyurethane/nanosilica (PU/SiO₂) hybrid for grouting was prepared in a two‐step polymerization using poly(propylene glycol) diols as the soft segment, toluene 2,4‐diisocyanate (TDI) as the diisocyanate, 3,3′‐dichloro‐4,4′‐diaminodiphenylmethane (MOCA) as the chain extender, and acetone as the solvent. The size and dispersion of nanosilica, the molecular structure, mechanical properties, rheological behavior, thermal performance, and the UV absorbance characteristic of the PU/SiO₂ hybrid were investigated by transmission electron microscopy (TEM), FTIR, mechanical tests, viscometry, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and UV spectroscopy. Nanosilica dispersed homogeneously in the PU matrix. The maximum values of mechanical properties such as tensile strength, elongation break, and adhesive strength showed an addition of nanosilica of about 2 wt %. Resistance to both high and low temperatures was better than with PU. And the UV absorbance of the PU/SiO₂ hybrid increased in the range of 290–330 nm with increasing nanosilica content. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4333–4337, 2006