Synthesis and characterization of nanocomposites of silicon dioxide and polyurethane and epoxy resin interpenetrating network

Nanocomposites with varying concentrations of nanosized silicon dioxide particles were prepared by adding nanosilica to interpenetrating polymer networks (IPN)s of polyurethane and epoxy resin (PU/EP). The PU/EP IPNs and nanocomposites were studied by dynamic mechanical analysis, scanning electronic microscopy, wide‐angle X‐ray diffraction and small‐angle X‐ray scattering. The result showed that adding nanosize silicon dioxide can improve the properties of compatibility, damping and phase structure of IPN matrices. Copyright © 2003 Society of Chemical Industry     

含有互穿网络结构的丁腈橡胶改性环氧/酚醛胶粘剂的合成及其应用

合成了一种含有互穿网络结构的丁腈橡胶(BN)改性环氧/酚醛胶粘剂。通过扫描电镜(SEM)分析, 证明了此胶片具有互穿网络结构。同时对胶粘剂进行了差热分析(DTA),并考察了其粘结性能以及贮存性能。最后将其成功地应用到一种厚铜箔(0.4～0.5mm)环氧玻璃布层压板上,得到的覆铜板样品具有剥离强度高、平整度好、电性能优良等特点。     

聚氨酯/环氧树脂互穿网络聚合物反应动力学

通过共混法制备了聚氨酯(PU)/环氧树脂(EP)互穿网络聚合物(IPN),采用示差扫描量热法(DSC)和动态机械分析(DMA)对IPN形成过程中的固化反应动力学及产物IPN的相容性进行了研究,结果表明,m(PU)/m(EP)=10∶6的IPN体系的反应级数为0.95,表观活化能为169.23 kJ/mol;PU/EP IPN只有1个玻璃化转变温度,相容性好。     

Toughness response of vinylester/epoxy‐based thermosets of interpenetrating network structure as a function of the epoxy resin formulation: Effects of the cyclohexylene linkage

Vinylester/epoxy (VE/EP)‐based thermosets of interpenetrating network (IPN) structures were produced by using a VE resin (bismethacryloxy derivative of a bisphenol A–type EP resin) with aliphatic (Al‐EP) and cycloaliphatic (Cal‐EP) EP resins. Curing of the EP resins occurred either with an aliphatic (Al‐Am) or cycloaliphatic diamine compound (Cal‐Am). Dynamic mechanical thermal analysis (DMTA) and atomic force microscopy (AFM) suggested the presence of an interpenetrating network (IPN) in the resulting thermosets. Fracture toughness (K_c) and fracture energy (G_c) were used as the toughness characterization parameters of the linear elastic fracture mechanics. Unexpectedly high K_c and G_c data were found for the systems containing cyclohexylene units in the EP network, such as VE/Al‐EP+Cal‐Am and VE/Cal‐EP+Al‐Am. This was attributed to the beneficial effects of the conformational changes of the cyclohexylene linkages (chair/boat), which were closely analogous to those in some thermoplastic copolyesters. The failure mode of the VE/EP thermoset combinations was studied in scanning electron microscopy (SEM) and discussed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2124–2131, 2003     

Mechanical properties of blocked polyurethane/epoxy interpenetrating polymer networks

The mechanical properties of blocked polyurethane(PU)/epoxy interpenetrating polymer networks (IPNs) were studied by means of their static and damping properties. The studies of static mechanical properties of IPNs are based on tensile properties, flexural properties, hardness, and impact method. Results show that the tensile strength, flexural strength, tensile modulus, flexural modulus, and hardness of IPNs decreased with increase in blocked PU content. The impact strength of IPNs increased with increase in blocked PU content. It shows that the tensile strength, flexural strength, tensile modulus, and flexural modulus of IPNs increased with filler (CaCO₃) content to a maximum value at 5, 10, 20, and 25 phr, respectively, and then decreased. The higher the filler content, the greater the hardness of IPNs and the lower the notched Izod impact strength of IPNs. The glass transition temperatures (T_g) of IPNs were shifted inwardly compared with those of blocked PU and epoxy, which indicated that the blocked PU/epoxy IPNs showed excellent compatibility. Meanwhile, the T_g was shifted to a higher temperature with increasing filler (CaCO₃) content. The dynamic storage modulus (E′) of IPNs increased with increase in epoxy and filler content. The higher the blocked PU content, the greater the swelling ratio of IPNs and the lower the density of IPNs. The higher the filler (CaCO₃) content, the greater the density of IPNs, and the lower the swelling ratio of IPNs. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1826–1832, 2006     

Property evaluation and structure analysis of polyurethane/epoxy graft interpenetrating polymer networks

Polyurethanes obtained from 4,4′‐diphenylmethane diisocyanate (MDI) and polydiols with different molecular weights (polyethylene glycol and polyoxypropylene diols) were used as modifiers for diglycidyl ether of bisphenol A. Impact strength (IS), critical stress intensity factor (K_C), flexural strength and flexural strain at break were measured as a function of polyurethane (PUR) type and content. Scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and infrared spectroscopy (FTIR) were employed for the structure and morphology analysis. It was found that the addition of polyurethane with an excess of isocyanate groups to epoxy resin resulted in the formation of a grafted interpenetrating polymer network structure. The mechanical properties of epoxy resin were improved with 5 and 10% PUR. Moreover, it was observed that composites containing PUR based on higher molecular weight (PUR 1002 and PUR 2002) with long flexible segments exhibited higher impact strength while PUR prepared from polyethylene glycol had a higher flexural energy to break and a higher flexural modulus. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Semi‐interpenetrating polymer networks based on polyurethane and polyvinylpyrrolidone. II. Dielectric relaxation and thermal behaviour

Semi‐interpenetrating polymer networks (semi‐IPNs) based on crosslinked polyurethane (PU) and linear polyvinylpyrrolidone (PVP) were synthezised, and their thermal and dynamic mechanical properties and dielectric relaxation behavior were studied to provide insight into their structure, especially according to their composition. The differential scanning calorimetry results showed the glass transitions of the pure components: one glass‐transition temperature (T_g) for PU and two transitions for PVP. Such glass transitions were also present in the semi‐IPNs, whatever their composition. The viscoelastic properties of the semi‐IPNs reflected their thermal behavior; it was shown that the semi‐IPNs presented three distinct dynamic mechanical relaxations related to these three T_g values. Although the temperature position of the PU maximum tan δ of the α‐relaxation was invariable, on the contrary the situation for the two maxima observed for PVP was more complex. Only the maximum of the highest temperature relaxation was shifted to lower temperatures with decreasing PVP content in the semi‐IPNs. In this study, we investigated the molecular mobility of the IPNs by means of dielectric relaxation spectroscopy; six relaxation processes were observed and indexed according the increase in the temperature range: the secondary β‐relaxations related to PU and PVP chains, an α‐relaxation due to the glass–rubber transition of the PU component, two α‐relaxations associated to the glass–rubber transitions of the PVP material, and an ionic conductivity relaxation due to the space charge polarization of PU. The temperature position of the α‐relaxation of PU was invariable in semi‐IPNs, as observed dynamic mechanical analysis measurements. However, the upper α‐relaxation process of PVP shifted to higher temperatures with increasing PVP content in the semi‐IPNs. We concluded that the investigated semi‐IPNs were two‐phase systems with incomplete phase separation and that the content of PVP in the IPNs governed the structure and corresponding properties of such systems through physical interactions. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1191–1201, 2003     

Morphology and thermal and dielectric behavior of cycloaliphatic epoxy/trimethacrylate interpenetrating polymer networks for vacuum‐pressure‐impregnation electrical insulation

Vacuum pressure impregnation has been known as the most advanced impregnation technology that has ever been developed for large and medium high‐voltage electric machines and apparatuses. We developed one new type of vacuum‐pressure‐impregnation resin with excellent properties by means of a novel approach based on in situ sequential interpenetrating polymer networks resulting from the curing of trimethacrylate monomer [trimethylol‐1,1,1‐propane trimethacrylate (TMPTMA)] and cycloaliphatic epoxy resin (CER). In this study, the influence of the concentrations of the components and their microstructures on their thermal and dielectric behaviors were investigated for the cured CER/TMPTMA systems via atomic force microscopy, dynamic mechanical analysis, thermogravimetric analysis, and dielectric analysis. The investigation results show that the addition of TMPTMA to the CER–anhydride system resulted in the formation of a uniform and compact microstructure in the cured epoxy system. This led the cured CER/TMPTMA systems to show much higher moduli in comparison with the pure CER–anhydride system. The thermogravimetric analysis results show that there existed a decreasing tendency in the maximum thermal decomposition rates of the cured CER/TMPTMA systems, which implies that the thermal stability properties improved to some extent. The dielectric analysis results show that the cured CER/TMPTMA systems displayed quite different dielectric behaviors in the wide frequency range 0.01 Hz–1 MHz and in the wide temperature range 27–250°C compared with the cured CER–anhydride system. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis and mechanical properties of leather–epoxy interpenetrating polymer networks

Leather–epoxy interpenetrating polymer networks (IPNs) were synthesized; these IPNs have an approximate epoxy concentration of 25 wt %. The flexural and tensile moduli of the IPNs prepared are equivalent to those of the epoxy resin. The Izod impact energy and fracture toughness measured for the IPNs, however, exceed those attained by the epoxy resin alone by at least a factor of 4. The glass transition of leather–epoxy IPNs occurs over a wide temperature range, thus indicating that the IPN is an intimate admixture of the epoxy resin throughout the collagen matrix of the hide. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1224–1232, 2000     

The effect of composition and the level of crosslinking of the poly(methylmethacrylate) phase on the properties of natural rubber‐poly(methylmethacrylate) semi‐2 interpenetrating polymer networks

The effects of the PMMA content and the cross‐linker level in the poly(methylmethacrylate) component on the dynamic and physico‐mechanical properties of semi‐2 interpenetrating polymer networks based on natural rubber and poly(methylmethacrylate) were determined. The miscibility of the components in these semi‐2 interpenetrating polymer networks was determined using the loss tangent data, obtained from dynamic mechanical thermal analysis and the interphase contents were calculated from modulated scanning calorimetric data. Some component mixing in these semi‐2 interpenetrating polymer networks was evident from these modulated differential scanning calorimetric and dynamic mechanical thermal analysis data. The degree of component mixing increased with cross‐linker level in the PMMA phase. The PMMA content in the semi‐2 IPNs has a significant effect on the tensile and hysteresis behavior of these semi‐2 interpenetrating polymer networks. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Reinforcement of polyurethane/epoxy interpenetrating network nanocomposites with an organically modified palygorskite

An organophilic palygorskite (o‐PGS) prepared by the treatment of natural palygorskite with hexadecyl trimethyl ammonium bromide was incorporated into interpenetrating polymer networks (IPNs) of polyurethane (PU) and epoxy resin (EP), and a series of PU/EP/clay nanocomposites were obtained by a sequential polymeric technique and compression‐molding method. X‐ray diffraction and scanning electron microscopy analysis showed that adding nanosize o‐PGS could promote the compatibility and phase structure of PU/EP IPN matrices. Tensile testing and thermal analysis proved that the mechanical and thermal properties of the PU/EP IPN nanocomposites were superior to those of the pure PU/EP IPN. This was attributed to the special fibrillar structure of palygorskite and the synergistic effect between o‐PGS and the IPN matrices. In addition, the swelling behavior studies indicated that the crosslink density of PU/EP IPN gradually increased with increasing o‐PGS content. The reason may be that o‐PGS made the chains more rigid and dense. As for the flame retardancy, the PU/EP nanocomposites had a higher limiting oxygen index than the pure PU. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

混合大二醇基聚氨酯弹性体/环氧树脂互穿网络聚合物的研究

以α,ω-双(γ-羟丙基)聚二甲基硅氧烷(BHPDMS)和聚氧四甲基二醇(PHMO)混合大二醇作为软链段,首先通过两步溶液聚合法合成了-NCO封端的混合大二醇基聚氨酯(PU)弹性体预聚物(PUT);然后以PUT和环氧树脂(EP)预聚物为原料、1,3-双(γ-氨丙基)-1,1,3,3-四甲基二硅氧烷(BATS)为交联剂,采用同步溶液聚合法合成了PUT/EP互穿聚合物网络(PUT/EP I PN)。使用傅里叶红外光谱(FT-I R)法、动力学分析(DMA)法和扫描电子显微镜(SEM)法,对PUT和PUT/EP I PN进行分析和表征,并对其力学性能和表面疏水性进行测试。实验结果表明,PUT/EP I PN中不存在宏观相分离状态,仅发生微观相分离状态;当PUT/EP I PN中w(PUT)=50%时,PUT/EP I PN具有优异的综合力学性能和表面疏水性。     

Effect of the synthesis route on the structure and properties of polyurethane/nitrokonjac glucomannan semi‐interpenetrating polymer networks

With a synthesis route differing from previous methods, novel semi‐interpenetrating polymer networks (semi‐IPNs), coded UNK‐II, were synthesized by the initial mixing of nitrokonjac glucomannan (NKGM) with castor oil in butanone and the subsequent addition of toluene diisocyanate (TDI) to begin the polymerization reaction in the presence of 1,4‐butanediol (BD) as a chain extender at 60°C. The results from dynamic mechanical analysis, differential scanning calorimetry, and ultraviolet spectroscopy indicated that a certain degree of microphase separation occurred between soft and hard segments of polyurethane (PU) in the UNK‐II sheets. The α‐transition temperature, glass‐transition temperature, heating capacity, and tensile strength increased with an increase in the NKGM content, and this suggested an interaction between PU and NKGM in the UNK‐II sheets. In a previous method, semi‐IPN materials (PUNK) were synthesized by the polymerization reaction between castor oil and TDI, and then this PU prepolymer was mixed with NKGM and cured in the presence of BD as a chain extender. The PUNK sheets had relatively good miscibility and mechanical properties. However, for UNK‐II sheets prepared by the method reported in this work, NKGM mainly played a role in reinforcement. When the NKGM content was less than 10%, the UNK‐II sheets exhibited good miscibility, tensile strength (26–28 MPa), and breaking elongation (130–140%), similar to those of PUNK materials. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1948–1954, 2003     

Thermal characteristics of interpenetrating polymer networks composed of poly(vinyl alcohol) and poly(N‐isopropylacrylamide)

Interpenetrating polymer networks (IPNs) composed of poly(vinyl alcohol) (PVA) and poly(N‐isopropylacrylamide) (PNIPAAm) were prepared by the sequential‐IPN method. The thermal characterization of the IPNs was investigated using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dielectric analysis (DEA). Depression of the melting temperature (T_m) of the PVA segment in IPNs was observed with increasing PNIPAAm content using DSC. DEA was employed to ascertain the glass‐transition temperature (T_g) of IPNs. From the result of DEA, IPNs exhibited two T_g values, indicating the presence of phase separation in the IPNs. The thermal decomposition of IPNs was investigated using TGA and appeared at near 200°C. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 881–885, 2003     

Structure–property relationships in acrylate/epoxy interpenetrating polymer networks: Effects of the reaction sequence and composition

Interpenetrating polymer networks (IPNs) of poly(ethylene glycol) 200 diacrylate and diglycidyl ether of bisphenol A were formed over a range of compositions and with different reaction sequences. We controlled the reaction sequence by thermally initiating the cationic epoxy polymerization, photoinitiating the free‐radical acrylate polymerization, and changing the processing order. The reaction was monitored by attenuated total reflectance Fourier transform infrared spectroscopy, photo differential scanning calorimetry. and modulated differential scanning calorimetry (mDSC). The glass‐transition temperature was estimated from mDSC. Mechanical and rheological tests provided the strength and hardness of the materials. Morphology and phase separation were explored with optical and scanning electron microscopy. All of the physical properties were dependent on IPN composition. Some properties and the morphology were dependent on the reaction sequence. Significant differences in glass‐transition temperature were observed at the same composition but with different reaction sequences. Even with minimal structure, correlations existed between the morphology and material properties with partially phase‐separated samples exhibiting maximum damping. The rapid reaction allowed minimal phase separation, yet different reaction sequences resulted in significantly different properties. This systematic study indicated that the relationships between phase morphology, processing, and the physical properties of IPNs are complex and not predictable a priori. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 891–901, 2007     

Modification of novolac resin by interpenetrating network formation with poly(butyl acrylate)

Interpenetrating networks (IPNs) of novolac (phenol formaldehyde) resin and poly(butyl acrylate) (PBA) were prepared by a sequential mode of polymerization. Both full IPNs and semi‐IPNs of different compositions were synthesized and characterized with respect to their mechanical properties, that is, their modulus, ultimate tensile strength (UTS), elongation‐at‐break percentage, and toughness. Their thermal properties were examined with differential scanning calorimetry and thermogravimetric analysis (TGA). A morphological study was performed with an optical microscope. The effects of the variation of the blend ratios on the aforementioned properties were studied. There was a gradual decrease in the modulus and UTS with a simultaneous increase in the elongation‐at‐break percentage and toughness for both types of IPNs as the proportions of PBA were increased. With increasing proportions of PBA, the glass‐transition temperatures of the different IPNs underwent shifts toward a lower temperature region. This showed a plasticizing influence of PBA on the rigid and brittle phenolic matrix. TGA thermograms depicted the classical two‐step degradation for the phenolic resin. Although there was an apparent increase in the thermal stability at the initial stage (up to 350°C), particularly at lower temperatures, a substantial decrease in the thermal stability was observed at higher temperatures under study. In all the micrographs of full IPNs and semi‐IPNs, two‐phase structures were observed, regardless of the PBA content. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2407–2417, 2005     

Synthesis,characterization and properties of organoclay‐modified polyurethane/epoxy interpenetrating polymer network nanocomposites

organoclay‐modified polyurethane/epoxy interpenetrating network nanocomposites (oM‐PU/EP nanocomposites) were prepared by adding organophilic montmorillonite (oMMT) to interpenetrating polymer networks (IPNs) of polyurethane and epoxy resin (PU/EP) which had been prepared by a sequential polymerization technique. Wide‐angle X‐ray diffraction (WAXD) and transmission electronic microscopy (TEM) analysis showed that the interpenetrating process of PU and EP improved the exfoliation and dispersion degree of oMMT. The effects of the NCO/OH ratio (isocyanate index), the weight ratio of PU/EP and oMMT content on the phase structure and the mechanical properties of the oM‐PU/EP nanocomposites were studied by tensile testing and scanning electronic microscopy (SEM). Water absorption tests showed that the PU/EP interpenetrating networks and oMMT had synergistic effects on improvement in the water resistance of the oM‐PU/EP nanocomposites. Differential scanning calorimetry (DSC) analysis showed that PU was compatible with EP and that the glass transition temperature (T_g) of the oM‐PU/EP nanocomposites increased with the oMMT content up to 3 wt%, and then decreased with further increasing oMMT content. The thermal stability of these nanocomposites with various oMMT contents was studied by thermogravimetric analysis (TGA), and the mechanism of thermal stability improvement was discussed according to the experimental results. Copyright © 2005 Society of Chemical Industry     

The swelling behavior of interpenetrating polymer networks composed of polyurethane and unsaturated polyester

The kinetics of swelling and the sorption performance were observed for the polymer compositions with interpenetrating polymer networks made up of polyurethane and unsaturated polyester during their exposure to chlorobenzene at 25°C. It was found that the rates for solvent transport and solvent absorption processes were controlled by the chemical composition of the formulation studied. On the basis of the observed swelling process, parameters could be assessed which were specific for the mass transfer process, i.e., diffusion coefficient, sorption coefficient, and permeability coefficient. Moreover, an attempt was made to evaluate structural parameters that describe topology of the obtained networks. It was found that the increasing share of polyurethane in the composition reduced crosslinking density in the polyester network that resulted in faster diffusion of the solvent and higher sorption capacity for the solvent. The higher the styrene content in the composition, the higher the crosslinking density in the system, and hence the diffusion of solvent and its sorption inside the polymer network was much more difficult. In the scanning electron microscope analysis of samples, which had been subjected to swelling, no leaching was observed for any phase present in the system, despite phase separation for both the components. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3511–3519, 2006     

Rigid interpenetrating polymer network foams prepared from a rosin-based polyurethane and an epoxy resin

A series of rigid interpenetrating polymer network (IPN) foams, based on a rosin-based polyurethane and an epoxy resin, were prepared by a simultaneous polymerization technique. The changes in the chemical structure, dynamic mechanical properties, and morphology of the rigid IPN foams were investigated by Fourier transform infrared (FTIR) spectroscopy, dynamic mechanical thermal analysis, and scanning electron microscopy. The FTIR analysis showed clearly that the cure rate of the rosin-based rigid polyurethane foam and the epoxy resin were different and, as a result, these two networks formed sequentially in the final rigid IPN foams. All of the rigid IPN foams exhibited a single, broad glass transition that shifted to lower temperature as the epoxy resin content increased. The experimental composition dependence of T_g's of the rigid IPN foams showed slight positive deviation from the Fox equation for homogeneous polymer systems. No phase separation was observed from the scanning electron microscopy investigation. It could be concluded that these two component networks were compatible in the final rigid IPN foams. This compatibility could be attributed to a graft structure in the polyurethane and the epoxy resin networks arising from the reaction of the hydroxyl groups of the epoxy resin with the isocyanate groups of MDI, and from the reaction of the hydroxyl groups of the polyols with the epoxide groups of the epoxy resin, as suggested by FTIR analysis. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 271–281, 1998     

Preparation and properties of a degradable interpenetrating polymer networks based on starch with water retention,amelioration of soil,and slow release of nitrogen and phosphorus fertilizer

In this study, we aimed to develop a degradable nitrogen and phosphorus (NP) fertilizer with properties of slow release, water retention, and remediation of saline soil; the nitrogen and phosphorus was coated with starch/poly(acrylic acid‐co‐acrylamide) [poly(AA‐co‐AM)] superabsorbent (SAAmF) by reverse suspension radical copolymerization. The variable influences on the water absorbency were investigated and optimized. The results of the structure and morphology characterization of SAAmF show that poly(AA‐co‐AM) was grafted partly from the chain of starch, and the different contents of starch brought about a difference in the size of the three‐dimensional net hole of the coating polymer. The property of water retention, the behaviors of slow release of nutrient, and the degradation of the SAAmF were evaluated, respectively, and the results revealed that the water transpiration ratio of soil with SAAmF was lower by approximately 8 percentage points than that of the blank test, about 60% nutrient was released from SAAmF by the 30th day, and 32 wt % of SAAmF with a content of starch of 20% was degraded after 55 days. Moreover, a considerable decrease in the conductivity was observed, which revealed a sharp reduction in the concentration of residual ions for the soil mixed with SAAmF. It may be inferred from these that the product seems to be a promising vehicle for the management of soils, including saline soils. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013