Preparation, characterization and electrochemical corrosion studies on environmentally friendly waterborne polyurethane/Na-MMT clay nanocomposite coatings

In this study, we present the first practical evaluation for the corrosion protection effect of waterborne polyurethane (WPU)/Na⁺-montmorillonite (Na⁺-MMT) clay nanocomposite coating. Typically, a series of waterborne polyurethane (WPU)/Na⁺-montmorillonite (Na⁺-MMT) clay nanocomposite materials have been successfully prepared by effectively dispersing the inorganic nanolayers of commercially purified Na⁺-MMT clay in WPU matrix through direct aqueous solution dispersion technique. First of all, WPU was prepared by polymerizing PCL, DMPA and H₁₂MDI, followed by characterized by nuclear magnetic resonance (¹H NMR), Fourier transform infrared (FTIR) and gel permeation chromatography (GPC). Subsequently, the as-prepared PU/Na⁺-MMT clay nanocomposite (Na⁺-PCN) materials were subsequently characterized by FTIR, X-ray diffraction (XRD) patterns and transmission electron microscopy (TEM).PCN materials in the form of coating at low Na⁺-MMT clay loading up to 3 wt% coated on the cold-rolled steel (CRS) coupons were found to exhibit superior corrosion protection effect over those of neat WPU based on a series of electrochemical measurements of corrosion potential, polarization resistance, corrosion current and impedance in 5 wt% aqueous NaCl electrolyte. Effects of the material composition on the gas permeability, thermal stability and optical clarity of neat WPU along with a series of Na⁺-PCN materials, in the form of coating and free-standing film, were also studies by gas permeability analyzer (GPA), thermogravimetric (TGA), differential scanning calorimetry (DSC) and ultraviolet UV-visible transmission spectroscopy, respectively. As control experiments, a series of PU/organo-MMT nanocomposite (denoted by organo-PCN) materials were also prepared for comparative studies.     

Study on thermal properties of polyurethane nanocomposites based on organo-sepiolite

The effects of sepiolite modified with γ-aminopropyltriethoxylsilane (KH550-Sp) on thermal properties of polyurethane (PU) nanocomposites were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TG), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), and tensile test. The DSC results showed that the glass transition temperature of hard segments in PU/KH550-Sp nanocomposite increased with the increase of KH550-Sp, because sepiolite restricted the formation of hydrogen bonding within hard segments of polyurethane. TG results revealed that the thermal stability of PU was improved by KH550-Sp, and the onset decomposition temperature for PU nanocomposites with a KH550-Sp content of 3 wt% was about 20 °C higher than that for pure PU. The tensile properties of pure PU and nanocomposites before and after ageing 120 °C for 72 h were determined, and it was observed that the percentage loss in tensile strength decreased with the addition of KH550-Sp because of an oxidation barrier of KH550-Sp confirmed by ATR-FTIR.     

Synergism between flame retardant and modified layered silicate on thermal stability and fire behaviour of polyurethane nanocomposite foams

Synergy in flame retardancy of polyurethane foams between phosphorus-based flame retardant (aluminium phosphinate) and layered silicates has been investigated. We used pristine montmorillonite as well as ammonium modified clay (commercially available) and diphosphonium modified clay, which were synthesised by the intercalation of the quaternary diphosphonium salt according to a procedure reported here. The morphology of the foams was characterised through X-ray diffraction (XRD), while thermal properties were characterised by oxygen index test, cone calorimeter and thermogravimetric analysis (TGA). The morphological characterisation showed that pristine and diphosphonium modified clays are almost slightly intercalated, while ammonium modified one is very well dispersed. The results of thermal characterisation showed that in the presence of phosphinate enhancements of oxygen index, fire behaviour, measured by cone calorimeter, and thermal stability have been achieved. Phosphinate is therefore an efficient flame retardant for polyurethane foams and its flame retardancy action takes place in both condensed and gas phases. Pristine and ammonium modified layered silicate bring some enhancements of thermal stability while having no important effect in decreasing peak heat release rate (PHRR) and total heat evolved (THE) when used in conjunction with phosphinate; their main advantage is related to the enhancement of compactness of the char layer formed. Diphosphonium clay is instead effective in further improving the fire behaviour of the foams because of the flame retardancy action of phosphonium: both PHRR and THE were decreased. The analysis of cone calorimeter data showed that clays act through physical effect constituting a barrier at the surface which is effective in preventing or slowing the diffusion of volatiles and oxygen, while phosphinate and phosphonium are more effective owing to their combined action in both condensed and gas phases.     

Processing and thermal properties evaluation of silylated apophyllite–filled epoxy nanocomposite

The primary objective of the research was to evaluate the rheology and thermal properties of silylated apophyllite–filled epoxy nanocomposite. Several n‐octyldimethylsiloxy‐apophyllite with different grafting degrees were synthesized by controlling the ratio of the apophyllite and n‐octyldimethylchlorosilane. The thermal studies of silylated apophyllite have shown that the onset decomposition temperature of silylated apophyllite far exceeds the onset temperature of conventional organoclays (~260 °C). Chemorheological measurements of 1.8 wt% silylated apophyllite–filled tetra functional epoxy (MY720) and difunctional epoxy (DER661) resin mixture showed that the addition of the silylated apophyllite does not dramatically affect the cure profile of the epoxy resin with the availability of 40 min of processing window after the addition of apophyllite. Wide angle X‐ray diffraction and transmission electron microscopy results of the shear mixed and cured nanocomposite suggest that the apophyllite was well dispersed in the epoxy matrix. The thermal studies of epoxy nanocomposite showed an increase in the char yield on the addition of silylated apophyllite to the epoxy resin. In addition, an improvement in the onset decomposition temperature of the cyanopropyldimethylsiloxy‐apophyllite epoxy nanocomposite was observed compared with that of pure epoxy resin. Copyright © 2011 John Wiley & Sons, Ltd.     

Thermal stability, crystallization, structure and morphology of syndiotactic 1,2-polybutadiene/organoclay nanocomposite

Syndiotactic 1,2-polybutadiene/organoclay nanocomposites were prepared and characterized by thermogravimetry analysis (TGA), X-ray diffraction (XRD), polarized optical microscopy (POM), and differential scanning calorimetry (DSC), respectively. The XRD shows that exfoliated nanocomposites are formed dominantly at lower clay concentrations (less than 2%), at higher clay contents intercalated nanocomposites dominate. At the same time, the XRD indicates that the crystal structures of sPB formed in the sPB/organoclay nanocomposites do not vary, only the relative intensity of the peaks corresponding to (0 1 0) and (2 0 0)/(1 1 0) crystal planes, respectively, varies. The DSC and POM indicate that organoclay layers can improve cooling crystallization temperature, crystallization rate and reducing the spherulite sizes of sPB. TGA shows that under argon flow the nanocomposites exhibit slight decrease of thermal stability, while under oxygen flow the resistance of oxidation and thermal stability of sPB/organoclay nanocomposites were significantly improved relative to pristine sPB. The primary and secondary crystallization for pristine sPB and sPB/organoclay (2%) nanocomposites were analyzed and compared based on different approaches. The nanocomposites exhibit smaller Avrami exponent and larger crystallization rate constant, with respect to pristine sPB. Primary crystallization under isothermal conditions displays both athermal nucleation and three-dimensional spherulite growth and under nonisothermal processes the mechanism of primary crystallization becomes very complex. Secondary crystallization shows a lower-dimensional crystal growth geometry for both isothermal and nonisothermal conditions. The activation energy of crystallization of sPB and sPB/organoclay nanocomposites under isothermal and nonisothermal conditions were also calculated based on different approaches.     

Influence of SEBS-g-MA on morphology, mechanical, and thermal properties of PA6/PP/organoclay nanocomposites

Polyamide 6/polypropylene (PA6/PP = 70/30 parts) blends containing 4 phr (parts per hundred resin) of organically modified clay (organoclay) toughened with maleated styrene-ethylene-butylene-styrene (SEBS-g-MA) were prepared by melt compounding using co-rotating twin-screw extruder followed by injection molding. X-ray diffraction (XRD) and transmission electron microscope (TEM) were used to characterize the structure of the nanocomposites. The mechanical properties of the nanocomposites were determined by tensile, flexural, and notched Izod impact tests. The single edge notch three point bending test was used to evaluate the fracture toughness of SEBS-g-MA toughened PA6/PP nanocomposites. Thermal properties were studied by using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). XRD and TEM results indicated the formation of the exfoliated structure for the PA6/PP/organoclay nanocomposites with and without SEBS-g-MA. With the exception of stiffness and strength, the addition of SEBS-g-MA into the PA6/PP/organoclay nanocomposites increased ductility, impact strength and fracture toughness. The elongation at break and fracture toughness of PA6/PP blends and nanocomposites were increased with increasing the testing speed, whereas tensile strength was decreased. The increase in ductility and fracture toughness at high testing speed could be attributed to the thermal blunting mechanism in front of crack tip. DSC results revealed that the presence of SEBS-g-MA had negligible effect on the melting and crystallization behavior of the PA6/PP/organoclay nanocomposites. TGA results showed that the incorporation of SEBS-g-MA increased the thermal stability of the nanocomposite.     

Helical polyurethane@attapulgite nanocomposite: Preparation, characterization and study of optical activity

Helical polyurethane@attapulgite (BM-ATT) based on R-1,1′-binaphthyl-2′,2-diol (R-BINOL) composite was prepared after the surface modification of attapulgite (ATT). BM-ATT was characterized by Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HTEM) and vibrational circular dichroism (VCD) spectroscopy. FT-IR and XRD analyses indicate that the helical polyurethane has been successfully grafted onto the surfaces of the modified ATT without destroying the original crystalline structure of ATT. BM-ATT exhibits the rod-like structure by SEM, TEM, and HTEM photographs. BM-ATT displays obvious Cotton effect for some absorbance in VCD spectrum, and its optical activity results from the singlehanded conformation of helical polyurethane.     

Polyurethane/montmorillonite nanocomposites prepared from crystalline polyols, using 1,4-butanediol and organoclay hybrid as chain extenders

Polyurethane/montmorillonite (PU/MMT) nanocomposites were prepared via in situ polymerization from highly crystalline poly(butylene succinate)/poly(ethylene glycol) polyols and 4,4^′-dicyclohexylmethane diisocyanate, using both 1,4-butanediol and 1, 2, or 3 wt.% of a tris(hydroxymethyl)aminomethane-MMT hybrid, as chain extenders. The corresponding nanocomposites were designated PU-1MMT, PU-2MMT and PU-3MMT, respectively. The layered silicates were mostly intercalated in the nanocomposites. The distances between the individual silicate layers in the PU-1MMT and PU-2MMT were in the range of 2-10 nm, while those in the PU-3MMT were only about 2 nm. The inefficient exfoliation of the clay in this system was mainly due to the high crystallinity and polarity of the PBS polyol. There were no significant changes in the thermal properties of the pure PU and PU nanocomposites. However, the tensile modulus and elongation of the PU-2MMT at break were significantly greater than those of the pure PU and PU-3MMT.     

Comparative studies for the effect of intercalating agent on the physical properties of epoxy resin-clay based nanocomposite materials

In this study, a series of comparative studies for the effect of intercalating agent on the physical properties of the epoxy resin-clay based nanocomposite materials were performed. First, the quaternary alkylphosphonium and alkylammonium salt were both used as the intercalating agents separately for the preparation of organophilic clay through the cationic exchange reactions with Na⁺-montmorillonite clay. Subsequently, the organophilic clay was blent into the epoxy resin through in-situ thermal ring-opening polymerizations to prepare a series of polymer-clay nanocomposite (PCN) materials. The as-synthesized PCN materials were subsequently characterized by Fourier-Transformation infrared (FTIR) spectroscopy, wide-angle powder X-ray diffraction (WXRD), and transmission electron microscopy (TEM).It should be noted that the quaternary alkylphosphonium salt (Φ₃P⁺-C₁₂)-modified clay was found to show better dispersion capability than that of quaternary alkylammonium salt (Me₃N⁺-C₁₆)-modified clay existed in the polymer matrix based on the studies of WXRD and TEM. The better dispersion of (Φ₃P⁺-C₁₂)-modified clay in epoxy resin was found to lead more effectively enhanced physical property such as corrosion protection, gas barrier, mechanical strength, thermal stability, and flame retardant properties of polymers than that of (Me₃N⁺-C₁₆)-modified clay, in the form of coating and membrane, based on the measurements of a series of electrochemical corrosion parameters, gas permeability analysis (GPA), dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and limiting oxygen index (LOI), respectively. Effect of material composition on the physical properties of as-prepared materials was also investigated.     

A MTDSC analysis of phase transition in polyurethane-organoclay nanocomposites

Modulated differential scanning calorimetry (MTDSC) was applied to investigate the phase transition behaviour of polyurethane/organoclay nanocomposites. The endotherm transitions located at 50-80 and 140 °C were re-analysed through revealed thermal features in the MTDSC reversing, non-reversing and dC_p/dT curves. It was proposed that the diffused interfacial phase exists between hard and soft phases in the polyurethane system. The assignment of endotherm at 140 °C is attributed to the hard microphase domain transition, which is similar to an order-disorder transition. The transition in the region of 50-80 °C reveals the relaxation of segments in the interface resulted by annealing. The addition of organoclay resulted in a reduction of hard domain ordering level. A simple method for quantitatively estimating the amount of polymer chains intercalated into layers of clay was introduced, and the relationship between the weight fraction (ω_p), of the polymer intercalated into layers and the weight fraction (ω_c), of clay was established.     

Polymer blend/organoclay nanocomposite with poly(ethylene oxide) and poly(methyl methacrylate)

A series of polymer blend/organoclay nanocomposite at a fixed blending ratio was prepared using equal ratio of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA) via solvent casting method. With respect to nanoscale internal structure, we found that PMMA chains have better affinity with organoclay than PEO, based on the results from X-ray diffraction. Direct visualization via transmission electron microscopy (TEM) also supported the better affinity of PMMA with organoclay by indicating the existence of hybrid structures of mainly intercalated but with some exfoliated forms. The miscible nature of the blend and homogeneous dispersion state of layered silicate in the blend system were investigated via the microscopic fractured surface morphologies. From rheological measurements (storage and loss modulus), we discovered the role of the physical network structure between polymer and organoclay to be a main factor for the enhancement of elastic properties.     

Advanced environmentally friendly anticorrosive materials prepared from water-based polyacrylate/Na-MMT clay nanocomposite latexes

A series of novel advanced environmentally friendly anticorrosive materials have been successfully prepared by effectively dispersing nanolayers of Na⁺-montmorillonite (Na⁺-MMT) clay into water-based polyacrylate latex (i.e., vinyl acrylic terpolymers). First of all, a polyacrylate latex was synthesized through co-polymerizing organic monomers of MMA, BMA and styrene (St) using conventional emulsion polymerization technique with SDS, 1-pentanol and KPS as surfactant, co-surfactant and initiator, respectively. Subsequently, the commercial purified hydrophilic Na⁺-MMT was effectively dispersing into the polyacrylate latex through the direct solution dispersion technique.The as-prepared neat polyacrylate and the series of water-based polyacrylate/Na⁺-MMT clay nanocomposite (Na⁺-PCN) materials were subsequently characterized by FTIR spectroscopy, XRD, TEM and GPC. The water-based Na⁺-PCN materials loaded with low content of Na⁺-MMT when in the form of coating on the cold rolled steel (CRS) coupons was found to be remarkably superior in anticorrosion efficiency over those of neat polyacrylate based on a series of electrochemical measurements of corrosion potential, polarization resistance, corrosion current, and impedance spectroscopy in saline. Effect of material composition on the molecular barrier, optical clarity and thermal stability were also studied by molecular permeability analysis, ultraviolet-visible transmission spectra, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. Organo-PCN materials were also prepared as a control experiment for comparative studies.     

Effect of clay on the corrosion protection efficiency of PMMA/Na-MMT clay nanocomposite coatings evaluated by electrochemical measurements

The preparation of PMMA-clay nanocomposites was investigated by using sodium dodecylbenzenesulfonate (SDS) and potassium peroxodisulfate (KPS) as a surfactant and chain initiator for an in situ emulsion polymerization reaction, respectively. The as-prepared nanocomposites were then characterized by Fourier transformation infrared (FTIR) spectroscopy, wide-angle X-ray diffraction (WAXRD) patterns and transmission electron microscopy (TEM).It should be noted that the nanocomposite coating containing 1 wt% of clay loading was found to exhibit an observable enhanced corrosion protection on cold-rolled steel (CRS) electrode at higher operational temperature of 50 °C, which was even better than that of uncoated and electrode-coated with PMMA alone at room temperature of 30 °C based on the electrochemical parameter evaluations (e.g., E_corr, R_p, I_corr, R_corr and impedance). In this work, all electrochemical measurements were performed at a double-wall jacketed cell, covered with a glass plate, through which water was circulated from a thermostat to maintain a constant operational temperature of 30, 40 and 50 ± 0.5 °C. Moreover, a series of electrochemical parameters shown in Tafel, Nyquist and Bode plots were all used to evaluate PCN coatings at three different operational temperatures in 5 wt% aqueous NaCl electrolyte. The molecular barrier properties at three different operational temperatures of PMMA and PCN membranes were investigated by gas permeability analyzer (GPA) and vapor permeability analyzer (VPA). Effect of material composition on the molecular weight and optical properties of neat PMMA and PCN materials, in the form of solution and membrane, were also studied by gel permeation chromatography (GPC) and UV-vis transmission spectra.     

Atomic force microscopy study on blend morphology and clay dispersion in polyamide‐6/polypropylene/organoclay systems

The phase structure and clay dispersion in polyamide‐6(PA6)/polypropylene(PP)/organoclay (70/30/4) systems with and without an additional 5 parts of maleated polypropylene (MAH‐g‐PP) as a compatibilizer were studied with atomic force microscopy (AFM). AFM scans were taken from the polished surface of specimens that were chemically and physically etched with formic acid and argon ion bombardment, respectively. The latter technique proved to be very sensitive to the blend morphology, as PP was far more resistant to ion bombardment than PA6. In the absence of the MAH‐g‐PP compatibilizer, the organoclay is located in the PA6 phase; this finding is in line with transmission electron microscopic results. Further, the PP is coarsely dispersed in PA6 and the adhesion between PA6 and PP is poor. The addition of MAH‐g‐PP resulted in a markedly finer PP dispersion and good interfacial bonding between PA6 and PP. In this blend, the organoclay was likely dispersed in the PA6‐grafted PP phase. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43:1198–1204, 2005     

Structure and properties of isobutylene-isoprene rubber/swollen organoclay nanocomposites prepared by shear mixing

A new approach was developed to prepare high-performance isobutylene-isoprene rubber/swollen organoclay nanocomposites by shear mixing.Compared with traditional melt compounding method,better dispersion of nanoclay layers in rubber matrix was verified through transmission electron microscopy(TEM) and X-ray diffraction(XRD).The nanocomposites also exhibit significantly improved mechanical properties and gas barrier property.As a mechanism,the molecules of organic swelling agent play a vital role in accelerating the diffusion and intercalation of the matrix molecules.     

In situ synchrotron SAXS/WAXD studies during melt spinning of modified carbon nanofiber and isotactic polypropylene nanocomposite

The structural development of a nanocomposite, containing 95 wt% isotactic polypropylene (iPP) and 5 wt% modified carbon nanofiber (MCNF), during fiber spinning was investigated by in situ synchrotron small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) techniques. The modification of carbon nanofibers (CNFs) was accomplished by a chemical surface treatment using in situ polymerization of olefin segments to enhance its compatibility with iPP, where the iPP/MCNF nanocomposite was prepared by twostep blending to ensure the dispersion of MCNF. X-ray results showed that at low spin-draw ratios, the iPP/MCNF nanocomposite fiber exhibited much higher iPP crystalline orientation than the control iPP fiber. At higher spin-draw ratios, the crystalline orientation of the nanocomposite fiber and that of the pure iPP fiber was about the same. The crystallinity of the composite fiber was higher than that of the control iPP fiber, indicating the nucleating effect of the modified carbon nanofibers. The nanocomposite fiber also showed larger long periods at low spin-draw ratios. Measurements of mechanical properties indicated that the nanocomposite fiber with 5 wt% MCNF had much higher tensile strength, modulus and longer elongation to break. The mechanical enhancement can be attributed to the dispersion of MCNF in the matrix, which was confirmed by SEM results.Dedicated to Prof. E D. Fischer on his 75th birthday.     

Study on solvent permeation resistance properties of nylon6/clay nanocomposite

Nylon6/clay nanocomposite is prepared by mixing organized montmorillonite with nylon6 in HAAKE mixer. Solvent permeation resistance of the nanocomposite is measured to estimate the resistance to solvent permeation. The nanocomposite shows resistance to solvent permeation superior to that of pure nylon6. In addition, the clay content was found to significantly influence the solvent permeation resistance of nylon6, and the maximum improvement in barrier properties of nylon6/clay composite was found as the clay content reached an “optimum” value. By using proper composites and processing conditions, the permeation rate of toluene and ethanol in nylon6/clay nanocomposite is about 3 and 4 times slower than that in pure nylon6 at 50 °C. Our investigation indicated that the crystalline property of nylon6 has a strong impact on the sorption and diffusion of small molecules in the polymer. The improvement in solvent barrier properties of nylon6/clay nanocomposite is attributable to incorporation of an impermeable phase such as the layered silicate, improvement in crystallinity and decrease of crystalline dimension, which are evidenced by XRD, AFM, DSC and polarized optical microscopy (POM) studies.     

Influence of clay surface modification with urethane groups on the crystallization behavior of in situ polymerized poly(butylene succinate) nanocomposites

The crystallization behavior and fine structure of poly(butylene succinate) (PBS) nanocomposites with intercalation (30B20) and exfoliation (30BM20) morphologies, respectively, were investigated via isothermal crystallization testing and synchrotron small-angle X-ray scattering (SAXS). The dynamic viscosity of 30BM20 was markedly increased due to favorable interactions between the PBS matrix and the urethane group on the clay surface. However, 30BM20 showed similar crystallization rates to that of homo PBS because the surface urethane modification for 30BM20 precluded PBS matrix from the metallic group into clay to difficult in contact with each other, resulting in a reduced nucleation activity for the metallic group. SAXS profiles revealed that the long period and amorphous region size for 30B20 drastically decreased during isothermal crystallization. Meanwhile, 30BM20 was similar to those of homo PBS. This result also supports the above explanation for isothermal crystallization behavior. Considering all results in total, the introduction of a urethane modification considerably enhanced the physical properties of PBS but caused delayed crystallization rates.     

Crystallization, morphology, and dynamic mechanical properties of poly(trimethylene terephthalate)/clay nanocomposites

The poly(trimethylene terephthalate) (PTT)/clay nanocomposite has been successfully prepared via melt intercalation using a co-rotating twin screw extruder. The nanocomposite was characterized by wide angle X-ray diffraction (WAXD), transmission electron microscope (TEM), differential scanning calorimetry (DSC), polarized light microscope (PLM) and dynamic mechanical analysis (DMA). The nanocomposite forms an exfoliated structure, which can be observed by WAXD and TEM. The effect of clay layers on the crystallization behaviors of PTT was studied through isothermal and non-isothermal crystallization methods. The results suggest that the introduction of nanosize clay layers accelerates the crystallization rate of PTT and the clay layers act as nucleation agents. The morphology of spherulites was investigated with PLM and the result is well in agreement with crystallization kinetics. DMA shows that glass transition temperature (T_g) and storage modulus (E^′) of the PTT matrix of the nanocomposite are higher than those of pure PTT.     

Structure and properties of polyurethane/polyacrylate latex interpenetrating networks hybrid emulsions

Some new kinds of novel polyurethane (PU)/polyacrylate (PA) latex interpenetrating networks (LIPNs) were synthesized. Firstly PU dispersions were synthesized by self-emulsification polymerization. Then PU/PA LIPNs using PU dispersion as the seed were prepared by soap free emulsion polymerization. The effects of different PU/PA ratios, the blending method and the NCO/OH molar ratio of PU components on PU/PA LIPNs performance were also investigated. The structure and properties of PU/PA LIPNs such as mechanical properties, particle size, morphology of the surface were characterized by dynamic mechanical analysis, scanning electron microscopy, and dynamic light scattering. It was found that PU/PA LIPNs can markedly improve the water resistance and the mechanical properties of PU latex much more than those of PU/PA physical blends due to a great deal of interpenetrating and entangling between PU and PA latex. Moreover, the particle size of PU/PA LIPNs is related to the PA content and NCO/OH molar ratio of PU components: the higher the NCO/OH molar ratio in PU dispersions, the larger is the particle size of PU/PA LIPNs, and the average particle size of PU/PA LIPNs becomes larger with an increase in PA content.