Preparations and properties of waterborne polyurethane/allyl isocyanated-modified graphene oxide nanocomposites

We synthesized waterborne polyurethane (WPU)/allyl isocyanate modified graphene oxide (iGO) nanocomposites by UV curing, and the effects of iGO on the mechanical, dynamic mechanical, and thermal properties of the nanocomposites were systematically investigated. It was shown that the iGO chemically incorporated into the WPU chains by covalent bonding acts as a multifunctional cross-linking agent as well as reinforcing filler. Consequently, the tensile strength, glassy and rubbery state moduli, glass transition temperature, and thermal stability of the WPU were significantly increased up to an iGO content of 1%, beyond which most of the above properties showed a decrease, due probably to the auto-inhibition of the allyl compounds.     

Heat Shrinkable Behavior and Mechanical Response of a Low‐Density Polyethylene/Millable Polyurethane/Organoclay Ternary Nanocomposite

Summary: A low‐density polyethylene (LDPE)/millable polyurethane (PU)/organoclay ternary nanocomposite was successfully prepared. The nanocomposites were characterized by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). The nanocomposites, as evidenced by XRD, are intercalated. The heat shrinkable behavior of the nanocomposites, as well as their pristine counterparts, was studied. It was observed that heat shrinkability decreases with increased filler content. The tensile strength and the tensile modulus of the nanocomposites are higher than their pristine counterparts.

The heat shrinkability of the unfilled LDPE/millable PU blend is highest and it decreases with increased nanofiller content.     

The disorderly exfoliated LDHs/PMMA nanocomposites synthesized by in situ bulk polymerization: The effects of LDH-U on thermal and mechanical properties

The disorderly exfoliated layered double hydroxides/poly(methyl methacrylate) (LDHs/PMMA) nanocomposites were obtained in a two-stage process by the in situ bulk polymerization of methyl methacrylate (MMA) in the presence of 10-undecenoate intercalated LDH (LDH-U). The dispersed behavior of the LDH-U in the PMMA matrix was identified by using X-ray diffraction (XRD), transmission electron microscopy (TEM), and UV/visible transmission spectroscopy. All these nanocomposites showed significantly enhancement of glass transition temperature (T_g) and the decomposition temperatures compared to pristine PMMA, as identified in differential scanning calorimetry (DSC) and thermogravimetric (TGA) analysis. The tensile modulus of these nanocomposites was also enhanced by incorporating the LDH-U into the PMMA matrix and increased as the amount of LDH-U increased. According to the analytical method of Ozawa-Flynn, the degradation activation energies of these nanocomposites are higher than that of pristine PMMA.     

水性聚氨酯阻燃纳米复合材料的Click反应制备及性能

以4,4'-二羟甲基-1,4-庚二炔功能单体作为扩链剂制备了端炔基功能化聚氨酯, 与叠氮基改性纳米蒙脱土(MMT-N₃)、 纳米氢氧化铝(ATH-N₃)和纳米氢氧化镁(MH-N₃)通过Click反应制备了水性聚氨酯(WPU)阻燃纳米复合材料. 采用红外光谱(FTIR)、 核磁氢谱(¹H NMR)和扫描电子显微镜(SEM)对WPU阻燃纳米复合材料的结构进行了表征, 对比研究了纳米阻燃剂配比和制备方法对WPU阻燃纳米复合材料的氧指数、 动态燃烧行为和热稳定性的影响. 阻燃性能研究结果表明, 当MMT-N₃, MH-N₃和ATH-N₃的质量分数分别为7%, 2%和1%时, 采用Click反应制备的复合材料的氧指数比纯WPU高7%, 点燃时间从10 s延长到29 s, 峰值热释放速率和烟释放速率分别降低了41%和42%. 热失重分析结果表明, 当MMT-N₃质量分数为10%时, 与WPU相比, 采用Click反应制备的MMT/WPU复合材料在热失重50%时的温度提高了21 ℃. 复合材料断面和燃烧后残渣的SEM分析证明在聚合物基体中Click反应是分散纳米材料的一种有效方法.     

Hydrogen‐bonding,crystallinity, and morphological properties of poly(silicic acid)/waterborne polyurethane nanocomposites

Unique nanocomposites consisting of poly(silicic acid) nanoparticles (PNs) and waterborne polyurethane (WPU) were prepared. The aliphatic WPU prepared in this study was end‐capped with a silanol group, which could react with PNs via a sol–gel process. PNs were modified with phenyltrimethoxysilane (PTMS) and 3‐(trimethoxysilyl)propyl ester (TMPE) and then blended with WPU. The structure–property relationships were examined. Solid‐state ²⁹Si NMR spectra of WPU showed that structures T₁, T₂, and T₃ of WPU decreased and structures Q₃ and Q₄ of PN/WPU nanocomposites increased gradually. When the PN concentration increased to 10 wt %, PN/WPU nanocomposites exhibited the maximum fraction of hydrogen‐bonded carbonyl groups. In the PTMS–PN and TMPE–PN systems, the fraction of hydrogen‐bonded carbonyl groups fluctuated stably when the concentrations of PTMS–PN and TMPS–PN exceeded 5 wt %. The X‐ray diffraction results revealed that α‐form, γ‐form, or triclinic crystallization could be found in the WPU matrix. A differential scanning calorimetry spectrum showed that the crystalline structure of the hard segment of WPU was influenced by the nanoparticle concentration. The degrees of crystallinity were 88% for the PN/WPU nanocomposites, 41% for the PTMS–PN/WPU nanocomposites, and 54% for the TMPE–PN/WPU nanocomposites when the PN, PTMS–PN, and TMPE–PN concentrations were 5 wt %. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1076–1089, 2005     

Effect of interaction between poly(ethylene terephthalate) and carbon nanotubes on the morphology and properties of their nanocomposites

Poly(ethylene terephthalate) (PET) nanocomposites were prepared by melt‐extruding mixtures of PET and functionalized multiwalled carbon nanotubes (MWNTs) with some interaction with PET molecules. For the functionalization of MWNTs, benzyl isocyanate and phenyl isocyanate with different molecular flexibility were employed on the surface of the MWNTs via chemical modification, respectively. The reaction for functionalization of MWNTs was confirmed by FTIR and transmission electron microscopy (TEM) measurements. TEM observations indicated that both benzyl and phenyl isocyanate groups covered the surface of the MWNTs after functionalization. The PET nanocomposites containing isocyanate groups showed improved mechanical properties, including the tensile strength and tensile modulus, compared with those with pristine and acid‐treated nanotubes. These improvements were ascribed to π–π interactions between the aromatic rings of PET molecules and the isocyanate group in MWNTs. The functionalized MWNTs showed a better dispersion of carbon nanotubes in the matrix polymer and a different fractured cross‐section morphology in scanning electron microscope measurements relative to the pristine MWNTs. The crystallinity of the functionalized MWNT‐PET nanocomposites was significantly higher than that of the pristine and acid‐treated MWNTs. FTIR results indicated that the presence of carbon nanotubes induced trans‐conformation of PET chains, and trans conformation was particularly dominant in PET composites incorporating MWNT‐phenyl. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 900–910, 2008     

Water‐assisted melt compounding of nylon‐6/pristine montmorillonite nanocomposites

An exploratory pioneering study on the fabrication of nylon‐6/montmorillonite (MMT) nanocomposites with the aid of water as an intercalating/exfoliating agent via melt compounding in a twin‐screw extruder was conducted. Commercial nylon‐6 pellets and pristine MMT powder were directly fed into the hopper of the extruder. Water was then injected into the extruder downstream. After interactions with the nylon‐6 melt/pristine MMT system, water was removed from the extruder further downstream via a venting gate. As such, no third‐component residual was left within the extrudates. Transmission electron microscopy micrographs showed that pristine MMT was uniformly dispersed in the nylon‐6 matrix. The contact time between water and the nylon‐6/pristine MMT system inside the extruder was so short that nylon‐6 was subjected to very little hydrolysis, if any. The resultant nanocomposites showed higher stiffness, superior tensile strength, and improved thermal stability in comparison with their counterparts obtained without water assistance and the nylon‐6/organic MMT nanocomposites. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1100–1112, 2005     

Synthesis and thermal properties of antimony doped tin oxide/waterborne polyurethane nanocomposite films as heat insulating materials

The waterborne polyurethane (WPU) was synthesized from the polycondensation between isophorone diisocyanate (IPDI) and polyoxypropylene glycol (N‐210) and then dispersed into water. Subsequently, the WPU emulsion was modified with antimony doped tin oxide (ATO) nanoparticle by ultrasonic dispersion. The ATO/WPU emulsion was cast onto Teflon molds. After being dried, ATO/WPU films were prepared. TEM indicated that the ATO nanoparticles were homogeneously dispersed in the polymer matrix at the nanometer scale. DSC showed that the ATO/WPU nanocomposites displayed increased glass transition temperatures compared to the control WPU. The mechanical properties of the films were characterized by dynamic‐mechanical analysis (DMA). The higher glass transition temperature and storage modulus indicates the superior mechanical properties of WPU modified by ATO nanoparticles over the conventional unmodified WPU. The thermal behaviors of the films were evaluated by thermogravimetric analysis (TGA). It could be found that the incorporation of ATO into WPU can improve the thermal stability dramatically. The results from UV–visible–near infrared spectra indicated that the ATO/WPU films could decrease the infrared transmission effectively. The heat‐insulation measurements showed that glass coated with ATO/WPU films possessed better heat‐insulating effect than empty glass. Copyright © 2010 John Wiley & Sons, Ltd.     

Self-assembled fabrication and flame-retardant properties of reduced graphene oxide/waterborne polyurethane nanocomposites

The graphite oxide (GO) was prepared from expandable graphite by the pressurized oxidation method, and samples were characterized using XRD, UV–Vis, and TEM. GO is reduced in situ emulsion using hydrazine to achieve reduced graphene oxide/waterborne polyurethane (rGO/WPU) nanocomposites. The effect of rGO content on the stability, fracture morphologies, mechanical performance, thermal degradation, and flame-retardant properties of rGO/WPU composites was investigated by zeta potential analyzer, TEM, SEM, universal testing machine, TG, and Cone Calorimeter. The results of zeta potential, TEM, and SEM analysis indicate that rGO has a good stability and dispersibility in rGO/WPU nanocomposites. The results of mechanical tests showed that the mechanical properties of rGO/WPU nanocomposites increased consistently with increasing rGO content up to 2 mass%, and TG showed that the thermostability of rGO/WPU nanocomposites decreased slightly compared to pure WPU, but carbon residue increased from 0.99 to 1.99 % when the mass fraction of rGO in WPU is 2 %. Cone Calorimeter test indicated that the flame-retardant and smoke suppression properties of rGO/WPU composites showed significant improvement compared to the WPU alone. When the mass fraction of rGO is 1 %, the total smoke release and smoke factor decreased by 25 and 38 %, respectively, compared to those of pure WPU.     

Preparation of PLA-based nanocomposites modified by nano-attapulgite with good toughness-strength balance

Polylactic acid (PLA) was modified by poly (butylene adipate-co-terephthalate) (PBAT) and nano-attapulgite (AT) using the melt blending technique. Ethylene-butyl acrylate-glycidyl methacrylate (E-BA-GMA) was used as a compatibilizer which can bond the AT nanoparticles with PLA/PBAT matrix by interaction between the epoxy and hydroxyl groups. The effects of the AT content on the mechanical properties, thermal properties, crystallinity and morphology of PLA/PBAT/ATT nanocomposites were investigated. The results showed that the tensile strength, elongation at break and impact strength of PLA/PBAT could be simultaneously increased by incorporating AT nanoparticles. PLA/PBAT/AT nanocomposites possessed higher thermal stability than pure PLA/PBAT. In the ternary composite system of PLA/PBAT/AT, AT acted as a heterogeneous nucleating agent and was able to increase the crystallization temperature. When the AT content was low (≤2.5 wt%), AT nanoparticles could uniformly disperse in the PLA/PBAT matrix. In general, AT was an effective filler to reinforce and toughen PLA/PBAT blend simultaneously, and the PLA/PBAT/AT nanocomposite with 2.5 wt% AT exhibited a good combination of strength and toughness.     

Flammability, structure and mechanical properties of PP/OMMT nanocomposites

Polypropylene/organoclay (PP/OMMT) nanocomposites were prepared in a twin-screw corotating extruder using two methods. The first method was the dilution of commercial (PP/50% Nanofil SE3000) masterbatch in PP (or PP with commercial flame retardant). The second method consists of two stages was the extrusion of maleic anhydride grafted polypropylene (PP-g-MAH) with commercially available organobentonite masterbatch in first stage and dilution of the masterbatch in PP (or PP with commercial flame retardant) in second stage. XRD results showed no intercalation in composites obtained from commercial masterbatch without compatibilizer and semi - delamination for compatibilized systems. Tensile tests revealed that nanocomposites with 5% of organoclay have a slightly higher tensile modulus and tensile strength than pristine PP, however addition of the commercial flame retardant (FR) reduces mechanical parameters to roughly the level of those for neat PP. PP/OMMT composites have approx. 25% higher oxygen index than pristine PP, and this changes slightly after the addition of FR. The cone calorimeter tests showed a decrease of a heat release rate (HRR) and a mass loss rate (MLR) after the addition of FR.     

Functionalization of graphene oxide with different diisocyanates and their use as a reinforcement in waterborne polyurethane composites

Abstract

To examine the reinforcing effects of isocyanated graphene oxide (NCO-GO) on a waterborne polyurethane matrix, the surface of GO was respectively modified by isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI) and toluene diisocyanates (TDI) and then confirmed by FT-IR, Raman, TGA, XRD, TEM, AFM and SEM-EDS. The dispersity behavior between different NCO-GO and polymer was evaluated by FESEM and XRD. The nanocomposites’ chemical structure, emulsion morphology, hydrophobicity, thermal and mechanical properties were investigated by FT-IR, TEM, TGA, tensile testing machine and water contact angle test, respectively. It was shown that these properties of nanocomposites including tensile strength, initial thermal degradation and hydrophobicity were increased by the incorporation of NCO-GO, in which, particularly, the tensile stress and initial degradation temperature were respectively increased from 13.32 to 18.80?Mpa and 249 to 288?°C after the addition of TDI-GO. These superior reinforcing effects were attributed to the two-dimensional structure of NCO-GO as well as the good interfacial adhesion between the NCO-GO and WPU matrix.     

Physical characteristics and properties of waterborne polyurethane materials reinforced with silk fibroin powder

Degummed silk filament was pulverized with a home‐made machine to obtain silk fibroin (SF) powder, and the structure, morphology, and particle size of the SF powder were investigated. The individual spherical particles and aggregates with different morphology of silk fibroin coexisted in water. A waterborne polyurethane (WPU) aqueous dispersion was blended with the SF powder to prepare novel blended materials with improved physical properties. The average particle size and zeta potential of the WPU/SF aqueous dispersions were characterized. The result showed that the WPU/SF dispersion with higher SF content exhibited a less negative zeta potential and a larger average particle size. Furthermore, the effect of SF content on the morphology, miscibility, and mechanical properties of the resulting blended films was studied by scanning electron microscopy, wide‐angle X‐ray diffraction, dynamic mechanical thermal analysis, and tensile testing. The films showed an improved Young's modulus and tensile strength from 0.3 to 33.8 MPa, and 0.6 to 5.2 MPa, respectively, with the increasing of SF up to a content of 26 wt %. The negative charges in the periphery and the small particle size made a good effort on dispersing SF powder into the WPU matrix as small aggregates, and the SF powder led to the efficient strengthening of WPU materials. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 940–950, 2010     

Preparation of Antibacterial Waterborne Polyurethane/silver Nanocomposite

Stable aqueous dispersions of silver (Ag) nanoparticles were prepared by reducing silver nitrate solutions with sodium borohydride (NaBH₄) in the presence of waterborne polyurethane as a stabilizing agent. WPU/Ag nanocomposites were obtained after evaporating water. Transmission electron microscope (TEM) shows nanoscale Ag particles are well dispersed in WPU matrix at a lower concentration, while particles exhibit a little aggregation at a higher concentration. UV‐visible spectra, X‐ray powder diffraction, and energy dispersive X‐ray spectrometer (EDS) confirm the existence of Ag particle in WPU matrix. The WPU/Ag composite films show good antibiotic ability.     

Tailoring the morphology and properties of waterborne polyurethanes by the procedure of cellulose nanocrystal incorporation

Polyurethane waterborne synthesis was performed using a two-step method, commonly referred to as a prepolymer method. Nanocomposites based on waterborne polyurethane and cellulose nanocrystals were prepared by the prepolymer method by altering the mode and step in which the nanofillers were incorporated during the polyurethane formation. The morphology, structural, thermal, and mechanical properties of the resulting nanocomposite films were evaluated by Fourier transform infrared spectroscopy (FTIR), small angle X-ray scattering (SAXS), scanning electron microscopy (SEM), and tensile tests. FTIR results indicated that the degree of interaction between the nanofillers and the WPU through hydrogen bonds could be controlled by the method of cellulose nanocrystal incorporation. Data obtained from SAXS experiments showed that the cellulose nanocrystals as well as the step of the reaction in which they are added influenced the morphology of the polyurethane. The reinforcing effect of CNCs on the nanocomposites depends on their morphology.     

A brief survey on CLAYPEN and Nanocomposites based on unmodified PE and organo-pillared clays

New clay fillers are mixed with linear low-density polyethylene at 160 °C for 10 min to obtain clay-PE nanocomposites (CLAYPEN) by melt intercalation. Raw montmorillonite (Mt) was pillared (PMt) with partially hydrolyzed Al and Fe salt solutions and further reacted with hexadecyl trimethylammonium bromide (OPMt). For comparison, the hexadecyl trimethylammonium-montmorillonite (OMt) was prepared as a reference material. PE is not intercalated by organoclay. In investigating the pillared clay-PE nanocomposites, XRD is not an appropriate indicator of intercalation of PE, which penetrates into the mesoporous OPMt as shown by TEM. All the nanocomposites have higher Young modulus values than the pristine PE. The best compromise between the other mechanical properties (tensile strength and elongation at break) is obtained with the OPMt-PE nanocomposite. Cone-calorimeter study shows that peak heat release rate value of PE decreases substantially (34%) on addition of 5 phr of this novel OPMt filler.     

Thermal,mechanical and electroactive shape memory properties of polyurethane (PU)/poly (lactic acid) (PLA)/CNT nanocomposites

Polymer blend nanocomposites based on thermoplastic polyurethane (PU) elastomer, polylactide (PLA) and surface modified carbon nanotubes were prepared via simple melt mixing process and investigated for its mechanical, dynamic mechanical and electroactive shape memory properties. Chemical and structural characterization of the polymer blend nanocomposites were investigated by Fourier Transform infrared (FT-IR) and wide angle X-ray diffraction (WAXD). Loading of the surface modified carbon nanotube in the PU/PLA polymer blends resulted in the significant improvement on the mechanical properties such as tensile strength, when compared to the pure and pristine CNT loaded polymer blends. Dynamic mechanical analysis showed that the glass transition temperature (T_g) of the PU/PLA blend slightly increases on loading of pristine CNT and this effect is more pronounced on loading surface modified CNTs. Thermal and electrical properties of the polymer blend composites increases significantly on loading pristine or surface modified CNTs. Finally, shape memory studies of the PU/PLA/modified CNT composites exhibit a remarkable recoverability of its shape at lower applied dc voltages, when compared to pure or pristine CNT loaded system.     

A new thermoplastic vulcanizate (TPV)/organoclay nanocomposite: Preparation,characterization, and properties

The preparation, characterization, and properties of the new thermoplastic vulcanizate (TPV)/organoclay nanocomposites are reported in this article. The nanocomposites were prepared by the melt intercalation method. The organoclay was first treated with glycidyl methacrylate, which acts as a swelling agent for organoclays, as well as a grafting agent for TPV (in the presence of dicumyl peroxide) during the melt mixing. The nanocomposite was intercalated, as evidenced by X‐ray diffraction. The tensile modulus of the 5% TPV/organoclay nanocomposite was higher than that of the 20% talc‐filled microcomposite. The storage modulus of the nanocomposite was higher than that of the pristine TPV. The most important observation is obtained from dynamic mechanical analysis, which reveals that the glass‐transition temperature of the polypropylene phase of the nanocomposite increases (as compared to virgin TPV), whereas the ethylene–propylene–diene monomer phase remains almost the same. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2900–2908, 2004     

Morphology and properties of waterborne polyurethane/clay nanocomposites

Aqueous emulsion of polyurethane ionomers, based on poly(tetramethylene glycol) or poly(butylene adipate) as soft segment, isophorone diisocyanate as diisocyanate, 1,4-butandiol as chain extender, dimethyl propionic acid as potential ionic center, triethylene tetramine as crosslinker, and triethyl amine as neutralizer, were reinforced with organoclay to give nanocomposites. The particle size of emulsion was measured and the morphology of these nanocomposites was observed by transmission electron microscope, where the effectively intercalated or exfoliated organoclay was observed. The reinforcing effects of organoclay in mechanical properties of these nanocomposites were examined by dynamic mechanical and tensile tests, and the Shore A hardness was measured. Enhanced thermal and water resistance and marginal reduction in transparency of these nanocomposites were observed compared with pristine polymer.     

Fabrication of functional waterborne polyurethane/montmorillonite composites by click chemistry method

"Click" chemistry method was used to fabricate novel waterborne polyurethane (WPU)/montmorillonite (MMT) composites based on alkyne-containing WPU and azide-modified montmorillonite. The morphology of these composites was characterized by x-ray diffractometer, scanning electron microscope. The mechanical properties, thermal stability, and flame resistance of the composites were investigated by tensile, thermogravimetry and cone calorimetric experiments, etc. The experimental results show that the tensile strength, water resistance and flame retardancy of the WPU/MMT composites have been reinforced efficiently owing to the linking of MMT by click reaction.