Structure–property correlation study of hyperbranched polyurethane–urea (HBPU) coatings

This paper deals with the structure–property relation of different HBPU coatings based on the variation of parameters like, NCO/OH ratio, generation number and type of diisocyanates used. For this, the NCO terminated HBPU prepolymers were synthesized first by reacting the different generation hyperbranched polyesters (HBPs) with excess diisocyanates. In the next step, these HBPU prepolymer coated films were completely moisture cured to get the desired HBPU coatings. The synthesized polymers were confirmed by ¹H, ¹³C NMR and FT-IR spectroscopy methods whereas structure–property relation was drawn from the FT-IR peak deconvolution technique. The degree of branching (DB) and percent composition of different structural units present in the HBPs were calculated from the ¹H and ¹³C NMR data by using Fretch equation. The melt viscosity study of different HBP samples suggests that most polyester sample showed Newtonian behavior. The coating film properties were studied by DMTA, TGA, UTM, and contact angle measurement instruments. DMTA and TGA data shows that the increase of NCO/OH ratio and generation number had a favorable impact on storage modulus (E′), glass transition temperature (T_g), onset degradation temperature (T_1ON) and char residue values of the coatings. The contact angle and UTM data suggest that the hydrophobicity and tensile strength increases but flexibility decreases with increasing the NCO/OH ratio.     

Structure–property evolution of poly(ethylene terephthalate)/poly(trimethylene terephthalate) side-by-side self-crimp filament

To investigate the microstructure and mechanical properties of self-crimping two-component side-by-side bicomponent filament, this paper focuses on systematically investigating the structure–property evolution of poly(ethylene terephthalate) (PET)/poly(trimethylene terephthalate) (PTT) side-by-side bicomponent filament prepared via melt spinning with various component ratios, drawing and heating treatment. The investigation was operated upon the combination of morphology analysis, thermal analysis, crystallization, and orientation analysis. The variation of cross section and curl-morphology, crystallization, and microstructures mainly containing lamellar and microfibrillar crystals as well as their effects on the mechanical and self-crimping properties were discussed. As the draft ratio (DR) increases, the crystallinity, sonic orientation factor, tensile strength, and crimp-recovery rate of the filaments were increased. The sonic orientation factor in the crystalline region decreases from 0.923 to 0.777 but increases from 0.677 to 0.903 in the amorphous region. In contrast to the variation of the DR, heating temperature has a limited effect on the tensile strength of the PET/PTT hybrid filaments. Crimp-recovery rate, however, first increases to 11.8 and then decreases to 9.8 with an increasing heating temperature from 144 to 168°C. Most of these behaviors have been attributed to changes in the ratio of contractile stress for both PTT and PET components, originating from microstructural evolution in hybrid filaments, including crystal growth, breakage, deflection, and deformation of chains along the axial direction. As a summary, an interpretive diagrammatic sketch has been proposed to clarify the structure–property relationships of the commercial PET/PTT filaments.     

High performance moisture cured poly(ether–urethane) amide coatings based on renewable resource (cottonseed oil)

In this investigation, polyetheramide resin was prepared through the condensation polymerization of N,N-bis (2-hydroxyethyl) cottonseed oil fatty amide (HECOFA) with bisphenol-A. It was further modified by 2,4-toluene diisocyanate (TDI) in 10–30 wt% of polyetheramide to develop a series of moisture curing urethane-modified polyetheramide resins (UMCOPEtA). The synthesized resin was characterized using ¹H NMR, ¹³C NMR, FTIR and solubility in various organic solvents at room temperature. The thermal and curing behavior of the resin was investigated using thermogravimetric analysis and differential scanning calorimetric techniques. The physico-chemical properties such as hydroxyl value, iodine value, specific gravity and mechanical properties like scratch hardness, impact, and flexibility were determined by standard laboratory methods. Coatings of UMCOPEtA resin were prepared on mild steel panels to evaluate chemical resistance performance against acid, alkali, water and xylene. The newly developed UMCOPEtA coatings showed improved hardness, impact, gloss, water and chemical resistance when compared with unmodified polyetheramide coatings, and thus were found to be suitable as a high performance coating material.     

Electrodeposition of Zn–SiC nanocomposite coatings

Zn–SiC composite coatings were obtained on mild steel substrate by electrodeposition technique with high-current efficiency. A slightly acidic chloride bath, containing SiC nanoparticles and gelatine as additive, was used. The electrodeposition was carried out under galvanostatic control with pulsed direct current; the effect of experimental parameters (temperature, average current density and particles concentration) on composition, morphology and structure of the deposit was studied. Coatings were characterized by means of scanning electron microscopy, energy dispersive X-ray analysis, X-ray diffractometry and Vickers microhardness measurements. Zn–SiC electrodeposits with the best characteristics were obtained by performing electrodepositions at 45 °C, with 20 g L^?1 SiC in the bath and with average current density in the range 100–150 mA cm^?2. Under these experimental conditions, homogeneous and compact coatings, with low-grain size and SiC content ranging from 1.7 to 2.1 wt%, were found to be electrodeposited. Microhardness measurements showed for these deposits an increase of about 50 % with respect to those without nanoparticles obtained in the same experimental conditions.     

Development of novel waterborne poly(1-naphthylamine)/poly(vinylalcohol)–resorcinol formaldehyde-cured corrosion resistant composite coatings

Advancements in the field of corrosion protective coatings have headed towards the utilization of conducting polymer-based blends and composites for the formulation of corrosive protective paints and coatings. With the aim to develop an ecofriendly waterborne conducting polymer-based protective coating material, corrosion protective behavior of waterborne resorcinol formaldehyde (RF)-cured composite coatings of poly(1-naphthylamine) (PNA)/poly(vinylalcohol) (PVA) was investigated on mild steel (MS). The corrosion protective performance was evaluated by physicochemical, physicomechanical, corrosion protective efficiency and resistance in acid, alkaline and saline media by open circuit potential (OCP) measurements. The morphologies of coated, uncoated as well as corroded samples were analyzed by SEM technique. Superior corrosion protective performance was observed which was compared to the reported solvent-based conductive polymer coatings in different corrosive media.     

A crosslinked waterborne poly(urethane-urea) oligomer enables mechanically strong waterborne polyacrylate–poly(urethane-urea) hybrid films with superior film-forming ability

In this article, a crosslinked waterborne poly(urethane-urea) (WPUU) is synthesized based on the terminal aromatic amine polyether (DP-1000) and aliphatic isophorone diisocyanate. Then WPUU is compound with acrylate monomer by emulsion polymerization to produce waterborne polyacrylate–poly(urethane-urea) (WPUUA) hybrid emulsions. Compared with waterborne polyacrylate (WPA) film, the film-forming ability of WPUUA film is improved and the surface roughness R_a and R_q of WPUUA film decreases from 47.5 and 36.4 nm to 35.2 and 18.8 nm, respectively. Meanwhile, the mechanical properties of WPUUA films are significantly improved compared to WPA film. In addition, the performances of WPUUA hybrid films can be modified according to requirements by adjusting the molar ratio between DP-1000 and polyisocyanate. As a result, these WPUUA hybrid emulsions have great application potential in waterborne coatings and other fields.     

Structure–property correlations of flexible clear coats

In this paper thermomechanical and mechanical properties of various free clear coat films for coil-coated steel sheets were studied by dynamic mechanical analysis and tensile testing. To establish structure–property correlations, polyacrylate and polyester binder resins with varying molar mass and functionality were investigated. The clear coat films based on polyacrylate binders exhibited higher glass transitions values, crosslinking densities, elastic modulus and tensile strength values. For both resin types, a relationship of the properties glass transition temperature, crosslinking density, stiffness and tensile strength and the functionality considering the molar mass and the hydroxyl value of the resins was obtained. The elastic strain energy of the investigated brittle clear coat films depended mainly on the elastic modulus.     

Intercalative redox polymerization and characterization of poly(4-vinylpyridine)–vermiculite nanocomposite

A new nanocomposite material consisting of poly(4-vinylpyridine) (PVP) and vermiculite is synthesized by the intercalative redox polymerization of VP in the gallery of copper(II) ion-exchanged vermiculite. The formation of a single filament of the polymer in the gallery is confirmed by the increase in gallery spacing of 4.7 Å as indicated by X-ray diffraction (XRD) analysis. Electron spin resonance studies confirm the presence of Cu(II) upon ion exchange and its absence following redox polymerization. The amount of polymer present in the gallery is found to be ∼18–19 mass % by thermogravimetric analysis. Confining the polymer to the gallery spacing in vermiculite results in enhanced thermal stability that is evident from the increase in the initial decomposition temperature by ∼300°C. Differential scanning calorimetry of the nanocomposite indicates that the polymer is confined to a restricted geometry because of the absence of a glass-transition temperature, which confirms the XRD finding. The IR absorption peaks corresponding to PVP and the expected PVP UV π–π* transition at 275 nm, along with the XRD and thermal data confirms that the gallery expansion is due to the PVP filament. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 555–561, 2001     

Sol–gel processing of hybrid nanocomposite protective coatings using experimental design

Environmentally friendly hybrid nanocomposite sol–gel coatings as substitutes for chromate conversion coatings have attracted a great deal of attention recently. The coatings derived from hydrolysis and condensation of polymerizable silane precursors tetraethylorthosilicate (TEOS) and 3-glycidoxypropyltrimethoxysilane (GPTMS) were deposited onAA5083 substrates by a dip coating technique. Statistical design of experimental (DoE) methodology based on Taguchi orthogonal design has been used to study and optimize compositional and process parameters using multifactor analysis of variance (ANOVA) analysis method and the adhesion strength of coatings to the substrate as per pull off test has been used as a response. Adhesive strength of sol–gel coatings to the substrate was evaluated using pull off and tape tests. Bending, impact resistance and pencil scratch tests were employed to characterize mechanical properties of different coatings. The surface morphology and chemical composition of the hybrid films were studied by atomic force microscopy (AFM) and Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR/FTIR), respectively. Optical microscopy (OM) and field emission scanning electron microscopy (FE-SEM) were used to investigate structure of the coatings. The results show an increase of the hydrolysis water content at a constant organic/inorganic molar ratio and other variable parameters increases adhesion of coatings to substrate, and optimum coatings exhibit excellent mechanical properties as well as adhesive to the substrate.     

Electrophoretic deposition of titania–carbon nanotubes nanocomposite coatings in different alcohols

The suspensions of titania nanoparticles in different alcohols (methanol, ethanol and butanol) were prepared using triethanolamine (TEA) as a dispersant. The optimum concentration of TEA was 16.67, 8 and 0.33 mL/L in methanol, ethanol and butanol, respectively. Two component suspensions of titania (20 g/L) and carbon nanotubes (CNTs) (0.1, 0.2, 0.5 and 1 g/L) were prepared in different alcohols without and with optimum concentration of TEA. The finer and positively charged titania nanoparticles were heterocoagulated on the surface of coarser and negatively charged CNTs and generated the titania–CNT composite particles with the net positive charge. In the presence of TEA, titania nanoparticles completely covered CNTs surface due to their higher positive surface charge. At same CNT concentration, the deposition rate was faster for suspensions with TEA additive due to the faster mobility of the composite particles. The photocatalysis efficiency of coatings for methylene blue degradation increased as CNTs were incorporated in their microstructure.     

Thermal–mechanical property and fracture behaviour of plasticised PLA–CaCO3 nanocomposite

Abstract

This study investigates the influence of two plasticisers, polyethylene glycol (PEG) and tributyl citrate (TbC), on the thermomechanical properties and fracture behaviour of nanosized calcium carbonate blended poly(lactic acid). Various compositions of nanocomposites were compounded and processed using co-rotating twin screw extrusion and compression moulding. DMA analysis shows that adding nano-CaCO₃ reduced the storage modulus (E′) of the nanocomposite while the glass transition temperature (T_g) of the samples was not affected. Furthermore, plasticised poly(lactic acid) (PLA) showed an improvement in elongation at break in all samples, and the impact resistance of the nanocomposites was also improved by 1·6 times with the addition of 20 phr PEG plasticiser and by 1·4 times with the addition of 20 phr TbC plasticiser. Morphological study reveals that the fracture behaviour of PLA-CaCO₃ nanocomposites changed from brittle to ductile after plasticisers were incorporated.     

Structure and properties of electrodeposited Ni–Co–YZA composite coatings

The aim is to develop an economical composite coating with high thermal stability. Ni–Co alloys are found to possess better thermal, physical and mechanical properties compared to Ni. Also, oxide particles as distributed phase can impart better thermal stability. Hence, particulates of composite Yttria stabilised zirconia, a commonly used high temperature material and alumina (YZA) were reinforced in various Ni–Co alloy matrices through electrodeposition. The influence of YZA on the microhardness, tribology and corrosion behaviour of Ni–Co alloys with Co contents of 0 wt.%, 17 wt.%, 38 wt.% and 85 wt.% was evaluated. Optical and Scanning Electron Microscopy (SEM) confirmed the presence of YZA particles and Energy Dispersive X-ray Analysis (EDX) revealed the composition. Tribology testing showed that composite containing 38 wt.% Co displayed better wear resistance. It was found from the immersion corrosion studies that Ni–17Co–YZA coating displayed improved corrosion resistance. Thermal stability studies showed that Ni–85Co–YZA coating retained its microhardness at temperatures of 600 °C. Thus, these coatings can be tailored for various applications by varying the cobalt content.     

DSC studies of poly(vinyl chloride)/poly(ε-caprolactone)/poly(ε-caprolactone)-b-poly(dimethylsiloxane) blends

Poly(vinyl chloride)/poly(ε-caprolactone)/poly(ε-caprolactone)-b-poly(dimethylsiloxane) [PVC/PCL/(PCL-b-PDMS)] blends were prepared by solvent casting from tetrahydrofuran. The content of PVC was kept constant (60 wt%); the PCL and PCL-b-PDMS contents were varied by replacing different amounts of PCL [0–20 wt% from the PVC/PCL (60/40) blend] with PCL-b-PDMS copolymer having different molecular weights of the PCL blocks. The thermal properties of prepared blends were investigated by differential scanning calorimetry in order to analyse miscibility (through glass transition temperature) and crystallinity. Differential scanning calorimetry analyses show that the PVC/PCL/PCL-b-PDMS blends are multi-phase materials which contain a PVC plasticized with PCL phase, a block copolymer PCL-b-PDMS phase (with crystalline and amorphous PCL and PDMS domains) and a PCL phase (preponderantly crystalline).     

Influence of additives on microstructure and property of microarc oxidized Mg–Si–O coatings

Ceramic coatings were fabricated on ZK60 magnesium alloy substrate by microarc oxidation (MAO) in Na₂SiO₃–KOH base electrolyte with four kinds of additives (i.e. KF, NH₄HF₂, C₃H₈O₃ and H₂O₂). The effects of these additives on microstructure and property of coatings were investigated. The surface morphology, phase composition and corrosion resistance of the ceramic coatings were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and simulation body fluid (SBF) immersion test respectively. It is found that different additives can change the spark discharge phenomenon during microarc oxidation. It is proved that both potassium fluoride (KF) and ammonium bifluoride (NH₄HF₂) promote discharge and accelerate reaction while the introduce of glycerol (C₃H₈O₃) leads to the refining of sparks and reduction of thermal effects. Results also demonstrate that the introduce of hydrogen peroxide (H₂O₂) contributes to the increase of coating surface roughness and enlargement of surface micropore size. XRD results indicate that the ceramic coatings are mainly composed of Mg₂SiO₄, MgSiO₃ and SiO₂. The introduce of H₂O₂ hinders the reaction between SiO₂ and MgO and creates favorable conditions for the formation of the MgO phase. The ceramic coatings formed in base electrolyte containing 7 g/L NH₄HF₂ and 5 mL/L C₃H₈O₃ exhibit the highest corrosion resistance.     

Structure of carboxylated acrylonitrile-butadiene rubber (CNBR)–clay nanocomposites by co-coagulating rubber latex and clay aqueous suspension

Carboxylated acrylonitrile-butadiene rubber (CNBR)–clay mixtures were prepared by co-coagulating rubber latex and clay aqueous suspension, then combining the mixtures with a rubber ingredient and vulcanizing by a traditional rubber mixing processing procedure. Transmission electron microscopy (TEM) showed that the silicate layers of clay were delaminated or intercalated with CNBR and dispersed in the CNBR matrix at a nanometer level during co-coagulating. X-ray diffraction indicated that the amount of CNBR intercalating between the layers increased with the increase of content of clay in CNBR, which is in contrast with the results of other studies. Some reasons were put forward for this discrepency. The aspect ratio (width/thickness) of the platelet inclusions was reduced and the silicate layers were aligned more orderly during the compounding operation on an open mill. The intercalated CNBR, on co-coagulating, still remained within the interlayer space after curing. In these nanocomposites, the particles of silicate layers were dispersed at the nanometer level and the structure was a combination of delaminated and intercalated silicate layers dispersed in the continuous CNBR matrix. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2842–2848, 2001     

Sol–gel preparation and characterization of antibacterial and self-cleaning hybrid nanocomposite coatings

ZnO–TiO₂, SiO₂–TiO₂, and SiO₂–TiO₂–ZnO hybrid nanocomposite coatings were synthesized based on sol–gel precursors including tetramethoxysilane (TMOS), 3-glycidoxypropyl trimethoxysilane (GPTMS), tetra(n-butyl orthotitanate) (TBT), and zinc acetate dihydrate. The hybrid network was characterized by FTIR, FESEM, and EDAX techniques. Results indicated that inorganic particles’ size was of nanoorder (20–30 nm), with very uniform distribution and dispersion. Photocatalytic and self-cleaning activities of these coatings were further investigated by degradation of methylene blue in an aqueous solution (20 ppm) at visible light irradiation, indicating photocatalytic performance of the coatings containing ZnO and TiO₂ nanoparticles. The antibacterial effect of the coatings was investigated for inhibition and inactivation of cell growth, with the results showing the same antibacterial activity for ZnO–TiO₂ and SiO₂–TiO₂–ZnO coatings against Escherichia coli and Staphylococcus aureus; the activity was, however, higher than that of SiO₂–TiO₂ hybrid nanocomposite coatings.     

Structure–property relationship of poly(cyclohexane 1,4-dimethylene terephthalate) modified with high trans-1,4-cyclohexanedimethanol and 2,6-naphthalene dicarboxylicacid

A series of novel poly(1,4-cyclohexanedimthylene terephthalate-co-1,4-cyclohxylenedimethylene 2,6-naphthalenedicarboxylate) (PCTN) copolyesters were successfully melt polymerized using different content of trans- or cis-isomers. Before evaluations, the performance properties, their actual chemical composition, chemical structure, and molecular weight were determined using proton nuclear magnetic resonance (¹H-NMR), Fourier transform infrared spectroscopy (FTIR), and intrinsic viscosity (IV) measurements. Thermal studies of obtained copolyesters were carried out using differential scanning calorimetry (DSC). Thermal degradation behaviors were analyzed by thermogravimetric analysis (TGA). Randomly oriented film specimens were developed using a hot-press and their thermal, barrier, dimensional stability, and optical properties were analyzed and compared with conventional poly(ethylene terephthalate) (PET) and poly(ethylene naphthalate) (PEN). The results revealed that glass transition temperature (T_g), melting temperature (T_m), and crystallinity (X_c) of the synthesized copolyesters are increased in a linear trend by increasing the trans-1,4-cyclohexanedimethanol (trans-CHDM) isomers. It was also found that synthesized films had better thermal, barrier, optical, and dimensional stability properties than conventional PET and PEN films. Results clearly indicated that high trans-CHDM isomers significantly improve the performance properties of the fabricated films. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48950.     

NanoZnO initiated polymerization of N-vinylcarbazole (NVC) and evaluation of a poly(N-vinylcarbazole)–ZnO nanocomposite

The polymerization of N-vinylcarbazole was conducted in bulk in presence of ZnO without any external initiator and a nanocomposite of poly(N-vinylcarbazole)–ZnO (PNVC–ZnO) was isolated from the system. The polymerization of N-vinylcarbazole by ZnO impregnated with acetylene black (AB) and Fe³⁺ was also conducted to isolate the respective AB and Fe³⁺ loaded PNVC–ZnO composites, PNVC–ZnO(AB) and PNVC–ZnO(Fe³⁺). The formation of the poly(N-vinylcarbazole) in these systems was confirmed by FTIR, UV–vis and emission spectroscopic analysis. TGA, DSC and SEM characteristics of these composites were evaluated in details. XRD analysis revealed no crystanillity in poly(N-vinylcarbazole) moiety. PNVC–ZnO was nonconducting but PNVC–ZnO(AB) and PNVC–ZnO(Fe³⁺) systems exhibited conductivities in the range 0.12 and 10⁻³ S/cm respectively. A carbocationic propagation pathway was suggested to explain the initiation of N-vinylcarbazole by Zn⁺⁺ moiety in ZnO. Kinetic studies revealed that the polymerization is first order with respect to ZnO and the monomer concentration respectively.     

Development of moisture cure polyurethane–urea coatings using 1,2,3-triazole core hyperbranched polyesters

This article reports the development of moisture cure polyurethane–urea coatings. The coating has been developed using different generations of novel 1,2,3-triazole core containing hyperbranched polyester polyols (THBP). For the synthesis of THBP, the core molecule, tetra hydroxyl-terminated di-triazole (THTD), has been synthesized by click reaction involving ethylene diazide and 2-butyne-1,4-diol. The polycondensation reaction between the core THTD and 2,2-bis (hydroxymethyl) propionic acid (Bis-MPA) at different mole ratios has been used to get first (THBPG-1), second (THBPG-2), and third (THBPG-3) generations of triazole core hyperbranched polyesters. The structural investigations of these THBPs have been carried out by ¹H NMR, ¹³C NMR, and FTIR spectroscopy. The different generations of THBPs were further reacted with 1-isocyanato-4-[(4-isocyanatocyclohexyl) methyl] cyclohexane (H₁₂-MDI) at OH:NCO ratio of 1:1.2 to get –NCO terminated triazole core hyperbranched polyurethanes. They were cured under atmospheric moisture to get hyperbranched polyurethane–urea coatings and were named as THBPUG-1, THBPUG-2, and THBPUG-3. FTIR has been used to confirm the formation of polyurethane coatings. The TGA and DMTA have been used to determine the thermal stability and dynamic mechanical properties of the coatings, respectively. The corrosion resistance properties of the coatings have been studied by salt spray and electrochemical test. The coatings were also evaluated for microbial resistance. The results indicate that the thermal stability, glass transition temperature, and corrosion resistance properties increase with an increase in generation number of THBPs used for coating development. All three generations of coating films show excellent antimicrobial activity. Based on overall combined structure–property relationship study, these types of coatings will be useful as multifunctional applications in marine and moist environments.     

Melting and crystallization behaviors of compatibilized poly(trimethylene terephthalate)/acrylonitrile–butadiene–styrene blends

The melting and crystallization behaviors of poly(trimethylene terephthalate) (PTT)/acrylonitrile–butadiene–styrene (ABS) blends were investigated with and without epoxy or styrene–butadiene–maleic anhydride copolymer (SBM) as a reactive compatibilizer. The existence of two separate composition-dependent glass-transition temperatures (T_g's) indicated that PTT was partially miscible with ABS over the entire composition range. The melting temperature of the PTT phase in the blends was also composition dependent and shifted to lower temperatures with increasing ABS content. Both the cold crystallization temperature and T_g of the PTT phase moved to higher temperatures in the presence of compatibilizers, which indicated their compatibilization effects on the blends. A crystallization exotherm of the PTT phase was noticed for all of the PTT/ABS blends. The crystallization behaviors were completely different at low and high ABS contents. When ABS was 0–50 wt %, the crystallization process of PTT shifted slightly to higher temperatures as the ABS content was increased. When ABS was 60 wt % or greater, PTT showed fractionated crystallization. The effects of both the epoxy and SBM compatibilizers on the crystallization of PTT were content dependent. At a lower contents of 1–3 wt % epoxy or 1 wt % SBM, the crystallization was retarded, whereas at a higher content of 5 wt %, the crystallization was accelerated. The crystallization kinetics were analyzed with a modified Avrami equation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008