Preparation of polybenzimidazole/functionalized carbon nanotube nanocomposite films for use as protective coatings

Functionalized multi‐walled carbon nanotubes (MWCNTs) via microwave‐induced polymerization modification route, and polybenzimidazole (PBI) nanocomposite films containing 0.1‐5 wt% functionalized MWCNTs were successfully synthesized. The functionalized MWCNTs were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and X‐ray photoelectron spectroscopy (XPS). The results verify that the polymer was successfully grafted to the MWCNTs with a polymer layer that was several nanometers thick. The TGA results showed that the quantity of the attached polymer reached approximately 9.4 wt%. The mechanical properties of the nanocomposite films were measured by tensile test and dynamic mechanical analysis (DMA). The tensile test results indicated that the Young's modulus increased by about 43.9% at 2 wt% CNT loading, and further modulus growth was observed at higher filler loading. The DMA studies indicated that the nanocomposite films had a higher storage modulus than pure PBI film in the temperature range of 30‐300°C, and the storage modulus was maintained above 0.82 GPa. Simulation results confirmed that the PBI nanocomposite films had desirable mechanical properties for use as a protective coating. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers.     

Mechanical,thermal, and electrical conducting properties of CNTs/bio‐degradable polymer thin films

The objective of this study is to increase mechanical, thermal, and electrical properties of plasticizer free thermoplastic bio polymer, BIOPLAST GS 2189 (BP), a blend of poly lactic acid (PLA) and potato starch. This polymer is highly suitable for sheet molding, film processing; blown film extrusion and injection molding and fully biodegradable. Structural, mechanical, thermal, and electrical properties of these films were manipulated by reinforcement of multiwalled carbon nanotubes (CNTs) in BP. Thin films of various (1–5 wt %) percentages of CNTs/BP were prepared by using a high‐speed spin coating technique. These as‐prepared films are ～60–100 µm in thickness. The thickness measurements of these films were carried out using micrometry and optical microscopy. The maximum tensile strength (200%) and modulus (150%) was observed for 4 wt % loading of CNTs in BP as compared with the neat BP thin film. The X‐ray diffraction results show that the addition of CNTs in BP increases the crystallinity of BP. Electrical conductivity of this film also increased by 48% as compared with the neat BP polymer films. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Fabrication of starch‐g‐poly(l‐lactic acid) biocomposite films: Effects of the shear‐mixing and reactive‐extrusion conditions

In this study, we developed a new approach for the fabrication of a green poly(l ‐lactic acid)‐grafted starch (St‐g‐PLA) copolymer and nanocomposite (St‐g‐PLA/organoclay)‐based films via shear‐mixing and reactive‐extrusion systems. The chemical and physical structures, thermal behavior, and morphology of the synthesized blends and some other parameters were examined by Fourier transform infrared spectroscopy and ¹³C cross‐polarization/magic angle spinning NMR spectroscopy, X‐ray diffraction, thermogravimetric analysis–derivative thermogravimetry, and scanning electron microscopy, respectively. Significant increases in the mechanical and permeability properties were evident in the high value of grafted poly(lactic acid) molar percentages and high exfoliation of organoclay. The biodegradability of films were investigated under aerobic composting conditions through the measurement of the temperature, moisture, pH, consumed O₂ value, and carbon dioxide produced. This new strategy mainly improved the good adhesion between both phases, and it was an interesting method for the production of environmentally friendly biocomposites that could easily be scaled up for commercial production with the potential for replacing petroleum‐based plastics. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44490.     

Photocurable epoxy/cubic silsesquioxane hybrid materials for polythiourethane: Failure mechanism of adhesion under weathering

A new inorganic–organic hybrid coating containing epoxy‐functionalized cubic silsesquioxane (CSSQ) has been developed, which can be polymerized cationically by UV radiation. This solvent‐free solution can be used as hybrid coating for polythiourethane (PTU) substrate. The surface properties of the coating film were determined by adhesion and scratch resistance. The excellent adhesion of coating films on the substrate was observed at the initial stage before weathering, but deteriorated after exposure to the sunshine. The low viscosity of hybrid coating solution (～ 15 mPa s) leads to fast curing and the formation of hybrid coating film during the photopolymerization reaction. The adhesion failure was evaluated by atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), and X‐ray photoelectron spectroscopy (XPS) analyses. AFM images showed that the surface is smooth at the initial stage, but a texture surface was developed after weathering. The shrinkage of the hybrid film due to the increase in crosslinking density by postpolymerization would affect the surface roughness after weathering. XPS analysis indicated that the adhesion failure occurred by photodegradation of the PTU substrate during weathering. The weathering resistance was significantly improved by adding UV absorbers, which protected the polymer substrate from the photodegradation. The advantages of the hybrid coating include fast cure speed, solvent‐free formulation, and improved surface properties of the coating film. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Influence of the spinning conditions on the structure and properties of polyamide 12/carbon nanotube composite fibers

The inclusion of nanoparticles in polymer fibers is potentially useful for improving or bringing new properties such as mechanical strength, electrical conductivity, piezoresistivity, and flame retardancy. In this study, composite fibers made of polyamide 12 and multiwall carbon nanotubes were investigated. The fibers were spun via a melt‐spinning process and stretched at different draw ratios. The influence of several spinning factors, including spinning speed, extrusion rate, and draw ratio were investigated and correlated to the structure and properties of the fibers. X‐ray diffraction analyses and mechanical tests indicated that the spinning speed barely affected the structure and mechanical properties of the fibers under tension. The spinning speed, however, is critical for future industrial applications because it determines the possible production rates. By contrast, drawing during spinning or after spinning strongly affected the polymer chain alignment and fiber mechanical properties. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Heat‐sealing properties of soy protein isolate/poly(vinyl alcohol) blend films: Effect of the heat‐sealing temperature

To promote the heat‐sealing properties of soy protein isolate (SPI) films applied in the packaging field, we mixed a synthetic polymer of poly(vinyl alcohol) (PVA) with SPI to fabricate blend films by a solution‐casting method in this study. To clarify the relationship between the heat‐sealing properties and the heat‐sealing temperature, strength, melting process, crystalline structure, and microstructure, variations of the heat‐sealing parts of the films were evaluated by means of differential scanning calorimetry, tensile testing, scanning electron microscopy, X‐ray diffraction, and Fourier transform infrared spectroscopy, respectively. The test results showed that both the PVA and glycerol contents greatly affected the melting behavior and heat of fusion of the SPI/PVA blends; these blend films had a higher melting temperature than the pure SPI films. The peel strength and tensile strength tests indicated that the long molecular chain of PVA had a main function of enhancing the mechanical properties above the melting temperature. With increasing heat‐sealing temperature, all of the mechanical properties were affected by the microstructure of the interface between the laminated films including the chain entanglement, crystallization, and recrystallization. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Extrusion of polyethylene/polypropylene blends with microfibrillar‐phase morphology

Extrusion of immiscible polymers under special conditions can lead to creation of microfibrillar‐phase morphology, ensuring significant increase of mechanical properties of polymer profiles. Polyethylene/polypropylene blend extrudates with microfibrillar‐phase morphology (polypropylene microfibrils reinforcing polyethylene matrix phase) were prepared through continuous extrusion with semihyperbolic‐converging die enabling elongation and orientation of microfibrils in flow direction. Structure of extruded profiles was examined using electron microscopy and wide‐angle X‐ray scattering. Tensile tests proved that extrudates with microfibrillar‐phase morphology show significantly higher mechanical properties than the conventional extrudates. The presented concept offers possibility of replacing the existing expensive multi‐component medical devices with fully polymeric tools. POLYM. COMPOS., 31:1427–1433, 2010. © 2009 Society of Plastics Engineers     

Polymeric carbon nanocomposites from multiwalled carbon nanotubes functionalized with segmented polyurethane

Multiwalled carbon nanotubes (MWNT) were functionalized with segmented polyurethanes (PU) by the “grafting to” approach. Raman and X‐ray photoelectron spectroscopy (XPS) spectra show that the sidewalls of MWNTs have been functionalized with acid treatment, and the amount of COOH increases with increasing acid treatment time. FTIR and X‐ray diffraction (XRD) spectra confirm that PU is covalently attached to the sidewalls of MWNTs by esterification reaction. Similar to the parent PU, the functionalized carbon nanotube samples are soluble in highly polar solvents, such as dimethyl sulfoxide (DMSO) and N,N‐dimethylformamide (DMF). The functionalized acid amount and the grafted PU amount were determined by thermogravimetric analyses (TGA). Comparative studies, based on SEM images between the PU‐functionalized and chemically defunctionalized MWNT samples, also reveal the covalent coating character. Dynamic mechanical analysis (DMA) of nanocomposite films prepared from PU and PU‐functionalized MWNTs show enhanced mechanical properties and increased soft segment T_g. Tensile properties indicate that PU‐functionalized MWNTs are effective reinforcing fillers for the polyurethane matrix. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Preparation and characterization of transparent poly(methyl methacrylate)/Na+‐MMT nanocomposite films by solution casting

Films of poly(methyl methacrylate) (PMMA)/sodium montmorillonite (Na⁺‐MMT) nanocomposites have been successfully prepared utilizing Na⁺‐MMT by N,N‐dimethylformamide solution casting. The nanocomposite films show high transparency, enhanced thermal resistance, and mechanical properties in comparison with the neat polymer film. The transparency of the films was investigated by UV‐vis spectra. The exfoliated dispersion of Na⁺‐MMT platelets in nanocomposites were investigated by X‐ray diffraction and transmission electron microscopy. The enhanced thermal resistance and mechanical properties of PMMA were studied by thermal gravimetric analysis and dynamic mechanical analysis, respectively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Modification and extrusion coating of polylactic acid films

Polyethylene (PE) extrusion coating on paper substrates are the traditional packing material for coffee cups and take‐out food containers. It is difficult to recycle the PE/paper laminates and the thin polymer films remain in landfills after the decomposition of their paper substrates. Disposal of plastic materials is causing serious effects on our environment and wildlife. Demand for compostable or biodegradable plastic packaging products is increasing because of consumer pressure and legislation. Biodegradable polylactic acid (PLA) is regarded as one of the most promising biopolymers with a large market potential, but its applications are limited by poor thermal stability, mechanical properties and processibility. We utilize modified gelatin as additives to improve PLA's performance without compromizing the biomass origin and compostable properties of the material. Extrusion coating, or extrusion casting, of polylactic acid (PLA) films onto paper substrates to form PLA/paper laminates was achieved by modification of the polymer with a plant or animal gelatin. Various paper substrates with thin PLA coatings were prepared using a conventional extrusion coating equipment for the fabrication of take‐out food containers and coffee cups. Melt rheology of PLA and adhesion of the resulting thin film were greatly improved in the presence of a small amount of gelatin in the polymer matrices. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42472.     

Preparation and characterization of grafting polyacrylamide from PET films by SI‐ATRP via water‐borne system

The grafted homopolymer and comb‐shaped copolymer of polyacrylamide were prepared by combining the self‐assembly of initiator and water‐borne surface‐initiated atom transfer radical polymerization (SI‐ATRP). The structures, composition, properties, and surface morphology of the modified PET films were characterized by FTIR/ATR, X‐ray photoelectron spectroscopy (XPS), contact angle measurement, and scanning electronic microscopy (SEM). The results show that the surface of PET films was covered by equable grafting polymer layer after grafted polyacrylamide (PAM). The amount of grafting polymer increased linearly with the polymerization time added. The GPC date show that the polymerization in the water‐borne medium at lower temperature (50°C) shows better “living” and control. After modified by comb‐shaped copolymer brushes, the modified PET film was completely covered with the second polymer layer (PAM) and water contact angle decreased to 13.6°. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Insulating polyimide films containing n‐type perylenediimide moieties

Oxadiazole‐containing polyperyleneimides were prepared by high‐temperature solution polycondensation reaction of an aromatic diamino‐oxadiazole with a mixture of two dianhydrides, one containing a perylene moiety and the other containing a hexafluoroisopropylidene unit. Flexible films having good mechanical properties were made therefrom. The structure of the polymer films was confirmed using X‐ray photoelectron spectroscopy. Some polymer films were subjected to measurements of electrical insulating properties. The variation of the real and imaginary parts of the dielectric permittivity with frequency and temperature was recorded. The values of the dielectric constant, dielectric loss and specific resistance were obtained at 25 °C and in the frequency domain from 1 Hz to 130 kHz. The dielectric spectroscopy data showed distinct γ and β subglass transitions for these polymers at low activation energies. Electronic conduction through a hopping mechanism in these polyimide films was determined from AC conductivity measurements. Copyright © 2012 Society of Chemical Industry     

Chemical grafting of sulfobetaine onto poly(ether urethane) surface for improving blood compatibility

Poly(ether urethane)s (PEUs) are widely used as blood‐contact biomaterials because of their good biocompatibility and mechanical properties. Nevertheless, their blood compatibility is still not adequate for more demanding applications. Surface modification is an effective way to improve blood compatibility and retain bulk properties of biomaterials. The purpose of the present study was to design and synthesis a novel non‐thrombogenic biomaterial by modifying the surface of PEU with zwitterionic monomer. In this study, sulfobetaine was grafted onto PEU surface through the following reaction steps: (1) Poly(propylene oxide) (PPO) was reacted at both chain ends with hexamethylene diisocyanate (HDI), and OCN–PPO–NCO was obtained; (2) OCN–PPO–NCO was reacted at one chain end with N,N‐dimethylethanolamine (DMEA) and OCN–PPO–N(CH₃)₂ was formed; (3) the sulfobetaine was prepared by a ring‐opening reaction between OCN–PPO–N(CH₃)₂ and 1,3‐propanesultone (PSu); (4) the sulfobetaine was grafted onto PEU surface by the reaction between NCO and the N–H bonds of PEU. The surface composition of films and the hydrophilicity on the PEU surface were investigated by X‐ray photoelectron spectroscopy analysis and contact angle measurements, respectively. The blood compatibility of PEU was evaluated by platelet‐rich plasma contact experiments and the results were observed by scanning electron microscopy. The state of platelet adhesion and shape variation for the attached platelets was described. The modified surface showed excellent blood compatibility, featured by low platelet adhesion. Copyright © 2003 Society of Chemical Industry     

Axial‐feed thermoforming of oriented polypropylene tubes

The effect of newly developed axial feed thermoforming process (AFTF) on mechanical properties and morphology were investigated to gain a better understanding of structure–properties–process relationship. The starting material for AFTF is an oriented polypropylene tube (OPP) produced in uniaxial direction by using solid state extrusion process. Morphological changes from solid‐state extrusion are briefly reported. A die‐less bulge testing system was designed to bulge OPP tube at a high temperature in biaxial direction. Wide‐angle X‐ray diffraction, field emission scanning electron microscope, and optical microscopy were used to characterize the microstructure of the extruded and bulged samples of OPP. In addition, tensile tests were carried out at room temperature of samples machined from the extruded and bulged tubes along the axial and hoop directions. The results show that tensile strength increases with draw ratio in extruded samples as well as improvements in ductility were obtained in die‐less bulge tests with an increase in axial feed. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Comparative studies of polypropylene nonwoven sputtered with ITO and AZO

In this study, the polypropylene (PP) spunbonded nonwoven materials were used as substrates for depositing transparent nanostructures on the fiber surfaces. Magnetron sputter coating technique was used to deposit tin‐doped indium oxide (ITO) and aluminum‐doped zinc oxide (AZO) films onto the nonwoven substrates. The structures and properties of the deposited ITO and AZO films were investigated and compared using atomic force microscopy, energy‐dispersive X‐ray (EDX), and electrical and optical tests. The observations by atomic force microscopy revealed the formation of functional nanostructures on the fiber surfaces. EDX analyses confirmed the deposition of ITO and AZO functional films on the PP fibers. It was found that ITO had more compact structures on the fiber surface than AZO under the same sputtering conditions. The transmittance analysis revealed that the nonwoven substrates deposited with nanostructural AZO showed better ultraviolet shielding effect than those coated with ITO in the same thickness. The nonwoven materials coated with ITO had lower electrical resistance than those coated with AZO in the same thickness. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of the degree of clay delamination on the phase morphology,surface chemical aspects,and properties of hydrolyzable polyurethanes for periodontal regeneration

In recent years, there has been increased interest in biodegradable polyurethanes for use in regenerative medicine because of their versatility and biocompatibility. Nevertheless, these polymers are usually produced using organic solvents that can lead to the release of toxic components. In this work, polyurethane/montmorillonite nanocomposites were designed to work as guided tissue regeneration membranes to treat periodontal diseases. Polyurethanes were synthesized in an aqueous environment. The composition, morphology, and mechanical properties of the biomaterials were evaluated. The cellular viability, proliferation, and morphology changes of rat culture cementoblasts were also investigated using a montmorillonite assay. Small‐angle X‐ray scattering, X‐ray diffraction, and infrared spectroscopy results showed that the degree of clay delamination within the polymer was able to tailor the phase morphology of the polymer, the chemical aspects of the surface, the mechanical properties, and the kinetics of hydrolysis of the materials. The produced scaffolds provided a good environment for the adhesion and proliferation of cementoblasts and thus can be considered suitable biomaterials for participating in procedures associated with periodontal regeneration. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation of Fe/Al Composites with Enhanced Thermal Properties by Chemical Liquid Deposition Methods

Core‐shell Fe/Al composites were successfully prepared by chemical liquid deposition with iron carbonyl [Fe(CO)₅] as precursor and kerosine as oil phase medium. Scanning electron microscopy (SEM), X‐ray diffractometer (XRD), and simultaneous thermogravimetry‐differential thermal analysis (TG‐DTA) were employed to characterize the samples and assess their thermal properties. The results indicated that the aluminum core was coated compactly by an iron layer and the the oxidation kinetics of the obtained composite powders showed a significant improvement compared to pure aluminum powders. The thermal reactivity of Fe/Al composites with oxygen is obviously higher than those of pure aluminum powders, which means that after coating much more heat can be released in the same temperature range and the heat release happens faster and more concentrated. On the basis of the results, a possible formation of the coating is proposed and a thermal reaction mechanism is also discussed.     

Reactive coupling between immiscible polymer chains: Acceleration by compressive flow

It is demonstrated that processing flow affects the kinetics of the interfacial coupling reaction between functional groups that are grafted to polymer chains. At melt temperatures the amine group on the end of nylon 6 chains reacts with maleic anhydride grafted polyethylene (PE‐MA) and forms graft copolymers. Bilayers were made by lamination and coextrusion and adhesion was measured using asymmetric dual cantilever beam (ADCB). The amount of graft copolymer in the interface was quantified by X‐ray photon spectroscopy (XPS). With quiescent lamination, adhesion increased with temperature and the concentration of PE‐MA. The adhesion metric, G_c (critical energy release rate), plotted as a function of Σ (interfacial copolymer density) fell on the same master curve, unifying reaction process, temperature and time. G_c was a linear function of Σ for low‐copolymer coverage and weak adhesion. For relatively high coverage and strong adhesion, G_c scaled with Σ. 2 Coextrusion with compressive flow resulted in a reaction rate strikingly two‐orders of magnitude faster than that without compressive flow. The rate in the noncompressive die was close to quiescent lamination. Even for lamination, when compressive flow was applied normal to the interface, the coupling reaction rate was also greatly accelerated. Several mechanisms are speculated for this remarkable acceleration in polymer chain coupling. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3391–3402, 2013     

Improved adhesion of silicone rubber to polyurethane by surface grafting

Polyurethane (PU) has widespread applications in implantable devices because of its excellent mechanical and biocompatible properties, whereas weak biostability limits its long‐term implantation. The introduction of silicone rubber (SR) onto the PU surface is an effective method for improving the biostability of PU, but the adhesion of these two polymers is unsatisfactory. In this study, the surface modification of PU via grafting through the introduction of vinyl and Si H groups onto the PU surface was attempted to improve the adhesion of PU to SR. Fourier transform infrared, energy‐dispersive X‐ray spectroscopy, and X‐ray photoelectron spectroscopy were employed to investigate the graft reaction on the PU surface. The interfacial and surface morphology was characterized with scanning electron microscopy. Different PU/SR interfaces after oscillation and shear were compared as well. The results indicated that the PU surface was activated by diisocyanate, which generated free isocyanate groups for the further grafting of vinyl and Si H groups. When addition‐type, room‐temperature‐vulcanized SR was poured onto the PU surface, the vinyl and Si H groups on the PU surface underwent an addition reaction, which improved the adhesion of PU and SR by connecting them with chemical bonds. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

The tribological characteristics of phosphorylated 3‐aminopropyltriethoxysilane nanometer film

Thin films deposited on the phosphonate 3‐aminopropyltriethoxysilane (APTES) self‐assembled monolayer (SAM) were prepared on the hydroxylated silicon substrate by a self‐assembling process from specially formulated solution. Chemical compositions of the films and chemical state of the elements were detected by X‐ray photoelectron spectrometry. The thickness of the films was determined with an ellipsometer, whereas the morphologies and nanotribological properties of the samples were analyzed by means of atomic force microscopy. As the results, the target film was obtained and reaction may have taken place between the thin films and the silicon substrate. It was also found that the thin films showed the lowest friction and adhesion followed by APTES‐SAM and phosphorylated APTES‐SAM, whereas silicon substrate showed high friction and adhesion. Microscale scratch/wear studies clearly showed that thin films were much more scratch/wear resistant than the other samples. The superior friction reduction and scratch/wear resistance of thin films may be attributed to low work of adhesion of nonpolar terminal groups and the strong bonding strength between the films and the substrate. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009