Fractal analysis of polypropylene composite filled with nano‐calcium carbonate

Polypropylene (PP) and nano‐calcium carbonate (CaCO₃) composites were prepared by melt mixing in a corotating twin‐screw extruder. Transmission electron microscopy study and particle size analysis revealed the dispersion and the size distribution of CaCO₃ in PP. With the increase of loading of filler, CaCO₃ nanoparticles densely aggregated together and the dispersion of filler became bad. The fractal dimensions of the composites were determined using fractal concept. The fractal dimensions of D and D_k described the irregularities of the shape of an object and the distributions of particle populations, respectively. The D and D_k values were influenced by the content of filler, i.e., the D values increased, and the D_k values decreased with the increase of loading of filler. When the loading of filler was low, the values of D and D_k of PP composites differ slightly than the counterparts of PP/PP‐g‐MA (50 wt %) blend. For 20 wt %, they were almost identical. This fact showed that the fractal dimension was correlated with the dispersion. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Fabrication and characterization of in situ synthesized nano‐CaCo3‐reinforced polypropylene composite materials

To improve the impact toughness of polypropylene (PP), nano‐CaCO₃ was prepared by an in situ synthesis. The surface of the nano‐CaCO₃ was modified by KH‐550 silane coupling agent and NDZ‐401 titanium acid ester coupling agent. Nano‐CaCO₃/PP composite materials were fabricated through a melt‐blending method and characterized, and their mechanical properties were analyzed. The impact toughness and the tensile strength of the PP were improved significantly by the incorporation of nano‐CaCO₃. When the weight fraction of nano‐CaCO₃ was 2%, the maximum impact toughness and tensile strength of the PP nanocomposites were 293% and 259%, respectively, of the values for neat PP. Observation of the impact fracture surface of the nanocomposites indicated that the dispersion of nano‐CaCO₃ modified by NDZ‐401 coupling agent was more homogeneous than that of nano‐CaCO₃ modified by the KH‐550 silane coupling agent. J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers     

A study on the preparation of polymer/montmorillonite nano‐composite materials by photo‐polymerization

The preparation of polymer/montmorillonite intercalation composite materials was studied by two kinds of photo‐polymerization reaction (photo‐acid generation and photo‐radical generation). Small‐angle X‐ray diffraction was used for the structural characterization of montmorillonite contained in the products. Results indicated that, after chemical modification of montmorillonite, the monomer (methyl methacrylate) and the prepolymer (m‐cresol/HMMM) were able to intercalate into the layers of clay and to polymerize ‘in situ’, thus producing photo‐polymerized composite materials. The advantages and shortcomings of the method of photo‐polymerization for the preparation of these composite materials are discussed. © 2001 Society of Chemical Industry     

Controlled freezing and freeze drying: a versatile route for porous and micro‐/nano‐structured materials

Freeze drying is a process whereby solutions are frozen in a cold bath and then the frozen solvents are removed via sublimation under vacuum, leading to formation of porous structures. Pore size, pore volume and pore morphology are dependent on variables such as freeze temperature, solution concentration, nature of solvent and solute, and the control of the freeze direction. Aqueous solutions, organic solutions, colloidal suspensions, and supercritical CO₂ solutions have been investigated to produce a wide range of porous and particulate structures. Emulsions have recently been employed in the freeze drying process, which can exert a systematic control on pore morphology and pore volume and can also lead to the preparation of organic micro‐ and nano‐particles. Spray freezing and directional freezing have been developed to form porous particles and aligned porous materials. This review describes the principles, latest progress and applications of materials prepared by controlled freezing and freeze drying. First of all the basics of freeze drying and the theory of freezing are discussed. Then the materials fabricated by controlled freezing and freeze drying are reviewed based on their morphologies: porous structures, microwires and nanowires, and microparticles and nanoparticles. The review concludes with new developments in this area and a brief look into the future. Copyright © 2010 Society of Chemical Industry     

Thermal interaction between polymer‐based composite friction materials and counterfaces

Attempts have been made to improve the performance of polymeric composite friction materials for eliminating undesirable mechanical and thermal effects on the opposing surfaces. Elastic compression modulus and thermal conductivity of the moulded friction materials were found to be the most effective parameters upon the thermal interaction between the disc and brake pad. Effects of elastic modulus on temperature accumulation of the interface have also been studied. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 364–369, 2001     

Comparative studies on corrosion protection properties of polyimide‐silica and polyimide‐clay composite materials

Comparative studies on corrosion protection properties of polyimide‐silica‐clay composites were studied in this article. A series of polyimide‐silica (PIS), polyimide‐clay (PIC), and polyimide‐silica‐clay composites (PISC) materials, consisting of an organo‐soluble polyimide (ODA‐BSAA) matrix, inorganic silica particles prepared through the sol–gel reaction of tetraethyl orthosilicate (TEOS) and dispersed nanolayers of inorganic montmorillonite clay, were successfully prepared by solution dispersion technique. Then, all samples were characterized by FTIR, powder X‐ray diffraction patterns, transmission electron microscopy, and ²⁹Si solid‐state NMR. The main focus of this article is the comparison of the corrosion protection properties of PIS, PIC, and PISC composite materials. Normally, the aspect ratio of clay is higher than silica. Superior dispersion of clay platelets into a polymer matrix may effectively increase the length of diffusion pathways for oxygen and water. The effects of the materials composition on the corrosion protection performance, gas barrier, and optical properties, in the form of both coating and film, were also studied by electrochemical corrosion measurements (e.g., corrosion potential, polarization resistance, corrosion current, and impedance spectroscopy), gas permeability analysis, and UV‐visible transmission spectroscopy. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

The influence of interphase on nylon‐6/nano‐SiO2 composite materials obtained from in situ polymerization

Three commercially available silane, titanate and aluminate based coupling agents were used to pretreat nano‐SiO₂ for the preparation of nylon‐6/nano–SiO₂ composites via in situ polymerization. The interphases formed in different composite systems and their influence on material properties were investigated. Results indicated that the interfacial interactions differed between composite systems, whereas rigidity and toughness of composites were all improved by addition of pretreated silicas at an optimal content of 4.3 wt%. The presence of pretreated silicas did not have a distinct influence in the non‐isothermal crystallization behaviour of the nylon matrix. The composites containing pretreated silicas had slightly higher dynamic viscosities and superior storage moduli at high frequency, compared with neat nylon‐6. Copyright © 2003 Society of Chemical Industry     

Solid‐state synthesis and characterization of polyaniline/nano‐TiO2 composite

Polyaniline/nano‐TiO₂ composites with the content of nano‐TiO₂ varying from 6.2 wt % to 24.1 wt % were prepared by using solid‐state synthesis method at room temperature. The structure and morphology of the composites were characterized by the Fourier transform infrared (FTIR) spectra, ultraviolet‐visible (UV–vis) absorption spectra, X‐ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The electrochemical performances of the composites were investigated by galvanostatic charge–discharge measurement, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The results from FTIR and UV–vis spectra showed that the composites displayed higher oxidation and doping degree than pure PANI. The XRD and morphological studies revealed that the inclusion of nano‐TiO₂ particles hampered the crystallization of PANI chains in composites, and the composites exhibited mixed particles from free PANI particles and the nano‐TiO₂ entrapped PANI particles. The galvanostatic charge–discharge measurements indicated that the PANI/nano‐TiO₂ composites had higher specific capacitances than PANI. The composite with 6.2 wt % TiO₂ had the highest specific capacitance among the composites. The further electrochemical tests on the composite electrode with 6.2 wt % TiO₂ showed that the composite displayed an ideal capacitive behavior and good rate ability. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Coincorporation of nano‐silica and nano‐calcium carbonate in polypropylene

In this study, various polypropylene (PP) nanocomposites were prepared by melt blending method. The effects of different spherical nanofillers, such as 50 nm CaCO₃ and 20 nm SiO₂, on the linear viscoelastic property, crystallization behavior, morphology and mechanical property of the resulting PP nanocomposites were examined. Rheological study indicated that coincorporation of nano‐SiO₂ and nano‐CaCO₃ favored the uniform dispersion of nanoparticles in the PP matrix. Differential scanning calorimeter (DSC) and polarizing optical microscopy (POM) studies revealed that the coincorporation of SiO₂ and CaCO₃ nanoparticles could effectively improve PP crystallizability, which gave rise to a lower supercooling temperature (ΔT), a shorter crystallization half‐life (t_1/2) and a smaller spherulite size in comparison with those nanocomposites incorporating only one type of CaCO₃ or SiO₂ nanoparticles. The mechanical analysis results also showed that addition of two types of nanoparticles into PP matrix gave rise to enhanced performance than the nanocomposites containing CaCO₃ or SiO₂ individually. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Mechanical and antibacterial properties of modified nano‐ZnO/high‐density polyethylene composite films with a low doped content of nano‐ZnO

Nano‐ZnO/high‐density polyethylene (HDPE) composite films were prepared via melt blending and a hot compression‐molding process. The properties, including ultraviolet absorption, mechanical and antibacterial properties of the films, and plasticizing behavior of the composites, were investigated. The results show that the absorbance in the ultraviolet region of the HDPE films was enhanced after the addition of modified nano‐ZnO to the HDPE matrix. Also, we found that improvement in the HDPE films of the tensile strength and elongation at break was achieved by the incorporation of modified ZnO nanoparticles up to 0.5 wt % in contrast with the original nano‐ZnO/HDPE composite films. Antibacterial testing was carried out via plate counting, and the results indicate that the HDPE films doped with modified ZnO nanoparticles showed favorable antibacterial activity, especially for Staphylococcus aureus. However, the low doped content of modified nano‐ZnO in the HDPE matrix made the balance torque of the composites increase slightly. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation of the composite consisting of nano‐sized gold particles and nylon‐11 oligomer

Nylon‐11 oligomer was utilized as a matrix to prepare a composite containing nano‐sized gold particles. Nylon‐11 oligomer was prepared by a thermal degradation of a commercial nylon‐11 in vacuum. Weight‐average molecular weight of the oligomer was in a range from 500 to 800. Nylon‐11 oligomer was formed into a film, and then gold was vapor‐deposited onto the oligomer film. The gold‐colored oligomer film turned a transparent red after a heat treatment at 120°C. Transmission electron microscopy showed an isolated distribution of nano‐sized gold particles in the red film of the oligomer. The gold particles were stable in the oligomer for more than a year, and they were dissolved in CH₂Cl₂ to produce a stable colloidal solution. These results suggest that the gold particles were not only dispersed in the oligomer film, but they were stabilized by the nylon‐11 oligomer to form a composite. IR spectrum of the composite showed that N H groups of the nylon‐11 oligomer were responsible for the interaction between the gold particles and the oligomer. Pulse ¹H‐NMR measurement suggested that an active molecular motion of the nylon‐11 oligomer caused the dispersion of the gold particles. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1654–1661, 1999     

Antimicrobial carbon materials incorporating copper nano‐crystallites and their PLA composites

In the first stage, carbon materials were manufactured from chitin and chitosan as the main precursor. Chitin and chitosan were impregnated with Cu²⁺ ions. Using heat treatment, the organic matter (biopolymers) was transformed into a porous carbon matrix, while copper ions were transformed into copper‐based nano‐crystallites containing copper atoms in a +1 and 0 oxidation state. Such synthesized carbons exhibited high contact antifungal activity, e.g., for sample, CH‐ACu0.1_Ox against R. nigricans the inhibition zone is 10.27 mm. In the second stage, composite polymer films were manufactured by mixing polylactide (PLA) and the obtained microbial carbon material (up to 3 wt % Cu‐carbon content). Despite the very low content of carbon material (3 wt %), the composite PLA films exhibited excellent microbial properties for selected bacteria and fungi, e.g., sample CuCM3%/PLA demonstrated high log₁₀ reduction values of 2.17 and 2.66 for the strains of E. coli and S. aureus, respectively. The composite films, and their components, were examined by means of diversified physicochemical methods like low temperature adsorption of nitrogen, SEM, elemental analysis, XRD, cyclic voltammetry, antifungal, and antibacterial analysis. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43429.     

Preparation and evaluation of nano‐epoxy composite resins containing electrospun glass nanofibers

In this study, electrospun glass (structurally amorphous SiO₂) nanofibers (EGNFs) with diameters of ～ 400 nm were incorporated into epoxy resin for reinforcement and/or toughening purposes; the effects of silanization treatment (including different functional groups in silane molecules) and mass fraction of EGNFs on strength, stiffness, and toughness of the resulting nano‐epoxy composite resins were investigated. The experimental results revealed that EGNFs substantially outperformed conventional glass fibers (CGFs, with diameters of ～ 10 μm) in both tension and impact tests, and led to the same trend of improvements in strength, stiffness, and toughness at small mass fractions of 0.5 and 1%. The tensile strength, Young's modulus, work of fracture, and impact strength of the nano‐epoxy composite resins with EGNFs were improved by up to 40, 201, 67, and 363%, respectively. In general, the silanized EGNFs with epoxy end groups (G‐EGNFs) showed a higher degree of toughening effect, while the silanized EGNFs with amine end groups (A‐EGNFs) showed a higher degree of reinforcement effect. The study suggested that electrospun glass nanofibers could be used as reinforcement and/or toughening agent for making innovative nano‐epoxy composite resins, which would be further used for the development of high‐performance polymer composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of nano‐SiO2 on granule characteristic and fusion process of Poly(vinyl chloride‐co‐vinyl acetate)/nano‐SiO2 composite resin

Poly(vinyl chloride‐co‐vinyl acetate) (PVVA)/nano‐SiO₂ composite resin was prepared by radical suspension polymerization of the monomers in the presence of fumed nano‐SiO₂ particles premodified with γ‐methylacryloxypropyl trimethoxysilane. The cool dioctyl phthalate absorption percentage, granule porosity, and specific surface area of the composite resin were enhanced through incorporation of nano‐SiO₂ into the PVVA. Scanning electron microscope pictures showed the resin had higher porosity. PVVA/nano‐SiO₂ composite resin was mixed with pure PVC resin to form a mixture sample (polymer‐composite blend [PCB]) and the mixture was fused in the torque rheometer. The rheological test results indicated that, at a certain nano‐SiO₂ content, the fusion speed of PCB was accelerated and the fusion temperature of PCB was decreased, owing to nano‐SiO₂ dispersed evenly in the polymer matrix. When excessive nano‐SiO₂ was loaded, the fusion torque, the fusion time, and the fusion temperature of PCB were all increased. These properties are correlative to the dispersive density of nano‐SiO₂ in the polymer matrix. This study also demonstrated that the introduction of small amounts of nano‐SiO₂ into the resin increased the impact strength and tensile strength of PCB simultaneously. J. VINYL ADDIT. TECHNOL., 20:230–236, 2014. © 2014 Society of Plastics Engineers     

Thermal energy storage performance of hierarchical porous kaolinite geopolymer based shape-stabilized composite phase change materials

Phase change materials (PCMs) are prospective energy materials that are widely applied in building energy conservation, waste heat recovery, infrared stealth technology and solar dynamic power system. The enhancement of heat transfer and leak-proof performance are critical to PCMs. Although geopolymers have been applied in thermal energy storage, meanwhile, hierarchically porous geopolymers have already shown superb performance in various functional applications, to the authors’ knowledge, no report concerning the application of hierarchical porous ones have been issued. This paper concerns the preparation of a shape-stabilized composite PCMs, consisting of hierarchically porous kaolinite-based geopolymer (PKG) embedding polyethylene glycol 4000 (PEG4000), which shows promising prospects in thermal energy storage. Optimized porous geopolymer matrices feature high porosity (>83%), combined with high specific surface area (4.7 m²/g) and thermal conductivity (TC, 1.324 W·m⁻¹·K⁻¹). Furthermore, the shape-stabilized composite PCMs show excellent thermal energy storage properties: loading rate of 80.93 wt%, latent heat of 168.80 J g⁻¹ and TC of ∼0.36 W·m⁻¹·K⁻¹ at 20–30 °C, which is 1.64 times of the TC of pure PEG4000. Finally, the photothermal conversion performances of the shape-stabilized composite PCMs were also simulated.     

Nonisothermal crystallization kinetics of flame‐sprayed polyamide 1010/nano‐ZrO2 composite coatings

Polyamide1010 (PA1010) and its composite with nanometer‐sized zirconia (PA1010/nano‐ZrO₂) coatings were deposited using a flame spray process. The kinetics of nonisothermal crystallization of PA1010/nano‐ZrO₂ composite coatings was investigated by differential scanning calorimetry (DSC) at various cooling rates. Several different analysis methods were used to describe the process of nonisothermal crystallization. The results showed that the modified Avrami equation and Mo's treatment could describe the nonisothermal crystallization of the composite coatings very well. The nano‐ZrO₂ particles have a remarkable heterogeneous nucleation effect in the PA1010 matrix. The values of halftime and Z_c showed that the crystallization rate increased with increasing cooling rates for both PA1010 and PA1010/nano‐ZrO₂ composite coating, but the crystallization rate of PA1010/nano‐ZrO₂ composite coating was faster than that of PA1010 at given cooling rate. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Thermal and morphological behavior of irradiated composite materials based on injection‐moulded recycled polyethylene terephthalate

The effect of gamma irradiation and short glass fiber (SGF) on the thermal and morphological behavior of the recycled poly (ethylene terephthalate) (rPET) in the presence of reactive additive (epoxy resin, 2 wt %) has been investigated. Characterization of the resulted composites to evaluate the effect of incorporation the SGF and irradiation by means of differential scanning calorimetry, X‐ray diffraction, thermal gravimetric analysis, and scanning electron microscopy (SEM). The results show that the SGF and epoxy resin behave as nucleating agents for the crystallization of rPET. A noticeable increase in the rPET thermal stability in the presence of both SGF and epoxy resin has been observed. Furthermore, the rPET melting temperature (T_m) slightly decrease in the presence of the SGF and remains nearly constant with the incorporation of the epoxy resin. On the other hand, the rPET crystallinity percent (X%) decreases in the presence of SGF and gamma irradiation. The SEM showed that a layer of epoxy resin was coated onto the SGF in the rPET matrix. This coating layer raises the interfacial shear strength between the fiber and polymer matrix and also increases with gamma irradiation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Decomposition kinetics of a phenolic–carbon composite. II. Rate relationships

The isothermal decomposition of a phenolic resin in a phenolic–carbon cloth composite was measured in air at 0.1 to 0.2 torr over the temperature range 104–718°C. Two decomposition rate relationships are presented that can be used to predict decomposition. One assumes two second-order consecutive rate-controlling reactions, and the other assumes a diffusion-limited second-order reaction. Two rate constants govern each relationship, one being operative during the initial decomposition stages, and the other during the final stages. Evidence is presented to support the applicability of both relationships to predict decomposition over the entire temperature range studied. Arrhenius plots of the rate constants consist of several segments linearly connected. Activation energies and frequency factors computed from these segments cover a broad range of values. The activation energies are used to correlate the temperature ranges with the predominant products formed in these ranges.     

Viscoelasticity of porous composite materials: Experimentals and theory

The viscoelasticity of latex/PS beads composites, having the same volume content of latex and PS beads, but various porosity ratios and specific surfaces of particles has been investigated in the glass temperature range of the latex matrix. In order to give evidence for the main factors governing the viscoelastic properties, data were compared to numerical simulations based on the Christensen and Lo model and Skorokhod's approach. Such modelings were performed by considering either the latex matrix of the PS beads as the continuous phase. It was concluded that the glassy modulus is mainly governed by the volume fraction of porosity, while the rubbery modulus is controlled by both the interactions between phases and the void volume content. The location of the mechanical relaxation seems to be governed by the mechanical coupling between phases, which implies some local phase inversion. The magnitude of the mechanical relaxation depends not only on the chemical coupling induced by the interactions between phases, but also on the mechanical coupling.     

Activation energy and curing behavior of resol‐ and novolac‐type phenolic resins by differential scanning calorimetry and thermogravimetric analysis

The thermal behavior, thermal degradation kinetics, and pyrolysis of resol and novolac phenolic resins with different curing conditions, as a function of the formaldehyde/phenol (F/P) molar ratio (1.3, 1.9, and 2.5 for the resol resins and 0.5, 0.7, and 0.9 for the novolac resins) were investigated. The activation energy of the thermal reaction was studied with differential scanning calorimetry at five different heating rates (2, 5, 10, 20, and 40°C/min) between 50 and 300°C. The activation energy of the thermal decomposition was investigated with thermogravimetric analysis at five different heating rates (2, 5, 10, 20, and 40°C/min) from 30 to 800°C. The low molar ratio resins exhibited a higher activation energy than the high molar ratio resins in the curing process. This meant that less heat was needed to cure the high molar ratio resins. Therefore, the higher the molar ratio was, the lower the activation energy was of the reaction. As the thermal decomposition of the resol resins proceeded, the activation energy sharply decreased at first and then remained almost constant. The activation energy of the thermal decomposition for novolac resins with F/P = 0.5 or F/P = 0.7 was almost identical in all regions, whereas that for novolac resins with F/P = 0.9 gradually decreased as the reaction proceeded. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2589–2596, 2003