LDPE composite films incorporating ceramic powder emitting far‐infrared radiation for advanced food‐packaging applications

A ceramic powder that emits far‐infrared radiation (FIR) was incorporated into low‐density polyethylene (LDPE) via melt‐compounding and subsequent melt‐extrusion processes. To investigate the feasibility of as‐prepared LDPE/FIR composite films for use in packaging applications, the composite films were characterized using Fourier transform infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, FIR emissivity and emissive power, antimicrobial activity assays, and storage tests. The physical properties and antimicrobial activities of the composite films were found to strongly correlate with the changes in the chemical and morphological structures that originate from different contents of FIR ceramic powder. A higher content of FIR ceramic powder in the LDPE/FIR composite film provided increased FIR emissivity and emission power of the composite and resulted in good antimicrobial activity. Storage tests also showed that incorporation of FIR ceramic powder into LDPE film was an effective method for maintaining the freshness of lettuce. Furthermore, the incorporation of FIR ceramic powder into LDPE films induced higher thermal stability and crystallinity and enhanced their barrier properties, which suggest these LDPE/FIR composite films are potential candidates for advanced packaging materials for the food and medical industries. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43102.     

A general and efficient route to covalently surface modification of MWCNTs by dopamine and their synergistic reinforcing effects in chitosan films

Multiwalled carbon nanotubes (MWCNTs) were considered as ideal filler in a polymer matrix due to their outstanding mechanical, electrical and thermal properties. This article describes a simple route to preparation of nanocomposite (NC) of chitosan and modified MWCNT by solution casting method. The process involves modification of MWCNT with dopamine and effects of modified MWCNT on dispersion, mechanical, thermal and morphological properties. Atomic force microscopy, Fourier transform infrared spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy, transmission electron microscopy, have been used to characterize the NCs. Scanning electron micrographs showed that in all of the NC films, except chitosan/MWCNT-Dop NC 7 wt%, MWCNT were dispersed homogeneously throughout the chitosan matrix. The XRD studies showed that the crystallinity of composite films decreases through hydrogen bonding between chitosan and MWCNT-Dop. The determination of mechanical and thermal properties demonstrated that the NC films exhibited significant enhancement in strength, modulus, and thermal stability compared with the pure chitosan.     

Synthesis of high performance organic–inorganic composite via click coupling of block polymer and polyhedral oligomeric silsesquioxane

Novel hybrid systems based on poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS) and a polyhedral oligomeric silsesquioxane (POSS) have been synthesized via click chemistry. Different compositions of SEBS-functionalized POSS were obtained from the reaction of azide-functionalized styrene units of SEBS with alkyne-functionalized POSS molecules. Characterization of SEBS-functionalized POSS by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and nuclear magnetic resonance spectroscopy revealed that the POSS molecules were successfully attached to the phenyl group of the SEBS polymer chain following the click reaction. Homogeneous dispersion of POSS molecules in the polymer matrix was demonstrated by scanning electron microscopy. The POSS molecule showed excellent compatibility with polymer matrix, and as a consequence the remarkable enhancement of mechanical properties (breaking stress = 44%, modulus = 285%) and thermal stability for the resulting composite films was achieved. The reinforcing effect is ascribed to both the compatible homogeneous dispersion of POSS in the matrix and the covalent bond between SEBS and POSS molecules arising from the click coupling.     

Novel low-κ polyimide/mesoporous silica composite films: Preparation,microstructure, and properties

A series of novel low-dielectric constant (low-κ) polyimide (PI) composite films containing the SBA-15 or the SBA-16-type mesoporous silica were successfully prepared via in situ polymerization and following thermal imidization. Their morphologies, dielectric constants, and thermal and dynamic mechanical properties were investigated. It is found that the dielectric constants of the composite films can be reduced from 3.34 of the pure PI to 2.73 and 2.61 by incorporating 3 wt% SBA-15 and 7 wt% SBA-16, respectively. The reduction of the dielectric constant is attributed to the incorporation of the air voids (κ = 1) stored within the mesoporous silica materials, the air volume existing in the gaps on the interfaces between the mesoporous silica and the PI matrix, and the free volume created by introducing large-sized domains. The PI/mesoporous silica composite films prepared in this study also present stable dielectric constants across the wide frequency range and a good phase interconnection. The improvement of the thermal stability and dynamic mechanical properties of the PI film is achieved by incorporation of the mesoporous silica materials. The enhanced interfacial interaction between the surface-treated mesoporous silica and the PI matrix has led to the minimization of the deterioration of the mechanical properties. The incorporation of the mesoporous silica materials is a promising approach to prepare the low-κ PI films.     

Effect of hydrophilic and hydrophobic cyclodextrins on the release of encapsulated allyl isothiocyanate (AITC) and their potential application for plastic film extrusion

Allyl isothiocyanate (AITC), a natural pungent flavor from wasabi and horseradish, is well-known antimicrobial agents against foodborne pathogens. However, its highly volatile nature and low thermal stability restrict its application in the food packaging industry. Also, its strong organoleptic characteristics hinder its application at a higher dosage. We encapsulated AITC in β-cyclodextrin (β-CD) and triacetyl-β-CD (TA-β-CD) and evaluated the performance as slow releasing active compounds through low-density polyethylene (LDPE)–cyclodextrins (CDs) matrix. Also, the thermal, optical, mechanical, and barrier properties of two ternary blends, LDPE/β-CD/AITC(L-CDs) and LDPE/TA-β-CD/AITC(L-TACDs), were investigated to compare their compatibility under the plastic extrusion process. During the 15 days of the storage period, L-TACDs maintained more consistent AITC release and a higher concentration than L-CDs. Also, the blending of LDPE and TA-β-CD was more compatible with that of LDPE and β-CD. No significant optical, mechanical, and barrier property changes were observed in LDPE with less than 3% of TA-β-CD while L-CDs showed substantial agglomeration on the ternary blend films and the lower mechanical and barrier properties than pure LDPE. The results indicate that the LDPE films containing TA-β-CD/AITC can be applied as an effective antimicrobial packaging material for food and nonfood applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48137.     

Preparation,thermal properties and thermal reliability of eutectic mixtures of fatty acids/expanded vermiculite as novel form-stable composites for energy storage

This paper deals with the preparation, characterization, thermal properties and thermal reliability of novel form-stable composite phase change materials (PCMs) composed of eutectic mixtures of fatty acids and expanded vermiculite for thermal energy storage. The form-stable composite PCMs were prepared by incorporation of eutectic mixtures of fatty acids (capric–lauric, capric–palmitic and capric–stearic acids) within the expanded vermiculite by vacuum impregnation method. The composite PCMs were characterized by SEM and FTIR techniques. Thermal properties of the composite PCMs were determined by differential scanning calorimeter (DSC) method. DSC results showed that the melting temperatures and latent heats of the prepared composite PCMs are in the range of 19.09–25.64 °C and 61.03–72.05 J/g, respectively. The thermal cycling test including 5000 heating and cooling process was conducted to determine the thermal reliability of the composite PCMs. The test results showed that the composite PCMs have good thermal reliability and chemical stability. Furthermore, thermal conductivities of the composite PCMs were increased by adding 10 wt% expanded graphite. Based on all results, the prepared form-stable composites can be considered as promising PCMs for low temperature thermal energy storage applications due to their satisfactory thermal properties, good thermal reliability, chemical stability and thermal conductivities.     

The preparation and characterization of urushiol powders (YPUOH) based on urushiol

Urushiol and lacquer sap from lacquer tree exhibit good antimicrobial and antioxidant properties. However, they are limited to commercial application due to their high volatility, low drying rate and allergic reaction. To overcome these limitations, solid-type urushiols (YPUOH), which is one of the essential factors for convenient handling in various industrial fields such as functional additives for paints, coating and composite films, were successfully prepared with urushiol and TPM. The reaction mechanism between urushiol and silane coupling agent has been evaluated based on Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). As-prepared YPUOH powders exhibited excellent antibacterial activity against E. coli and S. aureus, good antioxidant activity, and high thermal stability.     

Nanocomposite polymer films containing carvacrol for antimicrobial active packaging

Nanocomposite films based on low‐density polyethylene (LDPE) containing carvacrol were prepared and characterized with the aim to get antimicrobial active packaging. Organo‐modified montmorillonite (MMT) was used as filler. The weak interaction between LDPE and clay led to the formation of intercalated systems. On the other hand, strong interaction between carvacrol and organosilicate allowed a good dispersion of the oil into the clay galleries, promoting the swelling of MMT stacks and a higher polymer/clay interface. As a result, carvacrol was protected against thermal degradation and its release from the films was efficiently delayed. Moreover, outstanding thermal oxidative stability as well as improved oxygen barrier properties were detected in the nanocomposite containing carvacrol. The presence of clay and carvacrol also increased LDPE crystallinity, due to an enhanced nucleation activity, while the mechanical properties of the films were slightly affected. The antimicrobial properties of carvacrol containing films were tested, showing a significant activity against several bacterial strains, which is preserved in presence of the clay. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Dielectric properties of a novel high absorbing onion-like-carbon based polymer composite

A novel lightweight onion-like carbon (OLC) based Poly(methyl metacrylate) (PMMA) composite with high electromagnetic (EM) absorption capability determined earlier in microwave range is studied in low frequencies from 20 Hz to 1 MHz by dielectric spectroscopy. The investigation of dielectric properties of PMMA films with incorporated OLC in small concentration (0.5–2 wt.%) have been carried out by varying the temperature between 240 and 520 K. The temperature behavior of the complex permittivity at a given frequency is found to be strongly dependent on the OLC concentration. The experimental data are in quantitative agreement with the results of modified effective medium calculations of OLC-based polymer film's permittivity. Both the experimental observations and theoretical simulation demonstrate that small additions of onion-like carbon particles to a polymer matrix can noticeably modify the composite response to low-frequency EM radiation as well as improve its thermal stability (increased glass transition and melting temperatures, correspondingly).     

Studying the effect of organo-modified nanoclay loading on the thermal stability,flame retardant,anti-corrosive and mechanical properties of polyurethane nanocomposite for surface coating

Clay polyurethane nanocomposite (CPN) coating films were fabricated by uniformly dispersing nanoclay, organically modified with 25–30 wt.% octadecylamine in varying concentrations up to 5 wt.%, in a commercial two component, glossy, acrylic aliphatic polyurethane using ultrasonication. Organo-modified nanoclay was characterized by X-ray diffraction (XRD). The dispersion of the nanoclay into the matrix was investigated by scanning electron microscopy (SEM). CPN coating films were characterized by thermogravimetric analysis (TGA), and flame retardant, corrosion resistance and mechanical properties were also investigated. The XRD measurement indicated that, the organo-modified nanoclay particles were mainly constituted of montmorillonite with traces of quartz and calcite also found to be present. The SEM analysis showed that the nanoclay layers were dispersed and intercalated into the polyurethane coating. Thermogravimetric analysis showed that incorporating 5 wt.% organo-nanoclay into polyurethane considerably enhanced the thermal stability and increased the char residue to 14.11 wt.% relative to 4.58 for the sample without organo-nanoclay (blank polyurethane). The limiting oxygen index (LOI) test revealed that incorporation of organo-nanoclay led to a further increase in LOI values, which indicate an improvement in flame retardancy properties. The corrosion resistance also improved and this improvement increases with increase nanoclay wt.%. The mechanical resistance measurements demonstrated that the gloss of the CPN coating films slightly decreased, although hardness, adhesion and impact resistance of the CPN coating films improved with the incorporation of the organo-nanoclay.     

Fabrication and properties of mullite fiber matrix porous ceramics by a TBA-based gel-casting process

A bird nest-like structure was designed by using the mullite fiber as the matrix and SiO₂ as the high temperature binder. This special material was successfully prepared by a TBA-based gel-casting process. The randomly arranged fiber laps bonded by SiO₂ binder was the most important structure characteristic of this porous material. The effect of sintering temperature on the properties, i.e. porosity, bulk density, linear shrinkage, compressive strength, thermal conductivity and the microstructure was studied. The composite exhibited significant pseudoductility. The fracture mechanism of this composite under compression was discussed. The results indicated that the sintering temperature ranging from 1500 to 1600 °C was suitable for yielding mullite fiber matrix porous ceramics which had a low thermal conductivity (0.19–0.22 W/m K), a relatively high compressive strength (3–13 MPa) and a high resilience (66–70%) for applications in the thermal insulators and high-temperature elastic seal field.     

Synthesis,morphology and physical properties of multi-walled carbon nanotube/biphenyl liquid crystalline epoxy composites

We have developed multi-walled carbon nanotube/liquid crystalline epoxy composites and studied the effects of incorporation carbon nanotubes (CNTs) on the morphology, thermal and mechanical properties of the composites. The CNTs are functionalized by liquid crystalline (LC) 4,4′-bis(2,3-epoxypropoxy) biphenyl (BP) epoxy resin for the ease of dispersion and the formation of long range ordered structure. The epoxy functionalized CNT (ef-CNT) were dispersed in the LC BP epoxy resin that can be thermal cured with an equivalent of 4,4′-diamino-diphenylsulfone to form composite. The curing process was monitored by polarized optical microscopy. The results indicate the LC resin was aligned along the CNTs to form fiber with dendritic structure initially then further on to obtain micro-sized spherical crystalline along with fibrous crystalline. With homogeneous dispersion and strong interaction between nanotubes and matrix, the composite containing 2.00 wt.% ef-CNT exhibits excellent thermal and mechanical properties. When the amount of ef-CNT exceeds 2.00 wt.%, vitrification stage of curing is fast reached, which lowers the degree of conversion. As compared with the neat resin, the composite containing 2.00 wt.% ef-CNT increases the glass transition temperature by 70.0 °C, the decomposition temperature by 13.8 °C, the storage modulus by 40.9%, and the microhardness by 63.3%.     

A study of the oxidation behavior of CrN and CrZrN ceramic thin films prepared in a magnetron sputtering system

CrN and CrZrN ceramic thin films were produced by a planar type reactive sputtering system on glass and stainless steel substrates. We investigated oxidation resistance of CrN and CrZrN ceramic thin films with different Zr contents. The structure of the films at different thermal-annealing temperatures was investigated by X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). The mechanical properties of the films at different thermal-annealing temperatures were measured by nano-indentation. The results of this study showed that the addition of few amount of Zr (0.4 at%), can improve thermal stability of CrZrN ceramic thin film and increase the oxidation temperature of the film from 600 °C to 800 °C. The relatively good oxidation resistance (800 °C) and high hardness of the film with the lowest Zr content, indicates that this film is a good candidate for high temperature applications.     

A facile one step electrostatically driven electrocodeposition of polyviologen–reduced graphene oxide nanocomposite films for enhanced electrochromic performance

Polyviologen (PV)–reduced graphene oxide (rGO) nanocomposite films were fabricated by simple, one-step reductive electropolymerization of cyanopyridinium based precursor monomer (CNP) in an aqueous dispersion of graphene oxide (GO). Since the polymer formation and reduction of graphene oxide occurs within the same potential window, electrocodeposition method was preferred for obtaining nanostructured PV–rGO films. Cyclic voltammetry experiments of PV–rGO displayed two well resolved, reversible one-electron redox processes typical of viologen. Being a redox polymer, incorporation of rGO further enhances the electroactivity of the PV in the composite films. Vibrational spectral analysis with surface characterization revealed structural changes after composite formation along with subsequent reduction of GO within the polymer matrix. The PV–rGO nanostructured film exhibits a high-contrast electrochromism with low driving voltage induced striking color changes from transparent (0 V) to purple (−0.6 V), high coloration efficiency, fast response times and better cycling stability compared to a pristine PV film. This improved performance can be attributed to the high stability of the electrochrome in the composite assembly induced by electrostatically driven non-covalent interactions between redox PV²⁺ and negatively charged rGO, improved electrical conductivity and enlarged surface area accessed through reinforced nanostructured graphene sheets for tethering PV molecules.     

Effect of processing technique on the transport and mechanical properties of vapour grown carbon nanofibre/rubbery epoxy composites for electronic packaging applications

Vapour grown carbon nanofibre (VGCNF)/rubbery epoxy (RE) composites were produced, by either mechanical mixing, three-roll milling (RM) or combined ultrasonication/mechanical mixing. Incorporation of VGCNFs resulted in significant enhancements in the thermal and electrical conductivities of the material. Appropriate selection of processing technique and parameters can help to maximise the potential of VGCNF additions by improving their dispersion in the matrix. The composites produced by RM have superior transport properties compared with those produced by other techniques. The thermal conductivity of such composites at 40 wt.% VGCNFs reached 1.845 W/m K, a 10-fold increase compared to RE alone. The thermal conductivity data of VGCNF/RE composites best fits to the Hatta–Taya model. The lowest electrical percolation threshold is at 2 wt.%, obtained for composites produced by RM. The thermal conductivity of VGCNF/glassy epoxy (GE) composites at 12 wt.% is 10% lower than the corresponding RE composite but its electrical conductivity is 2 orders of magnitude higher than the corresponding RE composite. VGCNFs at 40 wt.% increase the compressive strength of rubbery epoxy by ～5× but the compressive modulus of 40 wt.% VGCNF/RE composite is 12 times lower than that of 12 wt.% VGCNF/GE composite, demonstrating highly compliant nature of RE composites.     

Preparation of erythritol–graphite foam phase change composite with enhanced thermal conductivity for thermal energy storage applications

Three-dimensional interconnected graphite composite foam as a heat conductive matrix was fabricated by using low cost polymeric precursors and polyurethane (PU) foam as carbon source and sacrificial macroporous template, respectively. Erythritol–graphite foam as a stable composite phase change material (PCM) was obtained by incipient wetness impregnation method. The thermophysical properties such as thermal diffusivity, specific heat, thermal conductivity and latent heat of the erythritol–graphite composite foam were measured. From the results, it was found that the thermal conductivity of the erythritol–graphite composite foam (3.77 W/mK) was enhanced 5 times as compared with that of pristine erythritol (0.72 W/mK). This enhancement can significantly reduce the charging and discharging times of the PCM storage system. There is no chemical reaction between erythritol and graphite as confirmed by X-ray diffractometer (XRD). The PCM/foam composite has a melting point of 118 °C and latent heat of 251 J/g which corresponds to the mass percentage (75 wt.%) of the erythritol within the composite foam. The obtained results confirmed the feasibility of using erythritol–graphite foam as a new phase change composite for thermal energy storage (TES) applications, thus it can contribute to the efficient utilization and recovery of solar heat or industrial waste heat.     

Improved charging/discharging behavior of electropolymerized nanostructured composite films of polyaniline and electrochemically reduced graphene oxide

In this work, a simple electrochemical reduction procedure has been applied to nanostructured composite films of polyaniline (PANI) and graphene oxide (GO) having a globular surface morphology with the grain size of 50 nm. The reduction converts GO to reduced GO (rGO) which improves the electroactivity of the PANI composite films with 30%. Cyclic voltammetry confirmed the reduction of GO to rGO whereas electrochemical impedance spectroscopy showed that the rGO network increases the redox capacitance of the composite films with 15% to 77 mF cm⁻². In a three-electrode cell, the anodic charge of the PANI film containing GO increased with 18.7% during the potential cycling stability test for 10,000 cycles between −0.2 and 0.5 V, indicating that the film had a good stability against degradation. This composite film type still maintained a high capacitance of 15 mF cm⁻² in a symmetric two-electrode cell after 10,000 potential cycles between 0 and 0.4 V. The electrochemically prepared PANI composite films reported here are aimed to be used in capacitor applications where it is crucial to deposit thin PANI layers on well-defined small surfaces where other polymerization or deposition techniques cannot be used and in solid-state chemical sensors as ion-to-electron transducer interfaces.     

Jatropha curcas oil based alkyd/epoxy/graphene oxide (GO) bionanocomposites: Effect of GO on curing,mechanical and thermal properties

Jatropha curcas oil based alkyd/epoxy/GO bionanocomposites were prepared by direct solution blending of alkyd/epoxy blend matrix with GO nano filler. Structures and properties of the bionanocomposites were characterized with Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, differential scanning calorimetry, thermogravimetric analysis, and tensile testing. X-ray diffraction and transmission electron microscopy study demonstrates the formation of highly exfoliated GO layers and its homogeneous dispersion throughout the polymer matrix with 1 and 3 wt% GO. However, the intercalated structure is predominant with 5 wt% GO. The homogeneous dispersion and the strong interaction of the GO layers and the polymer matrix induced the significant improvement in thermal and mechanical properties of the bionanocomposites. The tensile strength and elastic modulus of the bionanocomposite increased by 133% and 68% respectively with 3 wt% GO loading. The thermal stability of the bionanocomposite improved by 39 °C and T_g is shifted toward higher temperature by 20 °C as compared to the pristine polymer. Incorporation of GO significantly decreases the curing time of the alkyd/epoxy resin blend.     

Preparation and properties of poly(propylene carbonate) and nanosized ZnO composite films for packaging applications

A series of polypropylene carbonate (PPC)/ZnO nanocomposite films with different ZnO contents were prepared via a solution blending method. The morphological structures, thermal properties, oxygen permeability, water sorption, and antibacterial properties of the films were investigated as a function of ZnO concentration. While all of the composite films with less than 5 wt % ZnO exhibited good dispersion of ZnO in the PPC matrix, FTIR and SEM results revealed that solution blending did not lead to a strong interaction between PPC and unmodified ZnO. As such, poor dispersion was induced in the composite films with a high ZnO content. By incorporating inorganic ZnO filler nanoparticles, the diffusion coefficient, water uptake in equilibrium, and oxygen permeability decreased as the content of ZnO increased. The PPC/ZnO nanocomposite films also displayed a good inhibitory effect on the growth of bacteria in the antimicrobial analysis. The enhancement in the physical properties achieved by incorporating ZnO is advantageous in packaging applications, where antimicrobial and environmental‐friendly properties, as well as good water and oxygen barrier characteristics are required. Furthermore, UV light below ～ 350 nm can be efficiently absorbed by incorporating ZnO nanoparticles into a PPC matrix. ZnO nanoparticles can also improve the weatherability of a PPC film. In future research, the compatibility and dispersion of the PPC matrix polymer and the inorganic ZnO filler nanoparticles should be increased. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

High-temperature alloy/honeycomb ceramic composite materials for solar thermal storage applications: Preparation and stability evaluation

SiC_w/Al₂O₃ honeycomb ceramics were engaged as sensible shell materials for encapsulating Al-Si alloys (latent heat materials) in the honeycomb holes to obtain alloy/ceramic composite materials with a high thermal storage capacity for high-temperature solar thermal storage applications. The stability evaluation between the sensible honeycomb ceramics and the latent alloys had been conducted and the failure mechanism for the latent alloys was investigated. Results indicated that the addition of the latent alloys could improve the thermal storage capacity of the sensible honeycomb ceramics significantly by >114% and the thermal storage densities of honeycombs containing Al-12Si and Al-20Si alloys were 1141.3 kJ/kg and 1106 kJ/kg (400–900 °C), respectively. The composite materials exhibited excellent physical and chemical stability. No cracks formed in the honeycomb ceramics and no leakage of alloys was discovered after the composite materials were exposed to 100 thermal cycles in a high-temperature testing environment. The oxidation of Al at >600 °C would lower the latent heat of alloys and the thermal storage densities decreased to 1039.9 kJ/kg and 1013.2 kJ/kg after enduring 100 thermal cycles. This study not only provides a sensible-latent system of thermal storage materials with excellent stability but also gives an insight into the protection of metal containers against the corrosion from Al-based alloys.