Effect of corona pre-treatment on the performance of gas barrier layers applied by atomic layer deposition onto polymer-coated paperboard

The effect of corona pre-treatment on the performance of Al₂O₃ and SiO₂ gas barrier layers applied by atomic layer deposition onto polymer-coated paperboards was studied. Both polyethylene and polylactide coated paperboards were corona treated prior to ALD. Corona treatment increased surface energies of the paperboard substrates, and this effect was still observed after several days. Al₂O₃ and SiO₂ films were grown on top of the polymer coatings at temperature of 100 °C using the atomic layer deposition (ALD) technique. For SiO₂ depositions a new precursor, bis(diethylamido) silane, was used. The positive effect of the corona pre-treatment on the barrier properties of the polymer-coated paperboards with the ALD-grown layers was more significant with polyethylene coated paperboard and with thin deposited layers (shorter ALD process). SiO₂ performed similarly to Al₂O₃ with the PE coated board when it comes to the oxygen barrier, while the performance of SiO₂ with the biopolymer-coated board was more moderate. The effect of corona pre-treatment was negligible or even negative with the biopolymer-coated board. The ALD film growth and the effect of corona treatment on different substrates require further investigation.     

Effect of Fiber Surface Modification on the Interfacial and Mechanical Properties of Kenaf Fiber-Reinforced Thermoplastic and Thermosetting Polymer Composites

The surfaces of kenaf fibers were treated with three different silane coupling agents. 3-glycidoxypropyltrimethoxy silane (GPS), 3-aminopropyltriethoxy silane (APS), and 3-methacryloxypropyltrimethoxy silane (MPS). Among them, the most effective one for the property improvement was GPS when it was applied to the kenaf fiber surfaces at 0.5 wt%. Thermoplastic polypropylene (PP) and thermosetting unsaturated polyester (UPE) matrix composites with chopped kenaf fibers untreated and treated at different GPS concentrations from 0.1 wt% to 5 wt% were fabricated using compression molding technique. The present study demonstrates that the interfacial, flexural, tensile, and dynamic mechanical properties of both kenaf/PP and kenaf/UPE composites importantly depend on the GPS treatments done at different concentrations. The greatest property improvement of both thermoplastic and thermosetting polymer composites was obtained with the silane treatment at 0.5 wt% and the mechanical properties were comparable with E-glass composites prepared the same polymer matrix under the corresponding fiber length and fiber loading. The results also agreed with each other with regard to their interfacial shear strength, flexural properties, tensile properties, storage modulus, with support of fracture surfaces of the composites.     

AFM Observation of a Mica Surface Treated with Silane Coupling Agent Having a Mercapto Group

The topography of mica surface after treatment with silane coupling agent having a mercapto group was studied using an atomic force microscope. The cleaved mica plate was used as a model inorganic surface. The effect of treatment condition on the topography of the mica surface was investigated. Agglomerates consisting of self-condensed silane molecules were observed on the surface. However, their amount and size were smaller than those for silanes having other organo-functional groups such as amino, methacryloxy and vinyl groups. Aqueous and water/2-propanol mixture solutions gave a smoother surface as compared with a 2-propanol solution. There was no significant influence discernable from di- and trialkoxy structures. The aqueous solution of silane coupling agent having a mercapto group showed an acidic pH. This was the reason why the smoother silane-treated layer was formed by the silane with the mercapto group than by those with other organic functional groups, because the silanol group generated by hydrolysis is stable in an acidic pH.     

Novel Jute/Polycardanol Biocomposites: Effect of Fiber Surface Treatment on Their Properties

In the present study, novel biocomposites with chopped jute fibers and thermosetting polycardanol were prepared using compression molding technique for the first time. Prior to biocomposite fabrication, jute fiber bundles were surface-treated at various concentrations using 3-glycidoxypropyltrimethoxy silane (GPS) and 3-aminopropyltriethoxy silane (APS), respectively. The interfacial shear strength, flexural properties and thermal properties of jute/polycardanol biocomposites reinforced with untreated and silane-treated jute fibers were investigated by means of single fiber microbonding test, three-point flexural test, dynamic mechanical analysis, thermogravimetric analysis and thermomechanical analysis. Both GPS and APS treatments played a role in improving the interfacial adhesion, reflecting that the organofunctional groups located at the end of silane coupling agents may contribute to linking between jute fibers and a polycardanol resin. As a result, it gave rise to increased interfacial shear strength of the biocomposites. Such interfacial improvement also led to increasing the flexural strength and modulus, storage modulus, thermal stability and thermomechanical stability.     

X-ray photoelectron spectroscopy,X-ray excited Auger electron spectroscopy and time-of-flight secondary ion mass spectroscopy characterization of carbon fibres activated by d.c. corona discharge at ambient pressure and temperature

High modulus polyacrylonitrile-derived fibres were characterized by X-ray photoelectron spectroscopy, X-ray excited Auger electron spectroscopy and time-of-flight secondary ion mass spectroscopy after d.c. corona discharge treatments under a nitrogen atmosphere at ambient pressure and temperature. The results allow identification of the main functional groups produced by the treatment on the fibre surface and verification of a substantial equivalence of negative- and positive-corona discharge treatments.     

Annealing effect in glass woven fabric composites,Part I. Mode I and mode II interlaminar fracture behavior

Mode I and mode II interlaminar fracture behavior of plain glass woven fabric composites with different silane concentration was investigated on the basis of a discussion of the effects of annealing on the fracture behavior. The fracture mode changed by annealing from stable to unstable manner in lower silane concentration and from unstable to stable manner in higher silane concentration specimens in mode I fracture. In the mode II fracture, the initiation values of fracture toughness increased by annealing without respect to silane concentration.     

UV grafting of extended chain polyethylene fibres

A bench-scale continuous fibre treatment line has been built to modify polyethylene fibre surfaces using UV radiation-induced grafting. It is shown that grafting does indeed take place and that the grafts adhere well to the resin. Single-fibre pullout behaviour, interlaminar shear strength, and flexural behaviour were observed to improve considerably. The loss of tensile properties due to treatment was investigated and found to be small in the range of useful treatments. The interlaminar shear strength of the UV-treated fibre is as high as 38 MPa (5.5 ksi) as compared with the untreated fibre value of 10 MPa (1.5 ksi). The most important process parameters are identified and trends established.     

Effect of surface treatment of nanoclay on the mechanical properties of epoxy/glass fiber/clay nanocomposites

A new method of silane treatment of nanoclays is reported where in the clay is nanodispersed in hydrolyzed silanes. The surface functionalization of Cloisite^® 15A nanoclay has been carried out using two different silane coupling agents: 3-aminopropyltriethoxy silane and 3-glycidyloxypropyltrimethoxy silane using varied amounts of silane coupling agents, e.g. 10, 50, 200, and 400 wt% of clay. The surface modification of Cloisite^® 15A has been confirmed by Fourier transform infrared spectroscopy. The modified clays were then dispersed in epoxy resin, and glass fiber-reinforced epoxy clay laminates were manufactured using vacuum bagging technique. The fiber-reinforced epoxy clay nanocomposites containing silane modified clays have been characterized using small angle X-ray scattering, transmission electron spectroscopy and differential scanning calorimetry. The results indicate that the silane treatment of nanoclay aided the exfoliation of nanoclay and also led to an increase in mechanical properties. The optimized amount of silane coupling agents was 200 wt%. The nanocomposites containing clay modified in 200 wt% of silanes exhibited an exfoliated morphology, improved tensile strength, flexural modulus, and flexural strength. The improved interfacial bonding between silane modified nanoclays and epoxy matrix was also evident from significant increase in elongation at break.     

Effect of surface treatment on mode I interlaminar fracture behaviour of plain glass woven fabric composites: Part I. Report of the 2nd round-robin test results

A round-robin test programme has been carried out to characterise the mode I interlaminar fracture behaviour of E-glass woven fabric reinforced vinyl ester matrix composites. Special emphasis has been placed on the effect of silane coupling agent on the stability of interlaminar crack propagation and fracture toughness. Sixteen laboratories participated in this programme. Each laboratory was supplied with composite laminates of thicknesses of its own choice and conducted the tests according to its own procedures. The results showed that variations in interlaminar fracture toughness between laboratories were very large in spite of slight differences in the test procedures used, such as specimen dimensions, test speed and data reduction schemes. Nevertheless, the general trends were clearly identified with respect to different silane coupling agents. Other observations and the implications are discussed.     

Effects of surface treatment and weave structure on interlaminar fracture behaviour of plain glass woven fabric composites: Part II. Report of the 2nd round robin test results

This paper reports the second part of the results from the round robin test program proposed by the Society of Interfacial Materials Science (SIMS) to characterise the interlaminar fracture behaviour of E-glass woven fabric reinforced vinylester composites. Special emphasis was placed on the study of loading direction (i.e. weft and warp directions) effect on interlaminar shear strength and fracture toughness. Ten laboratories worldwide participated in this test (Table 1). Each laboratory was supplied with composite laminates and conducted the tests according to its own procedure. The results showed that although there were large variations in absolute magnitude between laboratories, a general trend was established with higher interlaminar fracture resistance in the weft direction than in the warp direction for a given silane agent. The larger number of strands running in the warp direction with rougher, more undulating areas perpendicular to the direction of crack propagation was mainly responsible for this result. The results also confirmed the previous finding that the mode I interlaminar fracture toughness increased with increasing silane agent concentration.     

Improving the interfacial strength of PMMA resin composites by chemically grafting graphene oxide on UHMWPE fiber

Controlling interfacial microstructure and interactions between (ultra high molecular weight polyethylene) UHMWPE fiber and matrix is of crucial importance for the fabrication of advanced polymer composites. In this paper, (UHMWPE fiber-g-graphene oxide [GO]) was prepared. GO nanoparticles distributed onto the ?ber surface uniformly, which could increase surface polarity and roughness. Increases of interlaminar shear strength (ILSS) and interfacial shear strength (IFSS) of UHMWPE fiber-g-GO composites were achieved. These enhancements can be attributed to the existent of GO interface with providing chemical bonding and strong mechanical interlocking between the ?ber and matrix. Moreover, impact resistance of UHMWPE fiber-g-GO composites was enhanced.     

Interfacial characterisation and mechanical properties of heat treated non-woven kenaf fibre and its reinforced composites

This paper reports on the comprehensive characterisation of heat treated kenaf fibre (KF) and its composites. The kenaf fibres were modified by heating for 2.5–12.5 h inside a drying oven. Heat treatment produces an increase in the crystallinity index and fibre strength of KF. The highest value of KF strength was recorded by applying heat treatment of 10 h on KF. The heat treatment results in the partial removal of impurities/extractives on the KF surface which is detected by scanning electron microscopy and X-ray photoelectron spectroscopy. Atomic force microscopy results signify the decrease of roughness, the increase in peak area density and the increase of the adhesion force on the surface area of heat treated KF. The effect of the heat treatment in enhancing the interface bonding characteristics between the KF and unsaturated polyester matrix can be reflected by the interlaminar shear strength (ILSS) and dynamic mechanical analysis value of the composites. The flexural properties of the composites showed a similar trend to ILSS. However, the fracture toughness revealed contrasting results. Water absorption induced a drastic loss of the mechanical properties of the composites albeit better retention of properties was observed in the case of heat-treated KF composites.     

Micromechanical Behavior of Carbon Nanotube-Covered SiC Fibers in Polymer Matrix Composites

The incorporation of nanotube-covered fibers in continuous fiber/epoxy composites has been shown to influence the mechanical, electrical, and thermal properties of the composite. Increased interlaminar shear stress, flexural strength and modulus have been reported in such composites over composites containing bare fibers. In this study, the microstructure and interfacial shear strength (ISS) of continuous silicon carbide fiber/epoxy composites with and without nanotubes grown from the SiC fiber surface were investigated with micro-Raman spectroscopy (MRS) and microscopy. The fibers with nanotubes grown from the surface were found to have a reduced ISS compared with the bare fibers. Electron microscopy showed good wetting of epoxy in the nanotube forests, but poor attachment of the nanotube forests to the fibers. These results suggest that the mechanism leading to improvements in bulk composite properties is not due to an improvement in the fiber/matrix ISS.     

Amino functionalization of carbon nanotube surfaces with NH3 plasma treatment

NH₃ plasma treatment of carbon nanotube (CNT) surfaces was performed with the purpose of incorporating amino groups onto the surface. Amino groups incorporated onto the CNT surface were indentified and quantified using chemical derivatization with pentafluorobenzaldehyde and subsequent characterization with X-ray photoelectron spectroscopy (XPS). The amount of incorporated amino groups reached a maximum value with increasing plasma power. The incorporation of amino groups was seriously affected by the degradation of the CNT surface during the plasma treatment, which became very serious at high plasma power, as verified with optical emission spectroscopy (OES) and FT-IR analyses. The type of species present in the plasma discharge also seems to be important for amino group functionalization; partially decomposed ammonia species are considered to be more favorable than fully decomposed atomic species.     

Effect of sizing agent on interfacial properties of aramid knitted structural composites

Tensile tests have been carried out on aramid knitted fabrics/epoxy resin composites in which the aramid knitted fabrics are treated with different sizing agents. Two kinds of surface treatment are performed; one uses an epoxy sizing agent and the other uses a polyethylene sizing agent. Tensile modulus and strength of epoxy-sized composites are higher than those of polyethylene-sized composites. The fracture process is different between epoxy- and polyethylene-sized materials. This difference in fracture process is caused by the different interphase made from either epoxy or polyethylene sizing treatments, resulting in the different tensile performance. Moreover, the tensile properties of the wale specimen are more affected than those of the course specimen by the interphase.     

Plasma treatment of carbon fibers: Non-equilibrium dynamic adsorption and its effect on the mechanical properties of RTM fabricated composites

The effect of oxygen plasma treatment on the non-equilibrium dynamic adsorption of the carbon fabric reinforcements in RTM process was studied. 5-Dimethylamino-1-naphthalene-sulfonylchloride (DNS-Cl) was attached to the curing agent to study the change of curing agent content in the epoxy resin matrix. Steady state fluorescence spectroscopy (FS) analysis was used to study this changes in the epoxy resin at the inlet and outlet of the RTM mould, and XPS was used to study the chemical changes on the carbon fiber surfaces introduced by plasma treatment. The interlaminar shear strength (ILSS) and flexural strength were also measured to study the effects of this non-equilibrium dynamic adsorption progress on the mechanical properties of the end products. FS analysis shows that the curing agent adsorbed onto the fiber surface preferentially for untreated carbon fiber, the curing agent content in the resin matrix maintain unchanged after plasma treatment for 3 min and 5 min, but after oxygen plasma treatment for 7 min, the epoxy resin adsorbed onto the fiber surface preferentially. XPS analysis indicated that the oxygen plasma treatment successfully increased some polar functional groups concentration on the carbon fiber surfaces, this changes on the carbon fiber surfaces can change the adsorption ability of carbon fiber to the resin and curing agent. The mechanical properties of the composites were correlated to this results.     

In Situ Characterisation of Polymer Surfaces and Thin Organic Films in Plasma Processing

In situ sampling techniques are presented for investigation of plasma surface modification of polymers and plasma polymerisation. FTIR spectroscopy (infrared absorption reflection spectroscopy - IRRAS, and attenuated total reflection - ATR) are properly used for characterisation of the changes in the molecular structure of thin polymer films (polystyrene, polyethylene) due to low pressure plasma treatment. The thin films were prepared by dip or spin coating procedures. In the case of plasma polymerisation a novel fibre-ATR technique is applied to investigate the plasma polymerisation process in the plasma bulk. Results are exemplary shown for plasma polymerisation of styrene. Ellipsometric measurements allowed the characterisation of the thin plasma modified top polymer surface layer or thin deposited plasma polymer films by their refractive index and thickness. It was shown that the applied surface plasmon ellipsometry is very sensitive with respect to the usual ellipsometry for investigation of polymer surface modification. The in situ microgravimetry by means of electronic vacuum microbalance permitted to measure the change of the sample mass in the order of 1 μg during the plasma treatment. The first steps in plasma modification (concurrence between the incorporation of plasma particles and the material etching) were studied.     

Hologram Recording in Various Glass Plates by Corona Charging

We propose techniques of hologram replication in glass plates and reconstruction on another film by corona charging. A surface relief hologram on an azobenzene polymer film was recorded in the form of electric polarization in glass plates that include alkali cations by corona charging at high temperature. The hologram recorded in the glass plate is stable for more than 1 month at room temperature. After removal of the azobenzene polymer film from the plate, poly(methyl methacrylate) (PMMA) film was spin-coated onto the plate. The hologram recorded in the plate was reconstructed with the same surface relief structure on the PMMA film by corona charging again at 110°C.     

HLDPE/organic functionalized SiO2 nanocomposites with improved thermal stability and mechanical properties

High-pressure low-density polyethylene (HLDPE)/organic functionalized SiO₂ nanocomposites were synthesized using melt-blending technique in a sigma internal mixer. The properties of the nanocomposites were studied using two different organic functional modifiers: diglycidyl ether of bisphenol-A (DGEBA) and triacetoxyvinylsilane. Reinforcing, thermal stability and toughening effects of organic functionalized nanosilica on the polymer matrix were found at loading of 2.5% nanosilica functionalized with 2.8% of DGEBA and silane coupling agent respectively. Organic functionalization on the nanosilica particle surface led to different microstructures when compared with that of the pure polymer. Organic functionalization on the nanosilica particle surface produced good interfacial adhesion and homogeneous dispersion in the polymer matrix, while the use of nanosilica resulted in aggregated silica particles in the polymer matrix. There was no significant improvement in thermal stability and mechanical properties when only nanosilica was added to the pure polymer. On the contrary, the addition of pretreated nanosilica with organic functional modifiers led to an increase of thermal stability from 313–363°C, elastic modulus and toughness from 0.12–0.18 GPa and 3.23–9.81 MJ/m³ respectively.     

Preparation and Properties of Polylactic Acid (PLA)/Silica Nanocomposites

Surface-modified silica was incorporated into bio-based polylactic acid (PLA) to improve its performance. The modification by aminosilane on the silica was confirmed through FTIR (Fourier transform infrared) spectra. Following the aminosilane modification, polyethylene glycol methyl ether (PEGME) was grafted, via the aminosilane, on the silica to form the desired surface-modified silica (PEGME-silica). The grafting percentage of polyethylene glycol methyl ether was about 6.9 wt%. Unmodified silica, having underwent a similar treatment to maintain the same thermal history but without adding silane and PEGME, was also prepared. The PEGME-silica system had slightly higher tensile strength than the unmodified silica system, with a rheological study showing an enhanced polymer matrix-dispersed silica interaction and better dispersion in morphology observations being proposed as the cause. The dynamic storage modulus in the terminal zone was reduced for large amounts of highly dispersed surface-modified silica in comparison with unmodified silica. Tan δ decreased significantly with increasing unmodified silica contents in the low frequency region, resulting in solid-like behaviors. On the other hand, there was only a limited decrement for modified silica-filled samples in the corresponding ranges, especially for low dosages of the modified silica. The shear thinning phenomenon appeared to be more pronounced for unmodified silica at high silica content, but not for modified silica. To the best of our knowledge, this is the first report of the effect of polyethylene glycol methyl ether (PEGME)-modified nanosilica on the properties of PLA/silica nanocomposites prepared under a melt mixing process to illustrate the significance of surface modification via Cole–Cole plots.