Composites Of Resin Research Articles

Evaluation of mechanical properties of untwisted carbon nanotube yarn for application to composite materials

Abstract Carbon nanotubes (CNTs) with superior mechanical properties have been of interest as reinforcement for polymer composites. However, the length of individual CNTs is limited. As a solution, yarns spun by twisting together multi-walled carbon nanotubes (MWCNTs) have been reported. In this study, untwisted CNT yarns were prepared by a non-conventional method drawing CNTs through a die. The MWCNTs in these yarns are held together by strong van der Waals forces that arise due to the interactions on the long and smooth surfaces of the MWCNTs. Here, mechanical properties of untwisted CNT yarn were studied by tensile tests. The strength of the CNT yarn was increased by increasing the apparent density of the yarn. The CNT yarns showed high tensile strength of 1 GPa and elastic modulus of 79 GPa at a yarn diameter of 35 μm. The interfacial shear strength between the CNT yarn and epoxy resin was studied by the microdroplet method, and it was very low. The wettability of the CNT yarn was affected by a type of curing agent. A unidirectional composite of epoxy resin and CNT yarn was prepared by the pultrusion molding method. Mechanical properties of the unidirectional composite were affected by the type of curing agent.

Structural mass irregularities and fiber volume influence on morphology and mechanical properties of unsaturated polyester resin in matrix composites

This paper presents the comparative results of a current study on unsaturated polyester resin (UPR) matrix composites processed by filament winding method, with cotton spun yarn of different mass irregularities and two different volume fractions. Physical and mechanical properties were measured, namely ultimate stress, stiffness, elongation%. The mechanical properties of the composites increased significantly with the increase in the fiber volume fraction in agreement with the Counto model. Mass irregularities in the yarn structure were quantitatively measured and visualized by scanning electron microscopy (SEM). Mass irregularities cause marked decrease in relative strength about 25% and 33% which increases with fiber volume fraction. Ultimate stress and stiffness increases with fiber volume fraction and is always higher for yarn with less mass irregularities.

Benzoxazine resin/carbon nanotube nanostructured composite's degradation kinetic.

In the last decades a new class of thermoset phenolic resin is emerging as a substitute of the traditional epoxy and phenolic resins in the aircraft industry. This new class is called polybenzoxazines and its associates the epoxy resin's mechanical properties and phenolic resin's thermal and flame retardant properties, resulting in a resin with superior properties when analyzed with the others singly. The introduction of carbon nanotubes in low concentration into polymeric matrices can produce nanostructured materials with good properties. Thus, in this study, nanostructured composites of benzoxazine resin were processed with different concentration of carbon nanotubes (0.1%, 0.5% and 1.0% w/w). In order to evaluate the thermostability of the benzoxazine resin and its nanostructured composites, it was performed a degradation kinetic study using the thermogravimetric technique. For that, the analysis have been done with the temperature ranging from 25 degrees C to 1000 degrees C at nitrogen atmosphere (100 mL x min(-1)) and in different heating rates (2, 4, 6, 8, 10 and 20 degrees C x min(-1)), in order to obtain the kinetic parameters (activation energy, E(a), and pre-exponential factor, A), based on Ozawa-Wall-Flynn model. The results showed excellent agreement between the thermogravimetric curves obtained and the Ozawa-Wall-Flynn method. The degradation kinetic study showed that the introduction of carbon nanotubes in the benzoxazine matrix does not change the thermostability of the resin, so that it does not have a significant influence in the shelf life of the material.

Mechanical and thermal properties of epoxy-POSS reinforced-(biphenyl diol formaldehyde/epoxy hybrid resin) composites

To enhance the properties of epoxy composites, the biphenyl diol formaldehyde resin (BPFR) and glycidyloxypropyl polyhedral oligomeric silsesquioxane (G-POSS) were synthesized and used for modification of fiber-glass reinforced composites of epoxy resin (ER). The BPFR was employed to cure epoxy resin with different G-POSS contents and the laminates of fiber-glass reinforced hybrid composites prepared from BPFR, ER and G-POSS. The dynamic mechanical properties, thermal properties, mechanical and electrical properties of the hybrid composites were characterized by dynamic mechanical analyzer, thermogravimetric analyzer and electroproperty detector. The results showed that the T g of the composites is increased with the addition of G-POSS. When the content of G-POSS is 5 wt%, the tensile and impact strength of the hybrid composites are 249.87 MPa and 63.83 kJ/m2, respectively, which are all 30 % higher than those of non-added composites. At G-POSS content of 7 wt%, T g of the material is 9.6 °C higher than pure BPFR/ER composite, and the initial decomposition temperature, T id, is enhanced by about 29 °C. Dielectric constant, e, and dielectric loss, tanδ, of the hybrid composites are between 0.53–0.7 and between 0.004–0.012, respectively.

Interfacial charge behaviour at dielectric - dielectric interfaces

Multi-dielectric insulation systems are commonly used in high voltage apparatus. Interfacial charge accumulated at the dielectric - dielectric interface governs the dielectric behaviour of the composites considerably. In this work, we perform space charge measurements on polymeric composites of epoxy resin and polyethylene, to investigate the behaviour of interfacial charge at the interfaces, under various experimental conditions. Pulsed Electro-Acoustic (PEA) system is used for measurement of charge distribution. The interfacial charge at the discontinuities, in similar as well as dissimilar dielectrics, is studied. Interfacial charge is seen to develop at discontinuities within otherwise homogeneous materials. Accumulation of space charge above threshold fields, at interfaces of different materials, ultimately dominates the polarity and magnitude of accumulated charge.

Ultrasonic properties of epoxy resin/marble waste powder composites

Non‐destructive techniques are suitable alternatives for characterization of composites. The aim of this study is to analyze the composites of epoxy resin (ER)/marble waste powder (MWP) by ultrasonic method. The effects of marble powder, coagulant type, and dosage on the ultrasonic properties of ER/MWP composites were investigated. The ultrasonic wave velocities of composites were measured with the pulse–echo method at room temperature by a flaw detector. The values of the acoustic impedance, Poisson's ratio, and elastic constants of the samples were calculated by the measured values of the densities and both longitudinal and shear ultrasonic wave velocities. According to the results, the ER/MWP composite using sepiolite coagulant in dosages of 4 g/500 mL has showed the highest values of elastic constants. POLYM. COMPOS. 36:584–590, 2015. © 2014 Society of Plastics Engineers

Dispersion and resistivity optimization of conductive carbon black in environment‐friendly conductive coating based on acrylic resin

A designated chemical structure, determined through the analysis of elements and groups on the surface of conductive carbon black (CB), alcohol‐soluble acrylic resin used for dispersion of conductive CB was successfully prepared based on the principles of similar structure complex well. The content of acrylic acid, glass transition temperature (Tg), molecular weight (Mw), self‐crosslinking degree, and N‐hydroxymethyl acrylamide content were investigated to optimize the electrical conductivity and dispersion effect of conductive CB in coating. The composites of acrylic resin and conductive CB were characterized by X‐ray photoelectron spectroscopy for surface chemical structure on CB, scanning electron microscopy for morphology of conductive coating, Fourier transform infrared for groups in acrylic resin, and digital multimeter techniques for surface resistivity of conductive coating. The optimum surface resistivity of the acquired conductive coating could reach 600 ohm/sq, showing an excellent conductive property. Moreover, the conductive coating still maintained a lower resistivity after salt spray and weather resistance test. POLYM. COMPOS. 36:467–474, 2015. © 2014 Society of Plastics Engineers

Investigation on flame retardancy, combustion and pyrolysis behavior of flame retarded unsaturated polyester resin with a star-shaped phosphorus-containing compound

The phosphorus-containing star-shaped flame retardant (TRIPOD-DOPO) was synthesized, while the flame retardant unsaturated polyester resins (FR-UPRs) composites with various amounts of TRIPOD-DOPO were prepared. The thermogravimetric analysis (TGA) and oxygen index (OI) results showed that the incorporation of TRIPOD-DOPO improves the thermal stability and flame retardancy of UPR. The combustion properties of composites were evaluated by microscale combustion calorimeter (MCC), and the results indicated that TRIPOD-DOPO decreased the peak heat release rate (pHRR) and total heat release (THR) of UPR. Fourier transform infrared coupled with the thermogravimetric analyzer (TG–IR) revealed that UPR and TRIPOD-DOPO decomposed independently of each other. Flame inhibition was expected to occur in the gas phase. Under the air condition, TRIPOD-DOPO showed a more obviously condensed phase interaction increasing charring from the TG results. The SEM results showed that the residual char of composites were more compact and continuous, which could prevent mass and thermal transfer.

Material characteristics and residual bond properties of organic and inorganic resins for CFRP composites in thermal exposure

This paper presents the residual characteristics of organic and inorganic resins for structural retrofit using carbon fiber reinforced polymer (CFRP) composites exposed to thermal stress states. A three-phase experimental program is carried out to study the behavior of the inorganic resin, CFRP composites, and resin-concrete interface at elevated temperatures ranging from 25°C to 200°C. The properties of the inorganic resin demonstrate strong dependency on curing time and are influenced by the degree of temperature exposure. CFRP composites show a decrease in strength and modulus with an increasing temperature due to the degradation of bond between the fibers and resin. The inorganic resin exhibits better thermal stability than the organic resin, whereas the former illustrates a lower strength than the latter because of insufficient stress-transfer. The composites have failed abruptly, regardless of resin types. The interfacial fracture energy of the resins is reduced with temperature, including the deteriorated morphology of the interface between the concrete substrate and the resin.

Estimation of the biobased carbon content of polypropylene resin in composites on the basis of the carbon 14 concentration

ABSTRACTThe aim of this study was to estimate a procedure for the biobased carbon content of polypropylene (PP) resin isolated from composites containing additives or fillers on the basis of the carbon 14 concentration ratio, as measured by accelerated mass spectrometry (AMS). To reliably estimate the biobased carbon content of plastics, additives and fillers in the composites had to be removed because they often contain significant amounts of biobased carbon. To obtain specimens with purity suitable for estimation, an isolation procedure for PP from the composites was devised. The dissolution of the composites in 1,2,3,4‐tetrahydronaphthalene at 150°C, followed by immediate centrifugation of the hot solution, yielded PP as semicrystalline precipitates by allowing the hot solution to cool during centrifugation. The recovery of the resin through the scooping off of the precipitates was typically 90%. This simple procedure provided a suitable specimen for the estimation of biobased carbon content by AMS on the basis of ASTM D 6866. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014, 131, 39978.

Phenylphosphine oxide containing polyimide matrix resins for atomic oxygen-resistant fiber-reinforced composites

Phenylethynyl-endcapped imide oligomers with different calculated molecular weights (calcd number average molecular weight ([Formula: see text])) and phosphorous (P) contents (P loading) were synthesized by the reaction of diethyl ester of 4,4′-oxydiphthalic acid, monoethyl ester of 4-phenylethynyl phthalic acid, and the P-containing diamines including [2,5-bis(4-aminophenoxy)phenyl] diphenylphosphine oxide and di(3-aminophenyl)methylphosphine oxide via in situ polymerization of monomeric reactant method. The amide–ester solutions were impregnated with carbon fiber (Cf) and quartz fiber (Qf) cloth to give high quality prepregs that were then thermally cured to yield the Cf-reinforced polyimide (PI) composite (Cf/PI) and Qf-reinforced PI composite (Qf/PI), respectively. The Cf/PI composites showed high mechanical properties with a flexural strength of 1554 ± 93 MPa, a flexural modulus of 112 ± 3 GPa and an interlayer shear strength of 90 ± 5 MPa, respectively. The atomic oxygen (AO) resistances of the neat resins and composites were evaluated on a ground-based simulation facility. Experimental results indicated that the P structures offer PIs with 55–75% lower weight losses and a self-healing property. The fiber-reinforced composites showed further lower erosion rates than neat resins. In addition, the effects of calcd [Formula: see text] and P loadings on the melt processabilities of the B-staged imide oligomers and the AO resistance of the cured PIs were systematically investigated.

Immobilization of flame-retardant onto silica nanoparticle surface and properties of epoxy resin filled with the flame-retardant-immobilized silica (2)

To prepare silica nanoparticle having flame-retardant activity, immobilization of flame-retardant onto the surface was investigated. The immobilization of phosphorous flame-retardant was achieved by two-step reactions: (1) introduction of cyclotriphosphazene (PH) groups onto silica nanoparticle by the reaction of terminal amino groups of the surface with hexachlorocyclotriphosphazene and (2) immobilization of bis(4-aminophenoxy)phenyl phosphine oxide (BAPPO) onto silica having PH groups by the reaction of PH groups on the surface with BAPPO. The immobilization of BAPPO was confirmed by FT-IR and thermal decomposition GC–MS. The composite of epoxy resin filled with BAPPO-immobilized silica (Silica–PH–BAPPO) was successfully prepared by heating in the presence of curing agents. Thermal decomposition temperature and glass transition temperature of the epoxy resin filled with Silica–PH–BAPPO was higher than that of epoxy resin filled with untreated silica, free HCTP and BAPPO. Moreover, flame-retardant property of epoxy resin filled with Silica–PH–BAPPO was estimated by limiting oxygen index (LOI). The LOI value of epoxy resin filled with Silica–PH–BAPPO was higher than that of epoxy resin filled with untreated silica, free HCTP and BAPPO. This may be due the fact that char yield of the epoxy resin filled with Silica–PH–BAPPO was higher than that filled with free flame-retardant.

Thermal and Mechanical Properties of Novel Composites of Methyl Silicone Polymer and Partially Ceramized Rice Bran

Rice bran (RB), rich in carbon and silicone, is an agricultural waste that is abundantly available in rice producing countries. In this work, composites of a preceramic methyl silicone resin (MSR) and RB were prepared by blending powdered RB with a molten MSR at 110 °C at various ratios in a Brabender-type static mixer. Composites were made from them by compression molding and cross-linking at 260 °C under 20 MPa pressure. The thermal, mechanical, and chemical properties of the produced composites were assessed by thermogravimetric analysis, scanning electron microscopy, and FT-IR and by measuring compressive strength and hygroscopic expansion. It was found that RB was partially ceramized and decomposed to carbonaceous materials during cross-linking. The water absorption and hygroscopic expansion of the MSR/RB composites were increased but the compressive strength was decreased with an increase in the weight % of RB. The highest compressive strength was shown by the composites made from the 50/50 blends, which was 27.61 MPa. The developed composites showed an excellent compressive strength and also very low water absorption and hygroscopic expansion.

Improvement of Mechanical Properties of Noil Hemp Fiber Reinforced Polypropylene Composites by Resin Modification and Fiber Treatment

The present study aims to improve the reinforcement of hemp fibre to polypropylene (PP) by simple resin modification and fibre treatment. Maleic anhydride grafted polypropylene (MAPP) was used as resin modifier by direct mixing with PP, and hydrophobically modified hydroxyethyl cellulose (HMHEC) was used as fibre treatment reagent by immersing fibre into its aqueous solution. The influences of fibre content, resin modification, and fibre treatment on the mechanical properties (tensile, flexural, and impact strengths) of composites were investigated. The change of interfacial bonding between fibre and resin in composites caused by MAPP and HMHEC was studied by scanning electron microscopy and dynamic mechanical analysis. Resin modification and fibre treatment were effective to enhance the mechanical properties of the composites. The improvement in interfacial bonding is quantitatively evaluated with adhesion factor.

Micro-hardness and contraction stress evaluation of bulk-fill resins composites

Micro-hardness and contraction stress evaluation of bulk-fill resins composites

Effectiveness of amine functional aniline furfuraldehyde condensate as toughening agent for epoxy resin

PurposeThe purpose of this paper is to find a new toughening agent for diglycidyl ether of bisphenol A (DGEBA) resin and to check effectiveness of this new toughening agent to obtain toughness and chemical resistance of cured epoxy.Design/methodology/approachFor this purpose, an investigation was carried out to synthesise, characterise and to study the toughening reaction of amine functional aniline furfuraldehyde condensate (AFAFFC) with DGEBA resin. AFAFFC was first synthesised from the reaction of aniline and furfuraldehyde in the acid medium (pH‐4) and characterised by FT‐IR spectroscopy, elemental analysis and concentration of primary and secondary amine analysis. Then various formulations were made by mixing DGEBA, AFAFFC and ambient temperature curing agent triethylene tetramine (TETA) in different compositions and the modified networks were evaluated to their mechanical and thermal properties. The dynamic mechanical analysis (DMA), scanning electron microscopy (SEM) studies and thermogravimetric analysis (TGA) of toughened epoxy were also reported.FindingsThe resulting networks developed a two‐phase microstructure upon network formation and displayed significantly improved fracture toughness. The dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM) studies showed two‐phase morphology in the cured networks where AFAFFC particles were dispersed. TGA showed that the AFAFFC modified epoxy network was thermally stable up to around 311°C.Research limitations/implicationsThe toughening agent AFAFFC has been synthesised by using aniline and furfuraldehyde. By changing amine and aldehyde other toughening agents could be synthesised and efficiency of these toughening agent for epoxy resin could also be studied.Originality/valueThe method for toughening of epoxy resin (DGEBA) is novel and relevant, as the toughened products have high performance applications in protective coatings, adhesives for most substrates and matrix resins for composites.

Phenylethynyl-endcapped polymerizable monomer reactants poly(amic ester) resins for high impact-toughened carbon fiber composites

Toughened polymerizable monomer reactants (PMR) poly(amic ester) matrix resins were prepared by the reaction of the diesters of aromatic dianhydrides (3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) and/or 2,3′,3,4′-biphenyltetracarboxylic dianhydride) and aromatic diamines (the mixture of 3,4′-oxydianiline and 1,3-bis(4-aminophenoxy)benzene) in the presence of monoester of 4-phenylethynyl phthalic anhydride as the end-capping agent using ethanol as solvent. The PMR matrix resins owned the characteristic of high resin concentration and low viscosity, suitable for impregnating carbon fibers (Cfs) to give high-quality Cf prepreg. The B-staged imide oligomers prepared by thermal baking of the PMR matrix resins at the temperature of ≤240°C showed good meltability at elevated temperatures. The polyimide (PI) neat resins prepared by thermally curing the B-staged oligoimide resins at 370°C showed good combined thermal and mechanical properties. The Cf/PI composite (T300/PI) showed high impact toughness, with compression strength after impact of as high as 260 MPa. Unidirectional laminates had high mechanical properties at room temperature and high strength retention at 250°C, with 97.4% for flexural modulus, 53.3% for flexural strength, and 48.8% for interlaminar shear strength, demonstrating that the high impact-toughened Cf/PI composite could be long-term served at a temperature as high as 250°C.

Influence of glass and sisal fibers on the cure kinetics of unsaturated polyester resin

The effect of grinded glass and sisal fibers (25 vol%) on the cure kinetics of composites of unsaturated polyester resin (UPR) was investigated by differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The DSC analysis was carried out at four different heating rates (5, 10, 20 and 40 °C/min), and the cure enthalpy and activation energy (Ea) were determined according to the Flynn-Wall-Ozawa (FWO) method. The results showed that increasing heating rates promoted reduced reaction times. The sisal fiber-containing composites exhibit higher activation energy values for the cure process in comparison with the neat polyester resin and the glass fiber composites. This can be due to the presence of polar groups in the sisal components, which physically interact with the polyester resin and retard the cure reaction. Hence, as sisal fiber retarded the cure reaction of the UPR resin, it is suggested that the use of natural fibers in polymer matrix composites can affect the cure kinetics of the polyester resin.

Evaluation of the Influence of Eugenol in Dental Leakage in Composite Resins Restorations in Deciduous Teeth

Objective: to evaluate dental leakage in composite resin restorations carried through on the lining with zinc oxide and eugenol in molar deciduous. Methods: For the study, had been used 24 deciduous molars, which had been divided in three groups, in accordance with the moment where the resin restoration was carried through: G1= immediately after insertion of the IRM, G2= after 48 hours and G3= after 28 days. A occlusal socket was carried through, in all the teeth, with a drill 3018 HL (KG Sorensen). After restored, the teeth had been covered enamel layer and wax, leaving itself around exempts a region of 1, of the restoration. The teeth had been, then, immersed in rodamina dye 0.5% during 24 hours. After it was removed the enamel and the wax, and the teeth had been washed, dried and cut with a machine of precision cut (Labcut 1010). The specimens had been evaluated in a Stereo Microscope (Olympus SZH 10) and classified by levels of infiltration of 0 the 3. Results: Through the analysis statistics, a significant association was evidenced enters the presence of infiltration and the period where the restoration was carried through. It was observed that in the immediate period dental leakage had a minor and in the period of 28 days a bigger infiltration (p=0.02). Conclusion: It is important that there is not much time between temporary restoration with IRM and final restoration with composite resin to decrease microleakage.

Development of soy-based adhesives for the manufacture of wood composite products

Abstract Soy-based resins have recently attracted great attention as adhesives in the wood composite industry. This article is focusing on hydrolysis and modification of soy protein concentrates to formulate soy-based resins for wood composites. The soy-based resins have been evaluated in terms of bondability on wood substrates and bonding performance in plywood products. The performance of plywood was found to meet the relevant CSA standard (Canadian Standard Association) requirements under both of dry and wet conditions, if the soy-based resins were obtained from low hydrolyzed soy flour. Hydrolysis is an effective and efficient tool for reducing the viscosity of soy resins. However, hydrolysis also reduces the bond strength of soy-based resins as hydrolysis cleaves the macromolecules of soy proteins into smaller molecules. Modified soy-based resins have a certain potential for production of interior- and exterior-used plywood.