Mechanical Properties of Bio-Composites Based on Epoxy Resin and Nanocellulose Fibres

The aim of our research was to investigate the effect of a small nanocellulose (NC) addition on an improvement of the mechanical properties of epoxy composites. A procedure of chemical extraction from pressed lignin was used to obtain nanocellulose fibers. The presence of nanoparticles in the cellulose pulp was confirmed by FTIR/ATR spectra as well as measurement of nanocellulose particle size using a Zetasizer analyzer. Epoxy composites with NC contents from 0.5% to 1.5% w/w were prepared. The obtained composites were subjected to strength tests, such as impact strength (IS) and resistance to three-point bending with a determination of critical stress intensity factor (Kc). The impact strength of nanocellulose composites doubled in comparison to the unmodified epoxy resin (EP 0). Moreover, Kc was increased by approximately 50% and 70% for the 1.5 and 0.5% w/w NC, respectively. The maximum value of stress at break was achieved at 1% NC concentration in EP and it was 15% higher than that for unmodified epoxy resin. The highest value of destruction energy was characterized by the composition with 0.5% NC and corresponds to the increase of 102% in comparison with EP 0. Based on the analysis of the results it was noted that satisfactory improvement of the mechanical properties of the composite was achieved with a very small addition of nanofiller while other research indicates the need to add much more nanocellulose. It is also expected that this kind of use of raw materials will allow increasing the economic efficiency of the nanocomposite preparation process. Moreover, nanocomposites obtained in this way can be applied as elements of machines or as a modified epoxy matrix for sandwich composites, enabling production of the structure material with reduced weight but improved mechanical properties.

Study on Thermal Stability Properties of Epoxy Matrix/Fluorine and Silicon Composites

Fluorine and silicon resin has excellent thermal stability properties. The thermal stability properties of polymers modified by fluorine and silicon resin can be improved. In this paper, fluorine and silicon resin has been prepared by (1,3,5-tris(trifluoropropylmethyl)-cyclotrisiloxane and 3-aminopropyltriethoxysilane. The FTIR spectra and the 1H NMR spectrum showed the structure of fluorine silicon resin. The thermo gravimetric traces indicated that fluorine silicon resin had improved the thermal stability properties of epoxy matrix resin significantly. The temperature of decomposition velocity of unmodified epoxy matrix resin and modified epoxy matrix resin began to increase rapidly were 356oC, 375oC respectively. The final weight fraction of unmodified epoxy matrix resin and modified epoxy matrix resin were 4.6%, 6.5% , respectively. The temperature of the maximum rate of degradation were 398oC, 420oC, respectively.

Synthesis and Characterization of Imide Containing Hybrid Epoxy Resin with Improved Mechanical and Thermal Properties

Phosphorous containing amine, tripropyldiamine phosphine oxide (TPDAP), and hybrid monomer 4-(N-phthalimidophenyl) glycidylether (PPGE) were synthesized and characterized by Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and elemental analysis (EDX). PPGE was incorporated in bisphenol A epoxy resin (BPA) in various concentrations (5% to 20%), based on a weight percentage of BPA resin. Curing was carried out with the stoichiometric amount of TPDAP and 1,3-propanediamine (PDA) to result in cross-link network. Various mechanical, chemical, thermal, and flame retardant properties of modified and unmodified epoxy resin were studied. The coatings obtained with the addition of PPGE were found to have improved properties as compared with those of the unmodified resin. Coatings with 15% loading of PPGE showed improved flame retardant and mechanical properties with stable thermal behaviour.

Fatigue Behaviour of a Hybrid Particle Modified Fiberglass/Epoxy Composite under a Helicopter Spectrum Load Sequence

The fatigue life of a glass fibre reinforced plastic (GFRP) hybrid composite containing 9 wt.% of rubber microparticles and 10 wt.% of silica nanoparticles, under a standard helicopter rotor spectrum load sequence was determined and observed to be about three times higher than that of GFRP with unmodified epoxy matrix. The underlying mechanisms for the observed improvements in spectrum fatigue life of GFRP composite with the hybrid matrix are discussed.

Preparation of Polyurethane-Modified Epoxy

Polyurethane (PU) prepolymer with the isocyanine-based were synthesized by toluene -2, 4-diisocyanate (TDI), polyethylene glycol (PEG-400) and polyethylene glycol (PEG-1000) with N-methylpyrrolidone as the solvent. The effects of temperature and time on the synthesis of polyurethane prepolymer were examined in this paper. The structures of PU, unmodified epoxy resin and modified epoxy resin were identified by FI-IR spectra. It was shown that polyurethane prepolymer was synthesized at 70°C for 5 hours and modified epoxy resin was synthesized successfully.

Toughening Mechanism and the Application of Epoxy Adhesive Modified by Nano-SiO2

Epoxy resin adhesives are widely used in various sectors, particularly in the aerospace and automotive industries. However, the solidification of the three-dimensional network structure of pure epoxy resin, which causes greater density and brittleness, results in poor system resilience. With the ultimate goal of improving the resilience of epoxy resin, nano-sized SiO2particles were introduced to improve the adhesion strength of both modified and unmodified epoxy adhesive. The results indicated increases of shearing strength from 16.66-Mpa to 18.01 -Mpa, impact strength from 15.4-kJ/m2 to 33.68-kJ/m2, and flexural strength from 70.5-Mpa to 80.94 Mpa.

Fracture Toughening of Epoxy Resins by Addition of a Novel Thermoplastic PPAEs

A series of blends have been prepared by adding a novel thermoplastic Poly (aryl ether) s containing phthalazinone moiety (PPAEs) in varying proportions to diglycidyl ether of bisphenol A epoxy resin (DGEBA) cured with p-diaminodiphenylsulfone (DDS). The glass transition temperature (Tg) of DGEBA /PPAEs blends were performed using differential scanning calorimetry (DSC) technique. It is proved that the addition of PPAEs resulted in enhancement of thermal properties of the blends, especially PPENK. There was moderate increase in the fracture toughness as estimated by notched impact strength. Compared to that of unmodified epoxy, the maximum toughness of the modified blends had increased 44% by addition of 15 phr PPENK. Fracture mechanisms such as plastic deformation and the ductile nature of the crack of the matrix were responsible for the increase in the fracture toughness of the blends.

Morphological Study on Room-Temperature-Cured PMMA-Grafted Natural Rubber-Toughened Epoxy/Layered Silicate Nanocomposite

A morphological study was conducted on ternary systems containing epoxy, PMMA-grafted natural rubber, and organic chemically modified montmorillonite (Cloisite 30B). Optical microscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and wide-angle X-ray diffraction (WAXD) analysis were used. The following four materials were prepared at room temperature: cured unmodified epoxy, cured toughened epoxy, cured unmodified epoxy/Cloisite 30B nanocomposites, and cured toughened epoxy/Cloisite 30B nanocomposites. Mixing process was performed by mechanical stirring. Poly(etheramine) was used as the curing agent. The detailed TEM images revealed co-continuous and dispersed spherical rubber in the epoxy-rubber blend, suggesting a new proposed mechanism of phase separation. High-magnification TEM analysis showed good interactions between rubber and Cloisite 30B in the ternary system. Also, it was found that rubber particles could enhance the separation of silicates layers. Both XRD and TEM analyses confirmed that the intercalation of Cloisite 30B was achieved. No distinct exfoliated silicates were observed by TEM. Aggregates of layered silicates (tactoids) were observed by SEM and EDX, in addition to TEM at low magnification. EDX analysis confirmed the presence of organic and inorganic elements in the binary and ternary epoxy systems containing Cloisite 30B.

Studies on the Properties of Epoxy Resins Modified with Novel Liquid Crystalline Polyurethane

Liquid crystal polyurethane (LCPBI) containing biphenylnate and imide units was synthesized and characterized and used to modify the conventional epoxy resin (E-51). Experimental results revealed that the impact strength of the epoxy resin modified with LCPBI was 2.5 times higher than that of unmodified epoxy resin, and the tensile strength as well as the bending strength was also improved. The thermal decomposition temperature of modified systems was also 15-20oC higher than that of the unmodified system, and the fracture structures of the blends was investigated by SEM.