Small range 文档类型:"3"

Totally found 5320 items.

  • [期刊] Time‐temperature‐transformation diagram of modified resol phenolic resin and the thermomechanical performance of resol phenolic resin/glass fabric composite

    In this paper, modified resol phenolic resin (MPR) and its glass fabric prepreg (MPR/GF prepreg) were fabricated via a hot melt preimpregnated method. To optimize the curing schedule in curing completion, safe processing window, and storage stability conditions, time‐temperature‐transformation diagram dynamic rheological behavior of MPR was established based on such phenomenological changes as viscosity, gelation, and vitrification. The curing behavior of MPR/GF prepreg was further clarified using online monitored dynamic mechanical analysis. At last, thermogravimetric analysis and dynamic mechanical analysis tests were conducted to evaluate the thermomechanical properties of MPR/GF composite. The excellent thermomechanical performance of MPR/GF composite suggests the important role of time‐temperature‐transformation diagram in optimizing the curing cycle and the overall dynamic mechanical properties of the composite.

  • [期刊] Preparation and properties of nanocomposites composed of a water-soluble nylon and chitin nanofibers
    Nanocomposites composed of a water-soluble nylon (P-70, polyalkyleneoxide-modified poly(-caprolactum), and chitin nanofibers (ChNFs) were prepared by a casting method of the aqueous resin/fiber dispersion. P-70 was crosslinked with a resol-type phenolic resin (PR) and its ChNF nanocomposites were prepared to provide water resistance. The P-70/PR and P-70/PR/ChNF exhibited excellent water-resistance. The FT-IR analysis revealed that the crosslinked structure was formed by the reaction of amide groups of P-70 and methylol groups of PR. The glass transition temperature (T-g) of P-70/PR increased with increasing PR content, whereas the dispersion of ChNFs was deteriorated. Although the addition of ChNF to P-70 hardly affected the T-g, the addition of ChNF to P-70/PR caused a lowering of T-g. The tensile strength and modulus for P-70/ChNF nanocomposites increased with increasing ChNF content. The tensile strength of P-70/PR was lower than that of P-70, which increased by the addition of ChNF.
    Glass fiber reinforced composites are widely used in the various industrial applications. The present study deals with the experimental investigation on the manufactured compositeswith the aid of the phenolic resin. The specimens were prepared as per ASTM. Standard with two different fibre: resin ratios. The effect of various drilling parameters affects the mechanical properties of the composites with the aid of Taguchi L9 orthogonal array. The drilling performance was evaluated in terms of thrust force, torque, delamination and surface roughness. The best performance characteristics were obtained with 8 mm drill bit when drilling of phenolic resin (25:75%) composites with the higher cutting point angle of 140°, feed rate of 0.2 m/min and lower cutting speed of 1500 rpm. Similarly in 30:70% composites with the point angle of 140°, lower feed rate of 0.1 m/min and higher cutting speed of 3500 rpm the performance was good.
  • [期刊] Synthesis and characterization of novel phenolic resin/silicone hybrid aerogel composites with enhanced thermal, mechanical and ablative properties
    A novel lightweight phenolic resin/silicone (PR-Si) hybrid aerogel composite was fabricated through vacuum impregnation using PR-Si hybrid aerogels as matrix and low density (0.184 g/cm(3)) carbon-bonded carbon fibre as 3-dimensional reinforcement. The PR-Si hybrid aerogels was synthesized through a facile sol-gel polymerization, accompanied by solvent exchange and ambient pressure drying from a mixture of PR and methyltrimethoxysilane (MTMS) with ethylene glycol as the porogen and hexamethylenetetramine as the catalyst. The hybrid aerogels possess hierarchically micro-meso-macroporous structure and higher thermal stability than that of the pristine PR aerogels. The obtained aerogel composites exhibit low density (0.312-0.356 g/cm(3)), high compressive strength (0.76-4.08 MPa), low thermal conductivity (0.098-0.240 W/(mK)), and good thermal ablative and insulative properties in oxyacetylene flame simulated high temperature environment (linear ablation rates as low as 0.073 mm/s and internal temperature peaks below 200 degrees C at 38mm in-depth position as the surface temperature approximately 1800 degrees C). (C) 2017 Elsevier Ltd. All rights reserved.
  • [期刊] Improvement the mode I interlaminar fracture toughness of glass fiber reinforced phenolic resin by using epoxidized soybean oil
    In this study, the epoxidized soybean oil (ESO) was successfully synthesized from soybean oil based on its double bond, and used to synthesize the ESO-modified phenolic resin via reaction between ESO, phenol and formaldehyde. The ESO contents used in this study vary in range from 0 to 40 wt%. Then, the obtained ESO modified phenolic resin (ESO-PR) was used as resin matrices to fabricate glass-fiber-based composites by using prepreg technique. The chemical structures of both epoxidized soybean oil and phenolic resin modified with epoxidized soybean oil were confirmed with the help of Fourier transform infrared spectrometry (FTIR). The mechanical characteristics of fabricated composite materials examined include the tensile property, flexural property, impact property as well as the mode I interlaminar fracture toughness, while the morphology composite materials were also confirmed by scanning electron microscopy. The test results showed that at 20 wt% of ESO-PR, the mode I interlaminar fracture toughness for both propagation and initiation, the tensile strength, flexural strength and impact strength were increased by 78.3 and 84.5%, 7.0%; 20.5 and 39.7%, respectively. The scanning electron microscopy (SEM) observation indicated that the fracture surface of the modified composite was rougher when compared to the fracture surface of the pristine composite, and hence more energy was needed for the crack to propagate.
  • [期刊] Improved thermal stability of phenolic resin by graphene-encapsulated nano-SiO2 hybrids
    Phenolic resin (PR) modified with hybrids of reduced graphene oxide (RGO)-encapsulated nano-SiO2 (SiO2-RGO) was prepared by a simple method. The synergistic effect of RGO and nano-SiO2 was achieved in the thermal decomposition of the modified PR. Thermal stability of SiO2-RGO and the modified PR was evaluated by thermogravimetric analysis (TG). With 1 mass% loading of SiO2-RGO, the maximum decomposition temperature (T-dmax) of the modified PR was increased by 32.50 degrees C and the residual mass at 800 degrees C was increased by 6.54%. The structure of the resin char was characterized to study the mechanism of ameliorative thermal stability. SiO2-RGO hybrids were conducive to induce the PR to form graphitized carbon in the pyrolysis process. Thus, SiO2-RGO can facilitate the application of PR in the fields of heat insulation and ablation resistance.
  • [期刊] Effect of reciprocating and unidirectional sliding motion on the friction and wear of phenolic resin based composite
    Purpose The purpose of this paper is to investigate the effect of reciprocating and unidirectional sliding motions on friction and wear of phenolic resin-based composite.
  • [期刊] Phase and microstructural evolution of low carbon MgO-C refractories with addition of Fe-catalyzed phenolic resin
    In the present paper, phase and microstructural characterization of low carbon MgO-C refractories with addition of Fe-catalyzed phenolic resins as binder were investigated. Initially, phenolic resin was modified using various amounts of Fe particles as catalyst originated from iron nitrate ([Fe(NO3)(3)center dot 9H(2)O]). The MgO-C matrix compositions were prepared by using 7% of modified phenolic resin, shaped and cured at 200 degrees C for 24 h. The cured samples were coked in the temperature range from 800 to 1400 degrees C and then characterized by XRD and FE-SEM techniques. Based on attained results, in-situ graphitic carbons, particularly in carbon nanotubes (CNTs) network were gradually formed from Fe-catalyzed phenolic resin in the matrix of MgO-C refractory bodies. It was also clarified in comparison with sample containing as-received phenolic resin, more ceramic whiskers such as Al4C3, AIN, MgO and MgAl2O4 were formed in the matrix of MgO-C specimens with addition of Fe-catalyzed phenolic resin binder and significally increased with coking temperature. Microstructural observation showed the graphitic carbons like CNTs and ceramic whiskers mainly formed in the bonding phase between the aggregates, that certainly leads to enhancement of physical and mechanical properties of MgO-C refractories.
  • [期刊] Peering into the structural evolution of glass-like carbons derived from phenolic resin by combining small-angle neutron scattering with an advanced evaluation method for wide-angle X-ray scattering
    The structural evolution of two non-graphitizing glass-like carbons derived from a liquid resole and a solid novolac-type phenolic resin was quantitatively characterized by combining small-angle neutron scattering (SANS) with an advanced evaluation for wide-angle X-ray scattering (WAXS) data. Utilizing these two methods allowed for studying the microstructure on the Angstrom level (graphene stacks, WAXS) and the inaccessible microporosity (SANS). The applied WAXS analysis provided quantitative structural parameters for both, size and disorder in the polyaromatic sp(2) microstructure. Hence, the combined SANS-WAXS analysis yielded comprehensive insights into the relation between the graphene microstructure and the inaccessible porosity upon heat treatment for glass-like carbons, i.e. a nongraphitizing class of carbon. In particular, the analogue investigation of a graphitizing mesophase pitch demonstrates the major impact of the chemical composition of the utilized carbon precursor. For the glass-like carbons the results revealed different growth rates for the lateral extent of the basic structural units (L-a) depending on the temperature range, finally reaching 12 nm, whereas the stack height (L-c) exhibiting 2.2 nm is hardly affected by the thermal processing up to 3000 degrees C. As a major finding our study thus relates the evolution of microstructure and porosity to changes in chemical composition. (C) 2018 Elsevier Ltd. All rights reserved.
  • [期刊] Effect of phenolic resin thickness on frequency-dependent dynamic mechanical properties of Nomex honeycomb cores
    Using the mixed experimental/numerical method, the frequency-dependent transverse shear moduli (TSM) and damping values of the commercially available Nomex honeycomb cores were investigated. Four kinds of honeycomb cores with different phenolic resin thicknesses were used to explore the effect of the phenolic resin thickness on these dynamic mechanical properties. Results reveal that both the TSM and damping values have positive logarithmic relationships with the frequency, and the sensitivity of these dynamic mechanical properties to frequency is higher for the honeycomb core with thicker phenolic resin. Among all the transverse shear directions, TSM and damping values in the LT direction are the highest at medium and high frequencies. Compared with the damping values, the effect of phenolic resin thickness on TSM is more obvious. Therefore, it is a more efficient way to enhance the TSM than to improve the damping values by controlling the thickness of phenolic resin.