Synthesis and characterization of bis(4‐cyanato 3,5‐dimethylphenyl) naphthyl methane/epoxy/glass fiber composites

Bis(4‐cyanato 3,5‐dimethylphenyl) naphthylmethane was prepared by treating CNBr with bis(4‐hydroxy 3,5‐dimethylphenyl) naphthylmethane in the presence of triethylamine at −5 to 5°C. The dicyanate was characterized by FT‐IR and NMR techniques. The prepared dicyanate was blended with commercial epoxy resin in different ratios and cured at 120°C for 1 hr, 180°C for 1 hr, and post cured at 220°C for 1 hr using diamino diphenyl methane (DDM) as curing agent. Castings of neat resin and blends were prepared and characterized by FT‐IR technique. The morphology of the blends was evaluated by SEM analysis. The composite laminates were also fabricated from the same composition using glass fiber. The mechanical properties like tensile strength, flexural strength, and fracture toughness were measured as per ASTMD 3039, D 790, and D 5528, respectively. The tensile strength increased with increase in cyanate content (3, 6, and 9%) from 322 to 355 MPa. The fracture toughness values also increased from 0.7671 kJ/m² for neat epoxy resin to 0.8615 kJ/m² for 9% cyanate ester epoxy modified system. The thermal properties were also studied. The 10% weight loss temperature of pure epoxy is 358°C and it increased to 398°C with incorporation of cyanate ester resin. The incorporation of cyanate ester up to 9% loading level does not affect the T_g to a very great extent. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

A novel high performance RTM resin based on benzoxazine

Resin transfer molding (RTM) has the potential to manufacture high quality, geometrically complex composite parts. Benzoxazine is a new kind of high performance composite matrix. It can be polymerized with a ring‐opening reaction without releasing volatiles. In this article, a novel RTM resin made from aromatic diamine, phenol and formaldehyde is reported. The viscosity and curing behavior of the RTM resin as well as the properties of the cured neat resin and fiber reinforced composite were investigated. The resin has a viscosity lower than 0.5 Pa · s after 4 hr at 100°C, and can be cured at 180°C. The tensile strength, modulus, and elongation of the cast resin are 94 MPa, 4.6 GPa, and 2.2%, respectively. The flexural strength and modulus of the cast resin are 160 MPa and 4.9 GPa. The flexural strength and modulus of its glass fiber laminate are 662 MPa and 30 GPa. It is very easy to control the viscosity and curing rate of the RTM resin through the addition of reactive dilute agents and catalysts according to the requirement of RTM processing. POLYM. COMPOS., 26:563–571, 2005. © 2005 Society of Plastics Engineers     

Synthesis and characterization of bis(4‐cyanato‐3,5‐dimethylphenyl)anisylmethane/epoxy/glass fiber composites

Bis(4‐cyanato‐3,5‐dimethylphenyl)anisylmethane was prepared by treating CNBr with bis(4‐hydroxy‐3,5‐dimethylphenyl)anisylmethane and blended with commercial epoxy resin in different ratios and cured at 120°C for 2 h, 180°C for 1 h, and postcured at 220°C for 1 h using diamino diphenyl methane as curing agent. Castings of neat resin and blends were prepared and characterized. The composite laminates were also fabricated with glass fiber using the same composition. The tensile strength of the composites increased with increase in cyanate content (3, 6, and 9%) from 322 to 355 MPa. The fracture toughness values also increased from 0.7671 kJ/m², for neat epoxy resin, to 0.8615 kJ/m², for 9% cyanate ester‐modified epoxy system. The 10% weight loss temperature of pure epoxy (358°C) was increased to 390°C by the incorporation of cyanate ester resin. The incorporation of cyanate ester up to 9% in the epoxy resin increases the T_g from 143 to 147°C. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and properties of fluorinated biphenyl‐type epoxy resin

A novel fluorinated biphenyl‐type epoxy resin (FBE) was synthesized by epoxidation of a fluorinated biphenyl‐type phenolic resin, which was prepared by the condensation of 3‐trifluoromethylphenol and 4,4′‐bismethoxymethylbiphenyl catalyzed in the presence of strong Lewis acid. Resin blends mixed by FBE with phenolic resin as curing agent showed low melt viscosity (1.3–2.5 Pa s) at 120–122°C. Experimental results indicated that the cured fluorinated epoxy resins possess good thermal stability with 5% weight loss under 409–415°C, high glass‐transition temperature of 139–151°C (determined by dynamic mechanical analysis), and outstanding mechanical properties with flexural strength of 117–121 MPa as well as tensile strength of 71–72 MPa. The thermally cured fluorinated biphenyl‐type epoxy resin also showed good electrical insulation properties with volume resistivity of 0.5–0.8 × 10¹⁷ Ω cm and surface resistivity of 0.8–4.6 × 10¹⁶ Ω. The measured dielectric constants at 1 MHz were in the range of 3.8–4.1 and the measured dielectric dissipation factors (tan δ) were in the range of 3.6–3.8 × 10^?3. It was found that the fluorinated epoxy resins have improved dielectric properties, lower moisture adsorption, as well as better flame‐retardant properties compared with the corresponding commercial biphenyl‐type epoxy resins. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Maleimido-functionalized spirobislactone having enhanced volumetric expansion on polymerization

An approach to enhancing the volumetric expansion on polymerization of spirobislactone is proposed. This approach suggests a molecular modification of spirobislactone through attaching a rigid pendant segment bearing maleimido group to its aromatic ring. An additional volumetric expansion is achieved from loose molecular packing in cured resins due to the steric hindrance effect among rigid pendent segments. Thus a new monomer, maleimido-functionalized spirobislactone (MFS), is prepared. In order to evaluate the volumetric expansion of MFS during curing, tetraglycidyl 4,4′-diamino diphenyl methane (TGDDM) is employed to cure with MFS. The volumetric expansion of MFS on curing is measured to be 12.3%, higher than that of net spirobislactone monomer. The existence of loose molecular packing in MFS/epoxy cured resins is demonstrated by morphology observation of the cured resin stained by the phosphotungstic acid (PTA), and the stained regions are observed to be nanoparticles. Such a cured resin, prepared from 20 mol% of MFS and 80 mol% of TGDDM epoxy resin, shows excellent toughness (Charpy impact strength 13,000 J/m²) and good mechanical strength (flexural strength 120 MPa, storage flexural modulus 4.2 GPa). Its glass transition temperature by dynamic mechanical thermal analysis (DMA) attains 227 °C, much higher than that of the cured resin from net spirobislactone and epoxy resin.     

Biobased composites prepared by compression molding with a novel thermoset resin from soybean oil and a natural‐fiber reinforcement

Biobased composites were manufactured with a compression‐molding technique. Novel thermoset resins from soybean oil were used as a matrix, and flax fibers were used as reinforcements. The air‐laid fibers were stacked randomly, the woven fabrics were stacked crosswise (0/90°), and impregnation was performed manually. The fiber/resin ratio was 60 : 40. The prepared biobased composites were characterized by impact and flexural testing. Scanning electron microscopy of knife‐cut cross sections of the specimens was also done to investigate the fiber–matrix interface. Thermogravimetric analysis of the composites was carried out to provide indications of thermal stability. Three resins from soybean oil [methacrylated soybean oil, methacrylic anhydride modified soybean oil (MMSO), and acetic anhydride modified soybean oil] were used as matrices. The impact strength of the composites with MMSO resin reinforced with air‐laid flax fibers was 24 kJ/m², whereas that of the MMSO resin reinforced with woven flax fabric was between 24 and 29 kJ/m². The flexural strength of the MMSO resin reinforced with air‐laid flax fibers was between 83 and 118 MPa, and the flexural modulus was between 4 and 6 GPa, whereas the flexural strength of the MMSO resin reinforced with woven fabric was between 90 and 110 MPa, and the flexural modulus was between 4.87 and 6.1 GPa. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Toughening of an epoxy resin with hydroxy‐terminated poly(arylene ether nitrile) with pendent tertiary butyl groups

Hydroxy‐terminated poly(arylene ether nitrile) oligomers with pendent tert‐butyl groups (PENTOH) were synthesized by the nucleophilic aromatic substitution reaction of 2,6‐dichlorobenzonitrile with tert‐butyl hydroquinone in N‐methyl‐2‐pyrrolidone medium with anhydrous potassium carbonate as a catalyst at 200°C in a nitrogen atmosphere. The PENTOH oligomers were blended with diglycidyl ether of bisphenol A epoxy resin and cured with 4,4′‐diaminodiphenyl sulfone. The curing reaction was monitored with infrared spectroscopy and differential scanning calorimetry. The morphology, fracture toughness, and thermomechanical properties of the blends were investigated. The scanning electron micrographs revealed a two‐phase morphology with a particulate structure of the PENTOH phase dispersed in the epoxy matrix, except for the epoxy resin modified with PENTOH with a number‐average molecular weight of approximately 4000. The storage modulus of the blends was higher than that of the neat epoxy resin. The crosslink density calculated from the storage modulus in the rubbery plateau region decreased with an increase in PENTOH in the blends. The fracture toughness increased more than twofold with the addition of PENTOH oligomers. The tensile strength of the blends increased marginally, whereas the flexural strength decreased marginally. The dispersed PENTOH initiated several toughening mechanisms, which improved the fracture toughness of the blends. The thermal stability of the epoxy resin was not affected by the addition of PENTOH to the epoxy resin. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Characterization of modified bismaleimide resin

A new high-temperature resin system based on methylene dianiline bismaleimide (MDA-BMI) chemistry is studied. This is a two-component resin system which is modified by 2,2′-methylene-bis[4-methyl-6-(2-propenyl)] phenol (MBMPP) and has excellent thermal mechanical properties and good toughness characteristics. This paper discusses in detail some of the characteristics of the prepolymer by reacting the two components in addition to the cured system's properties. The prepolymer has very good stability at 100–120°C with very minimal molecular weight increase. The reaction order for curing prepolymer is almost 1. The activation energy of the curing reaction is 74.12 KJ/mol. The flexural strength and modulus of the cured modified MDA-BMI and their retention at 250°C are 124 and 3774.6 MPa and 69 and 78%, respectively. © 1996 John Wiley & Sons, Inc.     

Thermal conductivity and dynamic mechanical property of glycidyl methacrylate‐grafted multiwalled carbon nanotube/epoxy composites

The well dispersed multiwalled carbon nanotube (MWCNT)/epoxy composites were prepared by functionalization of the MWCNT surfaces with glycidyl methacrylate (GMA). The morphology and thermal properties of the epoxy nanocomposites were investigated and compared with the surface characteristics of MWCNTs. GMA‐grafted MWCNTs improved the dispersion and interfacial adhesion in epoxy resin, and enhanced the network structure. The storage modulus of 3 phr GMA‐MWCNTs/epoxy composites at 50°C increased from 0.32 GPa to 2.87 GPa (enhanced by 799%) and the increased tanδ from 50.5°C to 61.7°C (increased by 11.2°C) comparing with neat epoxy resin, respectively. Furthermore, the thermal conductivity of 3 phr GMA‐MWCNTs/epoxy composite is increased by 183%, from 0.2042 W/mK (neat epoxy) to 0.5781 W/mK. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Enhanced thermal and mechanical properties of epoxy composites by addition of hyperbranched polyglycerol grown on cellulose fibers

We reported a novel approach for epoxy composites by incorporation of hyperbranched polyglycerol (HPG) grafted sisal cellulose fibers (SCF). In this work, we have synthesized SCF wrapped HPG shell (SCF-g-HPG) by a “grafting from” strategy for the strong interfacial interaction between fillers and matrix. It was found that the thermal and mechanical properties of epoxy composites were greatly improved by incorporating SCF-g-HPG. For example, the impact strength, flexural strength, tensile strength, Young’s modulus and toughness of the composites with 3.0 wt% SCF-g-HPG loading were 38.35 KJ/m², 123.40 MPa, 86.62 MPa, 151.7 MPa, and 417.84 MJ/m³, significantly increased by 119.1 %, 55.2 %, 45.6 %, 43.1 %, and 166.1 % respectively, as compared with neat epoxy. In addition, thermal stability of SCF-g-HPG/epoxy composites also showed an obvious enhancement compared with neat epoxy.     

间苯二酚二缩水甘油醚的制备及其应用

采用三苯基磷作醚化催化剂,粉状氢氧化钠作闭环剂合成了间苯二酚二缩水甘油醚(RDGE),其环氧值为0.80,在25℃时粘度为0.36 Pa.s,示差扫描量热仪(DSC)检测表明,其固化放热峰比双酚A型环氧树脂(E51)降低了约15℃。RDGE对E51有非常显著的稀释作用,二者共混,大大提高了通用环氧树脂的综合性能。采用593#固化剂时,RDGE和E51的拉伸强度分别为75.17 MPa和58.58 MPa,前者比后者高出28%,RDGE与E51共混固化物的拉伸强度随RDGE含量的增加而呈线性增加;593#固化的RDGE/E51共混体系,弯曲强度和弯曲模量均随RDGE用量的增加而呈线性增加,弯曲强度由E51的112.77 MPa增加到RDGE的123.75 MPa,弯曲模量由E51的1.79 GPa增加到RDGE的2.40 GPa。     

Preparation and properties of an oxide fiber‐reinforced silica matrix composite

Oxide (Nextel? 440) fiber‐reinforced silica composites, with the density and porosity of 1.97 g/cm³ and 21.8%, were prepared through sol‐gel. Their average flexure strength, elastic modulus, shear strength, and fracture toughness at room temperature were 119.7 MPa, 25.6 GPa, 10.8 MPa, and 4.0 MPa·m^1/2, respectively. The composites showed typical toughened fracture behavior, and distinct pullout fibers were observed at the fracture surface. Their mechanical properties were performant up to 1000°C, with the maximum flexural strength of 132.2 MPa at 900°C. Moreover, the composites showed good thermal stability, even after thermal aging and thermal shock at elevated temperatures.     

Hydrothermal effects on the thermomechanical properties of high performance epoxy/clay nanocomposites

The effects of hydrothermal ageing on the thermomechanical properties of high performance epoxy and its nanocomposite were studied. The epoxy–clay nanocomposite was prepared through a recently developed “slurry‐compounding” approach. The cured samples were immersed in distilled water at 60°C for different periods of time before subjecting to characterization. The storage modulus, relaxation behavior, fracture toughness, and tensile properties were investigated. It was found that the storage modulus and α‐relaxation were strongly affected by water uptake, while the fracture toughness and Young's modulus were less influenced. Dependence of tensile strength and strain at break on water uptake was found to be different in neat epoxy and epoxy–clay systems. POLYM. ENG. SCI., 46:215–221, 2006. © 2005 Society of Plastics Engineers     

Hybrid multi‐scale epoxy composites containing conventional glass microfibers and electrospun glass nanofibers with improved mechanical properties

A mechanically flexible mat consisting of structurally amorphous SiO₂ (glass) nanofibers was first prepared by electrospinning followed by pyrolysis under optimized conditions and procedures. Thereafter, two types of hybrid multi‐scale epoxy composites were fabricated via the technique of vacuum assisted resin transfer molding. For the first type of composites, six layers of conventional glass microfiber (GF) fabrics were infused with the epoxy resin containing shortened electrospun glass nanofibers (S‐EGNFs). For the second type of composites, five layers of electrospun glass nanofiber mats (EGNF‐mats) were sandwiched between six layers of conventional GF fabrics followed by the infusion of neat epoxy resin. For comparison, the (conventional) epoxy composites with six layers of GF fabrics alone were also fabricated as the control sample. Incorporation of EGNFs (i.e., S‐EGNFs and EGNF‐mats) into GF/epoxy composites led to significant improvements in mechanical properties, while the EGNF‐mats outperformed S‐EGNFs in the reinforcement of resin‐rich interlaminar regions. The composites reinforced with EGNF‐mats exhibited the highest mechanical properties overall; specifically, the impact absorption energy, interlaminar shear strength, flexural strength, flexural modulus, and work of fracture were (1097.3 ± 48.5) J/m, (42.2 ± 1.4) MPa, (387.1 ± 9.9) MPa, (12.9 ± 1.3) GPa, and (30.6 ± 1.8) kJ/m², corresponding to increases of 34.6%, 104.8%, 65.4%, 33.0%, and 56.1% compared to the control sample. This study suggests that EGNFs (particularly flexible EGNF‐mats) would be an innovative type of nanoscale reinforcement for the development of high‐performance structural composites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42731.     

Investigation of thermal behaviour and mechanical property of the functionalised graphene oxide/epoxy resin nanocomposites

ABSTRACT

Graphite oxide (GO) and functionalised graphite oxide (FGO) were successfully prepared with -NH₂-terminated GO in the paper, and their chemical structures were characterised with Fourier transform infrared (FTIR), Energy-Dispersive X-ray Spectroscopy (EDS), UV spectrum analysis and XRD, their microstructures were researched by a scanning electron microscope (SEM) and a transmission electron microscope (TEM), and their thermal properties were characterised by TG. The result showed the carbon residue of FGO was 82.1% and the residual char of GO was 48%, the composite materials were prepared with curing for epoxy resin. The thermal stability, mechanical properties, and morphology after impacting tests of composite materials were investigated using thermogravimetric analysis, tensile and charpy impact tests and SEM. The result showed when the 0.2% FGO was filled into the epoxy, the tensile strength was 55.4?MPa, the impact strength was 17.3?KJ/m², the flexural strength was 82?MPa, and the flexural modulus was 2760?MPa. The mechanical properties of composite materials were higher than those of pure epoxy and improved the strength and toughness of epoxy nanocomposites.     

Preparation and properties of bio‐based epoxy montomorillonite nanocomposites derived from polyglycerol polyglycidyl ether and ε‐polylysine

Glycerol polyglycidyl ether (GPE) and polyglycerol polyglycidyl ether (PGPE) were cured with ε‐poly(L ‐lysine) (PL) using epoxy/amine ratios of 1 : 1 and 2 : 1 to create bio‐based epoxy cross‐linked resins. When PGPE was used as an epoxy resin and the epoxy/amine ratio was 1 : 1, the cured neat resin showed the greatest glass transition temperature (T_g), as measured by differential scanning calorimetry. Next, the mixture of PGPE, PL, and montomorillonite (MMT) at an epoxy/amine ratio of 1 : 1 in water was dried and cured finally at 110°C to create PGPE‐PL/MMT composites. The X‐ray diffraction and transmission electron microscopy measurements revealed that the composites with MMT content 7–15 wt % were exfoliated nanocomposites and the composite with MMT content 20 wt % was an intercalated nanocomposite. The T_g and storage modulus at 50–100°C for the PGPE‐PL/MMT composites measured by DMA increased with increasing MMT content until 15 wt % and decreased at 20 wt %. The tensile strength and modulus of the PGPE‐PL/MMT composites (MMT content 15 wt %: 42 and 5300 MPa) were much greater than those of the cured PGPE‐PL resin (4 and 6 MPa). Aerobic biodegradability of the PGPE‐PL in an aqueous medium was ～ 4% after 90 days, and the PGPE‐PL/MMT nanocomposites with MMT content 7–15 wt % showed lower biodegradability. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Adhesion Improvement of Bio-Based Epoxy in Environmentally Friendly and High-Performance Natural Fiber-Reinforced Composites

Developing robust bio-based epoxy against petroleum-derived epoxy is necessary for environmentally friendly and high-performance natural fiber-reinforced composites. A bio-based vanillin epoxy (VE) is synthesized from the lignin-derived vanillin, and a thermoset resin is prepared after mixing it with a 4,4′-diaminodiphenyl methane (DDM) hardener. Further, it is infused in high-cellulose-containing alkali-treated jute fiber (TJF) mats through a simple approach to enhance the adhesion between the VE-DDM and TJF. Bio-based VE-DDM resin shows better compatibility with TJF than petroleum-derived bisphenol A diglycidyl ether (DGEBA) epoxy. The bio-based VE-DDM/TJF composite demonstrates the T_gis ≈165 °C, tensile strength is ≈83.12 ± 3.80 MPa, and Young's modulus is ≈2.86 ± 0.10 GPa with excellent flexural strength (138.72 ± 3.81 MPa) and flexural modulus (8.01 ± 0.11 GPa). It also shows merits regarding hydrophobicity, reduced water absorption ability, durability, and chemical resistance in an acidic medium. The natural fiber-reinforced VE composites pave the way to produce environmentally friendly and high-performance composites for structural applications.     

RTM成型用高性能环氧树脂基体的研究

将AG-80和TDE-86以一定比例混合,通过加入自配的低粘度液体固化剂,得到了一种适用于RTM工艺的树脂体系。结果表明,该树脂体系在30℃时的粘度为1081mPa.s,其树脂固化物的拉伸强度为73MPa,弹性模量达到1.36GPa,断裂伸长率为6.3%,弯曲强度为150MPa,弯曲模量为3.12GPa,玻璃化转变温度为191℃,该树脂体系不仅粘度低,还具有优异的力学性能和耐温性,可满足RTM成型工艺对环氧树脂体系的要求。     

An epoxy resin-elastomer system for filament winding

Tests characterizing an epoxy system that contains 5 percent rubber and is suitable for wet-filament winding are described. The resin is a bisphenol-A rubberized epoxy diluted with an aliphatic diglycidyl ether and cured with an aromatic amine. The viscosity and pot life were measured and the progress of cure was monitored so an optimum cure could be chosen. Mechanical tests were performed on the cured resin. The low viscosity (0.95 Pa's) and long pot life (29.3 h) make for ease of processing. A cure cycle of 1.5h at 90°C plus 2 h at 130°C gives a cured resin having a glass transition temperature of 104°C. The heat-cured material has a tensile strength of 76.1 MPa and a modulus of 2.43 GPa. Kevlar 49 composites of 60-, 65-, and 70-volume-percent fiber were prepared and tested. Results are presented and compared to two other Kevlar 49/epoxy composites.     

Microstructural,mechanical, and thermal characteristics of recycled cellulose fiber‐halloysite‐epoxy hybrid nanocomposites

Epoxy hybrid‐nanocomposites reinforced with recycled cellulose fibers (RCF) and halloysite nanotubes (HNTs) have been fabricated and investigated. The dispersion of HNTs was studied by synchrotron radiation diffraction (SRD) and transmission electron microscopy (TEM). The influences of RCF/HNTs dispersion on the mechanical properties and thermal properties of these composites have been characterized in terms of flexural strength, flexural modulus, fracture toughness, impact toughness, impact strength, and thermogravimetric analysis. The fracture surface morphology and toughness mechanisms were investigated by SEM. Results indicated that mechanical properties increased because of the addition of HNTs into the epoxy matrix. Flexural strength, flexural modulus, fracture toughness, and impact toughness increased by 20.8, 72.8, 56.5, and 25.0%, respectively, at 1 wt% HNTs load. The presence of RCF dramatically enhanced flexural strength, fracture toughness, impact strength, and impact toughness of the composites by 160%, 350%, 444%, and 263%, respectively. However, adding HNTs to RCF/epoxy showed only slight enhancements in flexural strength and fracture toughness. The inclusion of 5 wt% HNTs into RCF/epoxy ecocomposites increased the impact toughness by 27.6%. The presence of either HNTs or RCF accelerated the thermal degradation of neat epoxy. However, at high temperature, samples reinforced with RCF and HNTs displayed better thermal stability with increased char residue than neat resin. POLYM. COMPOS. 2012. © 2012 Society of Plastics Engineers