邻甲硼酚醛树脂固化双酚-A环氧树脂及其复合材料的性能

用邻甲硼酚醛树脂(BoPFR)固化双酚-A环氧树脂(BPAER),制备了含硼酚醛的高性能玻璃钢复合材料.分析了固化过程,研究了固化树脂以及玻璃纤维层压板的力学性能、热性能和电性能.当m(BoPFR)/m(BPAER)为1.0∶0.5时,复合材料的玻璃化转变温度从198.4 ℃下降到134.5℃,材料韧性提高.固化物有良好的耐热性能,当m(BoPFR)/m(BPAER)为1.0∶0.2时,材料在900℃时的残留率为25.83％,热降解动力学符合一级反应动力学;玻璃纤维层压板拉伸强度提高了一倍,而电性能变化不大.     

Addition‐cure phenolic resins based on propargyl ether functional novolacs: synthesis,curing and properties

Thermosetting phenolic resins, bearing varying extents of propargyl ether groups (PN resins), have been synthesized by the Williamson reaction of a novolac with propargyl bromide and the products characterized. The resin precursors were cured through Claisen rearrangement of the propargyl ether groups and thermal polymerization. The activation energy for thermal cure is substantially lower than that of model bispropargyl ether compounds but is quite independent of the degree of functionalization. The isothermal cure profile, extrapolated from non‐isothermal DSC kinetics studies is consistent with the results from DMA studies. The mechanical properties of glass composites of the resins, of varying propargyl contents, reveal good consolidation of the interphases, evident from the initial gain in both interlaminar shear strength (ILSS) and flexural strength. The benefits of better resin–reinforcement interactions are not retained on crosslinking the resin further, wherein the composite fails by a combination of fibre debonding and brittle fracture of the matrix. Although the resins show better thermal stability than cured resoles, a higher extent of propargylation is detrimental for the thermal stability. Resins with moderate propargylation show good mechanical and thermal properties. © 2001 Society of Chemical Industry     

Monitoring the reaction progress of a high‐performance phenylethynyl‐terminated poly(etherlmide). Part II: Advancement of glass transition temperature

The cure schedule for carbon fiber‐reinforced, phenylethynyl‐terminated Ultem™ (GE Plastics) composites was studied in an attempt to optimize the resultant glass transition temperature, T_g. Reaction progress and possible matrix degradation were monitored via the T_g. On the basis of previous research, matrix degradation induced T_g reduction was expected for increases in cure time or temperature beyond approximately 70 minutes at 350°C. Using the central composite design (CCD) of experiment technique, composite panels, neat resin, and polymer powder‐coated tow (towpreg) were cured following various cure schedules to allow for the measurement of the glass transition temperatures resulting fronm cure time and temperature variations. The towpreg and neat resin specimens were cured in a differential scanning calorimeter. The glass transition temperatures of all specimens were measured via differential scanning calorimetry; the composite glass transition temperatures were also measured with dynamic mechanical thermal analysis. The composite panels and towpreg specimens showed similar trends in T_g response to cure schedule variations. Composite and towpreg glass transition temperatures increased to a plateau with increasing cure time and temperature, whereas, the neat resin showed an optimal T_g followed by T_g reduction with increasing cure time and temperature. The optimal neat resin T_g occurred within a cure time and temperature significantly below that required to maximize the composite and towpreg glass transition temperatures.     

环氧树脂改性氰酸酯树脂的研究进展

综述了采用环氧树脂(EP)增韧改性氰酸酯(CE)树脂的共聚反应机理、固化产物的性能和复合材料的性能。CE在水分或残留的酚及金属离子等作用下自聚生成三嗪环,接着与EP反应生成口恶唑烷酮。CE改性后树脂的韧性和弯曲强度提高,而玻璃化温度和耐热性下降很少,且固化产物耐湿热性能和介电性能基本维持不变。     

Sepiolite‐reinforced epoxy nanocomposites: Thermal,mechanical, and morphological behavior

A bisphenol A‐based epoxy resin was modified with pristine sepiolite and an organically surface‐modified sepiolite and thermally cured using two different curing agents: an aliphatic and a cycloaromatic diamine. The nanocomposites were characterized by dynamic mechanical analysis (DMA), rheology, thermogravimetric analysis (TGA), and electron microscopy. The initial sepiolite–epoxy mixtures show a better dispersion for the sepiolite‐modified system that forms a percolation network structure. Mechanical properties have also been determined. The flexural modulus of the epoxy matrix slightly increases by the incorporation of the organophilic sepiolite. The flexural strength of the sepiolite‐modified resin cured with the aliphatic diamine increased by 10%, while the sepiolite‐modified resin cured with the cycloaromatic diamine resulted in a lower flexural strength, as compared with the unmodified resin. Electron micrographs revealed a better nanodispersion of the sepiolite in the epoxy matrix for the organophilic modified sepiolite nanocomposite. The initial thermal decomposition temperature did not change significantly with the addition of sepiolite, whereas mechanical properties were affected. The reduced flexural strength was attributed to the stress concentrations caused by the sepiolite modifier. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

New tetrafunctional epoxy resin system with increased shelf life

Chlorine‐ and methyl‐substituted aromatic diamines based on diaminodiphenylmethane were epoxidized and characterized. The effect of different substituents on epoxidation was studied. The cure studies of the two new tetrafunctional resins in comparison with unsubstituted resin N,N,N′,N′‐tetraglycidyl‐4,4′‐diaminodiphenylmethane (TGDDM) was carried out by DSC with 3,3′‐dichloro‐4,4′diaminodiphenylmethane (o‐DCDDM; 30% w/w) as a common curing agent. The mechanical properties such as flexural, Izod impact, heat distortion temperature (HDT), of such cured neat resins were also studied. The results of the cure studies indicate that the substitution of the α‐hydrogen of the resin by chlorine or methyl group decreases the reactivity of the resin leading to an increase in the shelf life. This study also indicates that the functionality of the resin plays a pivotal role in the reactivity and thus the shelf life of an epoxy resin system. The results of the mechanical properties of the neat resin casts obtained by subjecting to a common cure schedule when compared with the unsubstituted resin showed a decrease in impact strength, which is obvious because of the presence of a bulky pendant group but the impact strength was higher than that of the TGOS30 resin system. Results of flexural strength of the different substituted neat resin casts did not show much of a deviation from that of the unsubstituted resin system. The HDT results indicate no significant difference in the values of the unsubstituted resin vis‐a‐vis with substituted resin systems. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2790–2801, 2004     

动态固化聚丙烯／马来酸酐接枝聚丙烯／滑石粉／环氧树脂复合材料研究

将动态硫化技术应用于热塑性树脂／填料／热固性树脂复合体系，制备了动态固化聚丙烯(PP)／马来酸酐接枝PP(PP-g-MAH)/滑石粉(Talc)／环氧树脂(EP)复合材料。研究了动态固化PP／PP-g-MAH/Talc／EP复合材料的界面作用、形态结构、力学性能以及热稳定性。实验结果表明：PP／PP-g—MAH的加入，可明显增加PP/Talc复合材料的界面作用。在动态固化PP／PP-g-MAH/Talc／EP复合材料中，PP和Talc两相界面更加模糊，动态固化EP进一步增加了PP和Talc间的界面作用。当EP的用量超过5份时，部分EP呈颗粒状分布在PP基体中。与PP／PP-g-MAH/Talc／EP和PP／PP-MAH-Talc／EP复合材料相比，动态固化PP／PP-g-MAH/Talc／EP复合材料的冲击强度、拉伸强度和弯曲模量均有明显提高。当EP用量超过5份时，复合材料的冲击强度和断裂伸长率明显降低，但拉伸强度和弯曲模量继续增加。热分析表明动态固化PP／PP-g-MAH/Talc／EP复合材料具有较高的热稳定性。     

Synthesis and characterization of chlorinated soy oil based epoxy resin/glass fiber composites

Composites with good toughness properties were prepared from chemically modified soy epoxy resin and glass fiber without additional petroleum based toughening agent. Chlorinated soy epoxy (CSE) resin was prepared from soybean oil. The CSE was characterised by spectral, and titration method. The prepared CSE was blended with commercial epoxy resin in different ratios and cured at 85°C for 3 h, and post cured at 225°C for 2 h using m‐phenylene diamine (MPDA) as curing agent. The cure temperatures of epoxy/CSE/MPDA with different compositions were found to be in the range of (151.2–187.5°C). The composite laminates were fabricated using epoxy /CSE/MPDA‐glass fiber at different compositions. The mechanical properties such as tensile strength (248–299 MPa), tensile modulus (2.4–3.4 GPa), flexural strength (346–379 MPa), flexural modulus (6.3–7.8 GPa) and impact strength (29.7–34.2) were determined. The impact strength increased with the increase in the CSE content. The interlaminor fracture toughness (G_IC) values also increased from 0.6953 KJ/m² for neat epoxy resin to 0.9514 KJ/m² for 15%CSE epoxy‐modified system. Thermogravimetric studies reveal that the thermal stability of the neat epoxy resin was decreased by incorporation of CSE. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

High-performance composite from epoxy and glass fibers: Morphology,mechanical, dynamic mechanical,and thermal analysis

Diglycidyl ether of bisphenol-A type epoxy resin cured with diamino diphenyl sulfone was used as the matrix for fiber-reinforced composites to get improved mechanical and thermal properties for the resulting composites. E-glass fiber was used for fiber reinforcement. The morphology, tensile, flexural, impact, dynamic mechanical, and thermal properties of the composites were analyzed. The tensile, flexural, and impact properties showed dramatic improvement with the addition of glass fibers. Dynamic mechanical analysis was performed to obtain the T_g of the cured matrix as well as the composites. The improved thermal stability of the composites was clear from the thermogravimetric analysis. Scanning electron micrographs were taken to understand the interfacial adhesion between the fiber and the matrix. The values of mechanical properties were compared with modified epoxy resin composite system. Predictive models were applied using various equations to compare the mechanical data obtained theoretically and experimentally. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Effect of cyanate ester on the cure behavior and thermal stability of epoxy resin

Epoxy resin (diglycidyl ether of bisphenol A, DGEBA)/cyanate ester mixtures were cured with a curing agent, 4,4′-diaminodiphenylsulfone, and the effect of cyanate ester resin on the cure behavior and thermal stability in the epoxy resin was investigated with a Fourier transform infrared spectrometer, a rheometer, a dynamic mechanical analyzer, and a thermogravimetric analyzer. Cure reactions in the epoxy/cyanate ester mixture were faster than that of the neat epoxy system. The cure reaction was accelerated by increasing the cyanate ester resin component. Glass transition temperature and thermal stability in the cured resins were increased with increasing cyanate ester resin component. This may be caused by the increase of crosslinking density due to the polycyclotrimerization of the cyanate ester monomer to form triazine rings and the reaction of cyanate ester resin with the epoxy network. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 85–90, 1997     

Epoxy toughening using low viscosity liquid diglycidyl ether of ethoxylated bisphenol‐A

Two new epoxy resins, diglycidyl ether of ethoxylated bisphenol‐A (BPA) with two and six oxyethylene units (DGEBAEO‐2 and DGEBAEO‐6) were synthesized and characterized. DGEBAEO‐6 was used to toughen the conventional epoxy resin diglycidyl ether of BPA (DGEBA). The blends of DGEBA with different amounts of DGEBAEO‐6 were cured by 4,4′‐diamino diphenylmethane (DDM), and their thermal and mechanical properties were examined. The DSC and DMA results presented that DGEBA/DGEBAEO‐6 blends exhibited a homogenous phase, and the glass transition temperature of the blends was inversely proportional to the content of DGEBAEO‐6. The impact strength of the cured blends was directly proportional to the content of DGEBAEO‐6, and reached five times higher than that of the neat DGEBA when 50 wt % DGEBAEO‐6 was used; the same impact strength was achieved for DDM‐cured DGEBAEO‐2. The viscosities of the blends decreased with increasing the DGEBAEO‐6 content, whereas the tensile and flexural strength and the thermal stabilities were not obviously affected. Scanning electron microscopic results confirmed that the plastic deformation inducing by the incorporated flexible oxyethylene units was responsible for the toughness improvement. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis of polysiloxane‐type multifunctional flame retardant and its application in epoxy systems

Polymethyl(3‐glycidyloxypropyl)siloxane (PMGS) was synthesized as a flame‐retardant additive, which were cocured with diglycidyl ether of bisphenol‐A (DGEBA) using 4,4′‐diaminodiphenylsulfone as a curing agent. The structure of PMGS was confirmed through Fourier transform infrared and ¹H‐NMR spectra. The cured products were characterized with dynamic mechanical thermal analysis, thermogravimetric analysis, and oxygen index analyzer. With PMGS incorporated, the cured epoxy resin showed better thermal stability, higher limited oxygen index, and higher char yield. At moderate loading of PMGS, the storage modulus and glass transition temperature of the cured epoxy resin based on neat DGEBA were obviously improved. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Addition‐cure‐type phenolic resin based on alder‐ene reaction: Synthesis and laminate composite properties

A maleimide‐functional phenolic resin was reactively blended with an allyl‐functional novolac in varying proportions. The two polymers were coreacted by an addition mechanism through Alder‐ene and Wagner–Jauregg reactions to form a crosslinked network system. The cure characterization was done by differential scanning calorimetry and dynamic mechanical analysis. The system underwent a multistep curing process over a temperature range of 110–270°C. Although the cure profiles were independent of the composition, the presence of maleimide led to a reduced isothermal gel time of the blend. Increasing the allylphenol content decreased the crosslinking in the cured matrix, leading to enhanced toughness and improved resin‐dominant mechanical properties of the resultant silica laminate composites. Changing the reinforcement from silica to glass resulted in further amelioration of the resin‐reinforcement interaction, but the resin‐dominant properties of the composite remained unaltered. Increasing the maleimide content resulted in enhanced thermal stability. Integrating both the reactive groups in a single polymer and its curing led to enhanced thermal stability and T_g, but to decreased mechanical properties of the laminate composites. This can be attributed to a brittle matrix resulting from enhanced crosslinking facilitated by interaction of the reactive groups located on the polymer of an identical backbone structure. The cured polymers showed a T_g in the range of 170–190°C. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 737–749, 2001     

Polydimethylsiloxane containing isocyanate group-modified epoxy resin: Curing,characterization, and properties

A synthesized polydimethylsiloxane containing an isocyanate group was used to improve the flexibility and to reduce the internal stress of epoxy resin cured with MDA (4,4′-methylene dianiline). The effect of polysiloxane content on the curing kinetics of a novolac-type epoxy modified with an isocyanate group was investigated. It was found that the modified epoxy resin showed significant improvement in impact strength. The polysiloxane containing isocyanate groups effectively depressed the internal stress of cured epoxy resins by reducing the flexural modulus and the coefficient of thermal expansion, while the glass transition temperature was increased. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2739–2747, 1999     

Effects of carbon nanotube fillers on the curing processes of epoxy resin‐based composites

The effects of different grades of carbon nanotubes on the curing of a typical epoxy resin (EPIKOTE? resin 862 and EPIKURE? curing agent W) were examined via differential scanning calorimetry. It was found that nanotubes could initiate cure at lower temperatures, while the overall curing process was slowed as evidenced by lower total heat of reaction and lower glass transition temperatures of the cured nanocomposites compared to neat epoxy. This finding is practically important as it is essential to have a consistent degree of cure when the properties of thermosets with nanoinclusions are compared to neat resins. It was also found that the inclusion of carbon nanotubes might induce the thermal degradation of epoxy composites at lower temperatures. Morphological analysis done with scanning electron microscopy revealed good dispersion of nanotubes within the epoxy matrix. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:5248–5254, 2006     

Preparation,morphology, and properties of silane‐modified MWCNT/epoxy composites

Both epoxy resin and acid‐modified multiwall carbon nanotube (MWCNT) were treated with 3‐isocyanatopropyltriethoxysilane (IPTES). Scanning electron microscopy (SEM) and transmission electronic microscope (TEM) images of the MWCNT/epoxy composites have been investigated. Tensile strength of cured silane‐modified MWCNT (1.0 wt %)/epoxy composites increased 41% comparing to the neat epoxy. Young's modulus of cured silane‐modified MWCNT (0.8 wt %)/epoxy composites increased 52%. Flexural strength of cured silane‐modified MWCNT (1.0 wt %)/epoxy composites increased 145% comparing to neat epoxy. Flexural modulus of cured silane‐modified MWCNT (0.8 wt %)/epoxy composites increased 31%. Surface and volume electrical resistance of MWCNT/epoxy composites were decreased with IPTES‐MWCNT content by 2 orders and 6 orders of magnitude, respectively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Properties and curing behavior of reactive blended allyl novolak with bismaleimide using dicumyl peroxide as a novel curing agent

For reducing the cure temperature and improving the thermal stability and mechanical properties, a thermosetting resin system composed of novolak and bismaleimide (BMI) was developed by reactive blending and using dicumyl peroxide (DCP) as a novel curing agent. Novolak was allylated and reacted with BMI to produce bismaleimide allylated novolak (BAN), and the effect of DCP on flexural, impact and heat distortion temperature of cured resin were investigated. On the basis of improved mechanical and thermal properties at 0.5% DCP contents, the curing behavior of DCP/BAN resin system was evaluated by DSC analysis. Ene, Diels‐Alder, homo‐polymerization and alternating copolymerization which occurred in DCP/BAN resin system were further verified using FTIR at sequential cure conditions from 140 to 200°C. Kissinger and Ozawa‐Flynn‐wall methods were used to optimize the process and curing reactions of DCP/BAN resin system. The results showed that the addition of 0.5% DCP in BAN reduced the curing temperature and time of the modified resin. For evaluating process ability of the modified system, composite samples using polyvinyl acetyl fiber were molded and tested for flexural properties. The resulting samples showed better flexural properties when compared with the composite made with neat BAN. The modified 0.5% DCP/BAN resin system with good mechanical properties and manufacturability can be used for making bulk molding compounds and fiber reinforced composites required in various commercial and aerospace applications. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41829.     

Effect of structure on mechanical properties of vinyl ester resins and their glass fiber‐reinforced composites

The article describes the effect of structure of vinyl ester resins (VE) on the mechanical properties of neat sheets as well as glass fabric‐reinforced composites. Different samples of VE were prepared by reacting ester of hexahydrophthalic anhydride (ER) and methacrylic acid (MAA) (1 : 1 molar ratio) followed by reaction of monomethacrylate terminated epoxy resin with glutaric (E) or adipic (F) or sebacic acid (G) (2 : 1 molar ratio). The neat VE were diluted with styrene and sheets were fabricated by using a glass mold. A significant reduction in the mechanical properties was observed by increasing the methylene content of resin backbone (i.e., sample E to G). Glass fabric‐reinforced composites were fabricated by vacuum assisted resin transfer molding (VARTM) technique. Resin content in the laminates was 50 ± 5 wt %. Increase in the number of methylene groups in the vinyl ester resin (i.e., increasing the bridge length) did not show any significant effect on limiting oxygen index (LOI) value (21 ± 1) of the laminates but tensile strength, tensile modulus, flexural strength, and flexural modulus all increased though these values are significantly lower than observed in laminates based on resin B. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis,cure analysis,and composite properties of allylated cyclopentadiene resins

Allylated cyclopentadiene was synthesized through the phase transfer reaction of cyclopentadiene and allyl chloride in the presence of a strong base. The reaction yielded a mixture of isomers with 2 to 6 allyl groups per cyclopentadiene ring. Variations in reactant ratios changed product ratios only slightly; however, lower ratios of allyl chloride to cyclopentadiene (4:1 and 2:1) produced lower substituted products. DSC analysis of the ACP showed thermal cure without added catalyst. The total enthalpy of cure was ∼750 J/g with a peak energy at 310°C. FTIR analysis of the thermal cure showed the predominate cure mechanisms to be ene reactions and polyadditions of allyl groups with a small amount of oxidation. Partial curing (B-staging) of ACP was conducted thermally at 180 and 200°C. An increase in viscosity with time was found in each case with gelation occurring at ∼15 h and 3 h, respectively. ACP resin was also cured using various concentrations of peroxide and BF₃₀ dibutyl etherate catalysts. In all cases gelled materials were formed. ACP/carbon fiber and ACP/glass fiber composites gave flexural moduli of 165 and 42 GPa, respectively. Flexural strength values were found to be 956 MPa for ACP/carbon and 681 MPa for ACP/glass. Treatment of ACP/carbon fiber composites in boiling water or refluxing toluene had no significant effect on their mechanical properties.     

Toughening epoxy resin with blocked isocyanate containing soft chain

A series of imidazole (MI) blocked 2,4‐toluene diisocyanate (TDI) with polyethylene glycol (PEG‐400) as soft segment (PEG‐MI‐b‐TDI) were synthesized for toughening and curing the bisphenol A type epoxy resin (E‐44). Fourier transform infrared (FTIR) spectrum indicates that the NCO groups of the isocyanate molecule are blocked with MI. For curing epoxy systems, elimination of epoxy group and the formation of urethane bonds were studied by FTIR spectroscopy. The results of mechanical property were shown that the tensile shear and impact strengths of neat MI and MI‐b‐TDI cured E‐44 are lower than those of PEG‐MI‐b‐TDI cured E‐44. Based on the scanning electron microscope studies, microstructure evolutions of the E‐44 cured by different curing agents were imaged. The mechanical, thermal, and dynamic mechanical properties were measured by universal testing machine, differential scanning calorimeter and dynamic mechanical analyzer (DMA). The toughness of E‐44 cured by PEG‐MI‐b‐TDI was effectively improved without sacrificing the tensile shear strength. Based on the DMA studies, the long soft chain of PEG brought in a noticeable lowering in the glass transition temperature (T_g). The glass transition temperature is near 165°C for the neat MI cured E‐44, which is higher than the T_gs of the other curing agents cured epoxy. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41345.