Epoxy curing by polyaniline (PANI) – Characterization and self-healing evaluation

Polyaniline (PANI) was synthesized by chemical oxidative polymerization of aniline dissolved in aqueous phosphoric acid. The polymer was characterized by UV–Visible spectroscopy (UV–Vis), thermal gravimetric analysis (TGA) and Fourier transform infrared spectroscopic (FTIR) techniques. Hardener free epoxy coating was formulated with 10% PANI. The curing process of epoxy resin by PANI was analyzed using FTIR and a suitable mechanism of curing was suggested. The corrosion protective performance of conventional polyamide cured epoxy and PANI cured epoxy coating on steel has been assessed in 3% NaCl by electrochemical impedance spectroscopy (EIS). The self-healing property of the PANI cured epoxy coating on steel in 3% NaCl was studied by scanning vibrating electrode technique (SVET).     

环氧树脂/蒙脱土纳米复合材料的性能及增韧机理

将有机蒙脱土添加到环氧树脂中,制备环氧树脂/纳米复合材料,考察复合材料的力学和热学性能,研究发现,5%的添加量可以使环氧树脂的冲击、断裂强度得到大幅度的提高,添加3%的有机蒙脱土,热变形温度提高了6.1℃.通过SEM和AFM,对环氧树脂/蒙脱土纳米复合材料冲击断口进行微观研究,发现断口呈现出明显的韧性断裂.结合微观形貌,对有机蒙脱土增韧环氧树脂的各种机理进行探讨,认为符合基体剪切屈服增韧机理.     

Thermo mechanical behaviour of unsaturated polyester toughened epoxy–clay hybrid nanocomposites

The intercrosslinked networks of unsaturated polyester (UP) toughened epoxy–clay hybrid nanocomposites have been developed. Epoxy resin (DGEBA) was toughened with 5, 10 and 15% (by wt) of unsaturated polyester using benzoyl peroxide as radical initiator and 4,4′-diaminodiphenylmethane as a curing agent at appropriate conditions. The chemical reaction of unsaturated polyester with the epoxy resin was carried out thermally in presence of benzoyl peroxide-radical initiator and the resulting product was analyzed by FT-IR spectra. Epoxy and unsaturated polyester toughened epoxy systems were further modified with 1, 3 and 5% (by wt) of organophilic montmorillonite (MMT) clay. Clay filled hybrid UP-epoxy matrices, developed in the form of castings were characterized for their thermal and mechanical properties. Thermal behaviour of the matrices was characterized by differential scanning calorimetry (DSC), thermo gravimetric analysis (TGA) and dynamic mechanical analysis (DMA). Mechanical properties were studied as per ASTM standards. Data resulted from mechanical and thermal studies indicated that the introduction of unsaturated polyester into epoxy resin improved the thermal stability and impact strength to an appreciable extent. The impact strength of 3% clay filled epoxy system was increased by 19.2% compared to that of unmodified epoxy resin system. However, the introduction of both UP and organophilic MMT clay into epoxy resin enhanced the values of mechanical properties and thermal stability according to their percentage content. The impact strength of 3% clay filled 10% UP toughened epoxy system was increased by 26.3% compared to that of unmodified epoxy system. The intercalated nanocomposites exhibited higher dynamic modulus (from 3,072 to 3,820 MPa) than unmodified epoxy resin. From the X-ray diffraction (XRD) analysis, it was observed that the presence of d ₀₀₁ reflections of the organophilic MMT clay in the cured product indicated the development of intercalated clay structure which in turn confirmed the formation of intercalated nanocomposites. The homogeneous morphologies of the UP toughened epoxy and UP toughened epoxy–clay hybrid systems were ascertained from scanning electron microscope (SEM).     

Influence of Multiwalled Carbon Nanotubes on Mechanical,Thermal and Electrical Behavior of Polybenzoxazine-Epoxy Nanocomposites

Multiwalled carbon nanotubes (MWCNT)-reinforced polybenzoxazine-epoxy nanocomposites were prepared via the solvent method and were investigated for their thermal, thermo-mechanical, mechanical, electrical and morphological properties. Epoxy resin (DGEBA) was modified with 5, 10 and 15 wt.% of benzoxazines using 4,4′-diaminodiphenylmethane as a curing agent at appropriate conditions. Epoxy and benzoxazines-modified epoxy systems were further reinforced with 0.25, 0.50 and 0.75 wt.% of surface-modified MWCNT. MWCNT-reinforced polybenzoxazine-epoxy nanocomposites exhibited better thermal, mechanical and dielectric properties. Dispersion of MWCNT in benzoxazine-epoxy resins and nanostructure of the composites was confirmed by transmission electron microscopy analysis.     

Sodium carbonate activated slag as cement replacement in autoclaved aerated concrete

This paper aims to study the suitability of fully replacing cement by sodium carbonate activated slag in producing autoclaved aerated concrete (AAC). The material properties of the product are characterized in terms of green strength development, mechanical properties, pore related properties such as porosity and thermal conductivity, shrinkage and reaction products. The produced alkali-activated slag-based AAC (ASAAC) shows comparable material properties to the designed cement-based reference AAC samples by giving a compressive strength of −25% with raw density of +18%, thermal conductivity of +13% with a porosity of −5% and drying shrinkage of +5.5%. Besides, a relatively higher crystallinity of calcium silicate hydrates and Al incorporation in the chain of C-S-H is observed for ASAAC products. Furthermore, significant reductions in cost, energy consumption and CO₂ emission are foreseen.     

Preparation and characterization of bismaleimide (N,N′‐bismaleimido‐4,4′‐diphenyl methane)–unsaturated polyester modified epoxy intercrosslinked matrices

An intercrosslinked network of unsaturated polyester–bismaleimide modified epoxy matrix systems was developed. Epoxy systems modified with 10, 20, and 30% (by weight) of unsaturated polyester were made by using epoxy resin and unsaturated polyester with benzoyl peroxide and diaminodiphenylmethane as curing agents. The reaction between unsaturated polyester and epoxy resin was confirmed by IR spectral studies. The unsaturated polyester toughened epoxy systems were further modified with 5, 10, and 15% (by weightt) of bismaleimide (BMI). The matrices, in the form of castings, were characterized for their mechanical properties. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) of the matrix samples were performed to determine the glass transition temperature (T_g) and thermal degradation temperature of the systems, respectively. Mechanical properties, viz: tensile strength, flexural strength, and plain strain fracture toughness of intercrosslinked epoxy systems, were studied by ASTM methods. Data obtained from mechanical and thermal studies indicated that the introduction of unsaturated polyester into epoxy resin improves toughness but with a reduction in glass transition, whereas the incorporation of bismaleimide into epoxy resin improved both mechanical strength and thermal behavior of epoxy resin. The introduction of bismaleimide into unsaturated polyester‐modified epoxy resin altered thermomechanical properties according to their percentage concentration. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2853–2861, 2002     

Enhancing the thermal conductivities of SiO2/Epoxy composites by orientation

To improve the thermal conductivity of epoxy resin, tensile way was used to orient the molecular chain of epoxy resin with SiO₂ particles filled. In this article, SiO₂/Epoxy composites which had approximately one‐dimensional lattice structure were prepared. The heat generated by LED chip rapidly passed along the direction of the one‐dimensional orientation in SiO₂/Epoxy composites. The results showed that the thermal conductivity of oriented composites increased with the increase of silica concentration and draw ratio (If S is the cross‐sectional areas of composites at the mold outlet, S₀ is the cross‐sectional areas of composites after molding set, and draw ratio is S/S₀). With the addition of 50 wt% SiO₂ to the epoxy resin, the thermal conductivity of oriented SiO₂/Epoxy composites with the draw ratio of 4 was 0.873 W/m K, which was 2.55 times that of unoriented SiO₂/Epoxy composites. And a thermal conductivity, 5.97 times that of the epoxy resin, was obtained with 80 wt% SiO₂ and the draw ratio of 4. Nevertheless, the relative permittivities of epoxy composites which had 50 wt% SiO₂ with the draw ratio of 4 are stable with increasing frequency. POLYM. COMPOS., 37:818–823, 2016. © 2014 Society of Plastics Engineers     

Laboratory investigation of the properties of asphalt modified with epoxy resin

Epoxy asphalts were prepared by mixing styrene–butadiene–styrene (SBS) modified asphalt with epoxy resin. The curing process and morphology of epoxy asphalts were characterized by infrared spectroscopy and fluorescent microscope, respectively. The effects of epoxy resin contents, ratio of curing agent to epoxy resin and curing temperature on properties of epoxy asphalt were investigated. Results indicated that epoxy resin and epoxy asphalt showed similar curing efficiency. Epoxy asphalts can be cured at 120 or 60°C and its viscosity at 120°C can meet the demands of asphalt mixture mixing and paving. The chemical reaction of epoxy resin in epoxy asphalt is slow and reaction occurs not only with the curing agent but also carboxylic acid in epoxy asphalt. The microstructure of epoxy asphalt transforms from the dispersed structure to networks structure with epoxy resin content increasing and phase transition starts when 30 wt % epoxy resin present in asphalt. The softening point and tensile strength of epoxy asphalt increased with epoxy resin contents increasing. The softening point and tensile strength of epoxy asphalt were markedly improved when epoxy resin content was more than 30 wt %, which is attributed to formation of continuous structure of epoxy resin. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and characterization of high‐performance epoxy resin based on disiloxane and 4,4′‐oxybis(benzoic acid) ester

Epoxy‐terminated siloxane‐contained resin (BCDS/OBBA‐ETS) with high tensile strength and lap shear strength as well as good thermal stability was synthesized and characterized by ¹H‐NMR and Fourier transform infrared spectroscopy. Carboxy‐capped disiloxane‐4,4′‐oxybis (benzoic acid) ester oligomer (BCDS/OBBA) was firstly prepared from the reaction between 1,3‐bis(chloromethyl)‐1,1,3,3‐tetramethyl‐disiloxane and 4,4′‐oxybis(benzoic acid) (OBBA) in N,N‐dimethylformamide in the presence of triethylamine. Then, the BCDS/OBBA oligomer was reacted with epichlorohydrin to obtain the title BCDS/OBBA‐ETS resin. Cured with liquid polyamide L‐651, or diethylenetriamine, the mechanical and thermal properties as well as the lap shear strength of the BCDS/OBBA‐ETS resin were evaluated. The results indicated that the BCDS/OBBA‐ETS resin exhibited good thermal stability below 200°C, and the glass transition temperature (T_g) was about 64°C after cured with L‐651. The tensile strength of same cured BCDS/OBBA‐ETS resin was 27.46 MPa with a stain at break of 42.11%, and the lap shear strength for bonding stainless steel was 18.59 MPa. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of sulfur in different valence on flame retardance of epoxy resin for light emitting diode

A novel phosphorus/nitrogen-containing flame retardant (DOPO-AM) was synthesized by 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and acrylamide (AM) and its chemical structure was characterized. DOPO-AM was added into diglycidyl ether of bisphenol-A (DGEBA) with curing agent m-xylylenediamine (MXDA)to prepare flame retarded epoxy resin to reduce the possibility of fire. The compounds with different valences sulfur respectively replace partial DGEBA resin to study the effects of sulfur valences on the flame retardance of epoxy resins. The results indicated that DOPO-AM had excellent flame retardance for epoxy resin. When phosphorus content was only 0.75%, DGEBS resin containing DOPO-AM achieved the limiting oxygen index value of 34.55% and vertical burning test (UL-94) V-0 rating. Although sulfur element is help for refractive index of epoxy resin, sulfur element in three kinds of valences all weaken the flame retardant of epoxy resin. Improving phosphorus content is help for the synergistic effect of P N and P N S. Moreover, the flame retardance is not proportional to sulfur valence, sulfide with +2 valence had the best flame retardance. However, +6 valence sulfonic with strong oxidation effect worsen the flame retardant. Simultaneous thermal analysis of thermogravimetric analyzer and differential scanning calorimeter and scanning electronic microscopy photographs verified the above conclusion.     

硅烷单体改性环氧树脂的固化及性能

分别用苯基三甲氧基硅烷(PTMS)和3-缩水甘油醚氧丙基三甲氧基硅烷(KH560)单体对环氧树脂进行了化学改性,通过红外(FT-IR)、核磁(1H NMR)对其化学结构进行了表征。以聚酰胺650为固化剂,用差示扫描量热仪(DSC)研究了固化物的固化动力学。此外还研究了涂膜的热失质量(TGA)、吸水率、附着力等性能。结果表明:苯基三甲氧基硅烷和3-缩水甘油醚氧丙基三甲氧基硅烷接枝上环氧树脂,与纯环氧树脂相比,改性后的树脂具有更好的热稳定性和更低的吸水率。改性环氧树脂固化后形成两面性质不同的涂层,与底材接触的涂层底面保留了环氧树脂原有的附着力,而涂层表面则具有高憎水性,起到防腐等作用。     

Preparation and characterization of siliconized epoxy/bismaleimide (N,N′‐bismaleimido‐4,4′‐diphenyl methane) intercrosslinked matrices for engineering applications

Novel hybrid intercrosslinked networks of hydroxyl‐terminated polydimethylsiloxane‐modified epoxy and bismaleimide matrix systems have been developed. Epoxy systems modified with 5, 10, and 15 wt % of hydroxyl‐terminated polydimethylsiloxane (HTPDMS) were developed by using epoxy resin and hydroxyl‐terminated polydimethylsiloxane with γ‐aminopropyltriethoxysilane (γ‐APS) as compatibilizer and dibutyltindilaurate as catalyst. The reaction between hydroxyl‐terminated polydimethylsiloxane and epoxy resin was confirmed by IR spectral studies. The siliconized epoxy systems were further modified with 5, 10, and 15 wt % of bismaleimide (BMI). The matrices, in the form of castings, were characterized for their mechanical properties. Differential scanning calorimetry and thermogravimetric analysis of the matrix samples were also performed to determine the glass‐transition temperature and thermal‐degradation temperature of the systems. Data obtained from mechanical studies and thermal characterization indicate that the introduction of siloxane into epoxy improves the toughness and thermal stability of epoxy resin with reduction in strength and modulus values. Similarly the incorporation of bismaleimde into epoxy resin improved both tensile strength and thermal behavior of epoxy resin. However, the introduction of siloxane and bismaleimide into epoxy enhances both the mechanical and thermal properties according to their percentage content. Among the siliconized epoxy/bismaleimide intercrosslinked matrices, the epoxy matrix having 5% siloxane and 15% bismaleimide exhibited better mechanical and thermal properties than did matrices having other combinations. The resulting siliconized (5%) epoxy bismaleimide (15%) matrix can be used in the place of unmodified epoxy for the fabrication of aerospace and engineering composite components for better performance. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 38–46, 2001     

Rheological,mechanical, and electrical properties of Sr0.7Bi0.2TiO3 modified BaTiO3 ceramic and its composites

Porous BaTiO₃-based relaxor ferroelectric ceramics with lamellar structure were achieved by ice templating method, and the rheological properties of ceramic slurry for freeze casting were deeply studied. Epoxy resin was then backfilled to generate ceramic–epoxy resin composites. Ceramic–epoxy composites with a lamellar structure were obtained when using a slurry with a ceramic content of 45 wt.%. The nanoindentation results showed that the introduction of ceramic materials into the epoxy resin can significantly improve the penetration resistance and hardness of the material. The dielectric and ferroelectric properties of the composites were also characterized. The interaction between the highly coupled dipoles in the polymers results in a decrease in the breakdown field strength of the composite. The dielectric constant reached up to ∼800. At 220 kV/cm, W_rec = 0.62 J/cm³, and η was ∼80%. At low frequencies, W_rec was ∼0.16 J/cm³, which indicated good stability.     

聚氨酯改性环氧树脂的制备及其粘接性能

制备了聚氨酯(PU)改性环氧树脂(EP),使用红外光谱(FT-IR)和扫描电子显微镜(SEM)对其结构进行了表征,并对其固化物的热性能和动态热机械性能进行了研究;以PU改性EP为基体树脂制备胶粘剂,并对该胶粘剂的性能进行了测定。实验结果表明,由于PU链段可以改善EP的韧性,并且两者相容性较好,故由此制取的胶粘剂综合性能良好,其拉伸剪切强度为16MPa、粘接拉伸强度为35MPa且断裂伸长率为1.8%。     

Using organic montormollontrite to reinforce the structure and flexural property of denture base nanocomposites

The denture bases nanocomposites were prepared by adding organic montormollontrite(OMMT) into poly(methyl methacrylate) matrix. The resulting composites were characterized by XRD, TEM, and ISTRON 3365 flexural strength testing systems. One‐way analysis of variance and Tukey's test were used to compare the difference in flexural strength and flexural modulus. The results showed the formation of exfoliated‐intercalated and intercalated denture base nanocmposite when the content of OMMT was 3 wt % and 5 wt % in the powder of denture base resin, respectively. The maximum ultimate flexural strength was observed in denture base nanocomposite containing 3 wt % of OMMT and flexural strength decreased with further increases of OMMT content. The flexural modulus of denture base nanocomposite increased continually with OMMT content increasing from 1 wt % to 10 wt %. Significant difference in both flexural strength and flexural modulus was observed between the nanocomposites with 3 wt % OMMT and controls (n = 5, P < 0.05). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and modification of trifunctional epoxy resin with amine terminated polydimethyl siloxanes for semiconductor encapsulation application

Epoxy resins based on the triglycidyl ether of tris(hydroxyphenyl)methane (TETM) possess a very high heat distortion temperature and superior thermal oxidative stability over other types of epoxy resins. The high performance trifunctional epoxy resin (TETM) was synthesized by the condensation of a hydroxybenzaldehyde with phenol followed by epoxidation with a halohydrin. The structure of the synthesized TETM was confirmed by infrared (IR), mass spectra (MS), and nuclear magnetic resonance (NMR) spectroscopy. Amine terminated polydimethylsiloxanes (ATPDMS) were used to reduce the stress of trifunctional epoxy resin cured with phenolic novolac resin for electronic encapsulation applications. The dispersed silicone rubbers effectively reduce the stress of cured epoxy resins by reducing the coefficient of thermal expansion (CTE) and flexural modulus, while the glass transition temperature (T_g) is depressed by only a small amount.     

Multifunctional Cu2+‐montmorillonite/epoxy resin nanocomposites with antibacterial activity

Multifunctional nanocomposites can be achieved by addition of modified layered nanoclays to impart to the final materials a designed set of properties. The easy reproducible preparation of copper modified montmorillonite has been reported here together with its spectroscopic characterization, including ²⁹Si NMR in the solid state. Epoxy‐nanocomposites and glass fiber reinforced laminates containing 1% wt and 3% wt of Cu²⁺‐MMT have been prepared and characterized. Thermal and mechanical properties have been evaluated. The experiments carried out to evaluate the antibacterial activity showed that the epoxy‐resin nanocomposites with 3% wt of Cu²⁺‐MMT exhibited an inhibition action higher than 96% against Escherichia coli and Staphylococcus aureus. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44733.     

Fiber‐reinforced nanopigmented poly(methyl methacrylate) as improved denture base

Nanopigmented and fiber‐reinforced poly (methyl methacrylate) (PMMA) were synthesized for denture bases, by incorporating E‐glass fibers, flock fibers, or polyethylene fibers into the PMMA powder formulation to improve the flexural behavior and porosity; decreasing the Candida albicans adherence and being noncytotoxic. The commercial acrylic resin, Lucitone 199 was used as a control group. Scanning electron microscopy analysis was performed to the PMMA particles and the reinforcing fibers. Flexural strength increased by adding E‐glass fibers in the PMMA powder as compared to flock and polyethylene fibers. The reinforced PMMA with flock fibers showed the lower porosity even smaller than Lucitone 199. The synthesized PMMA and the fiber reinforced nanopigmented PMMA groups reduced significantly the C. albicans adherence when compared to the commercial acrylic resin. All the tested groups were found to be nontoxic materials after being in contact with mouse fibroblast culture during 24 h, showing that these novel nanostructured composites are suitable for producing adequate and nontoxic reinforced materials with antimicrobial properties for dentistry applications. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Curing,Spectral and Thermal Study of Epoxy Resin of Bisphenol-C and Its Polyester Polyols Based Polyurethanes

Epoxy resin of bisphenol-C (EBC), its ricinoleate- and linoleate-based polyols have been cured using 5–25 wt% triethylamine and toluene-2,4-di-isocyanate at 100° and 140°C, respectively. Cured resins are insoluble in common solvents and characterized by IR, DSC and TGA. Amine-cured resin was thermally stable up to about 309–318°C and followed 1.5-order degradation kinetics. Ricinoleate-based polyurethane was thermally stable up to about 215°C and followed 0.43-, 0.75-, and 1.12-order degradation kinetics. Linoleate-based polyurethane was thermally stable up to about 260°C and followed, respectively, 1.9- and 0.93-order degradation kinetics. Kinetic parameters are interpreted in light of resin structure and nature of hardeners used. Amine-cured epoxy resin possesses better thermal properties than those of its polyols-based polyurethanes.     

Contrast on tensile and flexural properties of glass powder reinforced epoxy composites: Pilot study

Epoxy resin was filled with glass powder to optimize the tensile and flexural strength of the composite for structural applications by a research center in the University of Southern Queensland (USQ). To reduce costs, the center wishes to fill as much glass microspheres as possible subject to maintaining sufficient strength of the composites in structural applications. This project varies the percentage by weight of the glass powder in the composites. After casting the composites to the molds, they were cured at ambient conditions for 24 h. They were then postcured in a conventional oven and subjected to tensile and flexural tests. The contribution of the study was that if tensile and flexural properties were the most important factors to be considered in the applications of the composites, the maximum amount of glass powder can be added to the resin will be five (5) percent. It was also found that the fractured surfaces examined under scanning electron microscope were correlated with the tensile and flexural strength It is also hoped that the discussion and results in this work would not only contribute toward the development of glass powder reinforced epoxy composites with better material properties, but also useful for the investigations of tensile and flexural properties in other composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011