Preparation of thermal-enhanced epoxy resin adhesive with organic PCM for applying wood flooring

Epoxy resins are well-known materials that show beneficial properties, such as high tensile strength and modulus, good adhesive properties, low cost, and ease of processing and environmental advantages. However, epoxy resin adhesive has no characteristic of thermal storage. Latent heat storage is one of the favorable kinds of thermal energy storage methods considered for energy saving and thermal efficiency in various fields, such as solar air conditioning systems and buildings. So we prepared thermal-enhanced epoxy resin adhesive by using PCM. This paper addresses the effects of n-hexadecane and sodium lauryl sulfate on the thermal properties and chemical properties of epoxy resin adhesive and HEAC, using differential scanning calorimetry, thermal gravimetric analysis, and Fourier transform-infrared spectroscopy. Also, we evaluated the applicability of composite epoxy resin adhesive to wood-based flooring using n-hexadecane, through measurement of bonding strength from universal testing machine analysis.     

Thermally stable liquid crystalline thermosets based on aromatic copolyesters: Preparation and properties

The synthesis and physical properties are described for a thermally stable liquid crystalline (LC) thermoset based on all aromatic ester units. The persistence of the liquid crystalline phase throughout the curing process was monitored with polarizing optical microscopy. The applicability of these new liquid crystalline thermosets has been evaluated for use as an adhesive for bonding metals, namely titanium. The failure of the adhesive bonds always occurs within the polymer; thus it can be inferred that bonding at the polymer-metal interface is very good. This strong interfacial bonding is attributed to low cure shrinkage and CTE matching of the underlying substrate by the LC resins. The cohesive properties and strength of the cured resin can be greatly enhanced by the addition of filler materials. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35:1061–1067, 1997     

Synthesis and characterization of epoxy resins containing imine group and their curing processes with aromatic diamine

The epoxy resins containing imine bonding were prepared from hydroxyl substituted Schiff base monomers in two steps. At the first step, hydroxyl substituted Schiff base monomers were synthesized via condensation reaction. At the second step, epoxy resins were synthesized from the reaction between Schiff base monomers and epichlorohydrine (EPC). Then curing processes of epoxy resins were achieved by p-phenylenediamine compound. The structures of resulting compounds were confirmed by FT-IR, UV-Vis and ¹H-NMR. TG-DTA and DSC measurements were performed for thermal characterizations of the compounds. Chemical resistances of the cured epoxy-amine systems were determined for coating applications in acidic, alkaline and organic solvents. HCl (10%, aqueous solution), NaOH (10%, aqueous solution), DMSO, DMF, N-methylpyrrolidone, ethanol, THF and acetone were used for corrosion tests. Chemical resistance data of the synthesized epoxy resins demonstrated that they have good chemical resistance against various acid, alkaline and common organic solvents. Surface morphologies of epoxy resin and the cured epoxy resin were determined with scanning electron microscopy (SEM) measurements. Also, optical band gap (E_g) values of Schiff base monomers and epoxy resins were calculated from UV-Vis measurements.     

Preparation and Characterization of DGEBA/EPN Epoxy Blends with Improved Fracture Toughness

The physical and mechanical properties of blends composed of two kinds of epoxy resins of different numbers of functional groups and chemical structure were studied.One of the resins was a bifunctional epoxy resin based on diglycidyl ether ofbisphenol A and the other resin was a multifunctional epoxy novolac resin.Attempt was made to establish a correlation between the structure and the final properties of cured epoxy samples.The blend samples containing high fraction of multifunctional epoxy resin showed higher solvent resistance and lower flexural modulus compared with the blends containing high fraction of bifunctional epoxy resin.The epoxy blends showed significantly higher ductility under bending test than the neat epoxy samples.The compressive modulus and strength increased with increasing of multifunctional epoxy in the samples,probably due to enhanced cross-link density and molecular weight.Morphological analysis revealed the presence of inhomogeneous sub-micrometer structures in all samples.The epoxy blends exhibited significantly higher fracture toughness (by 23％ at most) compared with the neat samples.The improvement of the fracture toughness was attributed to the stick-slip mechanism for crack growth and activation of shear yielding and plastic deformation around the crack growth trajectories for samples with higher content of bifunctional epoxy resin as evidenced by fractography study.     

Polymer alloy adhesive film made up of epoxy resin and aromatic polyester

Printed wiring boards (PWBs) with high wiring density such as thin multilayer PWBs and flexible PWBs requiring bonding sheets with superior thermal and adhesive properties, and must have a flat board surface. To meet these requirements, a polymer alloy adhesive film made up of epoxy resins and aromatic polyester has been developed. The crosslinking reaction between the components was utilized to improve thermal properties. The polymer alloy adhesive film demonstrates good heat resistance and adhesiveness. It features a low processing pressure of 2 MPa at 170°C and gives the board surface greater flatness, which is better for the fine wiring of PWBs.     

Effect of poly(arylene ether ketone)s of different chemical constitutions on adhesion properties of epoxyamine binder

The adhesive strength at the bipolymer blend/fiber interface was determined by the pull-out method. Epoxy resin blends with heat-resistant linear thermoplastics, poly(arylene ether ketone)s of different molecular masses and chemical compositions, were used as adhesives, and a steel wire of 150 μm diameter was used as a substrate. It was found that the addition of 5–20 wt % poly(arylene ether ketone) to epoxy resin results in a 10–20% increase in the adhesive strength; a sharp gain in the adhesive strength (by 50–80%) is observed at a modifier content of 30%. The introduction of nanoparticles (Na⁺-montmorillonite) into the epoxy resin-poly(arylene ether ketone) blend increases the strength of adhesive bonding to steel wire. Possible reasons for the observed changes in the adhesive strength are discussed.     

Insertion of nano-crystalline cellulose into epoxy resin via resilin to construct a novel elastic adhesive

Development of high-performance bio-nanocomposite adhesives is of high interest due to their environmentally friendly nature and superior mechanical properties in outdoor environments. Nano-crystalline cellulose (NCC) and resilin are among the most promising bio-nanofillers, providing strength and elasticity, respectively. A novel bio-nanocomposite comprised of NCC and resilin fused to a cellulose binding domain (Res.-CBD) is presented. As a case study, commercial epoxy adhesive was chosen as a matrix for the bio-nanocomposite adhesive. Insertion of hydrophilic NCC into hydrophobic resins, such as epoxy, is typically performed using solvent exchange, chemical modification, emulsifier addition or mixing with water-borne resins, techniques which either limit the material’s application range or which are considered environmentally unfriendly. The unique approach presented here employed Res.-CBD as a surfactant-like agent supportive of the direct insertion of water-suspended NCC into an epoxy resin. The presented approach involves binding of Res.-CBD to NCC through its CBD domain and a chemical reaction between the resin epoxide groups and Res.-CBD amine moieties. The resulting bio-nano material shows a 50 % increase in the Young’s modulus and a 20 % decrease in the tan(δ), compared to pristine epoxy. This novel epoxy adhesive can be advantageous in applications where higher elasticity and Young’s modulus are required.     

Modification of epoxy resin using reactive liquid (ATBN) rubber

Epoxy resins are widely utilised as high performance thermosetting resins for many industrial applications but unfortunately some are characterised by a relatively low toughness. In this respect, many efforts have been made to improve the toughness of cured epoxy resins by the introduction of rigid particles, reactive rubbers, interpenetrating polymer networks and engineering thermoplastics within the matrix.In the present work liquid amine-terminated butadiene acrylonitrile (ATBN) copolymers containing 16% acrylonitrile is added at different contents to improve the toughness of diglycidyl ether of bisphenol A epoxy resin using polyaminoimidazoline as a curing agent. The chemical reactions suspected to take place during the modification of the epoxy resin were monitored and evidenced using a Fourier transform infrared. The glass transition temperature (T_g) was measured using a differential scanning calorimeter. The mechanical behaviour of the modified epoxy resin was evaluated in terms of Izod impact strength (IS), critical stress intensity factor, and tensile properties at different modifier contents. A scanning electron microscope (SEM) was used to elucidate the mechanisms of deformation and toughening in addition to other morphological features. Finally, the adhesive properties of the modified epoxy resin were measured in terms of tensile shear strength (TSS).When modifying epoxy resin with liquid rubber (ATBN), all reactivity characteristics (gel time and temperature, cure time and exotherm peak) decreased. The infrared analysis evidenced the occurrence of a chemical reaction between the two components. Addition of ATBN led to a decrease in either the glass transition temperature and stress at break accompanied with an increase in elongation at break and the appearance of some yielding. As expected, the tensile modulus decreased slightly from 1.85 to about 1.34 GPa with increasing ATBN content; whereas a 3-fold increase in Izod IS was obtained by just adding 12.5 phr ATBN compared to the unfilled resin. It is obvious that upon addition of ATBN, the Izod IS increased drastically from 0.85 to 2.86 kJ/m² and from 4.19 to 14.26 kJ/m² for notched and unnotched specimens respectively while K_IC varies from 0.91 to 1.49 MPa m^1/2 (1.5-fold increase). Concerning the adhesive properties, the TSS increased from 9.14 to 15.96 MPa just by adding 5 phr ATBN. Finally SEM analysis results suggest rubber particles cavitation and localised plastic shear yielding induced by the presence of the dispersed rubber particles within the epoxy matrix as the prevailing toughening mechanism.     

Flame retardancy of fibre-reinforced epoxy resin composites for aerospace applications

The applicability of phosphorus-containing reactive amine, which can be used in epoxy resins both as crosslinking agent and as flame retardant, was compared in an aliphatic and an aromatic epoxy resin system. In order to fulfil the strong requirements on mechanical properties of the aircraft and aerospace applications, where they are mostly supposed to be applied, carbon fibre-reinforced composites were prepared. The flame retardant performance was characterized by relevant tests and mass loss type cone calorimeter. Besides the flame retardancy, the tensile and bending characteristics and interlaminar shear strength were evaluated. The intumescence-hindering effect of the fibre reinforcement was overcome by forming a multilayer composite, consisting of reference composite core and intumescent epoxy resin coating layer, which proved to provide simultaneous amelioration of flame retardancy and mechanical properties of epoxy resins.     

聚苯基硅氧烷与聚甲基苯基硅氧烷改性环氧树脂的合成与性能比较

热熔法制备了一系列聚苯基甲氧基硅氧烷(PPMS)、聚甲基苯基甲氧基硅氧烷(PMPS)改性环氧树脂,通过环氧值、红外光谱(IR)分析表明聚硅氧烷接枝了E-20环氧树脂且环氧基保持不变.探讨了有机硅含量对改性树脂固化体系耐热性能及韧性的影响.实验表明,当E-20环氧树脂与PPMS、PMPS的质量比为7∶3时,改性树脂固化体系的耐热性能明显提高,玻璃化转变温度(Tg)为95.8、88.3℃,分别比改性前提高了9.0℃和1.5℃;质量损失50%时的热分解温度(Td)为476.5、487.8℃,分别比改性前提高了58.3℃和69.5℃.与ED-30固化体系相比,EPMS-30固化物的耐热性能,韧性等力学性能提高的更加明显,并且还具有优良的涂膜性能.     

Synthesis and characterization of thiocarbonohydrazone-based epoxy resins

Novel epoxy resins of various thiocarbonohydrazones have been synthesized by reacting the aldehyde or ketone derivatives of thiocarbohydrazide with excess of epichlorohydrin. The resins have been characterized by elemental analyses, epoxy equivalents, ¹H-NMR and IR spectra, thermal analyses, and viscosity measurements. Curing of the resins has been carried out by mixing with thiocarbohydrazide or ethylenediamine and heating at 80°C for 48 h. A comparison of the thermal stability of the cured resin samples has been made.     

Statistical Analysis of Polymer Nanocomposites for Mechanical Properties

Epoxy resins, due to their high stiffness, ease of processing, good heat, and chemical resistance obtained from cross-linked structures, have found applications in electronics, adhesives coatings, industrial tooling, and aeronautic and automotive industries. These resins are inherently brittle, which has limited their further application. The emphasis of this study is to improve the properties of the epoxy resin with a low-concentration (up to 0.4% by weight) addition of Multi-Walled Carbon Nanotubes (MWCNTs). Mechanical characterization of the modified composites was conducted to study the effect of MWCNTs infusion in the epoxy resin. Nanocomposites samples showed significantly higher tensile strength and fracture toughness compared to pure epoxy samples. The morphological studies of the modified composites were studied using Scanning Electron Microscopy (SEM).     

Preparation and characterization of functionalized graphene oxide/carbon fiber/epoxy nanocomposites

Graphene oxide (GO) was functionalized using three different diamines, namely ethylenediamine (EDA), 4,4′-diaminodiphenyl sulfone (DDS) and p-phenylenediamine (PPD) to reinforce an epoxy adhesive, with the aim of improving the bonding strength of carbon fiber/epoxy composite. The chemical structure of the functionalized GO (FGO) nanosheets was characterized by elemental analysis, FT-IR and XRD. Hand lay-up, as a simple method, was applied for 3-ply composite fabrication. In the sample preparation, the fiber-to-resin ratio of 40:60 (w:w) and fiber orientations of 0°, 90°, and 0° were used. The GO and FGO nanoparticles were first dispersed in the epoxy resin, and then the GO and FGO reinforced epoxy (GO- or FGO-epoxy) were directly introduced into the carbon fiber layers to improve the mechanical properties. The GO and FGO contents varied in the range of 0.1–0.5 wt%. Results showed that the mechanical properties, in terms of tensile and flexural properties, were mainly dependent on the type of GO functionalization followed by the percentage of modified GO. As a result, both the tensile and flexural strengths are effectively enhanced by the FGOs addition. The tensile and flexural moduli are also increased by the FGO filling in the epoxy resin due to the excellent elastic modulus of FGO. The optimal FGO content for effectively improving the overall composite mechanical performance was found to be 0.3 wt%. Scanning electron microscopy (SEM) revealed that the failure mechanism of carbon fibers pulled out from the epoxy matrix contributed to the enhancement of the mechanical performance of the epoxy. These results show that diamine FGOs can strengthen the interfacial bonding between the carbon fibers and the epoxy adhesive.     

具高耐热性多芳烃结构环氧树脂的研究

综述了近年来具耐热性多芳烃结构环氧树脂的发展概况,包括萘系、蒽系和芘系环氧树脂,着重介绍了其合成途径、反应活性及结构与性能的关系.认为多芳烃结构环氧树脂具有良好的耐热耐湿性,颇具发展潜力.其中,萘系环氧树脂与蒽、芘系环氧树脂相比 ,具有较高的反应活性和耐热性,具有较高的实际应用价值.因此,近年来萘基环氧树脂受到研究人员和厂商的关注,并且一些萘系环氧树脂已经应用于生产.     

Improvement in strength of the aluminium/epoxy bonding joint by modification of the interphase

This contribution describes the influence of different surface pre-treatments including self-assembly of phosphoric acid mono alkyl ester as adhesion promoter (AP) for adhesive bonding of aluminium alloy AlMg3. The investigations were performed using a cold hardening two components epoxy-adhesive. The pre-treated surfaces, the interphase structures and the joints were characterized by: SEM/EDX, surface tension, XPS, DMA and the determination of mechanical parameters. The results interestingly show that the test sample with three step pre-treatment (degreasing in acetone, then anodic oxidation in phosphoric acid and adsorption of AP) has the highest adhesive strength and durability.     

Determination of Water Diffusion Coefficients and Dynamics in Adhesive/ Carbon Fiber Reinforced Epoxy Resin Composite Joints

To determinate the water diffusion coefficients and dynamics in adhesive/carbon fiber reinforced epoxy resin composite joints,energy dispersive X-ray spectroscopy analysis(EDX)is used to establish the content change of oxygen in the adhesive in adhesive/carbon fiber reinforced epoxy resin composite joints.As water is made up of oxygen and hydrogen,the water diffusion coefficients and dynamics in adhesive/carbon fiber reinforced epoxy resin composite joints can be obtained from the change in the content of oxygen in the adhesive during humidity aging,via EDX analysis.The authors have calculated the water diffusion coefficients and dynamics in the adhesive/carbon fiber reinforced epoxy resin composite joints with the aid of both energy dispersive X-ray spectroscopy and elemental analysis.The determined results with EDX analysis are almost the same as those determined with elemental analysis and the results also show that the durability of the adhesive/carbon fiber reinforced epoxy resin composite joints subjected to silane coupling agent treatment is better than those subjected to sand paper burnishing treatment and chemical oxidation treatment.     

基于可逆动态共价化学的新型可修复、可回收、可加工环氧树脂

利用生物来源的二聚脂肪酸为原料,合成了二聚酸酰肼和二聚酸酰腙两种衍生物,并进一步以其作为环氧E-44树脂固化剂,得到了新型的含动态共价连接的热固性环氧树脂。采用傅里叶红外光谱(FT-IR)、差式扫描量热(DSC)、扫描电子显微镜(SEM)、热重(TG)和动态力学分析(DMA)等多种测试手段对环氧树脂固化过程以及固化后材料的结构与性能关系进行了详细表征,特别研究了动态亚胺键对热固性环氧树脂性能的独特影响。结果表明:与传统环氧树脂相比,改性后的环氧树脂有更好的韧性,且其玻璃化转变温度及热稳定性没有明显下降。在升温和加压的条件下,酸可催化亚胺键的动态交换反应,赋予传统环氧树脂以全新的可修复、可回收与可多次加工性能。     

Novel Epoxy Resins Derived from Biomass Components

Biomass has received considerable attention because it is renewable and offers the prospect of circulation of carbon in the ecological system. The concept “Biorefinery” has been developed rapidly in order to establish sustainable industries. Recently, new types of epoxy resins with polyester chains, which can be derived from saccharides, lignin and glycerol, have been investigated. In the above studies, the relationship between chemical structure and physical properties was investigated. In the present review, the features of the preparation system and the action of biomass components in epoxy resin polymer networks are described. The glass transition temperatures of the epoxy resins increased with increasing content of biomass components in epoxy resin polymer networks. Thermal decomposition temperatures were almost constant regardless of the content of biomass components contents in epoxy resins. Mass residue at 500 °C increased with increasing contents of biomass components in epoxy resins. It was found that the thermal properties can be controlled by changing the contents of biomass components.     

Epoxy resins and epoxy blends studied by near infra-red spectroscopy

The cure and the final network of epoxy resins have been investigated by numerous techniques, nevertheless a clear understanding of this network structure has not yet been achieved. FTIR analysis of polymeric materials provides highly precise measurements that are widely interpretable in terms of chemical structure. Yet the high absorption of fundamental bands requires careful sample preparation to reduce the thickness of the sample or special reflection techniques are needed. Furthermore, the occurrence of overlapping bands for epoxy resin (N-H and O-H vibrations in the 3000 cm⁻¹ region) renders the quantitative analysis in the region mid IR particularly difficult. However, the overtone and combination bands are 10–100 times weaker than the fundamental ones and are observed in near infrared (NIR) region. Longer pathlengths than Mid IR ones can be used allowing transmission analysis of thick samples (1-20 mm) without special preparation. NIR absorption bands have different intensities depending on the anharmonicity of vibrations. The strongest absorption bands are due to protons connected to carbon, nitrogen, oxygen. Hydrogen bonding due to inter- and intramolecular interactions can cause band broadening, peak position shifts and intensity variations. NIR spectroscopy is therefore a useful technique to investigate polymeric materials and was used to study the cure reactions of various epoxy resins cured with amine hardener. Using different NIR techniques (reflectance, transmission and microscopy) we will briefly present some results concerning hydrogen bonding between epoxy and amine hardener before curing, epoxy resins, glass/epoxy composites and epoxy/PES (polyethersulfone) blends.     

Synthesis and characterization of novel polythiourethane hardeners for epoxy resins

A novel thiol-terminated polythiourethanes were synthesized from low-molecular-weight di- and multifunctional mercaptans and diisocyanates and employed as curing agent of epoxy resin. The curing reaction of epoxy resin and thermal properties of cured products were investigated with differential scanning calorimetry. Evaluation of climatic ageing resistance was made by the change in mechanical properties. Mechanical studies indicated that the application of polythiourethane has toughening effect and significantly increases ageing resistance of the cured resins. The results of this study indicate that molecular structure and functionality of polythiourethane oligomers are of critical importance in governing the curing mechanism, structure of the network and final properties of epoxy compositions.