Polymer resins with epoxy end groups obtained from hydrocarbon pyrolysis C9 fraction

Polymer resins with epoxy groups (PREGs) are synthesized by radical copolymerization of hydrocarbon pyrolysis C₉ fraction using 1,2-epoxy-3-tert-butylperoxypropane as the initiator or by copolymerization of the ED-20 epoxy resin modified by tert-butyl hydroperoxide. The effect of the initiator nature and quantity, temperature and reaction time on the yield and characteristic of PREGs are examined. The structure of synthesized products is established by chemical methods and IR spectroscopy. The structurization of ED-22 epoxy resin is studied in the presence of polyethylenamine using 10 and 25 mass% of PREG.     

Synthesis and characterization of petroleum resins with epoxy groups

Pyrolysis of petroleum hydrocarbons (including diesel pyrolysis) aimed at obtaining polyethylene also creates certain liquid products which can be used for making so-called petroleum resins (PRs). The C₉ fraction from pyrolysis contains among others, styrene and its derivatives, indene and pentanodiene. Petroleum resins with epoxy groups (PREs) have been synthesized by oligomerization of unsaturated components of the C₉ fraction in the presence of 4,4′-azo-bis-[2,3-epoxypropoxy-4-cyano-pentanenitrile] (AEPCP) used as an azoinitiator. The influence of azoinitiator quantity, temperature and time of oligomerization upon the yield and characteristics of the resulting functional petroleum resins has been evaluated. The structure of the products was confirmed by IR-spectroscopy. Our PREs have potential applications as active additives to industrial epoxy resins based on Bisphenol A.     

γ射线辐照对碳纤维表面接枝改性的影响

为提高碳纤维/环氧树脂复合材料的界面粘结性能, 采用γ射线共辐照接枝方法对碳纤维表面改性, 利用X光电子能谱仪(XPS)、 扫描电子显微镜(SEM)、 电子万能材料试验机, 研究了在缩乙二醇丙酮溶液和环氧氯丙烷丙酮溶液中经200 kGy剂量的γ射线辐照接枝后, 碳纤维的表面化学元素及官能团组成、 表面形貌、 复合材料剪切断面形貌及其层间剪切强度(ILSS)的变化。研究表明, 缩乙二醇类接枝液的接枝效果较理想, 碳纤维接枝率达7%; 辐照处理碳纤维表面O/C比值和含氧官能团含量增加, 以此制备的碳纤维/环氧复合材料的ILSS提高, 最大提高率达31.2%; 同时还发现辐照接枝后的碳纤维表面粗糙度增大。     

Effect of superheated steam treatment of carbon fiber on interfacial adhesion to epoxy resin

To elucidate the effect of superheated steam (SHS) treatment of carbon fiber on the adhesion to epoxy resin and surface states, virgin unsized carbon fiber was exposed to SHS with or without N₂ in the temperature range of 500–800 °C. The interfacial shear strength (IFSS) between the carbon fiber and epoxy resin was successfully improved by SHS treatment with N₂, and the IFSS of fiber treated above 700 °C was the same as or higher than that of a commercial sized fiber. SHS treatment without N₂ resulted in an increase of total acidic groups on the fiber surface accompanied with the increase of phenolic hydroxyl groups, whereas that with N₂ resulted in a simultaneous increase of total acidic and basic functional groups. The significant improvement in the IFSS after SHS treatment with N₂ is considered to be due to the increase of basicity on the fiber surface.     

Strengthening of basalt fibers with nano-SiO2–epoxy composite coating

Coatings, which were made from pure epoxy and SiO₂ nanoparticle modified epoxy composite, respectively, were applied onto the basalt fiber rovings. The SiO₂ nanoparticles were synthesized using a sol–gel method and modified using coupling agent. Fourier transform infrared spectroscopy (FT-IR) and Differential Scanning Calorimetry (DSC) analyses indicated the formation of modified SiO₂ nanoparticles. The SiO₂ nanoparticle–epoxy composite coating gave rise to a significant increase in the tensile strength of the basalt fibers as compared with the pure epoxy coating, and also the coating endowed the basalt fiber with a promising interfacial property in the basalt fiber reinforced resin matrix composite. The coating modification was an effective way in improving the mechanical properties of basalt fibers and the properties of basalt fiber/epoxy resin composites.     

Preparation and characterization of epoxy composites filled with functionalized nano-sized MCM-41 particles

Mono-dispersed nano-sized MCM-41 (M (with template)) particles were synthesized by sol–gel reaction. The effect of interface modification on the properties of epoxy composites was investigated. Modifications were carried out either by substituting silanol groups on the surface or in the mesopore channels into amine (M-NH₂), calcinating mixture template in the mesopore channels (M(without template)), or recalcinating them at higher temperature to remove silanol groups (–OH) in the mesopore channels or on the surface (CM). Transmission electron micrograph results showed that the dispersing of MCM-41 nanoparticles was not influenced by the modification, while –NH₂ group indeed modified the mesopore channels or the surface of MCM-41 particle by using IR, XRD, and N₂ adsorption–desorption. In addition, tensile tests suggested that M-NH₂ nanoparticles could simultaneously provide epoxy matrix with strengthening and toughening effects. However, due to the different interfacial structures between the fillers and the matrix, the mechanical properties of the composites filled by M-NH₂ were much better than those of composites filled by MCM-41 (without template), MCM-41 (with mixture template), and CM.     

Improvement of epoxy resin properties by incorporation of TiO2 nanoparticles surface modified with gallic acid esters

Epoxy resin/titanium dioxide (epoxy/TiO₂) nanocomposites were obtained by incorporation of TiO₂ nanoparticles surface modified with gallic acid esters in epoxy resin. TiO₂ nanoparticles were obtained by acid catalyzed hydrolysis of titanium isopropoxide and their structural characterization was performed by X-ray diffraction and transmission electron microscopy. Three gallic acid esters, having different hydrophobic part, were used for surface modification of the synthesized TiO₂ nanoparticles: propyl, hexyl and lauryl gallate. The gallate chemisorption onto surface of TiO₂ nanoparticles was confirmed by Fourier transform infrared and ultraviolet–visible spectroscopy, while the amount of surface-bonded gallates was determined using thermogravimetric analysis. The influence of the surface modified TiO₂ nanoparticles, as well as the length of hydrophobic part of the gallate used for surface modification of TiO₂ nanoparticles, on glass transition temperature, barrier, dielectric and anticorrosive properties of epoxy resin was investigated by differential scanning calorimetry, water vapor transmission test, dielectric spectroscopy, electrochemical impedance spectroscopy and polarization measurements. Incorporation of surface modified TiO₂ nanoparticles in epoxy resin caused increase of glass transition temperature and decrease of the water vapor permeability of epoxy resin. The water vapor transmission rate of epoxy/TiO₂ nanocomposites was reduced with increasing hydrophobic part chain length of gallate ligand. Dielectric constant of examined nanocomposites was influenced by gallate used for the modification of TiO₂ nanoparticles. The nanocomposites have better anticorrosive properties than pure epoxy resin, because the surface modified TiO₂ nanoparticles react as oxygen scavengers, which inhibit steel corrosion by cathodic mechanism.     

Nanostructured systems based on SBS epoxidized triblock copolymers and well-dispersed alumina/epoxy matrix composites

In the present research, the effect of addition of (1 wt.% and 3 wt.%) alumina nanoparticles (Al₂O₃) to epoxy modified by poly(styrene-b-butadiene-b-styrene) (SBS) epoxidized triblock copolymer was studied. The microstructure of final hybrid composites was studied with atomic force microscopy (AFM). Composites showed homogeneously dispersed Al₂O₃ nanoparticles in the epoxy matrix containing polystyrene (PS) microphase separated nanodomains. Dynamic mechanical analyses (DMA), flexural and fracture toughness investigations were carried out. The glass transition temperature of epoxy matrix has been retained unchanged by the addition of Al₂O₃ nanoparticles. The nanostructured epoxy systems based on SBS epoxidized triblock copolymer and well-dispersed Al₂O₃ nanoparticles allowed an increase in fracture toughness maintaining the transparency and stiffness of neat epoxy.     

Vinylester/epoxy-based thermosets of interpenetrating network structure: An atomic force microscopic study

The morphology of vinylester (VE) and epoxy (EP) resins, and their combination (VE/EP at a ratio 1/1) was studied by atomic force microscopy (AFM). AFM scans taken on the ion-etched surface of EP showed a featureless homogeneous structure. On the other hand, VE exhibited a two-phase microgel, whereas VE/EP a two-phase interpenetrating network (IPN) structure. A vinylester-urethane hybrid resin (VEUH) showed also the formation of an IPN-like morphology. It was concluded that cross-reactions between the hydroxyl functionality of VE and additional functional groups, such as isocyanate in VEUH or epoxy in VE/EP combinations, strongly favour the IPN formation. AFM scans revealed the compaction of the IPN structure of VE/EP upon post-curing which was associated with a prominent increase in the glass transition temperature (T _g) according to dynamic-mechanical thermal analysis.     

Size reduction of WO3 nanoparticles by ultrasound irradiation and its applications in structural nanocomposites

The porous WO₃ (pore size 2–5 nm) nanoparticles were synthesized using a high intensity ultrasound irradiation of commercially available WO₃ nanoparticles (80 nm) in ethanol. The high resolution transmission electron microscopic (HRTEM) and X-ray studies indicated that the 2–5 nm uniform pores have been created in commercially available WO₃ nanoparticles without much changing the initial WO₃ nanoparticles (80 nm) sizes. The nanocomposites of WO₃/SC-15 epoxy were prepared by infusion of 1 wt.%, 2 wt.% and 3 wt.% of porous WO₃ nanoparticles into SC-15 epoxy resin by using a non-contact (Thinky) mixing technique. Finally the neat epoxy and nanocomposites were cured at room temperature for about 24 h in a plastic rectangular mold. The cured epoxy samples were removed and precisely cut into required dimensions and tested for their thermal and mechanical properties. The HRTEM and SEM studies indicated that the sonochemically modified porous WO₃ nanoparticles dispersed more uniformly over the entire volume of the epoxy (without any settlement or agglomeration) as compared to the unmodified WO₃/epoxy nanocomposites.     

Enhancement of tensile and thermal properties of epoxy nanocomposites through chemical hybridization of carbon nanotubes and alumina

This paper presents the properties of epoxy nanocomposites, prepared using a synthesized hybrid carbon nanotube–alumina (CNT–Al₂O₃) filler, via chemical vapour deposition and a physically mixed CNT–Al₂O₃ filler, at various filler loadings (i.e., 1–5%). The tensile and thermal properties of both nanocomposites were investigated at different weight percentages of filler loading. The CNT–Al₂O₃ hybrid epoxy composites showed higher tensile and thermal properties than the CNT–Al₂O₃ physically mixed epoxy composites. This increase was associated with the homogenous dispersion of CNT–Al₂O₃ particle filler; as observed under a field emission scanning electron microscope. It was demonstrated that the CNT–Al₂O₃ hybrid epoxy composites are capable of increasing tensile strength by up to 30%, giving a tensile modulus of 39%, thermal conductivity of 20%, and a glass transition temperature value of 25%, when compared to a neat epoxy composite.     

Simultaneous epoxy grafting on SiO2 nanoparticles during bead milling and their effects on the mechanical properties of epoxy-based composites

Epoxy resin-grafted SiO₂ nanoparticles stabilized in toluene were successfully designed by the simultaneous surface modification of SiO₂ nanoparticles during bead milling which involves the adsorption of polyethyleneimine-oleic acid complex (PEI-OA) and epoxy resin grafting to the free amine groups of PEI-OA (PEI-OA-Epoxy). The effectiveness of epoxy grafting on the properties of the SiO₂/epoxy based nanocomposites were investigated using a bead-milled SiO₂/toluene suspension stabilized with PEI-OA, PEI-OA-Epoxy, and a complex of PEI and an anionic surfactant comprising an epoxy-soluble polyethylene glycol-based chain (PEI-AS). While SiO₂ nanoparticles were pulverized with similar sizes (c.a. 126–171 nm) and stabilized in toluene with any of the three surface modifications, PEI-OA-stabilized SiO₂ nanoparticles aggregated during processing epoxy-based composites. PEI-AS- and PEI-OA-Epoxy-stabilized SiO₂ nanoparticles maintained their dispersion stability, however, the epoxy composites with PEI-OA-Epoxy-stabilized SiO₂ nanoparticles exhibited better material properties, such as increase in the strain at fracture and higher T_g.     

Corrosion protection of waterborne epoxy coatings containing mussel-inspired adhesive polymers based on polyaspartamide derivatives on carbon steel

A novel mussel-inspired adhesive polymer (PHEA-DOPA) containing the 3,4-dihydroxyphenylalanine (DOPA) functional group based on polyaspartamide derivatives was synthesized. The corrosion protection of the waterborne epoxy coatings containing the adhesive polymers was investigated by electrochemical impedance spectroscopy (EIS). The results indicated that the PHEA-DOPA could improve the corrosion resistance of the waterborne epoxy coating. The corrosion products were also analyzed by Raman microspectroscopy (RM), indicating the formation of the insoluble DOPA-Fe complexes on the carbon steel surface. These complexes simultaneously acting as a passivating layer, can inhibit the process of corrosion at the metal-solution interface. The differential scanning calorimeter (DSC) measurement indicated that PHEA-DOPA can increase the crosslinking density of coating. The effect of O₂ on the protective mechanism of the PHEA-DOPA coating in a 3.5% NaCl solution was also evaluated by EIS. The results indicated that the barrier effect was significantly improved under aerated conditions because DOPA was oxidized to DOPA–quinone (Dq) by O₂, which triggered the reaction with Fe ions that were released from the surface of the carbon steel. This led to more compact coatings.     

Influence of sequence of chemical reactions on kinetics and solid state behavior for bisphenol A diglycidyl ether – bisphenol A – sulfanilamide ternary blends

The kinetics of reaction of ternary blends based on Bisphenol A diglycidyl ether, Bisphenol A and sulfanilamide curing agent was investigated using FTIR, HPLC, SEC following two different synthesis paths. Four the same initial composition prepolymers differing by the cross-link point distribution and the chain length between cross-links have been synthesized and their solid state behavior has been studied. For the formulation DGEBA:SAA:BA = 4.0:1.25:1.5 mol (catalyst - 0.005 e.e.w. DGEBA), though the schedules have different kinetics, finally the prepolymers with equal conversion of epoxy groups and mass-average molar mass were obtained by both schedules. The dynamic mechanical spectroscopy performed in the glass transition region displays the evolution of the viscoelastic characteristics as a function of cross-link density. For similar formulations networks obtained by schedule 1 have higher values of T _g and σ _y than networks obtained by schedule 2, perhaps due to a higher real cross-link density. Received: 18 September 2000 / Reviewed and accepted: 20 September 2000     

The effect of hyperbranched polyester and zirconium slag nanoparticles on the impact resistance of epoxy resin thermosets

A hyperbranched polyester (HBP) was synthesized through a polymerization of AB₂ approach with succinic anhydride and diethanolamine. The effect of HBP and Zirconium slag nanoparticle (ZSN, a kind of solid waste in Zirconium industry) content on the toughness enhancement and morphology of diglycidyl ether of bisphenol A epoxy resin (DGEBA) thermosets was studied. The results indicated that HBP can greatly improve the impact strength (IS) of epoxy thermosets, but the flexural strength (FS) was decreased with increasing the HBP content. The IS of epoxy thermosets modified with ZSN was also improved, and the FS decreases as increase of ZSN. The thermosets modified with both HBP and ZSN showed excellent IS and FS. The toughening enhancement mechanism was also discussed.     

Moisture absorption by cyanate ester modified epoxy resin matrices. Part V: effect of resin structure

A series of epoxy resins of varying functionality (in terms of the number of epoxide groups) were used to cure the cyanate ester resin, AroCy L10 (1,1-bis(4-cyanatophenyl) ethane). The effect of thermal spiking on moisture absorption and changes in glass transition temperature (T_g) were studied.With the tetra functional (MY720) epoxy a more polar crosslinked density matrix forms. However, after thermal spiking to 140 °C a second peak appeared in the DMTA spectrum which was attributed to partial hydrolysis. The other two systems were much more stable.All systems exhibited the enhancement of moisture absorption as a result of thermal spiking.The mechanism of this phenomenon has been discussed in detail and related to the distribution of unoccupied volume in the dry resin and the location of water molecules at hydrogen bonding sites. The redistribution of the water molecules throughout the sites during thermal cycling is considered responsible for the enhancement and the reduction in moisture contents at high thermal spike temperatures.     

Hybrid C/Pet/epoxy composites

Hybrid carbon/PET/epoxy composites were prepared by a wet layup technique and characterized by standard methods of fracture and impact tests. The influence of PET fibre surface treatment with polyfunctional amine on the composite properties has been studied in order to determine the role of the fibre/matrix interface. The state of the fibre/matrix interface has been examined by several techniques, such as SEM, differential scanning calorimetry (DSC) and contact angle measurements. A significant hybrid effect of the PET/aminated fibres on the curing reaction and T _g of the epoxy matrix in the composites was established. It is probably due to the reaction between the amine groups of the fibre surface and the epoxy component of the resin, as determined by DSC.     

碳纤维/TiO2改性树脂复合材料的制备及力学性能

针对环氧树脂脆性大、与碳纤维形成的界面性能较差等问题,本文选用纳米TiO₂对5284环氧树脂进行改性,并以角联锁机织物为增强体制备了碳纤维/环氧树脂复合材料。使用FT-IR、旋转流变仪、表面张力仪等设备对TiO₂/环氧树脂进行表征,并研究了树脂改性对复合材料压缩与层间剪切性能的影响。研究表明：TiO₂的羟基与环氧树脂的环氧基和羟基发生了反应;经1wt.%TiO₂改性的树脂复数黏度为0.066 Pa·s,纤维与树脂间接触角为28.85°,浸润效果较好;相较于未改性复合材料,树脂改性的复合材料纵向压缩强度与模量分别提高了7.46%和11.03%,横向压缩强度与模量分别提高了6.99%和4.96%,纵向、横向的剪切强度分别提高了6.88%和4.65%。TiO₂改性环氧树脂提高了复合材料的承载能力,改善了界面结合强度。     

碳纳米管的表面改性对环氧树脂低温(77 K)冲击性能及热膨胀系数的影响

采用混酸氧化及表面接枝改性的方法制备了表面含不同官能团的多壁碳纳米管(MWCNTs), 并研究了不同MWCNTs对环氧树脂的低温(77 K)抗冲击性能及热膨胀系数(CTE)的影响。结果表明: 通过接枝反应将—NCO基团封端的PEO齐聚物引入MWCNTs表面, 可提高MWCNTs在环氧树脂基体中的分散性, 加强MWCNTs与环氧树脂的界面作用; 相对于纯环氧树脂, 添加质量分数为0.5%的纯MWCNTs、 氧化MWCNTs和表面接枝MWCNTs改性后的环氧树脂的低温冲击强度分别升高了10.27%、 26.13%和32.95%, 而CTE则分别降低了14.79%、 29.59%和40.29%。这表明表面接枝改性MWCNTs可明显提高环氧树脂基体的低温抗冲击性能并降低环氧树脂在玻璃化转变温度下的CTE。     

Cyclic fatigue crack propagation of nanoparticle modified epoxy

An experimental study on the fatigue performance of nanoparticle modified epoxy was conducted. Seven material systems were examined which were: neat epoxy (E), 6 and 12 weight percent (wt.%) silica nanoparticle modified epoxy (S6, S12), 6 and 12 wt.% rubber nanoparticle modified epoxy (R6, R12), 3 wt.% each of silica and rubber nanoparticle modified epoxy (S3R3) and 6 wt.% each of silica and rubber nanoparticle modified epoxy (S6R6). Effects of those nanoparticles on the fatigue threshold (ΔG_th and ΔK_th) and fatigue crack propagation rates (da/dN) were studied. It was found that, compared to neat epoxy (E), nanosilica (S6, S12) increased ΔG_th (and ΔK_th) but nanorubber (R6 and R12) did not. However, a synergistic effect was observed on the fatigue threshold when both silica and rubber nanoparticles were added into epoxy. All these nanoparticles, individually or conjointly, decreased da/dN with silica the most effective. Morphology of the fracture surface was examined to understand the role of nanoparticles on toughening mechanisms under cyclic loading, which depended on the applied ΔG levels.