Preparation and Properties of Novel Inherent Flame-Retardant Cyclotriphosphazene-Containing Epoxy Resins

A novel flame-retardant cyclotriphosphazene-based epoxy resin (CPEP) was successfully prepared by epoxidation of bis-(4-hydroxyphenylsulfonylphenoxy) tetraphenoxycyclotriphosphazene with epichlorohydrin, and was characterized by ¹H nuclear magnetic resonance (NMR), Fourier transform infrared, and gel permeation chromatography (GPC). Then the blends of CPEP and diglycidyl ether of bisphenol A (E51) with different mass ratios were cured using 4,4′-diaminodiphenylmethane as a curing agent. The curing behaviors and the glass transition temperatures of the resulting thermosets were studied by differential scanning calorimetry. The thermal stabilities and flame-retardant properties of the cured resins were studied by thermogravimetric analysis and UL94 tests, respectively. In addition, mechanical, hydrophobic, and electrical properties were also characterized. Compared to the corresponding E51-based thermosets, the cured resins with a mixture of CPEP and E51 showed better thermal stabilities, higher char yields, and greatly improved flame-retardant properties. Furthermore, relatively good mechanical properties, hydrophobicity, and electric resistance were maintained. The cured resins of CPEP/E51 (mass ratio 1:1) achieved UL94 V-0 rating, indicating that the epoxy resin prepared in this study could be used as a flame-retardant coating material.     

Thermal and Mechanical Properties of Epoxy/Carbon Fiber Composites Reinforced with Multi-walled Carbon Nanotubes

Multi-scale hybrid composite laminates of epoxy/carbon fiber (CF) reinforced with multi-walled carbon nanotubes (MWCNTs) were fabricated in an autoclave. For laminate fabrication, 0.5 wt% of pristine MWCNTs or silane-functionalized MWNCTs (f-MWCNTs) were dispersed into a diglycidyl ether of bisphenol-A epoxy system and applied on the woven carbon fabric. The neat epoxy/CF composite and the MWCNTs-reinforced epoxy/CF hybrid composites were characterized by thermogravimetric analysis (TGA), thermomechanical analysis (TMA), tensile testing, and field emission scanning electron microscopy (FE-SEM). A significant improvement in initial decomposition temperature and glass transition temperature of epoxy/CF composite was observed when reinforced with 0.5 wt% of f-MWCNTs. The coefficient of thermal expansion (CTE), measured by TMA, diminished by 22% compared to the epoxy/CF composite, indicating an improvement in dimensional stability of the hybrid composite. No significant improvement in tensile properties of either MWCNTs/epoxy/CF composites was observed compared to those of the neat epoxy/CF composite.     

Thermal and Tensile Properties of Epoxy Nanocomposites Reinforced by Silane-functionalized Multiwalled Carbon Nanotubes

Epoxy nanocomposites with unmodified multiwalled carbon nanotubes (u-MWCNTs) and silanized multiwalled carbon nanotubes (si-MWCNTs) were prepared by a cast molding method. The effects of 3-aminopropyltriethoxysilane functionalization of MWCNTs on thermal, tensile, and morphological properties of the nanocomposites were examined. The nanocomposites were characterized by thermogravimetric analysis, dynamic mechanical thermal analysis, and tensile testing. The results showed that epoxy composites based on si-MWCNTs showed better thermal stability, glass transition temperature, and tensile properties than the composites based on u-MWCNTs. These results prove the effect of silane functionalization on the interfacial adhesion between epoxy and MWCNTs. This was further confirmed by morphology study of fractured surfaces of nanocomposites by field emission scanning electron microscopy.     

Effect of Silanes on Mechanical and Thermal Properties of Silicone Rubber/EPDM Blends

The effect of four types of silane coupling agents on the mechanical and thermal properties of silicone rubber and ethylene–propylene–diene monomer (M-class) rubber (EPDM) blends is studied, namely, isobutyltriethoxysilane (BUS), acryloxypropyltriethoxysilane (ACS), aminopropyltriethoxysilane (AMS), and vinyltriethoxysilane (VIS). ACS and VIS increase the crosslink density of the blends, which results in higher tensile strength, modulus, and thermal stability, but lower elongation at break compared with the other silanes. However, the blend containing BUS shows highest tanδ in the temperature range of 45°C to 200°C. Thermogravimetric analysis shows two steps of degradation for all the samples, but little difference with the varied silanes.     

含稀土铕(Ⅲ)配合物光学树脂的制备及光学性能的研究

报道了将多种稀土铕（Ⅲ）的二元及三元配合物复合于苯乙烯（St)／甲基丙烯酸（HMA）的共聚体系,制备得到具有发光功能的透明光学树脂,对其光学性能进行研究。同时,考察了稀土配合物的含量对聚合物 透明性、发光性能的影响。     

Kinetics Study on Thermal Decomposition of Polyepoxyphenylsilsesquioxane/Epoxy Resin Systems

The thermal decomposition kinetics of epoxy resin (EP) containing polyepoxyphenylsilsesquioxane (PEPSQ) was studied by thermogravimetric analysis (TGA) in a nitrogen atmosphere. Kissinger and Flynn–Wall–Ozawa methods were both used to analyze the thermal decomposition process under nonisothermal conditions. The results showed that a slight increase of activation energy was observed in the presence of PEPSQ, which indicated that the addition of PEPSQ retarded the thermal decomposition of EP. The Flynn–Wall–Ozawa method further revealed that PEPSQ significantly increased the activation energy of the whole EP thermal decomposition, especially in the final stage of the thermal decomposition process, which is attributed to the PEPSQ stabilizing the char layer and improving the flame retardancy of EP.     

Synergistic Effect of Polyhedral Oligomeric Silsesquioxane and Multiwalled Carbon Nanotubes on the Flame Retardancy and the Mechanical and Thermal Properties of Epoxy Resin

A novel polyhedral oligomeric silsesquioxane containing phosphorus and boron (PB-POSS) was synthesized. The resulting PB-POSS and multiwalled carbon nanotubes (MWCNTs) were incorporated into an epoxy resin (EP) to prepare PB-POSS/MWCNTs/EP composites through a solution mixing method. The synergistic effect of MWCNTs and PB-POSS on the thermal and mechanical properties and the flame retardancy of these flame retardant composites were studied. The experimental results showed that the introduction of PB-POSS or MWCNTs further improved the LOI values of the epoxy resin, and the highest LOI value (32.8%) was obtained for the formulation containing 14.6 wt% PB-POSS and 0.4 wt% MWCNTs. In addition, the incorporation of both PB-POSS and MWCNTs significantly improved the thermal and mechanical properties of the composites. The mechanical properties of composites containing 14.7 wt% PB-POSS and 0.3 wt% MWCNTs reached the maximum. The impact strength and flexural strength increased by 42% and 7%, respectively, compared to the neat epoxy resin. Thus, a combination of PB-POSS and MWCNTs in the appropriate ratio could effectively enhance the thermal and mechanical properties and the flame retardancy of the epoxy resin matrix.     

Metal-Filled Epoxy Composites: Mechanical Properties and Electrical/Thermal Conductivity

Abstract

The mechanical properties and the electrical and thermal conductivity of composites based on an epoxy polymer (EP) filled with dispersed copper (Cu) and nickel (Ni) were studied. It was shown that the electrical conductivity of the composites demonstrated percolation behavior with the values of the percolation threshold being 9.9 and 4.0?vol.% for the EP-Cu and EP-Ni composites, respectively. Using the Lichtenecker model, the thermal conductivity of the dispersed metal phase in the composites, λ_f, was estimated as being 35?W/mK for Cu powder and 13?W/mK for Ni powder. It was shown that introduction of the filler in EP led to a decrease in the intensity of the mechanical loss tangent (tan δ) peak that was caused by the existence of an immobilized polymer layer around the filler particles which did not contribute to mechanical losses. Using several models the thickness of this layer, ΔR, was estimated. The concept of an “excluded volume” of the polymer, V_ex, i.e. the volume of the immobilized polymer layer, which does not depend on the particle size and is determined solely by the value of the interaction parameter, B, was proposed.     

Influence of Curing Pressure on the Structure and Properties of Epoxy Adhesive Films

The effects of different curing pressures on the structure and properties of bisphenol A type epoxy adhesive film (METLBOND 1515-4, Cytec Industries Inc. Germany) were investigated by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), dynamic mechanical analysis (DMA), nano-indentation analysis, and tensile testing. When the curing pressure was increased from 0?MPa to 0.5?MPa FTIR showed that more rigid carbonyl groups were found in the polymers. In addition, the microscopic and macroscopic mechanical properties of the cured adhesive films were improved. Nano-indentation analysis showed that the elastic modulus of the cured product increased significantly, from 2.92?GPa to 3.49?GPa. However, the tensile tests showed that the breaking-elongation increased only slightly, from 3.10% to 3.73%, when the curing pressure was increased from 0?MPa to 0.5?MPa. DMA results showed that the crosslinking densities of the cured epoxy films were improved by the increased curing pressure. These results indicated that a higher modulus of the cured product could be gained by increasing the curing pressure appropriately.     

Modification of Epoxy Resin with Cycloaliphatic-Epoxy Oligosiloxane for Light-Emitting Diode (LED) Encapsulation Application

A novel cycloaliphatic-epoxy oligosiloxane (EHDM) was incorporated into 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (ERL-4221) for use as a light-emitting diode (LED) encapsulant. EHDM, with reactable epoxy groups and flexible Si-O-Si chains, was obtained by the hydrolytic condensation reaction between 2-(3,4-epoxycyclo-hexyl)ethyl-trimethoxysilane (EHETMS) and dimethyldiethoxylsilane (DMDES). The results of Fourier transform infrared spectroscopy, ²⁹Si nuclear magnetic resonance, and gel permeation chromatography indicated that EHDM had a narrow molecular weight distribution and high epoxy graft degree. The thermal and mechanical properties, morphologies, and light transmittance of the cured neat epoxy resin and EHDM-modified epoxy were investigated by differential scanning calorimetry, thermogravimetric analysis, tensile and impact testing, scanning electron microscopy, and ultraviolet-visible spectrophotometry. The experimental results demonstrated that the cured EHDM-10 hybrimer with 10 pph of EHDM relative to ERL-4221 maintained the neat ERL-4221 epoxy transmittance of 85% at 450 nm. With respect to the corresponding properties of the neat epoxy resin, EHDM-10 hybrimer possessed a higher glass transition temperature, better thermal stability, better fracture toughness, and lower water absorption ratio, indicating EHDM effectively improved the properties of ERL-4221 for LED packaging applications.     

Surface Modification of Para-Aramid Fiber by Direct Fluorination and its Effect on the Interface of Aramid/Epoxy Composites

Surface modification of a para-aramid fiber (DAFIII) was performed by direct fluorination. The properties of treated and untreated fibers were characterized and compared in detail by mechanical testing, Fourier transform infrared (FTIR) spectroscopy characterization, X-ray photoelectron spectroscopy (XPS) analysis and static contact angle measurements. The results showed that little damage of the fiber occurred after direct fluorine treatment, and the content of polar groups on the fibers surfaces were increased significantly, which resulted in a lower value of contact angle. The interlaminar shear strength (ILSS) of DAFIII fiber/epoxy composites and the tensile strength of NOL-ring specimens increased by 33% and 12%, increasing to 56.2 MPa and 2340 MPa, respectively, which indicated that the interfacial adhesion between the matrix and the aramid fiber was improved significantly by the fluorination treatment. Further tests showed that the durability of the direct fluorination treatment on the aramid fiber was also satisfactory.     

Phase Structure,Thermal, and Mechanical Properties of Polypropylene/Hollow Glass Microsphere Composites Modified with Maleated Poly(ethylene-octene)

Maleated poly(ethylene-octene) (POE-g-MAH), as a compatilizer and toughener, was incorporated in polypropylene/hollow glass microspheres (PP/HGM) binary composites, and the phase structure and thermal and mechanical properties of these composites were investigated. Scanning electron microscopy analysis indicated that the phase structure of ternary composites could be controlled by POE-g-MAH and the surface treatment of HGM. Fourier transform infrared spectroscopy revealed that there was an amidation reaction between the treated HGM and POE-g-MAH during melt compounding. Differential scanning calorimetry suggested that the crystallization and melting behaviors of ternary composites were influenced by phase structure. Evaluation of mechanical properties showed that the amide linkage between the treated HGM and POE-g-MAH was favorable for improving the properties of ternary composites.     

Kinetic Evaluation of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide as a Flame Retardant for Epoxy Resins

Abstract

In this investigation the flame-retardant effect of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) on an epoxy resin (EP) was studied. The results showed that the peak of heat release rate (PHRR) and total heat release (THR) of EP/DOPO (FREP) with 5phr DOPO during cone calorimeter measurements were only 67.4% and 75.3% of those of pure EP, respectively. The thermal degradation behavior of FREP was analyzed by the Kissinger and Flynn-Wall-Ozawa methods, both of which indicated that the activation energy of the FREP thermal degradation was lower than that of pure EP. This was attributed to the addition of DOPO into the resin, which promoted the thermal degradation of the EP composite.     

Effect of Silica and Silicone Oil on the Mechanical and Thermal Properties of Silicone Rubber

The effect of three types of silicas with varied loading and the loading of hydroxyl terminated silicone oil on the mechanical and thermal properties of silicone rubbers (SRs) were investigated. Mechanical properties were affected by the silica loading because of the interaction between fillers and polymer and the filler dispersion. Fumed silica filled SRs showed higher tanδ, tensile strength, and elongation at break compared to those containing two types of precipitated silicas. With increasing silicone oil loading, the tensile strength, tear strength, hardness, and tanδ of SRs first increased and then decreased.     

高压热处理对铝青铜热物理性能的影响

在5 GPa压力下对铝青铜进行750℃、保温15 min的高压热处理,对高压热处理前后铝青铜的电导率以及25～600℃温度范围内的热扩散系数、热容和热导率进行测试,结合显微组织的观察结果,探讨了高压热处理对铝青铜热物理性能的影响。研究表明:高压热处理能增大铝青铜的热扩散系数,减小热容;对热导率而言,温度低于400℃时高压热处理能增大铝青铜的热导率,而温度高于400℃时高压热处理能减小铝青铜的热导率。分析认为,产生变化的主要原因是高压热处理使铝青铜的微观组织发生了变化。     

Physical and Thermal Properties of High-Density Polyethylene Film Modified with Polypropylene and Linear Low-Density Polyethylene

Abstract

In view of the toughness and processing difficulty of high-density polyethylene (HDPE) film, the HDPE was modified by polypropylene (PP) and linear low density polyethylene (LLDPE), and the melt index, haze, dart impact strength, elongation at break were characterized. In addition the infrared spectra (IR), scanning electron microscopy (SEM), infrared image analysis, and differential scanning calorimetry (DSC) data were obtained. The results showed that the toughening effect of the 10%PP/30%LLDPE/60%HDPE composition was the best; the haze was reduced 6% and its dart impact strength and elongation at break were increased by 27.3% and 47%, respectively, relative to the pure HDPE. The blend of 10%PP/30%LLDPE/60%HDPE had compatibility. The melting point of the 10%PP/30%LLDPE/60%HDPE blend film increased by 5?°C compared with the pure HDPE film, with the results indicating the application fields of HDPE film could be widened.     

Preparation and Characterization of Two Types of Cyanate Ester-epoxy Resin Interpenetrating Network Matrix/Butadiene-acrylonitrile Rubber Composites

Two types of butadiene-acrylonitrile rubbers (i.e., carboxyl randomized butadiene-acrylonitrile rubber (CRBN) and hydroxyl terminated butadiene-acrylonitrile rubber (HTBN)) have been used for modifying an interpenetrating network of cyanate ester (CE)/epoxy resin (EP) (70/30). The toughness of the matrix can be improved effectively with addition of rubbers. The values of impact strength (11.6 KJ/m²) show a maximum for the CE/EP/HTBN (70/30/8) blend. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results show that CRBN and HTBN have a different dispersion state in the CE/EP matrix. CRBN aggregates to form regular spheres with a size of about 1 μm. HTBN disperse homogeneously with its size of the nano-level (about 10 nm). Fourier transform infrared spectrum (FTIR) and differential scanning calorimetric (DSC) analysis shows that the CRBN has higher reactivity than HTBN. The thermal gravimetric analysis (TGA) results shows that T ₁₀ (temperature of 10% weight loss) of the CE/EP system decreases with the addition of rubbers. For the CE/EP/CRBN system, both T ₃₀ (temperature of 30% weight loss) and T ₅₀ (temperature of 50% weight loss) are lower than neat CE/EP. However, for the CE/EP/HTBN system, both T ₃₀ and T ₅₀ are near to neat CE/EP. Different reactivity and compatibility between the rubbers and CE/EP matrix is the main determining factor for the thermal stability of the blends.     

Thermal Properties of Fe-octacarboxyl Acid Phthalocyanine/Polyurethane Blends

The thermal stability of PU has been a critical factor to influence its applications as engineering materials. In this paper, the thermal properties of Fe-octacarboxyl acid phthalocyanine (Fe-OCAP)/polyurethane (PU) blends were investigated. The glass transition temperatures (T_g) of Fe-OCAP/PU blends were analyzed by differential scanning calorimetry (DSC). The results showed that with increasing Fe-OCAP content up to 10% T_g of the samples decreased. Thermal stability of the samples was studied by thermogravimetric analysis (TGA). The decrease of the degradation rate of the samples with increasing Fe-OCAP content indicated an improvement of thermal stability for the modified samples. The activation energy of thermal degradation was calculated by the Freeman and Carroll method. The results showed that the activation energy increased with increasing Fe-OCAP content, which also indicated the improved thermal stability obtained in the modified samples. The thermal properties of the samples were influenced by the incorporation of Fe-OCAP.     

Mechanical and Thermal Properties of Polypropylene/Silica Aerogel Composites

Polypropylene (PP) composites including various amounts of silica aerogel (SA) microparticles were prepared by melt mixing in an internal mixer. The morphology and microstructure of the prepared composites were investigated by scanning electron microscopy (SEM). Mechanical properties of the samples, including elastic modulus, tensile stress, elongation and stress at break, were measured by tensile tests. In addition, the other mechanical features, including Izod impact strength, hardness and wear resistance, were evaluated and then related to the structure of the PP/SA composites. Furthermore, the thermal characteristics of the composites, such as heat deflection temperature and thermal stability, were studied by thermal gravimetric analysis (TGA). The SEM photographs indicated the satisfactory SA particles dispersion for the compositions of 1% and 3% but agglomeration of the aerogels at higher SA contents. Since the composites became stiffer, the impact and tensile strength decreased. The addition of the SA to the PP matrix yielded harder samples with lower weight loss and coefficients of friction in wear tests. The TGA evaluations confirmed that the presence of SA promoted and upgraded the thermal stability and heat deflection temperature of PP. The thermal results proved the superior potential of PP as an insulator when the SA particles were added.     

对爱因斯坦模型的修正及考虑热效应的三个通用状态方程

 对固体考虑热效应的爱因斯坦模型进行了修正。指出考虑热效应的通用状态方程中不应该包含零点振动项，方程参数不应该直接取为参考温度下的实验值V_R，B_R，B′_R和γ^G_R，而应该取为零温下的数值V₀，B₀，B′₀和γ^G₀；提出了一种从V_R，B_R，B′_R和γ^G_R求解V₀，B₀，B′₀和γ^G₀的方法。将提出的方法应用于三个典型的通用状态方程，包括Baonza、mMNH和Vinet方程。数值结果表明，利用相同的实验参数对三个方程解出的参数，以及预测的零压和低压下的热物理性质差异很小，而且都与实验数据符合很好。这些结果表明，在零压和低压下预测热物理性质的精确度不足以用来判断各种通用状态方程的适用性。