Thermal properties and moisture absorption of nanofillers‐filled epoxy composite thin film for electronic application

This current study aimed to enhance the thermal conductivity of thin film composites without compromising other polymer qualities. The effect of adding high thermal conductivity nanoparticles on the thermal properties and moisture absorption of thin film epoxy composites was investigated. Three types of fillers in nanosize with high thermal conductivity properties, boron nitride (BN), synthetic diamond (SD), and silicon nitride (Si₃N₄) were studied. SN was later used as an abbreviation for Si₃N₄. The contents of fillers varied between 0 and 2 vol.%. An epoxy nanocomposite solution filled with high thermal conductivity fillers was spun at 1500–2000 rpm to produce thin film 40–60 µm thick. The effects of the fillers on thermal properties and moisture absorption were studied. The addition of 2 vol.% SD produced the largest improvement with 78% increment in thermal conductivity compared with the unfilled epoxy. SD‐filled epoxy thin film also showed good thermal stability with the lowest coefficients of thermal expansion, 19 and 124 ppm, before and after T_g, respectively, which are much lower compared with SN‐filled and BN‐filled epoxy thin film composites. However the SD‐filled epoxy film has its drawback as it absorbs more moisture compared with BN‐filled and SN‐filled epoxy film. Copyright © 2012 John Wiley & Sons, Ltd.     

Thermal and mechanical properties of particulate fillers filled epoxy composites for electronic packaging application

Epoxy composites containing particulate fillers‐fused silica, glass powder, and mineral silica were investigated to be used as substrate materials in electronic packaging application. The content of fillers were varied between 0 and 40 vol%. The effects of the fillers on the thermal properties—thermal stability, thermal expansion and dynamic mechanical properties of the epoxy composites were studied, and it was found that fused silica, glass powder, and mineral silica increase the thermal stability and dynamic thermal mechanical properties and reduce the coefficient of thermal expansion (CTE). The lowest CTE value was observed at a fused silica content of 40 vol% for the epoxy composites, which was traced to the effect of its nature of low intrinsic CTE value of the fillers. The mechanical properties of the epoxy composites were determined in both flexural and single‐edge notch (SEN‐T) fracture toughness properties. Highest flexural strength, stiffness, and toughness values were observed at fillers content of 40 vol% for all the filled epoxy composites. Scanning electron microscopy (SEM) micrograph showed poor filler–matrix interaction in glass powder filled epoxy composites at 40 vol%. Copyright © 2007 John Wiley & Sons, Ltd.     

Study of the fire resistant behavior of unfilled and carbon nanofibers reinforced polybenzimidazole coating for structural applications

With increasing interest in epoxy‐based carbon fiber composites for structural applications, it is important to improve the fire resistant properties of these materials. The fire resistant performance of these materials can be improved either by using high performance epoxy resin for manufacturing carbon fiber composite or by protecting the previously used epoxy‐based composite with some fire resistant coating. In this context, work is carried out to evaluate the fire resistance performance of recently emerged high performance polybenzimidazole (PBI) when used as a coating material. Furthermore, the effect of carbon nanofibers (CNFs) on fire resistant properties of inherently flame retardant PBI coating was studied. Thermogravimetric analysis of carbon/epoxy composite, unfilled PBI and nano‐filled PBI shows that the carbon/epoxy composite maintained its thermal stability up to a temperature of 400°C and afterwards showed a large decrease in mass, while both unfilled PBI and nano‐filled PBI have shown thermal stability up to a temperature of 575°C corresponding to only 11% weight loss. Cone calorimeter test results show that unfilled PBI coating did not improve the fire retardant performance of carbon/epoxy composite. Conversely, nano‐filled PBI coating has shown a significant improvement in fire retardant performance of the carbon/epoxy composite in terms of increased ignition time, reduced average and peak heat release rate and reduced smoke and carbon monoxide emission. These results indicate that addition of carbon nanofibers to inherently flame retardant coating can significantly be helpful for improving the fire resistance performance of composite materials even with low coating thickness. Copyright © 2013 John Wiley & Sons, Ltd.     

高性能环氧树脂/碳纳米管复合物的热分析研究

用差示扫描量热仪(DSC)、热失重分析仪(TGA)和动态力学热分析仪(DMTA)研究了多壁碳纳米管(MWNTs)/高性能4,4′-二氨基二苯甲烷四缩水甘油环氧树脂(TGDDM)/4,4′-二氨基二苯基砜(DDS)复合物的热性能.Kissinger和Flynn-Wall-Ozawa的非等温固化动力学研究发现,随着MWNTs含量的增加,复合物固化反应的活化能先减小后增大.TGA研究表明,MWNTs的添加对环氧树脂热稳定性影响很小.碳纳米管填充到TGDDM/DDS体系后,复合物的储存模量随着MWNTs含量的增加而增大,而玻璃化温度却随之减小.     

Thermal degradation of epoxy composites based on thermally expanded graphite and multiwalled carbon nanotubes

Thermal degradation of epoxy composites filled with various carbon materials (thermally expanded graphite, multiwalled carbon nanotubes) was studied. The dynamics of the thermal degradation of epoxy composites was evaluated by thermogravimetric analysis in the temperature range of 55–700°С (heating rate 10 deg min^–1) in an oxidizing medium. Carbon fillers were studied by scanning electron microscopy, transmission electron microscopy, and low-temperature nitrogen adsorption. The influence of the composite preparation procedure on its thermal stability was determined. The type of filler significantly influences the thermal oxidative degradation of the composites.     

高性能可回收环氧树脂及其复合材料的制备与性能研究

采用戊二酸酐为固化剂,乙酰丙酮锌为催化剂制备了一种综合性能优异的高性能可回收环氧树脂.系统研究了固化剂及催化剂含量对树脂结构、热学及动态性能的影响,实现了树脂组成的优化设计.基于酯交换反应的热可逆性,制备的vitrimer树脂通过物理热压方法可实现良好回收,力学强度保持率可达80%.采用RTM工艺制备的碳纤维织物增强vitrimer树脂复合材料表现出与传统热固性树脂基复合材料相当的力学性能,并且通过醇类溶剂热降解树脂的方法,可实现复合材料中碳纤维的高效无损回收,回收率近100%.     

A Study on the Ballistic Performance of Composites

The mechanical behaviour and ballistic performance of carbon, glass (E and S type), aramid and polyethylene fabric reinforced composites with different epoxy resins were studied. The specimens – produced by hand lay-up method – were characterized by low velocity (Charpy and drop-weight tests) and high velocity (two different calibre ballistic) impact tests. The energy absorption capacity of the composites was found to be strongly affected by the material properties of the reinforcing fiber, by the type of fabric structure and by the elasticity of resin.     

Influence of silica fillers during the electron irradiation of DGEBA/TETA epoxy resins, part III: Solid-state NMR investigations

The influence of silica fillers on chemical modifications of diglycidyl ether of bisphenol A/triethylene tetramine (DGEBA/TETA) epoxy resins induced by electron beam irradiation has been studied by ¹³C CP-MAS (Cross Polarisation and Magic Angle Spinning) NMR. Four kinds of silica filler were investigated: a pure micrometric silica, a treated micrometric silica, a pure nanometric silica and a treated nanometric silica. On the unirradiated epoxy resins, the magnetization transfer curves reveal structural differences due to the kind of silica fillers. A decrease of the epoxy network rigidity in the presence of nanometric silica fillers is shown. During irradiation, the formation of phenolic ends and enamine functions is confirmed. The slowing of the magnetization transfer of the pure and treated micrometric silica filled epoxy resin reveals an important decrease of the rigidity of these resins. On the pure and treated nanometric silica filled epoxy resins, reactions of the reactive species created by the irradiation in the epoxy resin and the silica particles surface are shown.     

The thermal and dielectric properties of high performance cyanate ester resins/microcapsules composites

Novel high performance bisphenol A dicyanate ester (BADCy) resins/poly(urea-formaldehyde) microcapsules filled with epoxy resins (MCEs) composites have been prepared. The effects of different contents of MCEs on the thermal and dielectric properties of cured BADCy were investigated using dynamic mechanical analyzer (DMA), thermalgravimetric analyzer (TGA) and broadband dielectric analyzer. The dielectric properties of BADCy/MCEs treated in hot water and hot air were also discussed. The morphologies of BADCy/MCEs composites were characterized by scanning electron microscopy (SEM). Results indicate that the appropriate content of MCEs can improve or maintain the thermal stability, the low dielectric constant and dielectric loss of cured BADCy mainly owing to higher conversion of cyanate ester (-OCN) groups. After aged in hot water and hot air, respectively, BADCy/MCEs composites with small content of MCEs can retain the low dielectric constant and dielectric loss.     

Epoxy Composites Modified with Finely Dispersed Fillers

The thermal stability and mechanical strength of composites based on ED-20 epoxy oligomer cured with isomethyltetrahydrophthalic and methylendic anhydrides was studied as influenced by the nature and properties of finely dispersed inorganic fillers, such as carbon black, aluminum oxide, and silica nanoparticles.     

Effect of nano/micro‐mixed ceramic fillers on the dielectric and thermal properties of epoxy polymer composites

Nano/micro ceramic‐filled epoxy composite materials have been processed with various percentage additions of SiO₂, Al₂O₃ ceramic fillers as reinforcements selected from the nano and micro origin sources. Different types of filler combinations, viz. only nano, only micro, nano/micro, and micro/micro particles, were designed to investigate their influence on the thermal expansion, thermal conductivity, and dielectric properties of epoxy polymers. Thermal expansion studies were conducted using thermomechanical analysis that revealed a two‐step expansion pattern consecutively before and after vitreous transition temperatures. The presence of micro fillers have shown vitreous transition temperature in the range 70–80°C compared with that of nano structured composites in which the same was observed as ~90°C. Similarly, the bulk thermal conductivity is found to increase with increasing percentage of micron‐size Al₂O₃. It was established that the addition of micro fillers lead to epoxy composite materials that exhibited lower thermal expansion and higher thermal conductivity compared with nano fillers. Moreover, nano fillers have a significantly decisive role in having low bulk dielectric permittivity. In this study, epoxy composites with a thermal expansion coefficient of 2.5 × 10^?5/K, thermal conductivity of 1.18 W/m · K and dielectric permittivity in the range 4–5 at 1 kHz have been obtained. The study confirms that although the micro fillers seem to exhibit good thermal conductivity and low expansion coefficient, the nano‐size ceramic fillers are candidate as cofillers for low dielectric permittivity. However, a suitable proportion of nano/micro‐mixed fillers is necessary for achieving epoxy composites with promising thermal conductivity, controlled coefficient of thermal expansion and dielectric permittivity. Copyright © 2013 John Wiley & Sons, Ltd.     

Thermally conductive and electrically insulative nanocomposites based on hyperbranched epoxy and nano‐Al2O3 particles modified epoxy resin

Novel epoxy nanocomposites based on a diglycidyl ether of bisphenol A (DGEBA) epoxy, an epoxy functionalized hyperbranched polymer (HTTE) and nano‐Al₂O₃ were synthesized with the aim of determining the effect of the nano‐Al₂O₃ particles and HTTE on the structure and properties of epoxy nanocomposites. The mechanical properties, thermal conductivity, bulk resistivity, and thermal stability of the nano‐Al₂O₃/HTTE/DGEBA ternary composites were evaluated and compared with the corresponding matrix. The improvement in impact properties of these nanocomposites was explained in terms of fracture surface analysis by SEM. The results indicate that the incorporation of nanoparticles and hyperbranched epoxy effectively improved the toughness of epoxy composites without sacrificing thermal conductivity and bulk resistivity compared to the neat epoxy and Al₂O₃/DGEBA, obtaining a well dispersion of nanoparticles in epoxy matrix and solving the drawbacks for single fillers filled epoxy nanocomposite. Copyright © 2010 John Wiley & Sons, Ltd.     

Ball milling: An effective technique for the preparation of exfoliated clay filled unsaturated polyester toughened epoxy nanocomposite

This paper investigates the possibility of improving the mechanical and thermal properties of epoxy and unsaturated polyester toughened epoxy resins through the dispersion of octadecyl ammonium ion-exchanged montmorillonite (organoclay) through exfoliated mechanism. The nanocomposites prepared are characterized for their structural change and studied for their crystallite size, mechanical, thermal and water absorption (hydrophilicity) properties. The mechanical data indicates significant improvement in the flexural and tensile properties over the neat epoxy and UP-epoxy matrix according to the percentage content of organoclay. The thermal behavior too shows noticeable enhancement in glass transition temperature T _g and high thermal stability. Hydrophilicity of all the composites decreases irrespective of the concentration of organoclay on the epoxy and UP-epoxy matrices. The homogeneous morphology of epoxy and UP toughened epoxy nanocomposite hybrid systems is ascertained using scanning electron microscope (SEM). X-ray results point out that the cetyl ammonium modified clay filled composites exhibited the exfoliated structure.     

Novel polyphenylene oxide microcapsules filled with epoxy resins

Novel polyphenylene oxide (PPO) microcapsules filled with epoxy resins (PPOMCs) were synthesized by in situ polymerization technology with 2, 6‐dimethy phenol as shell materials and diglycidyl ether of bisphenol A epoxy resins as core materials. The structures and morphologies of PPOMCs were characterized using Fourier‐transform infrared spectroscopy, micro‐confocal Raman microscope, laser scanning confocal microscopy, scanning electron microscopy and optical microscopy, respectively. The thermal properties of PPOMCs were investigated using differential scanning calorimetry and thermogravimetric analysis. The influences of different processing parameters such as the weight ratio of shell material to core material, kind of surfactant and reaction temperature on the morphologies and sizes of PPOMCs were investigated. Preliminary investigation on application of PPOMCs to thermosetting resins 4,4′‐bismaleimidodiphenylmethane/O,O′‐diallylbisphenol A (BMI/BA) system was conducted. Results indicate that PPOMCs can be synthesized successfully. The sizes and surface morphologies of PPOMCs may be significantly affected by different processing parameters. PPOMCs can be well prepared at about 30°C, and they depend strongly on the kind of surfactant and the weight ratio of shell material to core material. PPOMCs basically exhibit high thermal stability when the temperature is below 258°C. The addition of PPOMCs can improve the mechanical properties and maintain the thermal properties of BMI/BA system. The released core materials from PPOMCs may repair the matrix cracks through the polymerization of epoxy resins initiated by curing agent. Copyright © 2012 John Wiley & Sons, Ltd.     

Effect of Different Hybrid Method on Properties of Carbon Nanotubes/Dolomite Hybrid Filled Phenolic Composites

Hybridization of multi wall carbon nanotubes (MWCNTs) with other filler in polymer matrix composites (PMC) is one of the techniques for combining different properties of fillers for making more unique composites. In this work, the hybrid filler (CNTs–dolomite) are prepared via chemical vapour deposition (CVD hybrid) and the milling method (physically hybrid). The effect of different hybrid method on properties of multi wall carbon nanotubes/dolomite hybrid filled phenolic composites were studied. Phenolic/CVD hybrid composites and phenolic/physically hybrid composites with different filler loadings were prepared using hot mounting press. The prepared samples were characterized for their thermal conductivity and hardness. The thermal conductivity was measured using the Transient Plane Source (TPS) method, using a Hot-DiskTM Thermal Constant Analyzer and the hardness was measured using Rockwell micro-hardness. The results showed that at 5% filler loading, the phenolic/CVD hybrid composites were capable of increasing the thermal conductivity and micro-hardness up to 7.22% and 101.6% respectively compared to pure phenolic.     

Experimental investigation of thermal properties and fire behavior of carbon/epoxy laminate and its foam core sandwich composite

According to structural characteristics, composites are classified as laminated structure and sandwich structure. Carbon/epoxy laminate and foam core sandwich composite are the most commonly used laminate and sandwich structure material in the aircraft industry. The flammability of epoxy resins and foam core material is an inherent hazard. Many previous studies focused primarily on their mechanical properties, while the studies on the thermal and fire properties of carbon/epoxy laminate and its foam core sandwich composite have rarely conducted. Therefore, to characterize their thermal and fire properties, a comprehensive experimental investigation and theoretical analysis were carried out in this work using thermogravimetric analysis, cone calorimeter, vertical/horizontal burning tests, limiting oxygen index and scanning electron microscope tests. Several typical characteristic parameters were obtained and analyzed, such as pyrolysis temperature, heat release rate, mass loss, flaming spread rate and limiting oxygen index. These experimental data coupled with theoretical analysis can provide support for fire risk assessment and fire protection design in aircrafts. The carbon/epoxy laminate and foam core sandwich composite are both characterized as the thermally thick materials. The ignition models and mass loss rate models were obtained. Foam core material negatively affects most of the thermal and fire properties of sandwich composite, but the foam core sandwich composite has self-extinguishing behavior during horizontal burning tests, whose LOI is higher than that of carbon/epoxy laminate. Thus, an important conclusion was reached that the ignition position and flame spread direction have critical effect on the fire behavior of foam core material.

     

钛酸钾晶须填充环氧树脂复合材料的摩擦磨损特性

以提高环氧树脂的摩擦磨损性能为目的,研究了钛酸钾晶须(PTW)填充环氧树脂复合材料的滑动干摩擦磨损特性,着重探讨PTW含量、摩擦条件等对复合材料摩擦性能的影响.通过对复合材料磨损表面的形貌分析以及复合材料表面硬度的测定,探讨了复合材料的磨损机理.结果表明:PTW能明显提高环氧树脂耐磨性并降低其摩擦系数,w(PTW)=0.08的环氧树脂复合材料的耐磨性比纯环氧树脂提高近10倍,摩擦系数降低35%.     

Electro-conductive resins filled with graphite for casting applications

Electro-conductive resins, convenient for casting and coating applications were investigated in this paper.Electrical conductivity of epoxy and polyurethane resins, filled with two different grades of synthetic graphite (different average size) was studied. It was found that all the investigated composites became electro-conductive when filled with 22-vol% of the filler.The impact strength of epoxy and polyurethane resins filled with graphite was also investigated. A decrease in impact strength with an increase in filler content was observed in all cases. The highest values of impact strength were found for polyurethane/graphite KS 6 composites.The strength of adhesion of the filled resins to aluminum was also determined. A decrease in the strength of adhesive joints to aluminum foils with an increase in filler content was observed in all cases. The strongest adhesive joints were found for the epoxy/graphite KS 6 composites.     

Oligo-fluoropolymer Modified Cycloaliphatic Epoxy Resins with Excellent Compatibility,Waterproof and Mechanical Properties for LED Encapsulation

An oligo-fluoropolymer(PFM) with functional cycloaliphatic epoxy and fluorinated groups was obtained via free radical polymerization and applied to the modification of cycloaliphatic epoxy resins(CE). The chemical structure of PFM was characterized by Fourier transform infrared(FTIR) spectroscopy, gel permeation chromatography(GPC) and nuclear magnetic resonance(NMR) spectroscopy, and the effects of different PFM concentrations(0.5%—6%, mass fraction) on the thermal resistance, mechanical properties, surface dewettability, light transmission, refractive index and various cured polymer properties were studied in detail. The DSC and TGA results demonstrate that the modified epoxy resins possess a higher thermal resistance than the neat epoxy resin. The improvements in the surface dewettability and water resistance are caused by the high crosslinking density and the enrichment of the oligo-fluorinated random copolymers dispersed in the matrix. The fracture surface morphologies of the thermosets were investigated by scanning electron microscopy(SEM) and transmission electron microscopy(TEM). It was observed that the optical transmittance of the composites was maintained even though microphase separation occurred during the curing process. With respect to the corresponding properties of the neat epoxy resins, the 2 phr(parts per hundreds of resin) PFM thermoset exhibited relatively better comprehensive properties, making the cured material a good candidate for light-emitting diode(LED) encapsulation.     

Nano- and micro-structured random copolymer modified cycloaliphatic epoxy resins for use as light-emitting diode encapsulation

Poly(2,2,3,4,4,4-Hexafluorobutylmethacrylate–random–glycidolmethacrylate) random copolymer (P(HFBMA-r-GMA)) was synthesized via free radical polymerization. The novel reactive random copolymer was incorporated to modify cycloaliphatic epoxy resins and obtain the nano- or micro- structured composites. The chemical structures of P(HFBMA-r-GMA) were confirmed by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). The morphology and light transmittance of the cured epoxy resins were observed by scanning electron microscopy (SEM), transmission electron microscope (TEM) and ultraviolet-visible spectrophotometry (UV-vis), respectively. It is indicated that the optical transmittance of composites were basically kept although the microphase separation occurred in the curing process, which has a profound influence on the mechanical properties and refractive indexes. The thermal properties, surface dewettability and water absorbency of the cured epoxy resins were examined by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), contact angle measurement and immersion test respectively. The experimental results revealed that the values of glass transition temperatures (Tg), surface dewettability and water resistance were effectively improved by the high cross-linking density and the enrichment of the fluorinated random copolymer dispersing in the composites. With respect to the corresponding properties of the neat epoxy resin, P (HFBMA-r-GMA)-0.25 hybrimer embraced the relatively good comprehensive properties, making the modified epoxy resins as good candidates for LED encapsulation.