氧化石墨烯/呋喃树脂复合材料的制备及其性能

用改良的Hummers法制备出氧化石墨烯(GO),再通过溶液共混,逐步升温固化制备得到GO/呋喃树脂复合材料。利用FTIR、XRD和SEM对GO/呋喃树脂复合材料的微观结构和形貌进行表征,同时对其黏度、玻璃化转变温度、热分解温度、残炭率及硬度进行了检测。结果表明,GO较均匀地分散于呋喃树脂基体中,且两者界面相容性较好。GO/呋喃树脂复合材料的热性能和力学性能相对于纯树脂都有一定的提高。与纯呋喃树脂相比,当GO的添加量为0.3wt%时,GO/呋喃树脂复合材料的玻璃化转变温度提高了36℃,热失重5%时的温度提高了16℃;当GO的添加量为0.1wt%时,GO/呋喃树脂复合材料的残炭率从50.7%提高到53.9%,邵氏硬度从90提高到97。     

Interfacial,fire retardancy,and thermal stability evaluation of graphite oxide (GO)-phenolic composites with different GO particle sizes

Mechanical and thermal properties of graphite oxide (GO)-phenolic composites were evaluated for different sizes of GO. Tensile tests on the composites with larger sizes of GO particles typically exhibited better mechanical properties. After ageing tests at 200 °C a decline in the mechanical properties of GO-phenolic composites was observed but this decline was less than that for neat phenolic resin. This was attributed to the GO absorbing thermal energy and thereby reducing damage to the molecular chain in the resin. The ageing tests, also suggested that the wettability of specimens improved with the addition of GO, which might be attributed to microvoid formation on specimen’s surface during the elapsed time at the elevated temperature. The chemical structures of neat phenolic resin was relatively easily broken-up by thermal damage, whereas GO-phenolic composites exhibited better thermal stability in both thermal analysis and flame retardant testing. The GO particles exhibited reinforcing effects that served to protect chemical bonding in the phenolic resin. It appears, therefore, that GO composites may be good candidates for us as heat and flame resisting materials, for various applications.     

Enhancement of ablative and interfacial bonding properties of EPDM composites by incorporating epoxy phenolic resin

Effects of epoxy phenolic resin (EPR) on ablative and interfacial bonding properties of EPDM composites were evaluated. Ablative properties of EPDM composites were enhanced by two folds with incorporating 10 phr EPR. This significant enhancement was attributed to positive effect of EPR on thermal stability and thermal insulating properties of EPDM composites as well as formation of compact char layer onto composites. Furthermore, interfacial shear strength of EPDM composites with carbon fiber/epoxy (CF/EP) composites was increased by 55.6% with incorporating 10 phr EPR, due to interfacial chemical reaction of epoxide groups of EPR molecule from EPDM composites with amine group of hardener from CF/EP composites.     

Enhanced thermal resistance of GO/C/phenolic nanocomposite by introducing ZrB2 nanoparticles

The effectiveness of different additives on improving the thermal stabilities of phenolic composite was investigated by incorporating of graphene oxide sheets (GO) into the carbon/phenolic (PR), and then the ZrB₂ nanoparticles into the GO/PR composite. The GOs dissipate heat throughout the sample thereby reducing thermal gradients and the intensity of heating at the surface exposed to flame. Also, at higher exposure time, the resistance to oxidation of the nanocomposite begins taking advantage of the ongoing formation of an oxide coating layer (ZrO₂) on the exposed face. This protected the underlying unoxidized material from the structural damage caused by thermal shocks and high shear forces.     

Preparation of thermally reduced graphene oxide and the influence of its reduction temperature on the thermal,mechanical, flame retardant performances of PS nanocomposites

In this article, we investigated the influence of thermally reduced graphene oxides (TGOs) at different reduction temperatures on the thermal, mechanical and flame retardant performances of polystyrene (PS). The results indicated that disordered expanded layer structure can be obtained as the reduction temperature increases from 200 to 500 and 800 °C (the resulted composites are named as PS/TGO2, PS/TGO5 and PS/GTO8, respectively), which could lead to better dispersion of TGO sheets in PS matrix. Dynamic mechanical thermal analysis showed that both the storage modulus and T_g of PS/TGO5 and PS/TGO8 nanocomposites are significantly improved compared with that of neat PS. Noticeable improvement in flame retardant performance were achieved with the addition of TGO5 and TGO8, particularly TGO8, due to the removal of the functional oxygen groups from GO and the barrier effect of intumescent and loosely structure of char layers.     

Improving the thermal and mechanical properties of polysulfone by incorporation of graphene oxide

Nanocomposites of polysulfone (PSF)-graphene oxide (GO) were prepared by classical phase inversion method. The structural and surface features and the mechanical and thermal performances of the prepared materials were investigated in detail. TEM and X-ray diffraction analysis indicated a good compatibility and excellent dispersability with PSF matrix for the low GO content (0.25, 0.5 and 1 wt.%) composites. It was observed that GO dispersion was reasonably homogeneous for the composite with 2 wt.% GO. The mechanical properties of the prepared materials were found to be greatly enhanced by the addition of GO for some compositions. The thermogravimetrical investigation demonstrated considerable improvements in thermal stability for the composite with low GO content. This novel material offers a feasible candidate for practical membrane application.     

Microstructural interpretation of the ablative properties of phenolic–quartz hybrid fabric reinforced phenolic resin composites

The thermal decomposition behavior of phenolic fiber and phenolic resin (PR) matrix was investigated by using a thermo gravimetric analyzer in nitrogen. The ablative properties of the composite specimens were quantitatively evaluated by performing oxyacetylene flame test and exhaust plume ablative test with a small liquid motor. The ablative properties of phenolic–quartz hybrid fabric reinforced phenolic resin (P–Q/PR) composites were compared with those of phenolic fabric and quartz fabric reinforced (P/PR and Q/PR) composites. The patterns and microstructures of the ablated composite specimens were also studied, and the advantages of the hybrid reinforced composites under ablation conditions were interpreted. The phenolic fiber decomposed similarly to the manner in which the PR did. The mixture rule can be used to predict the mass loss rate of the P–Q/PR composites during the oxyacetylene flame test. After the oxyacetylene flame test, there was no crack or delamination can be observed in P–Q/PR composite specimens and the carbonaceous residue blocks which were produced by the phenolic fiber and the PR were attached well to the quartz fibers. The resistance to heat-flow erosion of the P–Q/PR composites had significantly improved and the mass loss of the P–Q/PR composites (24.6%) was much lower than those of the Q/PR composites (56.4%) and the P/PR composites (86.3%) in the exhaust plume ablative test with a small liquid motor. A vis-à-vis char layer of the P–Q/PR composites formed during this ablation.     

Comparison of the thermal properties between composites reinforced by raw and amino-functionalized carbon materials

Carbon materials, such as graphite oxides, carbon nanotubes and graphenes, have exceptional thermal conductivity, which render them excellent candidates as fillers in advanced thermal interface materials for high density electronics. In this paper, these carbon materials were functionalized with 4,4′-diaminodiphenyl sulphone (DDS), to enhance the bonding between the carbon materials and the resin matrix. Their visibly different properties were investigated. It seems that DDS-functionalization can obviously improve the interfacial heat transfer between the carbon materials and the epoxy matrix. The thermal conductivity enhancement of D-Graphene composites (0.493 W/m K) was about 30% higher than that of D-MWNTs composites (0.387 W/m K) at 0.5 vol.% loading. The different effects among EGO, D-EGO, MWNTs, D-MWNTs and D-Graphene in polymer composites were also discussed. It was demonstrated that DDS-functionalized carbon materials had an obvious effect on the thermal performances of composite materials and were more effective in thermal conductivity enhancement.     

Highly conductive graphene oxide/polyaniline hybrid polymer nanocomposites with simultaneously improved mechanical properties

Graphene oxide (GO) was added to a polymer composites system consisting of surfactant-wrapped/doped polyaniline (PANI) and divinylbenzene (DVB). The nanocomposites were fabricated by a simple blending, ultrasonic dispersion and curing process. The new composites show higher conductivity (0.02–9.8 S/cm) than the other reported polymer system filled with PANI (10⁻⁹–10⁻¹ S/cm). With only 0.45 wt% loading of GO, at least 29% enhancement in electric conductivity and 29.8% increase in bending modulus of the composites were gained. Besides, thermal stability of the composites was also improved. UV–Vis spectroscopy, X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM) revealed that addition of GO improves the dispersion of PANI in the polymer composite, which is the key to realize high conductivity.     

Effect of imidazolium phosphate and multiwalled carbon nanotubes on thermal stability and flame retardancy of polylactide

A series of composites based on polylactide (PLA), have been prepared by melt-blending with multiwalled carbon nanotubes (MWNT) and Tri(1-hydroxyethyl-3-methylimidazolium chloride) phosphate (IP) functionalized MWNT (MIP). The morphology, thermal stability and burning behavior of the composites were investigated by Field Emission Scanning Electron Microscopy (FESEM), Thermogravimetric Analysis (TGA) and Cone Calorimeter Test (CCT), respectively. Significant improvement in fire retardant performance was observed for the PLA/MIP composite from CCT (reducing both the heat release rate and the total heat release) and TGA (increasing the char residue) compared to PLA/MWNT. SEM and Raman spectroscopy were utilized to explore the surface morphology and chemical structure of the char residues. It revealed that the catalytic charring effect of IP, the physical crosslinking effect of MWNT, and the combined effect of both IP and MWNT (forming continuous and compact char layers) were very efficient in improving the flame retarding properties of PLA/MIP composite.     

Synthesis and structure evolution of phenolic resin/silicone hybrid composites with improved thermal stability

Phenolic resin/silicone hybrid composites (MPR) were prepared by a facile and low-cost method. FTIR results show that polycondensation of siloxane occurs in the presence of catalyst and water in the system, and siloxane oligomer was formed. During the curing process, the transesterification reaction between siloxane oligomer and phenolic resin (PR) makes silicon incorporated into PR. The TGA results indicate that introducing Si–O structure into PR can effectively improve the thermal stability of the resin. Compared with cured neat PR, temperatures at 5 and 10% mass loss of cured MPR can be improved by 43 and 36 °C. Its char yield at 800 °C was increased by about 9.1%. Cured MPR has been characterized by FTIR, XPS, XRD and Raman spectra to discuss the chemical state changes of silicon during pyrolysis process, as well as the effect of silicon on the char yield. On the one hand, the formation of Si–O–C structure can reduce the number of phenyl hydroxyl groups, which contributes to the reduced weight loss. On the other hand, the results indicate that Si–O_x structure was formed from the oxidation of Si–CH₃ and hydrolysis of Si–O–C structures. According to Raman analyses, introducing silicone into the system cannot help to promote the formation of a more ordered structure. Additionally, the mechanical properties of cured MPR have also been improved.     

Nylon-6/Graphene composites modified through polymeric modification of graphene

The covalent functionalization of graphene oxide (GO) with poly(vinyl alcohol) (PVA) via ester linkages (GO-es-PVA) as well as the characterization of modified graphene based Nylon-6 (PA6) composite prepared by solution mixing techniques was examined. The anchoring of PVA chains on GO sheets was confirmed by XPS and FTIR measurements. The resulting functionalized sample became soluble in formic acid, allowing solution-phase processing for preparation of PA6/GO composites. Answering to the efficient polymer-chain grafting, a homogeneously dispersion of GO sheets in PA6 matrix and a dramatic improvement of interface adhesion between nanosheets and matrix were observed in PA6/GO-es-PVA composites by SEM and TEM. The depressed crystallization of PA6 chains in PA6/GO-es-PVA composites was investigated by their DSC and XRD results.     

Effects of carbon nanotubes and carbon fiber reinforcements on thermal conductivity and ablation properties of carbon/phenolic composites

The ablation properties and thermal conductivity of carbon nanotube (CNT) and carbon fiber (CF)/phenolic composites were evaluated for different filler types and structures. It was found that the mechanical and thermal properties of phenolic-polymer matrix composites were improved significantly by the addition of carbon materials as reinforcement. The concentrations of CF and CNT reinforcing materials used in this study were 30 vol% and 0.5 wt%, respectively. The thermal conductivity and thermal diffusion of the different composites were observed during ablation testing, using an oxygen–kerosene (1:1) flame torch. The thermal conductivity of CF mat/phenolic composites was higher than that of random CF/phenolic composites. Both CF mat and CNT/phenolic composites exhibited much better thermal conductivity and ablation properties than did neat phenolic resin. The more conductive carbon materials significantly enhanced the heat conduction and dissipation from the flame location, thereby minimizing local thermal damage.     

Thermal diffusivity, thermal conductivity, and specific heat of flax fiber–HDPE biocomposites at processing temperatures

There is increasing work on the use of flax fibers as reinforcement for manufacturing composites because of their lower cost and environmental benefit. During manufacturing of such natural fiber–plastic composites, heat transfer is involved, but information about the thermal conductivity and thermal diffusivity at the processing temperatures is not available. In this study, the thermal conductivity, thermal diffusivity, and specific heat of flax fiber–high density polyethylene (HDPE) biocomposites were determined in the temperature range of 170–200 °C. The fiber contents in biocomposites were 10%, 20%, and 30% by mass. Using the line-source technique, the instrumental setup was developed to measure the thermal conductivity of biocomposites. It was found that the thermal conductivity, thermal diffusivity, and specific heat decreased with increasing fiber content, but thermal conductivity and thermal diffusivity did not change significantly with temperature in the range studied. The specific heat of the biocomposites increased gradually with temperature.     

Effect of crab shell particles on the thermomechanical and thermal properties of polybenzoxazine matrix

For various molecular ratios ranging between 0% and 30%, the effect of Crab Shell Particles (CSP) on the thermal and thermomechanical properties of polybenzoxazine has been studied. The high contents of CaCO₃ particles in CSP clearly improve both the thermomechanical and thermal properties of the polybenzoxazine corresponding to a gain in storage modulus and glass transition temperature of 137% and 25%, respectively, at 30% CSP loading. Thermal analysis reveals that the polybenzoxazine matrix filled with CSP also increases the initial decomposition temperatures and the char yield of composites which reaches 49% at maximum CSP content.     

三聚氰胺聚磷酸盐和次磷酸铝协效阻燃高密度纤维板复合材料

将三聚氰胺聚磷酸盐(MPP)和次磷酸铝(AP)阻燃剂添加到木纤维/酚醛树脂(WF/PR)复合材料中,通过人造板热压工艺技术制备阻燃高密度纤维板(MPP-AP-WF/PR)复合材料,探索了MPP和AP组成复配阻燃剂时,MPP-AP-WF/PR复合材料达到最佳阻燃性能时MPP与AP的最佳质量比。采用弯曲强度、吸水厚度膨胀率、吸水率、热失重和极限氧指数(LOI)研究阻燃剂对MPP-AP-WF/PR复合材料的力学性能、耐水性能、耐热性能和阻燃性能的影响,探讨其阻燃机制。结果表明,添加阻燃剂之后,MPP-AP-WF/PR复合材料的力学性能和耐水性能明显降低;而热失重测试结果表明,阻燃剂对MPP-AP-WF/PR复合材料的初始耐热性能没有明显影响,但两者在高温下的协同效应有助于提高残炭量;LOI测试结果表明,单独使用时,MPP比AP具有更好的阻燃效果,当MPP和AP复配使用、MPP与AP的质量比为1∶2时,MPP-AP-WF/PR复合材料具有最好的阻燃效果,这是由于MPP和AP存在协同效用。且SEM和EDS表征发现,MPP-AP-WF/PR复合材料燃烧之后形成致密的含磷酸类物质的炭层,有效阻止了O₂和热量进入到炭层的内部,从而提高了MPP-AP-WF/PR复合材料的阻燃性能。      

Effect of surface treatment on thermal stability of the hemp-PLA composites: Correlation of activation energy with thermal degradation

The thermal behavior of hemp-poly lactic acid composites with both untreated and chemically surface modified hemp fiber was characterized by means of activation energy of thermal degradation. Three chemical surface modification employed were; alkali, silane and acetic anhydride. Model-free isoconversion Flynn–Wall–Ozawa method was chosen to evaluate the activation energy of composites. The results indicated that composites prepared with acetic anhydride modified hemp had 10–13% higher activation energy compared to other composites. Further, among the three surface modifications, acetic anhydride resulted in higher activation energy (159–163 kJ/mol). Fourier transform infrared spectroscopy supported the findings of thermogravimetric analysis results, wherein surface functionalization changes were observed as a result of surface modification of hemp fiber. It was concluded that, higher bond energy results in higher activation energy, which improves thermal stability. The activation energy data can aid in better understanding of the thermal degradation behavior of composites as a function of composite processing.     

Three-dimensional carbon nanotube based polymer composites for thermal management

In this study, the porous multiwall carbon nanotube (MWCNT) foams possessing three-dimensional (3D) scaffold structures have been introduced into polydimethylsiloxane (PDMS) for enhancing the overall thermal conductivity (TC). This unique interconnected structure of freeze-dried MWCNT foams can provide thermally conductive pathways leading to higher TC. The TC of 3D MWCNT and PDMS composites can reach 0.82 W/m K, which is about 455% that of pure PDMS, and 300% higher than that of composites prepared from traditional blending process. The obtained polymer composites not only exhibit superior mechanical properties but also dimensional stability. To evaluate the performance of thermal management, the LED modulus incorporated with the 3D MWCNT/PDMS composite as heat sink is also fabricated. The composites display much faster and higher temperature rise than the pristine PDMS matrix, suggestive of its better thermal dissipation. These results imply that the as-developed 3D-MWCNT/PDMS composite can be a good candidate in thermal interface for thermal management of electronic devices.     

原位氨基化氧化石墨烯/聚酰亚胺复合材料的制备及性能

以1,4-双（4-氨基-2-三氟甲基苯氧基）苯（6FAPB）和3,3',4,4'-二苯醚四酸二酐（ODPA）为合成聚酰亚胺（PI）的单体,首先采用原位氨基化方法使氧化石墨烯（GO）与6FAPB反应转变为原位氨基化GO,再与ODPA和剩余的6FAPB发生聚合反应得到原位氨基化GO/聚酰胺酸（PAA）溶液。涂膜后,经热酰亚胺化制备出GO质量分数分别为0.05wt%、0.1wt%、0.3wt%、0.5wt%和1.0wt%的原位氨基化GO/PI复合材料膜。利用FTIR、XPS、XRD、UV-vis、TGA、TMA、SEM、拉伸性能测试及接触角测试对原位氨基化GO/PI复合材料的结构和性能进行表征。结果表明,原位氨基化使GO以化学键与PI大分子链连接,有利于GO在复合材料基体中的稳定和均匀分散。XRD结果表明,所得到的原位氨基化GO/PI复合材料膜均为无定型结构。随GO质量分数增加,原位氨基化GO/PI复合材料薄膜的光学透明性急剧降低,但力学性能和热稳定性有一定提高。当GO的质量分数为1.0wt%时,原位氨基化GO/PI复合材料的拉伸强度由64 MPa增加到83 MPa,杨氏模量由1.67 GPa提高到2.10 GPa,10%热失重温度由593℃增加到597℃,玻璃化转变温度变化不大。由于热酰亚胺化后GO表面的大部分含氧官能团消失,原位氨基化GO/PI复合材料膜的吸水率由0.86%降低至0.58%,水接触角由72.5°增加到77.8°。     

Thermal conductivity of graphene nanoplatelets filled composites fabricated by solvent-free processing for the excellent filler dispersion and a theoretical approach for the composites containing the geometrized fillers

The thermal conductivity of polymer composites containing nanofillers such as GNP (graphene nanoplatelet) and carbon black (CB) was investigated using experimental and theoretical approaches. We developed a fabrication method that allows different shapes and sizes of nanofillers to be highly dispersed in polymer resin. When the bulk and in-plane thermal conductivities of the fabricated composites were measured, they were found to increase rapidly as the GNP filler content increased. The in-plane thermal conductivity of composites with 20 wt.% GNP filler was found to reach a maximum value of 1.98 W/m K. The measured thermal conductivities were compared with the calculated values based on a micromechanics model where the waviness of nanofillers could be taken into account. The waviness of the incorporated GNP filler is an important physical factor that determines the thermal conductivity of composites and must be taken into consideration in theoretical calculations.