Tannin–Phenol Formaldehyde Resins As Binders for Cellulosic Fibers: Mechanical Properties

In this study Eucalyptus tannin (T) was isolated from outer bark of Eucalyptus trees;as sodium phenoxide salt and used as extender or copolymer into phenol formaldehyde (PF) resin at five percent (10, 20, 30, 40 and 50)% W/W. Tan-nin-phenol formaldehyde (TPF) and tannin formaldehyde-phenol formaldehyde (TFPF) resins that synthesized in this study were evaluated as adhesive material for cellulosic fibers by study the mechanical properties of the composite sheets .The results show that the substituting of (PF) with tannin at (10 –50)% W/W give resins with mechanical properties comparable or near to those of pure (PF) , where the tensile strength at break (Tb) ranging from 15.15 Mpa to 22.27 Mpa as compared with 17.6 Mpa for pure (PF);while the impact strength properties (Im) of composites sheets increased with increased the (T) percents which were about 5.16 KJ/m2 for (TPF – 10%) and 7.21 KJ/m2 for (TPF - 50%) .On the other hand modification of (T) to tannin formaldehyde resin (TF) appear less performance at the results of this study , this effect probably to low penetration of (TFPF) resins between the small voids of cellulose fibers when soaked it in resin solutions. In general the results of this study indicate that the Eucalyptus tannin can be used for par-tial substitution of (PF) to produce resins with feasible mechanical properties and can be used in some applications of (PF) resins.

Characterization of the Mechanical Properties of Urea-Formaldehyde Microcapsules

The mechanical properties of urea?formaldehyde (U?F) microcapsules were determined using a micromanipulation technique and a theoretical model. Loading?unloading, compressing and holding, and compressing to bursting tests at different speeds between two parallel plates for single microcapsules were carried out. It was found that the U?F microcapsules were visco-elastic (mainly elastic) at small compressive deformation, and plastic under large deformation. The transition point from elastic to plastic occurred at about (14±0.2)% compressive deformation. All the microcapsules would disrupt when compressed to about (17±0.2)% deformation, and the burst force increased linearly with their diameter. Compressing speed had no remarkable effect on both burst force and burst deformation. Liquid filled non-permeable and linear elastic spherical membrane model was used to simulate the uniaxial compression of single microcapsule, and its membrane modulus Eh was determined by fitting model prediction to experimental data. The average value of Eh was estimated to be (478±8) N/m.

Mechanical properties and energy evolution of Beishan shallow-layer granite under different unloading paths

Rock has mechanical characteristics and a fracture damage mechanism that are closely related to its loading history and loading path. The mechanical properties, fracture damage features, acoustic emission(AE) characteristics, and strain energy evolution of the Beishan shallow-layer granite used in triaxial unloading tests were investigated in this study. Three groups of triaxial tests, namely, conventional triaxial compression test(Group Ⅰ), maintaining deviatoric stress synchronously unloading confining pressure test(Group Ⅱ), and loading axial pressure synchronously unloading confining pressure test(Group Ⅲ), were carried out for the cylindrical granite specimens. AE monitoring device was utilized in these tests to determine the degree to which the AE waves and AE events reflected the degree of rock damage. In addition, the crack stress thresholds of the specimens were determined by volumetric strain method and AE parameter method, and strain energy evolution of the rock was explored in different damage stages. The results show that the shallow-layer granite experiences brittle failure during the triaxial loading test and unloading test, and the rock has a greater damage degree during the unloading test. The crack stress thresholds of these samples vary greatly between tests, but the threshold ratios of all samples are similar in the same crack damage stage. The Mogi-Coulomb strength criterion can better describe the unloading failure strength of the rock. The evolution of the AE parameter characteristics and strain energy differs between the specimens used in different stress path tests. The dissipative strain energy is the largest in Group Ⅱ and the smallest in Group Ⅰ.

Temperature dependence of mechanical properties and damage evolution of hot dry rocks under rapid cooling

Understanding the differences in mechanical properties and damage characteristics of granitoid under high temperatures is crucial for exploring deep geothermal resources.This study analyzes the evolution of the acoustic emission(AE)characteristics and mechanical parameters of granodiorite and granite after heating and water cooling by uniaxial compression and variable-angle shear tests under different temperature gradients.We identify their changes in mesostructure and mineral composition with electron probe microanalysis and scanning electron microscopy.Results show that these two hot dry rocks have similar diagenetic minerals and microstructure,but show significantly different mechanical and acoustic characteristics,and even opposing evolution trends in a certain temperature range.At the temperatures ranging from 100℃to 500℃,the compressive and shear mechanical properties of granodiorite switch repeatedly between weakening and strengthening,and those of granite show a continuous weakening trend.At 600℃,both rocks exhibit a deterioration of mechanical properties.The damage mode of granite is characterized by initiating at low stress,exponential evolutionary activity,and intensified energy release.In contrast,granodiorite exhibits the characteristics of initiating at high stress,volatile evolutionary activity,and intermittent energy release,due to its more stable microstructure and fewer thermal defects compared to granite.As the temperature increases,the initiation and propagation of secondary cracks in granodiorite are suppressed to a certain extent,and the seismicity and brittleness are enhanced.The subtle differences in grain size,microscopic heterogeneity,and mineral composition of the two hot dry rocks determine the different acoustic-mechanical characteristics under heating and cooling,and the evolution trends with temperature.These findings are of great significance for the scientific and efficient construction of rock mass engineering by rationally utilizing different rock strata properties.

Shear mechanical properties and fracturing responses of layered rough jointed rock-like materials

This study aims to investigate mechanical properties and failure mechanisms of layered rock with rough joint surfaces under direct shear loading.Cubic layered samples with dimensions of 100 mm×100 mm×100 mm were casted using rock-like materials,with anisotropic angle(α)and joint roughness coefficient(JRC)ranging from 15°to 75°and 2-20,respectively.The direct shear tests were conducted under the application of initial normal stress(σ_(n)) ranging from 1-4 MPa.The test results indicate significant differences in mechanical properties,acoustic emission(AE)responses,maximum principal strain fields,and ultimate failure modes of layered samples under different test conditions.The peak stress increases with the increasingαand achieves a maximum value atα=60°or 75°.As σ_(n) increases,the peak stress shows an increasing trend,with correlation coefficients R² ranging from 0.918 to 0.995 for the linear least squares fitting.As JRC increases from 2-4 to 18-20,the cohesion increases by 86.32%whenα=15°,while the cohesion decreases by 27.93%whenα=75°.The differences in roughness characteristics of shear failure surface induced byαresult in anisotropic post-peak AE responses,which is characterized by active AE signals whenαis small and quiet AE signals for a largeα.For a given JRC=6-8 andσ_(n)=1 MPa,asαincreases,the accumulative AE counts increase by 224.31%(αincreased from 15°to 60°),and then decrease by 14.68%(αincreased from 60°to 75°).The shear failure surface is formed along the weak interlayer whenα=15°and penetrates the layered matrix whenα=60°.Whenα=15°,as σ_(n) increases,the adjacent weak interlayer induces a change in the direction of tensile cracks propagation,resulting in a stepped pattern of cracks distribution.The increase in JRC intensifies roughness characteristics of shear failure surface for a smallα,however,it is not pronounced for a largeα.The findings will contribute to a better understanding of the mechanical responses and failure mechanisms of the layered rocks subjected to shear loads.

The Influence of Rice Husk Ash on Mechanical Properties of the Mortar and Concrete: A Critical Review

Increasing the population and infrastructure in both emerging and developed countries requires a considerable amount of cement, which significantly affects the environment. The primary materials of concrete (‘cement’) production emit a large quantity of CO2 into the environment. Also, the cost of conventional building materials like cement gives motivation to find geopolymer waste materials for concrete. To reduce harmful effects on the environment and cost of traditional concrete substance, alternative waste materials like rice husk ash (RHA), ground granulated blast-furnace (GGBS), fly ash (FA), and metakaolin (MK) can be used due to their pozzolanic behavior. RHA waste material with a high silica concentration obtained from burning rice husks can possibly be used as a supplementary cementitious material (SCM) in the manufacturing of concrete, and its strong pozzolanic properties can contribute to the strength and impermeability of concrete. This review paper highlights a summary of the positive effect of using RHA as a partial substitute for cement in building construction, as well as its optimal inclusion of enhanced mechanical properties like compressive strength, flexural strength, and split tensile strength of mortar and concrete.

The effect of urea pretreatment on the formaldehyde emission and properties of straw particleboard

For manufacturing low-formaldehyde emission particleboard from wheat straw and urea-formaldehyde （UF） resins using urea treatment for indoor environments, we investigated the influence of urea treatment on the formaldehyde emission, physical and mechanical properties of the manufactured particleboard. Wheat straws were treated at three levels of urea concentration （5%, 10%, 15%） and 95℃ as holding temperature. Wheat straw particleboards were manufactured using hot press at 180℃ and 3 MPa with two types of UF adhesive （UF-45, UF-91）. Then the formaldehyde emission values, physical properties and mechanical properties were considered. The results show that the for- maldehyde emission value was decreased by increasing urea concentration. Furthermore, the results indicate that the specimens under urea treatment have better mechanical and physical properties compared with control specimens. Also specimens under urea treatment at 10% concentration and UF-91 type adhesive have the most optimum physical and mechanical strength.

Mechanical and field-emission properties of individual ZnO nanowires studied in situ by transmission electron microscopy

The mechanical and field-emission properties of individual ZnO nanowires,grown by a solid-vapour phase thermal sublimation process,were studied in situ by transmission electron microscopy(TEM)using a home-made TEM specimen holder.The mechanical resonance is electrically induced by applying an oscillating voltage,and in situ imaging has been achieved simultaneously.The mechanical results indicate that the elastic bending modulus of individual ZnO nanowires were measured to be～58 GPa.A nanobalance was buil...

Mechanical properties and damage characteristics of solidified body-coal combination in continuous driving and gangue backfilling

Recovery of the coal buried under buildings,railways and water bodies and the residual coal in irregularly arranged fully mechanized mining faces is a common engineering problem facing underground coal mining.In this study,a mining technology of continuous driving and gangue backfilling(CDGB)was proposed.The technology,which can not only alleviate ground subsidence and gangue discharge,but also release the above-mentioned coals,contributes to green and efficient sustainable development of mining.The stability of the system of the solidified body-reserved coal pillar combination(S-C combination)is crucial to the CDGB technology.Therefore,it is of great significance to explore the mechanical and damage characteristics of S-C combination in the synergistic bearing process.First,four sets of differentshaped S-C combination specimens were fabricated and a S-C combination bearing structure in CDGB was constructed to explore the differences in mechanical characteristics and damage modes of different-shaped S-C combination specimens during CDGB.Subsequently,their surface strain field evolutions and acoustic emission(AE)response characteristics in the load-bearing process were obtained with the aid of the digital image correlation technique and the AE signal monitoring system.Furthermore,a damage evolution model based on AE parameters and mechanical parameters was established to clarify the damage evolution law.The following results were obtained:(1)The free area of S-C combination can serve as a quantitative index to evaluate the stability of the overburden control system;(2)The concept of critical value k of the free area was first proposed.When the free area exceeds the critical value k(free area ratio greater than 1.13),the deformation resistance and the free area changes becomes negatively correlated;(3)As the free area expands,the failure of the S-C combination specimen evolves from tensile failure to shear failure.The distribution characteristics of the axial strain field also verified such a change in the failure mode;(4)When the free area expands,the peak AE count gradually changes from“double peaks”to“a single peak”.In this process,the expansion of free area shortens the time for accumulating and releasing energy during loading.Micro cracks generated in the specimen change from a phased steep growth to a continuous increase,and the process in which micro cracks develop,converge,intersect and connect to form macro cracks accelerates.The damage evolution law concluded based on AE parameters and mechanical parameters can well characterize the damage evolution process of S-C combination,providing certain reference for the study on the synergistic bearing of S-C combination during CDGB.

Effect of optimal aging treatment on magnetic performance and mechanical properties of sintered Nd-Fe-B permanent magnets

The magnetic performance and mechanical properties including hardness, brittleness, fracture toughness and strength characteristics of the as-sintered and the optimal aged Nd-Fe-B magnets were examined in this work. A new method of Vickers hardness indentation combined with acoustic emission was used to test the brittleness of the magnets.The results show that the magnetic properties of the magnets could be improved through aging treatment, especially the intrinsic coercive force. But it is accompanied by a decrease of strength and fracture toughness. Theoretical calculation confirms that acoustic emission energy accumulated count value could be used to characterize the material brittleness. The bending fracture morphologies of the as-sintered and the optimal aged Nd Fe B magnets were investigated with the emphasis on the relationship between mechanical properties and microstructure using a field emission scanning electron microscopy(FE-SEM). The research results indicate that the intergranular fracture is the primary fracture mechanism for both as-sintered and optimal aged Nd Fe B magnets. Aging treatment changes the morphology and distribution of the Nd-rich phases, reducing the sliding resistance between Nd_2Fe_(14)B main crystal grains and lowers the grain boundary strength, which is the main reason for the strength and fracture toughness decrease of the aged Nd-Fe-B magnets.

Effect of Multi-Hydroxyl Polymer-Treated MUF Resin on the Mechanical Properties of Particleboard Manufactured with Reed Straw

The poor bonding performance between aqueous adhesives represented by melamine-urea formaldehyde(MUF)resins and reed straw hinders their applications in the field of non-wood-based panels.Multi-hydroxyl polymers are highly reactive and are often used as crosslinkers.This study fabricated a resin with a strengthened crosslinked structure by combining a multi-hydroxyl polymer and MUF resin prepolymer.The reed particleboard was prepared by using this resin as an adhesive and reed stalk as the matrix.The results show that neighboring molecules combined to form C–O–C bonds that strengthened the cross-linked structure of the resin.In addition,the viscosity of the resin was increased,and a continuous adhesive layer on the surface of reed particles was formed,which slowed the penetration of reed particles.The adhesive layer significantly improved the mechanical properties of the reed particleboard.The maximum modulus of rupture(MOR),modulus of elasticity(MOE),and internal bonding strength(IB)of the reed particleboard were 33.53,4126,and 0.79 MPa,respectively.The IB of the board was 3.3 times higher than that of the reed particleboard prepared with a conventional MUF resin.Reed straw is a non-wood biomass material that has the advantage of sustainable development and may replace woodbased materials to produce particleboard.This resin-prepared reed particleboard is expected to be used in areas such as custom furniture and engineering materials.

Mechanical behaviors of mylonitic granite and granitic protomylonite in a deep ductile shear zone

For projects near the tectonic belt,mylonite of varying metamorphic degrees may be present.The matrix proportion of rock reflects its internal microscopic characteristics,thus it is beneficial for engineering geology to study the effect of the matrix proportion on the mechanical properties and rupture behaviors of rock.Samples of mylonitic granite and granitic protomylonite with varying matrix proportions were obtained from a ductile shear zone for a series of uniaxial compression and acoustic emission(AE)tests.The results showed that with the increase in matrix proportion,the average strength and elastic modulus of the samples increased,and the rock sample with the largest matrix proportion exhibited the maximum peak stress of 244.42 MPa,which was 45.86%greater than the average peak stress of the rock samples with the smallest matrix proportions.For the rock samples with larger matrix proportion,their mechanical parameters exhibited greater dispersion and the large-scale appearance of AE events occurred earlier,showing a relatively gradual failure process.These samples had larger accumulated AE parameter values and greater degree of failure.In contrast,for samples with smaller matrix proportions,the large-scale appearance of AE events occurred close to the peak stress,indicating that the occurrence of damage and fractures was centralized and instantaneous.These samples had lower accumulated AE parameter values and fewer cracks after failure.Additionally,for the rock samples with more matrix proportion,the average variance of the b-value was 1.1,which was lower than that of rock samples with the smallest matrix proportion(the average variance of the b-value was 3.7).Furthermore,it can be predicted that under certain stress,the failure depth around a tunnel is generally smaller when the strength of rock samples with larger matrix proportion is greater.

Preparation and properties of waste tea leaves particleboard

Urea-formaldehyde （UF） adhesive is the main source of formaldehyde emission from UF-bonded boards. The components in waste tea leaves can react with formaldehyde to serve as a raw material in the production of low formaldehyde emission boards. In our study, waste tea leaves and UF adhesive were employed in the preparation of waste tea leaves particleboard （WTLB）. An orthogonal experimental method was applied to investigate the effects of process parameters on formaldehyde emission and mechanical properties of WTLB. The results indicated that： 1） waste tea leaves had the ability to abate formaldehyde emission from boards; and 2） density of the WTLB was a significant factor affecting its modulus of rupture （MOR）, modulus of elasticity （MOE） and internal bonding （IB）.

Synergistic Reinforcement of Phenol-Formaldehyde Resin Composites by Poly(Hexanedithiol)/Graphene Oxide

In this paper, the preparation of graphene oxide was achieved by Hummers method and the surface modification was achieved by poly(hexaneditiol), which was a synthetic thermotropic liquid crystalline polymer. The c-PHDT/GO/PF composites were prepared by blending, rolling and compression molding techniques. Then, the as-prepared samples were characterized by FTIR, Raman, XRD, TGA and POM to obtain information on their structures and properties. After that, the effects of c-PHDT/GO content on the mechanical properties, friction performance and dynamic mechanical performance of c-PHDT/GO/PF composites were studied by Mechanical and Dynamic Mechanical Analysis (DMA) methods. Also, Scanning Electron Microscope (SEM) was used for the characterization of wear and fracture surface morphology. The results revealed that the reinforcing effect of c-PHDT/GO was significant as a considerable enhancement on the mechanical performance of c-PHDT/GO/PF composite as compared to pure phenol-formaldehyde composites was observed: the impact strength, bending modulus and bending strength increased from 1.63 kJ/m2, 8.61 GPa and 41.55 MPa to 2.31 kJ/m2, 10.16 GPa and 54.40 MPa respectively at the c-PHDT/GO content = 0.75%. Moreover, the initial storage modulus increased by 28.4%, while the wear mass loss decreased by 17.8%. More importantly, the reinforcement by c-PHDT/GO was further enhanced as compared to GO/PF and p-PHDT/GO/PF composites, the impact strength of c-PHDT/GO/PF composite increased by 27.6% and 11.1%, the bending strength increased by 11.8% and 7.6%, the initial storage modulus increased by 16.2% and 4.2% and the mass loss due to wear decreased by 12.7% and 8.8%, respectively. Based on these results, we can conclude that the surface modification of GO by poly(hexanedithiol), which includes synergistic effect by c-PHDT and GO, improves the interfacial adhesion between GO and the resin matrix, thus reinforcing the composites.

Study on Physical and Mechanical Properties of Poplar Modified by Phenol-formaldehyde Resin

Impregnation method can effectively improve physical and mechanical properties of wood. In this study, plantation poplar lumbers are impregnated by a low molecular weight phenol-formaldehyde resin solution with concentration of 30% under vacuum-pressure process, and then dried and machined according to the related standards. The results show that the physical and mechanical properties of poplar can be improved by the treatment, except for toughness. The average density of poplar increases from 0.397 to 0.710 g/cm3, the modulus of elasticity in static bending, the bending strength and the compressive strength parallel to grain of treated specimens increase by 56.71%, 112.97% and 87.69%, respectively, compared to the untreated. And the hardness values on radial and tangential sections, and nail holding power as well as abrasion resistance of treated specimens improve by 283.87%, 82.78%, 71.43% and 22.06%, respectively; while toughness decreases by 48.80%.

Carbon Emission Cycle and Literature Measurement of Carbon Fiber Vehicles

Carbon fiber is a kind of high-temperature fiber with high modulus and strength characteristics.Carbon fiber material is made of carbon fiber braid with carbon content>90%.Among them,resin-based carbon fiber reinforced composite material is often used as automotive structural material.Compared with the A36 steel commonly used in automobiles,the T300/5208 carbon fiber reinforced epoxy resin composite commonly used in automobiles has a higher tensile strength of 2500-3300 MPa and a lower density of 6.25 g/cm 3,showing great performance advantages.In this paper,by analyzing the trend of automobile lightweight,and exploring the development prospects of carbon fiber in the field of automobile lightweight,the literature in the Elsevier database is analyzed by scientific measurement analysis method,and the research hotspot in the field is listed.The relationship between the development of fiber materials and the promotion of policies is analyzed by comparing the number of carbon fiber automobile literature publications and key event nodes.This paper proposes a keyword-based influence calculation method.Through drawing analysis tools of information visualization scientific knowledge map and scientific measurement methods of keyword,it proposes the scientific measurement analysis literature of on-board carbon fiber,explores and discusses some frontier directions of automotive carbon fiber materials.The research provides reference for studying automobile lightweight carbon fiber material.

超临界CO_(2)作用下高阶煤微观结构及力学特性-声发射特征研究

超临界CO_(2)压裂技术作为极具发展潜力的压裂煤体增透瓦斯技术,明晰其对煤体的影响机制,有助于推动该技术的机理研究和实践工程应用。为准确表征超临界CO_(2)作用下高阶煤的孔裂隙结构及力学特性变化,以焦煤集团中马村矿的高阶煤为试验对象,通过自主搭建的超临界CO_(2)浸泡试验系统,结合全自动物理吸附仪(BET)以及全自动压汞仪(MIP),对超临界CO_(2)处理前后高阶煤的孔裂隙结构变化进行分析,并利用单轴压缩和声发射试验系统对超临界CO_(2)处理前后高阶煤的单轴压缩力学特性和声发射特征进行测定。结果表明:超临界CO_(2)对高阶煤具有良好的扩孔增渗作用。超临界CO_(2)处理后高阶煤的微小孔孔容占比降低,中大孔孔容占比增大,且高阶煤的总孔容增大;超临界CO_(2)对高阶煤的力学特性具有明显的劣化作用。超临界CO_(2)处理后高阶煤单轴抗压强度和弹性模量均显著下降,降幅分别为70.06%和55.56%,且超临界CO_(2)处理后高阶煤的内部声发射信号活跃度明显下降,高阶煤单轴抗压时间、累计振铃计数以及累计能量分别降低了98.68 s、95.14×10^(3)个、200.30 V·ms,降幅分别为46.65%、37.65%、50.03%,高阶煤累计振铃计数以及累计能量平静期占比均显著增加,缓增期占比均降低,激增期前者占比降低,后者占比小幅度增加。研究成果将有助于推动超临界CO_(2)压裂技术的机理研究,对深部高阶煤的煤层气开采和CO_(2)地下封存具有一定指导意义。

动静载作用下充填节理砂岩应力波传播特性研究

为研究节理角度和不同围压作用下的充填节理岩石的动态力学特性和应力波传播规律,利用改造后的动静组合加载霍普金森压杆(split Hopkinson pressure bar, SHPB)装置,对充填节理厚度为8 mm的砂岩试样进行冲击试验,研究不同围压等级(0、4、6和8 MPa)和不同节理倾角(0°、15°、30°、45°)下充填节理试样的动态力学特性和应力波传播的规律,采用应力波斜射理论并进行验证。试验结果表明:(1)完整砂岩的反射波幅值最小,以0 MPa为例,反射波幅值从0.194×10^(-3)增长到0.299×10^(-3),与倾角成正相关,透射波幅值与倾角成负相关,且从0.169×10^(-3)减小到0.053×10^(-3);以0°为例,反射波幅值与围压呈负相关,且从0.194×10^(-3)减小到0.074×10^(-3),透射波幅值相反从0.169×10^(-3)增长到0.257×10^(-3);(2)在冲击动载作用下,一定程度围压可以起到限制变形,抑制胶结面分离,提高承载能力;节理倾角越大的充填节理产生的变形越大,承载状态越差;(3)倾角试件随着围压增大反射能力降低,透射能力提高,0°倾角试件的反射系数从0.603减小到0.147,透射系数从0.569均匀增加到0.789,围压试件随着倾角的增大反射能力增大,透射能力降低与理论分析规律一致;(4)节理倾角与试样吸收能密度呈负相关,围压与试样吸收能密度呈正相关,与围压作用下的透反射规律一致。

排污指标法律属性辨析——兼及“排污权”交易制度的走向

“排污权”实为排污指标。对生产者的法律意义是,在许可的种类和数量范围内排污,它既包含权利,也包含义务。从排污不受限制到受法律规制的变化来看,排污指标的功能是设置义务。排污指标本身既不是权利,也不是财产。各种“排污权”权利说都不成立,无法为排污指标交易提供理论支持。排污指标具有某些财产属性是权力发挥作用的结果,其在交易过程中以财产的面貌出现,回到生产过程则回归到义务分配机制的本来属性。受自身本质属性的限制,排污指标的财产权能是不完整的。根据排污指标的性质和指标交易的目的,排污指标交易制度这样安排比较合适:排污指标初始分配采用当前占有无偿分配的方式;政府可以预留一定比例的储备指标,以便对排污指标的供给进行宏观调控;排污指标的交易价格由市场根据供求关系决定。

褐土色低红外发射率涂层的制备及性能研究

以环氧树脂为黏合剂,片状Cu粉为功能颜料,石墨烯和邻苯二甲酸二辛酯(DOP)为界面结构改性剂,制备得到了一种具有良好综合性能的褐土色低红外发射率涂层。系统研究了片状Cu粉添加量(质量分数)、石墨烯添加量(质量分数)及DOP添加量(质量分数)对涂层微结构、发射率、光泽度及力学性能的影响规律。结果表明:合适的片状Cu粉添加量可以构建出表面结构规整、颜料分散均匀、片状Cu粉定向与涂层表面平行的微观结构,从而使涂层实现较低的发射率性能。石墨烯改性可提高涂层的致密度,减少由树脂填充的空隙,从而可进一步降低涂层的发射率。黑色石墨烯改性可明显强化涂层对可见光的吸收作用,从而降低涂层的光泽度。另外,利用石墨烯固有的高强度及高韧性特点,可改善涂层的柔韧性和耐冲击强度。DOP可通过减弱环氧树脂分子间作用力和增强分子链的移动性来提高涂层的塑性和韧性,从而可明显改善涂层的柔韧性和耐冲击强度。当涂层中片状Cu粉、石墨烯和DOP的添加量分别为40%、8%和7%时,所制备的褐土色涂层具有最佳的发射率(0.222)、光泽度(20.4)、附着力(1级)、柔韧性(2mm)及耐冲击强度(50kg·cm)性能。