Synthesis and Curing Kinetics of UV-Curable Waterborne Bisphenol-S Epoxy-Acrylate/Polyurethane-Acrylate/Methylacryloylpropyl-POSS Nanocomposites

In order to prepare waterborne UV-curable polyurethane-acrylate (PUA) /epoxyl-acrylate (ERA) nanocomposites, the PUA, bisphenol-S epoxy acrylate (BPSEA) and methylacryloylpropyl polyhedral oligomeric silsesquioxanes (MAP-POSS) were synthesized. UV-curable BPSEA/PUA/MAP-POSS nanocomposites were prepared. The curing process, kinetics, and properties of the nanocomposites were investigated by Fourier transform infrared spectrometer (FTIR), differential scanning calorimeter (DSC) and dynamic mechanical analyzer (DMA). The base-acid resistance ability, adhesive strength, and hardness of coating films were determined. The results showed that these nanocomposites could be cured by both UV-light irradiation and a thermal free radical polymerization. Under the UV-light irradiation, they could be cured basically completely in about 20 min. The thermal free radical curing reaction could be described by a two-parameter autocatalytic ?esták-Berggren (S-B) model. The dynamic mechanical loss peak temperature, T_p, of the cured nanocomposites increased with increasing MAP-POSS content up to 8 wt%, an enhancement of 5.8°C over the pure BPSEA/PUA system, and then decreased. Films of the nanocomposites also had better base-acid resistance ability and hardness than pure BPSEA/PUA.     

长亚甲基链段改性固化剂的制备与性能

采用二官能度环氧树脂对己二胺进行改性,得到了含多段长亚甲基链段的柔性固化剂。利用红外光谱表征其基本结构。采用环氧树脂E-44与之进行固化,通过不同温度下固化时间对力学强度影响的分析,初步确定其最佳固化条件为80 ℃,6 h。通过热重分析检测不同固化比例下固化产物的热稳定性,并采用差示扫描量热法研究该固化剂的固化动力学参数、反应活性、最佳固化温度及时间。对其固化物拉伸剪切强度进行测试,测试结果表明：在固化比例为1:0.5时,在-196 ℃、室温、60 ℃下的拉伸剪切强度分别为16.84,14.73和13.52 MPa,基本满足实际应用的需求。     

Studies on the Thermal Properties of Epoxy Resins Modified with Two Kinds of Silanes

Dimethyldiethoxysilane (DMDES) and diphenyldimethoxysilane (DPDMS)-containing epoxy resins were synthesized by dehydration polycondensation. The chemical structures were determined by FT-IR, ¹H NMR, and ¹³C NMR. The cured samples, with 4, 4′-diaminodiphenylmethane (DDM) as curing agent, were investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and tensile and impact testing. Results showed that DMDES and DPDMS-modified epoxy resins possess higher glass transition temperatures, better thermal stability, and better fracture toughness than the neat epoxy resin.     

Preparation,Characterization, and Properties of Resol-Based Benzoxazine Intermediates and Glass Cloth Reinforced Laminates Based on Their Polymers

A series of multifunctional benzoxazine intermediates (Boz-p-x) with different molecular weights and curing behaviors were synthesized based on resol. Their composition was controlled by adjusting the mole ratio (x) of aniline to phenol; i.e. the content of benzoxazine rings formed was varied. The chemical structures and hydrogen-bonding interaction of the intermediates were confirmed by ¹H nuclear magnetic resonance (NMR) spectroscopy and Fourier transform infrared (FTIR) spectroscopy. Their curing behaviors were investigated by differential scanning calorimetry (DSC). The results indicated that the residual phenolic hydroxyl groups in the intermediates formed two kinds of hydrogen bonding and acted as a catalyst in the curing process. The more residual phenolic hydroxyl present, the higher the glass transition temperature was and the faster the curing reaction. Further, glass cloth reinforced laminates based on poly(Boz-p-x)s were prepared. The mechanical properties of the laminates were tested by dynamic mechanical analysis (DMA) and flexural measurements. The poly(Boz-p-8) laminate exhibited the highest glass transition temperature (T _g) and mechanical properties in the laminates. Its T _g was 237°C and its flexural modulus and flexural strength were 26.8 GPa and 597 MPa, respectively. The laminates of poly(Boz-p-6), poly(Boz-p-8), and poly(Boz-p-10) showed good modulus retention at elevated temperature due to more ?OH???N hydrogen-bonding interactions. In addition, poly(Boz-p-x)s exhibited high thermal stability and char yield at 800°C.     

Characterization of hydrogenated amorphous carbon thin films by end-Hall ion beam deposition

Pure hydrogenated amorphous carbon (α-C:H) and nitrogen doped hydrogenated amorphous carbon (α-C:H:N) thin films were prepared using end-Hall (EH) ion beam deposition with a beam energy ranging from 24 eV to 48 eV. The composition, microstructure and mechanical properties of the films were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, scanning probe microscopy (SPM), and nano-scratch tests. The films are uniform and smooth with root mean square roughness values of 0.5-0.8 nm for α-C:H and 0.35 nm for α-C:H:N films. When the ion energy was increased from 24 eV to 48 eV, the fraction of sp³ bonding in the α-C:H films increased from 36% to 55%, the hardness increased from 8 GPa to 12.5 GPa, and the Young's modulus increased from 100 GPa to 130 GPa. In the α-C:H:N films, N/C atomic ratio, the hardness and Young's modulus of the α-C:H:N films are, 0.087, 15 and 145 GPa, respectively. The results indicate that both higher ion energy and a small amount of N doping improve the mechanical properties of the films. The results have demonstrated that smooth and uniform α-C:H and α-C:H:N films with large area and reasonably high hardness and Young's modulus can be synthesized by EH ion source.     

Load transfer from fiber to polymer matrix,studied by measuring the apparent elastic modulus of carbon fiber embedded in epoxy

Load transfer from a single carbon fiber to the surrounding epoxy matrix was studied by measuring the apparent tensile modulus of the fiber while the fiber was embedded in epoxy and comparing the apparent modulus (1650 GPa) with the real modulus (230 GPa). Thus, it was found that 87% of the tensile load applied to the fiber was transferred to the epoxy.     

激光固化快速成形SL7510型光敏树脂性能研究

利用红外光谱仪、紫外激光固化快速成形设备、旋转黏度计、电子拉力试验机以及热机械性能分析仪对美国Huantsman公司的SL7510型光敏树脂进行了性能研究.实验结果表明,SL7510型光敏树脂是一种环氧树脂-丙烯酸酯混杂型光敏树脂,它在30℃时的黏度为335 mPa·s,临界曝光量为10.9 mJ/cm2,透射深度为0.14 mm,固化体积收缩率为4.03%,固化物托伸强度为40.8 MPa,拉伸弹性模量为2009.2 MPa,断裂伸长率为13.6%,玻璃化温度为62℃.同时,根据所测定的光敏树脂临界曝光量和透射深度数值,选定了紫外激光固化快速成形设备的加工参数,制作了电话机外壳,其制作效果较好.     

Preparation and Characterization of Silicon-containing Polyarylacetylene/montmorilloite Nanocomposites

Dimethylphenylpropargyl ammonium bromide (DMPPAB) was synthesized and used to modify pristine montmorillonite (MMT) by a cation exchange process. The organically modified montmorillonite (OMMT) was verified and used to mix with a silicon-containing polyarylacetylene (PSA) as well as MMT. The PSA/MMT and PSA/OMMT nanocomposites were prepared by solution under sonication and melting intercalation processes, respectively, and then cured by a step heating process. The thermal and flexural properties of the cured PSA and nanocomposites were studied by thermogravimetric and dynamic mechanical analysis. The results showed that the intercalation of DMPPAB into the MMT galleries made the d-spacing enlarge. During PSA curing, the cure heat of PSA caused the MMT and OMMT to delaminate and exfoliate in the PSA matrix. The glass transition temperature of the cured PSA and nanocomposites were higher than 500?°C. The inner acetylenic groups in the PSA resin could further crosslink above 300?°C. The temperature at 5% mass loss of the cured PSA decreased by 4.6% with 3% mass fraction of OMMT loading, and the char yield of the cured PSA changed only slightly. The flexural strength of the cured PSA was augmented with addition of MMT or OMMT, but the flexural modulus of the cured PSA decreased slightly. The flexural strength of the cured nanocomposite increased from 20.1?MPa to 30.1?MPa when 3% mass fraction of OMMT was added into the PSA matrix.     

Characterization of new cellulose sansevieria ehrenbergii fibers for polymer composites

Natural cellulose fibers were newly identified from the sources of sansevieria ehrenbergii plant. These fibers were extracted using the mechanical decortication process. The hierarchical cell structure of the plant and fibers was analyzed using scanning electron microscope, optical microscope, Fourier transforms infrared, and X-ray diffraction. The density and diameter of the fibers were found to be approximately 0.887?g/cm³ and 10–250?μm, respectively. The various chemical compositions were analyzed and compared with other natural fibers. The thermal stability of the fiber was examined through thermogravimetric analysis/differential thermogravimetric analysis (DTG). The maximum peak temperature was obtained at 333.02?°C in DTG curve. The raw fibers exhibited a tensile strength of 50–585?MPa, an elongation at break of 2.8–21.7%, a Young’s modulus of 2.5–7.5?GPa, and a corrected compliances Young’s modulus of 2.5–7.8?GPa.     

Simultaneously Enhancing Mechanical Properties and Melt Flow Ability of Polyamide 6 by Blending with a Hyperbranched Polymer

A series of polyamide 6/hyperbranched polymers (PA6/HBP) blends with different HBP contents was prepared by melt processing using a twin-screw extruder. The HBP was synthesized on the basis of pentaerythritol and dimethyl terephthalate according to a one-step method. The melt flow behavior, crystallization behavior, morphology, and mechanical properties of the PA6/HBP blends were investigated. The results showed that the melt flow index of the blends was greatly improved by a small amount of HBP. The yield strength, tensile modulus, Izod impact strength, and flexural strength of samples were simultaneously enhanced from 54.6 MPa, 0.5 GPa, 3.8 kJ/m², 56.9 MPa for pure PA6 to 61.1 MPa, 0.7 GPa, 5.3 kJ/m², 67.1 MPa for PA6 blends with 2.0 wt% HBP, respectively. The PA6/HBP blends showed the higher content of α-form crystal and a higher degree of crystallinity than those of pure PA6.     

A comparison of the mechanical strength and stiffness of MWNT-PMMA and MWNT-epoxy nanocomposites

The surface of multi-wall carbon nanotubes (MWNTs) was functionalized by covalent linking of long alkyl chains. Such functionalization led to a much better tube dispersion in organic solvents than pristine nanotubes, favored the formation of homogenous nanocomposite films, and yielded good interfacial bonding between the nanotubes and two polymer matrices: a thermo-set (Epon 828/T-403) and a thermoplastic (PMMA). Tensile tests indicated, however, that the reinforcement was greatly affected by the type of polymer matrix used. Relative to pure PMMA, a 32% improvement in tensile modulus and a 28% increase in tensile strength were observed in PMMA-based nanocomposites using 1.0 wt% nanotube filler. Contrasting with this, no improvement in mechanical properties was observed in epoxy-based nanocomposites. The poorer mechanical performance of the latter system can be explained by a decrease of the crosslinking density of the epoxy matrix in the nanocomposites, relative to pure epoxy. Indeed we demonstrate that the presence of nanotubes promotes an increase in the activation energy of the curing reaction in epoxy, and a decrease of the degree of curing.     

Comparative Study of the Effect of Addition of Silica and Silicate Nanofillers on the Properties of Epoxy Coatings

The effect of adding different amounts (0.5–3 wt%) of nanosilica (NS) and organomodified montmorillonite (MMT) to diglycidyl ether bisphenol A (DGEBA) cured with isophorone diamine at different temperature on the viscoelastic, topographical and gelation properties of epoxy resin was studied. Gel time measurements revealed that both NS and MMT accelerated the curing reaction of DGEBA with IPDA. Both nanofillers were adequately dispersed in DGEBA. The particle size distribution depended on the amount of nanofiller. A broader distribution for NS than for MMT filled epoxy was obtained. On the other hand, an increase in the curing temperature was required to obtain the intercalation of the epoxy into the MMT tactoids. At room temperature, the addition of NS increased both the stiffness (high storage modulus) and the toughness (an increase in the area and height of the tan δ curve) of epoxy, but no significant differences were found by curing at higher temperature. Epoxy/MMT composites showed higher storage modulus in the rubbery region. The improved properties imparted by NS can be ascribed to the interactions between the silanol moieties on the nanosilica surface and the polar groups in the epoxy, whereas the improvement imparted by MMT organoclay was related to tactoid intercalation within the epoxy matrix.     

The effect of the microstructure of porous alumina films on the mechanical properties of glass-fiber-reinforced aluminum laminates

The glass-fiber-reinforced aluminum laminates were obtained by anodizing aluminum alloy under anodizing voltage of 10, 20, and 30?V in the 200?g/L H₃PO₄ electrolyte. Scanning electron microscopy (SEM), short beam, and tensile tests were employed to determine the surface morphology, interlaminar shear strength (ILSS) and tensile strength of laminates, respectively. The results also show that the epoxy penetrates into the pores of the anodic films, and this is the mechanism of adhesion. The ILSS and tensile strength of the anodized specimens (under 20?V) respectively increased by approximately 50 and 15% comparing with those of the non-anodized specimens. This increase of mechanical properties results from the porous surface of aluminum providing greater mechanical interlocking to epoxy. The ILSS and tensile strengths of the anodized specimens increased with the increase of anodizing voltage from 10 to 20?V; however, it decreased when the voltage further increased to 30?V. It is considered that the microstructure evolution of the porous films has a significant effect on the mechanical properties of the laminates.     

Mechanical properties of kaolinite ‘macro-crystals’

The mechanical properties of a rare sample of kaolinite macroscopic crystals were evaluated using instrumented indentation. The crystals were also characterized by X-ray diffraction, scanning electron microscopy, atomic force microscopy and Fourier transform infrared spectroscopy before and after heat treatment at 1100°C. The results are explained in terms of the fracture process occurring in the layered structure of kaolinite, and of the effect of roughness on the hardness and elastic modulus. Data analysis using One-way ANOVA (p?<?0.05) showed that the values of hardness and elastic modulus obtained are statistically homogeneous. Before heat treatment, the sample was composed essentially of kaolinite, with hardness of 42?MPa and elastic modulus equal to 1.3?GPa. After calcination at 1100°C, the sample keeps its layered habit and consists of amorphous metakaolinite. The hardness increases to 360?MPa and the elastic modulus increases to 6.9?GPa.     

Microstructure and mechanical properties of nano-Y2O3 dispersed ferritic steel synthesized by mechanical alloying and consolidated by pulse plasma sintering

Ferritic steel with compositions 83.0Fe–13.5Cr–2.0Al–0.5Ti (alloy A), 79.0Fe–17.5Cr–2.0Al–0.5Ti (alloy B), 75.0Fe–21.5Cr–2.0Al–0.5Ti (alloy C) and 71.0Fe–25.5Cr–2.0Al–0.5Ti (alloy D) (all in wt%) each with a 1.0?wt% nano-Y₂O₃ dispersion were synthesized by mechanical alloying and consolidated by pulse plasma sintering at 600, 800 and 1000°C using a 75-MPa uniaxial pressure applied for 5?min and a 70-kA pulse current at 3?Hz pulse frequency. X-ray diffraction, scanning and transmission electron microscopy and energy disperse spectroscopy techniques have been used to characterize the microstructural and phase evolution of all the alloys at different stages of mechano-chemical synthesis and consolidation. Mechanical properties in terms of hardness, compressive strength, yield strength and Young's modulus were determined using a micro/nano-indenter and universal testing machine. All ferritic alloys recorded very high levels of compressive strength (850–2850?MPa), yield strength (500–1556?MPa), Young's modulus (175–250?GPa) and nanoindentation hardness (9.5–15.5?GPa), with up to 1–1.5 times greater strength than other oxide dispersion-strengthened ferritic steels (<1200?MPa). These extraordinary levels of mechanical properties can be attributed to the typical microstructure of uniform dispersion of 10–20-nm Y₂Ti₂O₇ or Y₂O₃ particles in a high-alloy ferritic matrix.     

Vulcanization and Thermal Properties of Silicone Rubber/Fluorine Rubber Blends

With the rapid development of automobile, aviation, aerospace, machinery and other fields, rubber products used in these fields required to meet higher requirements. Fluorine rubber (FKM) and silicone rubber (MVQ) have excellent performance in some areas. However, the FKM is poor in low-temperature resistance and processing performance, limiting its applicability. Although the MVQ has a wide range of temperature and excellent processing performance, but its mechanical properties and oil resistance are not good. In this work, the MVQ/FKM blends were prepared by two different mechanical blending methods. The effects of the mixing process, mass ratio, curing system and conditions of the blends were studied. The chemical compositions of the blends were analyzed by infrared spectroscopy (IR). The compatibility and the thermal properties of the blends were investigated by dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA), respectively. The results showed that the mechanical properties, compatibility and thermal stability of the blends were the best when they were prepared by kneading the FKM and MVQ individually in a two-rool mill roll, then mixing them together homegeneously with an MVQ/FKM mass ratio of 10/90, curing system of (4 phr, 1/9) dicumyl peroxide (DCP)/N, N-Dicinnamylidene-1, 6-hexanediamine (3^# Vulcanizer), first curing conditions at 170?°C under 10?MPa for 30?min and post curing conditions at 200?°C for 6?hours at 1 atmospheric pressure.     

Strengthening in high-pressure quenched Zr

The present study examined the effects of pressure (range: 1–6?GPa) on microstructure and mechanical properties of pure Zr. Pressure significantly affected refining of Zr microstructure. When 5?GPa pressure was applied, ω-phase was observed in processed specimen, and volume fraction sharply increased to 57.4% for specimen pressurized-quenched at 6?GPa. Benefitting from refinement of acicular-shaped α (α′) plates and the formation of equiaxial ω-phase, the yield strength of the sample quenched from 6?GPa reached ～616?MPa, which is almost twice as that of coarse-grained Zr.     

Preparation and Properties of Epoxy‐Clay Nanocomposites

Epoxy‐clay nanocomposites were synthesized to examine the effects of adding different contents of nanoclays on the physical, mechanical, and thermal properties of the epoxy resin system used in composite pipes manufacturing. Diglycidyl ether of bisphenol‐A (epoxy) with a cycloaliphatic amine heat curing hardner was reinforced by 1–7 wt.% of an organically modified type of montmorillonite. SEM results showed the change in failure of epoxy from brittle to tough mode by addition of nanoclays. X‐ray results indicated some degree of exfoliation by 1 wt.% clay and a decrease in d‐spacing in higher clay loadings after that. The heat‐distortion temperature of epoxy-clay nanocomposites increased from 125.5 to 138.7°C with 3 wt.% organoclay loading. Tensile and flexural modulus increased with increasing clay loading in this type of nanocomposite, but addition of organically modified clay decreased the tensile and flexural strengths and tensile elongation at break. Addition of 7 wt.% nanoclay improved the impact strength by 25.6%.     

Microstructure and Mechanical Properties of Isotactic Polypropylene Films Fabricated via Melt-Extrusion and Uniaxial-Stretching

In this work, isotactic polypropylene (iPP) melt was slowly extruded through a slit die of a single-screw extruder. Once the iPP melt left the die, it was uniaxially stretched at different stretching rates (SRs). Via this process its microstructure can be manipulated, it was subsequently investigated by wide-angle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS), differential scanning calorimetry (DSC), polarized optical microscopy (POM), and Fourier transform infrared spectroscopy (FTIR). Furthermore, the mechanical properties (including tensile strength, modulus, toughness, and strain-hardening) were investigated. The results showed that the tensile strength and modulus of the melt-stretched iPP films gradually increased with increasing SRs. In addition, the toughness and elongation at break showed maximum values for iPP films melt-stretched at 30 cm/min. Moreover, compared with other melt-stretched films, the iPP films melt-stretched at 90 cm/min exhibited an obvious strain-hardening behavior at lower strain.     

Tensile strength of aluminium nitride films

Two-layered aluminium nitride (AlN)/silicon nitride microbridges were fabricated for microbridge tests to evaluate the elastic modulus, residual stress and tensile strength of the AlN films. The silicon nitride layer was added to increase the robustness of the structure. In a microbridge test, load was applied to the centre of a microbridge and was gradually increased by a nano-indenter equipped with a wedge tip until the sample was broken, while displacement was recorded coherently. Measurements were performed on single-layered silicon nitride microbridges and two-layered AlN/silicon nitride microbridges respectively. The data were fitted to a theory to derive the elastic modulus, residual stress and tensile strength of the silicon nitride films and AlN films. For the AlN films, the three parameters were determined to be 200, 0.06 and 0.3?GPa, respectively. The values of elastic modulus obtained were consistent with those measured by conventional nano-indentation method. The tensile strength value can be used as a reference to reflect the maximum tolerable tensile stress of AlN films when they are used in micro-electromechanical devices.