The Effect of OMMT on the Morphology and Mechanical Properties of PVC/ABS Blends

Poly(vinyl chloride) (PVC)/acrylonitrile-butadiene-styrene (ABS) blends containing organically modified montmorillonite (OMMT) were prepared using a twin-screw extruder followed by injection molding. The OMMT dispersion was evaluated by X-ray diffraction and transmission electron microscopy. The clay was preferentially situated in the PVC phase and across the interfaces of PVC/ABS. The effect of the addition of OMMT on the morphology and mechanical properties was also evaluated. Scanning electron microscopy revealed a large reduction in domain size when OMMT was used. The mechanical properties were studied through tensile and impact tests. The yield stress increased when an appropriate amount of OMMT was used without impairing the impact strength.     

Effect of Rubber Content of ABS on the Mechanical Properties of ABS/Clay Nanocomposites

One approach to improve the impact strength of acrylonitrile–butadiene–styrene (ABS)/clay nanocomposites is to increase rubber content. To investigate the effect of the rubber content of ABS on the mechanical properties of the ABS/clay nanocomposites, other parameters were fixed and ABS/clay nanocomposites containing various rubber contents were prepared in this study. Also the effect of the UV stabilizer on the mechanical properties of ABS/clay nanocomposite was studied. For addition of 3 wt% clay, ABS nanocomposite with 35 wt% content of rubber displayed the highest reinforcement ratio for tensile properties and impact strength.     

Effects of Viscosity Ratio on Morphological,Rheological and Mechanical Properties of PP/PBT Melt Spun Alloy Fibers

Phase morphology formation plays an important role in the mechanical properties of polymer alloy fibers. The development of the blend morphology depends not only on the intrinsic properties of the component polymers but also on extrinsic factors such as viscosity ratio, λ, in the melt spinning process. The effects of blend component viscosity ratio on the morphological, rheological, and mechanical properties of polypropylene/poly(butylene terephthalate) (PP/PBT) melt spun alloy fibers were investigated. Accordingly, two kinds of PP as matrix phase and two kinds of PBT as dispersed phase, with various melt viscosity, were physically mixed and then blended during the extrusion step of melt spinning. SEM micrographs and rheological and mechanical properties evaluations showed that the morphology of PP/PBT alloy fibers strongly depend on the viscosity ratio, λ. Finer diameter PBT fibrils were observed for Viscosity ratios less than 1 (λ < 1) compared to samples with λ > 1. The best mechanical properties in alloy fiber samples were obtained for the viscosity ratio closest to unity (sample with λ = 0.9). The lowest differences among measured complex viscosities at various shear rates (0.1, 10, and 100 s^?1) were also observed in samples with λ = 0.9. The results showed that the mechanical properties of alloy fiber samples are affected not only by morphological properties observed at different viscosity ratios but also by the properties of the individual polymer components.     

The Mechanical Properties,Compatibility, and Thermal Stabilities of POE-Graft-Methyl Methacrylate and Acrylonitrile(POE-g-MAN)/ Styrene-Acrylonitrile Copolymer (SAN Resin) Blends

POE-graft-methyl methacrylate and acrylonitrile (POE-g-MAN) was prepared by graft copolymerization of methyl methacrylate (MMA) and acrylonitrile (AN) onto polyethylene-octene copolymers (POE) with suspension polymerization. POE-g-MAN/SAN resin blends (AOMS) were prepared by blending POE-g-MAN with styrene-acrylonitrile copolymer (SAN resin). The mechanical properties, compatibility, and thermal stabilities of AOMS were studied. The notched impact strength of the blends reached 54.0 kJ/m² when the AN/(MMA + AN) ratio (f_AN) of POE-g-MAN, benzoyl peroxide dosage, and POE content in AOMS were 15 wt%, 1.0 wt%, and 25 wt%, respectively. Transmission electron microscopy analysis showed that the highest toughness occurred when the size of POE-g-MAN particles and the surface-to-surface inter-particle distance were proper. Scanning electron microscopy analysis indicated that the AOMS fracture surface had plastic flow visible, which looked like a fibril morphology when the AN/(MMA + AN) ratio (f_AN) of POE-g-MAN was 15 wt%. The toughening mechanism of AOMS was shear yielding of the matrix, which endowed AOMS with remarkable toughness. Dynamic mechanical thermal analysis showed that the compatibility of the POE phase and SAN phase improved after graft copolymerization of MMA and AN onto POE. When the grafting chain polarity was appropriate, the miscibility between POE-g-MAN and SAN resin was the best. Thermogravimetry analysis showed that thermal stability of AOMS increased with increasing AN units in POE-g-MAN.     

The Effect of Epoxidized Natural Rubber and Two Kinds of Organoclay upon Molecular Interaction,Structure and Mechanical Properties of (Styrene-Butadiene Rubber/Acrylonitrile-Butadiene Rubber/Organoclay) Nanocomposites

Epoxidized natural rubber (ENR50) and two different kinds of organoclay (C30B and C15A) were used in blends of styrene-butadiene rubber (SBR) and acrylonitrile butadiene rubber (NBR) and their effects upon interaction between phases, morphology, and mechanical properties of the blends were investigated. The compounds were characterized by means of Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM), and differential scanning calorimetry (DSC). The obtained results showed formation of hydrogen bonding between the compounds ingredients due to incorporation of C30B, especially in presence of ENR. AFM and FE-SEM analysis revealed good dispersion of the nanoparticles in the polymer matrix upon addition of ENR as well as better dispersion of C30B than C15A in the NBR phase. XRD results showed a greater expansion of the silicate layers by simultaneous use of organoclay and ENR Incorporation of organoclay alone or in combination with ENR in the blends caused shifting of the SBR T_g toward the NBR T_g. The tensile properties of the blends showed improvement by using nanoparticles in the presence of ENR.     

Pithecellobium Clypearia Benth Fiber/Recycled Acrylonitrile-Butadiene-Styrene (ABS) Composites Prepared in a Vane Extruder: Analysis of Mechanical Properties and Morphology

The effect of compatibilizer types and concentrations on the mechanical properties and morphology of Pithecellobium Clypearia Benth Fiber (PCBF)/recycled ABS composites prepared by a vane extruder were characterized. In addition, the percentage of compatibilizer was fixed at 8%, and the effect of lubricant concentrations on the mechanical properties and torque behaviors of the composites was also studied. Maleic anhydride grafted ABS (ABS-g-MAH) and maleic anhydride grafted PS (PS-g-MAH) were used as compatibilizers; the lubricant used was Struktol TPW 604 (blend of aliphatic carboxylic acid salts and mono diamides). The composite with 8% ABS-g-MAH showed superior mechanical properties compared to the composite without compatibilizer and the 8% PS-g-MAH compatibilized composites. Compared with PS-g-MAH, ABS-g-MAH was more effective for the composites to improve the interfacial interaction and mechanical properties. The comprehensive mechanical properties of PCBF/recycled ABS composite filled with 4% lubricant were better than the composites without lubricant and the composites with any other content of TPW 604. Moreover, the torque of the composites in an internal mixer decreased with an increasing lubricant content.     

Simulation of Gas-Assisted Injection Molding of High-Density Polyethylene: The Role of Rheological Properties and Physical Fields on the Crystalline Morphology

The shear and temperature fields in the filling process during gas penetration of gas-assisted injection molding (GAIM) of two kinds of high-density polyethylene (HDPE) with different molecular weights (M_w) were simulated numerically via Moldflow 6.1. The simulated results indicated that HDPE with higher M_w showed a relatively low shear rate in both the outer and inner zone of GAIM parts as compared to that with lower M_w, while the shear rate of the inner zone of the parts of the two materials were lower than that of the outer zone, which has a lower temperature and shorter time for crystallization. Considering the remarkable difference between their viscosities, a model of the shear thinning and recovering effects on crystallization during the GAIM process is proposed. Through the simulation, along with the analysis of their viscosities and rheological properties, the influence of molecular weight and shear and temperature fields on two special kinds of crystalline morphology (i.e., shish-kebabs and banded spherulites) during GAIM were interpreted.     

Effect of Surface Roughness, Type and Size of Model Aggregates on the Bond Strength of Aggregate/Mortar Interface

The paper reports on a two-stage study of the interface between three types of model cylindrical aggregates (sandstone, limestone and granite) and two types of mortar matrix (plain and 20% Silica Fume mortar). In the first stage, the surface roughness (R _a) of the aggregates and the interfacial bond strength using push-out specimens have been experimentally determined. In the second, aggregate push-out geometry has been modelled using two different approaches. In the first approach, the surface roughness is ignored and the cylindrical aggregates are assumed to have an ideally smooth surface with a constant radius, r ₀ over the aggregate length, L. In the second approach, the surface roughness of the aggregates is included so that the radius, r varies along the length of the cored rock aggregate. Hence, the influence of the surface roughness of the aggregates on the interfacial bond strength is obtained. It is found that the surface roughness plays a significant role in determining the interfacial bond strength, in particular of smaller size aggregates. The effect, however, diminishes as the aggregate size increases, regardless of the aggregate and mortar type.     

The Effect of Structure of the Clay Modifier on the Morphology and Properties of Polystyrene/Clay Nanocomposites Prepared via In Situ Suspension Polymerization

Polystyrene (PS)/organoclay nanocomposites were prepared via free radical suspension polymerization. Two kinds of organoclay were used, labeled KT and KD, modified by trimethyloctadecyl ammonium (TM) and dimethyldioctadecyl ammonium (DM) ions, respectively. Nanocomposites containing various amounts of both of the organoclay nanoparticles (1, 3, and 5 wt%) were prepared. The wide angle X-ray diffraction (WAXD) results revealed intercalation in both of the nanocomposites. The greatest improvement in thermal stability of the nanocomposites was achieved with 5 wt% of organo-MMT for both of the clays. The nanocomposite containing 3 wt% of KT organo-MMT showed the greatest improvement of storage modulus. When the organoclay content exceeded 3 wt%, the storage moduli decreased compared to the nanocomposite filled with 3 wt% of the organoclay. D-spacing calculations using Bragg's law and WAXD data showed that the KT and KD nanoparticles were intercalated within the PS matrix, but with different extents of intercalation. The styrene conversions of the as-polymerized nanocomposite samples were obtained by a gravimetric method. The results showed that conversion decreased with incorporation of organoclay in the reaction recipe. Particle size was also increased by increasing nanoclay content.     

The Effect of Paraffinic Oil and Aromatic Oil on the Crosslinks and Physical Properties of Butyl Rubber

Butyl rubber (also known as isobutylene-isoprene rubber, IIR) compounds were prepared with paraffinic oil (PO) and aromatic oil (AO) to study the effect of the two kinds of processing oil on the crosslinks and physical properties of the IIR. The effect of processing oil on performance was studied by Mooney viscosity, differential scanning calorimetry (DSC), equilibrium swelling, mechanical and extraction experiments. The results showed that the Mooney viscosity of the PO blend was lower than that of the AO/IIR blend and the Tg of the PO blend was obviously lower than the pure IIR but the T_g of the AO blend had no change compared with pure IIR. In addition, according to the equilibrium swelling test, the average molecular weights between crosslinks of the vulcanizates which contained the processing oils were higher than that of pure IIR, with the average molecular weight between crosslinks of the AO blend, the highest, being 40.3% higher than that of the PO blend. The extraction experiments indicated that part of the processing oil could be extracted and the extracted part of AO was higher than that of the PO. Overall the PO was better than AO for acting as a processing oil for IIR.     

The Effects of Different Processing Methods on the Morphology and Properties of PP/EPDM/Nano-CaCO3 Ternary Blend

The effects of different processing methods (direct extrusion, two-step extrusion or lateral injection extrusion) on the morphology of polypropylene (PP)/ethylene-propylene-diene terpolymer (EPDM)/calcium carbonate nanoparticles (nano-CaCO₃) ternary blend were investigated, including the morphology of the EPDM phase and the distribution of nano-CaCO₃ particles, by means of scanning electron microscopy (SEM). The results showed that the processing methods had a significant influence on the morphology of the EPDM phase and the distribution of nano-CaCO₃ particles. In the lateral injection extruded blends, it was amazingly observed that the EPDM particles encapsulated the PP phase tightly, and the dimension of EPDM particles was remarkably decreased. It was also found that the content of nano-CaCO₃ particles in the matrix of the lateral injection extruded blends was less than that of the two-step extruded blend, and that of the direct extruded blend was most. The properties of the ternary blend, including dynamic mechanical properties, rheological properties, and crystallization, were characterized in order to confirm the variety of morphologies caused by the different processing methods. The differences in the crystallization temperature, elastic modulus, and glass transition temperature of the blends prepared by different methods well agreed with the variation of their morphology.     

助熔剂对绿色荧光粉Ba2 SiO4∶Eu2+ 颗粒形貌及发光性能的影响

采用高温固相法在弱还原气氛下合成了Ba₂SiO₄∶Eu²⁺绿色荧光粉,利用X射线衍射、扫描电子显微镜和荧光分光光度计考察了不同助熔剂对Ba₂SiO₄∶Eu²⁺荧光粉的结晶度、物相纯度、颗粒形貌和发光强度的影响,并详细讨论了不同助熔剂在荧光粉制备过程中的作用机理。结果表明:不加助熔剂时样品存在BaSi₂和SiO₂杂相;利用NH₄F、Na₂CO₃或H₃BO₃作为助熔剂时会抑制BaSi₂杂相的形成,而BaF₂作助熔剂可以得到纯的斜方晶系。与未加助熔剂合成的荧光粉相比,添加质量分数为2% 的BaF₂、NH₄F或Na₂CO₃后合成样品的发光强度分别提高了138%,81%和34%;而质量分数为2%的H₃BO₃作助熔剂时,荧光粉的发光强度反而降低了14%。BaF₂作助熔剂合成的荧光粉颗粒形貌接近球形,以NH₄F、Na₂CO₃或H₃BO₃作助熔剂合成的荧光粉颗粒形貌分别为不规则片状、纺锤体形和不规则多边形大颗粒。     

氧气含量对射频磁控溅射方法制备的NiO∶Cu/ZnO异质pn结的光电性能的影响

利用磁控溅射方法改变氧气含量制备了一系列NiO∶Cu/ZnO异质pn结。实验结果表明,氧含量对NiO∶Cu/ZnO异质pn结电学影响很大。相对于纯氩溅射,引入一定氧气(O2/(Ar+O2)比例为30%)后,NiO∶Cu/ZnO异质pn结的整流特性明显得到改善。与此同时,NiO∶Cu/ZnO异质pn结的光透过率也从40%增大到80%。这可能是由于氧气的轻量引入致使NiO∶Cu/ZnO异质pn结的结晶得到改善,薄膜内缺陷减少所致。进一步提高氧气含量,直到O2/(Ar+O2)比例至80%后,异质结的整流特性有所削弱,这可能是由于过多氧气的引入造成薄膜缺陷再次增多,进而影响到异质结的整流特性。这一结论得到了EDS、XRD、AFM和UV结果的支持。     

The Effect of TiO2 and MgO on the Thermoluminescence Properties of a Lithium Potassium Borate Glass System

The influence of dopant TiO₂ and co-dopant MgO on the thermoluminescence (TL) properties of lithium potassium borate glass (LKB) is reported in this paper. The glow curve exhibits a prominent peak (T_m) at 230 °C. The TL intensity was enhanced by a factor of ~3 due to the incorporation of MgO, and this was attributed to the creation of extra electron traps mediated by radiative recombination energy transfer. We achieved good linearity of the TL yield with dose, low fading, excellent reproducibility and a promising effective atomic number (Z_eff=8.89), all of which are highly suitable for dosimetry. The effect of heating rate, sunlight and dose rate on the TL are also examined. These attractive features demonstrate that our dosimeter is useful in medical radiation therapy.     

The Comparison of the Holographic Storage Properties of Fe:LiNbO3 and Fe:Ce:LiNbO3 Crystals

Holographic storage properties of iron-doped and cerium/iron-doped LiNbO3 with different doping concentrations and treatment conditions have been measured for different recording wavelengths. The results show that at recording wavelengths of 532 nm and 633 nm the holographic storage properties of Ce:Fe:LiNbO3 are generally better than those of Fe:LiNbO3.     

SiNWs:Tb3+的光学稳定性及Si纳米线对其发光特性的影响

荧光纳米材料不但具备纳米材料的优势,同时还具有优异的光学性质,被广泛应用于荧光标记、离子识别、荧光免疫分析、光学成像和医学诊断等方面。因此,荧光纳米材料的制备、结构分析和荧光特性等方面的研究备受人们的关注。为了获得发光强度大、荧光量子效率高和制备过程可控的Si基荧光纳米材料,实验进一步研究了Si纳米线对样品发光特性的影响和样品的光学稳定性。首先,基于固-液-固生长机制,在反应温度为1 100 ℃、N₂气流量为1 500 sccm、生长时间为15～60 min等工艺条件下,分别以“抛光”和“金字塔”织构表面的单晶Si(100)为衬底,生长出不同长度和分布的Si纳米线;以Au或Au-Al合金膜层作为金属催化剂,生长出密度分别约为108和1010 cm-2的Si纳米线;然后,利用L4514自动控温管式加热炉,基于高温固相法,在温度为1 100 ℃、掺杂时间为60 min和N₂气流量为1 000 sccm等工艺条件下,以高纯Tb₄O₇(99.99%)粉末为稀土掺杂剂对不同Si纳米线衬底进行稀土掺杂,制备一系列的荧光纳米材料SiNWs:Tb3+样品;室温下利用Hitachi F-4600型荧光分光光度计,固定激发光波长为243 nm、激发光狭缝为2.5 nm、发射光狭缝为2.5 nm、扫描波长范围为450～650 nm、光电倍增管(photomultiplier lube, PMT)电压为600 V等参数下,测量了不同样品的光致发光特性;最后,实验测试了该荧光纳米材料的光学稳定性,如时间(0～30 d)、温度(300～500 K)、酸碱(pH 1和11)、抗光漂白(0～120 min)等稳定性以及水溶性和分散性。结果显示,在衬底为“金字塔”织构表面上、生长时间为30 min、以Au为金属催化剂等条件下制备的Si纳米线为Tb3+掺杂衬底时,SiNWs:Tb3+的绿光发射强度较大,其发光强峰值位于554 nm,属于能级5D₄→7F₅的跃迁,另外在波长为494,593和628 nm出现了三条发光谱带,它们分别属于能级5D₄→7F₆,5D₄→7F₄和5D₄→7F₃的跃迁。另外,样品展示出了优异的时间、温度、酸碱和抗光漂白等光学稳定性,同时还具有良好的水溶性和分散性。如温度升高到500 K时,光发射强度仅降低了约8.9%左右;抗光漂白能力较强,用波长为365 nm、功率为450 W的紫外光源照射120 min,样品的绿光发射强度无衰减;酸、碱稳定性好,在pH 1的强酸(HCl)溶液中120 min未见衰减,在pH 11的强碱(NaOH)溶液中15 min内衰减较小, 随后发光强度出现了缓慢下降的趋势;当60 min后,样品的发光强度变得极其微弱。分析认为,在SiNWs:Tb3+表面有一层SiO₂包覆层,而NaOH溶液容易和SiO₂发生化学反应,随着时间延长SiO₂层被破坏,故样品发光强度降低;样品溶于水中放置30 d未见沉淀物,发光亮度均匀且分散性较好。在研究了制备温度、气体流量和掺杂时间等工艺条件之后,深入研究了Si纳米线自身变化对Tb3+绿光发射的影响。该材料展示出了良好的光学稳定性、水溶性和分散性,使其作为荧光标记物具有一定的应用价值。     

Relaxation Behavior of Laser-Polarized Xe Gas: Size Dependency and Wall Effect of the T1 Relaxation Time in Glass and Gelatin Bulbs

Size dependency of the relaxation time T₁ was measured for laser-polarized ¹²⁹Xe gas encapsulated in different sized cavities made by glass bulbs or gelatin capsules. The use of laser-polarized gas enhances the sensitivity a great deal, making it possible to measure the longer ¹²⁹Xe relaxation time in quite a short time. The size dependency is analyzed on the basis of the kinetic theory of gases and a relationship is derived in which the relaxation rate is connected with the square inverse of the diameter of the cavity. Such an analysis provides a novel parameter which denotes the wall effect on the relaxation rate when a gas molecule collides with the surface once in a second. The relaxation time of ¹²⁹Xe gas is also dependent on the material which forms the cavity. This dependency is large and the relaxation study using polarized ¹²⁹Xe gas is expected to offer important information about the state of the matter of the cavity wall.