Morphology,interfacial and mechanical properties of polylactide/poly(ethylene terephthalate glycol) blends compatibilized by polylactide-g-maleic anhydride

Polylactide/poly(ethylene terephthalate glycol) (PLA/PETG 80/20 wt) blends compatibilized with polylactide-g-maleic anhydride (PLA-g-MAH) were prepared by melt blending and the rheological, morphological and mechanical properties of the blends were studied. PLA/PETG (80/20 wt) blend formed a typical sea-island morphology, while upon compatibilization, the size and size distribution of the dispersed phase decreased significantly and the 3 wt% PLA-g-MAH compatibilized blend exhibited the smallest phase size and the narrowest distribution of the dispersed particles. The interfacial tension between PLA and PETG was determined from the morphological characteristics and the viscoelastic response of PLA/PETG blends via using two emulsion models. A minimum for PLA/PETG blend containing 3 wt% PLA-g-MAH was observed from both Palierne model and G–M model. The elongation-at-break increased by ∼320%, from 6.9% for PLA to 28.7% for the blend containing 3 wt% PLA-g-MAH without significant loss in the tensile modulus and tensile strength.     

Effect of organoclay platelets on morphology and properties of LLDPE/EMA blends

Blends of linear low density polyethylene (LLDPE) and ethylene-co-methyl acrylate (EMA) and their nanocomposites with two types of modified montmorillonite (organoclay) were explored in order to achieve an improved balance between stiffness and toughness. The nanocomposites were prepared in a HAAKE RHEOMIX at three different mixing sequences. The compression molded nanocomposites were utilized to evaluate the morphology and the properties like mechanical, dynamic mechanical and thermal. The results reveal that the morphology and the properties of the nanocomposites are dependent on the blending sequence as well as the type of nanoclay used. The addition of organoclay slightly increases the tensile modulus for all the nanocomposites. On the other hand, a drastic improvement of the impact strength was observed when the organoclay located at the dispersed EMA phase. The effects of clay concentration on the properties of the nanocomposites were also studied. The optimum dispersion as well as property was found for the nanocomposite at 5 wt% of the nano clay.     

Influence of P3HT concentration on morphological, optical and electrical properties of P3HT/PS and P3HT/PMMA binary blends

Poly(3-hexylthiophene) (P3HT) has interesting optoelectronic properties and a wide variety of applications such as solar cells and O-FET devices. It is a soluble conductive polymer but their mechanical properties are poor and its conductivity is unstable in environmental condition. With the finality of overcome these disadvantages, P3HT binary blends with two insulating polymers, polystyrene (PS) and polymethylmetacrilate (PMMA), have been synthesized by direct oxidation of 3-hexylthiophene with FeCl₃ as oxidant inside the insulator polymers. Molecular weight and polydispersity of P3HT polymer were measured by size exclusion chromatography and the degree of regioregularity by ¹H RMN. P3HT/PS and P3HT/PMMA thin films were prepared by spin-coating technique from toluene solution at different P3HT concentrations. The doped films were obtained by immersion during 30 s in a 0.3 M ferric chloride (FeCl₃) solution in nitromethane. A classical percolation phenomenon was observed in the electrical properties of the binary blends, it was smaller than 4 wt.% of P3HT in the blend. Atomic force microscopy and confocal microscopy showed a phase-separated morphology. Variation in the surface morphology of the blends was observed, which was a function of the polymer concentration and the type of insulator polymer used in the blends. The insulator polymer was segregated on the surface of the films and showed pit and island-like topography. The pit and island size changed as a function of the polymer concentration. Optical absorption properties as a function of the P3HT concentration in the undoped and doped state were analyzed. In doped state, the bipolaron bands in the PS/P3HT and PMMA/P3HT blends were observed from a P3HT concentration of 1 wt.% and 3 wt.%, respectively. Finally, the polymers were analyzed by thermogravimetric analysis and infrared spectroscopy.     

γ射线辐照对PA6/PTFE合金吸水与力学性能的影响

为了探讨辐照对尼龙6(PA6)基共混材料吸水性能和力学性能的影响,制备了PA6和聚四氟乙烯(PTFE)共混合金并在室温下进行不同剂量的60Coγ射线辐照.通过吸水率测试、准静态拉伸和弯曲实验以及缺口冲击测试,研究了辐照对PA6/PTFE共混体系吸水性能以及吸收水和辐照剂量对共混合金动静态力学性能的影响.结果表明,辐照过程引发交联反应,共混合金的拉伸强度、拉伸模量和弯曲模量均随辐照剂量的增大而增大,而缺口冲击强度和吸水率则随之减小.吸收水对共混合金缺口冲击强度的影响与合金组分有关.PTFE含量较低时,吸收水抑制PTFE对合金冲击强度的减弱作用;当PTFE的质量分数大于7%时,吸收水反而加剧PTFE对材料冲击强度的减弱效应.此外,PA6/PTFE合金的吸水率随PTFE含量的增加而降低,而弯曲模量则先增后减.     

Processing and characterization of solid and microcellular poly(lactic acid)/polyhydroxybutyrate-valerate (PLA/PHBV) blends and PLA/PHBV/Clay nanocomposites

The morphology, microstructure, tensile properties, and dynamic mechanical properties of solid and microcellular poly(lactic acid) (PLA)/polyhydroxybutyrate-valerate (PHBV) blends, as well as PLA/PHBV/clay nanocomposites, together with the thermal and rheological properties of solid PLA/PHBV blends and PLA/PHBV/clay nanocomposites, were investigated. Conventional and microcellular injection-molding processes were used to produce solid and microcellular specimens in the form of ASTM tensile test bars. Nitrogen in the supercritical state was used as the physical blowing agent in the microcellular injection molding experiments. In terms of rheology, the PLA/PHBV blends exhibited a Newtonian fluid behavior, and their nanocomposite counterparts showed a strong shear-thinning behavior, over the full frequency range. An obvious pseudo-solid-like behavior over a wide range of frequencies in the PLA/PHBV/clay nanocomposites suggested a strong interaction between the PLA/PHBV blend and the nanoclay that restricted the relaxation of the polymer chains. PLA/PHBV/clay nanocomposites possess a higher modulus and greater melt strength than PLA/PHBV blends. The addition of nanoclay also decreased the average cell size and increased the cell density of microcellular PLA/PHBV specimens. As a crystalline nucleating agent, nanoclay significantly improved the crystallinity of PHBV in the blend, thus leading to a relatively high modulus for both solid and microcellular specimens. However, the addition of nanoclay had less of an effect on the tensile strength and strain-at-break.     

ABS改性剂的核壳比对CPVC/ABS共混物性能的影响

采用种子乳液聚合方法在聚丁二烯(PB)上接枝苯乙烯(St)和丙烯腈(AN)单体,合成了一系列不同核壳比的ABS改性剂,将其与氯化聚氯乙烯(CPVC)熔融共混制得CPVC/ABS共混物,研究了ABS核壳比对CPVC/ABS共混物结构与性能的影响.动态力学分析结果表明:CPVC与接枝SAN不相容;扫描电子显微镜发现:ABS...     

自蔓延法制备ZrO2-Y2O3纳米粒子的影响因素

采用自蔓延法制备ZrO2-Y2O3(YSZ)纳米粒子。研究了反应中柠檬酸与硝酸盐比例(c／n)对反应产物的影响以及对纳米晶粒尺寸的影响，并且探讨了分散剂的作用机理，在制备过程中添加分散剂磷酸酯(PE)对YSZ纳米颗粒尺寸的影响及其作用机制。结果表明，反应中柠檬酸与硝酸盐的最佳比例为0．56，此时可获得的晶粒尺寸为12nm；分散剂PE加入量为ZrOCl2质量的2％时，分散效果最好，获得的纳米颗粒团聚最小(30-70nm)。     

The effect of hygrothermal conditions on the fracture toughness of epoxy/poly(styrene-co-allylalcohol) blends

The influence of water content on the fracture toughness of epoxy/poly(styrene-co-allylalcohol) (PScoPA) blends with different amounts of modifier has been investigated. The water ingress has a double consequence: a considerable plasticization effect of the matrix and a significant weakening of the interphase between the matrix and the thermoplastic particles. The addition of thermoplastic modifier reduces, in the aged samples, the deterioration in fracture toughness. Analytical models, based on plastic voids growth around the dispersed phase particles, have been applied with reasonable agreement.     

The surface characteristics of organoclays and their effect on the properties of poly(trimethylene terephthalate) nanocomposites

Biobased materials developed in conjunction with nanotechnology are poised to achieve a significant presence in the world market for polymeric materials. An example of an engineering polymer that can be partially derived from biomass is poly(trimethylene terephthalate). One of its raw materials, 1,3-propanediol, can be derived from corn sugar. In the present study we used a fully petroleum-based resin as an analog to the biobased material. Five organically modified montmorillonite clays were characterized via moisture uptake studies to determine the hydrophilic/hydrophobic nature of their surfaces. Nanocomposites were produced via melt compounding followed by injection molding with 5 wt.% organoclay loading to determine which modification gave the best balance of mechanical and thermal properties. It was found that the tensile modulus increased by up to 35% and the tensile stress at break by up to 50%. The heat deflection temperature of the nanocomposites versus the neat polymer increased by up to 33 °C. From these results, one organoclay was selected for detailed study over a loading range of 0–5 wt.%. The testing revealed that over this range, changes in the mechanical properties may go through a maximum (e.g. strength) or increase/decrease to a plateau (e.g. modulus, elongation at break). X-ray diffraction and transmission electron microscopy were also used to characterize the nature of the organoclay/polymer interaction. Biobased poly(trimethylene terephthalate)/organoclay nanocomposites are expected to exhibit properties similar to the petroleum-based resin.     

Compatibilizing effect of acrylic acid modified polypropylene on the morphology and permeability properties of polypropylene/organoclay nanocomposites

This work dealt with the morphology and permeability properties of polypropylene/organoclay nanocomposites prepared using an acrylic acid grafted polypropylene (PP-g-AA) as compatibilizing agent. Two PP-g-AA containing the same acrylic acid content (6 wt.%) and having different molar masses were tested. The o-MMT content was 0, 1 or 5 wt.% and the PP-g-AA/o–MMT mass ratio was 0/1, 1/1, 2/1 or 5/1. Results of wide angle X-ray scattering (WAXS) and transmission electron microscopy (TEM) showed that without the PP-g-AA, the o-MMT was dispersed in the PP/o-MMT in a micrometer scale, similar to a conventional microcomposite. With the PP-g-AA, the o-MMT was much better dispersed and its interlayers were intercalated and partly exfoliated by the polymer chains. CO₂ permeability values decreased for all samples with the incorporation of the organoclay. The compatibilized samples showed a more significant reduction in CO₂ permeability, up to 50% when compared to the neat PP. In general, the PP-g-AA acted satisfactorily in compatibilizing PP/organoclay nanocomposites. Moreover, samples prepared with the compatibilizer/organoclay ratio of 5/1 had better barrier properties.     

The effect of surface modifications on sisal fiber properties and sisal/poly (lactic acid) interface adhesion

The main aims of this work were to study the effect of surface modifications on sisal fiber properties as well as on fiber/poly (lactic acid) (PLA) interface adhesion. For this purpose, alkali, silane and combination of both treatments were applied to sisal fiber. The effects of treatments on fiber thermal stability, fiber wettability, morphology, tensile properties and on fiber/PLA interfacial shear strength (IFSS) were studied. After treatments IFSS values improved at least 120%, however, tensile strength of sisal fibers decreased. Alkali treatment removed some non-cellulosic components (hemicelluloses, lignin) as confirmed by Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The removal of non-cellulosic materials led to fibrillated and rough morphology as observed by optical microscopy (OM). FTIR spectrum of silane treated fibers showed a band related to silane amino group and contact angle measurements confirmed that fibers became more hydrophobic. All treatments used improved fiber/PLA adhesion.     

The mechanical properties and resistivity of Au/NiCr/Ta multi-layered films on Si-(111) substrate

Au/NiCr/Ta multi-layered metallic films were deposited on Si substrate by magnetron sputtering at different substrate temperatures. The residual stress, hardness and resistivity were investigated as a function of substrate temperature by laser polarization phase shift technique, nanoindentation technique and four point probe method, respectively. The residual stress in as-deposited films at different substrate temperatures was tension with 385 MPa-606 MPa. Nanoindentation tests at shallow indentation depths (h ≤ t/4) where the hardness is reliable for metal films on hard substrate. Au film at deposition temperature 200 °C has the highest hardness 4.2 GPa. The resistivity in the deposited films reached the lowest value 3.1 μΩ.cm at substrate temperature 200 °C. The most interesting facts are that the hardness decreases with increasing residual stress and resistivity increases with increasing residual stress. The relationship of residual stress and resistivity may hint that there is a definite correlation between the mechanical properties and electrical properties in the metallic films.     

Grain size-dependent Mg/Si ratio effect on the microstructure and mechanical/electrical properties of Al-Mg-Si-Sc alloys

Al-Mg-Si-Sc alloys with different Mg/Si ratio (<1.73 in wt.% vs>1.73 in wt.%) and different grain size (coarse grains vs ultrafine grains) were prepared, which allowed to investigate the grain size-dependent Mg/Si ratio effect on the microstructural evolution and concomitantly on the hardness and electrical conductivity when subjected to aging at 200 °C. In the coarse-grained Al-Mg-Sc-Sc alloys, the β″ precipitation within the grain interior and also the precipitation hardening were highly dependent on the Mg/Si ratio, while the electrical conductivity was slightly affected by the Mg/Si ratio. A promoted β″ precipitation was found in the case of Si excess (Mg/Si ratio <1.73), much greater than in the case of Mg excess (Mg/Si ratio>1.73). While in the ultrafine-grained Al-Mg-Si-Sc alloys, the electrical conductivity rather than the hardness was more sensitive to the Mg/Si ratio. The alloy with Si excess displayed electrical conductivity much higher than its counterpart with Mg excess. This is rationalized by the grain boundary precipitation promoted by Si, which reduced the solute atoms and precipitates within the grain interior. Age softening was found in the ultrafine-grained alloy with Si excess, but the ultrafine-grained alloy with Mg excess held the hardness almost unchanged during the aging. The hardness-conductivity correlation is comprehensively discussed by considering the coupling effect of Mg/Si ratio and grain size. A strategy to simultaneously increase the hardness/strength and electrical conductivity is proposed for the Al-Mg-Si-Sc alloys, based on present understanding of the predominant factors on strengthening and conductivity, respectively.     

In-situ hydrothermal crystallization Mg(OH)2 films on magnesium alloy AZ91 and their corrosion resistance properties

Mg(OH)₂ films have been fabricated on magnesium alloy AZ91 substrates by an in-situ hydrothermal method. AZ91 alloy substrates act as both the source of Mg²⁺ ion and the support for the Mg(OH)₂ film in synthetic process. The effect of pH value and hydrothermal treatment time on the morphologies and corrosion resisting properties of Mg(OH)₂ film is studied. The obtained Mg(OH)₂ films are uniform and compact. The adhesion between the films and the substrate is strong due to the in-situ growth process, which enhances their potential for practical applications. Potentiodynamic polarization measurements showed that the Mg(OH)₂ films obtained at pH 10, 3 h exhibits the highest increase in corrosion potential at −0.7097 V and lowest i_corr, which suggests that it is the best effective film in improving the corrosion resistance of AZ91in all obtained films.     

高性能PVC/PSf共混超滤膜的研制——(Ⅰ)稀溶液黏度法测PVC/PSf共混相容性的研究

首次采用稀溶液黏度法(DSV法),通过相对黏度-组成曲线、增比黏度-浓度曲线,以及值对PVC与PS f的相容特性进行了研究。结果表明,PVC/PS f共混体系为部分相容体系,体系相容性随PVC/PS f共混比的增大而增加;溶液浓度和温度对PVC/PS f体系的相容性存在一定的影响。     

Characterisation of the thickness of transition layer and its relation to mechanical properties of polypropylene/poly(ethylene-co-octene) blends

Poly(ethylene-co-octene) (POE) was mixed into polypropylene (PP) by an internal mixer, which was installed on on-line small-angle laser light scattering (SALLS) device. A new parameter called the thickness (d) of transition layer was introduced to describe the compatibility of PP/POE blends in both dynamic and static states. Using the correlation distance, a_c (it was indicative of the dimension of the dispersed phase pellets), d was calculated for the PP/POE blends based on the SALLS theory. The results indicated that the average values of d increased with increasing concentration of dispersed phase and had a maximum value at 40/60(PP/POE) for the blends. And the values of d showed much more violent fluctuation and were much larger at the early stage of mixing, but at a later stage d leveled off and approached to steady state. In addition, the relationships between the thickness of transition layer and mechanical properties were studied. It showed that the notched Izod impact strength and the average values of d of PP/POE blends increased with increasing of POE concentration, while the Young's modulus and flexural modulus decreased. The results indicated that SALLS method was an effective method to deal with diffuse transition layer of PP/POE blends and d was indeed a valid parameter to describe compatibility.     

Influence of oxidized polyethylene wax (OPW) on the mechanical,thermal, morphological and biodegradation properties of PHB/LDPE blends

Blends of poly(β-hydroxybutyrate) (PHB) and low density polyethylene (LDPE) were prepared in proportions of 100/0, 75/25, 50/50, 27/75 and 0/100 (PHB/LDPE wt.%), with and without oxidized polyethylene wax (OPW, 5 wt.%), and the mechanical, thermal (differential scanning calorimetry and melting flow index, morphological (scanning electron microscopy) and biodegradation (aging in simulated soil) properties were evaluated. The addition of OPW increased the tensile strength and Young’s modulus but decreased the elongation at break of the blends. Similarly, OPW increased the T _g of the pure LDPE and enhanced the melt flow index. Scanning electron microscopy showed that OPW reduced the phase separation of LDPE and increased the biodegradation during aging in simulated soil.     

溴掺杂对PEDOT/PSS薄膜性能的影响及机理研究

为改善聚乙撑二氧噻吩∶聚（对苯乙烯磺酸）根阴离子（PEDOT/PSS）薄膜的光学及电学性能,采用共混-旋涂法在石英玻片上制备出溴掺杂的PEDOT/PSS透明导电膜,并就其掺杂导电机理进行了探讨.结果表明：经微量溴掺杂后的PEDOT/PSS薄膜,其透光性能与导电性能均得到提高;质量分数6%溴掺杂条件下,薄膜透光率为95....     

Effect of expanded graphite and modified graphite flakes on the physical and thermo-mechanical properties of styrene butadiene rubber/polybutadiene rubber (SBR/BR) blends

The aim of the present research work is to develop expanded graphite (EG) and isocyanate modified graphite nanoplatelets (i-MG) filled SBR/BR blends, which can substitute natural rubber (NR) in some application areas. The present study investigated the effect of i-MG on the physical, mechanical and thermo-mechanical properties of polybutadiene rubber (BR), styrene butadiene rubber (SBR) and SBR/BR blends in the presence of carbon black (CB). Graphite sheets were modified to enhance its dispersion in the rubber matrices, which resulting in an improvement in the overall physical and mechanical properties of the rubber vulcanizates. Compounds based on 50:50 of BR and SBR with ∼3 wt% nanofillers with CB were fabricated by melt mixing. The morphology of the filled rubber blends was investigated by wide angle X-ray diffraction (WAXD) and high resolution transmission electron microscopic (HR-TEM) analyses. The intercalated and delaminated structures of the nanofiller loaded rubber blends were observed. Scanning electron microscopic (SEM) analysis of the cryo-fractured surfaces of the rubber compounds showed more rough and tortuous pathway of the fractured surfaces compared to the fractured surfaces of the only CB loaded rubber composites. Filled rubber compounds exhibit increase in the ΔS (torque difference) value, reduced scorch and cure time compared to their respective controls. Dynamic mechanical thermal analysis (DMTA) of the filled rubber compounds shows an increase in the storage modulus compared to the controls. Isocyanate modified graphite nanoplatelets (i-MG) containing rubber compounds in the presence of CB showed an increase in the mechanical, dynamic mechanical, hardness, abrasion resistance and thermal properties compared to the alone CB filled rubber vulcanizates.