Morphology and Properties of PP In-reactor Alloys Prepared with a MgCl2/TiCl4/Diisobutyl Phthalate/Phosphate Tris-methylphenyl Ester Catalyst System

A series of polypropylene(PP)/poly(ethylene-co-propylene) in-reactor alloys with different ethylene contents was prepared through a two-stage polymerization process using a MgCl₂/TiCl₄/diisobutyl phthalate/phosphate tris-methylphenyl ester catalyst system. The ethylene content, particle shape, fractured surface, and glass-transition temperature(T_g) of the obtained PP in-reactor alloys were characterized by means of nuclear magnetic resonance, scanning electron microscopy(SEM), and dynamic mechanical analysis(DMA). The ethylene content of the PP alloys increased from 2.34% to 26.69% when the propylene/ethylene feed ratio was increased from 66/34 to 54/46(molar ratio). Morevoer, the increment in ethylene content increased the notched Izod impact strength of the resulting PP alloys. The impact strength of the PP alloy with an ethylene content of 26.69% was 55.8 kJ/m², which is 12.7 times that of isotactic polypropylene. The results of DMA and SEM analysis reveal that ethylene-propylene random copolymer(EPR) in the PP alloy has a low T_g of ca. -50 ℃ and a high interface compatibility with the PP matrix. The excellent impact performance of the PP alloy can be attributed to the uniform dispersal of EPR in the alloy particles and PP matrix.     

Rheology of polypropylene/poly(ethylene-co-propylene) in-reactor alloy

The interfacial adhesion and molecular structure of an in-reactor polypropylene/ethylene propylene rubber alloy were studied with respect to the rheological behavior and final properties of the alloy. The polymer alloys have similar structural parameters but different impact properties. The samples were characterized by gel permeation chromatography, thermal analysis, rheological analysis and mechanical testing. Fractionation of samples showed that the quantities of components are the same. Gel permeation chromatography results showed that molecular weight distribution of all components were similar. Thermal analysis results showed that the crystal size of two samples was the same but the crystal contents were different. In studying the impact strength, it was revealed that a large difference exists between the two samples. The small amplitude oscillation rheometry indicates that the rheological parameters have a glaring difference in both samples that can be an evidence of interfacial adhesion in the in-reactor alloys having so many similar structural parameters.     

Tensile,fatigue and thermomechanical properties of poly(ethylene-co-vinyl acetate) nanocomposites incorporating low and high loadings of pre-swelled organically modified montmorillonite

The production of exfoliated polymer/clay based nanocomposites is crucial to obtain an actual benefit of nanoscale reinforcement in the polymer matrix. In this project, the production of exfoliated polymer/clay nanocomposite was aimed through the use of poly(ethylene-co-vinyl acetate) (EVA) copolymer as matrix and organically modified montmorillonite (O-MMT) as nanofiller. The research work involved the use of pre-swelled technique through magnetic stirring and ultra-sonication to obtain more readily exfoliated and dispersed O-MMT nanofiller for EVA nanocomposite production. The aims were to allow the improvement in O-MMT exfoliation and dispersion when the nanofiller was incorporated in high loading (greater than 3 wt%) into the copolymer. The original and pre-swelled O-MMTs were employed to produce the EVA/O-MMT nanocomposites with 1, 3, 5, 7 and 9 wt% nanofiller by melt compounding technique. The results of TEM, tensile and fatigue tests, XRD, FTIR and DMA proved that the pre-swelling technique applied on the O-MMT before melt compounding with the EVA copolymer can bring positive impact to the performance of the nanocomposite. As opposed to the original O-MMT, the pre-swelled O-MMT has the ability to improve the tensile toughness, cyclic stability and storage modulus of the EVA copolymer even when high O-MMT loading (7 wt %) was employed. Improvement in the EVA - O-MMT interactions in the nanocomposite system was postulated to be the main reason for such observations.     

Preparation of metallic fuel rodlets for irradiation testing in the HANARO research reactor

U–10 wt% Zr fuel rodlets, which will be irradiated in the HANARO research reactor in order to evaluate the irradiation performance of metallic fuel and validate the in-reactor behavior, were prepared through determined fabrication processes. Injection casting technology was applied to produce U–10Zr fuel slugs, and sodium melt and a bonding process were conducted to bond a fuel slug to the fuel cladding. To seal the end plug to the fuel cladding tube, a gas tungsten arc welding technique was adopted. Based on the results of these experiments, sodium-cooled fast reactor fuel rodlets for irradiation testing in the HANARO research reactor have been soundly fabricated.     

Structure and morphology of polypropylene/poly(ethylene-co-propylene) in situ blends synthesized by spherical Ziegler-Natta catalyst

Polypropylene/poly(ethylene-co-propylene) (iPP/EPR) in situ blends of different composition were synthesized by spherical Ziegler-Natta catalyst, and were fractionated into three portions: the random copolymer (EPR), the block copolymer, and the iPP matrix. The EPR fraction was characterized by ¹³C NMR, and the block copolymer fraction was characterized by crystalline segregation and differential scanning calorimetry analysis. The blends showed bi-phase structure with EPR existing in the dispersed phase. Increasing EPR in the blends resulted in increase of the number and diameter of the EPR particles, but there is an upper limit for the particle number. There were only highly irregular spherulites or tiny crystallites in the isothermal crystallized blends. The morphology of the impact fracture surfaces of the blends clearly showed that they were fractured in ductile fashion. There was strong dependence of impact strength of the blends on their morphology, and the sequence distributions of the EPR and segmented copolymer fractions also markedly influenced the mechanical properties.     

橡胶相具有交联结构的新型抗冲聚丙烯合金

利用具有"颗粒反应器技术(RGT)"特征的Ziegler-Natta催化剂进行丙烯多相共聚(丙烯均聚+乙烯/丙烯无规共聚),通过在乙丙共聚阶段引入双烯烃单体1,9-癸二烯,使乙丙共聚物在聚合的同时实现交联,制备了新型抗冲聚丙烯合金.聚合反应结果表明,1,9-癸二烯可参与乙丙共聚,同时对聚合反应速率和共聚物组成影响较小;1,9-癸二烯使乙丙共聚物发生支化/部分交联,合金聚合物的熔体流动速率在引入1,9-癸二烯后显著降低,且凝胶含量随1,9-癸二烯用量的增加而增大.形态研究结果表明,乙丙共聚物的交联显著降低了其在聚丙烯基体中的分散尺度,提高了分散均匀性,分散相粒径随支化/交联程度提高而减小.力学性能测试结果表明,乙丙共聚物的交联使合金聚合物在保持较高韧性的同时显著提升了刚性,有利于实现抗冲聚丙烯合金的刚韧平衡.     

聚丙烯“催化合金”组成对结晶行为的影响

用示差扫描量热仪(DSC)和偏光显微镜(POM)研究了聚丙烯“催化合金”(PP-cats)组成对等温结晶行为与动力学的影响,并与等规聚丙烯(iPP)进行比较.结果表明,与纯PP相比较,PP-cats的平衡熔融温度明显下降,表明PP-cats中作为主要组分的丙烯均聚物和乙丙无规共聚物之间存在较强的相互作用.PP-cats的结晶初期动力学可用Avrami模型很好地描述,结晶过程均为预先成核和三维生长方式.PP-cats的结晶速率随体系中乙丙共聚物含量的增加而增大,而PP-cats的晶体生长速率随体系中乙丙共聚物含量的增加而减小.由于PP-cats熔体的粘度远高于纯PP,使得PP-cats中PP分子链运动能力降低,导致了PP-cats较低的晶体生长速率.此外,与纯PP相比,PP-cats的成核密度大幅度提高,被认为是PP-cats具有快的结晶速率的主要原因.     

Characterization of monomer sequence structure distribution of poly(1-butene)/poly(propylene-co-butene) in-reactor alloys through 13C-NMR

In situ FTIR testing demonstrated that crystallization of novel poly(1-butene)/poly(propylene-co-butene) in-reactor alloys from melt shows thermodynamic stable Form I directly rather than general reported unstable crystal Form II. In order to make clear this phenomenon, the microstructure and monomer sequence distribution of the as-obtained poly(1-butene)/poly(propylene-co-butene) in-reactor alloys was determined by ¹³C-NMR. The raw alloy was separated by fractional dissolution to five grades. The characterization of raw alloys and different grades demonstrates that propylene monomer unit distributes in a form of isolated or segmented along poly(1-butene) molecular chains. The fractional dissolution of the selected alloy indicates that chain structure changes gradually with fractional solvent. The number average sequence length of propylene and 1-butene unit has been calculated. The number average sequence length and distribution could help us to study the crystallization and transformation clearly. From the results of in situ FTIR and NMR, the random distribution of the propylene unit with certain content in the as-obtained alloys play role to accelerate the crystallization transformation.     

i-PP/EPR REACTOR ALLOY PREPARED THROUGH ETHYLENE/PROPYLENE SLURRY COPOLYMERIZATION CATALYZED BY METALLOCENE SUPPORTED iPP PARTICLES

i-PP/m-EPR reactor alloy were prepared through ethylene/propylene slurry copolymerization catalyzed by metallocene(rac-Et(Ind)_2ZrCl_2)supported on porous iPP particles.Polar monomer(dihydromyrcene alcohol)treated with triethyaluminum was added in the preparation of porous iPP particles to introduce hydroxyl groups and thus enhance the ability for chemically supporting the metallocene catalyst.The effects of MAO/Zr ratio and monomer composition in feed on the reaction activity and property of polymer wer...     

The orientation of the dispersed phase and crystals in an injection-molded impact polypropylene copolymer

The orientation of the dispersed phase and crystals in the injection-molded bar of an impact polypropylene copolymer (IPC) containing isotactic polypropylene (iPP), ethylene-propylene rubber (EPR) and a β-nucleating agent (β-NA) were studied simultaneously. In the IPC, iPP and EPR act as the matrix and dispersed phase, respectively. The EPR is amorphous and the iPP is crystallizable in α- and β-crystalline forms in the presence of the β-NA. The orientation and orientation distribution for both of the EPR phase and the iPP crystals, as well as the crystallization behavior of iPP, were investigated by two-dimensional wide-angle X-ray diffraction (2D-WAXD), two-dimensional small-angle X-ray scattering (2D-SAXS), scanning electron microscope (SEM) and differential scanning calorimetry (DSC). The results of the experiment show that orientation exists for both the EPR phase and the iPP crystals. But their orientation distribution manifests an opposite tendency. The EPR phase was observed to be highly oriented in the core layer but the orientation of the iPP crystals was weakened gradually from skin to core. The difference in the orientation behavior between the EPR phase and the iPP crystals reflects the distinct response of the micrometer-scale EPR particles and nanometer-scale iPP chains upon the flow field and temperature gradient in the mold. The diffraction geometry of the β-crystals has also been discussed in detail. The observations in this study may shed light on the study in the structure and property relationship for the IPC injection-molded products.     

In situ synchrotron SAXS/WAXD studies during melt spinning of modified carbon nanofiber and isotactic polypropylene nanocomposite

The structural development of a nanocomposite, containing 95 wt% isotactic polypropylene (iPP) and 5 wt% modified carbon nanofiber (MCNF), during fiber spinning was investigated by in situ synchrotron small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) techniques. The modification of carbon nanofibers (CNFs) was accomplished by a chemical surface treatment using in situ polymerization of olefin segments to enhance its compatibility with iPP, where the iPP/MCNF nanocomposite was prepared by twostep blending to ensure the dispersion of MCNF. X-ray results showed that at low spin-draw ratios, the iPP/MCNF nanocomposite fiber exhibited much higher iPP crystalline orientation than the control iPP fiber. At higher spin-draw ratios, the crystalline orientation of the nanocomposite fiber and that of the pure iPP fiber was about the same. The crystallinity of the composite fiber was higher than that of the control iPP fiber, indicating the nucleating effect of the modified carbon nanofibers. The nanocomposite fiber also showed larger long periods at low spin-draw ratios. Measurements of mechanical properties indicated that the nanocomposite fiber with 5 wt% MCNF had much higher tensile strength, modulus and longer elongation to break. The mechanical enhancement can be attributed to the dispersion of MCNF in the matrix, which was confirmed by SEM results.Dedicated to Prof. E D. Fischer on his 75th birthday.     

全同立构聚丙烯的晶片形态

本文应用光学显微镜,扫描和透射电子显微镜从三种不同层次的结构水平上研究了α和β两种晶型的全同立构聚丙烯的球晶和晶片形态结构,特别是应用四氧化钌染色技术直接观察到两种不同晶型聚丙烯球晶中单独分离的晶片形态.结果表明,不同晶型聚丙烯球晶的形态是不同的,其所呈现的性质与其内部晶片结构的排列特征相对应.同时研究了两种晶型聚丙烯在熔体拉伸结晶条件下生成的晶片形态,倾向于相同的取向晶片结构.电子衍射数据证明了,β型聚丙烯在拉伸取向结晶时将转变为α晶型.     

等规聚丙烯/二元乙丙橡胶合金相分离对结晶动力学的影响

用小角激光光散射(SALLS)、相差显微镜(PCM)、示差扫描量热仪(DSC)和偏光显微镜(POM)研究了聚丙烯/二元乙丙橡胶(iPP/EPR)共混体系的相分离行为和等温结晶行为.发现iPP/EPR(50/50,W/W)发生的液-液相分离遵循spinodal机理.通过Cahn-Hilliard方程求得了不同实验温度下iPP/EPR的表观扩散系数(Dapp)以及spinodal温度(Ts).考察了不同相分离程度的iPP/EPR体系结晶动力学,发现延长相分离时间(tps)或提高相分离温度(Tps)均会导致半结晶时间(t1/2)增大,即结晶速率降低.这被归于EPR成核作用的降低.动力学分析结果表明Avrami模型适用于描述该体系的等温结晶过程,其结晶机理基本不受相分离程度的影响,结晶均以瞬时成核和三维生长为主.     

Fabrication of Non‐enzymatic Electrochemical Glucose Sensor Based on Pd−Mn Alloy Nanoparticles Supported on Reduced Graphene Oxide

Mixed metals alloy nanoparticles supported on carbon nanomaterial are the most attractive candidates for the fabrication of non‐enzymatic electrochemical sensor with enhanced electrochemical performance. In this study, palladium‐manganese alloy nanoparticles supported on reduced graphene oxide (Pd?Mn/rGO) are prepared by a simple reduction protocol. Further, a novel enzyme‐free glucose sensing platform is established based on Pd?Mn/rGO. The successful fabrication of Pd?Mn alloy nanoparticles and their attachment at rGO are thoroughly characterized by various microscopic and spectroscopic techniques such as XRD, Raman, TEM and XPS. The electrochemical activity and sensing features of designed material towards glucose detection are explored by amperometric measurments in 0.1 M NaOH at the working voltage of ?0.1 V. Thanks to the newly designed Pd?Mn/rGO nanohybrid for their superior electrorochemical activity towards glucose comprising the admirable sensing features in terms of targeted selectivity, senstivity, two linear parts and good stability. The enhanced electrochemical efficacy of Pd?Mn/rGO electrocatalyst may be credited to the abundant elecrocatalytic active sites formed during the Pd?Mn alloying and the electron transport ability of rGO that augment the electron shuttling phenomenon between the electrode material and targeted analyte.     

聚丙烯釜内合金性能及微观形态

通以磷酸酯化合物为内给电子体的球型齐格勒纳塔催化剂,在本体-气相聚合装置上制备了己烷可溶级分含量不同的高熔融指数的聚丙烯釜内合金,考察了其微观形态与力学性能。 结果表明,随己烷可溶组分含量的增加,冲击强度明显增加, 冲击强度从4.4 kJ/m2增加至52.7 kJ/m2,弯曲强度和拉伸强度略有减小。 拉伸强度从28.6 MPa下降至19.5 MPa,弯曲强度从37.2 MPa下降至21.5 MPa。 扫描电子显微镜照片显示,橡胶相均匀分散在聚丙烯基体中形成“核-壳”结构。     

锂离子电池SiAg复合材料研究

应用机械合金化法制备了两种不同组分的Si-Ag复合材料.扫描电镜(SEM)、X射线衍射(XRD)、充放电测试和循环伏安法对该材料的微观形貌、相组成及电化学性能.研究表明,组成原子比为1∶1的复合材料具有很好的循环稳定性和可逆性,在0.2mA·cm-2的电流密度下,经50周循环后可逆容量仍保持300mAh·g-1.实验发现,借助充放电控制,即可有效提高合金材料的循环性能.     

Preparation of polymer nanocomposites with enhanced mechanical properties using hybrid of graphene and partially wrapped multi-wall carbon nanotube as nanofiller

Triblock copolymer of poly(p-dioxanone) and polyethylene glycol end-capped with pyrene moieties ((Py-PPDO)₂-b-PEG) was synthesized and used as modifier for multi-wall carbon nanotubes (MWCNTs). Nano-aggregates ((Py-PPDO)₂-b-PEG@MWCNTs) with shish-kebab like partially wrapped morphology and very good stability were obtained by incorporating the copolymer with MWCNTs. The bare MWCNT sections of (Py-PPDO)₂-b-PEG@MWCNTs were able to induce π-π interactions with graphene (GE) and resulted in a novel GE/(Py-PPDO)₂-b-PEG@MWCNTs hybrid. The dispersity of GE in solution or polymer matrix was therefore greatly improved. The PCL nanocomposite films using GE/(Py-PPDO)₂-bPEG@MWCNTs as hybrid nanofiller exhibited obviously improved mechanical properties especially at very low hybrid nanofiller content. The influence of the nanofiller content and feed ratio of GE/MWCNTs on the mechanical properties of composites films was evaluated. When the feed ratio of GE to MWCNTs is 2:8 and the total loading of nanofiller is only 0.01 wt%, the tensile strength of the composite film increased by 163% and the elongation at break increased by 17% compared to those of neat PCL. These results can be attributed to fine dispersion of the nanofillers in PCL matrix and the hybrid interactions between GE and MWCNTs. Therefore, this work provides a novel method for preparing polymer nanocomposites with high mechanical performance and low nanofiller loading.     

Free-standing poly(L-lactic acid) nanofilms loaded with superparamagnetic nanoparticles

Freely suspended nanocomposite thin films based on soft polymers and functional nanostructures have been widely investigated for their potential application as active elements in microdevices. However, most studies are focused on the preparation of nanofilms composed of polyelectrolytes and charged colloidal particles. Here, a new technique for the preparation of poly(l-lactic acid) free-standing nanofilms embeddidng superparamagnetic iron oxide nanoparticles is presented. The fabrication process, based on a spin-coating deposition approach, is described, and the influence of each production parameter on the morphology and magnetic properties of the final structure is investigated. Superparamagnetic free-standing nanofilms were obtained, as evidenced by a magnetization hysteresis measurement performed with a superconducting quantum interference device (SQUID). Nanofilm surface morphology and thickness were evaluated by atomic force microscopy (AFM), and the nanoparticle dispersion inside the composites was investigated by transmission electron microscopy (TEM). These nanofilms, composed of a biodegradable polyester and remotely controllable by external magnetic fields, are promising candidates for many potential applications in the biomedical field.     

Microhardness-structure correlation of iPP/EPR blends: influence of molecular weight and EPR particle content

The influence of molecular weight on the mechanical properties of isotactic poly(propylene) (iPP) and iPP blended with ethylene-propylene copolymers has been investigated by means of the microhardness technique. The hardness (H) of iPP is shown to slightly decrease with increasing molecular mass, within the range of molecular weights investigated. The H-decrease is correlated to a loss of crystallinity as the average molecular weight increases. On annealing, the mechanical properties are enhanced as a consequence of an increase in both, the degree of crystallinity and the crystalline lamellar thickness. A value of H ^∞ _c for iPP crystals of infinite thickness in the α-form is proposed for the first time. The inclusion of EPR particles in the iPP matrix softens the material. This result could be explained in terms of an increase in the basal surface free energy of the iPP crystals with increasing amount of rubber content. Received: 2 February 1998 Accepted: 11 May 1998     

Microbiosensors based on DNA modified single-walled carbon nanotube and Pt black nanocomposites

Glucose and ATP biosensors have important applications in diagnostics and research. Biosensors based on conventional materials suffer from low sensitivity and low spatial resolution. Our previous work has shown that combining single-walled carbon nanotubes (SWCNTs) with Pt nanoparticles can significantly enhance the performance of electrochemical biosensors. The immobilization of SWCNTs on biosensors remains challenging due to the aqueous insolubility originating from van der Waals forces. In this study, we used single-stranded DNA (ssDNA) to modify SWCNTs to increase solubility in water. This allowed us to explore new schemes of combining ssDNA-SWCNT and Pt black in aqueous media systems. The result is a nanocomposite with enhanced biosensor performance. The surface morphology, electroactive surface area, and electrocatalytic performance of different fabrication protocols were studied and compared. The ssDNA-SWCNT/Pt black nanocomposite constructed by a layered scheme proved most effective in terms of biosensor activity. The key feature of this protocol is the exploitation of ssDNA-SWCNTs as molecular templates for Pt black electrodeposition. The glucose and ATP microbiosensors fabricated on this platform exhibited high sensitivity (817.3 nA/mM and 45.6 nA/mM, respectively), wide linear range (up to 7 mM and 510 μM), low limit of detection (1 μM and 2 μM) and desirable selectivity. This work is significant to biosensor development because this is the first demonstration of ssDNA-SWCNT/Pt black nanocomposite as a platform for constructing both single-enzyme and multi-enzyme biosensors for physiological applications.