Melt‐flow‐induced phase morphologies of a high‐density polyethylene/poly(ethylene‐co‐1‐octene) blend

A blend of high‐density polyethylene and an elastomeric poly(ethylene‐co‐1‐octene) resin, containing 25 mol % octene and long‐chain branching, was phase‐separated in the melt under quiescent conditions. After melt flow, the blend had fine globular or interconnected phase morphologies that were interpreted as originating from the various stages of coarsening after liquid–liquid phase separation through spinodal decomposition. It was inferred that the miscibility of the blend was enhanced under melt flow. After cessation of flow, concurrent liquid–liquid and solid–liquid phase separation took place, resulting in the formation of an interpenetrating morphology comprising amorphous polyethylene, copolymer, and crystalline polyethylene. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 380–389, 2001     

氯化聚丙烯乳液的研究进展

氯化聚丙烯乳液是水基聚烯烃专用涂料的重要组成部分。本文综述了它的组成及其制备方法，并对其前景进行了展望。     

Metallocene based polyolefin: a potential candidate for the replacement of flexible poly (vinyl chloride) in the medical field

A comparative assessment of the performance properties of metallocene polyolefin (m‐PO) with those of plasticized poly (vinyl chloride) (pPVC) and ethylene vinyl acetate (EVA) copolymer having 18% vinyl acetate content (EVA‐18), the two common polymers used for flexible medical products, is carried out. The preliminary evaluation of the processability, mechanical properties, and thermal stability of the new material, m‐PO is described. The processability parameters like mixing torque and melt viscosity of m‐PO are found to be comparable with those of pPVC and EVA‐18. Mechanical properties such as tensile strength, elongation at break, and tear strength (TS) of m‐PO are much higher than that of pPVC and EVA‐18. Thermo gravimetric analysis (TGA) indicates that the thermal degradation of m‐PO takes place only at temperatures above 340°C and can be processed at 170°C without much damage. Oxygen and carbon dioxide permeabilities of m‐PO at three different temperatures (10, 25, and 40°C) are evaluated and compared with those of pPVC and EVA‐18. It could be seen that the permeabilities of both the gases for m‐PO at three temperatures were lower than those of pPVC and EVA. Biological evaluation of m‐PO is carried out by assessing its cytotoxicity, hemolytic property, and blood clotting initiation. The cytotoxicity studies indicate that m‐PO is non‐toxic to the monolayer of L929 mammalian fibroblast cell lines on direct contact or the exposure of its extract. Non‐hemolytic property of m‐PO by direct contact as well as test on extract is revealed both in static and in dynamic conditions. Blood clotting time experiments indicate that the initiation of blood clotting due to m‐PO is faster than that of pPVC and EVA‐18. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis of poly(ethylene‐co‐vinyl alcohol)‐g‐polystyrene graft copolymer and their applications for ordered porous film and compatibilizer

A series of new functional poly(ethylene‐co‐vinyl alcohol)‐g‐polystyrene graft copolymers (EVAL‐g‐PS) with controlled molecular weight (M_n = 38,000–94,000 g mol^?1) and molecular weight distribution (M_w/M_n = 2.31–3.49) were synthesized via a grafting from methodology. The molecular structure and component of EVAL‐g‐PS graft copolymers were confirmed by the analysis of their ¹H NMR spectra and GPC curves. The porous films of such copolymers were fabricated via a static breath‐figure (BF) process. The influencing factors on the morphology of such porous films, such as solvent, temperature, polymer concentration, and molecular weight of polymer were investigated. Ordered porous film and better regularity was fabricated through a static BF process using EVAL‐g‐PS solution in CHCl₃. Scanning electron microscopy observation reveals that the EVAL‐g‐PS graft copolymer is an efficient compatibilizer for the blend system of low‐density polyethylene/polystyrene. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 516–524     

Dynamic rheological characterization of polyamide/modified polyolefin laminates

 In this work dynamic rheological and peel strength measurements on laminates of polyamide and several modified polyolefins were made to evaluate the interfacial compatibilization phenomena. The polyolefins used were a low-density polyethylene, without any treatment and γ-ray irradiated in air, and two copolymers, an ethylene–tert-butyl acrylate–acrylic acid terpolymer and a partially neutralized ethylene–methacrylic acid copolymer containing sodium cations. Multilayer structures containing different amounts of both interfacial surface and volume fraction were studied. Relationships between viscoelastic functions and composition were used to analyze the effect of bulk and surface modification in the polyolefins at the interface with the polyamide. The results show that dynamic rheological measurements of stratified polymers can be used as a tool to investigate interfacial activity in multiphase systems. Received: 2 January 1998/Accepted: 21 March 1998     

Living copolymerization of ethylene with norbornene mediated by heteroligated (Salicylaldiminato)(β‐enaminoketonato)titanium catalysts

Three heteroligated (salicylaldiminato)(β‐enaminoketonato)titanium complexes [3‐Bu^t‐2‐OC₆H₃CH?N(C₆F₅)][(p‐XC₆H₄)N?C(Bu^t)CHC(CF₃)O]TiCl₂ ( 3a : X = F, 3b : X = Cl, 3c : X = Br) were synthesized and investigated as the catalysts for ethylene polymerization and ethylene/norbornene copolymerization. In the presence of modified methylaluminoxane as a cocatalyst, these unsymmetric catalysts exhibited high activities toward ethylene polymerization, similar to their parallel parent catalysts. Furthermore, they also displayed favorable ability to efficiently incorporate norbornene into the polymer chains and produce high molecular weight copolymers under the mild conditions, though the copolymerization of ethylene with norbornene leads to relatively lower activities. The sterically open structure of the β‐enaminoketonato ligand is responsible for the high norbornene incorporation. The norbornene concentration in the polymerization medium had a profound influence on the molecular weight distribution of the resulting copolymer. When the norbornene concentration in the feed is higher than 0.4 mol/L, the heteroligated catalysts mediated the living copolymerization of ethylene with norbornene to form narrow molecular weight distribution copolymers (M_w/M_n < 1.20), which suggested that chain termination or transfer reaction could be efficiently suppressed via the addition of norbornene into the reaction medium. Polymer yields, catalytic activity, molecular weight, and norbornene incorporation can be controlled within a wide range by the variation of the reaction parameters such as comonomer content in the feed, reaction time, and temperature. ©2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6072–6082, 2009     

NMR Characterization of Ethylene/Propylene Copolymers and Propylene Impact Copolymers from MgCl2/TiCl4/ID+AlR3/ED Catalytic Systems

Summary: The aim of this work was to study the comonomer distribution and the chemical composition distribution generated by different Ziegler-Natta (ZN) systems (different internal donors, ID, dicyclopentadienyl-dimethoxy silane, D donor, as the external donor) and to define the potentialities of different IDs to produce improved heterophasic copolymers (HECO). A methodology to quantify the amount of ethylene-propylene copolymer (EP) portion in ZN-HECO and ethylene content of the EP portion by ¹³C-NMR was established. By using this method, it was possible to analyze the composition of ZN-HECO obtaining results comparable to those obtained with a more complex fractionation technique.     

Effect of the Work Expended on Mixing and Extrusion on the Properties of Thermoplastic Elastomer Compounds

The effect of the processing parameters of thermoplastic elastomer compounds on their properties is studied. The compounds consist of ethylene-propylene rubber and high- or low-density polyethylene (HDPE or LDPE) mixed with extenders in equal amounts. The variations in the degree of crystallinity under different mixing modes are examined by means of differential scanning calorimetry. The variations in the molecular weight distribution (MWD) of polymeric constituents of the compounds are estimated based on the results of rheological tests. An increase in the mixing and extrusion rates affects, up to certain limits, the mechanical properties positively. The optimum preparation modes for HDPE- and LDPE-based compounds are different. A noticeable mechanical destruction of HDPE-based compounds, estimated from the MWD parameters, occurs when the work of mixing exceeds 3.4 kJ/g and is accompanied by cross-linking. Up to 7.1 kJ/g, the work of mixing improves the properties of LDPE-based compounds. The extrusion effects do not smooth out the mixing effects — both these effects add up.     

The Changes of Microstructure and Physical Properties of Isotactic Polypropylene/β Nucleation Agent/Polyolefin Elastomer Induced by Annealing Following Processing

Blends of isotactic polypropylene (iPP)/β nucleation agent (β-NA)/polyolefin elastomer (POE) were prepared by injection molding. The microstructure and mechanical properties of these blends before and after being annealed at various temperatures and times were studied. It was found that annealing simultaneously increased the tensile strength and impact strength. As known, the degree of orientation decreased from the skin layer to the core layer. The orientation of all layers decreased with the increase of annealing temperature and time. The results showed that annealing gave rise to chain rearrangement in both the crystalline and POE phases which, we suggest, played a crucial role in determining the mechanical properties of the blends.