Summary: The present communication reports the first use of electron tomography in reconstructing the three‐dimensional morphology in thermoplastic elastomer blends. The blends investigated were dynamically vulcanized blends of ethylene‐propylene‐diene (EPDM) rubber/poly(propylene)/oil and polystyrene‐block‐(ethylene‐co‐butylene)‐block‐polystyrene (SEBS)/poly(propylene)/oil. An easy identification of blend morphology could be carried out at blend compositions, where conventional transmission electron microscopic imaging gives misleading information. This technique gives a higher resolution than any other microscopic technique, and is applicable to blends with dispersed as well as co‐continuous morphologies.
Example of a tomographic model of partially co‐continuous SEBS phases in a SEBS/PP/oil thermoplastic blend. Only the contours of the SEBS phase are shown. 相似文献
Several novel poly(propylene)‐graft‐poly(ethylene‐co‐propylene) copolymers with isotactic poly(propylene) (PP) backbones and ethylene/propylene rubber (EPR) branches were synthesized. The thermomechanical properties of these samples were investigated using a dynamic mechanical analyzer. There appeared to be a critical EPR molecular weight above which a two‐phase system developed with EPR domains dispersed in a PP matrix. This domain formation gave an enhanced loss modulus compared to a commercial high impact PP product below 40°C. 相似文献
In this study, a series of styrene‐b‐ethylene‐co‐butylene‐b‐styrene copolymer (SEBS)/polypropylene (PP)/oil blends with different kinds of oil composition was developed through melt blending. The effect of oil with different composition and properties on its phase equilibrium and “redistribution” in multiphasic SEBS elastomer was systematically studied for the first time. Moreover, an integral influencing mechanism of oil composition on the structure and properties of SEBS/PP/oil blends was also put forward. The mineral oil was mainly distributed in ethylene/butylene (EB)/PP phase, which greatly enhanced the processing flowability of SEBS/PP/oil blends. With increasing oil CN content, a redistribution of oil appeared and excess naphthenic oil (NO) entered the interphase of soft and hard phases. The dynamic mechanical thermal analysis (DMTA) analysis indicated that the polystyrene (PS) phase was plasticized, which also helped to improve the processing fluidity of blends. However, the plasticizing of physical cross‐linking point PS resulted in a decrease in mechanical strength and thermal stability. Small‐angle X‐ray scattering (SAXS) and transmission electron microscope (TEM) results showed that PS phase (45 nm to 55 nm) cylindrically distributed in EB/PP/oil matrix, the excess NO in the interphase enlarged the distance between PS phase and widen the escape channel for oil migration. At over 45% oil CN content, the electron density difference between soft and hard phases reduced to the minimum, same as TgPS, indicating a deeper plasticizing effect. The PS phase swelled and exhibited elastic behavior; thus, the force could be uniformly transferred between two phases. Importantly, a recover in strength and thermal stability was observed in O‐5 blend. This work significantly filled the gap of studies in oil‐extended thermoplastic elastomers (TPEs), exhibiting great theoretical guiding significance and application value. 相似文献
The morphology, crystallization behavior, and properties of an impact-modified polypropylene (PP) copolymer with or without
sodium benzoate were investigated. The contents of ethylene–propylene rubber (EPR) in the reactor-made PP copolymer is about
15 wt%. For comparison, blends of PP and EPR containing the same EPR composition were prepared by melt-mixing. Morphological
studies by scanning probe microscopy indicated that the impact-modified copolymer consists of three different phases, i.e.,
polyethylene, PP, and EPR phases, which is considerably different from the morphology of the conventional PP/EPR blend of
the corresponding composition. The impact-modified PP copolymer exhibited a higher crystallization rate in terms of the lower
crystallization half-time and thus higher thermal and mechanical properties, such as impact strength and hardness, than the
PP/EPR blend did. The addition of sodium benzoate as a nucleating agent to the copolymer increased the crystallization rate
and the mechanical properties.
Received: 4 June 2001 Accepted: 31 October 2001 相似文献
We report the influence of polyelectrolyte (PE) multilayer films prepared from poly(styrene sulfonate)-poly(acrylic acid) (PSS-PAA) blends, deposited in alternation with poly(allylamine hydrochloride) (PAH), on film wettability and the adsorption behavior of the protein immunoglobulin G (IgG). Variations in the chemical composition of the PAH/(PSS-PAA) multilayer films, controlled by the PSS/PAA blend ratio in the dipping solutions, were used to systematically control film thickness, surface morphology, surface wettability, and IgG adsorption. Spectroscopic ellipsometry measurements indicate that increasing the PSS content in the blend solutions results in a systematic decrease in film thickness. Increasing the PSS content in the blend solutions also leads to a reduction in film surface roughness (as measured by atomic force microscopy), with a corresponding increase in surface hydrophobicity. Advancing contact angles (theta) range from 7 degrees for PAH/PAA films through to 53 degrees for PAH/PSS films. X-ray photoelectron spectroscopy measurements indicate that the increase in film hydrophobicity is due to an increase in PSS concentration at the film surface. In addition, the influence of added electrolyte in the PE solutions was investigated. Adsorption from PE solutions containing added salt favors PSS adsorption and results in more hydrophobic films. The amount of IgG adsorbed on the multilayer films systematically increased on films assembled from blends with increasing PSS content, suggesting strong interactions between PSS in the multilayer films and IgG. Hence, multilayer films prepared from blended PE solutions can be used to tune film thickness and composition, as well as wetting and protein adsorption characteristics. 相似文献
The morphology and thermal behaviour of polypropylene/polyamide 6 (PP/PA6), polypropylene/copolymer ethylene propylene diene (PP/PEBAX) and polypropylene/rigid polyurethane (PP/PUR) blends compatibilised with polypropylene-graft-maleic anhydride (PP-g-MA) were studied using scanning electron microscopy and thermogravimetric analyses. The study focuses on the influence of different blends obtained by mixing a thermoplastic, thermoplastic elastomer or thermoset with PP, compatibilised with PP-g-MA. The compatibilising effect of PP-g-MA in an immiscible PP/PA6 blend induces a homogeneous dispersion due to interfacial adhesion. For the PP/PEBAX and PP/PUR binary blends studied slight changes in the morphology were observed with a continuous phase but the PEBAX or PUR domains remained in the PP matrix. The deconvolution of the TGA curve permitted an evaluation of the decomposition stage of the undiluted and blend systems. Thermal stability is slightly influenced by the position of the maximum decomposition rate temperature of the first derivative thermogravimetric curve (DTG). However, the DTG curve profile remains consistent. The activation energy of undiluted PP was in the range of 162–169 kJ mol−1 determined by the Ozawa method. The stabilized activation energy value for all blends studied above a 0.4 weight-loss fraction is discussed. 相似文献
Aromatic azides with hindered amine light stabilizer (HALS) residues or hydrophilic groups such as glucose, sucrose and dextrine residues were synthesized and used for surface modification of polyolefins. By UV‐irradiation nitrenes were formed, which are able to react with polyolefin surfaces. By photochemical immobilization of the carbohydrates hydrophilicity of PE and PP was strongly increased (surface tensions > 44mN/m). Light stability of PP surfaces modified with HALS azides was comparable with PP, stabilised with Tinuvin 770. Bulk modification of ethylene‐propylene and ethylene‐octene copolymers was achieved by grafting nitrenes formed by thermal decomposition of azido benzoic acid. In a circulating air oven up to 1.55 wt% amino benzoic acid residues could be bonded covalently to ethylene‐propylene‐copolymers, less than half of it to ethylene‐octene‐copolymers. Reactive extrusion resulted in grafting yields of more than 50% for both types of copolymers. 相似文献