嵌段共聚物相容剂对聚合物共混体系力学性能影响的连续介观模拟

结合介观动力学方法和三维弹簧格子模型,研究了嵌段共聚物相容剂对相容性较差的聚合物二元共混体系力学性能的影响.在适当范围内不断增加嵌段共聚物相容剂的用量,研究了相容剂含量对体系杨氏模数及拉伸强度的影响,同时也对不同体系材料的破碎位点进行了分析.结果表明,未加入相容剂的二元共混体系在拉伸模拟中表现出较低的拉伸强度,而适量添加相容剂可以显著提升材料的拉伸强度,随着相容剂含量的增加,共混体系的破碎位点会发生转移并最终改善材料的整体性能.而相容剂的加入对体系杨氏模数的影响较小.该连续模拟方法为关联聚合物复合体系的微观结构和宏观力学性能提供了一条高效的途径.     

嵌段共聚物相容剂对聚合物共混体系力学性能影响的连续介观模拟

结合介观动力学方法和三维弹簧格子模型, 研究了嵌段共聚物相容剂对相容性较差的聚合物二元共混体系力学性能的影响. 在适当范围内不断增加嵌段共聚物相容剂的用量, 研究了相容剂含量对体系杨氏模数及拉伸强度的影响, 同时也对不同体系材料的破碎位点进行了分析. 结果表明, 未加入相容剂的二元共混体系在拉伸模拟中表现出较低的拉伸强度, 而适量添加相容剂可以显著提升材料的拉伸强度, 随着相容剂含量的增加, 共混体系的破碎位点会发生转移并最终改善材料的整体性能. 而相容剂的加入对体系杨氏模数的影响较小. 该连续模拟方法为关联聚合物复合体系的微观结构和宏观力学性能提供了一条高效的途径.     

Effect of styrene-4-vinyl pyridine diblock copolymer on morphological,thermal, and mechanical properties of poly(2,6-dimethyl-1,4-phenylene ether)/polyethylene ionomer blends

The compatibilizing effects of a styrene-4-vinyl pyridine diblock copolymer on the properties of immiscible poly(2,6-dimethyl-1,4-phenylene ether) (PPE)/polyethylene ionomer (Surlyn) blends are investigated by examining the phase morphology and the thermal and mechanical properties. The block copolymer is synthesized by sequential anionic polymerization at ?78°C and melt-mixed with PPE and Surlyn at 290°C. When a small amount of block copolymer is present, the domain size of the dispersed phase becomes smaller. The tensile strength and elongation at break increase with addition of the block copolymer for PPE-rich matrix blends, whereas the tensile strength increases but the elongation at break decreases for Surlyn-rich matrix blends. These effects are interpreted in terms of the interfacial activity and the reinforcing effect of the block copolymer. From the experimental results, it is concluded that the block copolymer plays a role as an effective compatibilizer for PPE/Surlyn blends. © 1994 John Wiley & Sons, Inc.     

磨盘碾磨制备PA6/PP/SBS共混物的结构与性能

采用磨盘形力化学反应器,在室温下制备了PA6/PP超细混合粉体,与SBS共混制得PA6/PP/SBS共混物,测定了材料的力学性能并用TEM研究了材料在不同加工温度下相结构的变化.结果表明,通过固相力化学粉碎制备的PA6/PP混合微粉,改善了PA6与PP和SBS的相容性,促进了PA6及PP的分散和与SBS的相界面结合.在微粉填充量为4%～8%(质量分数)时,材料的拉伸强度大幅度提高,扯断伸长率保持不变.加工温度变化引起材料相结构的变化对材料性能产生显著影响.在PP熔融温度下加工,PP粒子产生粘连形成链状结构,可提高材料的力学性能.     

Ternary polymer blends: prediction of mechanical properties for various phase structures

A predictive scheme is proposed for the simultaneous calculation of the modulus and yield (or tensile) strength of ternary polymer systems. According to the continuity or discontinuity of constituting phases, the scheme combines in two steps the models for binary systems: (i) in the interval of phase duality (co‐continuity), a two‐parameter equivalent box model is used along with the data on the phase continuity rendered by modified equations of the percolation theory; and (ii) the effects of a dispersed phase on the mechanical properties of a continuous phase are treated by using the approach developed earlier for particulate systems. Simultaneously predicted values of the modulus and yield (or tensile) strength of ternary systems are interrelated because they are calculated by using an identical set of input parameters characterizing a specific phase structure. The predictive scheme will allow the experimentalists: (i) to anticipate selected mechanical properties of envisaged blends (for presumed phase structures); (ii) by comparing experimental and theoretical data, to assess to which percentage the potential of a material has been exploited; (iii) to analyze the phase structure of prepared ternary blends; and (iv) to evaluate interfacial adhesion or the extent of interfacial debonding. The versatility of the predictive scheme is demonstrated on three examples of various types of ternary systems. Copyright © 2000 John Wiley & Sons, Ltd.     

间规聚苯乙烯/等规聚丙烯/间规聚苯乙烯-b-聚(1-丁烯)共混体系相容性

间规聚苯乙烯(sPS)的改性主要是对其增韧改性,提高其力学性能.sPS的化学改性已有较多文献报道[1,2].     

Tough crystalline blends of polylactide with block copolymers of ethylene glycol and propylene glycol

The effect of crystallinity of polylactide (PLA) on the structure and properties of tough PLA blends with PEG-b-PPG-b-PEG block copolymers was studied. PLA was melt blended with a set of the copolymers with varying ratio of the hydrophilic (PEG) and hydrophobic (PPG) blocks. Although the blend phase structure depended on the copolymer molar mass and PEG content, as well as on the copolymer concentration in the blend, crystallinity also played an important role, increasing the copolymer content in the amorphous phase and enhancing phase separation. The influence of crystallinity on the thermal and mechanical properties of the blends depended on the copolymer used and its content. The blends, with PLA crystallinity of 25 ÷ 34 wt%, exhibited relatively high glass transition temperature ranging from 45 to 52 °C, and melting beginning above 120 °C. Although with a few exceptions crystallinity worsened the drawability and toughness, these properties were improved with respect to neat crystalline PLA in the case of partially miscible blends, in which fine liquid inclusions of the modifier were dispersed in PLA rich matrix. About 20-fold increase of the elongation at break and about 4-fold increase of the tensile impact strength were reached at a small content (10 wt%) of the modifier. Moreover, crystallinity decreased oxygen and water vapor transmission rates through neat PLA and the blend, and the barrier property for oxygen of the latter was better than that of neat polymer.     

Thermal and mechanical properties of UV irradiated collagen/chitosan thin films

The thermal and mechanical properties of collagen/chitosan blends before and after UV irradiation have been investigated using thermal analysis and mechanical (Instron) techniques. Comparisons were made with the thermal and mechanical properties of both collagen and chitosan films. Air-dried collagen, chitosan and collagen/chitosan films were exposed to UV irradiation (wavelength 254 nm) for different time intervals. Thermal properties of collagen/chitosan blends depend on the composition of the blend and are not significantly altered by UV irradiation.Mechanical properties such as ultimate tensile strength and ultimate percentage of elongation were much better for collagen films than for collagen/chitosan films. The results have shown that the mechanical properties of the blends were greatly affected by the duration of UV irradiation. Ultimate tensile strength and ultimate percentage elongation decreased after UV irradiation of the blend. Increasing UV irradiation leads to an increase in Young's modulus of the collagen/chitosan blend.     

Molecular design of multicomponent polymer systems. X. Emulsifying effect of poly(styrene-b-methyl methacrylate) in poly(vinylidene fluoride)/noryl blends

The emulsifying activity of block copolymers is investigated in blends of incompatible engineering polymers such as polyvinyldene fluoride (PVF₂) and Noryl (high impact polystyrene-poly-2,6-dimethyl-1,4-phenylene oxide mixture). When the blends are modified by a poly(styrene-b-methyl methacrylate) copolymer, (PS-PMMA) each block of which being selectively miscible with Noryl and PVF₂ respectively, Phase dispersion, interfacial adhesion and ultimate mechanical properties are significantly improved; major effect is observed upon addition of 12 percent copolymer, resulting in intermingled and firmly adherent phases and a rough additivity of both tensile strength and elongation at break. All these features clearly demonstrate the important emulsifying effect of PS-PMMA in these very attractive PVF₂/Noryl blends.     

Investigations of the influence on the phase morphology of PP-EPDM-blends on their mechanical properties

This work covers the dependence of the mechanical properties of polymer blends on their composition and their phase morphology. Blends of EPDM-elastomers and polypropylene were prepared covering the whole concentration range. The phase morphology was varied strongly by employing different mixing techniques and its morphology was characterized by means of electron microscopy and light microscopy, as well as by x-ray scattering and calorimetry.Mechanical properties such as the complex shear modulus, the tensile modulus as well as the stress strain behavior were investigated as a function of the composition of the blends and their phase morphology. The experimental finding is that the complex modulus, the tensile modulus, the yield stress, and the ultimate stress are rather insensitive with respect to the phase morphology and vary continuosly with the composition. The elongation at break, on the other hand, as well as the impact strength were found to depend on the phase morphology and to vary discontinously with the composition. One conclusion to be drawn is that one is not always forced to control the phase morphology tightly during processing in order to obtain materials with sufficiently good mechanical properties. Rather, simple theoretical approaches, neglecting details of the phase morphology are frequently able to satisfactorily predict mechanical properties of multiphase blends.     

Reactive compatibilization of nylon copolymer/EPDM blends: experimental aspects and their comparison with theory

In situ reactive compatibilization was first time applied to a low melting nylon (nylon 6 and 66 copolymer) and EPDM blend system. The effects of in situ compatibilization and concentration of compatibilizer on the morphology and mechanical properties of nylon/EPDM blends have been investigated. The influence of EPM‐g‐MA on the phase morphology was examined by the scanning electron microscopy (SEM) after preferential extraction of the minor phase. The SEM micrographs were quantitatively analyzed for domain size measurements. The compatibilizer concentrations used were 0, 1, 2.5, 5, and 10 wt%. The graft copolymer (nylon‐g‐EPM) formed at the interface showed relatively high emulsifying activity. A maximum phase size reduction was observed when 2.5 wt% of compatibilizer was added to the blend system. This was followed by a leveling‐off at higher loadings indicating interfacial saturation. The conformation of the compatibilizer at the interface was deduced based on the area occupied by the compatibilizer at the blend interface. The experimental compatibilization results were compared with theoretical predictions of Noolandi and Hong. It was concluded that the molecular state of compatibilizer at interface changes with concentration. The in situ compatibilized blends showed considerable improvement in mechanical properties. Measurement of tensile properties shows increased elongation as well as enhanced modulus and strength up on compatibilization. At higher concentrations of compatibilizer, a leveling‐off of the tensile properties was observed. A good correlation has been observed between the mechanical properties and morphological parameters. Copyright © 2007 John Wiley & Sons, Ltd.     

Mechanical and Morphological Properties of Bio-Phenolic/Epoxy Polymer Blends

Polymer blends is a well-established and suitable method to produced new polymeric materials as compared to synthesis of a new polymer. The combination of two different types of polymers will produce a new and unique material, which has the attribute of both polymers. The aim of this work is to analyze mechanical and morphological properties of bio-phenolic/epoxy polymer blends to find the best formulation for future study. Bio-phenolic/epoxy polymer blends were fabricated using the hand lay-up method at different loading of bio-phenolic (5 wt%, 10 wt%, 15 wt%, 20 wt%, and 25 wt%) in the epoxy matrix whereas neat bio-phenolic and epoxy samples were also fabricated for comparison. Results indicated that mechanical properties were improved for bio-phenolic/epoxy polymer blends compared to neat epoxy and phenolic. In addition, there is no sign of phase separation in polymer blends. The highest tensile, flexural, and impact strength was shown by P-20(biophenolic-20 wt% and Epoxy-80 wt%) whereas P-25 (biophenolic-25 wt% and Epoxy-75 wt%) has the highest tensile and flexural modulus. Based on the finding, it is concluded that P-20 shows better overall mechanical properties among the polymer blends. Based on this finding, the bio-phenolic/epoxy blend with 20 wt% will be used for further study on flax-reinforced bio-phenolic/epoxy polymer blends.     

Polymer blends—I. Mechanical and morphological behaviour of polyethylene/polyvinyl chloride blends

As part of a fundamental study of the behaviour of mixed plastics during reprocessing and in service, blends of low density polyethylene (LDPE) and polyvinyl chloride (PVC) have been investigated. It was found that Young's modulus increased steadily from pure LDPE to pure PVC whereas both tensile strength at break and elongation at break passed through a minimum at about 5% PVC. Optical and scanning electron microscope studies have related this mechanical behaviour to morphological changes in the two phase system under stress.     

聚甲醛和聚氨酯共混物的微观结构与力学性能

聚甲醛和聚氨酯共混物的微观结构与力学性能徐卫兵，朱士旺，蔡琼英（合肥工业大学化工学院合肥２３０００９）关键词聚甲醛，聚氨酯，共混物，微观结构，力学性能聚甲醛（ＰＯＭ）是６０年代发展起来的新型工程塑料，具有高密度、高结晶性，且坚硬、耐磨、自润滑、耐疲劳...     

Interpenetrating polymer networks of poly(carbonate-urethane) and polyvinyl pyridine

Simultaneous interpenetrating polymer networks (IPN's), pseudo IPN's, and liner blends of aliphatic poly(carbonate-urethane) (PCU) and polyvinyl pyridine (PVP) have been prepared and characterized by DSC, DMA, and TEM. The full IPN's of PCU and PVP had a single phase morphology only above 50 wt % PCU, as determined by both DSC and DMA and confirmed by transmission electron microscopy (TEM). However, in both pseudo IPN's of PCU and PVP and in their linear blends there exist multiple glass transitions and melting points seen by DSC and DMA indicating phase incompatibility. The full IPN's exhibited superior ultimate mechanical properties and solvent resistance as compared to the pseudo IPN's, liner blends, and the pure crosslinked PCU and PVP networks.     

SYNERGISTIC MODIFICATION OF EPDM AND CROSSLINKING AGENT IN IMMISCIBLE BLENDS OF POLYVINYL CHLORIDE WITH LOW DENSITY POLYETHYLENE

The synergism of ethylene-propylene-diene monomer copolymer （EPDM） and dicumyl peroxide （DCP, a crosslinking agent） in low density polyethylene （LDPE）/poly（vinyl chloride） （PVC） blends was investigated. When EDPM and DCP are added to the blends simultaneously, the tensile properties could be improved significantly, especially for the blends with LDPE matrix. For example, incorporation of 10/1 （mass ratio） EPDM/DCP improves the tensile strength of the LDPE/PVC （mass ratio 80/20） blend from 7.9 MPa to 8.5 MPa and the elongation at break from 25% to 503%. Results from selective extraction, phase-contrast microscopy and thermal analysis reveal that the improvement in the tensile properties of the blends with LDPE matrix is principally due to the formation of a fine crosslinking network of the LDPE and EPDM phase. The outstanding modification effect of EPDM is explained by its dual functions： molecular entanglement with LDPE and the enhanced efficiency of DCP in the blends.     

Effect of oil and cured agent content on the structure and properties of thermoplastic vulcanizates

The effect of oil and curing agent content on the mechanical behavior of thermoplastic vulcanizates, based on a polypropylene (PP) and ethylene‐propylene‐diene copolymer (EPDM), was investigated. Mechanical properties such as Young's modulus, stress at 100% elongation and ultimate stress were investigated as a function of blends' composition and phase morphology. Experimental studies show that the Young's modulus of the vulcanizates depends on both PP/EPDM ratio and oil content in the blends; both ultimate strength and stress at 100% elongation increase with curing agent content.     

Rheological,mechanical and morphological properties of thermoplastic vulcanizates based on NR‐g‐PMMA/PMMA blends

Graft copolymer of natural rubber and poly(methyl methacrylate) (NR‐g‐PMMA) was prepared using semi‐batch emulsion polymerization technique via bipolar redox initiation system. It was found that the grafted PMMA increased with the increase of methyl methacrylate (MMA) concentration used in the graft copolymerization. The NR‐g‐PMMA was later used to prepare thermoplastic vulcanizates (TPVs) by blending with PMMA through dynamic vulcanization technique. Conventional vulcanization (CV) and efficient sulphur vulcanization (EV) systems were studied. It was found that the CV system provided polymer melt with lower shear stress and viscosity at a given shear rate. This causes ease of processability of the TPVs via extrusion and injection molding processes. Furthermore, the TPVs with the CV system showed higher ultimate tensile strength and elongation. The results correspond to the morphological properties of the TPVs. That is, finer dispersion of the small vulcanized rubber particles were observed in the PMMA matrix. Various blend ratios of the NR‐g‐PMMA/PMMA blends using various types of NR‐g‐PMMA (i.e. prepared using various percentage molar ratios of NR and MMA) were later studied via dynamic vulcanization by a conventional sulphur vulcanization system. It was found that increasing the level of PMMA caused increasing trend of the tensile strength and hardness properties but decreasing level of elongation properties. Increasing level of the grafted PMMA in NR molecules showed the same trend of mechanical properties as in the case of increasing concentration of PMMA used as a blend component. From morphological studies, two phase morphologies were observed with a continuous PMMA phase and dispersed elastomeric phase. It was also found that more finely dispersed elastomeric phase was obtained with increasing the grafted PMMA in the NR molecules. Copyright © 2005 John Wiley & Sons, Ltd.     

COMPATIBILIZERS FOR LOW DENSITY POLYETHYLENE/POLYPROPYLENE BLENDS

The role of polyolefin elastomers as compatibilizers in Low Density Polyethylene/Polypropylene (LDPE/PP) blends, in the presence of di-cumyl peroxide (DCP) has been studied. Mixtures of 90/10 LDPE/PP ratio, were prepared in a Brabender plasticorder and tested for their mechanical properties and calorimetric response. Then the elastomers ethylene-propylene-diene copolymer (EPDM) and polybutadiene (BR) were added, alone or together with 0.2% DCP at concentrations up to 2%. The mixing torque and gel content of the above products were recorded as a function of the blend consistency. Also, the mechanical properties of specimens were measured as an additional evidence to explore the capabilities of these additives to promote compatibility of the blend components. It was found that EPDM and BR can be easily incorporated into polyolefin blends and appear suitable as potential compatibilizers for those materials, probably acting within the PP phase. Both elastomers result in an increase of strength and modulus, the BR having more enhanced effect. The latter gives low elongation, which allows its use in applications where high tensile properties are desired and flexural behavior is not critical.     

Dynamically Photocrosslinking of Polypropylene／EPDM Blends as a Thermoplastic Elastomer

The mechanical properties and the crystal morphological structures of the dynamically photocrosslinked polypropylene (PP)/ethylene-propylene-diene terpolymer (EPDM) blends have been studied by means of mechanical tests, wide-angle X-ray diffraction(WAXD), and differential scanning calorimetry(DSC). The dynamically photocrosslinking of the PP/EPDM blends can improve the mechanical properties considerably, especially the notched Izod impact strength at low temperatures. The data obtained from the mechanical tests show that the notched Izod impact strength of the dynamically photocrosslinked sample with 30% EPDM at -20℃ is about six times that of the uncrosslinked sample with the same EPDM component. The results from the gel content, the results of WAXD, and the DSC measurements reveal the enhanced mechanism of the impact strength for the dynamically photocrosslinked PP/EPDM blends as follows: (1) There exists the crosslinking of the EPDM phase in the photocrosslinked PP/EPDM blends ; (2) The β-type crystal structureof PP is formed and the content of α-type crystal decreases with increasing the EPDM component; (3) The graft copolymer of PP-g-EPDM is formed at the interface between the PP and EPDM components. All the above changes of the crystal morphological structures are favorable for increasing the compatibility and enhancing the toughness of the PP/EPDM blends at low temperatures.