Frequency and temperature dependence of molecular and micromechanical transitions in PPO/PMMA/P(S-g-EO) blends

The frequency and temperature dependence of molecular and micromechanical transitions were studied in polymer blends with an interphase. The viscoelastic properties of poly(2,6-dimethyl-p-phenylene oxide) (PPO) and poly(methyl methacrylate) (PMMA) blends that were compatibilized by a poly(styrene-graft-ethylene oxide) (P(S-g-EO)) copolymer were studied by dynamic mechanical spectroscopy (DMS) and the experimental data were compared with an interlayer model. The addition of the copolymer resulted in a micromechanical transition, and the relation between the volume fraction of interphase, the activation energy of the micromechanical transition, and the micromechanical transition temperature was studied. A qualitative agreement between experiments and theory was achieved. The quantitative difference was explained by partial mixing of PPO and/or PMMA with the copolymer in the interphase. © 1996 John Wiley & Sons, Inc.     

Sizing effects on main relaxation process of cyanate ester glass fiber composites using dynamic mechanical and microthermal analyses

The influence of sizing/polymer interaction or interphase on dynamic mechanical relaxation properties of cyanate ester composites was investigated by means of dynamic mechanical analysis. The dynamic mechanical behavior of different samples (three types of composites with different sizing and neat resin) was analyzed by using two phenomenological models (TFV and WLF). Related coefficients such as C₁, C₂, and T_∞ (Vogel temperature) were evaluated. Results have shown that these parameters were strongly dependent on sizing state, therefore, on interphase. In addition, the frequency dependence of the molecular relaxation process was well described by the Cole‐Cole plot. These results were confirmed by the sizing extract/resin blend study. Microthermal analysis has shown that partial miscibility existed between resin and sizing extract. Local thermal analyses were carried out by positioning the probe over selected regions: bulk resin and sizing/resin blend. A decrease in resin glass‐transition temperature was observed in the sizing resin blend. The different results have shown that a local plasticization of resin by sizing occurred with crosslink density modification. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 205–214, 2006     

Adhesion through molecular entanglements in polymer interfaces

This paper examines the role of polymer interdiffusion or interpenetration along and across a boundary of two compatible but dissimilar polymers in controlling interfacial adhesion in the interface region (interphase). The effect of interphase adhesion on the mechanical properties as well as the deformation and fracture behavior of sandwich laminates of poly(methylmethacrylate) (PMMA) and poly(vinylidene) fluoride (PVF₂) have been studied. The interphase has been characterized using microscopy (optical, transmission, and scanning electron), dynamic mechanical spectroscopy, and x-ray microanalysis. Conditions of multiple crazing/fracture in the brittle phase (PMMA) and shear yielding in the ductile phase (PVF₂) are discussed. Scanning electron micrographs confirm these deformation modes in PMMA-PVF₂ sandwich composite laminates.     

Micromechanical characterization of the interphase layer in semi‐crystalline polyethylene

The interphase layer in semi‐crystalline polyethylene is the least known constituent, compared to the amorphous and crystalline phases, in terms of mechanical properties. In this study, the Monte Carlo molecular simulation results for the interlamellar domain (i.e. amorphous+ interphases), reported in (Macromolecules 2006, 39, 439–447) are employed. The amorphous elastic properties are adopted from the literature and then two distinct micromechanical homogenization approaches are utilized to dissociate the interphase stiffness from that of the interlamellar region. The results of the two micromechanical approaches match perfectly. Interestingly, the dissociated interphase stiffness lacks the common feature of positive definiteness, which is attributed to its nature as a transitional domain between two coexisting phases. The sensitivity analyses reveal that this property is insensitive to the non‐orthotropic components of the interlamellar stiffness and the uncertainties existing in the interlamellar and amorphous stiffnesses. Finally, using the dissociated interphase stiffness, its effective Young's modulus is calculated, which compares well with the effective interlamellar Young's modulus for highly crystalline polyethylene, reported in an experimental study. This satisfactory agreement along with the identical results produced by the two micromechanical approaches confirms the validity of the new information about the interphase elastic properties in addition to making the proposed dissociation methodology quite reliable when applied to similar problems. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 1228–1243     

辐射增强PP／BR共混体系的力学性能

研究了在多官能团单体－三烯丙基异氰酸酯存在下，共混体系聚丙烯／１．４－聚丁二烯橡胶的辐射效应，用ＤＳＣ，动态粘弹谱对其进行表征。结果显示，三烯丙基异氰酸酯主要分布于聚丙烯／１．４－聚丁二烯橡胶共混物的界面自高能射线作用下，被引发参与界面反应，从而改善了共混体系的相容性，增强也界面粘接，提高了共混物的力学性能。     

Stiffness variation in the interphase of amine‐cured epoxy adjacent to copper microstructures

In an effort to expand the understanding of the mechanical properties of the polymeric interphase on a metal surface, a composite consisting of epoxy and copper was prepared and analyzed. Scanning force microscopy‐based force modulation microscopy (SFM‐FMM) was employed along with dynamic mechanical analysis (DMA) and energy dispersive X‐ray analysis (EDX). Diglycidyl ether of bisphenol A (DGEBA)‐based epoxy resins were applied with amine curing agents. The samples were made taking advantage of electron beam lithography (EBL) in order to produce sharp edges of copper structures and a flat surface suitable for the SFM‐FMM analysis, which was able to depict the stiffness within the interphase. It is considered significant information because the mechanical characteristic within the narrow interphase was revealed. Comparing with DMA and EDX, the stiffness information of SFM‐FMM demonstrated a matching correlation and agreement in terms of preferential adsorption of the curing agent in the vicinity of the interface. The stiffness profiles of the two epoxy systems turned out to be different, and it shows the material dependence of the interphase characteristics. Copyright © 2007 John Wiley & Sons, Ltd.     

Dynamic mechanical spectrometry for the study of multiphase polymer materials

The dynamic mechanical behaviour of multiphase polymer materials depends on two factors: (i) properties of each phase and (ii) geometric arrangement of these phases (so-called morphology). Analysis of experimental results has been performed in order to separate these two factors; it leads to informations about morphology, presence of interphase between main phases, chemical composition of different domains and possible changes in physical properties of one phase, induced by its neighbours. The interest in such an analysis based on mechanical spectrometry appears important because of difficulties in direct investigations (low contrast in Electron Microscopy, poor information provided by X-ray measurements on amorphous polymers … )     

Ethylene/silane copolymers prepared with a metallocene catalyst as polymeric additives in polyethylene/aluminum trihydroxide composites

Metallocene catalyst based polyethylene‐co‐7‐octenyldimethyl phenyl silane (PE/Si? Ph ) and its post‐treated functional forms PE/Si? X ( X = Cl , F , OCH₃ , OCH₂CH₃ ) were used as additives in PE/ATH composites. The impact strength of the composites was significantly increased after a small addition (0.5–3.0 wt %) of the functionalized form of the copolymer (PE/Si? X ). The thermal study of the composites gave us more information about the additive's behavior at the filler/matrix interphase and correlation to the mechanical properties was found. According to this thermal data, the original untreated form of PE/Si? Ph also seemed to interact weakly with the ATH‐filler particles, which was seen in an altered interphase at the filler/matrix boundary layer. The interaction was not strong enough to improve the impact strength of composites but an increase was observed in some other mechanical properties (tensile stress, yield strain). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5597–5608, 2005     

Effect of ionizing radiation on the dynamic mechanical properties of an epoxy and a graphite fiber/epoxy composite

TGDDM/DDS epoxy and T300/NARMCO 5208 composite specimens were exposed to 0.5 MeV electrons to dose levels up to 10,000 Mrad, and the effects of radiation on the mechanical properties were characterized using dynamic mechanical analysis (DMA). In nominally cured specimens there remain unreacted epoxide groups because the epoxy system vitrifies during the cure, preventing additional reaction. DMA shows that ionizing radiation continues the reactions of epoxide groups. Also, the ultimate glass transition is shown to decrease monotonically with radiation dose. The room temperature elastic modulus of the epoxy increases slightly with radiation, but at temperatures exceeding 100°C there is a slight decrease with radiation. There is a dynamic loss phenomena associated with the composites, not seen in the epoxy, that is thought to be due to the interphase region between the fiber and the matrix.     

Influence of extender oil composition on flowing property,thermal stability,and morphology of styrene‐b‐ethylene‐co‐butylene‐b‐styrene copolymer/polypropylene/oil blends

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 C_N 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 C_N content, the electron density difference between soft and hard phases reduced to the minimum, same as T_gPS, 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.     

多相聚合物体系相界面研究进展

综述了多相聚合物体系相界面的形成、界面层状态的表征、界面层性质及其对体系性能的影响。重点论述了不同类型增容剂对界面行为的影响，其中对嵌段型增容剂的分子量、浓度等因素对界面行为的影响建立了定量关系；而对接枝型和无规增容剂对界面行为的影响研究较少，有待发展。指出了在界面张力、界面层厚度与多相聚合物体系性能，尤其是力学性能之间建立量化关系是高分子物理领域一个可以期待的发展方向。     

Transitions and mechanical properties in polyoxymethylene/phenoxy blends

Blends of polyoxymethylene (POM) and phenoxy were obtained by melt-blending to determine their phase behavior and to determine, among others, their dynamic and static mechanical properties. The dynamic mechanical spectrum of POM showed an unusually wide peak below the melting temperature that was attributed to amorphous POM close to, and hindered by, the predominant crystalline phase. The T_g of phenoxy was constant with composition, as was probably that of POM, proving their complete immiscibility. The overall mechanical properties of the blends, however, were those of a compatible blend. The synergism in ductility observed in POM-poor blends was partially attributed to their lesser crystalline character. © 1996 John Wiley & Sons, Inc.     

The effect of fiber orientation and stacking sequence on carbon/E-glass/epoxy intraply hybrid composites under dynamic loading conditions

This study investigated the dynamic mechanical properties of hybrid intraply carbon/E-glass epoxy composites with different orientations and stacking sequences under different loading conditions with increasing temperature. A neat epoxy and five various hybrid composites such as Carbon (0°)/E-glass (90°), Carbon (45°)/E-glass (135°), Carbon (90°)/E-glass (0°), Carbon/E-glass (alternating layer), and Carbon/E-glass (alternating layer 45°) were manufactured. Three-point bending test and dynamic mechanical test were conducted to understand the flexural modulus and viscoelastic behavior (storage modulus, loss modulus, and loss tangent) of the composites. Dynamic mechanical test was performed with the dual cantilever method, at four different frequencies (1, 5, 10, and 20 Hz) and temperatures ranging from 30 to 150°C. The experimental results of storage modulus, loss modulus, and loss tangents were compared with the theoretical findings of neat epoxy and various hybrid composites. The glass transition temperature (T_g) increased with the increase in frequency. A linear fit of the natural log of frequency to the inverse of absolute temperature was plotted in the activation energy estimation. The interphase damping (tanδ_i) between plies and the strength indicator (S_i) of the hybrid composites were estimated. It was observed that the neat epoxy had more insufficient storage and loss modulus and a high loss tangent at all the frequencies whereas hybrid composites had high storage and loss modulus and a low loss tangent for all the frequencies. Compared with other hybrid composites, Carbon (90°)/E-glass (0°) had higher strength and activation energy. The result of reinforcement of hybrid fiber in neat epoxy significantly increases the material's strength and stability at higher temperatures whereas decreasing free molecular movement.     

Functionalized SWNT/polymer nanocomposites for dramatic property improvement

In this paper, we present results for polymer nanocomposites of poly‐ (methyl methacrylate) (PMMA) and amide‐functionalized SWNTs. The results demonstrate that even at very low loadings, 1 wt % (0.5 vol %), the mechanical and electrical properties are significantly improved. The improvement over PMMA properties exceeds the theoretical bounds for composites with the same volume fraction loading of randomly oriented, straight, individually dispersed nanotubes. The modeling and experimental results thus suggest that the nanotube bundles are well dispersed in the polymer matrix, that the functionalization significantly improves interaction with polymer, and that the interphase formed has improved mechanical properties over that of the matrix material. Loss modulus results indicate a significant difference between functionalized and nonfunctionalized tubes in the composite. Functionalized tubes result in a composite in which relaxation mechanisms are shifted by 30 °C from that of the matrix material, indicating extensive interphase regions and absence of PMMA with bulk properties. Unfunctionalized composites demonstrate a broadening of relaxation modes, but still retain the signature of bulk PMMA properties. These data suggest a morphological difference with a discrete interphase layer in unfunctionalized composites and a fully transformed matrix in the case of functionalization. This difference is consistent with electrical and mechanical property data. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2269–2279, 2005     

Effect of diblock copolymers on dynamic mechanical properties of polyethylene/polystyrene blends

A systematic investigation of the dynamic mechanical properties of high-density polyethylene (HDPE)/high-impact polystyrene (HIPS)/copolymer blends was carried out. Blends of 80/20 weight percent of HDPE/HIPS were prepared in the melt state at 180°C in a batch mixer. Synthesized pure diblock (H77) and tapered diblock (H35) copolymers of hydrogenated polybutadiene (HPB) and polystyrene (PS) were added at different concentrations (1, 3, and 5 wt %), and the dynamic mechanical properties were investigated. The results show that: (1) both the tapered and the pure diblock copolymers enhance the phase dispersion and the interphase interactions; (2) structure and molecular weight are both important parameters in the molecular design of copolymers; (3) important effects occur when only small amounts of copolymer are added (up to the interface saturation concentration SC); (4) a micellar structure formation is possible when the copolymer is in excess in the blend; (5) the effect of the copolymer structure on the SC and the critical micellar concentration (CMC) is more pronounced than the effect of molecular weight. These concentrations are found to be lower for the tapered diblock copolymer. The analysis of the dynamic mechanical thermal analysis (DMTA) results obtained for the 20/80 HDPE/HIPS blend leads to the conclusion that the copolymers also enhance the interactions between heterogeneous phases. Similar conclusions based on electron microscopy were reported in the literature. DMTA shows great potential to relate macroscopic observations to the state of a copolymer in an immiscible blend.     

Surface tension and mechanical properties in polyolefin composites

Polyolefin composites were prepared with CaCO₃ fillers of different specific surface area. The fillers were surface treated with stearic acid between 0 and 100% surface coverage. As an effect of the treatment, surface tension of the fillers and also polymer/filler interaction decreased. The relation between interfacial interaction and mechanical properties of the composites was analysed by the equation developed earlier to describe the composition dependence of the tensile yield stress. The characteristics of the interphase were calculated, its yield stress decreases and thickness increases with increasing surface coverage. Reversible work of adhesion can be successfully related to the tensile yield stress, but a more complicated correlation exists between the thickness of the interphase and the strength of the interaction than assumed earlier. Other mechanical properties also change with the surface treatment; modulus and strength decrease and extensibility increases with decreasing polymer/filler interaction.     

共聚聚醚酯酰胺的多重转变及其相态结构

Segmented polyesteramides have been synthesized from N,N'-bis（p-carbomethoxybenzoy）butanediamine（T4T）as crystalline segments and mixture of poly（tetramethylene oxide）with the average molecular weight 1000（PTMO1000）and 1,5-pentanediol（PDO）as soft segments. The polymerization was carried out in the melt at 250℃ for 1-2 h while vacuum was applied. The chemical composition of the copolymer was measured by H1-NMR. The melting behavior of the copolymers was studied by the differential scanning calorimeter. The dynamic mechanical properties were investigated on injection moulded bars by means of dynamic mechanical analysis. It was found that the copolymers with more than 40% molar ratio PDO showed two glass transition temperatures and two melting temperatures. The glass transition temperatures are independent of composition,and thus two fully phaseseparated amorphous phases are present. The melting temperatures change with PDO content. The amount of PDO has an effect on both TmA and TmB . TmA is attributed to the lamella consisting of extended T4T segments,while TmB results from the much thicker lamella consisting of both extended T4T and PDO segments. It is also possible that some PDO is present in the interphase as adjacent re-entry groups. So the resultant copolymer shows that a complex system,two crystalline phases,two amorphous phases and an interphase are involved in the copolymer. The undercooling for these copolymers is small,which means that these segmented copolymers crystallize fast.     

Time-scale through-thickness interphase in polymer matrix composites including hygrothermal treatment

For the first time, the physical effects of long-term environmental conditions on through-thickness interphase in polymer matrix composites (PMCs) were studied. Atomic force microscopy (AFM) -based Peak Force Quantitative Nanomechanical Mapping (PF QNM) technique was utilized to study the effects of heat and humidity on the mechanical properties of interphase at nanometer resolution. Samples were aged with a heat of 60 °C and relative humidity of 90% for up to 2 years. The width of the interphase is uneven and ‘river-like’ through the thickness in unaged and aged composites. The width of interphase depends on its location and the degree of moisture saturation. The difference in thickness of the interphase, through the thickness, reduces with exposure time. While the mechanism of expansion and shrinkage of interphase is different through-thickness, the range of material modulus is almost the same through-thickness in unaged and aged conditions. Rate of debonding increases from unaged to one-year aged and reduces in the second year of exposure.     

Spatiotemporal Changes of the Solid Electrolyte Interphase in Lithium‐Ion Batteries Detected by Scanning Electrochemical Microscopy

The solid electrolyte interphase (SEI) in lithium‐ion batteries separates the highly reductive lithiated graphite from reducible electrolyte components. It is critical for the performance, durability, and safe operation of batteries. In situ imaging of the SEI is demonstrated using the feedback mode of scanning electrochemical microscopy (SECM) with 2,5‐di‐tert‐butyl‐1,4‐dimethoxy benzene as mediator. The formation of the SEI is indicated by a decrease of the mediator regeneration rate. Prolonged imaging of the same region revealed fluctuation of the passivating properties on time scales between 2 min and 20 h with an inhomogeneous distribution over the sample. The implications of the approach for in situ assessment of local SEI properties on graphite electrodes are discussed with respect to studying the influence of mechanical stress on SEI reliability and the mode of action of electrolyte additives aiming at improving SEI properties.