Viscoelastic properties of ionic polymer composites reinforced by soy protein isolate

Both linear and nonlinear viscoelastic properties of ionic polymer composites reinforced by soy protein isolate (SPI) were studied. Viscoelastic properties were related to the aggregate structure of fillers. The aggregate structure of SPI is consisted of submicron size of globule protein particles that form an open aggregate structure. SPI and carbon black (CB) aggregates characterized by scanning electron microscope and particle size analyzer indicate that CB aggregates have a smaller primary particle and aggregate size than SPI aggregates, but the SPI composites have a slightly greater elastic modulus in the linear viscoelastic region than the CB composites. The composite containing 3–40 wt % of SPI has a transition in the shear elastic modulus between 6 and 8 vol % filler, indicating a percolation threshold. CB composites also showed a modulus transition at <6 vol %. The change of fractional free volume with filler concentration as estimated from WLF fit of frequency shift factor also supports the existence of a percolation threshold. Nonlinear viscoelastic properties of filler, matrix, and composites suggested that the filler‐immobilized rubber network generated a G′ maximum in the modulus‐strain curves and the SPI formed a stronger filler network than the CB in these composites. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3503–3518, 2005     

Determination of dynamic properties of flax fibres reinforced laminate using vibration measurements

Experimental and numerical methods to identify the linear viscoelastic properties of flax fibre reinforced polymer (FFRP) composite are presented in this study. The method relies on the evolution of storage modulus and loss factor as observed through the frequency response. Free-free symmetrically guided beams were excited in the dynamic range of 10 Hz to 4 kHz with a swept sine excitation focused around their first modes. A fractional derivative Zener model has been identified to predict the complex moduli. A modified ply constitutive law has been then implemented in a classical laminates theory calculation (CLT) routine. Overall, the Zener model fitted the experimental results well. The storage modulus was not frequency dependant, while the loss factor increased with frequency and reached a maximum value for a fibre orientation of 70°. The damping of FFRP was, respectively, 5 and 2 times higher than for equivalent carbon and glass fibres reinforced epoxy composites.     

Rheological properties of road bitumens modified with polymer and solid nanosized additives

The study of the viscoelastic properties of composites based on road bitumens have shown that the addition of polymeric modifiers (poly(bytadiene-block-styrene) or devulcanized rubber particles) substantially increases the storage and loss moduli and decreases the intensity of reduction in the storage modulus with temperature by several orders of magnitude. However, at high polymer content, growth inadmissible from the point of view of acceptable technological parameters is observed in the apparent viscosity. The introduction of carbon nanotubes into bitumen does not substantially affect its viscoelastic properties. Filling with meta-kaolin promotes an increase in the storage modulus at elevated temperatures. It has been shown that a direct correlation may be established between the objective characteristics of bitumen-based composites and standard specification parameters, such as penetration depth and heat resistance.     

Rheological Behavior of the Melts for Polyethylene-based Montmorillonite Nanocomposites

IntroductionOwing to their special structures or morphologies,polymer-based montmorillonite nanocomposites exhibitsome particular characteristics,such as,physical,thermal,and mechanical properties,induced by theaddition of very small amounts of inorganic …     

Thermogravimetric and dynamic mechanical thermal analysis of pineapple fibre reinforced polyethylene composites

The thermal behaviour of pineapple leaf fibre (PALF) reinforced polyethylene composites was studied by thermogravimetric and dynamic mechanical thermal analysis. Fibre treatment was carried out using isocyanate, silane and peroxide to improve the interfacial adhesion between fibre and matrix. The effects of fibre loading and surface modification on the thermal properties were evaluated. It was found that at high temperature PALF degrades before the polyethylene matrix. The storage modulus increased with increase of fibre loading and decreased with increase of temperature. The treated fibre composites impart better properties compared to untreated system. Tan δ showed a distinct peak at low temperature ascribed to the glass transition temperature of polyethylene but no peak was observed for PALF fibre. The relative damping increased with fibre loading. Cole-Cole analysis was made to understand the phase behaviour of the composite samples.     

Dynamic-mechanical properties as a function of luffa fibre content and adhesion in a polyester composite

In this work, the characteristics of a vegetable fibre (luffa cylindrica) polyester composite are studied as a function of fibre surface treatment (with NaOH, Ca(OH)₂ and silane) and fibre content (30%, 40% and 50%). Composites were prepared through compression moulding and characterized with thermogravimetric and dynamic-mechanical analyses. Higher storage modulus was obtained with Ca(OH)₂ treated composites, reaching nearly 70% increase. Higher loss modulus (E”) was noted in for silane treated fibre (at 50%) and a high peak in damping factor was noted for Ca(OH)₂ treated fibre (at 50%). Cole-cole plot showed highest homogeneity for the Ca(OH)₂ treated composites. Electron microscopy revealed the fracture modes in static tested composites. The general properties obtained indicate that the composites can only be used for low loading applications.     

Mechanical and dynamic viscoelastic properties of hydroxyapatite reinforced poly(ε-caprolactone)

Poly(ε-caprolactone)/hydroxyapatite (PCL/HA) composites as potential bone substitutes were prepared by melt-blending. The melting, crystallization and glass transition temperatures deduced from differential scanning calorimetery and dynamic mechanical thermal analysis (DMTA) were all changed by the addition of HA, suggesting an interaction at the interface of these two phases. Quasi-static mechanical testing shows that the yield strength and Young's modulus of PCL were increased by the addition of the reinforcement filler, HA. Dynamic viscoelastic properties were investigated using DMTA and an advanced rheometric expansion system. The results show that both the storage modulus and viscous modulus are enhanced by HA, and the PCL composite melts still behave like pseudo-plastic liquid.     

冷冻/解冻制备的聚乙烯醇水凝胶的结构和流变性研究

研究了冷冻/解冻法制备的不同浓度(5wt%～25wt%)聚乙烯醇(PVA)水凝胶的结构和流变行为之间的关系.由XRD确定了凝胶中PVA的结晶度和晶粒尺寸.用应力流变仪研究了凝胶的流变行为,包括动态模量和蠕变等.在频率为1Hz和低应力的条件下,测量了凝胶的储能模量和损耗模量.在该试验条件下,PVA水凝胶的形变是完全可以回复的.低频率区和低应变区的储能模量随浓度增加而变大,但当浓度超过20wt%时,储能模量增加速率明显降低.由PVA水凝胶在1Hz时的储能模量和结晶度的数据,理论分析得到了形成PVA水凝胶的最低PVA浓度和最小结晶度.当PVA浓度低于15wt%时,储能模量主要由PVA的微晶控制,分子链间的氢键影响很小.通过低应变区储能模量的数值计算出了凝胶网孔尺寸的结构参数.同时对不同温度下PVA水凝胶的储能模量数据进行了标度分析.PVA水凝胶的蠕变行为显示,随浓度提高,凝胶的蠕变黏弹性由线性向非线性转变.     

Dynamic mechanical properties of aluminum nitride/cyanate ester composites for high performance electronic packaging

Viscoelastic ature is one of the key features of polymeric composites. A series of cyanate ester (CE)‐based composites with different aluminum nitride (AlN) contents for high performance electronic packaging, coded as AlN/CE, were developed; the viscoelastic nature of AlN/CE composites was intensively investigated by employing dynamic mechanical analysis (DMA). Results show that the AlN content has a great effect on dynamic mechanical properties of AlN/CE composites. The storage modulus in the glassy region increases linearly with the addition of AlN as well as the increase of AlN content. Meanwhile, all composites also exhibit notably higher loss modulus than cured CE resin due to the appearance of new energy dissipation forms. In addition, the incorporation of AlN has a significant effect on damping factor peak. All reasons leading to these phenomena are analyzed from the view of structure–property relationship. Copyright © 2009 John Wiley & Sons, Ltd.     

Mechanical properties of hybrid glass/sugar palm fibre reinforced unsaturated polyester composites

A research has been carried out to investigate the mechanical properties of composites made by hybridizing sugar palm fibre (Arenga pinnata) with glass fibre into an unsaturated polyester matrix. Hybrid composites of glass/sugar palm fibre were fabricated in different weight ratios of strand mat glass fibres: sugar palm fibres 4:0, 4:1, 4:2, 4:3, 4:4, and 0:4. The hybrid effects of glass and sugar palm fibre on tensile, flexural and impact properties of the composites were evaluated according to ASTM D5083, ASTM D790 and ASTM D256 respectively. Results have been established that properties of hybrid glass/sugar palm composites such as tensile strength, tensile modulus, elongation at break, toughness, flexural strength, flexural modulus and impact strength are a function of fibre content. The failure mechanism and the adhesion between fibres/matrix were studied by observing the scanning electron micrographs of impact fracture samples. In general, the incorporation of both fibres into unsaturated polyester matrix shows a regular trend of increase in the mechanical properties.     

Kapok/cotton fabric–polypropylene composites

Kapok/cotton fabric has been used as reinforcement for conventional polypropylene and maleic anhydride grafted polypropylene resins. Treating the reinforcement with acetic anhydride and sodium hydroxide has modified the fabric (fibres). Thermal and mechanical properties of the composites were investigated. Results show that fibre modification gives a significant improvement to the thermal properties of the plant fibres, whereas tests on the mechanical properties of the composites showed poor tensile strength. Mercerisation and weathering were found to impart toughness to the materials, with acetylation showing slightly less rigidity compared to other treatments on either the fibre or composites. The modified polypropylene improved the tensile modulus and had the least toughness of the kapok/cotton reinforced composites. MAiPP reinforced with the plant fibres gave better flexural strength and the same flexural modulus at lower fibre content compared with glass fibre reinforced MAiPP.     

Viscoelastic properties of sterically stabilized nonaqueous dispersions

The viscoelastic properties of a dispersion of poly(vinyl acetate) particles sterically stabilized by poly(2-ethyl hexyl methacrylate) and dispersed in Isopar G have been measured as a function of particle concentration and frequency at ambient temperature.At low particle concentrations, it was found that the loss modulus was larger than the storage modulus, while at high particle concentrations, i.e.,w>0.40, the storage modulus was found to be larger than the loss modulus. This inversion from a viscous to an elastic response as a function of particle concentration is attributable to the change in the configurational entropy of the steric barrier as a result of increasing the concentration of particles in the dispersion.     

Glutaraldehyde treatment of bacterial cellulose/fibrin composites: impact on morphology, tensile and viscoelastic properties

Bacterial cellulose/fibrin composites were treated with glutaraldehyde in order to crosslink the polymers and allow better match of the mechanical properties with those of native small-diameter blood vessels. Tensile and viscoelastic properties of the glutaraldehyde treated composites were determined from tensile static tests and cyclic creep tests, respectively. Glutaraldehyde-treated (bacterial cellulose) BC/fibrin composites exhibited tensile strength and modulus comparable to a reference small-diameter blood vessel; namely a bovine coronary artery. However, the breaking strain of the glutaraldehyde-treated composites was still well below that of the native blood vessel. Yet a long strain hardening plateau was induced by glutaraldehyde treatment which resembled the stress–strain response of the native blood vessel. Tensile cyclic creep test indicated that the time-dependent viscoelastic behavior of glutaraldehyde-treated BC/fibrin composites was comparable to that of the native blood vessel. Covalent bonding between BC and fibrin occurred via glutaraldehyde, affording mechanical properties comparable to that of the native small blood vessel.     

Comparison between 3-point bending and torsion methods for determining the viscoelastic properties of fiber-reinforced epoxy

Dynamic mechanical analysis is a technique used to determine the viscoelastic properties of polymers and their composites. The storage modulus, loss modulus and loss factor in correlation with the glass transition temperature can be detected by several means. In this study, these properties are determined using a dynamic mechanical analyzer in 3-point bending mode, as well as a rheometer in torsion mode. The materials under consideration are a unidirectional glass fiber-reinforced epoxy, a quasi-isotropic carbon fiber-reinforced epoxy and a quasi-isotropic glass fiber-reinforced epoxy. The results of each method and material are presented and the advantages and limitations of each method are discussed. 3-point bending proved to be more suitable to detect the effect of fiber orientation for unidirectional fiber-reinforced epoxy but requires careful control of sample dimensions for accuracy. Torsion, on the other hand, gave consistent measurements for samples of varying lengths, proving to be a suitable method if materials are scarce and limited.     

Linear Viscoelastic Behavior of Multiphase Dispersions

The linear viscoelastic behavior of polymer-thickened oil-in-water emulsions, polymer-thickened solids-in-liquid suspensions, and their blends is investigated using a controlled-stress rheometer. The emulsions exhibit a predominantly viscous behaviour at low values of oil concentration in that the loss modulus (G") exceeds the storage modulus (G') over most of the frequency range. At high values of oil concentration, the emulsions exhibit a predominantly elastic behavior. The ratio of storage modulus to loss modulus (G'/G") increases with the increase in oil concentration. Emulsions follow the theoretical model of J. F. Palierne (1990, Rheol. Acta 29, 204) only at low values of oil volume fraction (/=G' over most of the frequency range. The ratio G'/G" varies only slightly with the increase in solids volume fraction. The Palierne model describes the linear viscoelastic properties of suspensions accurately only at low values of solids volume fraction. At high values of solids concentration, the Parlierne model underpredicts the linear viscoelastic properties of suspensions and the deviation increases with the increase in solids concentration. The blends of emulsions and suspensions exhibit strong synergistic effects at low to moderate values of frequencies; the plots of blend modulus versus emulsion content exhibit a minimum. However, at high values of frequency, the blend modulus generally falls between the moduli of pure suspension and pure emulsion. The high-frequency modulus data of blends of emulsions and suspensions are successfully correlated in terms of the modulus ratio versus volume fraction of solids, where modulus ratio is defined as the ratio of blend modulus to pure emulsion modulus at the same frequency. Copyright 2000 Academic Press.     

国内外PVB材性研究

主要介绍了国内外研究PVB(聚乙烯醇缩丁醛)材性的现状。国内外研究表明,PVB是应变率及温度敏感材料。应变率增加,弹性模量变大;温度升高,弹性模量和剪切模量均下降。同时,国内外进行了少量的实验,研究PVB的本构模型。总结发现,PVB的本构模型可描述为线弹性、弹塑性、线性粘弹性和非线性粘弹性四种,但本质上PVB是非线性粘弹性材料,不同的环境条件与计算要求可选择不同的本构模型。目前,国内外学者比较认可的是用超弹性考虑其非线性,用Maxwell模型考虑其粘弹性。     

Mechanical, thermal, and moisture absorption properties of nano-clay reinforced nano-cellulose biocomposites

In this research, fully environment-friendly, sustainable and biodegradable ‘green’ composites were fabricated. A novel material comprised of microfibrillated cellulose and laponite clay with different inorganic/organic ratios (m/m) was prepared. The composites were characterized by tensile, bending and water absorption tests as well as dynamic mechanical analysis. The morphologies of these nanocomposites were evaluated through scanning electron microscopy. Results showed considerable improvement of mechanical properties; specifically in elastic modulus, tensile strength and flexural modulus with the addition of nanoclay up to 7.5 wt% nano-clay. The modulus of elasticity increased significantly by about 26 % at 5 wt% nanocaly. The flexural modulus increased by about 90 % at 7.5 wt% nanoclay. However, with an increased load of clay in the nanocomposite, the mechanical properties decreased due to the agglomeration of excessive nanoclay. The storage modulus was significantly increased at high temperature with increasing the load of nanoclay.     

聚乙烯/氧化铝复合材料形态、流变和力学性能

将聚乙烯（PE）和氧化铝（AO）熔融共混制得综合性能更好的PE/AO复合材料。通过对其进行流变分析、热力学性能分析、力学性能分析、导热性能分析和断面微观结构分析,探究AO质量分数对复合材料结构及性能的影响。结果表明,随着AO质量分数的增加,复合材料逐步转为脆性材料,其弹性模量、屈服强度、导热系数、储能模量同步增加;当AO质量分数为10%时,复合材料的断裂强度为18.2 MPa,综合性能最好。     

Gel kinetic characteristics and creep behavior of polymer microspheres based on bulk gel

Abstract

Deep profile control technology of polymer microspheres has become a widely used new method in improving oil recovery in heterogeneous reservoirs. The viscoelastic property of polymer microspheres plays an important role in the deformable migration behavior. In this study, a new method of measuring the viscoelastic properties of polymer microspheres based on bulk gel was proposed. Using mechanical rheometer and microrheometer, the effects on the storage modulus and gel performance were systematically researched. The creep-recovery test was applied to characterize the creep behavior of different polymer microsphere bulk gel. The results show that the storage modulus of polymer microspheres could be controlled by adjusting the agent concentration in the synthetic reaction. Moreover, the kinetic equation of gel time of polymer microspheres bulk gel and reaction temperature was established: ln(GT)?=?3289.18(1/T)-9.33. Elastic strain index was put forward as a new parameter to characterize the viscoelasticity of polymer microsphere in creep-recovery test. Finally, relationship between elastic strain index and storage modulus was constructed and a classification criterion of polymer microspheres with different viscoelasticity was proposed based on a large number of creep-recovery results. The research could provide a good theoretical guidance and technical support for the understanding of viscoelasticity of polymer microspheres.     

Study on the viscoelastic properties of the epoxy surface by means of nanodynamic mechanical analysis

The viscoelastic properties of the epoxy surface have been investigated by nanodynamic mechanical analysis (nano‐DMA). Both a Berkovich tip and a conospherical tip were used under the condition of different forces (i.e., different penetration depths) in the frequency range of 10–200 Hz. Loss tangent and storage modulus are characteristics that describe the viscoelastic properties. The effect of force frequency, penetration depth, and tip shape on the viscoelastic properties is studied and discussed according to the features of microstructures and mobility of molecular chains. The experimental results show important variations when the penetration depth is shallow (<30 nm). As the depth becomes deeper, the results tend to be stable and become almost constant over 120 nm. The two kinds of indenter tip can cause a slight difference of the storage modulus. A “master curve” of the storage modulus as a function of force frequency is established. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 281–288, 2008