Relaxation and viscoelastic properties of heterogeneous polymeric compositions

Lipatov, Yu.S.

doi:10.1007/3-540-07942-4_4

Cited by 70 publications

(25 citation statements)

References 62 publications

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“…One special advantage is that only a small amount of nanoparticles, typically 1-3 wt%, is required in order to achieve this enhancement. The theory of filler reinforcement of polymers predicts that a boundary layer of a matrix material is formed on the surface of the filler [1,2]. The thickness of layer depends on the strength of the interaction, with stronger interaction producing a larger thickness.…”

Section: Introductionmentioning

confidence: 99%

High Strain Rate Response of Sandwich Composites with Nanophased Cores

et al. 2005

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Polyurethane foam materials have been used as core materials in a sandwich construction with S2-Glass/SC-15 facings. The foam material has been manufactured from liquid polymer precursors of polyurethane. The precursors are made of two components; part-A (diphenylmethane diisocyanate) and part-B (polyol). In one set of experiments, part-A was mixed with part-B to manufacture the foam. In another set, TiO 2 nanoparticles have been dispersed in part-A through ultrasonic cavitation technique. The loading of nanoparticles was 3% by weight of the total polymer precursor. The TiO 2 nanoparticles were spherical in shape, and were about 29 nm in diameter. Sonic cavitation was carried out with a vibrasound liquid processor at 20 kHz frequency with a power intensity of about 100 kW/m 2 . The two categories of foams manufactured in this manner were termed as neat and nanophased. Sandwich composites were then fabricated using these two categories of core materials using a co-injection resin transfer molding (CIRTM) technique. Test samples extracted from the panel were subjected to quasi-static as well as high strain rate loadings. Rate of loading varied from 0.002 s −1 to around 1300 s −1 . It has been observed that infusion of nanoparticles had a direct correlation with the cell geometry. The cell dimensions increased by about 46% with particle infusion suggesting that nanoparticles might have worked as catalysts during the foaming process. Correspondingly, enhancement in thermal properties was also noticed especially in the TGA experiments. There was also a significant improvement in mechanical properties due to nanoparticle infusion. Average increase in sandwich strength and energy absorption with nanophased cores was between 40-60% over their neat counterparts. Details of manufacturing and analyses of thermal and mechanical tests are presented in this paper.

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Section: Introductionmentioning

confidence: 99%

High Strain Rate Response of Sandwich Composites with Nanophased Cores

et al. 2005

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“…In a gelatin-stabilized emulsion, the weight W 970 fraction of adsorbed protein on the oil droplets is given by wa = 6FgR/Odv s, (3) where 0 is the oil density, F is the areal concentration at the oil-water interface, and dvs is the mean droplet diameter defined by dvs = ~i nid3i/~i hid2 (4) for a dispersion containing ni droplets of diameter di.…”

Section: Introductionmentioning

confidence: 99%

“…The shear modulus G of a rubberlike network containing randomly-distributed filler particles can be written as [3] G = Go (1 + k,~ + k2# + ...),…”

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confidence: 99%

An adsorption effect on the gel strength of dilute gelatin-stabilized oil-in-water emulsions

Dickinson

Stainsby

Wilson

1985

Colloid & Polymer Sci

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Abstract:The incorporation of emulsion oil droplets into a gelatin gel leads to an initial increase in shear modulus at 25 ~ for a gelatin concentration of 8 wt % but an initial decrease for a concentration of 5 wt %. The latter resuIt is consistent with a net lowering of the gelatin concentration available for gelation in the aqueous phase due to adsorption at the oil-water interface.Key words: Gelatin, emulsion, gel, shear modulus, adsorption.Incorporating filler particles into a gelatin gel matrix normally has the effect of increasing the gel strength [1,2]. It is not obvious, however, that this will always be the case for weak gelatin gels in which a substantial proportion of the protein may become adsorbed on the particles and hence be unavailable for bulk-phase gelation. In this Note, we predict that under certain conditions a minimum should be observed in a plot of gel strength against particle volume fraction, and we test the theory against shear modulus data on dilute viscoelastic oil-in-water emulsions in which gelatin acts both as an emulsifier and a gelling agent.The shear modulus G of a rubberlike network containing randomly-distributed filler particles can be written as [3]where Go is the modulus of the unfilled network, ~ is the particle volume fraction, and kl, k2, etc., are constants. The dependence of the gelatin gel elasticity on polymer concentration can be represented by the equationwhere K1 is an elastic constant, w i is the weight fraction of free (unadsorbed) polymer, and wc is the critical polymer concentranon for the onset of gdation. In a gelatin-stabilized emulsion, the weight W 970 fraction of adsorbed protein on the oil droplets is given by wa = 6FgR/Odv s, (3) where 0 is the oil density, F is the areal concentration at the oil-water interface, and dvs is the mean droplet diameter defined by dvs = ~i nid3i/~i hid2 (4) for a dispersion containing ni droplets of diameter di.Taking w = wf + wa as the total concentration of gelatin in the whole emulsion, we obtain the following expression for the emulsion shear modulus to order ~2:The parameter K2 is given by K2 = 6r/o(w -we)&. (6) Differentiation of equation (5) shows that, if a minimum does occur in a plot of G versus ~, the volume fraction at the minimum will be Cmin ---~ (2K2 -hl)/2 (K22 + k2 -2h,K2).(7)

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“…After such a shape is chosen, one must scale the fiber and the interphase dimension to match their respective volume fractions. This latter dimension is especially difficult to obtain, though experimental means have been reported [24]. As mentioned earlier, the interphase is often modeled as an isotropic region in order to avoid mathematical complexity.…”

Section: Opportunities In Micromechanical Modelingmentioning

confidence: 99%

Interface/Interphase Concepts in Composite Material Systems

Swain

Reifsnider

Jayaraman

et al. 1990

Journal of Thermoplastic Composite Materials

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The influence of interfaces and interphases on the mechanical behavior of composite materials has been widely discussed in the literature, particularly in the last few years. Several books have been devoted to the subject. Despite this fact, the systematic representation of the mechanics of this subject remains grossly incomplete, and because of this, no consistent approach has been developed towards the determination of the influence of the interphase on the properties and performance of composite materials and laminates.The present paper advances a fundamental approach to this subject. The approach is based on the premise that the "composite effect"—that which defines the difference between the mechanical response of constituents acting without interaction and the response when they are bonded rigidly together — is the proper definition of the mechanical effect of the interphase. Within these two bounds, the "real" situation is determined by the extent of this interaction. The present paper attempts to specify these two bounds for typical loading and material situations. The nature of the boundary value problems associated with the two extremes as well as the intermediate cases is discussed.The incorporation of an interphasial region into micromechanical analyses of composite stiffness and strength will necessitate a reevaluation of the boundary value problem. The anisotropic, inhomogeneous, time-dependent quality of the interphase demands a more thorough treatment in existing micromechanical models. Yet, the level of complexity modeled is limited by our ability to measure interphasial properties. The interphase offers a wealth of opportunity on both analytical and experimental aspects of the problem.

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Relaxation and viscoelastic properties of heterogeneous polymeric compositions

Cited by 70 publications

References 62 publications

High Strain Rate Response of Sandwich Composites with Nanophased Cores

High Strain Rate Response of Sandwich Composites with Nanophased Cores

An adsorption effect on the gel strength of dilute gelatin-stabilized oil-in-water emulsions

Interface/Interphase Concepts in Composite Material Systems

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