Evolution of viscoelastic properties of polyurethane in the course of curing

Malkin, A. Ya.; Bolgov, S.A.; Begishev, V. P.; Mansurov, V. A.

doi:10.1007/bf00418331

Cited by 12 publications

(8 citation statements)

References 9 publications

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“…The curing degree α can be related to the variation of elastic modulus: 38 where G0′, G′(t) and G∞′ are the values of elastic modulus at the beginning of the reaction, time t and the end of curing reaction, respectively.…”

Section: Resultsmentioning

confidence: 99%

Experimental and numerical study of the polyurethane foaming process using high-pressure CO₂

Zhou

Liu

et al. 2020

Journal of Cellular Plastics

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A simulation of simultaneous bubble nucleation and growth was performed for polyurethane/CO2 physical foaming process. The single-factor and comprehensive effects of viscoelastic properties, Henry’s constant, CO2 diffusion coefficient and surface tension on the cell morphology were numerically analyzed. The results show that the cell density of PU foam ( N0) increases and its average cell diameter ( Dv) reduces with increased Henry’s constant and slower gas diffusion. Both N0 and Dv reduces with the curing degree ( α). In addition, the effects of α and foaming conditions on the cell structure were experimentally investigated. With an increase of α at foamable range, Dv decreases continuously and N0 increases first and then declines. With increasing saturation pressure and depressurization rate or decreasing temperature, N0 increases and Dv reduces. There is an intrinsic correlation between the simulated and experimental variables, and the results of the simulation and experiment are generally consistent.

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Section: Resultsmentioning

confidence: 99%

Experimental and numerical study of the polyurethane foaming process using high-pressure CO₂

Zhou

Liu

et al. 2020

Journal of Cellular Plastics

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“…72,73 The micro-foams in the RHPU grouting materials which have lower density have more irregular shapes and thinner walls, 16,18 and thus the smaller stiffness against deformation 34 ; therefore, under the same external load, the unrecoverable deformation of the lower-density RHPU grouting materials is larger (as shown in Figure 4), indicating the more obvious viscous mechanical behavior. 73 The more obvious the viscous mechanical behavior of the material, the more easily its mechanical properties are affected by the loading rate 74 ; therefore, the loading rate has greater influences on the mechanical properties of RHPU grouting materials with a lower density. In practical application, according to the monitoring results of soil deformation, the real strain rate of the RHPU grouting materials can be converted, and the mechanical properties can be evaluated based on the results of here.…”

Section: The Influences Of Loading Ratementioning

confidence: 99%

Study of the mechanical properties and constitutive model of the roadbed rehabilitation polyurethane grouting materials under uniaxial compression

Fang

Zheng

et al. 2022

J of Applied Polymer Sci

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Polyurethane grouting materials are increasingly used in the non-excavation rehabilitation of roadbeds. The compressive strength of roadbed rehabilitation polyurethane (RHPU) grouting materials is the key to achieving the desirable repair effect, whereas the constitutive model of RHPU grouting materials is not yet understood. Here, the mechanical properties of RHPU grouting materials under compression were experimentally investigated, followed by establishing the hyperfoam constitutive model. The variation laws of the critical parameters in the model with density were function fitted, and then the constitutive model was simplified as an equation of density as the single independent variable. The comparisons between the theoretical and experimental mechanical behavior of RHPU grouting materials were discussed to illustrate the applicability of the hyperfoam constitutive model. Results show that with the increasing density, both the yield strength (σ 1 ), elastic modulus (E 1 ), and secant modulus (E s ) increases exponentially, and the Poisson's ratio (v) increases logarithmically. The maximum increase in σ 1 , E 1 , E s , and v are about 750%, 720%, 940%, and 50%, respectively. Compared to the effects of density on the mechanical properties, the effect of loading rate is much smaller, and the side length has no effect. For RHPU samples with a density not exceeding 0.35 g/cm 3 , the hyperfoam model can well describe the uniaxial compression mechanical behavior, but for those whose density exceeds 0.35 g/cm 3 , the model can only describe the mechanical behavior before yielding. The theoretical yield strength of the RHPU samples obtained from the model is close to the experimental value (with differences of about 0.1%-14.4%). This study provides a base to evaluate the compressive strength of the practically used RHPU grouting materials based on the density.

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“…According to a strict definition, the gel-point is the moment of formation of the continuous molecular cluster. 31 In Table 3, the gel-point, t gel , is considered the crossover of tan δ curves from the rheological data recorded at various frequencies.…”

Section: Curing Rheokinetic Study At Gelationmentioning

confidence: 99%

Catalytic effects over formation of functional thermoplastic elastomers for rocket propellants

Lucio

Fuente

2021

Polymers for Advanced Techs

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Rheometry was the main method to characterize the curing process of binders made of functional polyurethanes (PUs). The macroglycols characterization by means of additional techniques, such as nuclear magnetic resonance, size exclusion chromatography, and differential scanning calorimetry, provided further information for the chemorheological description. Materials were based on Butacene ((ferrocenylbutyl) dimethylsilane grafted to hydroxyl-terminated polybutadiene (HTPB)), used in the solid propulsion field. First, the flow parameters for the uncured reactive mixtures of Butacene and four different diisocyanates were analyzed via viscometry and these were markedly influenced by the chemical structure of the curing agents. Analyzing the rheokinetic constant values of the pre-gel stage for Butacene-and HTPB-reactive systems, relevant catalysis caused by the ferrocene moiety was detected when aliphatic reactants were used, such as isophorone diisocyanate or 1,6-hexamethylene diisocyanate (IPDI and HMDI, respectively). No catalytic effect was found for 2,4-toluene diisocyanate (2,4-TDI) or even for 4,4 0 -methylenediphenyl diisocyanate (4,4 0 -MDI). Finally, the use of dynamic rheology was useful to evaluate the critical points during gelation process, where the reactivity of curing agents was associated with the achievement of elastic properties. Both techniques agreed the reactivity order of curing agents with Butacene, which is 4,4 0 -MDI > HMDI > > 2,4-TDI ≥ IPDI.The knowledge of the structure-reactivity relationship and, moreover, the kinetics of the urethane network formation for these metallo-PUs is paramount in manufacturing processes for advanced thermoplastic elastomer applications.

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Evolution of viscoelastic properties of polyurethane in the course of curing

Cited by 12 publications

References 9 publications

Experimental and numerical study of the polyurethane foaming process using high-pressure CO₂

Experimental and numerical study of the polyurethane foaming process using high-pressure CO₂

Study of the mechanical properties and constitutive model of the roadbed rehabilitation polyurethane grouting materials under uniaxial compression

Catalytic effects over formation of functional thermoplastic elastomers for rocket propellants

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Evolution of viscoelastic properties of polyurethane in the course of curing

Cited by 12 publications

References 9 publications

Experimental and numerical study of the polyurethane foaming process using high-pressure CO2

Experimental and numerical study of the polyurethane foaming process using high-pressure CO2

Study of the mechanical properties and constitutive model of the roadbed rehabilitation polyurethane grouting materials under uniaxial compression

Catalytic effects over formation of functional thermoplastic elastomers for rocket propellants

Contact Info

Product

Resources

About

Experimental and numerical study of the polyurethane foaming process using high-pressure CO₂

Experimental and numerical study of the polyurethane foaming process using high-pressure CO₂