Epoxy-Glass Microballoon Syntactic Foams: Rheological Optimization of the Processing Window

Ullas, A.V.; Kumar, Devendra; Roy, Prasun Kumar

doi:10.1155/2019/9180302

Cited by 16 publications

(9 citation statements)

References 50 publications

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“…The results of these tests are illustrated in Figure 2 b, which reports the natural logarithm of t gel as a function of 1000/T and the values of activation energy of crosslinking determined from the slope of the linear regressions. Interestingly, the activation energy is not significantly different in the four analyzed compositions, as is found in previous studies on epoxy/HGM systems [ 44 ]. This suggests that the inclusion of PCM and/or HGM does not influence the crosslinking mechanism of the epoxy resin and does not narrow the processing window.…”

Section: Resultssupporting

confidence: 81%

Thermophysical Properties of Multifunctional Syntactic Foams Containing Phase Change Microcapsules for Thermal Energy Storage

Galvagnini¹,

Dorigato²,

Fambri³

et al. 2021

Polymers

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Syntactic foams (SFs) combining an epoxy resin and hollow glass microspheres (HGM) feature a unique combination of low density, high mechanical properties, and low thermal conductivity which can be tuned according to specific applications. In this work, the versatility of epoxy/HGM SFs was further expanded by adding a microencapsulated phase change material (PCM) providing thermal energy storage (TES) ability at a phase change temperature of 43 °C. At this aim, fifteen epoxy (HGM/PCM) compositions with a total filler content (HGM + PCM) of up to 40 vol% were prepared and characterized. The experimental results were fitted with statistical models, which resulted in ternary diagrams that visually represented the properties of the ternary systems and simplified trend identification. Dynamic rheological tests showed that the PCM increased the viscosity of the epoxy resin more than HGM due to the smaller average size (20 µm vs. 60 µm) and that the systems containing both HGM and PCM showed lower viscosity than those containing only one filler type, due to the higher packing efficiency of bimodal filler distributions. HGM strongly reduced the gravimetric density and the thermal insulation properties. In fact, the sample with 40 vol% of HGM showed a density of 0.735 g/cm3 (−35% than neat epoxy) and a thermal conductivity of 0.12 W/(m∙K) (−40% than neat epoxy). Moreover, the increase in the PCM content increased the specific phase change enthalpy, which was up to 68 J/g for the sample with 40 vol% of PCM, with a consequent improvement in the thermal management ability that was also evidenced by temperature profiling tests in transient heating and cooling regimes. Finally, dynamical mechanical thermal analysis (DMTA) showed that both fillers decreased the storage modulus but generally increased the storage modulus normalized by density (E′/ρ) up to 2440 MPa/(g/cm3) at 25 °C with 40 vol% of HGM (+48% than neat epoxy). These results confirmed that the main asset of these ternary multifunctional syntactic foams is their versatility, as the composition can be tuned to reach the property set that best matches the application requirements in terms of TES ability, thermal insulation, and low density.

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Section: Resultssupporting

confidence: 81%

Thermophysical Properties of Multifunctional Syntactic Foams Containing Phase Change Microcapsules for Thermal Energy Storage

Galvagnini¹,

Dorigato²,

Fambri³

et al. 2021

Polymers

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“…Finally, the crosslinking reaction completes and the final viscosities of neat epoxy and glass microballoon filled composition become equal. 35…”

Section: Resultsmentioning

confidence: 99%

“…Finally, the crosslinking reaction completes and the final viscosities of neat epoxy and glass microballoon filled composition become equal. 35 The curing of epoxy in the presence of hardener leads to a concomitant increase in both the storage modulus and loss modulus. The variation of complex viscosity as a function of curing time during time sweep experiments performed isothermally at 60 � C are presented in Figure 2(a).…”

Section: Rheological Studiesmentioning

confidence: 99%

Exfoliated two-dimensional molybdenum disulfide reinforced epoxy syntactic foams

Ullas

Kumar

Roy

2021

Journal of Cellular Plastics

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In this paper, we report the effect of introducing molybdenum disulfide (MoS2) nano-platelets: a two-dimensional metal chalcogenide, on the mechanical properties of hollow glass microballoon (HGM)–epoxy syntactic foams. MoS2 reinforced syntactic foams were prepared by mixing MoS2 nanoplatelets to epoxy containing HGMs; with the amount of MoS2 being varied from 0.01 to 0.04% v/v, while maintaining a constant total filler volume fraction of 40% for all compositions. The mechanical behaviour of reinforced syntactic foam was studied under varied loadings including compressive, tensile and flexural under different strain rate regimes. Introduction of MoS2 led to significant improvements in characteristic mechanical properties, particularly in terms of compressive strength and toughness, which suggest intercalation of MoS2 within the epoxy matrix; however, the presence of relatively larger MoS2 micro particles couldn’t be completely negated. The toughness of the foam, as indicated by the area under the compressive stress-strain curve, was found to increase by ∼21% under optimal conditions. Our results highlight the potential of the two-dimensional MoS2 sheets as a reinforcing agent in syntactic foams.

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“…Detailed rheological studies on microballoon-polymer resin systems have been discussed elsewhere. 14,15 A representative increases in viscosity of the silicone resin due to introduction of HGMs is presented in Figure 2. It can be seen that the viscosity increases nonlinearly upon addition of microballoons and solventless processing of formulations is practically impossible at microballoon loadings >40%.…”

Section: Density Of Syntactic Foamsmentioning

confidence: 99%

Flexible silicone‐hollow glass microballoon syntactic foams for application in fire protective clothing

Tripathi

Parthasarathy

Yadav

et al. 2022

J of Applied Polymer Sci

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This work deals with the development of flexible syntactic foams based on silicone and hollow glass microballoons (HGMs) for potential application as a lightweight thermal cum vapor barrier in fire-protective ensembles. HGMs offer excellent thermal insulation and their inclusion into silicone leads to significant weight reduction, while improving the level of protection. Flexible silicone foams containing different types and loadings of HGMs were prepared and it was observed that high-density microballoons (K46) survived compression molding process, due to their superior crushing strength (6000 psi) as compared to K15 (300 psi). The specific quasi-static mechanical properties increased proportionally to the extent of loading. The inclusion of HGMs did not alter the curing behavior of silicone resin. Syntactic foams (40% HGMs) were coated onto glass fabric (GF) to prepare composites and thermal protective performance tests were performed to establish their effect on heat transfer. The protection level was higher for syntactic foam containing K46 glass microballoons, as compared to K15. The second-degree burn time increased from 6.4 s (neat GF) to 10s for syntactic foam-coated GF. Our studies demonstrate the potential of the developed syntactic foam-coated GFs as a vapor cum thermal barrier in fire protective clothing.

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Epoxy-Glass Microballoon Syntactic Foams: Rheological Optimization of the Processing Window

Cited by 16 publications

References 50 publications

Thermophysical Properties of Multifunctional Syntactic Foams Containing Phase Change Microcapsules for Thermal Energy Storage

Thermophysical Properties of Multifunctional Syntactic Foams Containing Phase Change Microcapsules for Thermal Energy Storage

Exfoliated two-dimensional molybdenum disulfide reinforced epoxy syntactic foams

Flexible silicone‐hollow glass microballoon syntactic foams for application in fire protective clothing

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