Abstract: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 syntact… Show more
“…This result could be attributed to the small cell size of EP/12h-RGO foam and strengthening effect of nanofillers. 39 Figure 9.(a) Compressive stress-strain curves and (b) specific compressive properties of EP and EP/RGO foams.…”
Section: Resultsmentioning
confidence: 99%
“…This result could be attributed to the small cell size of EP/12h-RGO foam and strengthening effect of nanofillers. 39 The specific compressive strength and modulus, which is defined as strength and modulus divided by density, of EP and EP/RGO foams are illustrated in Figure 9(b). It can be seen that the specific compressive strength and modulus of EP/RGO foams increased with increasing the reduction time of RGO.…”
Section: Characterization Of Ep/rgo Composite Foamsmentioning
In this study, N-aminoethylpiperazine (AEP)-functionalized and reduced graphene oxide (RGO) with different structures and properties was prepared by simply tuning the reduction time and then its effect on the rheological, curing and foaming behavior of epoxy resin was carefully investigated using the environment-friendly carbamate as a chemical foaming agent. As the reduction time of RGO increased, the reduction degree of RGO first increased and then levelled off but the grafted AEP was little affected by the reduction time. The addition of RGO undergoing long reduction time improved the viscoelasticity of epoxy/reduced graphene oxide (EP/RGO) composites but weakened the interfacial compatibility of RGO and EP. With increasing the reduction time of RGO, the cell size of EP/RGO composite foams decreased and the cell density increased. However, as compared with pure EP foam, the composite foams containing RGO with lower reduction degree had a larger cell size and a lower density. These results were attributed to the complicated effect of RGO, which not only acted as the heterogeneous nucleating and foaming agent but also affected the viscoelasticity of composites. In addition, as the reduction time of RGO increased, the initial thermal decomposition temperature, storage modulus at room temperature, electrical conductivity, thermal conductivity, and compressive properties of EP/RGO composite foams increased while the glass transition temperature remained unchanged. These results were related not only to the intrinsic properties and dispersion of RGO, but also to the density and cell morphology of the composite foams.
“…This result could be attributed to the small cell size of EP/12h-RGO foam and strengthening effect of nanofillers. 39 Figure 9.(a) Compressive stress-strain curves and (b) specific compressive properties of EP and EP/RGO foams.…”
Section: Resultsmentioning
confidence: 99%
“…This result could be attributed to the small cell size of EP/12h-RGO foam and strengthening effect of nanofillers. 39 The specific compressive strength and modulus, which is defined as strength and modulus divided by density, of EP and EP/RGO foams are illustrated in Figure 9(b). It can be seen that the specific compressive strength and modulus of EP/RGO foams increased with increasing the reduction time of RGO.…”
Section: Characterization Of Ep/rgo Composite Foamsmentioning
In this study, N-aminoethylpiperazine (AEP)-functionalized and reduced graphene oxide (RGO) with different structures and properties was prepared by simply tuning the reduction time and then its effect on the rheological, curing and foaming behavior of epoxy resin was carefully investigated using the environment-friendly carbamate as a chemical foaming agent. As the reduction time of RGO increased, the reduction degree of RGO first increased and then levelled off but the grafted AEP was little affected by the reduction time. The addition of RGO undergoing long reduction time improved the viscoelasticity of epoxy/reduced graphene oxide (EP/RGO) composites but weakened the interfacial compatibility of RGO and EP. With increasing the reduction time of RGO, the cell size of EP/RGO composite foams decreased and the cell density increased. However, as compared with pure EP foam, the composite foams containing RGO with lower reduction degree had a larger cell size and a lower density. These results were attributed to the complicated effect of RGO, which not only acted as the heterogeneous nucleating and foaming agent but also affected the viscoelasticity of composites. In addition, as the reduction time of RGO increased, the initial thermal decomposition temperature, storage modulus at room temperature, electrical conductivity, thermal conductivity, and compressive properties of EP/RGO composite foams increased while the glass transition temperature remained unchanged. These results were related not only to the intrinsic properties and dispersion of RGO, but also to the density and cell morphology of the composite foams.
“…Epoxy foam is also fabricated by applying an aqueous emulsion-template [7]. Besides, epoxy syntactic foams are produced by the addition of microballoons [8][9][10]. Compared to foaming techniques, epoxy-carbamate foaming offers a better way to control the density and the cellular structure of the final epoxy foam [11][12][13].…”
The use of carbamate to foam epoxy depends significantly on the precured modulus to stabilize the cellular structure. The optimum precured modulus is developed from the reaction of epoxy resin and the neat amine. The selection of the neat amine relies on its reaction temperature with epoxy, which is required to be below the decomposition temperature of carbamate. This study investigates the effect of three different neat amines on the rheological behavior of foaming epoxy-carbamate-amine. They are bisphenol-A diglycidyl ether epoxy (DGEBA), isophorone diamine carbamate (IDPA.CO2), N-aminoethylpiperazine (AEP), 2,4-Diamino-1-methyl-cyclohexan (DMC) and isophorone diamine (IDPA). The mixtures of DGEBA-amine-carbamate are filled in 25% and 75% of the volume of a closed mold. Precuring is carried out at 60°C for 2 h. The foaming and complete curing are conducted at 180°C for 1 h. Having H-active at piperazine, AEP reacts with DGEBA faster and develops a higher precured modulus compared to DMC and IDPA. It is important to note that DGEBA-AEP-IDPA.CO2 exhibits viscoelastic behavior beyond 138°C, seen by its rheological storage modulus lower than loss modulus and its tan delta larger than 1. The reaction between DGEBA and the H-active piperazine of AEP leads only to linear linkage and is unable to further crosslink compared to the primary amine (-NH2). This results in a lower glass transition temperature Tg of DGEBA-AEP-IPDA.CO2. The effect of amine on foaming is more obviously at 25% filling level. DGEBA-AEP-IPDA.CO2 has more spherical and homogeneous cellular structure and the density of 285 kg/m3. Having quite similar chemical structure, both DGEBA-DMC-IPDA.CO2 and DGEBA-IPDA-IPDA.CO2 produce the epoxy foams having cell-interconnection and coalescence; their densities are also similar 301 kg/m3 and 305 kg/m3, respectively. All the foams are closed-cell at 75% of filling level. The cell morphologies are well reflecting the foaming modulus and tan delta behavior.
“…A variety of polymer matrices have been used both thermosets and thermoplastics, etc. 5–8 Similarly, glass, 9 polymer 10,11 and other varieties of hollow microballoons 12 have been used for the fabrication of syntactic foam. The type and volume fraction of matrix and microballoons can be altered to prepare a wide range of materials with contrasting properties.…”
Polymer syntactic foams are lightweight polymer composites that are prepared by introducing hollow microspheres in a resin. The main endeavour is to obtain a significant reduction in the weight of the composite along with energy absorption. The present investigation aims to prepare poly (dimethylsiloxane) (PDMS)-hollow glass microballoons (HGM) (40–60% v/v) syntactic foams. Not only did HGM reduce the density of the syntactic foams but also act as a reinforcing phase and increase the compressive properties of PDMS. A ∼25% reduction in density was obtained in syntactic foam when compared to the neat elastomer. Similarly, an improvement of ∼118% in compressive strength was attained at 40% loading of HGM in PDMS. Specific compressive strength and toughness values also registered improvements of the order of ∼191 and ∼240% respectively which highlight the potential of PDMS syntactic foams in varied applications.
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