On depression of glass transition temperature of epoxy nanocomposites

Liu, Gang; Zhang, Daijun; Zhang, Hui; Zhong, Ziyi; An, Xiaobo; Yi, Xiaosu

doi:10.1007/s10853-012-6633-6

Cited by 21 publications

(18 citation statements)

References 33 publications

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“…Depressing of T g has been observed before in inorganic nanoparticle-reinforced epoxy composite systems. 34,[36][37][38] Tang and Weder also observed depressing of T g at low CNC content in aromatic hardener-cured epoxy. 25 However, T g of the cured epoxy increased when the CNC content increased, as the CNC formed a rigid percolation network, which limited the movment of polymer chains.…”

Section: Green Materialsmentioning

confidence: 79%

“…32 In addition, Liu et al suggested that nanoparticles could also selectively absorb resin or hardener at their surface, thus limiting the reaction between the epoxy resin and hardener. 36 In this study, since CNC was exposed with hardener first, the weak hydrogen bonding interactions between the CNCs and hardeners could possibly inhibit the epoxy/hardener reaction. These weak interactions of the hardeners, acetone, and CNCs could have caused incomplete curing in some regions of the epoxy and led to the formation of inhomogeneous crosslinking networks.…”

Section: Green Materialsmentioning

confidence: 90%

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Design and characterization of cellulose nanocrystal-enhanced epoxy hardeners

2014

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Cellulose nanocrystals (CNCs) are renewable, sustainable, and abundant nanomaterial widely used as reinforcing fillers in the field of polymer nanocomposites. In this study, two-part epoxy systems with CNC-enhanced hardeners were fabricated. Three types of hardeners, Jeffamine D400 (JD400), diethylenetriamine (DETA), and (±)-trans-1,2-diaminocyclohexane (DACH), were evaluated for their compatibility with CNC. The roles of CNC additions and hardener types in epoxy properties were analyzed with tensile testing and dynamic mechanical analysis. The CNC-reinforcing effects on epoxy depended on the structure of hardeners. For example, with less than 2 wt% CNC, Young's modulus was increased by 16% in JD400-cured epoxy and by 19% in DETA-cured epoxy, but had minimal effect for the DACHcured epoxy. In general, the DETA-cured specimens had the highest increases in mechanical properties among the three hardeners evaluated. These results indicate that CNC additions to pre-formulated hardeners could be an alternative approach for dispersing CNCs within epoxy matrices and for improving the mechanical properties of epoxy. However, residual acetone and water during the curing reaction plasticized the epoxy matrices and must be limited for further property improvements.

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Section: Green Materialsmentioning

confidence: 79%

Section: Green Materialsmentioning

confidence: 90%

Design and characterization of cellulose nanocrystal-enhanced epoxy hardeners

2014

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“…The observed T g trend could be due to the occurrence of two concurrent phenomena: as the filler content increases the chain blocking effect is more effective and induces a slight T g increase, while, at the same time, polymer-filler chemical interactions and the viscosity increase reduces the crosslinking degree of the matrix, with a consequent T g drop. In a recent investigation on epoxy/alumina nanocomposites, Liu et al [38] speculated that the hardener molecules were unevenly distributed at a microscale, thus leading to a stoichiometric imbalance between epoxy components and reduced T g values.…”

Section: Thermal Propertiesmentioning

confidence: 99%

Electrically conductive epoxy nanocomposites containing carbonaceous fillers and in-situ generated silver nanoparticles

Dorigato¹,

Giusti²,

Bondioli³

et al. 2013

Express Polym. Lett.

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Abstract. An epoxy resin was nanomodified with in-situ generated silver nanoparticles (Ag) and with various amounts of carbon black (CB) and carbon nanofibers (NF), in order to increase the electrical conductivity of the matrix. Differential scanning calorimetry tests revealed how the addition of both CB and NF led to a slight decrease of the glass transition temperature of the material, while electron microscopy evidenced how the dimension of CB aggregates increased with the filler content. Both flexural modulus and stress at yield were decreased by CB addition, and the introduction of Ag nanoparticles promoted an interesting improvement of the flexural resistance. CB resulted to be more effective than NF in decreasing the electrical resistance of the materials down to 10 3 !·cm. Therefore, a rapid heating of the CB-filled samples upon voltage application was observed, while Ag nanoparticles allowed a stabilization of the temperature for elevated voltage application times.

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“…As already reported in our previous paper on similar epoxy systems , the observed T g trend could be due to the occurrence of two concurrent phenomena: as the filler content increases the chain blocking mechanisms is more effective and leads to a slight T g increase, while, at the same time, polymer‐filler chemical interactions and the viscosity increase reduces the crosslinking degree of the matrix, thus reducing the T g of the material. As recently reported by Liu et al on epoxy/alumina nanocomposites, the hardener molecules were unevenly distributed at a microscale, leading to a stoichiometric imbalance between epoxy components and reduced T g values.…”

Section: Resultsmentioning

confidence: 51%

Shape memory epoxy nanocomposites with carbonaceous fillers and in‐situ generated silver nanoparticles

Dorigato

Pegoretti

2018

Polymer Engineering & Sci

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Aim of this work is to develop a novel epoxy based nanocomposite and to analyse its shape memory behavior. In particular, silver nanoparticles are in‐situ generated within an epoxy resin subsequently filled with both carbon black (CB) and carbon nanofibers (NFs) at different ratios and at a total amount of 4 wt%. Differential scanning calorimetry shows how the introduction of both CB and NF induces a slight decrease of the glass transition temperature (Tg) of the samples. The Tg drop due to nanofiller addition determines a decrease of both flexural modulus and stress at yield with respect to the neat resin, especially at elevated CB concentrations, while the presence of Ag nanoparticles plays a positive effect on the flexural properties. The best mechanical properties can be detected at a CF/NF ratio of 50%, coupled with a noticeable decrease of the electrical resistivity down to 102 Ω·cm and an interesting heating capability through Joule effect. The electro‐mechanical shape‐memory characterization under bending configuration demonstrates how it is possible to obtain an almost complete shape recovery after 60 s under an applied voltage of 220 V. POLYM. ENG. SCI., 59:694–703, 2019. © 2018 Society of Plastics Engineers

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On depression of glass transition temperature of epoxy nanocomposites

Cited by 21 publications

References 33 publications

Design and characterization of cellulose nanocrystal-enhanced epoxy hardeners

Design and characterization of cellulose nanocrystal-enhanced epoxy hardeners

Electrically conductive epoxy nanocomposites containing carbonaceous fillers and in-situ generated silver nanoparticles

Shape memory epoxy nanocomposites with carbonaceous fillers and in‐situ generated silver nanoparticles

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