Thermal Properties and Fracture Toughness of Epoxy Nanocomposites Loaded with Hyperbranched-Polymers-Based Core/Shell Nanoparticles
Abstract
:1. Introduction
2. Materials and Methods
2.1. Materials
2.2. CSNPs Synthesis
2.3. Nanocomposites Preparation
2.4. Characterization
3. Results and Discussion
3.1. CSNPs Characterization
3.2. CSNPs/RTM6 Nanocomposites Characterization
3.2.1. Dynamic Mechanical Properties
3.2.2. Thermal Stability
- A first degradation step up to 450 °C, which mainly involves dehydration (around 100 °C) of the material and formation of a poly-aromatic structure [22];
- A second step between 500–600 °C, characterized by thermo-oxidative reactions, which lead to the complete degradation of the carbonaceous materials and char formation [22].
- (1)
- At low CSNPs content (1 wt%), the activation energies of both degradation steps increased compared to the neat resin. This behavior can be explained assuming that CSNPs act as physical barriers both to postpone the thermal decomposition of volatile components and to prevent the transport phenomena of volatile decomposed products into the hosting matrix [24]. Therefore, at lower filler contents, the predominant effect associated with the presence of an inorganic core is an increase of the activation energy;
- (2)
- Higher CSNPs content (2.5 wt%) induces a reduction of both activation energies: In accordance with Zhou et al. [25], the HBP shell of the CSNPs can induce a lowering of activation energies associated with the reduction of the crosslink density in the hosting matrix. The energy reduction effect associated with the presence of the polymeric shell became more relevant compared to the sample filled at 1 wt% of CSNPs.
3.2.3. Fracture Toughness Results
- reduction of the crosslink density which affects the internal stress level induced during the epoxy cure [26];
- induction of a triaxial stress state in the matrix around CSNPs due to the presence of the inorganic core and thus promoting the plastic deformation mechanism in the polymeric phase and then crack tip blunting [27];
- further promotion of plastic deformation associated with the presence of the HBP shell [28].
4. Conclusions
Author Contributions
Funding
Acknowledgments
Conflicts of Interest
References
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Sample | Tg [°C] | Storage Modulus at 40 °C [MPa] |
---|---|---|
Neat RTM6 | 228.9 | 3107 ± 15 |
RTM6 + 1 wt% CSNPs | 226.8 | 3296 ± 21 |
RTM6 + 2.5 wt% CSNPs | 225.4 | 3392 ± 23 |
Sample | Tend set I (°C) | Tend set II (°C) | TPeak I (°C) | TPeak II (°C) | Char Yield (%) |
---|---|---|---|---|---|
Neat RTM6 | 407.9 | 612.7 | 387.0 | 584.1 | 0.06 |
RTM6 + 1 wt% CSNPs | 408.8 | 611.1 | 389.0 | 581.9 | 0.73 |
RTM6 + 2.5 wt% CSNPs | 406.7 | 621.8 | 393.0 | 595.9 | 1.61 |
Sample | EaI (KJ/mol) | EaII (KJ/mol) |
---|---|---|
Neat RTM6 | 103.5 | 110.6 |
RTM6 + 1 wt% CSNPs | 183.7 | 132.6 |
RTM6 + 2.5 wt% CSNPs | 152.0 | 90.6 |
Sample | KIC [MPa m1/2] | ΔKIC | % Variation KIC | GIC [KJ/m2] | ΔGIC | % Variation GIC |
---|---|---|---|---|---|---|
RTM6 Neat | 0.62 | 0.06 | - | 0.114 | 0.01 | - |
RTM6 + 1 wt% CSNPs | 0.76 | 0.07 | 22.6 | 0.185 | 0.03 | 62.3 |
RTM6 + 2.5 wt% CSNPs | 0.82 | 0.05 | 32.3 | 0.199 | 0.025 | 74.6 |
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Zotti, A.; Zuppolini, S.; Borriello, A.; Zarrelli, M. Thermal Properties and Fracture Toughness of Epoxy Nanocomposites Loaded with Hyperbranched-Polymers-Based Core/Shell Nanoparticles. Nanomaterials 2019, 9, 418. https://doi.org/10.3390/nano9030418
Zotti A, Zuppolini S, Borriello A, Zarrelli M. Thermal Properties and Fracture Toughness of Epoxy Nanocomposites Loaded with Hyperbranched-Polymers-Based Core/Shell Nanoparticles. Nanomaterials. 2019; 9(3):418. https://doi.org/10.3390/nano9030418
Chicago/Turabian StyleZotti, Aldobenedetto, Simona Zuppolini, Anna Borriello, and Mauro Zarrelli. 2019. "Thermal Properties and Fracture Toughness of Epoxy Nanocomposites Loaded with Hyperbranched-Polymers-Based Core/Shell Nanoparticles" Nanomaterials 9, no. 3: 418. https://doi.org/10.3390/nano9030418