Characterization and comparison of properties of cryogenic conditioned CNT reinforced thermoset (epoxy) and thermoplastic (poly vinyl alcohol) composite yarns

Carbon nanotube (CNT) fiber/yarn reinforced composites are considered as a new generation of advanced materials for applications in aerospace and space industry. In this study, two types of CNT composite yarns were produced by twisting CNT films and infiltrating with thermoset epoxy (EP) and thermoplastic poly vinyl alcohol (PVA) resins. The tensile strength of CNT/PVA and CNT/EP composite yarn was 409.91 MPa and 206.87 MPa, much higher than that of pure CNT yarn (129.94 MPa). After mono-cryogenic condition, the mechanical and electrical properties of CNT/EP and CNT/PVA composite yarns were both enhanced due to the structure reorder of the CNT bundles and improvement of interfacial bonding. However, after 60 times cyclic-cryogenic conditions, CNT/EP composite yarn showed a ∼10% degradation of tensile strength; while CNT/PVA composite yarn exhibited 6% increment. This study provides fundamental data of the CNT reinforced thermoset and thermoplastic composite yarns for their practical applications in cryogenic environment.

Prediction of statistical life time for unidirectional CFRTP under cyclic loading

Recently, the Innovative Composite Center of Kanazawa Institute of Technology developed a thermoplastic epoxy resin (TP-EP). Resin-impregnated carbon fiber reinforced TP-EP (CF/TP) strands molded by pultrusion were developed by Komatsu Matere Co., Ltd., for use as tension rods. This study examines the prediction of the statistical life time for these developed CF/TP strands under cyclic tension loading with comparison to our earlier report of similar predictions for carbon fiber reinforced thermoset epoxy resin (CF/TS) strands having a thermoset epoxy resin (TS-EP) as a matrix. First, test methods for static and fatigue strengths at elevated temperatures were developed for CF/TP strands. Second, static and fatigue tensile strengths of CF/TP strands were measured statistically at various constant temperatures under a constant strain rate and frequency. The master curves of statistical fatigue tensile strengths for CF/TP strands were constructed by substituting the measured data into the formulations of these strengths based on the matrix resin viscoelasticity. The fatigue strength characteristics of CF/TP strands were discussed through comparison to those of CF/TS strands with thermosetting epoxy resin as the matrix.

Seawater Absorption and Adhesion Properties of Hydrophobic and Superhydrophobic Thermoset Epoxy Nanocomposite Coatings

The enhancement of both thermal and mechanical properties of epoxy materials using nanomaterials becomes a target in coating of the steel to protect it from aggressive environmental conditions for a long time, with reducing the cost. In this respect, the adhesion properties of the epoxy with the steel surfaces, and its proper superhyrophobicity to repel the seawater humidity, can be optimized via addition of green nanoparticles (NPs). In-situ modification of silver (Ag) and calcium carbonate (CaCO3) NPs with oleic acid (OA) was carried out during the formation of Ag−OA and CaCO3−OA, respectively. The epoxide oleic acid (EOA) was also used as capping for Ca−O3 NPs by in-situ method and epoxidation of Ag−OA NPs, too. The morphology, thermal stability, and the diameters of NPs, as well as their dispersion in organic solvent, were investigated. The effects of the prepared NPs on the exothermic curing of the epoxy resins in the presence of polyamines, flexibility or rigidity of epoxy coatings, wettability, and coatings durability in aggressive seawater environment were studied. The obtained results confirmed that the proper superhyrophobicity, coating adhesion, and thermal stability of the epoxy were improved after exposure to salt spray fog for 2000 h at 36 °C.

Nanostructured Thermoset Blends Induced by Self-assembly of Polyisoprene-bpoly(4vinyl pyridine) Diblock Copolymer Blended with Thermoset Epoxy

Nanostructured thermoset blends were prepared based on a bisphenol A-type epoxyresin and an amphiphilic reactive diblock copolymer, namely polyisopreneblockpoly(4-vinyl pyridine) (PI-P4VP). Infrared spectra revealed that the P4VP blockof the diblock copolymer reacted with the epoxy monomer. However, the non-reactivehydrophobic PI block of the diblock copolymer formed a separate microphase on thenanoscale. Ozone treatment was used to create nanoporosity in nanostructuredepoxy/PI-P4VP blends via selective removal of the PI microphase and lead tonanoporous epoxy thermosets; disordered nanopores with the average diameter of about60 nm were uniformly distributed in the blend with 50 wt% PI-P4VP. Multi-scale phaseseparation with a distinctly different morphology was observed at the air/sampleinterface due to the interfacial effects, whereas only uniform microphase separatedmorphology at the nanoscale was found in the bulk of the blend.

Study of Curing Characteristics of Cellulose Nanofiber-Filled Epoxy Nanocomposites

In recent years, much attention was focused on developing green materials and fillers for polymer composites. This work is about the development of such green nanofiller for reinforcement in epoxy polymer matrix. A cellulose nanofiber (CNF)-filled epoxy polymer nanocomposites was prepared in this work. The effect of CNF on curing, thermal, mechanical, and barrier properties of epoxy polymer is evaluated in this study. CNF were extracted from banana fiber using acid hydrolysis method and then filled in epoxy polymer at various concentration (0–5 wt.%) to form CNF-filled epoxy nanocomposites. The structure and morphology of the CNF-filled epoxy nanocomposites were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis. Curing studies shows CNF particles acts as a catalytic curing agent with increased cross-link density. This catalytic effect of CNF particles has positively affected tensile, thermal (thermogravimetry analysis and dynamic mechanical analysis) and water barrier properties. Water uptake test of nanocomposites was studied to understand the barrier properties. Overall result also shows that the CNF can be a potential green nanofiller for thermoset epoxy polymer with promising applications ahead.