A new type of phthalonitrile-etherified resole resin (PNR) was synthesized from resole resin and 4-nitrophthalonitrile. The differential scanning calorimetry results showed that the curing temperature of PNR is lower than that of phthalonitrile resin. Excellent thermal stability and bonding properties were obtained after curing at 220°C. TGA showed that in air, the temperature of 5% weight loss (T5%) of the cured PNR was 446°C, approximately 41°C higher than that of resole resin (RS), and the char yield at 800°C increased from 4% for RS to 33% for PNR. The shear strengths of PNR at room temperature and high temperature were increased by 8% and 133%, respectively, over those of RS, and after aging at 350°C for 2 h, these values were increased by 262% and 198%, respectively, over those of RS. Its excellent curing behavior, heat resistance and high bonding strength show that PNR can be used as a high temperature-resistant adhesive.
The influence of multi-pass cold drawing on the evolution of microstructure, texture, and properties of Cu matrix composite, reinforced by in situ grown graphene, has been systematically investigated. Under continuous and severe plastic deformation, the grains in the composite were continuously refined to nanoscale. In addition, graphene in the composite could be gradually refined, exfoliated, and redispersed. Interestingly, dynamic recrystallization of the composite was formed after 80% drawing reduction and its formation mechanism was discussed. The texture of the as-drawn composite comprised a mixture of fiber textures with dominated <111> and minor <100> orientation after 99.7% severe drawing reduction. The tensile properties and electrical conductivity of the as-drawn composites were also investigated. This work provides a better guideline on the plastic deformation behavior of the advanced graphene/metal nanocomposite.
The practical application of thermoresponsive poly(N‐isopropylacrylamide) (PNIPAM) hydrogels are severely limited by their poor mechanical properties. Herein, we reported a series of dual crosslinked (DC) PNIPAM hydrogels with superior mechanical properties prepared by simple copolymerization of N‐isopropylacrylamide and sodium acrylate (SA) in the laponite RDS suspension, following by a soaking process in multivalent metal cations (e.g., Ca2+, Al3+, Fe3+) aqueous solutions to form ionic coordination interactions with COO groups of copolymer side chains. The effect of laponite RDS, AANa (sodium acrylate), and metal cation (e.g., Fe3+) concentrations on the mechanical properties and deswelling properties of the DC hydrogels are evaluated. The DC hydrogel prepared with 10 w/v% laponite RDS, 0.25 mol/L AANa and 0.45 mol/L Fe3+ possesses the best mechanical properties (ca. 1.1 MPa of tensile strength, 9.1 MPa of compression strength at 80% of compression strain, 1.4 MPa of elastic modulus and 1.3 MJ/m3 of toughness). Moreover, we also discovered that the DC hydrogels crosslinked by Fe3+ showed better mechanical properties due to the larger charge and ion radius of Fe3+.
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