Nanodiamond tethered epoxy/polyurethane interpenetrating network nanocomposite: Physical properties and thermoresponsive shape-memory behavior

Effect of nanodiamond particles on the structure, mechanical, and thermal properties of polymer embedded ND/PMMA composites

Nanodiamonds (NDs), the allotropic carbon nanomaterials with nanosize, durable inert core, adjustable surface morphology, high thermal constancy, and super mechanical performances, possess the characteristics of promising reinforcement materials for various technological applications. However, ND particles hold a vigorous propensity to aggregate in liquid media, obstructing their implementation in mechanical and thermal sciences. This aggregation is caused by high surface to volume ratio. By reducing the surface energy and lowering cluster formation, the mechanical and thermal properties of NDs can be polished. Herein, we report on the covalent functionalization of NDs with amine moiety through ball milling method. Their dispersion was checked in ethanol and polymethyl methacrylate (PMMA polymer) against nonfunctionalized NDs. The dispersive behavior showed that ball mill functionalized NDs produced preferably stable aqueous dispersions in ethanol media. Furthermore, 0.1, 0.2, and 0.4 wt% ND/PMMA composites were synthesized, and their mechanical and thermal behaviors were studied in terms of hardness, compression, Young`s modulus, flexural strength, tensile strength, and thermogravimetric analysis (TGA). Results revealed that the composites containing 0.2 wt% functionalized ND loaded with PMMA matrix showed outstanding mechanical and thermal performances indicating that 0.2 wt% is the optimum amount for achieving excellent outcomes.

Shape memory polymer/graphene nanocomposites: State-of-the-art

Graphene is one of most exceptional type of nanocarbon. It is a two-dimensional, one atom thick, nanosheet of sp2 hybridized carbon atoms. Graphene has been employed as nanofiller for shape memory polymeric nanocomposites due to outstanding electrical conductivity, mechanical strength, flexibility, and thermal stability characteristics. Consequently, graphene nanostructures have been reinforced in the polymer matrices to attain superior structural, physical, and shape recovery properties. This review basically addresses the important class of shape memory polymer (SMP)/graphene nanocomposites. This assessment is revolutionary to portray the scientific development and advancement in the field of polymer and graphene-based shape memory nanocomposites. In SMP/graphene nanocomposites, polymer shape has been fixed at above transition temperature and then converted to memorized shape through desired external stimuli. Presence of graphene has caused fast switching of temporary shape to original shape in polymer/graphene nanocomposites. In this regard, better graphene dispersion, interactions between matrix-nanofiller, and well-matched interface formation leading to high performance stimuli-responsive graphene derived nanocomposites, have been described. Incidentally, the fabrication, properties, actuation ways, and relevance of the SMP/graphene nanocomposite have been discussed here. The potential applications of these materials have been perceived for the aerospace/automotive components, self-healing nanocomposites, textiles, civil engineering, and biomaterials.

Fabrication of short glass fiber reinforced phenol-formaldehyde-lignin and polyurethane-based composite foam: mechanical, friability, and shape memory studies

In this research effort, phenol-formaldehyde-lignin (PFL) resin was prepared using phenol, formaldehyde, and lignin via a simple approach. The PFL-polyurethane (PFL-PU) was prepared using PU prepolymer and PFL resin. The blend components were then foamed via addition of Tween 80 surfactant and n-pentane as the blowing agent. Short glass fiber was reinforced in the blend sample to attain high performance composite foams. The composite foams were characterized for structure, morphology, stress-strain behavior, friability tests, and shape memory characteristics. Scanning electron microscopy showed a layered, porous, and distorted hexagonal shaped foam structure. The cell size ranges from 10 to 20 μm for PFL-PU-short glass fiber (SGF) Foam with 10–20 wt.% fiber loading. PFL-PU Foam had compression strength and strain of 48.3 MPa and 48.2%. The PFL-PU-SGF 1–20 Foam showed increase in strength from 55.1 to 101.7 MPa and decrease in strain from 57.8% to 35.8% due to filler addition. At temperature above Tg (130°C), the strain was increased up to 45.11%. The shape fixity was improved up to the addition of 10 wt.% filler where the value of 92.1% was achieved with shape recovery of 95%.