Modified Sepiolite Nanoclays in Advanced Composites for Engineering Applications.

Clay-polymer nanocomposites (CPNs) containing a small weight fraction of nanoclay are known to display enhanced mechanical and thermal properties compared to neat polymers. However, the preparation and application of such nanocomposites remain challenging owing to the difficulties in dispersing nanoclays in polymer matrices. This study focuses on two surfactant-modified organophilic sepiolite clays to demonstrate the simplicity of the modification process, as well as on the use of a benzoxazine monomer (i.

Taking a Tailored Approach to Material Design: A Mechanistic Study of the Selective Localization of Phase-Separated Graphene Microdomains.

To achieve multifunctional properties using nanocomposites, selectively locating nanofillers in specific areas by tailoring a mixture of two immiscible polymers has been widely investigated. Forming a phase-separated structure from entirely miscible molecules is rarely reported, and the related mechanisms to govern the formation of assemblies from molecules have not been fully resolved. In this work, a novel method and the underlying mechanism to fabricate self-assembling, bicontinuous, biphasic structures with localized domains made up of amine-functionalized graphene nanoplatelets are presented, involving the tailoring of compositions in a liquid processable multicomponent epoxy blend.

Properties and Curing Kinetics of a Processable Binary Benzoxazine Blend.

A benzoxazine system is presented combining liquid cardanol-based benzoxazine (CA-a) and an effective initiator (3,3'-thiodipropionic acid, TDA) to bisphenol A-based benzoxazine (BA-a). The resultant mixture of monomeric precursors shows excellent fluidity and a relatively low peak polymerization temperature of around 200 °C. Moreover, the cured polybenzoxazine displays a high thermal decomposition temperature ( > 330 °C), a moderately high glass transition temperature (∼148 °C), and robust mechanical strength (storage modulus ∼ 2.

Examining the Quasi-Static Uniaxial Compressive Behaviour of Commercial High-Performance Epoxy Matrices.

Four commercial high-performance aerospace aromatic epoxy matrices, CYCOM890, CYCOM977-2, PR520, and PRISM EP2400, were cured to a standardised 2 h, 180 °C cure cycle and evaluated in quasi-static uniaxial compression, as well as by dynamic scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The thermoplastic toughened CYCOM977-2 formulation displayed an overall increase in true axial stress values across the entire stress-strain curve relative to the baseline CYCOM890 sample. The particle-toughened PR520 sample exhibited an overall decrease in true axial stress values past the yield point of the material.

Steering Potential for Printing Highly Aligned Discontinuous Fibre Composite Filament.

DcAFF (discontinuous aligned fibre filament) is a novel material for fused filament fabrication (FFF) 3D printing made of highly aligned discontinuous fibres produced using high performance discontinuous fibre (HiPerDiF) technology. It reinforces a thermoplastic matrix to provide high mechanical performance and formability. Accurate printing of DcAFF poses a challenge, especially for complex geometries, because: (i) there is a discrepancy between the path where the filament experiences the adhering pressure from the filleted nozzle and the nozzle path; and (ii) the rasters display poor adhesion to the build platform immediately after deposition, which causes the filament to be dragged when the printing direction changes.

Open Hole Tension of 3D Printed Aligned Discontinuous Composites.

This paper explores the use of Discontinuous Aligned Fibre Filament (DcAFF), a novel discontinuous fibre reinforced thermoplastic filament for 3D printing, to produce structural complex parts. Compared to conventional composite manufacturing, 3D printing has great potential in steering fibres around small structural features. In this current study, the initial thin carbon fibre (CF)-poly(L-lactic acid) (PLA) tape, produced with the High Performance Discontinuous Fibre (HiPerDiF) technology, is now reshaped into a circular cross-section filament, the DcAFF, using a bespoke machine designed to be scalable to high production rates rather than using a labour-intensive manual moulding method as in previous work.

Analysis of the Chemical Distribution of Self-Assembled Microdomains with the Selective Localization of Amine-Functionalized Graphene Nanoplatelets by Optical Photothermal Infrared Microspectroscopy.

By incorporating 1-(2-aminoethyl)piperazine (AEPIP) into a commercial epoxy blend, a bicontinuous microstructure is produced with the selective localization of amine-functionalized graphene nanoplatelets (A-GNPs). This cured blend underwent self-assembly, and the morphology and topology were observed spectral imaging techniques. As the selective localization of nanofillers in thermoset blends is rarely achieved, and the mechanism remains largely unknown, the optical photothermal infrared (O-PTIR) spectroscopy technique was employed to identify the compositions of microdomains.

Natural Fibres as a Sustainable Reinforcement Constituent in Aligned Discontinuous Polymer Composites Produced by the HiPerDiF Method.

Sustainable fibre reinforced polymer composites have drawn significant attention in many industrial sectors as a means for overcoming issues with end-of-life regulations and other environmental concerns. Plant based natural fibres are considered to be the most suitable reinforcement for sustainable composites since they are typically from renewable resources, are cheap, and are biodegradable. In this study, a number of plant based natural fibres-curaua, flax, and jute fibres-are used to reinforce epoxy, poly(lactic acid) (PLA), and polypropylene (PP) matrices to form aligned discontinuous natural fibre reinforced composites (ADNFRC).

Characterisation of Natural Fibres for Sustainable Discontinuous Fibre Composite Materials.

Growing environmental concerns and stringent waste-flow regulations make the development of sustainable composites a current industrial necessity. Natural fibre reinforcements are derived from renewable resources and are both cheap and biodegradable. When they are produced using eco-friendly, low hazard processes, then they can be considered as a sustainable source of fibrous reinforcement.

A Novel Approach to Atomistic Molecular Dynamics Simulation of Phenolic Resins Using Symthons.

Materials science is beginning to adopt computational simulation to eliminate laboratory trial and error campaigns-much like the pharmaceutical industry of 40 years ago. To further computational materials discovery, new methodology must be developed that enables rapid and accurate testing on accessible computational hardware. To this end, the authors utilise a novel methodology concept of intermediate molecules as a starting point, for which they propose the term 'symthon'[a] rather than conventional monomers.

Improving Dispersion of Recycled Discontinuous Carbon Fibres to Increase Fibre Throughput in the HiPerDiF Process.

In order to increase the material throughput of aligned discontinuous fibre composites using technologies such as HiPerDiF, stability of the carbon fibres in an aqueous solution needs to be achieved. Subsequently, a range of surfactants, typically employed to disperse carbon-based materials, have been assessed to determine the most appropriate for use in this regard. The optimum stability of the discontinuous fibres was observed when using the anionic surfactant, sodium dodecylbenzene sulphonate, which was superior to a range of other non-ionic and anionic surfactants, and single-fibre fragmentation demonstrated that the employment of sodium dodecylbenzene sulphonate did not affect the interfacial adhesion between fibres.

Development of Cycloaliphatic Epoxy-POSS Nanocomposite Matrices with Lambas Enhanced Resistance to Atomic Oxygen.

The preparation of ultra-thin CFRP laminates, which incorporate a cycloaliphatic epoxy resin reinforced with polyhedral oligomeric silsesquioxane (POSS) reagent nanofiller, using out-of-autoclave procedure is reported. The influence of the amount of POSS within the laminate on the mechanical properties and surface roughness of the laminates is analysed before and after exposure to atomic oxygen (AO) to simulate the effects of low Earth orbit (LEO). The addition of 5 wt% POSS to the base epoxy leads to an increase in both flexural strength and modulus, but these values begin to fall as the POSS content rises, possibly due to issues with agglomeration.

Examining the Influence of Anion Nucleophilicity on the Polymerisation Initiation Mechanism of Phenyl Glycidyl Ether.

The reaction of phenyl glycidyl ether (PGE) with 1-ethyl-3-methylimidazolium acetateand 1-ethyl-3-methylimidazolium thiocyanate to initiate the polyetherification reaction wasexamined using thermal and spectral analysis techniques. The influence of the nucleophilicity of theanions on the deprotonation of the 1-ethyl-3-methylimidazolium cation determined the reactionpathway. The thermal degradation of the ionic liquid liberated the acetate ion and led, subsequently,to the deprotonation of the acidic proton in the imidazole ring.

Exploring Structure⁻Property Relationships in Aromatic Polybenzoxazines Through Molecular Simulation.

A series of commercial difunctional benzoxazine monomers are characterized using thermal and thermo-mechanical techniques before constructing representative polymer networks using molecular simulation techniques. Good agreement is obtained between replicate analyses and for the kinetic parameters obtained from differential scanning calorimetry data (and determined using the methods of Kissinger and Ozawa). Activation energies range from 85 to 108 kJ/mol (Kissinger) and 89 to 110 kJ/mol (Ozawa) for the uncatalyzed thermal polymerization reactions, which achieve conversions of between 85% and 97%.

'Phoenix polymers': fire induced nanohardness in fibril-forming aromatic cyanate esters.

For the first time we present nanoindentation analysis of charred, cured aromatic cyanate esters, which exhibit outstanding mechanical properties when analysed under applied loads of 0.1-300 mN. Following charring (900 °C for 10 minutes to achieve graphitised structures), the samples display a remarkable combination of a modulus of elasticity of around 25 GPa and nanohardness of 300 kgf mm, making them some 30-40% stiffer than bone and practically as hard as tooth enamel.

Water-based fractionation of a commercial humic acid. Solid-state and colloidal characterization of the solubility fractions.

Background And Hypothesis: Humic acid (HA) is of considerable environmental significance, being a major component of soil, as well as being considered for application in other technological areas. However, its structure and colloidal properties continue to be the subject of debate, largely owing to its molecular complexity and association with other humic substances and mineral matter. As a class, HA is considered to comprise supramolecular assemblies of heterogeneous species, and herein we consider a simple route for the separation of some HA sub-fractions.

Multi-Functional Carbon Fibre Composites using Carbon Nanotubes as an Alternative to Polymer Sizing.

Carbon fibre reinforced polymers (CFRP) were introduced to the aerospace, automobile and civil engineering industries for their high strength and low weight. A key feature of CFRP is the polymer sizing - a coating applied to the surface of the carbon fibres to assist handling, improve the interfacial adhesion between fibre and polymer matrix and allow this matrix to wet-out the carbon fibres. In this paper, we introduce an alternative material to the polymer sizing, namely carbon nanotubes (CNTs) on the carbon fibres, which in addition imparts electrical and thermal functionality.

Blocked Shape Memory Effect in Negative Poisson's Ratio Polymer Metamaterials.

We describe a new class of negative Poisson's ratio (NPR) open cell PU-PE foams produced by blocking the shape memory effect in the polymer. Contrary to classical NPR open cell thermoset and thermoplastic foams that return to their auxetic phase after reheating (and therefore limit their use in technological applications), this new class of cellular solids has a permanent negative Poisson's ratio behavior, generated through multiple shape memory (mSM) treatments that lead to a fixity of the topology of the cell foam. The mSM-NPR foams have Poisson's ratio values similar to the auxetic foams prior their return to the conventional phase, but compressive stress-strain curves similar to the ones of conventional foams.

Developing (Quantitative Structure Property Relationships) QSPR Techniques to Predict the Char Formation of Polybenzoxazines.

This study uses the Molecular Operating Environment software (MOE) to generate models to calculate the char yield of polybenzoxazines (PBz). A series of benzoxazine (Bz) monomers were constructed to which a variety of parameters relating to the structure (e.g.

Examining the Initiation of the Polymerization Mechanism and Network Development in Aromatic Polybenzoxazines.

Three bis-benzoxazine monomers based on the aniline derivatives of bisphenol A (BA-a), bisphenol F (BF-a), and 3,3'-thiodiphenol (BT-a) are examined using a variety of spectroscopic, chromatographic, and thermomechanical techniques. The effect on the polymerization of the monomers is compared using two common compounds, 3,3'-thiodiphenol (TDP) and 3,3'-thiodipropionic acid (TDA), at a variety of loadings. It is found that the diacid has a greater effect on reducing the onset of polymerization and increasing cross-link density and for a given benzoxazine.

Prediction of selected physical and mechanical properties of a telechelic polybenzoxazine by molecular simulation.

Molecular simulation is becoming an important tool for both understanding polymeric structures and predicting their physical and mechanical properties. In this study, temperature ramped molecular dynamics simulations are used to predict two physical properties (i.e.

A systematic examination of colour development in synthetic ultramarine according to historical methods.

A number of historical texts are investigated to ascertain the optimum conditions for the preparation of synthetic ultramarine, using preparative methods that would have been available to alchemists and colour chemists of the nineteenth century. The effect of varying the proportion of sulphur in the starting material on the colour of the final product is investigated. The optimum preparation involves heating a homogenised, pelletised mixture of kaolin (100 parts), sodium carbonate (100 parts), bitumen emulsion (or any 'sticky' carbon source) (12 parts) and sulphur (60 parts) at 750°C for ca.

Using combined computational techniques to predict the glass transition temperatures of aromatic polybenzoxazines.

The Molecular Operating Environment software (MOE) is used to construct a series of benzoxazine monomers for which a variety of parameters relating to the structures (e.g. water accessible surface area, negative van der Waals surface area, hydrophobic volume and the sum of atomic polarizabilities, etc.