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Conference paperDeng X, Kinloch AJ, Pimenta S, et al., 2017,
Homogeneous and toughened cellulose epoxy composites, 21st International Conference on Composite Materials
© 2017 International Committee on Composite Materials. All rights reserved. Homogeneous and toughened cellulose-epoxy polymers were made by modifying an anhydride-cured epoxy with two green modifiers, microcrystalline cellulose (MCC) and cellulose nanocrystals (CNC). Without silane treatment, the MCC and CNC particles sedimented in the epoxy resin and formed either a gradient polymer or two distinct layers. This problem was resolved by the addition of (3-glycidyloxypropyl)trimethoxysilane (GPTMS) during the three-roll mill process, which was able to act as a coupling agent between the MCC or CNC and the epoxy, to give a modified epoxy containing homogenously dispersed cellulose particles. The addition of MCC or CNC decreased the glass transition temperature of the epoxy, but doubled the fracture energy. By comparison, the addition of 10 wt% of nanosilica only gave a 57% increase in fracture energy. The toughening mechanisms of the MCC-epoxy and CNC-epoxy were identified to be crack deflection, pull-out and debonding of the cellulose particles, which was followed by plastic void growth. The modified Halpin-Tsai model was used to predict the increase in modulus and showed good agreement with the experimental modulus values. Analytical modelling of the fracture energies showed that particle debonding and particle pull-out contributed to the increased toughness, but the main toughening contributions were due to plastic void growth for CNC-epoxy and both plastic void growth and crack deflection for MCC-epoxy. In addition, plain-weave long glass fibre (GF) composite was manufactured with MCC using resin infusion under flexible tooling (RIFT). The interlaminar fracture energy of the composite was measured and it was found that the increase in toughness in the epoxy polymer was not translated to the composite. This was thought to be due to the silane that was used to treat the MCC-epoxy system migrating to the glass fibre surface and improved the fibre-matrix adhesion.
Journal articleRomain C, Garden JA, Trott G, et al., 2017,
Di-Zinc-Aryl Complexes: CO2 Insertions and Applications in Polymerisation Catalysis, CHEMISTRY-A EUROPEAN JOURNAL, Vol: 23, Pages: 7367-7376, ISSN: 0947-6539
Conference paperLowe C, Taylor A, 2017,
A Comparison of How Well Two Different Models of Thermo-Setting Polymers Predict Their Thermo-Mechanical Aspects, 23rd Polymer-Networks-Group Conference, Publisher: WILEY-V C H VERLAG GMBH, Pages: 51-68, ISSN: 1022-1360
Conference paperKinloch AJ, Guild FJ, Masania K, et al., 2017,
The fracture of thermosetting polymers containing silica nanoparticles, Pages: 71-72
The present paper concentrates on the effect of adding silica nanoparticles to epoxy polymers, which are the basis of modern structural adhesives. The formation of 'hybrid' epoxy polymers, containing both silica nanoparticles and carboxyl-terminated butadiene-acrylonitrile (CTBN) rubber microparticles, is also discussed. The structure/property relationships are considered, with an emphasis on the toughness and the toughening mechanisms.
Journal articlezhu Y, romain C, Williams CK, 2016,
Sustainable polymers from renewable resources, Nature, Vol: 540, Pages: 354-362, ISSN: 0028-0836
Renewable resources are used increasingly in the production of polymers. In particular, monomers such as carbon dioxide, terpenes, vegetable oils and carbohydrates can be used as feedstocks for the manufacture of a variety of sustainable materials and products, including elastomers, plastics, hydrogels, flexible electronics, resins, engineering polymers and composites. Efficient catalysis is required to produce monomers, to facilitate selective polymerizations and to enable recycling or upcycling of waste materials. There are opportunities to use such sustainable polymers in both high-value areas and in basic applications such as packaging. Life-cycle assessment can be used to quantify the environmental benefits of sustainable polymers.
Journal articleDagorne S, Romain C, 2016,
PolymerizationCatalysis by Metal Phenolates, Pages: 1-44
Journal articleKamaludin MA, Patel Y, Blackman BRK, et al., 2016,
Fracture mechanics testing for environmental stress cracking in thermoplastics, Procedia Structural Integrity, Vol: 2, Pages: 227-234, ISSN: 2452-3216
Under the combined influence of an aggressive environment and applied stress, engineering thermoplastics may undergo a phenomenon known as environmental stress cracking (ESC). This can result in adverse effects such as embrittlement and premature failure in service, due to the growth of environmentally-induced cracks to critical sizes, with little to no fluid absorption in the bulk material. Fracture mechanics is proposed as a suitable scheme to study and quantify ESC, with the aim being to obtain characterising data for different polymer-fluid combinations of interest, as well as to develop a reliable fracture mechanics test protocol. In the proposed method, slow crack growth is monitored to assess the effect of a range of applied crack driving forces (K, or alternatively G) on observed crack speeds, as opposed to simply measuring time-to-failure. This paper presents the results of experiments performed on the following materials: linear low density polyethylene (LLDPE) in Igepal solution and high impact polystyrene (HIPS) in sunflower oil. A discussion of the various issues surrounding the data analysis for these long-term tests is also included, as the attainment of consistent and repeatable results is critical for a method to be internationally standardised, which is a goal of the European Structural Integrity Society (ESIS) Technical Committee 4 from whose interest this work is drawn.
Conference paperKinloch AJ, mohammed IK, Charalambides MN, 2016,
Modelling the Peeling Behavior of Soft Adhesives, 21st European Conference on Fracture, ECF21, 20-24 June 2016, Catania, Italy, Publisher: Elsevier, Pages: 326-333
Peel tests were performed on pharmaceutical drug patches which consisted of a polyester backing membrane supporting an acrylic pressure-sensitive adhesive (PSA) (without and with an anti-fungal drug present) adhered to a polyethylene substrate. Interfacial separation of the PSA from the polyethylene substrate was observed in most cases. Finite element (FE) peeling simulations were conducted which characterized the backing-membrane as an elasto-plastic power-law material, the PSA as a viscoelastic material and the interfacial properties with a cohesive zone model (CZM). The mechanical response of the backing membrane and the PSA were measured from tensile experiments while the rate-dependent cohesive zone parameters, i.e. the fracture energy and maximum stress, were measured directly from poker-chip probe tack tests. The numerical results from the CZM/FE simulations and the experimental values of the peel forces as a function of the peel angle, peel speed and PSA thickness were found to be in good agreement. Two different anti-fungal drugs were added to the PSA and the influence of the drug was investigated using contact angle measurements, tensile tests, dynamic mechanical analysis and peel tests.
Journal articleBlackman BRK, Hoult T, Patel Y, et al., 2015,
Steady-state scratch testing of polymers, Polymer Testing, Vol: 49, Pages: 38-45, ISSN: 0142-9418
The paper extends the notion of steady-state cutting of polymers with a sharp tool to scratching. The analysis assumes there is separation at the tool tip (fracture) and the removed layer undergoes plastic shear. Results are presented for three polymers: PMMA, PC and PBT. For the tougher polymer, PC, smooth scratches were obtained and the modified cutting analysis works well provided that the wear on the initially sharp tip is accounted for. For the more brittle polymers, PMMA and PBT, rougher scratches were obtained and this is consistent with the notion that the polymers exhibited micro-cracking ahead of the tool tip, which led to rough surfaces being generated. The results demonstrate that the fracture toughness and the yield stress are controlling parameters in the scratching process and that a sufficiently high value of crack opening displacement COD (greater than about 10 μm) ensures that smooth scratches are obtained, as was the case for PC.
Conference paperZhu Y, Williams CK, 2015,
Chemoselective Polymerization: From Multi-Component Feedstocks to Sequence Controlled Block Copolyesters, 250th National Meeting of the American-Chemical-Society (ACS), ISSN: 0065-7727
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