Kerry Kirwan

A green chemistry-based classification model for the synthesis of silver nanoparticles

The assessment of the implementation of green chemistry principles in the syntheses of nanomaterials is a complex decision-making problem that necessitates the integration of several evaluation criteria. Multiple Criteria Decision Aiding (MCDA) provides support for such a challenge. One of its methods – Dominance-based Rough Set Approach (DRSA) – was used in this research to develop a model for the green chemistry-based classification of silver nanoparticle synthesis protocols into preference-ordered performance classes. DRSA allowed integration of knowledge from both peer-reviewed literature and experts (decision makers, DMs) in the field, resulting in a model composed of decision rules that are logical statements in the form: “if conditions, then decision”. The approach provides the basis for the design of rules for the greener synthesis of silver nanoparticles. Decision rules are supported by synthesis protocols that enforce the principles of green chemistry to various extents, resulting in robust recommendations for the development and assessment of silver nanoparticle synthesis that perform at one of five pre-determined levels. The DRSA-based approach is transparent and structured and can be easily updated. New perspectives and criteria could be added into the model if relevant data were available and domain-specific experts could collaborate through the MCDA procedure.

Synthetic mimicking of plant oils and comparison with naturally grown products in polyurethane synthesis

The use of plant oils as industrial feedstocks can often be hampered by their lack of optimization towards a particular process, as well as their development being risky; growing suitable volumes of crops to test can take up to five years. To circumvent this, we aimed to discover a method that would mimic plant oil profiles in the laboratory, and show that they exhibited similar properties to the naturally grown plant oils in a given process. Using the synthesis of polyurethanes as an example, we have synthesized six different polymers and demonstrated that plant oils will produce polymers with similar physical properties to those oils mimicked in the laboratory. The use of this mimicking process can be extended to other types of polymers to obtain a method for predicting the properties of a given material based on the plant oil composition of a crop before it is grown in bulk.

Workshop on life cycle sustainability assessment: the state of the art and research needs—November 26, 2012, Copenhagen, Denmark

The interest in life cycle sustainability assessment (LCSA) is currently booming in the LCA community, culminating lately in the forthcoming special issue from the International Journal of Life Cycle Assessment fully devoted to the topic. In the available literature, LCSA has mainly been conceptualised as a combination of LCA, social life cycle assessment (SLCA) and environmental life cycle costing (LCC). With the publication of guidelines for performing SLCA (Andrews et al. 2009), the code of practice for LCC (Swarr et al. 2011) and the existing standards for LCA, this could indicate that the question of how to perform an LCSA has been solved. However, the scientific publications give evidence of the need of further discussing the topic, both at conceptual and methodological level. The topic of LCSAwas at the core of a workshop organised on 26th November 2012 in the framework of the SETAC Europe 18th LCA Case Study Symposium in Copenhagen, with a dual aim: (1) to discuss the different schools of thoughts on LCSA and (2) to outline a research agenda framework for enabling/improving LCSA. The workshop was structured as four sessions (presentations) followed by a discussion part among participants which resulted in the identification of several research areas considered important for the successful future development of LCSA methodology and applications. The presentations provided insights on different approaches to LCSA both at conceptual and methodological level. A short summary of the main conclusions of the presentations and the main research topics proposed during the discussions is explained in the following sections.

Co-constructive development of a green chemistry-based model for the assessment of nanoparticles synthesis

Nanomaterials (materials at the nanoscale, 10-9m) are extensively used in several industry sectors due to the improved properties they empower commercial products with. There is a pressing need to produce these materials more sustainably. This paper proposes a MCDA approach to assess the implementation of green chemistry principles as applied to the protocols for nanoparticles synthesis. In the presence of multiple green and environmentally oriented criteria, decision aiding is performed with a synergy of ordinal regression methods; preference information in the form of desired assignment for a subset of reference protocols is accepted. The classification models, indirectly derived from such information, are composed of an additive value function and a vector of thresholds separating the pre-defined and ordered classes. The method delivers a single representative model that is used to assess the relative importance of the criteria, identify the possible gains with improvement of the protocols evaluations and classify the non-reference protocols. Such precise recommendation is validated against the outcomes of robustness analysis exploiting the sets of all classification models compatible with all maximal subsets of consistent assignment examples. The introduced approach is used with real-world data concerning silver nanoparticles. It is proven to effectively resolve inconsistency in the assignment examples, tolerate ordinal and cardinal measurement scales, differentiate between inter- and intra-criteria attractiveness and deliver easily interpretable scores and class assignments. This work thoroughly discusses the learning insights that MCDA provided during the co-constructive development of the classification model, distinguishing between problem structuring, preference elicitation, learning, modeling and problem-solving stages.

Inducing one-way toughness in laminated polycarbonate glazing

Abstract To aid escape in an emergency from a vehicle fitted with seemingly indestructible glazing, a laminate system has been developed that permits directional impact failure to be induced in polycarbonate glazing components. Test components exhibit near-full impact resistance when impacted from one side, but fail at much lower energy levels when impacted from the other. Thus, any glazing component made from this material system will exhibit excellent intruder resistance from the outside, whilst emergency escape becomes much easier from the inside. The system comprises a combination of polymer layers with the polycarbonate on the inside of the vehicle and a second polymer laminate on the outside. Additional features can be incorporated into the polymer laminate such as extra UV and chemical protection, i.e. areas where polycarbonate is less resilient than other materials. The mechanism of directional failure depends on the outside laminate containing a series of small flaws, generated during the manufacturing process, that close up when impacted from the outside. When impacted from the inside, the outer laminate is placed into tension and these flaws initiate cracks, which propagate rapidly backwards through the component inducing premature failure. The level of inside impact resistance can be varied by altering the processing conditions under which a component is made so that the interfacial strength between the polycarbonate and laminate is weakened.

Interfacial instabilities in multimaterial co-injection mouldings : Part 1 - Background and initial experiments

Abstract Interfacial adhesion between the skin and core is vital for successful co-injection moulding. This is the first paper in a series, which introduces and describes an in mould method of mixing that is applicable regardless of the compatibility of the materials. It works by inducing turbulent mixing at the interface between the skin and core materials. It makes use of the change that occurs from laminar to turbulent flow at high injection speeds in co-injection moulding. This novel approach takes advantage of the moulding parameters already available within the co-injection system to offer an expanded range of material combinations for multimaterial moulding. Comparisons are made between multimaterial mouldings made with miscible polymers, immiscible polymers with no compatibiliser, and immiscible polymers bonded by compatibilisers.

Interfacial instabilities in multimaterial co-injection mouldings: Part 2 - Interfacial mixing in transparent mouldings

Abstract Previous research in co-injection moulding has produced viscosity ratio guidelines for skin and core components, which must be followed if good core distribution is to be achieved. However, by examining two phase systems of PMMA-PC, which fall within the recommended viscosity range, this work shows that viscosity matching of materials is not a sufficient requirement for interfacial stability. The transparency of the materials allows areas of interfacial mixing to show up as streaks in the mouldings, so that factors affecting stability can be determined. One system is found to be more stable than the others. Explanations for such effects are given by consideration of interfacial mixing, viscosity, tooling geometry, injection speeds, interfacial stresses and shear in multilayered mouldings.

Robustness analysis of a green chemistry-based model for the classification of silver nanoparticles synthesis processes

This paper proposes a robustness analysis based on Multiple Criteria Decision Aiding (MCDA). The ensuing model was used to assess the implementation of green chemistry principles in the synthesis of silver nanoparticles. Its recommendations were also compared to an earlier developed model for the same purpose to investigate concordance between the models and potential decision support synergies. A three-phase procedure was adopted to achieve the research objectives. Firstly, an ordinal ranking of the evaluation criteria used to characterize the implementation of green chemistry principles was identified through relative ranking analysis. Secondly, a structured selection process for an MCDA classification method was conducted, which ensued in the identification of Stochastic Multi-Criteria Acceptability Analysis (SMAA). Lastly, the agreement of the classifications by the two MCDA models and the resulting synergistic role of decision recommendations were studied. This comparison showed that the results of the two models agree between 76% and 93% of the simulation set-ups and it confirmed that different MCDA models provide a more inclusive and transparent set of recommendations. This integrative research confirmed the beneficial complementary use of MCDA methods to aid responsible development of nanosynthesis, by accounting for multiple objectives and helping communication of complex information in a comprehensive and traceable format, suitable for stakeholders and/or decision-makers with diverse backgrounds.

Effect of Charge Density on the Taylor Cone in Electrospinning

A detailed understanding of charge density and its origins during the electrospinning process is desirable for developing new electrospinnable polymer-solvent systems and ensuring mathematical models of the process are accurate. In this work, two different approaches were taken to alter the charge density in order to measure its effect on the Taylor cone, mass deposition rate and initial jet diameter. It was found that an increase in charge density results in a decrease in the mass deposition rate and initial jet diameter. A theory is proposed for this behaviour in that an increase in charge density leads to the tip of the Taylor cone forming a smaller radius of curvature resulting in the concentration of electric stresses at the tip. This leads to the electrostatic forces drawing the initial jet from a smaller effective area or “virtual orifice”.

Effect of salts on the electrospinning of poly(vinyl alcohol)

Fibres with a diameter in the nanometer range were electrospun from aqueous poly(vinyl alcohol) (PVOH). In order to improve the mass deposition rate and decrease the final fibre diameter salts (NaCl, LiCl, LiBr and LiF) were added to the solution. The aim was to increase the charge density and hence increase the electrostatic forces on the fluid. It was found that with increasing salt concentration the charge density did increase. However the mass deposition rate was found to decrease and the final fibre diameter was found to increase. The decrease in mass deposition rate is explained by considering the concept of a virtual orifice. The increase in the final fibre diameter is explained by considering the charge distribution in the jet when it behaves like a conductor compared to when it behaves like an insulator. Both mechanisms result from the increase in conductivity of the PVOH solution without significantly modifying other solution properties when salt is added.