James L. Brighton

Modelling and Validation of Synthesis of Poly Lactic Acid Using an Alternative Energy Source through a Continuous Reactive Extrusion Process

PLA is one of the most promising bio-compostable and bio-degradable thermoplastic polymers made from renewable sources. PLA is generally produced by ring opening polymerization (ROP) of lactide using the metallic/bimetallic catalyst (Sn, Zn, and Al) or other organic catalysts in a suitable solvent. In this work, reactive extrusion experiments using stannous octoate Sn(Oct)2 and tri-phenyl phosphine (PPh)3 were considered to perform ROP of lactide. Ultrasound energy source was used for activating and/or boosting the polymerization as an alternative energy (AE) source. Ludovic® software, designed for simulation of the extrusion process, had to be modified in order to simulate the reactive extrusion of lactide and for the application of an AE source in an extruder. A mathematical model for the ROP of lactide reaction was developed to estimate the kinetics of the polymerization process. The isothermal curves generated through this model were then used by Ludovic software to simulate the “reactive” extrusion process of ROP of lactide. Results from the experiments and simulations were compared to validate the simulation methodology. It was observed that the application of an AE source boosts the polymerization of lactide monomers. However, it was also observed that the predicted residence time was shorter than the experimental one. There is potentially a case for reducing the residence time distribution (RTD) in Ludovic® due to the ‘liquid’ monomer flow in the extruder. Although this change in parameters resulted in validation of the simulation, it was concluded that further research is needed to validate this assumption.

A Technical and Economic Feasibility Study of Green Decortication of Hemp Fibre for Textile Uses

Abstract In 2003-4 BioRegional Development Group carried out a technical and economic feasibility study of a method of green decortication of hemp and degumming for the production of textile fibre. The study was published in December 2004. Two field trials of the green decortication technology took place in the UK and Australia, Cranfield University evaluated the process in both instances. Some of the fibre produced was subsequently processed in preparation for spinning. This paper contains the findings of these trials.

Nanomaterials Life Cycle Analysis : Health and Safety Practices , Standards and Regulations - Past , Present and Future Perspective

A new technology always raises new issues with its introduction on the market. Nanotechnology is not an exception. The advantages of nanomaterials use are not to demonstrate anymore and so, the commercializati on of consumer products based on nanotechnology doesn’t stop increasing. The introduction on the market of nanoproducts also involves some uncertainties. Risks regarding the environment and human health are not well known by the scientist, and the legislat ion doesn’t cover health and safety aspects related to nanomaterials. Especially, fate of nanoparticles during the life - cycle of nanoproducts is not fully experienced due the large variety of nanomaterials existing and their diverse applications. It is saf e to say that, given the explosive R&D and commercial uptake of nanomaterials unsurprisingly, the regulations governing the use and disposal of nanomaterials during its life cycle is behind the curve. The wide acceptance of nanotechnology by the consumers depends on

Techniques for estimating contact pressure resulting from loaded agricultural tyres

Recent increases in the weight of agricultural machines can cause soil management problems in the form of soil compaction. Tyre contact pressure is often used as an indicator of the potential for a machine to cause compaction.

Off-Road Dynamics Research at Cranfield University at Silsoe

This paper describes the laboratory and equipment designed and developed by the staff of Cranfield University at Silsoe to provide a centre to undertake research into the terramechanics of off road vehicles and single tyres and tracks; and the soil-machine dynamics of tillage and earthmoving equipment for civil and defence purposes. The laboratory comprises of a 45 m long, 5 m wide soil lane that has the facility to control soil moisture and water table levels together with single wheel test apparatus for both dynamic and quasi-static tyre performance studies, a “smart” winch to provide a dynamically controlled pull for “slip-pull” performance studies of whole vehicles, a tyre and track test device for compaction studies and a whole vehicle articulation rig. The facility has been designed to meet the needs of a range of applications including agriculture, automotive, construction, military, motor sport and telecommunications for the provision of previously unavailable tire, vehicle and machine performance data.

Microwave energy assisted synthesis of poly lactic acid via continuous reactive extrusion: modelling of reaction kinetics

The most commonly used batch process to manufacture PLA is ring opening polymerization (ROP) of lactide monomer in a suitable solvent, in the presence of a metallic/bimetallic catalyst (Sn, Zn, and Al) or other organic catalysts. However, this process does not lend itself to safer/cleaner and high throughput (and high volume) manufacturing. Continuous reactive extrusion of lactide monomer using a suitable reaction input has the potential to increase the throughput, and this route has been explored in the literature. In this work, reactive extrusion experiments using stannous octoate Sn(Oct)2 and tri-phenyl phosphine (PPh)3, were considered to perform ROP of lactide monomer using the microwave as an alternative energy (AE) source for activating and/or boosting the polymerization. Implementation of a microwave generator in a section of the extruder is one of the novelties of this research. A simulation model of ROP of PLA was formulated to estimate the impact of reaction kinetics and AE source on the polymerization process. Ludovic® software was used for the simulation of continuous reactive extrusion of the process. Experimental and simulated results were compared for the validation of the methodology. This work also highlights the advantages and drawbacks of most conventional metal catalysts, the effect of alternative energies on reaction mechanism, and safe and efficient production of PLA.

Development of CNC prototype for the characterization of the nanoparticle release during physical manipulation of nanocomposites

ABSTRACT This work focuses on the release of nanoparticles from commercially used nanocomposites during machining operations. A reliable and repeatable method was developed to assess the intentionally exposure to nanoparticles, in particular during drilling. This article presents the description and validation of results obtained from a new prototype used for the measurement and monitoring of nanoparticles in a controlled environment. This methodology was compared with the methodologies applied in other studies. Also, some preliminary experiments on drilling nanocomposites are included. Size, shape and chemical composition of the released nanoparticles were investigated in order to understand their hazard potential. No significant differences were found in the amount of nanoparticles released between samples with and without nanoadditives. Also, no chemical alteration was observed between the dust generated and the bulk material. Finally, further developments of the prototype are proposed.

Chronological review of the catalytic progress of polylactic acid formation through ring opening polymerization

The disposal of a large amount of polymer waste is one of the major challenges of this century. Use of bio-degradable polymers obtained from sustainable sources presents a solution to this problem. Poly lactic acid (PLA), a bio-degradable polymer, can be synthesized from sustainable sources as corn, starch, sugarcane and chips. Ring opening polymerization (ROP) of Lactide (LA) monomer using metal/bimetallic catalyst (Sn, Zn or Al) is the preferred method for synthesis of PLA. However, the PLA synthesized using such catalysts may contain trace elements of the catalyst. These catalyst traces are known carcinogens and as such should be (ideally) eliminated from the process. Use of the organic catalyst instead of metallic catalysts, may be one of the prominent solutions.

Morphological, optical and thermal characterisation of aerogel-epoxy composites for enhanced thermal insulation

The present work explores the possibility of introducing aerogel at different stages of the epoxy resin cure to identify the most effective method that ensures minimal destruction of the aerogel particles. The aerogel particles are added at 0.5 h, 1 h and 1.5 h after the resin and the hardener are mixed together. Additionally, the effect of a wetting agent that improves the interface between the aerogel and the resin is also investigated. The different materials are characterised using optical images and ESEM-EDX to determine the most effective processing route. Additional data are also provided by determining the different material’s optical transmittance and reflective characteristics. From the experimental results, it is observed that the addition of aerogel at the 1-h mark proves to be the most efficient route to follow. In addition, the wetting agent displays a negligible effect on the samples in the study; hence, its usage is advocated due to its influence on the interface strength. Therefore, the aerogel/epoxy/wetting agent sample with the aerogel added at the 1 h mark looks promising. A 13.3% decrease in thermal conductivity when compared with the pure resin/hardener sample along with the damage coefficient value of 0.183 demonstrates the material’s potential for thermal insulation applications.

The Design of a Mechanical System for the Harvest of Saffron Plants in Greece

Mechanisation contributes to increased crop production and timeliness of operation (Witney, 1988). Therefore there is always the need for the introduction of new harvest methods to increase harvest efficiency and consequently reduce the final cost of the product. Saffron is a crop traditionally harvested by hand and hence this paper explores the feasibility of mechanisation of the harvest procedure. A conceptual machine has been designed which operates by separating a) the tepals and b) the stigmas and stamens from the plant individually in the field using a combination of pneumatic and mechanical processes.