Organic Polymers Facilities and Techniques

Volatile additives including; antimicrobial agents, perfumes, flavourings and polymer stabilisers are often very difficult to retain in a polymer matrix during melt processing and throughout the service lifetime of the product. Loss of the additive can lead to premature failure or loss of function. We have extensive experience in encapsulation of such additives within porous particles which can lead to controlled release of the additive. Our success in this area stems from an ability to explore the interaction between the additive molecule and the surface of the porous particle. The encapsulation of antimicrobials in particular, maps very nicely onto the dental technology/health care research areas in the institute.

Reliance on anti-microbial chemicals is sometimes impractical in terms of maintenance issues and is also bad for the environment. A polymer coating containing nano-particles that lead to production of microbe destroying free radicals, when irradiated with ultraviolet radiation, is highly desirable and is currently being investigated at the centre and is another example of collaboration between the materials and microbiology arm of the institute. Similar nano-particles are also able to break down nitrogen oxides therefore incorporation of such particles into a paint for road-side structures/furniture could potentially reduce NOx emission, studies are also ongoing in this area and combine well with the environment related activities of the institute.

A common theme running through all the above areas is interfacial interactions between particles and adsorbate molecules whether they are polymer chains, biocides, coupling agents or polymer stabilisers. We therefore have excellent facilities for examining these interactions. Flow micro-calorimetry (FMC) is one of the principal techniques used and is able to measure the energy of adsorption together with the amount of material adsorbed from solution. FMC can also be used to study competitive adsorption. Very often diffuse reflectance Fourier transform infrared spectroscopy is used to support the FMC data and can provide information relating to which functional groups of the adsorbate are involved in the adsorption and therefore the orientation of the adsorbed molecule.

Facilities are also available to compound modified fillers into polymers in a small 50 g scale using a Haake Rheocord or at up to 30 kg/hour using a Thermo-Prism 24HC modular 28:1 L:D twin screw extruder.

Fillers can be incorporated into elastomers using the two roll mill. The resulting composites can be compression or injection moulded. The mechanical properties of the composites can then be investigated using dynamic mechanical thermal analysis and tensile testing.

Having the ability to characterise adsorption interactions occurring during the surface modification of fillers and conduct follow-on polymer melt compounding and moulding operations and characterisation of properties is an important strength in this group.

Most polymer and coatings materials undergo degradation and oxidation processes during their particular application resulting in marked property changes, which restrict their useful lifetime. Spectroscopic and physical-mechanical property changes are used to evaluate such effects and to determine useful practical lifetimes of polymer materials. Polymers in industry, engineering and conservation have specific requirements and needs. Discolouration is a major problem and can be important in recycling operations such as with polyester bottles and film or during the weathering of materials. These polymer materials also require some form of stabilisation for effective long-term usage where both heat and light are active environmental parameters. Different polymers require different methodologies for effective stabilisation and may often involve the use of synergistic formulations and their controlled release. Expertise is available for the development and study of the stabilisation of most polymeric materials against hydrolysis, biodegradation, thermal-oxidation, processing and weathering. The Centre has new QUV and Q-Panel Suntest Xenon arc weatherometers with humidity/temperature control.

Radiation curing science for general coatings and photoimaging processes are growing areas of industrial concern with the type, performance and properties of coatings being a major directive with particular emphasis on stability. Positive and negative photoresists for photoimaging play a key role in photographic, printing and electronic industries. Spectral photosensitivity and aqueous solubility continue to be major areas of technical development.

Polymer materials such as acrylics, polyesters and alkyds have widespread applications in paints and in powder coatings. Modified systems are being developed for enhanced stability in various environmental applications. Light stabilisation is of major concern as is anti-fungal activity. Enhanced coatings are being developed for both the control of light stability and biocide release mechanisms. Silica and titania filled systems play a major role in this regard.

The centre has wide expertise on the properties and surface characteristics of pigments such as carbon black, silica and titanium dioxide. Nano-particles are an important development particularly with regard to enhancement of polymer properties and the development of photocatalytic surfaces in polymers and paints for environmental and self-cleaning applications.

Synthetic receptors based on macrocyclic structures and molecular imprinting techniques are currently being investigated for use as sensors in environmental and medical applications.Work on sensors has primarily concentrated on the use of electrochemical, potentiometric and piezo-electric methods of analysis.

The synthesis of conducting and semiconducting polymers is the subject of current interest with work being undertaken into the synthesis of conducting polymers.

This includes pyrrole derivatives for use in the synthesis of artificial receptors for sensors and fluorescent phenylene ethynylene polymers for the development of electroluminescent displays, based on palladium cross-coupling reactions.

The main area of research carried out by the food technology group in the Centre (based in the Hollings Faculty) is the development of fermented and non‑fermented foods based on cereal and plant products to meet consumer/market needs. The chemical, physical and nutritional changes occurring during the manufacture of these products are being investigated, with the functionality of the components, so that product development and modification can be based on sound theoretical knowledge. Batch operations and continuous manufacturing process, particularly extrusion cooking, are being evaluated for the manufacture of these products. Supporting research is on food consumption patterns and nutritional status of different population groups. The results of this study will inform development work and lead to the identification of specific risk factors, which are associated with different population groups. The findings of this work are being applied to the product development work in order that highly nutritious and organoleptically acceptable foods are available to these population groups.

The Centre also has significant experience in the area of recycling of materials with a number of government incentives in operation such as fridges involving their component separations and monitoring and evaluation for product quality and environmental control.