Thermal Management in Polymer Processing

Lead Research Organisation: University of Bradford
Department Name: School of Engineering and Informatics


The U.K is one of the top 5 plastics processing countries in Europe with a turnover of 19 billion accounting for 2.1% of GDP (equivalent to the metals industry). The industry is made up of 7,400 companies falling mainly into the SME category.The sector is growing year on year as more traditional materials are being replaced by plastics, for example, in the construction industry a 6 million tonnes usage in 2004 is projected to grow to 8 million tonnes in 2010 while in the automotive industry the typical car now contains 10% plastic by weight. For a typical UK plastics company the electricity bill is usually between 1 and 3% of turnover, which amounts to 380 million per annum for the UK (this is only electricity costs - 80% of polymer processors in the UK use both electricity and gas). A reduction in electricity usage of 10% would result in savings of 38 million per annum and a significant reduction in environmental burden. There are many areas in a typical polymer processing plant where energy use could be reduced. A prime example is in the extrusion area where machines running at non-optimised conditions and without proper control systems in place can account for 15-20% of overall process energy losses. The cooling of polymer parts is also a prime area for consideration with chiller systems running at non-optimised temperatures and flow rates. It is evident from the figures for the polymer industry that there is a need to improve energy efficiency within the industry but for any energy management system to be effective measures must be taken to optimise the whole plant and not just isolated pieces of equipment. For this reason, this proposal will apply a whole systems approach to attaining energy efficiency within the polymer processing industry by developing a software based, Energy Management Tool (EMT). This approach will be complemented by the development of process monitoring and control technologies to optimise energy use in extrusion.


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Description The aim of this project was to investigate and improve the efficiency of single screw extrusion, one of the most important processes used to manufacture plastic products. Highly instrumented extruders were used, allowing the energy consumption and melt quality of polymer to be measured in real-time at a range of different conditions. Key indicators of melt quality included mass throughput and melt temperature and pressure stability. The effect of polymer type, set temperature, extruder screw screw geometry and extruder scale were examined.

Results showed that process efficiency and melt quality depended in a complex way on many different variables. However, a number of key findings included:
1. Extruder screw rotation speed was the single most important variable; using low screw rotation speeds used the most energy per kg of polymer, but produced the most stable output. High screw rotation speeds caused the process to consume least specific energy but conversely produced the highest levels of variation in output.
2. Extruder screw geometry had a significant influence on process efficiency and quality. For many polymers, use of barrier flighted extruder screws provided better performance because of the better melting capability.
3. Melt viscosity (resistance to flow) had a measurable effect on both process efficiency and stability. Higher viscosity polymer melts required more energy per kg to process and were less stable.
4. The scale of extruder had a strong effect on process efficiency. Smaller extruders were comparably less efficient than larger counterparts, although lower levels of variation were produced.
5. Novel dynamic models were produced to try to predict aspects of the extrusion process, such as throughput, energy consumption and melt quality. Experimental data were used to train these models, which were found to predict process conditions well.

Overall, the findings of this research, combined with the sister grant EP/G059489/1, hosted at Queens University, Belfast, have led to an improved understanding of the thermal efficiency of polymer extrusion. These findings and the tools developed will be useful for polymer processors wishing to better understand and optimise industrial processes.
Exploitation Route The findings of this research has direct industrial applications. In addition to the project partners, a number of industrial representatives have had exposure to the research through conferences and workshops. A number of journal papers have been published to disseminate the findings of this research to the wider industrial and academic communities. Conference papers were presented in the UK (SUSTEM and Polymer Process Engineering conferences) and internationally (Society of Plastics Engineers, USA; Polymer Processing Society Annual Meeting, Germany)
Sectors Energy,Manufacturing, including Industrial Biotechology,Other

Description The findings of the research project have been used to inform the UK and international polymer processing industry of important considerations related to the efficiency of polymer extrusion. In particular, the research has highlighted the importance of carefully choosing the type of extruder screw, set temperature and screw rotation speed used for each polymer and product type.
First Year Of Impact 2013
Sector Manufacturing, including Industrial Biotechology,Other
Impact Types Economic

Description Belfast 
Organisation Queen's University Belfast
Country United Kingdom 
Sector Academic/University 
PI Contribution The grant was run in parallel with an associated EPSRC grant at QUB (EP/G059489/1). Complementary and directly linked research was performed at both sites. The focus at Bradford was on understanding the thermal efficiency of the extrusion process, whereas the focus at QUB was to build on this understanding, complement it with data measured in an industrial setting and to develop a tool which industry could use.
Collaborator Contribution One PDRA at Queens focused on the development of a low cost monitoring system to measure and control the extrusion process; the other worked closely with a collaborating company to develop a software tool.
Impact 9 co-authored journal papers (as listed in publications); one follow-on grant at QUB (2013-2015, Proof of Concept (PoC) project, "Integrating energy efficiency monitoring, control and optimization for plastics industry". Invest Northern Ireland and European Regional Development Fund).
Start Year 2010
Description Joint International Laboratory for Polymer Micro Processing 
Organisation Sichuan University
Country China 
Sector Academic/University 
PI Contribution Establishment of a micro moulding facility in Sichuan, to mirror the (more extensive) facilities in Bradford, to develop further our collaborative research. Joint IP for conducting polymer products.
Collaborator Contribution Materials engineering expertise, including polymer nano composite products, especially for electrically conducting products. Joint IP for conducting polymer products.
Impact Joint publications. Joint IP
Start Year 2010
Description Polymer engineering/processing conferences in USA (Orlando) and Germany (Nuremberg) 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact The project findinds were disseminated widely through the relevant fields of industrial and academic research and development.
Year(s) Of Engagement Activity 2012,2013,2014