TPT November 2015

Article

Sikora AG

X-ray can also be used to detect agglomerations of additives in polyethylene pellets. The following example shows polyethylene with titanium oxide. X-ray was able to detect agglomerations of titanium oxide particles inside the plastic pellets (Picture 4). These agglomerations can lead to major problems when they are used in a further production process to manufacture final consumer products. The determination of the correct degree of foaming or expansion is also a possible analysis, which can be realised by X-raying the respective pellets (Picture 5). In contrast, an optical inspection of the pellets would have given the information that all the pellets are flawless. However, an incorrect degree of foaming or expansion of the pellets causes major defects in the end product, which can be prevented by using X-ray. In a further test, we used black pellets with different metallic contamination in order to prove the efficiency of X-ray technologies. In Picture 6, different black polyethylene pellets are visible. In these pellets, we clearly identified contamination of the size of 50µm or 100µm.

Picture 7: Metallic contamination in flakes

Picture 8: Contamination in coloured thick films

Picture 9: X-ray scanning and analysis equipment with conveyor belt for a continuous inspection flow (eg “at-line”)

Picture 10: X-ray scanning and analysis equipment for film and tape inspection

Picture 11: X-ray scanning and analysis equipment for discontinuous inspection and analysis – sample test (pellets, flakes, etc)

With the X-ray analysis it is also possible to detect contaminants in flakes. Picture 7 shows small and major metallic contaminants in flakes. An optical analysis would not be able to provide detailed results as the flakes are reflective and would disturb the analysis of an optical camera. With the X-ray analysis system it is possible to detect metallic contaminants and also classify their size. Due to this information it is possible to determine the quality degree of the flakes. The same principle can be used for coloured thick film inspection and analysis. As already mentioned, optical film inspection needs transparent thin films and therefore cannot be used for an inspection and analysis such as shown in Picture 8. Here the film has a dark colour and is several millimetres thick. An X-ray analysis system is able to detect the smallest contaminants in the film and therefore gives information on the contamination level of the overall material. Conclusions Quality standards in the plastic manufacturing industry are constantly increasing. Contamination, inhomogeneities or any other defects need to be detected and analysed. Today, even the smallest contamination needs to be detected during the production process. With X-ray technology, we are able to detect contamination of 50µm. Different inspection and analysis requirements need a modular concept approach for the equipment. Such equipment can be used either as a discontinuous lab scanner for pellets and flakes or as a continuous quality monitoring device of a production line. In this case the equipment is installed as an

“at-line” quality monitoring and analysis device and can be used for pellet and flake inspection as well. Pictures 9-11 illustrate the modular concept of an X-ray scanning and analysis device. The concept is applicable for different material types as for instance TPE, TPU, etc, or any coloured masterbatch or recycling product. The detection is independent of the colour of the pellet, or the colour and the thickness of the film or tape. Therefore, the quality can be constantly monitored and, hence, significantly improved. References 1. Mr Omar Monajjed, High Voltage Technical Manager, Liban Cables – Nexans, Lebanon, Effect of impurities on electric field distribution in HV XLPE insulation, Polymers in Cables 2014, Philadelphia, USA 2. J Kjellqvist, KP Pang, S Miao, Dow Europe GmbH, Horgen, Switzerland, Dow Chemical (China) Co Ltd, Shanghai, China, Performance Requirements to Assure Reliable HV and EHV Cables, China International Conference on Electricity Distribution (CICED 2010) Nanjing (20-23 Sept 2010) 3. Tomra demonstrates optical sorter, http://www.plasticsnews.com/ article/20131030/news/131039997/tomra-demonstrates-optical- sorter#, (10/2013) 4. Laura Tarrach, OCS GmbH, Pellet Scanning in “Free Fall”, Kunststoffe international (12/2010) 5. Satake, Pellet Sorter PCS600PFD, http://www.satake-usa.com/ images/Pellet_Sorter_Brochure.pdf (2014) 6. Robert Fosbinder, Denise Orth, Lippincott Williams & Wilkins, Essentials of Radiologic Science (01.02.2011)

Sikora AG – Germany Fax: +49 421 48900 90 Email: sales@sikora.net Website: www.sikora.net

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N ovember 2015