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| Issue date:11/12/2009 |
| China Plastic & Rubber Journal (CPRJ) - Dec 2009 Issue |
| Source:China Plastic & Rubber Journal |
| Dennis Duan, Senior Editor |
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| New advancements in energy resource, building and construction material, medical technologies and high performance packaging have urged extrusion lines suppliers to develop tailor-made solutions. Reforms are made on the plasticizing, compounding and molding mechanism of the extrusion lines. The search of the new technologies is further expanding newer applications for extrusion. |
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New mechanism on melting and plasticizing
Conventionally, the plasticizing and transfer processes of melt in extrusion are performed jointly by electrical resistance heating and rotation of screw. However, the experts in the plastics processing industry have not given up the search of other possible alternatives.
For example the researchers from China's SCUT (South China University of Technology), a Guangdong-based university, are developing new technologies in extrusion and injection molding based on electromagnetic induction. During the SAMT forum held earlier this September in Changzhou, scientists from China’s CSU (Central South University, based in Hunan province) presented their research findings on the application of ultrasonic in the plasticization of polymer melt. Likewise, two exhibitors from CHINAPLAS 2009 displayed the “Super-shear plasticizing extruders” invented by Qu Jinping, a professor from SCUT.
The technique of ultrasonic plasticizing has been run and tested both home and abroad. According to Jiang Bingyan, a CSU professor, ultrasonic melt plasticizing can produce polymer melt with homogenous, micro-structure and crystallites of smaller size. The result is far more satisfactory than conventional plasticizing by heating.
At CHINAPLAS 2009, the two “Super-shear plasticizing extruders” invented by professor Qu were displayed in Hall 3.1 and Hall 13.1. The Hall 3.1 model – called SSPE-40, was blow molding LDPE film onsite. The extruder is very compact, with the distance from the feeding inlet to the die measuring only 25cm. For LDPE extrusion, maximum output for this extruder is 55kg/h and power consumption accounts only one third of the conventional screw extruders.
The extruder exhibited at Hall 13.1 was SSPE-80, which demonstrated the molding of PP hollow profile board with output up to 200kg/h. This plasticizing extruder employs conveying mechanism based on normal stress. In the extrusion process, the volume is less affected by die pressure and the extruded products are generally more robust. In addition, all the melt stay evenly in the extruders, which avoids deviations due to temperature.
Multi-screw extruders satisfying high performance compounding
Compounding and pelletizing technology based on extrusion processing is finding applications in almost every plastic processing sector. Therefore it is important for the extrusion industry to improve the compounding efficiency. In this way, Gneuss, a German supplier of extrusion equipment, has introduced the MRS extruder technology which is best suited for PET sheet production. Compared with conventional extruders, this innovative MRS system can directly process recycled PET bottle flakes into sheets without pre-crystallization and drying.
Chinese scientists also made their progress in multi screw extrusion. Jin Gang, a professor from SCUT, recalled that the university once developed a 12-screws extruder during the 9th Five-Year plan period (1996-2000). The extruder is mainly used in devolatilization.
On the SAMT forum, Xu Baiping, a professor from GITC (Guangdong Industry Technical College), presented a patented technology on extrusion. By inserting a small screw inside the single-screw channel, it has successfully integrated dispersion, melting, compounding and reinforced heat transfer into a new screw configuration.
New application concept for WPC
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"Simply housing", a detailed view of the innovative housing concept from Tech-Wood International Ltd. |
Recently, extrusion equipment supplier Cincinnati Extrusion has introduced a “simply housing” concept, which realises the unbelievable dream of building a house entirely using WPC (Wood-plastics composite). The “simply housing” concept introduced by UK based Tech-Wood Int. Ltd, is a modular system for quick, easy construction of complete houses from WPC. The first houses are currently under construction in Europe and the US. To produce the building components, Tech-Wood relies on well-established formulas with a natural fiber content of about 75%. With the use of long fibers, a high rigidity between 6,000 and 7,000 MPa is achieved, which is a distinctive feature in comparison to WPC materials from competitors. Profiles for load-bearing parts receive additional reinforcement with metal or fiberglass inserts to counteract plastic flow and increase their rigidity to a maximum of 10,000 -14,000 MPa.
KraussMaffei Berstorff covers the entire value-adding chain for processing WPC and other composite materials – from processing the separate components to compounding formulas, conditioning the materials, pelletizing and extrusion and finally supplying complete system solutions. Energy efficiency and product quality analyses indicate that corotating twin-screw extruders offered by the company are well suited to direct extrusion of WPC. KraussMaffei Berstorff’s modular, building-block systems for the housing and screw ensure that each extrusion line is perfectly adapted to the intended processing task. One salient advantage of this process lies in the fact that the natural fibers can be metered to the extruder without energy-intensive pre-drying.
New micro-molding system for extruding medical catheter
The market for medical catheters has huge growing potential. However in China, medical catheters rely mainly on import. In IPF 2008 (International Plastic Fair in Japan), audiences were impressed by the three-part micro-catheter molding technology presented by Japanese company PLA Giken. The three-part micro catheters produced feature different hardness and diameters for three sections and the maximum outer diameter has only 0.5mm. In addition, this system is easy to install and operate. Furthermore, the system design is very compact even it includes winder, a synchronous system comprising three extruders, three gear pumps and dies, cooling groove, traction unit, cutting unit and waste material picking device.
China is putting more effort on the research and development of micro size, high precision medical catheter. Complete production technology and equipment developed by the IPME (Institute of Plastic Machinery and Engineering) of BUCT (Beijing University of Chemical Technology) can manufacture various types of medical-purpose catheters such as single-cavity catheters, multi-cavity catheters and multi-layer composite catheters.
The production technologies were already in operation in Beijing, Zhejiang and Liaoning. This project leverages core technologies in precision extrusion from precision plasticizing technology, series pressure-stabilizing system, parallel pressure-stabilizing system, flow-stabilizing mold technology, online diameter-test technology, online thick-test technology to SPC technology and DSC-based multiple closed-loop control technology to meet special needs in high-precision medical catheter production.
Latest layer multiplier meeting packaging need
Though the technology of layer multiplication in film extrusion is not very common, it certainly has huge potential for development. As one of the leading suppliers for layer multiplier, EDI (Extrusion Die Industries) recently launched a brand-new layer multiplier for cast film production. This new-type layer multiplier can substantially improve the performance of micro-layer structure.
In addition, it is easy to deploy, compact in size and versatile compared with other layer multiplication systems (including older layer multiplication systems from EDI).
Layer multiplier technology is focused on top-end packaging market |
Jingcheng Mold Machinery, a leading Chinese supplier of extrusion flat die, is meeting future demand by developing a micro-layer co-extrusion die. Micro-layer co-extrusion die consists of micro-layer distributor, composite multiplier, packing distributor and manifold or rack-type die head where three or more extruders provide raw materials to accomplish 50~1000-layer micro-layer co-extrusion within the range of 0.01~0.1mm per layer. Compared with single-layer extrusion, this system substantially improves product flexibility and strength, and effectively avoids cracking during bi-oriented stretching. A film may break easily by stretching, but a micro-layer film with good viscosity, flexibility and tear resistance can withstand the overload and avoid cracking.
In addition to die head, the roll stand system can also accomplish film layer multiplication. The XP Express roll stand system from Davis-Standard has proven its application efficiency. In the area of barrier structures, the XP Express is effective at processing sheet with more than 100 layers using layer multipliers for micro layer composites.
New energy resource bringing new opportunities
The rapid development of solar energy, one of the latest alternative energy sources in the world, has promoted many business opportunities for the extrusion industry – a clear example is the production of encapsulation film. Breyer, a German machinery supplier, has launched a new EVA film extrusion line that ensures low shrinkage. For the module manufacturers it means that they can run their laminators more stable and as fast as possible by using low shrinkage film.
Xinle Huabao, a Chinese machinery supplier, has also provided cast film production lines to six customers both home and abroad, which are used in photovoltaic battery and automobile industry to produce EVA solar cell film of various thicknesses.
The development of Lithium-ion batteries is another fast growing sector. EDI’s years of work relating to lithium-ion batteries led to development of a die system that applies an anode or cathode slurry onto both sides of a foil substrate. The company has supplied two types of slot die coating systems for applying liquids or slurries in lithium-ion battery applications. Ultracoat dies, with adjustable lips, have been used for most anode and cathode coating, including two-sided applications. EDI’s Contour cast film dies are also used for lithium ion battery applications by companies that produce separator film.
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Copyright © Adsale Publishing Limited. Credit goes to Adsale Industry Portal when used.
We reserve the right to take legal action against any party who reprint any part of this article without acknowledgement. For enquiries, please contact the Editorial Department. |
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