| 词条 | Guardian (polymer) | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| 释义 |
Guardian is the trademark name of a polymer originally manufactured by Securency International,{{sfn|de Heij|2002|p=6}} a joint venture between the Reserve Bank of Australia and Innovia Films Ltd. The latter completed acquisition of the former's stake in 2013. Its production involves gravity feeding a molten polymer, composed of extruded polypropylene and other polyolefins, through a four-storey chamber. This creates sheets of the substrate used as the base material by many central banks in the printing of polymer banknotes. ProductionPolypropylene is processed to create pellets.{{sfn|Garoffolo|Sientek|2009|p=25}} These pellets are extruded from a core extruder in conjunction with polyolefin pellets from two "skin layer" extruders, and are combined into a molten polymer.{{sfn|Garoffolo|Sientek|2009|p=25}}{{sfn|Hardwick|Ghioghiu|2004|p=6}}{{sfn|Innovia Security|2013}} This consists of a 37.5µm thick polypropylene sheet sandwiched between two 0.1 µm polyolefin sheets,{{sfn|Innovia Security|2013}}{{sfn|Hardwick|Ghioghiu|2004|p=6}} creating a thin film 37.7 µm thick. The molten polymer undergoes snap cooling as it passes by gravity feeding through a brass mandrel, which imparts on the thin film many properties, including its transparency.{{sfn|Garoffolo|Sientek|2009|p=25}} The cast tube material is then reheated and blown into a large bubble using air pressure and temperature.{{sfn|Garoffolo|Sientek|2009|p=25}} At the base of the four-storey chamber convergence rollers collapse the tube into a flat sheet consisting of two layers of the thin film.{{sfn|Innovia Security|2013}}{{sfn|Garoffolo|Sientek|2009|p=25}} This creates the base biaxially-oriented polypropylene substrate of 75.4 µm thickness, called ClarityC by Innovia Films.{{sfn|Hardwick|Ghioghiu|2004|p=6}}{{sfn|Bank of Canada: Life Cycle Assessment of Canada's Polymer Bank Notes and Cotton-Paper Bank Notes|2011|p=32}} The base substrate is slit as it exits the convergence rollers.{{sfn|Garoffolo|Sientek|2009|p=25}}{{sfn|Innovia Security|2013}} Four {{convert|3|µm}} thick layers of (usually white) opacifier are applied to the substrate, two on the upper surface and two on the lower surface.{{sfn|Hardwick|Ghioghiu|2004|p=6}}{{sfn|Innovia Security|2013}} A mask prevents the deposition of the opacifier on parts of the substrate that are intended to remain transparent.{{sfn|Hardwick|Ghioghiu|2004|p=1}} These overcoat layers protect the substrate from soiling and impart on it its characteristic texture,{{sfn|Hardwick|Ghioghiu|2004|p=2}} and increase the overall thickness to 87.5 µm. The resulting product is the Guardian substrate.{{sfn|Innovia Security|2013}} The opacifier conversion phase involves the use of resin and solvents, creating volatile organic compounds (VOCs) as by-products that are combusted in a thermal oxidizer.{{sfn|Bank of Canada: Life Cycle Assessment of Canada's Polymer Bank Notes and Cotton-Paper Bank Notes|2011|p=32}} The resulting polymer substrate then passes through a rotary printing press using chrome-plated copper cylinders.{{sfn|Bank of Canada: Life Cycle Assessment of Canada's Polymer Bank Notes and Cotton-Paper Bank Notes|2011|p=32}} After printing, the holographic security foil is incorporated into the base substrate.{{sfn|Bank of Canada: Life Cycle Assessment of Canada's Polymer Bank Notes and Cotton-Paper Bank Notes|2011|p=32}} This is then cut into sheets and transported to the banknote printing companies in wooden boxes as a secure shipment.{{sfn|Bank of Canada: Life Cycle Assessment of Canada's Polymer Bank Notes and Cotton-Paper Bank Notes|2011|p=32}}{{sfn|Robertson|2011}} PropertiesGuardian is a non-porous and non-fibrous substrate.{{sfn|Garoffolo|Sientek|2009|p=25}} Because of this, it is "impervious to water and other liquids", and so remains clean for longer than a paper substrate.{{sfn|Garoffolo|Sientek|2009|p=25}} It is difficult to initiate a tear on the substrate, which has higher tear initiation resistance than paper.{{sfn|Garoffolo|Sientek|2009|p=25}} Polymer banknotesGuardian is used in the printing of polymer banknotes by many central banks. It is the base material used for currencies printed by:
In 1993, the Bank of Indonesia issued a commemorative {{currency|50000|IDR}} banknote and the Central Bank of Kuwait issued a د.ك1 banknote.{{sfn|Innovia Security|September 2013}} In 1998, the Bank Negara Malaysia issued a commemorative {{currency|50|MYR}} banknote,{{sfn|Innovia Security|September 2013}} and the Central Bank of Sri Lanka issued a commemorative Rs200 banknote.{{sfn|Eu|Chiew|Straus|2006|p=124}} In 1999, the Northern Bank of Northern Ireland issued a commemorative {{currency|5|GBP}} banknote,{{sfn|Eu|Chiew|Straus|2006|p=90}} and the Central Bank of the Republic of China in Taiwan issued a commemorative {{currency|50|TWD}} banknote.{{sfn|Eu|Chiew|Straus|2006|p=126}}{{sfn|Innovia Security|September 2013}} In 2000, the Central Bank of Brazil issued a commemorative {{currency|10|BRL}} banknote{{sfn|Eu|Chiew|Straus|2006|p=42}} and the People's Bank of China issued a commemorative ¥100 banknote.{{sfn|Innovia Security|September 2013}} In 2001, the Central Bank of Solomon Islands issued a commemorative SI$2 banknote.{{sfn|Eu|Chiew|Straus|2006|p=122}} In 2009, the Bank of Mexico issued a commemorative $100 banknote.{{sfn|Innovia Security|September 2013}} NotesReferences{{refbegin}}
Further reading
2 : Polymers|Brand name materials |
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