Guardian (polymer)


Guardian is the trademark name of a polymer originally manufactured by Securency International, 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.

Production

is processed to create pellets. 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. This consists of a 37.5µm thick polypropylene sheet sandwiched between two 0.1 µm polyolefin sheets, 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. The cast tube material is then reheated and blown into a large bubble using air pressure and temperature. 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. This creates the base biaxially-oriented polypropylene substrate of 75.4 µm thickness, called ClarityC by Innovia Films.
The base substrate is slit as it exits the convergence rollers. Four thick layers of opacifier are applied to the substrate, two on the upper surface and two on the lower surface. A mask prevents the deposition of the opacifier on parts of the substrate that are intended to remain transparent. These overcoat layers protect the substrate from soiling and impart on it its characteristic texture, and increase the overall thickness to 87.5 µm. The resulting product is the Guardian substrate.
The opacifier conversion phase involves the use of resin and solvents, creating volatile organic compounds as by-products that are combusted in a thermal oxidizer. The resulting polymer substrate then passes through a rotary printing press using chrome-plated copper cylinders. After printing, the holographic security foil is incorporated into the base substrate. This is then cut into sheets and transported to the banknote printing companies in wooden boxes as a secure shipment.

Properties

Guardian is a non-porous and non-fibrous substrate. Because of this, it is "impervious to water and other liquids", and so remains clean for longer than a paper substrate. It is difficult to initiate a tear on the substrate, which has higher tear initiation resistance than paper.

Polymer banknotes

Guardian is used in the printing of polymer banknotes by many central banks.
It is the base material used for currencies printed by:
CountryCentral bankCurrencyBanknotes
AustraliaReserve Bank of AustraliaAustralian dollar
BangladeshBangladesh BankBangladeshi taka
BruneiBrunei Currency and Monetary BoardBrunei dollar
CanadaBank of CanadaCanadian dollarFrontier Series
ChileCentral Bank of ChileChilean peso
Costa RicaCentral Bank of Costa RicaCosta Rican colón
Dominican RepublicCentral Bank of the Dominican RepublicDominican peso
GuatemalaBank of GuatemalaGuatemalan quetzal
HondurasCentral Bank of HondurasHonduran lempira
Hong KongHong Kong Monetary AuthorityHong Kong dollar
IndonesiaBank of IndonesiaIndonesian rupiah
IsraelBank of IsraelIsraeli new shekel
MalaysiaBank Negara MalaysiaMalaysian ringgit
MauritaniaCentral Bank of MauritaniaMauritanian ouguiya
MauritiusBank of MauritiusMauritian rupee
MexicoBank of MexicoMexican peso
MozambiqueBank of MozambiqueMozambican metical
NepalNepal Rastra BankNepalese rupee
New ZealandReserve Bank of New ZealandNew Zealand dollar
NicaraguaCentral Bank of NicaraguaNicaraguan córdoba
NigeriaCentral Bank of NigeriaNigerian naira
Papua New GuineaBank of Papua New GuineaPapua New Guinean kina
ParaguayCentral Bank of ParaguayParaguayan guaraní
RomaniaNational Bank of RomaniaRomanian leu
SamoaCentral Bank of SamoaSamoan tālā
SingaporeMonetary Authority of SingaporeSingapore dollar
ThailandBank of ThailandThai baht
United KingdomBank of EnglandPound Sterling
VanuatuReserve Bank of VanuatuVanuatu vatu
VietnamState Bank of VietnamVietnamese đồng
ZambiaBank of ZambiaZambian kwacha

In 1993, the Bank of Indonesia issued a commemorative banknote and the Central Bank of Kuwait issued a د.ك1 banknote. In 1998, the Bank Negara Malaysia issued a commemorative banknote, and the Central Bank of Sri Lanka issued a commemorative Rs200 banknote. In 1999, the Northern Bank of Northern Ireland issued a commemorative banknote, and the Central Bank of the Republic of China in Taiwan issued a commemorative banknote. In 2000, the Central Bank of Brazil issued a commemorative banknote and the People's Bank of China issued a commemorative ¥100 banknote. In 2001, the Central Bank of Solomon Islands issued a commemorative SI$2 banknote. In 2009, the Bank of Mexico issued a commemorative $100 banknote.