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Smart card, also known as IC card, refers to the card in which IC chips are encapsulated. IC card has many characteristics, such as large storage capacity, high data security, good anti-counterfeiting, low cost of application equipment and mature technology, and has been widely used in finance, public security, transportation, communication, service, medical and other fields.

Since 1984, France has made great progress in using IC card in telephone card and has achieved great success. China started the gold card project in 1993, and the technology and market have been relatively mature.

The plastic sheet materials for IC card production are called card based materials. The current general card based materials are ABS (acrylonitrile butadiene styrene 1, PVC (PVC), pet (polyethylene terephthalate), PC (polycarbonate), PETG (modified PET), etc. PVC is the most widely used carnivore material, but because of the chlorine in PVC, it is not conducive to environmental protection. In recent years, with the continuous introduction of new materials and the rapid development of IC card technology, the materials used for card based materials are also changing. Some new card based materials which are environmentally friendly and high temperature resistant and can be preserved for a long time have been launched successively, such as PETG, PC, PC / PBT, etc. each material has different characteristics, and should be selected according to different needs.

2. introduction of kaki materials

2.1 PVC material

PVC (PVC) granular rubber is a multi-component plastic, because of the different content of each component, the appearance of the different. There are transparent materials, also have opaque materials: some soft and elastic, folding resistance; There are also hard and rigid mechanical properties of good materials. Most PVC is slightly toxic, but also has food grade PVC glue particles.

PVC can be divided into soft PVC and hard PVC. The surface hardness, tensile strength and rigidity of rigid PVC are close to the index of engineering materials. Soft PVC is generally used for wallpaper, floor, ceiling and leather surface. Hard PVC becomes brittle at low temperature, and it is sensitive to change. It cannot be completely restored after deformation: soft PVC becomes hard at low temperature, poor thermal stability and degradation by heating

At the same time, PVC card base materials still occupy a large proportion of market share while various new card based materials are gradually popularized and applied. This is because of its low production cost and superior performance. PVC film can be printed and hot pressed without any treatment. Therefore, it still has great application. PVC material is suitable for card surface, and magnetic strip is required, IC card with signature or convex and holographic sign. However, it is not environmentally friendly and will release HCl gas at high temperature, which is harmful to the environment. The industry has begun to phase out PVC card base materials.

With the development of plastic industry, some PVC composites have appeared, such as PVC / ABS, PVC / PET, PVC / PE, etc., and their properties have been improved compared with PVC.

2. 2 PET  

Pet is a thermoplastic polymer, which is formed by esterification of terephthalic acid and glycol. It is a crystalline polyester with obvious melting point, melting at 250 ℃ and decomposition at 360 ℃: the general processing temperature is 280 ℃ to 320 ℃ (see Table 1); Pet is a colorless, transparent, high hardness and tough material. Therefore, pet is the base material for the production of photographic film, and can also be used to produce audio tape and video tape. PET film materials have low specific gravity, non hygroscopic, high insulation and transparency, excellent mechanical properties, small deformation, good phase range wear resistance, good chemical corrosion resistance, high surface finish and long service life of the cards. Meanwhile, pet is also an environmental protection material. South of these

PET material is widely used in the card making industry.

PET film material is made by two-way drawing process. After biaxial stretching, the initial amorphous macromolecular chain crystallizes along the direction of stretching. The deformation of molecular chains in each position of the film is not very consistent, the smaller the deformation of the molecular chain is closer to the center line, and the orientation direction is not the same. The general direction is gradually approaching both sides along the center line, and the deviation angle is proportional to the tensile ratio. Therefore, PET materials should be used in pairs during the use. If the stress direction of the material is not paid attention to, the deformation direction of polymer materials on both sides of the card body is inconsistent, which will cause warping of the card body.

The original state of PET material is not suitable for printing and hot pressing bonding, which needs surface treatment. Pet surface becomes easy to print and bond. At present, the research focuses on improving its antistatic, printing adaptability and adhesion.

The surface modification is mainly treated by corona, gluing and light grafting, which makes the surface functionalized. Achieve the purpose of printing and bonding.

At present, most of the common pet protective films are coated with a layer of hot melt adhesive on the pet surface. For example, EVA, and some are to synthesize a low melting point polyester compound on the pet surface by surface photopolymerization grafting technology, so as to improve the printing and adhesion. DuPont has a kind of pet protective film, which is named melinex PETF 3368. The film is made by special technology to change the crystallization state of pet and co extrude with ordinary PET film. This kind of card base material can support many printing technologies, and can be bonded with the card body quickly at 120 ℃ and the bonding process is irreversible. This material has been widely used in Europe and the United States, but because of its high cost, there are only some important legal documents in China.

Because PET film needs printing or printing patterns at many times, the surface electrostatic treatment is also a hot topic. According to the specific requirements of PET film, the problems can be solved by spraying or spraying antistatic liquid, antistatic particles on the surface of PET film materials. The first Research Institute of the Ministry of public security has rich experience in this field. Some anti-static technology has been used in the process of large-scale certification making, and has achieved a very good anti-static effect.

2．3 ABS  

ABS is a kind of light yellow opaque particle ABS with high gloss and is a non crystalline material, with a specific gravity slightly heavier than water (see Table 1). ABS material has high rigidity and medium tensile strength: it has good chemical corrosion resistance and surface hardness, good toughness and impact resistance, easy to process, strong fluidity, easy to print and dye.

Different ABS materials can be made by changing the ratio of three monomers and molecular structure in two phases. The properties of different types of ABS materials are also very different. Generally speaking, all kinds of ABS materials have good luster, high hardness, tenacity, rigidity, moderate mechanical properties and other characteristics. Because it is easy to print and electroplating surface treatment and the size is stable, it is suitable for making card base materials. One disadvantage of ABS as card base material is that it can not be printed with convex characters. In addition, the ABS has poor weather resistance, easy aging, fading and brittle mobile phone SIM card uses PVC + ABS mixture. This material can be used in the high temperature environment of mobile phone. If the use environment of card body requires heat resistance and flame retardant, ABS card base material will be used generally.

2.4 PC and its alloy materials

1) PC (polycarbonate) is tough and tough, with high transparency. The surface has high gloss and mechanical strength close to nylon: impact resistance, high temperature resistance, friction resistance and resistance

Stress cracking (see Table 1), which can swell in steam and many organic solvents and lead to stress cracking. PC materials have high processing temperature and high requirements for lamination card equipment. Some cards in the United States use PC materials, and some high-end cards are produced by PC in domestic card factories. Because of the high carbon content of PC and no harmful gas release at high temperature, PC materials can be used for laser etching and anti-counterfeiting.

2) PC alloy material, compared with PC, PC alloy material has been widely used for its good processing properties. PC PBT is a blend of PC and PBT, which retains the advantages of both: high temperature shape, stress cracking resistance, high surface hardness, high rigidity and toughness. This material is mainly used to make large or precise instrument case, such as mobile phone case or automobile instrument panel, etc. its film material can also be used as card base material, which has good printing and environmental protection. Ge and Mitsubishi have film products of the material, which is widely used on Japanese cards.

Another is PC / ABS plastic: PC ABS has the easy to add property of ABS, and has good mechanical and thermal stability of PC, high surface hardness, high rigidity and toughness, high stress cracking resistance: the mechanical properties are between ABS and PC. This kind of carnivore material is relatively used less.

2．5 PETG  

PETG is a kind of polyester which is modified by the copolymerization of ethylene glycol (eg) and terephthalic acid (TPA) polycondensated polyester (PET) by 1,4-cyclohexane dimethanol (CHDM), and is an amorphous copolyester. The material has high transparency, high impact resistance, high hardness and good low temperature toughness. It is widely used in the fields of sheet, high performance shrink film, profile, toys, food, high-grade packaging materials, etc.

PETG has been used more and more in the card industry because it has lower temperature of adding (about 100%), high mechanical strength and excellent flexibility, higher transparency, better luster than PVC, easy to print and environmental protection advantages.

PETG materials are widely used in electronic payment and identification documents in Europe, USA and Elben. Visa has approved PETG as its card base material. PETG has been used as the card base material for some high-grade cards and important legal documents in China.

The manufacturers of PETG resin in the world are mainly Eastman company and SK company. The manufacturers of the base materials are all purchasing PETG resin and formula to add t-forming plates, sheets, films and so on by calendering or casting. Currently, there are four domestic manufacturers of PETG materials, all of which are using imported Eastman resin to produce the card base materials.