Transparent nylon is widely used in household goods, electronic equipment, precision optical instruments, sports equipment, health care and automotive industries due to its excellent transparency, excellent toughness, high thermal stability and good solvent resistance. Recent studies have found that some nylon materials have both transparency and ferroelectricity, making them an important component of flexible electronic products and are expected to be used in wearable devices.
Types of transparent nylon
1.Aliphatic Transparent Nylon
Aliphatic transparent nylon is a transparent material obtained by polycondensation of aliphatic dibasic acid and aliphatic diamine, ring-opening polymerization of lactam or polycondensation of amino fatty acid. The polymerized monomer can be a linear monomer or a monomer containing an alicyclic ring. The introduction of an alicyclic ring can greatly reduce the regularity of the polyamide chain segment, weaken the crystallization ability and enhance the transparency.
Representative polymers include PACM12, PACP-9/6, PA6/66, BMACM14, PA6/12, PA11/12, etc.
2. Semi-aromatic transparent nylon
Semi-aromatic transparent nylon is generally made by copolymerization of aliphatic dibasic acid and aromatic diamine or aliphatic diamine and aromatic dibasic acid. Due to the introduction of aromatic rings in the molecular chain, the heat resistance and mechanical properties are greatly improved, while the water absorption rate is reduced. In fact, semi-aromatic transparent nylon is the most popular type of transparent nylon on the market.
Representative polymers include PA6T/6I, PA10I/10T, PA6-3-T, MXD6, etc.
3. Aromatic transparent nylon
Fully aromatic transparent nylon is prepared from aromatic dibasic acids and aromatic diamines. The proportion of rigid aromatic rings in its main chain is high, the polymer has good crystallinity, and its heat resistance and solvent resistance are also the best among all polyamides.
The representative polymer is synthesized with 2-amino-6-(4-aminophenyl)-6-methylheptane and diphenyl isophthalate as monomers. However, its melting temperature is high and the requirements for molding equipment are extremely stringent, so this type of fully aromatic transparent polyamide has not been industrialized.
4. Complex structure transparent nylon
The monomer structure of this type of nylon material is complex and its source is limited, so it is mainly a laboratory research product. The research focuses on improving the adaptability of this type of material in special environments by introducing special heteroatoms or heterocycles such as trifluoromethylphenoxy, tert-butylcyclohexyl, xanthene, and sulfone groups on the main chain.
Main transparent nylon products
The world's first transparent nylon was successfully developed and marketed by Dynamit Nobel in the late 1950s under the trade name Trogamid T. Its successful development has aroused the enthusiasm of manufacturers around the world to develop transparent nylon materials.
At present, the world's well-known transparent nylon manufacturers mainly include EMS, LANXESS, UBE, DuPont, Evonik, Arkema, BASF, Toboyo, Philips, etc. The main transparent nylon materials currently on the market are shown in Table 1.
Emmans is a top professional manufacturer and supplier of high-performance polyamides. Its Grilamid TR series and Grilon C series include a variety of transparent nylons.
The Grilamid TR series mainly includes semi-crystalline nylon 12 and rigid groups, which have high chemical resistance, stress cracking resistance and excellent transparency. The more representative products in this series include GrilamidTR30 (PA6I/X), GrilamidTR55 (PA12/MACMI), GrilamidTR90 (PAMACM12) and GrilamidTRXE4010 (PAMACM10/1010).
Image source: Emmans
The Grilon C series is mainly PA6/12 copolymer, which has weak crystallinity and poor thermal and mechanical properties. Representative products include GrilonCF6S, GrilonCF7, GrilonCR8, etc.
In 1988, Evonik acquired Nobel and took over the production of TROGAMID®T. The polyamide has long-lasting and high transparency, and has good heat resistance due to the aromatic ring in the molecule. Its disadvantage is that the transmittance of the colored resin is low, and the product was discontinued in 2020.
In 1995, Evonik developed a new product line TROGA-MID®CX by using 4,4′-diamino-dicyclohexylmethane (PACM) and dodecanedioic acid as monomers for polycondensation reaction. This transparent polyamide has excellent light transmittance (92%), excellent corrosion resistance and stress cracking resistance, very high toughness and low-temperature wear resistance. After more than 20 years of development, this product has become a mainstream product in the market.
In 2021, Evonik developed a new generation of product line based on bio-based monomers, TROGAMID® myCX eCO. Compared with products of comparable quality produced using conventional fossil raw materials, this production line reduces the carbon footprint by 50% and is environmentally friendly.
Image source: Evonik
DuPont has successfully developed transparent engineering resins based on nylon 66. After more than 50 years of improvement and refinement, it has developed product lines such as Selar® and Zytel®. Among them, Selar® PA3426 is a non-crystalline nylon polyamide resin with high transparency and barrier properties, making it play a "glass-like" role in rigid composite packaging.
And by adding PACM to the molecular chain, Zytel® 330NC010 came into being. Compared with PA3426, its crystallization ability decreases, the glass transition temperature increases by 5°C, and the barrier ability to gas, water solvents and oil products is further improved.
Arkema is the first manufacturer to provide high-performance, bio-based transparent polyamide. Its transparent nylon product line is the Rilsan® Clear series, including G170, G830, G850, etc. Its main features are light weight and transparency. Among them, G850 has a density of only 1.01g/cm3 and is usually processed by injection molding.
Figure Application of transparent nylon in electronic cigarette structural parts
It is worth mentioning that the raw materials of Arkema's transparent nylon products are mainly bio-based raw materials. 62% of the raw materials in G820 are bio-based, which is environmentally friendly.
Lanxess has developed a series of transparent engineering thermoplastics based on polyamide 6 and polyamide 66. Among them, the Durethan® T series focuses on the high transparency market, including two product lines, T40 and T40ZS. Its molecular chain contains a rigid benzene ring structure, which has excellent mechanical properties and transparency. Toyobo Co., Ltd. also has a product with a similar structure, named T714-E.
Ube focuses on the development of nylon 6/66 and nylon 12. The UBENYLON50 series is mainly developed for high-transparency nylon 6/66 copolymers; the UBESTAXPA series is a new type of polyamide elastomer developed with the goal of improving flex fatigue properties while retaining transparency.
PACP-9/6 produced by Philips is a transparent polyamide obtained by co-condensation of PACP, azelaic acid and adipic acid. It has excellent light transmittance (92%), very low water absorption (1%) and typical rigidity of engineering plastics (flexural modulus 2185Pa), and can be extruded and blown on general equipment.
BASF mainly has two product lines in the transparent nylon industry: Ultramid® Vision and Ultramid® FBalance. The Vision series uses nylon 6 as raw material, which is characterized by low price, easy processing and good coloring effect, which is significantly different from other polyamide materials. The Ultramid® FBalance series is doped with long-chain amide units, focusing on mechanical properties and good adhesion to PU film.
Application of transparent nylon
1. Household items
In 2020, Emmans proposed the concept of "transparent kitchen" based on its product Grilamid TRHT170. Before that, transparent nylon had penetrated into all aspects of home life. Its transparency, heat resistance and shape retention properties made it widely used in faucets, water filters, flow meters and various household containers. And due to the excellent colorability of transparent nylon, its application range in the home field has been further broadened.
In addition, in the field of soft and hard packaging such as baby bottles and cosmetics, transparent nylon has also been widely used due to its sterile and durable characteristics. Major companies have launched corresponding products to meet different market needs.
2. Optical field
In May 2021, Safilo Eyewear announced that it would use Evonik's latest polyamide material, TROGAMID®myCXeCO, in the production of high-end sun lenses to improve product performance and environmental friendliness.
Prior to this, polyamide materials have been widely used in the manufacture of glasses and their components. As an ideal transparent material, the TROGAMID®CX series can meet the current market's many requirements for advanced frame and lens materials: light weight, not easy to break, scratch-resistant, chemical corrosion-resistant and stress crack-resistant. And it is not easy to cause allergies and is UV-resistant, which greatly broadens the scope of application. At present, TROG-AMID®CX7323 has been widely used in the high-end eyewear market.
In addition, Rilsan® Clear G850 produced by Arkema is also widely used in eyeglass frames due to its extremely low density.
3. Electronic devices
At present, transparent nylon materials have been used in various switch and relay housings due to their light weight, high temperature resistance and corrosion resistance, and play an important role in the packaging of microelectronic products. By combining the ferroelectric properties of nylon materials with their transparency, researchers have developed new polyamide materials such as Morse code detectors, electromagnetic interference shielding materials, and film capacitors.
4.Sporting goods
The excellent bending and abrasion resistance of transparent nylon can meet the performance requirements of athletes in intense competitions. In 2006, the English football shoes of the German World Cup used Ube's UBESTAXPA series of transparent nylon products. Its transparency has a great impact on the design of the shoes, and the material can be firmly bonded with polyurethane, increasing the design freedom of the product.
The Pebax® material (Arkema), which came out in 1980, has had a profound impact on modern sports. Its structure contains rigid nylon units and flexible polyester units. The outstanding performance of Pebax® material makes it used in the products of major sports manufacturers.
In addition, transparent nylon is also widely used in diving computers, camera packaging shells, sports watch cases and other fields.
5. Healthcare
Due to the COVID-19 pandemic, the global demand for medical protective equipment is increasing. Transparent nylon meets the needs of the healthcare market due to its light weight, water and oxygen resistance, and good mechanical properties.
Arkema's product Rilsan Clear G-170 MED has high transparency (91%), low density (1.05g/cm3), flexibility and durability, easy handling and assembly, and meets the needs of patient comfort. It is widely used in respiratory masks, hearing aids and medical tubing. In addition, nylon materials have been widely used in other medical devices such as PM2.5 protection windows and artificial muscle tissue.
6. Automotive Industry
Nylon is well suited for the automotive industry because of its high-speed transmission of light and its ability to withstand repeated exposure to corrosive media such as sunscreen, detergents and disinfectants without sustaining damage.
The Ultramid® Vision series from BASF can be used for backlighting components such as switches or operating displays. Ultramid® Vision B3KDLT is particularly suitable for light-resistant covers. In addition, transparent nylon is widely used in gasoline filters, oil/water separators, remote control systems and rearview mirrors.
Since its introduction, transparent nylon has experienced great development. Due to its excellent transparency, high thermal stability, good corrosion resistance and excellent mechanical properties, transparent nylon is widely used in household goods, precision optics, electronic equipment, sporting goods, healthcare and the automotive industry, with a wide range of products.
With the rise of wearable devices and electronic textiles, people are increasingly demanding lightweight, transparent, low-cost bendable materials. Some nylon materials are seen as potential base materials for the next generation of flexible transparent electronic devices. By integrating single-walled carbon nanotubes, graphene, polymethyl methacrylate, acetate fiber and other materials with nylon, researchers have prepared a variety of highly transparent new electronic textiles.
In addition, by replacing petroleum-based raw materials with bio-based raw materials, the transparent nylon industry is moving towards green chemistry. Evonik, BASF, Ube, Biond and other major transparent nylon manufacturers in the world have laid out the bio-based nylon industry. In the future, all-bio-based nylon is expected to become a reality and have a profound impact on people's lives. (The following picture is from: Biond booth)
