PBT and optical cable grade PBT

PBT is the latest developed variety among general engineering plastics. It was developed by GE Company and was only industrialized in the 1970s, but it developed very quickly. It has high comprehensive performance, good processing and formability, and high cost performance. PBT, PPO, POM, PC and PA are collectively called the five major general-purpose engineering plastics.

The Global PBT Plastic market is anticipated to rise at a considerable rate during the forecast period, between 2023 and 2031. In 2023, the market is growing at a steady rate [CAGR] and with the rising adoption of strategies by key players, the market is expected to rise over the projected horizon.

Currently on the market, the main uses of PBT can be divided into:

（1）Modified engineering plastics: Mainly used in automobile parts, electronics, electrical appliances, small household appliances, commercial machines and communication equipment. The approximate proportions are lighting appliances 42%, electronic industry 32%, home appliances 11%, and automotive parts 7%. Among them, lighting appliances mainly refer to energy-saving lamps. The main reason is that Western countries such as North America, the European Union, and Australia have legislated to eliminate incandescent lamps and replace them with energy-saving lamps around 2010. China's energy-saving lamp production accounts for more than 70% of the world's output, 80% of which is exported. Since the lamp holders of energy-saving lamps use a large amount of PBT alloy, the demand for PBT in this industry is very strong. The use of PBT in the automotive industry is also growing rapidly, such as car lights, grilles, connectors, etc.

（2）Spinning: wig filament, brush filament, elastic fabric. Spinning is the fastest growing use of PBT in recent years. It was first used in brush filaments such as toothbrushes, and is characterized by non-shedding. But currently the fastest growing usage is elastic fabrics. The elasticity of PBT fiber is between spandex (Lycra) and polyester. Its dyeability is better than spandex. It feels soft like wool. It can be made into silk alone or blended with polyester. The most important thing is that the price is much lower than spandex. It is currently being gradually used in various fabrics that require elasticity, such as underwear, elastic jeans, and sportswear.

（3）Fiber optic cable jacket: Loose tube used to protect optical fiber. Since the beginning of this year, due to the issuance of domestic 3G licenses and the development of village-to-village and FTTH construction, the demand for optical cables has surged, driving a surge in demand for PBT.

（4）Film: rainbow film, food packaging film. PBT films are widely reported in Japan and are mainly used as the outermost layer of food packaging composite films. The most commonly used film in China is rainbow film, which uses microscopic layering of PBT and PMMA to achieve a rainbow effect. It is used for packaging of candies, gifts, etc. Its current usage is growing rapidly.

The above four major categories of uses are currently in the fastest growing fields, and it is foreseeable that the demand will grow very rapidly in the next few years. Asia-Pacific has been one of the major regions for plastic consumption, especially in electronics, automotive and industrial applications. China, Japan, South Korea and other Southeast Asian countries are the main markets for PBT. Europe is also an important region for the engineering plastics market, especially in automotive and industrial manufacturing. Some European countries may have higher demand for PBT. China has been expanding its plastics production capacity in the past few years to meet domestic and international market demand. Engineering plastics, including PBT, may receive attention and investment. There are some major chemical companies and plastic manufacturers in China, such as Formosa Plastics, Huadong New Materials, Sinopec Yizheng, etc., involved in the production of PBT engineering plastics.

The optical communications market continues to grow as global demand for broadband and high-speed Internet connections continues to increase. Optical cables play a key role in this trend, and optical cable-grade PBT, as a type of optical cable material, will benefit from the growth of the optical communications market. What is the difference between ordinary PBT and optical cable grade PBT? 

• PBT is generally required to have an intrinsic viscosity between 1.2 and 1.3. The viscosity of ordinary PBT is between 0.8-1.0. Japanese experts once mentioned using 1.35 PBT as the main body of optical cable PBT. The reason is to ensure that when extruding the casing stability.

• The reason for proper reinforcement of PBT is to ensure a certain strength of the optical fiber casing.

PBT is obtained from BDO and PTA through transesterification. The reaction is reversible, and both acids and bases can promote the reaction. To increase the intrinsic viscosity is to increase the molecular weight of PBT. Two methods can be used: (1) Add chain extenders to connect PBT molecules to each other and increase the molecular weight; (2) Remove small molecules to allow the reaction to continue to occur and increase the molecular weight.

There are currently three ways to produce PBT for optical cables, each with its own advantages and disadvantages:

 1. Use a twin-screw extruder and add chain extenders, stabilizers and other additives. The molecular weight of PBT increases through the action of chain extender in the screw, and the intrinsic viscosity of PBT increases. Through the shearing action of the twin screws, the added additives such as tougheners and end-capping agents are dispersed very evenly, which can improve the hydrolysis resistance of PBT. However, the disadvantage is that the chain extension reaction is difficult to control. It is related to many factors such as moisture, temperature, additive dispersion, and whether the screw is vented. The product quality is difficult to control. Some foreign companies have used this method, but currently few companies use it.     

2.Use a vacuum drum to maintain it at a certain high temperature for a certain period of time. The small molecules are removed by vacuuming to increase the molecular weight and viscosity of PBT. Add a masterbatch containing additives during or after the viscosity increase. The advantages are low equipment investment, flexible production arrangements, and high uniformity of products produced by the same drum. The disadvantage is that the production volume of each batch is small, generally less than one ton per batch. The production process cannot be monitored, and product quality is closely related to the experience of the operators. Quality fluctuations are prone to occur if personnel are replaced. In addition, it is difficult to reduce the carboxylic acid group content only by increasing the vacuum degree, so this method has certain difficulties in improving the hydrolysis resistance of PBT.

3. Use a solid-phase thickening tower to remove small molecules with hot pure nitrogen to increase the molecular weight of PBT and thicken it. Add a masterbatch containing additives during or after the thickening process. The advantage is that the production batch is large, and the quality can be monitored in real time during the production process; the carboxylic acid group content is small, and the product has strong hydrolysis resistance. The disadvantage is that the initial investment is large, and product stability is related to the uniformity of the masterbatch added.

 At present, many domestic factories use the second method to produce PBT for optical cables. The reason is that the investment is small and domestic users have low hydrolysis resistance requirements for PBT. Currently, only Yizheng Chemical Fiber in China has a solid-phase thickening tower imported from Germany with an annual production capacity of 6,000 tons. Neither the Changchun Changshu factory nor Blue Star Nantong factory that recently invested has introduced solid-phase viscosity increasing equipment. Shanghai Haiyouwei Electronic Technology Co., Ltd. (Gongcheng Communications) and Yizheng Chemical Fiber Group Engineering Plastics Factory began to cooperate in the research and development and production of optical cable grade PBT in 2004, and applied for two national invention patents. Currently, production has reached full capacity.

The development of smart cities and the Internet of Things (IoT) poses new challenges and opportunities to the demand for optical cables. Cable-level PBT may need to adapt to more complex and diverse application scenarios, including smart city infrastructure and large-scale IoT deployments.

There are three directions for improving optical cable grade PBT: (1) improving hydrolysis resistance; (2) improving adaptability to high-speed extrusion; (3) improving strength.

 If you are interested in PBT engineering plastics, you can contact the engineering plastic raw material agent--QINGDAO PRIME UNION.

QINGDAO PRIME TRADE CO., LTD is a company with more than 21 years of experience that specializes in distributing international brand engineering plastic particles. It mainly represents: CHIMEI ABS, HANWHA TOTAL PP, SABIC PPO, PC special materials, and BASF PBT. We also have our own modification processing factory, Qingdao primetech  Plastic Co., Ltd., with a professional technical team to provide you with fast and professional services to meet the needs of customers at different levels.