By Liu Chunsheng, Sionpec Yizheng Chemical Fiber Co., Ltd.
Netherland-based DSM Co., Ltd. developed dry spinning technology - with decalin as solvent in late 1970s, and by adoption of the technology, the producer made ultra-high molecular weight polyethylene fiber (UHMWPE) successfully. The product has been put into commercial production since 1990.
China’s Donghua University (formerly China Textile University) started research on wet spinning technology in 1984, brought the technology into a trial use in 1997 and upsized the adoption in 1999. Later on, the technology was applied widely across the nation.
Based on the wet and dry spinning technologies with independent intellectual property rights, the UHMWPE market has been growing fast in China in recent years, with technologies upgrading continuously, quality of products becoming higher and wider application fields being explored.
At present, there are nearly 20 UHMWPE producers in China. The total capacity in 2018 was at 25 680 t/a, the output at 17 350 tons, the import volume at 650 tons and the export volume at 4 635 tons.
The rapidly increasing capacity and output are capping the prices, low at RMB400 000/t in 2007 and down further to RMB100 000/t now. The price downtrend will be favourable to explore the application and strengthen demand.
The proportion of UHMWPE for civil use and military use is approximately at 7:3 in the domestic market today. The civil-use UHMWPE market, featured with strong demand, good stability and wide application fields, is considered a good way to prop up healthy development of the whole industry. The exploration in civil textile fields, in turn, will lead to lower prices and greater market potential.
Exploration of application fields
Civil-use fields
The consumption of UHMWPE in China totaled 13 365 tons in 2018, with that in rope net sector at 3 320 tons, taking up 24.8%; that in gloves sector at 4 945 tons, occupying 37.0%; that in bulletproof and protection sector at 3 530 tons, taking up 26.4%; that in textile sector at 1 570 tons, accounting for 11.8%.
Military-use and aviation fields
Thanks to the highly wear-resistance protective performance, it is applied in the production of protective panels for armored vehicles, protective linings for tanks, bulletproof helmets, shields, body armors, lightning-proof boots, explosion-proof carpets, cut-resistant gloves, light composite armors, battlefield hospitals, and battlefield tents. In addition, by virtue of properties such as low dielectric constant, low dielectric loss and high sonar transmittance, it is used in the production of antenna radome, missile cover and radar protective cover. With the light weight and high strength, it is also applied in the production of cable and towing rope for warship and armored vehicles, as well as military ropes such as torpedo mooring cable and parachute rope. Besides, it is used in the fields such as aircraft wing tip structure, spacecraft structure, buoy component, drone shell and special umbrella materials because of the high strength, impact-resistance and light weight.
Cable and rope field
With excellent properties such as light weight, high strength, wear-resistance, anti-corrosion and anti-ultraviolet light, it is used in the production of negative-gravitropism rope, heavy-loading rope, salvage rope, towing rope, sailing rope and fishing line, as well as fixed anchor rope for super tanker, marine operating platform and lighthouse; besides, it is used in the production of marine fishing trawl and large-sized marine cage culture; it is also applied in the production of construction sling, seat belt, safety net and household escape rope.
In addition to the applications mentioned above, UHMWPE is applicable to various materials as enhancer. For example, concrete can have stronger quake-resistance and impact resistance with ultra-short fiber blended into it; the biocompatibility of UHMWPE enables artificial skeletal joints to have higher strength and stronger wear-resistance, so UHMWPE is favored by the sector.
Future development trend
There are six technological development directions in China. The first direction is to develop stable products with high strength and high quality. The strength of China’s UHMWPE products can reach 38CN/dtex, but still far below high-strength products. The second direction is to develop creep-resistance products. Netherland DSM has developed Dyneema DM20 – an extremely low creep fiber. Chinese producers are speeding up its space in R&D on creep-resistance fiber. The third direction is to develop high-grade cutting-resistance products. Such products have been put into commercial production but the production stability is yet to improve. The fourth direction is to develop serialized coloured yarn. Chinese producers have developed coloured fiber as a solution to weak UHMWPE fiber dyeing performance. However, the categories are not enough to cover standard color or make coloured yarn serialized. The fifth direction is to develop modification products. The R&D on fine denier fiber and profiled fiber will meet civil demand for comfortable textile; composite technology and processing technology are used to modify product performance and enhance materials strength. The sixth direction is to develop low-cost production technologies. Continuous upgrading of technologies and energy saving will help reduce production cost.
There are two ways for domestic producers to achieve coordinative development trend along the UHMWPE industrial chain. First, producers should collaboratively develop on-purpose raw material for the production of UHMWPE. Domestic producers have to purchase raw materials from the market, as none of them are equipped with raw material production units. Producers should cooperate with upstream suppliers to develop high-quality raw materials specifically applicable to UHMWPE. Secondly, producers should enhance quality of composite materials, as the processing quality of composite materials also affects the quality of UHMWPE products. Accordingly, aligning technologies in the industry and achieving collaborative development of the industrial chain from upstream to downstream facilitate Chinese UHMWPE market to grow faster.
As for the application fields, domestic producers should explore the application in civil summer textile along with its good thermal conductivity; should explore the application in household and industrial textile reinforcing sector along with the high strength; should blend UHMWPE with other special fibers so as to develop high-strength composite materials in new application fields; should replace carbon fiber and para-aramid for the price advantage; should replace nylon and polyester industrial yarn by materials upgrading.
