UHMWPE Fiber Makers Must Upgrade Quality & Cut Costs

By Yang Yong, Hu Ting, Sinopec Yizheng Chemical Fiber Co., Ltd.

China has increased its output of UHMWPE (ultra high molecular weight polyethylene) fiber more than 15% annually in recent years, and the growth exceeded 25% in 2015.

Technology:
gel spinning as the lead

Since the 1970s, quite a few UHMWPE fiber production technologies have appeared, such as high-pressure solid-state extrusion, plasticized melt spinning, surface crystalline growth, zone super stretching and gel spinning. Only plasticized melt spinning and gel spinning have really been commercialized. Fibers produced by plasticized melt spinning are not as good as fibers produced by gel spinning, which has become the major technology used in commercial production.
Gel spinning is classified into dry spinning and wet spinning, based on the different solvents used. Foreign producers mainly use dry spinning. Yizheng Chemical Fiber Co., Ltd. uses the technology today, and that capacity is 28% of China’s UHMWPE fiber capacity.

Market:
wide application space

China’s three most important products incorporating UHMWPE fiber are bulletproof/protective products, cables/rope nets and cut-resistant gloves. The makers of dry spun fibers have gradually developed special–characteristic fibers for textiles in recent years and hence gained very strong competitive advantages in the civilian marketplace.

1. Bulletproof/protective products

Bulletproofing and other protection is the most important application of UHMWPE fiber in the military sector. This includes bulletproofing and stab resistance. Weftless cloth made of UHMWPE fiber has been developed well for both bulletproofing and stab resistance. In addition to satisfying the needs of China’s soldiers and policemen, some products are also exported. Dry spun fibers have fine titer, great softness and high strength.

2. Cables/rope nets

The major application of UHMWPE fiber in cables is mooring lines for ocean-going ships and marine engineering. UHMWPE fiber cables are gradually replacing steel cables and nylon ropes in traditional fields such as job ropes, tow ropes and hoisting ropes.
UHMWPE fiber has low weight, high strength, biting resistance, abrasion resistance and mildew resistance. It can be used in breeding nets/cabinets and fishing nets to increase breeding density and prevent the killing of commercial fish by predatory fish. In this way the productivity and financial benefits of fishery can be remarkably enhanced.
UHMWPE fiber can also be used in other kinds of nets such as ball-guard nets in golf training courses. Compared with traditional polyester nets, aviation cargo nets made of UHMWPE fiber are 50% lighter, and their service life is 60% longer. In this way the maintenance costs of airlines can be reduced.

3. Cut-resistant gloves

Cut-resistant gloves are produced by braiding or cladding other fibers with UHMWPE filament yarn – fibers such as polyester fiber, nylon, polyurethane fiber, glass fiber or steel wire. Due to requirements such as slippage resistance and humidity resistance, and the particular environments where products are used, dipping and shaping are also needed. Electro-conducting fibers can also be woven into the gloves to get antistatic cutting-resistant gloves.

4. Textile fabrics

The thermal conductivity of UHMWPE fiber is four times that of polyester fiber. Wet spun fiber also features moisture conductivity. Products made of its filament and staple yarns are already used in making clothes and home textiles with requirements for coolness.

5. Other uses

As UHMWPE fiber has high specific strength and specific modulus and excellent toughness and impact resistance, it has extensive applications or development potential in sports/athletics, reinforcing materials, thin-wall pressure-resistant materials and medical materials. Moreover, it features negative expansion (expanding with the reduction of temperature) and a low friction coefficient. It therefore has unique applications in low temperature environments.

Future: focus on fine–denier fibers and environmental protection, upgrade quality
and cut costs

UHMWPE fiber has been developed rapidly ever since the commercial production. Still, the global supply is short.
With the maturity of production technologies, the production cost of UHMWPE fiber declines constantly. UHMWPE fiber is also increasingly accepted by civil sectors, driving demand growth. Table 1 shows China’s applications of UHMWPE fiber in the last five years. Fine denier is the key to developing civil products. Fine denier can help increase the strength and modulus of products. Softness and moisture conductivity of dry spun fibers can make products more comfortable. Dry spun fibers with fine denier will be the primary orientation in product development and technology modification.
Table 2 shows the development of UHMWPE fiber in China in the last five years. Applications of UHMWPE fiber have expanded constantly in China, but with intense market competition, the high-profit era is already gone. Upgrading quality and reducing costs will both be emphasized in the future development of technologies.         

Table 1  Application distribution of UHMWPE fiber in China, 2011-2015  (ton)

    2011    2012    2013    2014    2015
Gloves    1 200    1 400    1 650    1 860    2 420
Bulletproof products    1 080    1 350    1 510    1 600    1 900
Rope nets    280    500    745    1 000    1 070
Others    10    65    100    140    180


Table 2    Production & consumption of UHMWPE fiber in China, 2011-2015  (ton)

    2011    2012    2013    2014    2015
Capacity (t/a)    8 480    8 880    9 530    9 530    10 500
Output    4 000    4 860    5 620    6 500    8 160
Import volume    360    355    385    300    290
Export volume    1 800    1 900    2 000    2 200    2 880
Apparent consumption    2 560    3 315    4 005    4 600    5 570