Polyethylene fiber (PE fiber) refers to the fiber material obtained by spinning polyethylene by melt spinning, including short fibers and filaments. The mechanical strength of this fiber can be adjusted by spinning process parameters, and the wet strength and elongation are the same as those in the dry state. Polyethylene fiber has the advantages of high strength, low density, and good insulation, but its low heat bearing capacity and cold creep limit its application. It is mainly used to produce various industrial textiles, especially filter materials, tarpaulins, mesh belts and other products.

Introduction

Polyethylene fiber has a crystallinity of г╛85%, orthorhombic system, a density of 0.95бл0.96g/cm3, a melting temperature of 124бл138бц, a glass transition temperature of -75бл-120бц, and fiber properties are divided into ordinary type and high-strength high-model. The ordinary fiber has a strength of 4.4бл7.9cN/dtex, a modulus of 31бл88.3cN/dtex, and an elongation at break of 8%бл35%.

Process route

Internationally, there are two different production process routes for high-performance polyethylene fibers: one is the high-volatility solvent (decahydronaphthalene) dry gel spinning process route represented by Dyneema (referred to as the dry process route), and the other is the low-volatility solvent (mineral oil, white oil, etc.) wet gel spinning process route represented by Spectra (referred to as the wet process route).

Dry process route

Using high-volatility decahydronaphthalene as solvent and ultra-high molecular weight polyethylene powder as raw material, high-performance polyethylene fibers are produced by integrating the freeze-gel dry spinning б· super-multiple hot stretching б· solvent recovery system. After the spinning stock solution is extruded from the spinneret, the decahydronaphthalene is vaporized and escaped to obtain dry gel precursor, which is then stretched to obtain high-performance polyethylene fibers.

Wet route

Ultra-high molecular weight polyethylene spinning solution is prepared with low-volatile substances such as mineral oil and white oil as solvents. The spinning solution is extruded from the spinneret hole and then enters a water bath (or a mixed bath of water and ethylene glycol, etc.) to solidify to obtain wet gel precursor containing low-volatile solvent. The wet gel precursor is extracted with an extractant (freon or other reagent) with high volatility and excellent extraction performance through a continuous extraction device in multiple stages. The extractant replaced in the gel precursor is fully vaporized and escaped through a continuous multi-stage drying device to obtain a dry gel precursor, which is stretched to obtain high-performance polyethylene fiber.

Process route evaluation

Compared with the wet route, the dry route has the advantages of short process flow, good product quality, low production cost, direct solvent recovery, closed integration of spinning and solvent recovery systems, and economic and environmental protection. At present, the dry process route accounts for 80% of the existing high-performance polyethylene production capacity, becoming the dominant process in production and the development direction of high-performance polyethylene fiber industrialization. In the dry process, since decalin solvent allows a higher stock solution concentration and the spinning speed is much higher than that of the wet process, the solvent can be directly recovered without the need to consume a large amount of extractant and undergo a complex and energy-consuming multi-pass extraction and drying, and a large amount of mixed reagent distillation separation and recovery process, thereby reducing production costs.

The wet process route requires the consumption of a large amount of extractant and undergoes multiple extraction, drying, mixed reagent distillation separation and recovery processes, which is easy to cause environmental pollution. The extractant currently used is Freon, which may be banned due to its destructive effect on the atmosphere. In the dry process, the solvent decalin has no other toxicity except irritation, and is safe to use. It is an ideal industrial reagent. The dry process meets the requirements of sustainable development and clean production.

Fiber properties

(1) The fiber strength and elongation are close to those of polypropylene

(2) The moisture absorption capacity is similar to that of polypropylene, and the regain is 0 under normal atmospheric conditions.

(3) It has relatively stable chemical properties and good chemical resistance and corrosion resistance.

(4) Poor heat resistance, but good resistance to moisture and heat. Its melting point is 110-120бц, which is lower than other fibers, and its resistance to melt holes is very poor.

(5) Good electrical insulation. Poor light resistance, easy to age under light.

Application and performance

Poor wearing performance of ethylene, but its price is low. It is suitable for making bristle, flat or split fiber, used to make ropes, filter cloth, packaging cloth, etc.

Linear

Linear polyethylene is generally made by directional polymerization at normal pressure using Al(C2H5)3-TiCl3 as a catalyst. The former uses melt spinning method for fiber forming, and the latter uses ultra-high molecular weight polyethylene as raw material, using gel spinning method or super stretching method. Solvents include decahydronaphthalene, paraffin oil, paraffin and kerosene. Fiber uses, the former is used to make ropes, fishing nets, filter cloths and packaging bags; the latter is used to make bulletproof clothing and bulletproof products, cut-resistant fabrics, cables and fishing nets.

Synthetic fibers composed of linear molecules of unsubstituted saturated aliphatic hydrocarbons formed by polyethylene.

PE

Polyethylene (PE) is the most commonly used plastic polymer in the world, with an annual consumption rate of more than 50 billion pounds per year. More than 70% of Porex products use polyethylene. With a repeating linear molecular structure иCCH2-CH2- as the unit, PE is a semi-crystalline polymer whose toughness is enhanced before breaking under tension. Generally speaking, PE is a strong, lightweight thermoplastic material with excellent chemical resistance. The pore diameter of products produced using standard polyethylene grades is usually 7 to 150 microns, but these nominal values can be increased to 300 microns through special blends.

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