By Hu Panwei, China National Chemical Information Center

Polyolefin elastomer (POE) is a random copolymer of ethylene and alpha-olefin produced using metallocene catalyst technology. POE's unique molecular structure makes it excellent in elasticity, fluidity, mechanical properties, corrosion resistance, gas permeability, electrical properties, high/low temperature resistance, UV resistance, and water resistance. 

Domestic POE demand depends entirely on imports

   At present, only Dow Chemical, Mitsui Chemicals, SABIC, LG Chemical, ExxonMobil, and Borealis have capacities to produce POE, and no Chinese companies have such capacity. In the past five years, China’s POE imports have been rising due to the increase in domestic demand. In 2018, the global POE production was about 900 000 tons, and China’s import volume reached about 300 000 tons, accounting for 1/3 of the world’s total production.

   The POE imports in Chinese market are mainly POE (1-butene) and POE (1-octene). POE (1-butene) has more users due to its excellent performance and relatively low price. In recent years, due to the increase in the operating rate of POE (1-octene) lines, the wider range of its applications, and a better performance than POE (1-butene), coupled with China’s downstream products upgrades and their higher requirements on plastic products’ quality and functions, POE (1-octene) products have become the leading POE product in China.

   At present, most POE imports are concentrated in South China and East China. In 2018, Guangdong Province imported 102 000 tons, accounting for 34% of the total imports, followed by Shanghai with imports of 84 000 tons, accounting for 28%, and Jiangsu & Zhejiang, with imports accounting for 22%. The remaining 12 provinces and municipalities took a relatively small proportion of imports.

   In 2018, imported POE mainly included Dow's Engage series, Mitsui Chemical's Tamfer series, SABIC's Fortify series, SK Chemical's Solumer series, LG's Lucene series, ExxonMobil's Exact series, and Borealis' Queo series. The typical grades and production processes of imported POEs are shown in Table 1.

   Table 1   Producers and brands of POE imports in 2018

Domestic POE consumption structure and applications

   POE is a toughening material for general-purpose plastics and engineering plastics. Its downstream sectors include the automobile industry, packaging, foamed materials, the home appliance industry, and wire & cable. In 2018, among POE consumers, the automobile sector accounted for about 50%; the industrial packaging sector 23% (the surge in consumption was mainly because POE was used as major material in solar cell encapsulation film in the past two years), the foaming sector 10%, the wire & cable sector 8%, and others 9%. The POE consumption structure is shown in Figure 1.

   Automobile

   At present, in the automobile industry, POE is usually blended with PP as a toughening agent, or grafted with maleic anhydride (MAH) and then blended with PA66 to form a composite material. Such a composite material is applied to parts of bumpers, fenders, backing plates, steering wheels, and dashboards of automobiles.

   PP has the advantages of low density, high tensile strength, high hardness, high yield strength, and a high heat distortion temperature, and is easy to process and low in price. It is the most widely used material in automotive plastics, accounting for 37%. However, the impact strength of PP material is low, and the low-temperature brittleness is particularly prominent, which limits its application. Blending with elastomer to improve PP impact performance is currently the most widely used method. In the automotive industry, the current widely used blending system is PP, POE and inorganic fillers (CaCO3 and talc). POE modified PA can improve its mechanical properties, flame retardant properties, and electrical properties, enabling PA materials to face increasingly demanding working conditions. However, POE has poor compatibility with PA, and it needs to be grafted with maleic anhydride (MAH) to be used as a raw material to improve the impact toughness of parts.

   Foaming

   As a modifier of EVA foam material, POE is widely used in foaming sandals, the midsoles of foaming sports shoes and sneakers, foaming fitness mats, children's combination toys, foaming cushioning materials and sound absorbing materials. POE can be used alone or in combination with other materials, but since the average unit price of POE is higher than that of EVA, it is generally combined with POE and EVA. The foaming industry basically chooses POE (1-octene) as a modifier because the softness and resilience of the POE (1-octene) modified foamed material are better than that of POE (1-butene).

   Wire & cable

   The substrate of the low-smoke halogen-free flame-retardant polyolefin cable material includes polyethylene (PE), polypropylene (PP), ethylene-vinyl acetate (EVA), ethylene propylene rubber (EPR), etc., and they are composed of resin, flame retardant filler, aluminum hydroxide, magnesium hydroxide, and some antioxidants which can improve the heat-resistant life. Generally, the filling amount of aluminum hydroxide and magnesium hydroxide should be up to 150%, but the filling of a large amount of inorganic flame retardant causes the deterioration of physical and mechanical properties, electrical properties, and extrusion process performance of the cable material. So, it is generally required the POE or ethylene-propylene block copolymer to be modified, grafted, or added with a coupling agent for chemical modification.

   Industrial film/packaging

   Common substrates of the films are PP and PE. PP is widely used in the packaging field thanks to its good film transparency and mechanical properties. However, due to the low temperature and brittleness of PP and PE, their applications in the low temperature field are limited. POE can give PP higher impact resistance, high transparency, high thermal stability, and high cost performance. In the film industry, almost 75% of POEs are used in industrial packaging, and only about 15% are used in food packaging. 

   In recent years, with the continuous development of new energy materials, POE has been widely used in the packaging film of solar cells. As an industrialized packaging film, EVA still faces the problems of decreases in translucency and photoelectric conversion efficiency, yellowing, and cracking caused by unsaturated double bonds, acetic acid, and small amounts of acetaldehyde, ketone, and lactone structures under the action of light, heat, and oxygen. POE can be used as a modifier for EVA or as a packaging film for solar cells, thanks to its good mechanical properties, UV resistance, aging resistance, and rheological properties.

   Because of the excellent performance of POE, in addition to the above fields, it can also be applied in the fields of household appliances, medical plastics, hot melt adhesives, and the like. Its application area is still expanding, and on the back of the continuous development of downstream industries, the average annual growth rate of POE demand is expected to be higher than 10% in the next five years, especially in the fields of automobiles, foaming, wire and cable, and industrial packaging. 

   POE is one of the key development products during the “13th Five-Year Plan” period. The Petrochemical and Chemical Industry Development Plan (2016-2020) (Ministry of Industry and Information Technology [2016] No. 318) includes the development of polyolefin elastomer products in the development of new chemical materials. However, as the metallocene catalyst process is still not mature and the supply of raw materials is still short, it will take some more time to realize the localization of POE.