Aliphatic polyketone (POK) resin is a high-performance thermoplastic polymer. It is a linear crystalline polymer obtained by alternating copolymerization of carbon monoxide and ethylene. By adding propylene during copolymerization process, a terpolymer polyketone material (POK-ep) with a lower melting point and easier processing can be obtained. Its structural diagram is shown in figure below.

 

POK structural formula
POK consumes a large amount of carbon monoxide during synthesis process. For every 50,000 tons of POK produced, weight of carbon monoxide consumed is 25,000 tons, which is equivalent to purification effect of 3.8 million pine trees for 5 years. Therefore, vigorously developing POK production and application is in line with the green and sustainable development strategy.

 

Schematic diagram of polymerization of POK materials

POK has unique physical and chemical properties, good temperature resistance, acid and alkali corrosion resistance, gas barrier properties, as well as good wear resistance, high tensile strength and impact strength. POK's good flexibility meets its processing requirements in industrial applications. Its Vicat softening temperature can reach 180℃ and its heat distortion temperature can reach 210℃, which determines that POK has a high upper temperature limit for use.

 

Schematic diagram of structure of aliphatic polyketone (a) α crystal and (b) β crystal
POK has a regular molecular chain and is a crystalline polymer material. Current research has found that POK has two crystal structures, α and β (see picture above). In α crystal form, A=6.91, B=5.12, C=7.60, and crystal density is 1.382g/cm3. In β crystal form, A=7.97, B=4.76, C=7.57, and crystal density is 1.297g/cm3.
As propylene content increases during POK synthesis process, crystallinity and melting point of POK decrease, and crystals are more inclined to form β crystal form. When molar ratio of propylene in POK is greater than 2.9%, POK polymer only shows existence of β phase. Different reaction conditions are used during synthesis process, synthesized POK exhibits different structures and properties.
If amount of propylene during polymerization is more than twice that of ethylene, synthesized POK will exhibit properties of an amorphous low molecular weight polymer; and when amount of propylene during polymerization is less than twice that of ethylene, synthesized POK is a crystalline thermoplastic polymer. Therefore, POK thermoplastic crystalline plastics or POK elastomers with large structural differences can be obtained by adjusting proportion of reaction raw materials.
As crystallinity increases, barrier properties of POK increase, therefore, high crystallinity POK can be used in packaging or industrial pipes.

POK polymer was first obtained by DuPont in the 1940s through free radical polymerization using peroxide as an initiator. Due to inability to control strictly alternating chemical structure of ethylene and carbon monoxide during synthesis reaction, random or partial block copolymer structures are prone to occur. Obtained POK material has low molecular chain regularity, is almost non-crystallizable, and has poor mechanical properties. At the same time, synthesis process is complex and reaction conditions are harsh. Therefore, POK produced by DuPont has no practical value.
In 1952, Brubaker also used free radical polymerization to prepare POK. Resulting POK had a random copolymer structure, so it also had problems such as non-crystallization and low mechanical properties, and could not be put into use.
In the 1980s, researchers from Shell, represented by Drent, used palladium-phosphine coordination compounds as catalysts in presence of strong acid to catalyze copolymerization of carbon monoxide and ethylene, leading to a breakthrough in research and application of polyketones.
Shell Chemical launched Carilon thermoplastic polymer in the United States in 1996. Production was discontinued in 2001 due to various reasons, and its production patent was acquired by Hyosung Chemical. South Korea's Hyosung announced that it would be put into production in 2015 and now has a variety of commercial brands.

 

POKETONE

By mixing POK with other polymers, composite materials with various excellent properties can be obtained. If blended with PP, due to poor compatibility, a sea-island structure is formed, but bonding force between the two phases is strong and crystallization rate of the two components is reduced, making composite material practical.
Zuiderduin et al. systematically studied effect of adding rubber to POK materials on composite materials, and prepared composite materials with good toughness such as polyketone/ethylene propylene rubber.
POK materials and polyamide materials can be mixed together to achieve good interface contact and prepare composite materials with good performance.
In addition, POK can be combined with other fillers to improve performance or reduce overall material costs. Such as precipitated calcium carbonate particles, chopped glass fiber reinforcement, acid anhydride, graphene, PVDF, etc.

Since main chain of POK material molecule has a carbonyl group, new functional groups can be introduced as side chain parts through nucleophilic addition, such as reduction to hydroxyl groups, ketals, thiols, methylene, cyanohydrins, etc., polyketone materials with various physical properties are prepared.
Chemical modification of POK materials using diamines (such as 1,2-diamino-propane) is a simple method to prepare polyamines, and resulting materials can be used as surfactants. And after testing, average particle size of nanoemulsion prepared by this method is about 50nm, and it has high stability for up to one month. In addition, POK can be used as a grafting agent for multi-walled carbon nanotubes (MWNT) after amidation reaction. Biological properties of polyamines synthesized through POK modification have attracted attention of academic community.
Diels-Alder reaction can occur between furan-modified POK materials and 1,1 (diphenylene) bismaleimide to obtain a cross-linked network. Due to addition reversibility of this Diels-Alder reaction, resulting cross-linked network behaves as thermosetting, and can return to thermoplasticity upon continued heating. Material can be cross-linked at 50℃ and can be re-cross-linked at temperatures above 110℃. Results show that material has good reversibility and maintains good mechanical properties through DMA and DSC analysis.
In the field of industrial adhesives, functional materials chemically modified from POK materials are also widely used. Application of POK emulsions in adhesive industry has been studied at industrial level in the early days.
In addition, modified POK can be successfully combined with natural products, giving glue more prominent environmentally friendly properties and better adhesive properties.

Polyketones have excellent properties and can be used in a wide range of applications. Coatings, inks and automobile manufacturing are their main demand ends.
In the field of coatings, polyketones have excellent compatibility with coating solvents and resins, and can improve coating hardness, adhesion, weather resistance and color;
In the field of inks, polyketones can improve quick drying, leveling and glossiness of inks, and can be used to produce alcohol-based inks, gravure inks, flexographic inks, ballpoint pen inks, etc.;
In the field of automobile manufacturing, polyketones can be used to produce automobile wear-resistant parts, including under-hood covers, fuel filler necks, end channels, etc.
Major global polyketone manufacturers include South Korea's Hyosung, Germany's BASF, Solvay, etc. South Korea's Hyosung Group is the world's largest polyketone manufacturer and occupies a dominant position in China's market. Currently, Chinese companies do not have capacity to produce polyketones on a large scale.
POKETONE is an alternating copolymerized polymer material of carbon monoxide and enejing, also known as aliphatic polyketone
As of July 2021, there is still only one company in the world, South Korea's Hyosung, that produces POK products.
Main grades and performance applications of POK

02 POK market is small and consumption is concentrated in China.
POK has only one 50,000-ton/year production unit from South Korea's Hyosung in the world. According to Longzhong Consulting, unit's operating rate is low and its annual output is between 10,000 and 20,000 tons/year. Main consumption areas are in China, the United States and Europe.
Distribution of POK’s main consumption areas

 

At present, Hyosung adopts a parallel approach of agent sales and direct sales in China. It has two main agents in Shanghai and Shenzhen respectively. Ultra-high viscosity extrusion grade POK is sold directly by Hyosung China.
Domestic POK applications are mainly used in production of aerosol valves to replace PA6. The largest domestic user is Zhongshan Meijiesi Packaging Products Co., Ltd.; POK can also be used in production of water purifiers and shower heads. Since POM has possibility of precipitating formaldehyde, POK has certain advantages in parts that come into contact with drinking water, and downstream companies are mainly concentrated in Xiamen. POK is also used to produce injection molded products such as toys, dolls, lipstick tubes, and cosmetic bottles. In the field of oil extraction, ultra-high viscosity extrusion grade POK can currently replace part of ultra-high molecular weight polyethylene for production of oil production pipes and other products.
Main downstream applications of POK