Polyketones at the edge of new developments
Recently, Shell Chemical has introduced various commercial grades of polyketones to the engineering thermoplastic market, naming these semi-crystalline materials as Carilon polymers.What's great about...
Recently, Shell Chemical has introduced various commercial grades of polyketones to the engineering thermoplastic market, naming these semi-crystalline materials as Carilon polymers.
What’s great about Carilon? Its chemical structure and starting materials. When ethylene gas and carbon monoxide are combined over a catalyst, the result is polyketone, a highly crystalline polymer. Shell researchers threw some propylene into it and made a semicrystalline terpolymer, Carilon.
Lets not forget ETPs are 5-10 times costlier than commodity resins. But you get what you pay for. The good news is that Carilon will be much less costly in the future because of its simple chemistry and cheap source of raw materials.
The next obvious question is what Carilon can do? A major advantage of this polymer over other condensation polymers such as nylons and polyesters is its hydrolytic stability. If one wants to make a tiny gear wheel, a bearing or a connector, Carilon provides not only wear and endurance but also elasticity and moisture resistance. For making two 30 mm gears in the Optra S laser printer, Lexmark of Lexington, KY, has substituted an expensive lubricated grade of acetal with non-lubricated Carilon. Nalge Nunc International (NNI) of Rochester, NY now uses a 15% glass-filled Carilon for their unwire test tube rack. Previously, they utilized a glass-filled acetal, which gave out formaldehyde fumes during sterilization process.
An auto part is no good if the part dissolves in gasoline. Carilon’s fuel resistance characteristics pose a threat to nylons 11 & 12 and acetals. Furthermore, this property removes the necessity of an EVOH layer and tie layer in coextrusion blow moulded fuel tanks. Most importantly, the polymer can be processed by conventional extrusion, injection and blow molding machines.
No material is perfect and polyketones are no exception. For demanding conditions at low temperature, toughening is required. Also, they are susceptible to UV degradation. Nevertheless, these properties compare well with other existing engineering plastics.
What’s next? Polyketones will see increasing usage in packaging applications where resistance to aggressive chemicals and low permeability to oxygen, aromas and flavors are prerequisite. The day is not far away when polyketones polar nature will be exploited for bonding to other plastics to produce multi-layer packaging. Injection moldable monolayer fuel tanks made of Carilon are a distinct possibility. Already, developments of blends and alloys with polyketones are under development. Blends with LLDPE have enhanced oxygen barrier properties while blends with PVC have resulted in higher softening temperature.
(Circle Reader Service No. 98)
By Dr. Prithu Mukhopadhyay, director, Society of Plastics Engineers, Quebec Section. Prithu can be reached at firstname.lastname@example.org