Seals Without PFAS, Lub­ric­ated with Water

From ship pro­pellers to wind tur­bine and har­vesters, seals are cru­cial to ensur­ing func­tion­al­ity in any tech­nic­al sys­tem with mov­ing parts. To increase their dur­ab­il­ity, they have mainly been made from plastics that con­tain PFAS, main­tained with pet­ro­leum-based lub­ric­ants. That is true across the many dif­fer­ent places where they are used, from power plants to motor vehicles. Defects and dam­age there­fore not only cause eco­nom­ic harm but can also have sub­stan­tial envir­on­ment­al impact because the lub­ric­ants and chem­ic­als enter the environment.

“Known as ​‘forever chem­ic­als,’ per- and poly­fluoroal­kyl sub­stances, or PFAS for short, accu­mu­late in the envir­on­ment, can­not be broken down and also pose health risks. The upcom­ing ban in the EU is put­ting the industry in an even tight­er spot. On top of that, about a mil­lion met­ric tons of lub­ric­ants con­tain­ing pet­ro­leum are used in Ger­many alone each year. A single liter can con­tam­in­ate as much as a mil­lion liters of ground­wa­ter. And that res­ults in oily soils, con­tam­in­ated foods and des­troyed eco­sys­tems. We set out to find a solu­tion that addresses all of these chal­lenges togeth­er,” explains Mat­thi­as Trenn, head of the Sur­face Struc­tur­ing team at the Fraunhofer Insti­tute for Laser Tech­no­logy ILT.

For­ward-look­ing seals that bene­fit the environment

The pro­ject was a com­plete suc­cess: With fund­ing from the Fraunhofer-Zukun­ftss­tif­tung (Fraunhofer Future Found­a­tion), research­ers at the Fraunhofer Insti­tute for Laser Tech­no­logy ILT and the Fraunhofer Insti­tute for Mech­an­ics of Mater­i­als IWM teamed up in the pure­Wa­ter­Seal pro­ject to devel­op for­ward-look­ing seals that are not only PFAS free, but are also suit­able for water-based lubricants.

To accom­plish this, the experts from Fraunhofer IWM, led by Manuel Mee, head of the Tri­bolo­gic­al Coat­ings team, developed dia­mond-like car­bon (DLC) coat­ings designed for PFAS-free plastic com­pon­ents. In com­bin­a­tion with laser struc­tur­ing from Fraunhofer ILT, the research­ers delib­er­ately reduce intern­al ten­sion and mech­an­ic­al load­ing — not equally every­where but loc­ally at indi­vidu­al points instead. This main­tains the struc­tur­al integ­rity of the coat­ing while optim­iz­ing its func­tion­al prop­er­ties, such as res­ist­ance to wear and reduced fric­tion. The seals have sig­ni­fic­antly longer lifespans as a res­ult. Com­bin­ing the coat­ing and micro­struc­tur­ing also makes it pos­sible to use water-based lub­ric­ants, which was pre­vi­ously not feasible.

“The devel­op­ment of the seals is an import­ant step in advan­cing eco­friendly pro­duc­tion meth­ods since PFAS enters the envir­on­ment primar­ily dur­ing man­u­fac­tur­ing and not as much in applic­a­tion. We are pro­tect­ing resources and eco­sys­tems by using exclus­ively non-harm­ful sub­stances. At the same time, our seals are an optim­um fit for even soph­ist­ic­ated func­tion­al chal­lenges,” says Chris­tof Koplin, head of the Poly­mer Tri­bology and Bio­med­ic­al Mater­i­als team at Fraunhofer IWM.

Togeth­er for fast implementation

The Fraunhofer spe­cial­ists are work­ing closely with part­ner com­pan­ies focus­ing on dif­fer­ent applic­a­tions to ensure that their solu­tion makes its way into indus­tri­al prac­tice quickly, suc­cess­fully and on the broad­est pos­sible basis. Ini­tial pro­to­types are already in use in pumps at geo­therm­al power plants. Now the goal is to trans­fer the pro­cess to lar­ger facil­it­ies and sys­tems and move into series pro­duc­tion. At the same time, the research sci­ent­ists are optim­iz­ing their seals on an ongo­ing basis, tar­get­ing dif­fer­ent areas of applic­a­tion and cus­tom­er needs. Plans for a spin-off that mar­kets these devel­op­ments are already in the pipeline.