A process for making a closed functional unit of a device, wherein the device is selected from the group consisting of fuel cells; heat exchangers; and chemical reactors of electrolysis cells, batteries, dialysers, or contactors, and wherein the closed functional unit contains at least one elastomer sealing element, comprising the steps: (i) providing at least two components of the functional unit, which are to be bound by one or more sealing elements; (ii) applying a reactive liquid or paste-like composition, which can be cured into an elastomer by cross-linking, to at least one of the components of step (i); (iii) performing a series of steps or: series of steps complete or partial drying and/or partial curing of the reactive liquid or paste-like composition applied onto the component(s) of step (ii) to obtain one or more precursor(s) for (a) sealing element(s), which are self-adhesively bound to the component(s); contacting the component(s) of step with the component(s) to be bound; (AIII)curing of the precursor(s) of (a) sealing element(s) on the component(s) of step, wherein an eleastomer is obtained, to obtain one or more sealing element(s) that are self-adhesively bound to the component(s); series of steps curing of the reactive liquid or paste-like composition applied to the component(s) of step (ii) after the removal of solvent, wherein an elastomer is produced, to obtain one or more sealing element(s) that are self-adhesively bound to the component(s); and contacting the component(s) of step with the component(s) to be bound; and (iv) obtaining the closed functional unit; wherein the reactive liquid or paste-like composition contains one or more polymers selected from the group consisting of fluorinated carbon polymers capable of being cross-linked into elastomers; and the reactive liquid or paste-like composition is applied continually, in a pathcontrolled manner, or in a jet process in a path- or matrix-controlled manner discontinually in a dot matrix by compressed air or pumps by means of a dispensing tip or spray nozzle. (i) providing at least two components of the functional unit, which are to be bound by one or more sealing elements; (ii) applying a reactive liquid or paste-like composition, which can be cured into an elastomer by cross-linking, to at least one of the components of step (i); (iii) performing a series of steps or: series of steps complete or partial drying and/or partial curing of the reactive liquid or paste-like composition applied onto the component(s) of step (ii) to obtain one or more precursor(s) for (a) sealing element(s), which are self-adhesively bound to the component(s); contacting the component(s) of step with the component(s) to be bound; (AIII)curing of the precursor(s) of (a) sealing element(s) on the component(s) of step, wherein an eleastomer is obtained, to obtain one or more sealing element(s) that are self-adhesively bound to the component(s); series of steps curing of the reactive liquid or paste-like composition applied to the component(s) of step (ii) after the removal of solvent, wherein an elastomer is produced, to obtain one or more sealing element(s) that are self-adhesively bound to the component(s); and contacting the component(s) of step with the component(s) to be bound; and series of steps complete or partial drying and/or partial curing of the reactive liquid or paste-like composition applied onto the component(s) of step (ii) to obtain one or more precursor(s) for (a) sealing element(s), which are self-adhesively bound to the component(s); contacting the component(s) of step with the component(s) to be bound; (AIII)curing of the precursor(s) of (a) sealing element(s) on the component(s) of step, wherein an eleastomer is obtained, to obtain one or more sealing element(s) that are self-adhesively bound to the component(s); complete or partial drying and/or partial curing of the reactive liquid or paste-like composition applied onto the component(s) of step (ii) to obtain one or more precursor(s) for (a) sealing element(s), which are self-adhesively bound to the component(s); contacting the component(s) of step with the component(s) to be bound; (AIII)curing of the precursor(s) of (a) sealing element(s) on the component(s) of step, wherein an eleastomer is obtained, to obtain one or more sealing element(s) that are self-adhesively bound to the component(s); series of steps curing of the reactive liquid or paste-like composition applied to the component(s) of step (ii) after the removal of solvent, wherein an elastomer is produced, to obtain one or more sealing element(s) that are self-adhesively bound to the component(s); and contacting the component(s) of step with the component(s) to be bound; and curing of the reactive liquid or paste-like composition applied to the component(s) of step (ii) after the removal of solvent, wherein an elastomer is produced, to obtain one or more sealing element(s) that are self-adhesively bound to the component(s); and contacting the component(s) of step with the component(s) to be bound; and (iv) obtaining the closed functional unit; wherein