Many mobile consumer electronic devices use rubber jacketed cables to connect the earpiece with the cell phone or encapsulate devices in a rubberized case for monitoring body functions during daily routine or workouts. Such rubber parts need to be compatible with a variety of personal care products which are used by consumers.
A number of consumers returned their earbud cables to the manufacturer complaining of discoloration and wrinkling of the jacket and separation of the jacket from the end connectors.
The Field Return and Exemplar cable jackets were separated from the assembly and extracted with methylene chloride. The amounts of extractable organic compounds were determined gravimetrically and the chemical compositions of the extractables characterized by gas chromatography – mass spectroscopy (GC-MS).
The hydrocarbon based rubber jacket swelled during solvent extraction. While the Field Return samples had 39-40 wt-% extractable material, the Exemplar samples had a lower level (29-33 wt-%) of residue remaining after solvent evaporation.
The total ion chromatograms (TIC) of the direct injection GC-MS analyses of the Field Return and Exemplar solvent extracts are shown in the figure.
The Field Return sample solvent extract has more peaks in the chromatogram than the Exemplar extract.
The Field Return extract contains an admixture of individual long chain carboxylic acids, alkanes and alkenes (or cyclic alkanes). Squalene is the major single compound detected. The isopropyl esters of the C14 and C16 carboxylic acids, UV screens (oxybenzone salicylate ester and cinnamate ester) and phthalate/adipate esters (diethylphthalate, butyl benzyl phthalate, mono-2-ethylhexylphthate, bis-2-ethylhexyladipate) are also detected.
The GCMS results suggests that the ingredients common to many skin lotions have been detected in the Field Return samples which are not present in the exemplar sample.
Conclusion and Benefit to the Customer
The ingredients from personal care products used by the consumer infused into the rubber which led to discoloration and loss of mechanical properties. The manufacturer established a material selection criterion based on chemical compatibility and switched to a superior product for the application.