Complex sentence: Astronlon-C a polyamide yarn and Astralene-C a polyester yarn when made into clothing were irritable to the skin and companies had been trying for some time to find a artificial yarn alternative.
Split into simpler sentences: Astronlon-C, a polyamide yarn, and Astralene-C, a polyester yarn, were irritable to the skin when made into clothing. Companies had been trying for some time to find a artificial yarn alternative.