Control of Elongation in Highly Stretched Cotton Tire Cord

Abstract

Abstract 1. Cotton tire cords, differing with regard to gauge, construction, and variety of cotton, were subjected to stretching treatments involving various combinations of tension, heat, and moisture. It was found that all these treatments increased the strength of the cords but reduced their gauge and elongation at 10 pounds. The greatest increase in strength was obtained when tire cord was stretched in a swollen condition and in the presence of heat. Increases in count-strength product from 48 to 83 per cent were observed. 2. Experiments showed a reciprocal relationship between the strength and the elongation at 10 pounds obtainable by single-stretching treatments of tire cord, which makes impossible the control of elongation, independently of strength. Bone-dry elongations of about 6 per cent at 10 pounds could be obtained only with negligible increase in strength. 3. The original elongation was restored by treating highly stretched tire cord with water at room temperature for 30 minutes or with boiling water for 3 minutes, while most of the increase in strength resulting from stretching was retained. A hot-wet-stretched tire cord after treating with water had equal elongation but greater strength as compared with the untreated cord. 4. A dual-stretching method was devised which makes possible the control of elongation at 10 pounds independently of strength. The treatment consists of two phases : the first imparts to the cord the maximum potential breaking strength and the second serves to adjust the elongation at 10 pounds to a predetermined controlled value while maintaining over 90 per cent of the maximum count-strength product. Control of the elongation is achieved by proper selection of tension and degree of swelling during the second phase of the dual-stretching treatment.