Quarterly Scientific-Research Goljaam

Symmetric and asymmetric knots, as two original knots, possess different physical and mechanical properties that influence the function of a carpet. Jufti and U knots give different properties to the carpet compared to the original ones. If they were used to produce specific properties, they would enhance the carpet's quality. However, nowadays their applications are considered as methods that diminishes the quality of carpets. As these properties have significant influence on the carpets, some attention is paid to them in different papers and textbooks. Carpet samples are woven with each knot type and identical materials by a weaver. Then the effect of various kinds of knots measured on the carpet length, carpet thickness and pile height. Samples are woven in two different methods. The first one is a method in which the number of beating the comb is controlled; i.e., after each row of knots only and exactly two comb beats are applied to the row of knots. In the second method, the dimensions of samples were controlled and it is tried to weave the carpet with the dimensions designed; i.e., the number of times the comb is beating down the row of knots varies according to the weaving progress. In jufti and U knot samples, the number of beating times inevitably reduced to one, while in symmetric and asymmetric samples it increased to five to six times to obtain the designed dimensions. Results show that symmetric and asymmetric knots lead to an increase in the carpet length, whereas the other two knot types end in a decrease in the carpet length. To reach the designed length it is necessary to change the number of beating or to use different materials with suitable yarn counts. The thickness of the foundation of carpet is also influenced by the knot type; i.e., if the number of comb beating increases the foundation thickness increases as well, but if the number of comb beating remains constant there will be identical foundation thickness in carpets woven with different types of knots. 

In this paper, the specimens woven by the same weaver with identical materials but with four different types of knots, i.e., symmetrical, asymmetrical, jufti and U knots, which their details are given in a previous paper by these authors, are used. The effect of these knots on such physical properties as width of the weave, length of the motifs, length of yarn in a knot and the carpet weight are measured. The woven samples are produced in two different methods. Resulrs show that the width of jufti and U knot samples were reduced after cutting off the loom, while the change in the width of the other two is little. The change in the length of motifs depends on the change in the carpet length, i.e., in samples with change in carpet length, the motifs length change as well and in cases that there are little change or no change in the carpet length, accordingly no change or little change is observed in the motifs. In the meantime, by subjective investigation of shapes of motifs in the four different knots, the change in their details and the sharpness of the lines and curves in them are studied. The results of computation of the ratio of the wool yarn to cotton yarn demonstrates that in symmetric and asymmetric samples more than two third of the carpet weight is built up by wool yarns, so that it is predicted that they have better mechanical function compared with other knots. Jufti sample has the lowest ratio of wool to cotton yarn, so it would show the worst mechanical performance.