Product Properties of Dipped Polyester Cords The properties of polyester cords mostly rely on raw yarns. Besides improving the bonding between polyester cords and rubbers, dipping treatment may adjust heat shrinkage and elongation within certain limits through stretching. The tension of yarns is weakened due to abrasion of machinery and chemical action caused by RFL infiltration. For the cords used for reinforcement material for transmission belts, their large tension, small elongation at certain load, stable heat shrinkage and high adhesion between the cords and rubbers are the major properties as well as the standards to measure the quality of polyester cords. The four major technical elements influencing the quality of the cords are as follows: 1. Twisting processing parameters. 1. Formula and preparation of first and second dipping liquid. 1. Chemical reaction conditions and thermal treatment degrees after dipping through first and second bath, i.e. the dipping process. 1. Design and production of dipping equipment. The raw yarns are twisted and the twist affects the cords’ tension and elongation. To some degree, tension increases as twist increases and falls after an extreme value. The higher is the twist, the larger is the elongation. The formula of RFL and dipping process determines the cords’ adhesion. Visible and invisible elements influence cords’ tension during the whole production. The visible elements are components of twisters and treaters, and the invisible ones are the osmotic quantity of RFL to the cords, etc. It’s noteworthy that these elements are not working separately but interactively. The dipping process includes heat and cold shaping of polyester cords, and the heat shrinkage of polyester make the relationship more complicated. Cords’ heat shrinkage and elongation are correlated. When one quantity is confirmed, the other will be generated automatically. Which one is control quantity is decided by the intended use of the cords. Through stretching, the two quantities can be adjusted within a certain scope. To meet extreme demands, the raw yarn categories must be changed.