????The stretching production of PVC film is carried out on the calender production line or on a special stretching machine. The stretching methods are unidirectional stretching and bidirectional stretching. Unidirectional stretching refers to stretching the film in the longitudinal or transverse direction, and bidirectional stretching refers to stretching the film in both the longitudinal and transverse directions.
????Unidirectionally stretched PVC film is currently widely used in the calender production line. The method is to peel the polyvinyl chloride film blank formed on the roller of the calender, and peel it from the surface of the roller, and then introduce it into the tenter (at this time, the temperature of the film blank is above the glass transition temperature and below the melting temperature). The running conveyor belt is clamped up and down. As the horizontal running distance of the conveyor belt at both ends of the film blank is gradually increased, the film blank clamped by the conveyor belt is laterally widened and wound up after cooling and shaping. This method of producing a film blank with a roller with a small working surface size and then stretching to produce a wide film is both economical and convenient.
????Film blanks that can be unidirectionally stretched include polypropylene films, high density polyethylene films, and polyvinyl chloride films. Bidirectional pick-up film is generally carried out on a special stretching machine. The stretched film blank is first introduced into a longitudinal pick-up roller composed of multiple rollers. The roller body is heated by steam, and the pvc transparent film is pulled forward by the roller to run forward.