How much do you know about the stretching laws of stretched films?
Stretch film is oriented at a certain temperature, usually above the glass transition temperature of the polymer, below the melting point of the polymer thick film or sheet along its plane, two directions of longitudinal and horizontal directions, so that the macromolecular chains are oriented. The stretching temperature of the amorphous polymer should be between the glass transition temperature and the melting point of the polymer, that is, the polymer is in the viscoelastic state. The stretching orientation of the crystalline polymer is usually carried out at an appropriate temperature above the glass transition temperature of the polymer. The process of stretching orientation of the substance is essentially the deformation process of spherulites. The stretching orientation of the crystalline polymer is mainly to form a microfilament structure. As a result of the stretching orientation of the polymer, the number of straight segments increases, and the folds The number of chain segments is reduced, thereby improving the mechanical strength and toughness of the polymer material. Therefore, one way to improve the mechanical strength of the oriented polymer is to control the polymer aggregation state structure generated by the liver during processing, so that it generates more straight-chain structures.
The stretching rule of stretch film is as follows:
(1) When the temperature and the stretching speed are constant, the lower the stretching temperature exceeds the glass transition temperature of the material, the greater the orientation effect.
(2) When the temperature and the stretching speed are constant, the greater the stretching ratio, the greater the orientation effect.
(3) When the temperature and the stretching ratio are fixed, the faster the stretching speed, the greater the orientation effect.
(4) Under stretching conditions, the faster the cooling rate, the greater the orientation.
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