Lubricant is to be able to improve plastic processing flow properties of a kind of additive, its structure generally has a long chain of nonpolar and polar group two parts, in addition to improve the melt flow, it also has promotes molten, easy stripping, prevent electrostatic, prevent adhesion effect, according to the mechanism can be divided into external lubricant and lubricant in two.










(1) action mechanism of external lubricant.










Improve the friction between plastic melt and metal surface of molding equipment, reduce the friction between the two, so that plastic parts easy to demould. The compatibility of external lubricant and plastic is poor, and it is easy to migrate from the melt to the outside, thus forming a very thin isolation film between the melt and the mold to avoid the plastic melt sticking to the cylinder or the surface of the mold.










(2) action mechanism of internal lubricant.










Internal lubricant has good compatibility with plastic, it plays a role in reducing intermolecular cohesion in plastic melt, can reduce the internal friction of plastic melt, increase the melt rate and melt deformation of plastic, reduce melt viscosity and improve plasticizing performance.










Most lubricants are both inside and outside the function of the lubricant, but some lubrication, on some outside on lubrication, and the same kind of lubricant in different plastic or under different processing conditions will show different lubrication, it is commonly believed, has good compatibility with plastic, polar groups polarity of lubricants used as lubricant inside; Otherwise, it is used as external lubricant. Among them, if the plastic fluidity has been able to meet the needs of the molding process, the main consideration is whether the lubricant meets the process requirements, whether it is convenient to demould, to ensure the balance of inside and outside. When selecting external lubricant, it should be noted that its melting point should be close to the molding temperature, but there should be a difference of 10~30℃, so as to form a complete isolation film on the plastic surface.