Introduction of resins commonly used in film production-polyester (PET)-technical knowledge

Introduction of commonly used resins in film production-polyester (PET) Source: Protective film factory direct sales Release time: 2019-03-03 Hits: 2580 Today, the editor of polyva brings you some basic introductions of PET, welcome everyone to consult our company's production PET film! Polyester, English Polyethylene terephthalate, abbreviated as PET, mainly refers to polyethylene terephthalate, is a high molecular compound formed by the condensation of dibasic or polybasic acid and dibasic or polyhydric alcohol, with p-benzoic acid (PTA) and Polyethylene terephthalate, which is formed by polycondensation of ethylene glycol (EG) as raw material, is the world's first to realize industrialized production and is widely used in polyester products. It is also the world's most widely used and most widely used polymer. One of the materials. The film produced by PET is a relatively comprehensive plastic film. It has good transparency and luster; has good air tightness and fragrance retention; moderate moisture resistance. PET film has excellent mechanical properties, good toughness, tensile strength and impact strength; and has good stiffness, stable performance, and is suitable for secondary processing such as printing and paper bags. PET film also has excellent heat resistance, cold resistance, good chemical resistance and oil resistance, so it is widely processed into films, sheets and other polyester products, which are used in food packaging, optical base film, medical packaging, electrical engineering Products, etc. Polyester temperature performance Polyester needs to go through two key temperature points from solid to molten liquid at room temperature, namely glass temperature (Tg) and melting temperature (Tm). The glass temperature of polyester is about 67°C, at which time the polyester changes from a highly elastic state to a glass state. The melting temperature of the polyester is about 267°C, at which time the polyester changes from a solid state to a molten state. Because the polyester is a semi-crystalline polymer, the polyester has a crystallization temperature of about 160°C. At this time, due to the heating of the polyester, the interaction between the molecular chains increases, and the molecular chains are rearranged under the interaction to form a ball. Crystal, polyester cannot be crystallized completely, and its maximum crystallinity is 55%. In addition, some important physical properties of polyester are: the heat distortion temperature (1.8MPa) is about 224°C, and the temperature at the maximum crystallization rate is about 190°C. Polyester crystalline morphology structure Polyester crystallization behavior mainly occurs above the glass transition temperature and below the melting point temperature. Polyester can only be partially crystallized. Crystalline and amorphous regions exist at the same time. Each molecular chain runs through many crystalline and amorphous regions. . Moreover, in the amorphous region, the molecular chains are coiled and entangled with each other. The crystalline morphology structure of polyester is multi-layered. It mainly includes amorphous state, lamellae (5nm-10nm), spherulites (0.2um-0.5um), molecular chain orientation and crystal orientation.