Polyethylene naphthalate plastic

1. Introduction to polynaphthalene ethylene glycol plastic
The structure and properties of polyethylene naphthalate (PEN) are very similar to those of PET, as long as the benzene ring in the PET structure is replaced with a naphthalene ring.
2. Structural performance
PEN has a similar structure to PET, so it also has similar properties, but because the naphthalene in PEN is larger than the benzene ring in PET, the molecular chain of PEN is more rigid, and it has better mechanical, electrical, chemical, heat resistance and barrier properties than PET.
PEN has a large molecular building block, and its crystallization rate is only one-seventh of that of PET, so PEN is more suitable for making transparent products than PET.
(1) General performance PEN appearance is similar to PET, relative density of 1.36, water absorption rate of 0.3%, both slightly lower than PET, molding shrinkage longitudinal is 0.9%, lower than PET 1.5%, transverse shrinkage rate is almost zero.
PEN is transparent under visible light and can pass through light with wavelengths below 380 nm in the ultraviolet range. It is easy to change color in sunlight, but it is lightfaster than PET.
(2) Thermal performance The thermal deformation temperature of PEN is 121°C, which is 36°C higher than that of PET, and the melting temperature is 273°C, which is slightly higher than that of PET. PEN has good long-term heat resistance and can be used for a long time at 155°C.
PEN has good dimensional stability, small thermal shrinkage of only 0.9% at 150°C, nearly 60% smaller than PET, and thermal expansion coefficient of 13×10-6/°C (longitudinal), slightly lower than PET.
(3) Mechanical properties The mechanical properties of PEN are generally higher than those of PET, and its tensile strength is 60MPa, which is about 35% higher than that of PET. Biaxially oriented film has better mechanical properties, with a longitudinal tensile strength of 280MPa and a transverse tensile strength of 270MPa. The flexural modulus of PEN is 5% higher than that of PET, the elongation at break is slightly lower than that of PET, the right-angle tear strength is comparable to that of PET, and the impact strength is about 15% lower than that of PET.
Due to the slow crystallization rate of PEN molecules and the low crystallinity caused by molecular orientation during stretching, it is more suitable for high-rate stretching than PET.
(4) Chemical properties Because the molecular structure contains ester groups, hydrolysis reaction will occur when exposed to water. However, the hydrolysis rate of PEN is smaller than that of PET, and the degradation of mechanical properties caused by hydrolysis is only one-third of that of PET.
PEN is resistant to almost all chemicals except concentrated sulphuric acid, concentrated nitric acid and concentrated hydrochloric acid. Its radiation resistance is about 6 times that of PET, and it can reach 11 MGy.
(5) Electrical properties The dielectric strength and resistivity of PEN are comparable to those of PET, and the change is small over a wide temperature range.
(6) Barrier performance One of the most outstanding properties of PEN is excellent barrier property, and the barrier performance of various small molecule substances is better than that of PET. The barrier performance of O2 is 4 times that of PET, and the transmittance coefficient is 9.6 (cm3). The barrier performance of CO2 is 5 times that of PET, and the transmittance coefficient is 35 (cm3); The barrier performance of H2O is 3.5 times that of PET, and the transmittance coefficient is 6.7 (g).
3. Molding processing
PEN, like PET, is a non-Newtonian fluid, and its viscosity is not sensitive to temperature, but to shear rate. Its melt viscosity is about 10 times higher than that of PET, and the processing temperature is higher than that of PET, and the processing methods available for PET are suitable for PEN processing.
4. Scope of application
(1) The use of high barrier performance The largest use of PEN is barrier packaging materials, which are used for food and medical packaging, specifically the packaging of beer, soft drinks, milk and fresh food. In 1998, the first batch of PEN beer bottles appeared in SIPA in Italy, and the beer tasted the same as that of glass bottles after 6~9 months of storage, and the CO2 content was the same.
(2) The use of high-strength, high-rigidity PEN can be used to manufacture high-grade tape base film, film, F-class insulating materials, optical discs, heat-resistant capacitor films, speaker microphone vibration films, etc.
(3) Using heat resistance and dimensional stability, PEN can produce transparent conductive films, high-density floppy disks, optical discs, electronic components, transformers, flexible printed circuit boards, integrated circuit bases and flat heating elements.
(4) Radiation resistance can be used to produce diaphragms in aerospace products and atomic furnaces.