Preparation And Dielectric Properties Of Blend Modified Polybutene-1 Films

With the development of electronic information industry,capacitors have a wide and important use in the daily life.Capacitor diaphragm is an important component of the capacitor,and its dielectric properties are one of important factors to determine the energy density of the capacitor.At present,the biaxially oriented polypropylene film(referred to as BOPP)with excellent dielectric properties occupies an important seat in the capacitor diaphragm.Compared with polypropylene(referred to as PP),the environmental stress cracking resistance and creep resistance of polybutylene-1(referred to as PB-1)are excellent.In addition,the reported permittivity of PB-1(about 2.53)is higher than that of electrical grade polypropylene(2.2 or so).However,the research of PB-1 film in the field of capacitors has not attracted much attention.In this paper,a series of PB-1 films were prepared by the method of simultaneous biaxial stretching,using the self-made small polyolefin biaxial stretching equipment.The PB-1 films were prepared by changing the critical processing conditions,such as tensile temperature and tensile rate.The effects of technological parameters on the dielectric properties of the films were investigated and the optimum tensile conditions were found out.It is found that the tensile process conditions affect the uniformity and roughness of the film.The better the uniformity is,the larger the dielectric constant of the film is.In addition,the tensile process parameters affect the molecular chain orientation of the film.The better the degree of orientation is,the greater the dielectric constant is.When the tensile temperature is 123 ? and the tensile speed is 40 mm/min,the prepared PB-1 film has the smallest roughness and the best degree of orientation,so its dielectric constant is maximum(about 4.1)and the dielectric loss is very low(<0.001).The dielectric constant of the pure polymer is generally low(<10),and the capacitance and energy storage density can not be greatly improved.In order to prepare the dielectric materials with high dielectric constant,the conductive materials can be added to the polymer.The composites with different polyaniline content were prepared by melt blending.The prepared composites were hot pressed into sheets,and the films were prepared under the same tensile conditions.Their dielectric properties were measured and compared with the dielectric properties of the PB-1 film.It is found that the percolation threshold of PANI/PB-1 system is between 4 mass % and 5 mass %.By the linear fitting of log(?')and log(fC-f PANI),the percolation threshold is about 4.11 mass %.When the content of PANI is 5 mass %,the dielectric constant of the PANI/PB-1 film is 147.18 at 100 Hz.The addition of conductive particles causes a large amount of micro-capacitance to be formed inside the material,so that the dielectric constant is improved.In addition,the addition of PANI makes the mechanical properties of the composites worse and less impact on the rheological properties of the material.The composites with different CNFs content were prepared by melt blending.The films were prepared by the same method as above.The dielectric properties were measured and compared with the polybutene-1 film.It is found that the percolation threshold of the CNFs/PB-1 system is between 5 mass % and 6 mass %.By the linear fitting of log(?')and log(fC-f CNFs),the percolation threshold is about 5.08 mass %.When the content of CNFs is 6 mass %,the dielectric constant of CNFs/PB-1 film can reach 15.874 at 100 Hz.The addition of CNFs has an effect on the crystallinity and mechanical properties of the samples.The addition of conductive particles causes a large amount of micro-capacitance to be formed inside the material,so that the dielectric constant is improved.In addition,the addition of CNFs makes the mechanical properties of the composites worse.The complex viscosity,storage modulus and loss modulus of the composites are slightly increased.The PANI/CNFs/PB-1 composites were prepared by melt blending,and the films were prepared by the same method as described above.It is found that the dielectric constants of the films prepared with the mixed fillers of PANI and CNFs are less than the dielectric constants of the films with CNFs or PANI separately,under the same amount of conductive particles(4 mass %).However,the conductivities of PANI/CNFs/PB-1 films have reached the order of 10-5,and the dielectric constants have not increased greatly.This phenomenon may occur because the two conductive particles exist alone,destroying the physical and chemical structure of the matrix.Finally,the rheological properties of the composites were discussed.It is found that the addition of PANI,CNFs or PANI and CNFs mixed filler has little effect on the rheological properties of the composites.Relatively speaking,the complex viscosity,storge modulus and loss modulus of CNFs/PB-1 are slightly larger.The complex viscosity of the material decreases with increasing frequency.The storage modulus and loss modulus increase with frequency.The loss factor decreases with increasing frequency.The storage modulus and loss modulus of the material decrease with increasing temperature,and the loss factor increases with increasing temperature.