Structural characteristics and electrical insulating properties of BOPP films based on different stretching modes

doi:10.19491/j.issn.1001-9278.2024.03.010

Abstract

Abstract:

In this work， simultaneous biaxial drawing and sequential biaxial drawing were chosen as two stretching modes to adjust the thickness， extended chain crystal content， fibrillar morphology， and orientation texture of BOPP films， and the working rules of these structural issues on their electrical insulating properties were investigated. The results indicated that a thick lamellar structure with a good thermal stability and an isotropous fibrillated network facilitated an improvement in the breakdown strength and a reduction in the dielectric loss. These results are advantageous to a good understanding on the processing⁃structure⁃property relation of polymer film dielectric.

Key words: biaxially stretched polypropylene, extended chain crystal, fibrillated network, breakdown strength

CLC Number:

TQ325.1⁺4

WANG Peng, YAO Cheng, LIU Gang, CAI Xipeng, JIA Lei, WANG Kai, CHEN Long. Structural characteristics and electrical insulating properties of BOPP films based on different stretching modes[J]. China Plastics, 2024, 38(3): 54-58.

Figures/Tables 9

Fig.1. DSC temperature rise melting curve of a 3.4 μm thick film（a） and （b）； DSC temperature rise melting curve of a 4.5 μm thick film（c） and （d）； relationship between the relative content of extended chain crystals and film thickness（e）

样品	X_c/% （DSC）	X_c/% （XRD）	T_m1/℃	T_m2/℃	T_m3/℃	T_m4/℃
同步_3.4 μm	50.4	58.0	160.8	168.5	170.9	172.2
异步_3.4 μm	50.6	58.6	158.8	166.6	168.9	170.1
同步_4.5 μm	47.0	56.8	160.1	166.7	170.0	171.7
异步_4.5 μm	47.7	54.8	157.3	166.7	168.8	170.6

Tab.1. Crystallinity and melting point of 3.4 μm and 4.5 μm thick films prepared by different stretching methods

Fig.2. XRD diffraction spectra of 3.4 μm and 4.5 μm films prepared by different stretching methods

Fig.3. Surface profile morphology of BOPP films prepared by different stretching methods

Fig.4. AFM observation of the surface microstructure of films prepared by different stretching methods

Fig.5. Stress relaxation behavior of different tensile modes and different thickness films

样品	松弛时间（τ）/s	初始应力（σ₀）/MPa	最终应力（σ）/MPa
同步_4.5 μm/MD	392.4	44.0	20.5
同步_4.5 μm/TD	241.5	102.8	29.7
异步_4.5 μm/MD	373.7	32.6	14.6
异步_4.5 μm/TD	240.8	125.2	36.0
同步_3.4 μm/MD	408.6	46.9	22.5
同步_3.4 μm/TD	260.4	92.1	29.1
异步_3.4 μm/MD	391.4	36.4	17.1
异步_3.4 μm/TD	253.1	146.8	44.9

Tab.2. Characteristic parameters of stress relaxation behavior of various films with different thickness

Fig.6. The Weibull distribution of breakdown field strength of （a） 3.4 μm thick and （b） 4.5 μm thick films prepared by different stretching methods；（c） the relationship between the breakdown field strength （α factor） and the content of thick wafer for simultaneously stretched films

Fig.7. Frequency dependence of dielectric constant and dielectric loss of various BOPP films （a） and （b）； and temperature dependence of dielectric constant and dielectric loss of various BOPP films （c） and （d）

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