Application of Terahertz Spectroscopy in Porosity Detection of Polyolefin Films

Qing Li; Mingxia He

doi:10.3788/LOP221114

Laser & Optoelectronics Progress, Volume. 60, Issue 9, 0930003(2023)

Application of Terahertz Spectroscopy in Porosity Detection of Polyolefin Films

Qing Li^1,2 and Mingxia He^1,2、*

¹State Key Laboratory of Precision Measuring Technology and Instruments, School of Precision Instrument and Opto-electronics Engineering, Tianjin University, Tianjin 300072, China

²Center for Terahertz Waves, Tianjin University, Tianjin 300072, China

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Figures & Tables(11)

Fig. 1. Composition diagram of mixture sample prepared for THz-TDS system^［10］

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Fig. 2. Wiener bounds model^［12］

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Fig. 3. Thin film thickness extraction of cathode coating for lithium battery. (a) THz-TDS signal and EEMD fitting results; (b) dual time-domain signal after decomposition

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Fig. 4. Relationship between porosity and permittivity using common effective medium models

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Fig. 5. Simulation results of effective medium model. (a) Fitting with permittivity detection results; (b) absolute error value

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Table 1. Theoretical and experimental porosity values of PP/PE/PP separator (LLL model)
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Table 1. Theoretical and experimental porosity values of PP/PE/PP separator (LLL model)
No.
Porosity
（theoretical value）
Porosity
（experimental value）
Relative error /%
1 40 37.78 5.54
2 45 42.46 5.63
3 50 48.19 3.61
4 55 48.93 11.00
5 60 55.19 8.01

Table 2. Theoretical and experimental porosity values of PP/PE/PP separator (AB-EMA model)
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Table 2. Theoretical and experimental porosity values of PP/PE/PP separator (AB-EMA model)
No.
Porosity
（theoretical value）
Porosity
（experimental value）
Relative error /%
1 40 39.87 0.32
2 45 45.53 1.17
3 50 52.73 5.46
4 55 53.69 2.39
5 60 61.99 3.33

Table 3. Theoretical and experimental porosity values of PP/PE/PP separator (Winer upper bound model)
View table
Table 3. Theoretical and experimental porosity values of PP/PE/PP separator (Winer upper bound model)
No.
Porosity
（theoretical value）
Porosity
（experimental value）
Relative error /%
1 40 44.33 10.83
2 45 49.24 9.42
3 50 55.08 10.16
4 55 55.82 1.49
5 60 61.97 3.29

Table 4. Intrinsic permittivity of PP separator and PP/PE/PP separator
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Table 4. Intrinsic permittivity of PP separator and PP/PE/PP separator
Model Average value Max Min Variance
LLL 2.2848 2.2967 2.2609 0.0021
AB-EMA 2.3066 2.3143 2.2877 0.0002
Wiener upper bound 2.2748 2.3102 2.2304 0.0037

Table 5. Measurement errors
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Table 5. Measurement errors
n $θ = 1 °$ /% $θ = 2 °$ /% $θ = 3 °$ /% $θ = 4 °$ /% $θ = 5 °$ /%
1.5 0.036 0.144 0.326 0.581 0.905
1.7 0.027 0.108 0.249 0.438 0.689
2.0 0.019 0.076 0.173 0.306 0.481

Table 6. Thickness, permittivity, and porosity of microporous membranes with different pore sizes
View table
Table 6. Thickness, permittivity, and porosity of microporous membranes with different pore sizes
Pore size /μm d /μm $ε_{e f f}$ Porosity /%
0.45 221 1.27 76
2 186 1.31 81
3 192 1.31 82
5 205 1.29 78

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Qing Li, Mingxia He. Application of Terahertz Spectroscopy in Porosity Detection of Polyolefin Films[J]. Laser & Optoelectronics Progress, 2023, 60(9): 0930003

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Paper Information

Category: Spectroscopy

Received: Mar. 25, 2022

Accepted: May. 12, 2022

Published Online: May. 9, 2023

The Author Email: Mingxia He (hhmmxx@tju.edu.cn)

DOI:10.3788/LOP221114

Topics

laser devices and laser physics

Lasers and Laser Optics

Laser physics

laser manufacturing

Instrumentation, Measurement and Metrology

Table 1. Theoretical and experimental porosity values of PP/PE/PP separator (LLL model)

Table 1. Theoretical and experimental porosity values of PP/PE/PP separator (LLL model)

Table 2. Theoretical and experimental porosity values of PP/PE/PP separator (AB-EMA model)

Table 2. Theoretical and experimental porosity values of PP/PE/PP separator (AB-EMA model)

Table 3. Theoretical and experimental porosity values of PP/PE/PP separator (Winer upper bound model)

Table 3. Theoretical and experimental porosity values of PP/PE/PP separator (Winer upper bound model)

Table 4. Intrinsic permittivity of PP separator and PP/PE/PP separator

Table 4. Intrinsic permittivity of PP separator and PP/PE/PP separator

Table 5. Measurement errors

Table 5. Measurement errors

Table 6. Thickness, permittivity, and porosity of microporous membranes with different pore sizes

Table 6. Thickness, permittivity, and porosity of microporous membranes with different pore sizes