A method for quantitative analysis of rubber surface wax film
By forming a gold film on the rubber surface and transferring the wax film using tape, combined with DSC analysis, the problems of accuracy and complexity in wax film analysis in the prior art are solved, and simple and accurate quantitative analysis of wax film is realized.
Patent Information
- Application Number
- CN202610577498.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-04-28
- Publication Date
- 2026-06-19
Smart Images
Figure CN122238412A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of rubber material surface analysis technology, and in particular to a method for quantitative analysis of wax film on rubber surface. Background Technology
[0002] Microcrystalline wax is an important additive in tire production. After rubber vulcanization, protective wax gradually precipitates onto the surface, forming a barrier layer that provides protection against static aging. The thickness or amount of wax film is an important reference indicator for evaluating its protective effect; therefore, accurate quantitative analysis of the wax film on the rubber surface is of great significance.
[0003] Currently, there are two main methods for analyzing wax films on rubber surfaces: (1) Wiping method. The specific process of this method is as follows: cut a sample of rubber with a certain area, weigh it, and then use degreased cotton soaked in organic solvents such as cyclohexane or n-hexane to quickly wipe the upper and lower surfaces of the rubber. After the surface dries, weigh it again. The mass of surface wax precipitation is obtained by the mass difference before and after wiping, and then the wax film thickness is calculated. However, this method has obvious shortcomings: First, during the solvent wiping process, the rubber will quickly swell to a certain extent, causing various additives inside the rubber to dissolve, and the surface wax film may also re-dissolve into the rubber; Second, the rubber is elastic, and it is difficult to ensure the accuracy of the sample area when cutting; In addition, an extra thorough drying process is required after wiping, and the drying time is difficult to control. The introduction of the above-mentioned interference factors makes the measurement results very inaccurate.
[0004] (2) Scanning Electron Microscopy (SEM). This method is an image measurement method. The cross-section of the rubber is obtained through pretreatment, and then observed under a scanning electron microscope. The thickness of the wax film is determined through image geometry measurement. The key to this method is obtaining a smooth and regular rubber cross-section through pretreatment. However, due to the difference in toughness between the protective wax film and the rubber, direct cutting at room temperature or resin encapsulation will cause damage or even defects to the edge wax film. Obtaining an intact wax film cross-section at ultra-low temperatures is difficult and requires the use of an ultrathin cryostat. Furthermore, atomic force microscopy, because the wax layer thickness often exceeds its Z-axis limit, also requires ultrathin cryostat sections for cross-sectional observation. The overall complexity and equipment cost of the above methods are high, making them difficult to meet the needs of routine testing.
[0005] In summary, existing wiping methods suffer from poor accuracy, while image analysis methods such as scanning electron microscopy are complex to operate and require expensive equipment. Therefore, there is an urgent need for a simple and accurate quantitative analysis method for wax films on rubber surfaces. Summary of the Invention
[0006] The purpose of this invention is to overcome the shortcomings of the existing technology and to develop a quantitative analysis method for wax film on rubber surface in order to solve the problems mentioned in the background art.
[0007] A method for quantitative analysis of wax film on rubber surface, comprising the following steps: Step S1: Vacuum gold sputtering is performed on the surface of the rubber sample to form a thin gold film on its surface; Step S2: Use tape to stick to the gold film and press it firmly, then peel off the tape to transfer the gold film and the wax film attached thereto onto the tape. Step S3: Cut the area of the peeled tape containing the wax film to obtain a tape sample sheet with a fixed area. Step S4: Analyze the tape sample sheet by differential scanning calorimetry, measure the enthalpy of melting of wax, and calculate the amount and / or average thickness of wax film precipitation on the rubber surface based on the standard working curve and the fixed area.
[0008] As a further aspect of the present invention: the gold sputtering process is performed in a vacuum sputtering instrument with a sputtering current of 10 mA and a sputtering time of 60 seconds.
[0009] As a further aspect of the present invention: the tape is a transparent polyacrylate tape, and the tape has no thermal background at 120°C.
[0010] As a further aspect of the present invention, step S3 specifically includes the following steps: First, fold the peeled tape containing the wax film in half to protect and hold the middle wax film layer. Then, use a punch with a 3 mm aperture to punch holes and cut the tape to obtain a tape sample sheet with a fixed area.
[0011] As a further aspect of the present invention, step S4 specifically includes the following steps: The thermal enthalpy of the sample was obtained by measuring the area of the wax melting peak in the first heating curve of the tape sample using DSC. Based on the standard working curve of raw material wax mass and enthalpy of hot melt, the wax mass in the tape sample sheet was calculated by the external standard method. The average thickness of the wax film is calculated based on the wax mass, wax density, and fixed area, using the following formula: ; in, For wax quality, The density of the wax. This refers to the hole diameter of the hole punch.
[0012] As a further aspect of the present invention: the method for establishing the standard working curve is as follows: Different qualities of raw material microcrystalline wax were taken, packaged together with blank transparent tape, and then subjected to DSC testing. Take the second heating curve segment, integrate the melting peaks for each mass to obtain the peak area, and calculate the corresponding melting enthalpy change; The standard working curve is obtained by plotting the enthalpy change of the melt against mass.
[0013] As a further aspect of the present invention, the central carbon number distribution range of the raw material microcrystalline wax is 25 to 38.
[0014] As a further aspect of the present invention: the DSC analysis employs the following heating procedure: Starting from -40 °C, the temperature was increased to 120 °C at a rate of 20 K / min, and the heat flow changes during the heating process were recorded. Both the protective gas and the purging gas were nitrogen.
[0015] As a further aspect of the present invention: when the wax film morphology on the rubber surface is confirmed to be a discontinuous layered block shape by SEM characterization, a geometric model conversion factor corresponding to the block morphology is introduced when calculating the wax film thickness, so as to convert the average thickness into a physical thickness that reflects the real block structure.
[0016] As a further aspect of the present invention: in step S3, the tape is cut multiple times at different positions to obtain multiple tape sample pieces; in step four, the multiple tape sample pieces are analyzed separately, and the average value of the results is taken as the final wax film precipitation amount and average thickness.
[0017] Compared with the prior art, the present invention has the following technical advantages: Using the above technical solution, this invention achieves DSC analysis of wax film thickness through tape adhesion and peeling. Firstly, the sampling method of this invention has the advantages of high transfer efficiency, accurate sampling area, and convenient operation, providing a complete approach to peeling off the wax film from the rubber surface. This sampling method has application potential in various analytical methods. This invention increases the adhesion between the wax film on the rubber surface and the tape through gold sputtering, achieving a single-pass peeling rate of over 90%, improving peeling efficiency and ensuring the integrity of the wax film. Secondly, after peeling off the wax film, folding the tape and then sampling through a punch allows for precise control of the sampling area and protects the wax film in the middle during sampling. Finally, the transparent tape exhibits no thermal effect change within the test temperature range, and its low density and thinness significantly improve the signal-to-noise ratio of the wax film in DSC testing. In summary, the thickness of the wax film can be accurately determined by measuring the melting peak area of the wax film transferred by the tape using DSC. Attached Figure Description
[0018] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the steps of the quantitative analysis method disclosed in this application. Figure 2 This is a schematic diagram of tape application and folding according to an embodiment of this application; Figure 3 This is a SEM image of the wax film morphology of an embodiment disclosed in this application; Figure 4 This is a schematic diagram of SEM characterization of a rubber sample adhered with tape according to an embodiment of this application. Figure 5 This is a GC-MS characterization result of a continuous bonding test on tire samples according to an embodiment of this application. Figure 6 This is a schematic diagram illustrating the optimization of gold spraying time according to an embodiment of this application; Figure 7 This is a schematic diagram illustrating the improvement of the adhesion effect of gold spraying in an embodiment of this application; Figure 8 This is a standard working curve diagram of DSC analysis of raw material wax in an embodiment of this application; Figure 9 This is a graph showing the quantitative results of DSC analysis of different raw material waxes in the embodiments disclosed in this application; Figure 10 The figures show the DSC analysis results of different quantities of waxed rubber samples from the embodiments disclosed in this application. Figure 11 This is a graph showing the relationship between the enthalpy of heat dissipation and the wax content of the samples in the embodiments disclosed in this application; Figure 12 This is a schematic diagram of the cross-section of a frozen section of sample #7 and the thickness of the wax film, as disclosed in this application. Detailed Implementation
[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0020] Example 1: Please refer to Figure 1 In this embodiment of the invention, a method for quantitative analysis of wax film on rubber surface includes the following steps: Step S1: Vacuum gold sputtering is performed on the surface of the rubber sample to form a thin gold film on its surface; Step S2: Use tape to stick to the gold film and press it firmly, then peel off the tape to transfer the gold film and the wax film attached thereto onto the tape. Step S3: Cut the area of the peeled tape containing the wax film to obtain a tape sample sheet with a fixed area. Step S4: Analyze the tape sample sheet by differential scanning calorimetry, measure the enthalpy of melting of wax, and calculate the amount and average thickness of wax film precipitation on the rubber surface based on the standard working curve and the fixed area.
[0021] In this embodiment, the gold sputtering process is performed in a vacuum sputtering instrument with a sputtering current of 10 mA and a sputtering time of 60 seconds.
[0022] In this embodiment, the tape is a transparent polyacrylate tape, which has no thermal background at 120 °C.
[0023] In this embodiment, step S3 specifically includes the following steps: First, fold the peeled tape containing the wax film in half to protect and hold the middle wax film layer. Then, use a punch with a 3 mm aperture to punch holes and cut the tape to obtain a tape sample sheet with a fixed area.
[0024] In this embodiment, step S4 specifically includes the following steps: The thermal enthalpy of the sample was obtained by measuring the area of the wax melting peak in the first heating curve of the tape sample using DSC. Based on the standard working curve of raw material wax mass and enthalpy of hot melt, the wax mass in the tape sample sheet was calculated by the external standard method. The average thickness of the wax film is calculated based on the wax mass, wax density, and fixed area, using the following formula: ; in, For wax quality, The density of the wax. This refers to the hole diameter of the hole punch.
[0025] In this embodiment, the method for establishing the standard working curve is as follows: Different qualities of raw material microcrystalline wax were taken, packaged together with blank transparent tape, and then subjected to DSC testing. Take the second heating curve segment, integrate the melting peaks for each mass to obtain the peak area, and calculate the corresponding melting enthalpy change; The standard working curve is obtained by plotting the enthalpy change of the melt against mass.
[0026] In this embodiment, the central carbon number distribution range of the raw material microcrystalline wax is 25 to 38.
[0027] In this embodiment, the DSC analysis uses the following temperature ramping procedure: Starting from -40 °C, the temperature was increased to 120 °C at a rate of 20 K / min, and the heat flow changes during the heating process were recorded. Both the protective gas and the purging gas were nitrogen.
[0028] In this embodiment, when the wax film morphology on the rubber surface is confirmed to be a discontinuous layered block shape by SEM characterization, a geometric model conversion factor corresponding to the block morphology is introduced when calculating the wax film thickness to convert the average thickness into a physical thickness that reflects the real block structure.
[0029] In this embodiment, in step S3, the tape is cut multiple times at different positions to obtain multiple tape sample pieces; in step four, the multiple tape sample pieces are analyzed separately, and the average value of the results is taken as the final wax film precipitation amount and average thickness.
[0030] Example 2: In this embodiment, the specific experimental procedure for DSC analysis is as follows: (S101) Select a relatively clean and flat surface of the rubber sample, and cut a relatively flat sample piece with dimensions (length, width, and height) of 40×20×2 mm (too complex a curved surface will affect the uniformity of the gold plating and the ease of adhesion). The specific size can be adjusted according to the size of the vacuum sputtering chamber and the flatness of the sample. Use a bulb syringe or similar tool to blow away dust and other foreign matter from the surface for later use.
[0031] S102) Place the sample into a vacuum gold sputtering instrument, set the parameters as follows: current 10 mA, sputtering time 30-90 s, preferably 60 s.
[0032] S103) Use polyacrylate adhesive (high tack, thin base and adhesive layer, no heat background at 120°C) to gently attach to the gold-plated surface, and use a tool to scrape it from the middle to both sides to make the tape adhere tightly to the sample without air bubbles.
[0033] like Figure 2 The diagram shows a schematic of applying and folding tape. S104) Fix the sample on the table with double-sided tape or tweezers, peel off the tape vertically with the tape side facing up. The adhesive part is light / dark green, and the color becomes darker as the wax film thickness increases. Then fold the tape in half and stick it tightly to protect the wax layer in the center. S105) Use a hole punch (hole diameter D=3 mm) to take 5 sample pieces at different positions on the folded tape (5 pieces attached top and bottom, 10 pieces in total on one side) for later use; S106) Place the aluminum crucible into the analytical balance (accuracy 0.01 mg) and let it stand until zero. Place the sample piece into the aluminum crucible and weigh it m1. After assembling the crucible lid, seal and package it. S107) Take 5 blank transparent tape samples, fold them in half, punch holes in each sample, weigh them according to step S6 (m0), and seal them. (S108) Standard: Take 5 samples of raw material microcrystalline wax (5-20 mg each), weigh accurately using an analytical balance, and place them in a crucible along with blank tape. Repeat step S6 and weigh M1-M5. S109) The DSC temperature program is shown in Table 2. Place the sample crucible and the blank crucible in the program, input m0, m1, M1-M5 and run the program to measure all samples one by one. As shown in Table 1 below, this is the DSC temperature program.
[0034] For the S1010 standard, the curve segment from the second heating is used, and the hot melt peak is integrated to obtain the five peak areas A1-A5 of the standard. For the sample to be tested, the peak area a1 of the curve from the first heating is used.
[0035] S1011) Calculate the enthalpy change of the standard ΔH1~ΔH5 and the enthalpy Δh1 of the sample; Standard product: ΔH n =A n ×M n n=1~5, Sample: Δh1 = a1 × m1; ΔH is the enthalpy change value of the melting peak, and n is the standard sample number. A standard working curve is constructed using the enthalpy of melting of the standard sample against the mass. The wax mass m2 corresponding to the sample is calculated using the external standard method, and the average thickness d of the wax film is calculated. ; in, For wax quality, The density of the wax. This refers to the hole diameter of the hole punch.
[0036] like Figure 3 As shown, the figure is a SEM characterization image of the wax film morphology; (A) is a layered wax film on the sidewall of a certain brand of tire; (B) is the wax film morphology on the surface of a small compound rubber sample.
[0037] ρ is the density of the raw wax, typically 0.94 g / cm³. 3 It can also be obtained through measurement, where D is the diameter of the punch. On actual tire sidewalls, protective wax often appears in layers. For layered wax layers (such as...) Figure 3 A) Its wax layer thickness is approximately equal to the average thickness d; however, for small-scale compounded rubber sheets, the wax film precipitated at high temperatures (40℃) often appears in blocky form (e.g. Figure 3(B) This is because there is a certain difference between the thickness of the two and the actual vulcanization conditions. Based on the morphology of the actual sample, we simplified it into a closely packed frustum (the ratio of the upper and lower base diameters is 1:2), and its wax layer thickness is approximately 1.89d.
[0038] In this embodiment, the tape peel strength verification step is as follows: We masked the same sample to create three areas: untreated, gold-plated, and gold-plated and then pasted on. Figure 4 As shown, the figure is a SEM image of a rubber sample adhered with tape. After the rubber sample was treated with gold sputtering and the tape was removed, most of the wax was peeled off, with only residue remaining at the edges of the rubber sample. This is mainly because the wax layer at the edges will bulge and deform during the cutting of the sample, and the adhesion effect of the tape at the edges is poor. However, drilling can avoid the edge area, so this does not affect the accuracy of thermal analysis.
[0039] In this embodiment, the tape peeling efficiency verification step is as follows: A sample of a certain brand of tire sidewall was continuously coated with gold, with each coat lasting 60 seconds and covering an area of 8 cm². 2 (2cm × 4cm), after each application, the tape was soaked in 10 mL of cyclohexane and the supernatant was taken for GC-MS analysis. Figure 5 As shown in the figure, the GC-MS characterization results of the continuous bonding test of the tire sample are as follows: more than 90% of the wax layer was peeled off on the first bonding test, and no wax residue was found after wiping with solvent after 4 bonding tests, which proves the high efficiency of the method for extracting wax film.
[0040] In this embodiment, the verification steps for improving the adhesion effect of gold spraying are as follows: Using the same small piece of mating rubber, cut the central portion into multiple 8 cm pieces. 2 The sample pieces were sputtered with gold for different times, adhered with tape, and extracted with 10 mL of cyclohexane. GC-MS analysis was then performed. Figure 6 As shown in the figure, this is a schematic diagram of the optimized sputtering time. The highest wax peak value was obtained when sputtering for 30 seconds. As the sputtering time increased, incomplete peeling of the adhesive tape began to occur, and the extraction efficiency decreased. In addition, GC-MS analysis showed that when no gold sputtering was performed, some high-boiling-point impurities adhered to the adhesive tape, which basically disappeared after 30 seconds of sputtering. However, in order to ensure that the gold plating thickness of each sputtering is sufficient and stable, we optimized the sputtering time to 60 seconds.
[0041] We also masked the same sample, creating two areas: one with gold plating and one without. Then, we used the same tape to cover them to eliminate any potential differences. Figure 7As shown in the figure, the diagram illustrates the improvement of the adhesion effect of gold sputtering. There are no large pieces of wax residue in the area after gold sputtering, while there is a lot of residue in the area without gold sputtering. This verifies the adhesion enhancement effect of this method through gold sputtering. The principle may be that the gold plating layer has good adhesion to both wax and acrylic tape at the same time.
[0042] In this embodiment, the steps for verifying the quantitative analytical capability of DSC for protective wax raw materials are as follows: We selected the relatively common H3241 protective wax as the verification object, and weighed different weights for DSC testing, such as... Figure 8 As shown in the figure, the standard working curve for DSC analysis of the raw material wax is presented; the enthalpy of its melting peak shows a good linear relationship with the mass of the raw material. Furthermore, 8.92 mg of extracted rubber block and 1.59 mg of H3241 wax were weighed together for DSC testing. The sample melting enthalpy was 312.8 mJ, the calculated wax mass was 1.52 mg, and the recovery rate was 104%. All of the above demonstrates that DSC is feasible and has high accuracy in analyzing the quality of wax.
[0043] Furthermore, the carbon number distribution of the wax precipitated on the rubber surface often differs from that of the added raw materials. We were concerned that this difference in carbon number distribution might lead to variations in its ability to generate a thermal effect. Therefore, to verify the feasibility and reliability of this method, we selected six different grades of microcrystalline protective waxes with varying carbon number distributions (central carbon number ranging from 25 to 38), weighed different masses, and conducted DSC tests. The test results are as follows: Figure 9 As shown in the figure, the quantitative results of DSC analysis of different raw material waxes are presented; the enthalpy of melting of different raw materials has a good linear relationship with mass. These results indicate that the enthalpy of thermal change of raw material waxes is minimally affected by their carbon number distribution, meaning our method has broad applicability.
[0044] In this embodiment, the steps for analyzing rubber samples with different wax contents using DSC are as follows: We designed small-component rubber systems containing different amounts of wax, as shown in Table 2 below. After vulcanization, the systems were placed in a 40℃ constant temperature oven for 28 days. The thickness of the surface wax film was analyzed using this method, and the results are as follows: Figure 10 As shown in the figure, the DSC analysis results of wax rubber samples with different wax content are as follows: as the wax content increases, the hot melt peak increases, and the lowest detectable wax content is 2 parts. Substituting the sample enthalpy value into the calculation yields the average thickness of each sample, as shown in Table 3 below. Figure 11 The figure shows the relationship between the enthalpy of melting of the sample and the number of wax components; the number of wax components has a good linear relationship with the measured thickness of the wax film.
[0045] Table 2. Formulation schemes for wax rubber with different parts
[0046] Table 3. Relationship between average sample thickness and wax content
[0047] In this embodiment, the steps for verifying the accuracy of the wax film thickness data are as follows: We selected sample #7 above for SEM cross-sectional analysis, as follows: Figure 12 As shown in the figure, the cross-section of the frozen section of sample #7 and the thickness of the wax film are schematic diagrams. It was found that the wax block on its surface is truncated cone-shaped, with the ratio of the diameter of the upper and lower bases being close to 1:2, and the height of the wax block is about 40-43 μm. By constructing a simplified approximate model, we obtained the relationship between the thickness D of the truncated cone-shaped wax film and the average thickness d as D=1.89d. From this, the thickness of the tested wax film can be calculated to be 44.7 μm, which is basically consistent with the test results, indicating that the method has accuracy and consistency in the analysis of wax film thickness on rubber surfaces.
[0048] In this embodiment, the instruments, equipment, and reagents used can be adjusted according to actual needs.
[0049] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention. The scope of the invention is defined by the appended claims and their equivalents, all of which should be included within the scope of protection of the invention.
Claims
1. A method for quantitative analysis of wax film on rubber surface, characterized in that, Includes the following steps: Step S1: Vacuum gold sputtering is performed on the surface of the rubber sample to form a thin gold film on its surface; Step S2: Use tape to stick to the gold film and press it firmly, then peel off the tape to transfer the gold film and the wax film attached thereto onto the tape. Step S3: Cut the area of the peeled tape containing the wax film to obtain a tape sample sheet with a fixed area. Step S4: Analyze the tape sample sheet by differential scanning calorimetry, measure the enthalpy of melting of wax, and calculate the amount and average thickness of wax film precipitation on the rubber surface based on the standard working curve and the fixed area.
2. The method for quantitative analysis of wax film on rubber surface according to claim 1, characterized in that, The gold sputtering process was performed in a vacuum sputtering instrument with a sputtering current of 10 mA and a sputtering time of 60 seconds.
3. The method for quantitative analysis of wax film on rubber surface according to claim 1, characterized in that, The tape is a transparent polyacrylate tape, and the tape has no thermal background at 120 °C.
4. The method for quantitative analysis of wax film on rubber surface according to claim 1, characterized in that, The specific steps in step S3 include: First, fold the peeled tape containing the wax film in half to protect and hold the wax film layer in the middle. Then, use a punch with a hole diameter of 3mm to punch holes and cut the tape to obtain a tape sample sheet with a fixed area.
5. The method for quantitative analysis of wax film on rubber surface according to claim 1, characterized in that, The specific steps in step S4 include: The thermal enthalpy of the sample was obtained by measuring the area of the wax melting peak in the first heating curve of the tape sample using DSC. Based on the standard working curve of raw material wax mass and enthalpy of hot melt, the wax mass in the tape sample sheet was calculated by the external standard method. The average thickness of the wax film is calculated based on the wax mass, wax density, and fixed area, using the following formula: ； in, For wax quality, The density of the wax. This refers to the hole diameter of the hole punch.
6. The method for quantitative analysis of wax film on rubber surface according to claim 5, characterized in that, The method for establishing the standard working curve is as follows: Different qualities of raw material microcrystalline wax were taken, packaged together with blank transparent tape, and then subjected to DSC testing. Take the second heating curve segment, integrate the melting peaks for each mass to obtain the peak area, and calculate the corresponding melting enthalpy change; The standard working curve is obtained by plotting the enthalpy change of the melt against mass.
7. The method for quantitative analysis of wax film on rubber surface according to claim 6, characterized in that, The central carbon number of the raw material microcrystalline wax ranges from 25 to 38.
8. The method for quantitative analysis of wax film on rubber surface according to claim 5, characterized in that, The DSC analysis used the following temperature procedure: Starting from -40 °C, the temperature was increased to 120 °C at a rate of 20 K / min, and the heat flow changes during the heating process were recorded. Both the protective gas and the purging gas were nitrogen.
9. The method for quantitative analysis of wax film on rubber surface according to claim 5, characterized in that, When SEM characterization confirms that the wax film morphology on the rubber surface is a discontinuous layered block, a geometric model conversion factor corresponding to the block morphology is introduced when calculating the wax film thickness to convert the average thickness into a physical thickness that reflects the actual block structure.
10. The method for quantitative analysis of wax film on rubber surface according to claim 1, characterized in that, In step S3, the tape is cut multiple times at different positions to obtain multiple tape sample pieces; in step four, the multiple tape sample pieces are analyzed separately, and the average value of the results is taken as the final wax film precipitation amount and average thickness.