Applications and methods of infrared spectroscopy in identifying ultra-high molecular weight polyethylene composites

Abstract

This invention relates to the application and method of infrared spectroscopy in identifying ultra-high molecular weight polyethylene (UHMWPE) composite materials, specifically to determine whether UHMWPE composite materials contain high-density polyethylene (HDPE). The steps are as follows: 1) Prepare pure UHMWPE and pure HDPE separately; 2) Blend UHMWPE / HDPE composite materials in a certain proportion; 3) Collect the spectra of the pure product and the reference product as standard spectra; 4) Collect the spectrum of the sample to be tested and compare it with the standard spectrum. The peak area at a specific wavenumber is used to determine whether the sample contains HDPE and to preliminarily determine the content range. This invention establishes a rapid and accurate identification method, and simultaneously determines the HDPE proportion range in UHMWPE products based on the comparison of peak areas at specific wavenumbers, further understanding the performance of UHMWPE products.

Description

Technical Field

[0001] This invention belongs to the field of rapid detection technology, specifically relating to the application and method of infrared spectroscopy in identifying ultra-high molecular weight polyethylene composite materials. Background Technology

[0002] Ultra-high molecular weight polyethylene (UHMWPE), as a special engineering plastic, possesses excellent properties such as wear resistance, high strength, impact resistance, abrasion resistance, and self-lubrication. It is widely used in aerospace, defense, marine engineering, pipeline drainage, and new energy materials fields as fibers, films, pipes, and sheets. However, due to its extremely high molecular weight and the random entanglement of linear segments, UHMWPE exhibits extremely high melt viscosity and poor flowability, which is unfavorable for molding and processing, resulting in low production efficiency. Recent studies on UHMWPE materials have shown that by modifying them with low- to medium-molecular-weight polyethylene and detangling agents, UHMWPE pipes and sheets can be produced through extrusion molding using a specially designed single-screw extruder. Conversely, adding UHMWPE to polymers such as polyethylene and polypropylene can also improve the performance of these composite materials. However, in actual production, there is often a phenomenon where large amounts of HDPE are added to UHMWPE products as flow improvers. Due to excessively high processing temperatures, HDPE molecular chains break down and oxidize, ultimately affecting the performance of the products. Therefore, it is essential to quickly identify whether a certain amount of HDPE has been added to a specific grade of UHMWPE product for performance evaluation. Summary of the Invention

[0003] In view of the problems existing in the prior art, one purpose of this invention is to provide an application of infrared spectroscopy in the identification of ultra-high molecular weight polyethylene composite materials.

[0004] Specifically, it is used to identify whether ultra-high molecular weight polyethylene composite materials contain medium- or low molecular weight high-density polyethylene.

[0005] Furthermore, a preliminary assessment was made of the proportion of medium and low molecular weight high-density polyethylene contained in ultra-high molecular weight polyethylene composite products of the same brand.

[0006] Another object of the present invention is to provide a method for identifying ultra-high molecular weight polyethylene composite materials using infrared spectroscopy, the method comprising the following steps:

[0007] 1) Preparation of pure products: High-flowability pure ultra-high molecular weight polyethylene and pure medium-low molecular weight high-density polyethylene were prepared separately;

[0008] 2) Preparation of reference standard: Pure ultra-high molecular weight polyethylene and pure medium and low molecular weight high density polyethylene were blended in a certain proportion and extruded separately to prepare UHMWPT / HDPE composite materials;

[0009] 3) Spectral acquisition: Wavenumbers of the pure sample and the reference sample were collected separately in the range of 1000 cm⁻¹. -1 -800cm -1 The spectrum is used as a standard spectrum;

[0010] 4) Spectral acquisition of test samples: Samples of the same grade were acquired using an infrared spectrometer with a wavenumber range of 1000 cm⁻¹. -1 -800cm -1 The spectra of the sample to be tested were obtained and compared with the standard spectra. The peak area at a specific wavenumber was used to determine whether the sample contained medium and low molecular weight high-density polyethylene and to preliminarily determine the content range.

[0011] Furthermore, in step 2), a certain proportion refers to the blending of ultra-high molecular weight polyethylene and pure medium-low molecular weight high-density polyethylene at a mass ratio of 9:1, 8:2, 7:3, 6:4, or 1:1.

[0012] Furthermore, in step 4), the specific wavenumber refers to 908 cm⁻¹. -1 .

[0013] Furthermore, the conditions for infrared spectroscopy are: attenuated total reflectance method, test range 4000 cm⁻¹. -1 -400cm -1 Test resolution 4cm -1 The number of scans was 32.

[0014] This invention utilizes a specific spectral wavenumber of 908 cm⁻¹ -1 To establish a rapid and accurate identification method, and based on the comparison of peak areas at a specific wavenumber, to further determine the range of HDPE proportions in UHMWPE products, and to further understand the performance of UHMWPE products. Attached Figure Description

[0015] Figure 1 The infrared spectra of pure UHMWPE and pure HDPE are shown below (where (a) is the infrared curve of pure UHMWPE and pure HDPE, and (b) is the infrared curve at 1000 cm⁻¹). -1 -800cm -1 Infrared curves of pure UHMWPE and pure HDPE;

[0016] Figure 2 908cm -1 Infrared spectra of UHMWPE / HDPE composites at different ratios;

[0017] Figure 3 TGA curves of UHMWPE / HDPE composites at different ratios;

[0018] Figure 4 DTG curves of UHMWPE / HDPE composites at different ratios;

[0019] Figure 5 DSC curves of UHMWPE / HDPE composites with different proportions are shown. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to the accompanying drawings to provide a better understanding of the technical solution.

[0021] Raw materials and instruments

[0022] UHMWPE: Grade U030, produced by Korean Petrochemical; HDPE: Grade Q281, produced by Sinopec; effective flow improver, MV2.

[0023] Infrared spectrometer: Model INVENIO-S, Bruker GmbH, Germany; Differential scanning calorimeter: Model DSC3500Sirius, Netzsch GmbH, Germany; Thermogravimetric analyzer: Model TG 209F1, Netzsch GmbH, Germany.

[0024] Sample preparation

[0025] High-flowability pure UHMWPE and pure HDPE were prepared, and UHMWPE / HDPE composite materials were prepared by blending and extrusion according to certain ratios (9 / 1, 8 / 2, 7 / 3, 6 / 4, 5 / 5). The mass ratios of UHMWPE and HDPE were 9:1, 8:2, 7:3, 6:4, and 5:5, respectively.

[0026] Testing and Characterization

[0027] FT-IR spectroscopy: attenuated total reflectance method, test range 4000 cm⁻¹ -1 -400cm -1 Test resolution 4cm -1 The number of scans was 32, and the infrared spectrum is shown below. Figures 1-2 .

[0028] Figure 1 Infrared spectra of pure UHMWPE and pure HDPE. From Figure 1 As can be seen in (a), UHMWPE and HDPE are basically identical in molecular structure, with values ​​of 2915, 2848, 1471, 1464, 729, and 717 cm⁻¹. -1 The absorption band is the vibrational peak of -CH2-. However, when the wavenumber range is narrowed to 1000 cm⁻¹... -1 -800cm -1 At times, such as Figure 1As shown in (b), at 908cm -1 Pure HDPE exhibits a noticeable peak, with the peak area detailed in Table 1.

[0029] Table 1 908cm -1 Peak area

[0030]

[0031] Infrared spectra of UHMWPE / HDPE composite material and 908 cm⁻¹ -1 Compare the peak areas, such as Figure 2 As shown in Table 1, it was found that with the increase of HDPE content, 908cm -1 The intensity and area of ​​the peak gradually increase. Therefore, given the raw material grade used in this paper, the difference in peak area and intensity can be used to quickly identify whether a certain amount of HDPE has been added to the UHMWPE product of that grade, and a preliminary judgment can be made on the ratio of UHMWPE / HDPE composite materials based on the peak area.

[0032] TG test: The sample was heated from 30℃ to 650℃ under a nitrogen atmosphere, with a gas flow rate of 50ml / min and a heating rate of 10℃ / min.

[0033] Figure 3 , Figure 4 Table 1 shows the TGA and DTG curves of UHMWPE / HDPE composites at different ratios, and Table 2 shows the maximum thermogravimetric temperature (TGA) of the composites. As can be seen from the graphs, the maximum TGA of the HDPE raw material used in this application is higher than that of UHMWPE. It is speculated that because the UHMWPE raw material is a powder, additives were added during the preparation process to enhance its flowability and make it easier to process, thus resulting in a lower maximum TGA. However, after UHMWPE and HDPE are compounded in a certain ratio, the thermal stability of the composite material gradually increases. The maximum TGA reaches 502℃ at a ratio of UHMWPE / HDPE / 6 / 4, which is higher than that of pure UHMWPE and HDPE alone.

[0034] Table 2 Maximum thermogravimetric temperatures of UHMWPE / HDPE composites with different proportions.

[0035]

[0036] DSC test: Under a nitrogen atmosphere, the sample was first heated from -20℃ to 200℃ and held at that temperature for 5 minutes to eliminate thermal history. Then it was cooled to -20℃ and heated again to 200℃. The gas flow rate was 50 ml / min, and the heating and cooling rates were both 10℃ / min.

[0037] Figure 5 Table 3 shows the second heating DSC curves of UHMWPE / HDPE composites with different ratios. Table 3 shows the melting temperatures of UHMWPE / HDPE composites with different ratios. As can be seen from the figure, UHMWPE and HDPE used in this application have certain compatibility. However, as the HDPE content increases, the compatibility of the composites deteriorates. When UHMWPE:HDPE = 8:2, the melting peak temperature becomes wider, and when the ratio is 7:3, two melting peak temperatures appear clearly.

[0038] As shown in Table 3, although the melting temperature of UHMWPE products decreases after composite processing, it is still higher than that of pure HDPE, indicating that the composite material can still maintain good thermal stability even with poor compatibility.

[0039] Table 3 Melting temperatures of UHMWPE / HDPE composites with different proportions

[0040]

[0041] In actual processing and production, infrared spectroscopy can be used to distinguish specific grades of UHMWPE and HDPE materials, quickly identifying whether a certain amount of HDPE has been added to UHMWPE products. Furthermore, by preparing UHMWPE / HDPE composites in different proportions, the properties of the composites can be studied using DSC and TGA techniques. Studies show that after blending UHMWPE and HDPE materials in a certain proportion, although the melting temperature is lower than that of pure UHMWPE, it still maintains good thermal stability, and the maximum thermogravimetric temperature is also increased. With the deepening research into UHMWPE / HDPE composite material modification technology, this new material will undoubtedly have a broader application prospect.

Claims

1. The application of infrared spectroscopy in identifying ultra-high molecular weight polyethylene composite materials, characterized in that... This application is primarily used to identify whether ultra-high molecular weight polyethylene composites contain medium- or low molecular weight high-density polyethylene, specifically using a 1000cm² chromatogram. -1 -800cm -1 Identification is performed using the infrared spectrum of wavenumber.

2. The application as described in claim 1, characterized in that... This application further makes a preliminary judgment on the proportion of medium and low molecular weight high-density polyethylene contained in ultra-high molecular weight polyethylene composite products of the same brand.

3. A method for identifying ultra-high molecular weight polyethylene composite materials using infrared spectroscopy, characterized in that, The method includes the following steps: 1) Preparation of pure products: High-flowability pure ultra-high molecular weight polyethylene and pure medium-low molecular weight high-density polyethylene were prepared separately; 2) Preparation of reference standard: Pure ultra-high molecular weight polyethylene and pure medium and low molecular weight high density polyethylene were blended in a certain proportion and extruded separately to prepare UHMWPT / HDPE composite materials; 3) Spectral acquisition: Wavenumbers of the pure sample and the reference sample were collected separately in the range of 1000 cm⁻¹. -1 -800cm -1 The spectrum is used as a standard spectrum; 4) Spectral acquisition of test samples: Samples of the same grade were acquired using an infrared spectrometer with a wavenumber range of 1000 cm⁻¹. -1 -800cm -1 The spectra of the sample to be tested were obtained and compared with the standard spectra. The peak area at a specific wavenumber was used to determine whether the sample contained medium and low molecular weight high-density polyethylene and to preliminarily determine the content range.

4. The method for identifying ultra-high molecular weight polyethylene composite materials using infrared spectroscopy as described in claim 3, characterized in that... The "certain proportion" in step 2) refers to the blending of ultra-high molecular weight polyethylene and pure medium-low molecular weight high-density polyethylene at a mass ratio of 9:1, 8:2, 7:3, 6:4, or 1:

1.

5. The method for identifying ultra-high molecular weight polyethylene composite materials using infrared spectroscopy as described in claim 3, characterized in that... In step 4), the specific wavenumber refers to 908 cm⁻¹. -1 .

6. The method for identifying ultra-high molecular weight polyethylene composite materials using infrared spectroscopy as described in claim 3, characterized in that... The conditions for infrared spectroscopy were: attenuated total reflectance method, test range 4000 cm⁻¹. -1 -400cm -1 Test resolution 4cm -1 The number of scans was 32.

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