Method for detecting content of polyethylene element

Abstract

The invention provides a method for detecting the content of polyethylene elements, and relates to the technical field of polyethylene detection. The method for detecting the content of the polyethylene element mainly comprises the following steps: mixing a powdery or granular polyethylene sample with cellulose, carrying out hot pressing to prepare a polyethylene sheet, testing the prepared polyethylene sheet through a fluorescence spectrophotometer, and calculating by combining the mass of polyethylene and cellulose, the density of the polyethylene sheet and a fluorescence spectrum test result. And obtaining the element content of polyethylene. According to the method, the defects in the prior art are overcome, polyethylene and cellulose are blended, a hot pressing method is adopted for sample preparation, polyethylene is softened in the heating process, cellulose serves as a framework, polyethylene is connected together, the polyethylene and the cellulose are connected to form the test piece, the fluorescence spectrometry is adopted for determination, and the method is simple, efficient, safe and environmentally friendly.

Description

Technical Field

[0001] The invention relates to the technical field of polyethylene detection, and in particular to a method for detecting element content in polyethylene. Background Art

[0002] Polyethylene is an important plastic material that is widely used in daily life and industrial production. However, in some special cases, it is necessary to detect and analyze the elemental composition of polyethylene. As a quality control method, polyethylene elemental composition detection can ensure that the performance and quality of polyethylene products meet the standard requirements. By detecting the elemental composition, the material source, preparation process and quality control of polyethylene can be determined, providing a basis for the optimization and improvement of the production process.

[0003] At present, the detection of element content in polyethylene is in accordance with the standard SH / T 1829-2020 "Determination of trace element content in plastic polyethylene and polypropylene resins - Inductively coupled plasma optical emission spectrometry". When testing according to this standard, a standard curve needs to be established for inductively coupled plasma optical emission spectrometry (ICP-OES). The polyethylene material must be calcined and ashed first, and then the ash is digested before the ICP-OES test is performed. The element content is calculated based on the test results and the standard curve.

[0004] The existing industry standard method for detecting the element content in polyethylene has cumbersome test steps and complicated processes, and requires the preparation of hydrochloric acid, nitric acid and standard solutions, which is neither economical nor safe and environmentally friendly. Therefore, it is very necessary to develop a simple, efficient, safe and environmentally friendly method for detecting the element content in polyethylene. Summary of the invention

[0005] The purpose of the present invention is to solve the problem that the detection process of element content in polyethylene in the prior art is cumbersome, and proposes a method for detecting element content in polyethylene.

[0006] To achieve the above objectives, the technical solution of the present invention is implemented through the following technical solutions:

[0007] A method for detecting the element content of polyethylene, the detection method comprising the following steps:

[0008] (1) Sample preparation: Weigh the polyethylene sample and cellulose separately, record the mass, mix the two evenly, and bond the two together by hot pressing to form a polyethylene sheet;

[0009] (2) Testing: The prepared polyethylene sheet is tested by fluorescence spectrometer;

[0010] (3) Analysis: According to the following formula, the element content of polyethylene is obtained by combining the quality of polyethylene and cellulose, the density of polyethylene sheets and the results of fluorescence spectrum test:

[0011] A%=ρ / ρ0×B%×(1+m0 / m)

[0012] Where A is the element content in the actual polyethylene material; ρ is the density of the polyethylene sheet; ρ0 is the default density during fluorescence spectrometer testing; B is the element content shown in the fluorescence spectrometer test results; m0 is the cellulose mass; and m is the polyethylene sample mass.

[0013] Preferably, the polyethylene sample in step (1) is powder or pellets.

[0014] Preferably, the mass ratio of the polyethylene sample to the cellulose in the polyethylene sheet prepared in step (1) is m:m0=3-4:1.

[0015] Preferably, the polyethylene sheet prepared in step (1) is in the shape of a circular sheet with a diameter of 38 to 40 mm, a thickness of 2.0 to 2.5 mm, and a mass of 2.00 to 2.50 g.

[0016] Preferably, the hot pressing conditions in step (1) are: temperature 100-120° C., pre-pressing 2.8-3.0 MPa, boosting 4.7-5.0 MPa, pre-pressing time 1-2 min, boosting time 2-4 min, and exhaust times 6-10 times.

[0017] Preferably, the conditions for the fluorescence spectrometer test in step (2) are: test power 2.4-3.6 kW, test time 5-10 min.

[0018] The present invention provides a method for detecting the element content of polyethylene, which has the following advantages compared with the prior art:

[0019] (1) The present invention uses fluorescence spectroscopy to determine the element content of polyethylene. The method is simple, efficient, safe and environmentally friendly.

[0020] (2) The present invention blends polyethylene and cellulose and adopts a hot pressing method to prepare samples. During the heating process, the polyethylene softens and the cellulose acts as a skeleton to connect the polyethylene together. The two are bonded to each other to form a test piece. In this way, the temperature required for sample preparation does not need to be very high, which avoids the element changes of the polyethylene material caused by high temperature during the sample preparation process, making the final test result more accurate.

[0021] (3) The present invention combines the density of the polyethylene test piece, the proportion of polyethylene and cellulose content with the fluorescence spectrum results for analysis, making the test results more accurate. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention is clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] Embodiment 1:

[0024] Detection of element content in polyethylene pellets:

[0025] (1) Use granular PE-1 as the raw material to be tested, accurately weigh and record the mass m of the granular PE-1 sample and the mass m0 of cellulose, and stir and blend for 10 minutes;

[0026] (2) The sample was prepared using a Hal Technology HTYP-20 laboratory tablet press, and the hot pressing conditions were a temperature of 100°C, a pre-pressing of 2.8 MPa, a boosting of 4.7 MPa, a pre-pressing time of 1 min, a boosting time of 2 min, and 6 exhaust times to obtain a polyethylene sheet;

[0027] (3) Measure the diameter, thickness and mass of the polyethylene sheet and calculate its density;

[0028] (4) The polyethylene sheet was tested by PANalytical DY3880 fluorescence spectrometer with a test power of 2.4 kW and a test time of 5 min;

[0029] According to the test results, combined with the formula A% = ρ / ρ0×B×(1+m0 / m),

[0030] Where A is the element content in the actual polyethylene material; ρ is the density of the polyethylene sheet; ρ0 is the default density when the fluorescence spectrometer is tested; B is the element content shown in the fluorescence spectrometer test results; ρ0 is 1.0 g / cm 3 , CH2 content was calculated by difference method, and the results are shown in Table 1:

[0031] Table 1

[0032]

[0033]

[0034] Embodiment 2:

[0035] Test element content of granular polyethylene PE-2 samples:

[0036] (1) Accurately weigh and record the mass m of the pelletized PE-2 sample and the mass m0 of cellulose, and blend them by stirring for 10 min.

[0037] (2) A Hal Technology HTYP-20 laboratory tablet press was used for sample preparation. The hot pressing conditions were temperature 110°C, pre-pressing 3.0 MPa, boosting 5.0 MPa, pre-pressing time 2 min, boosting time 4 min, and exhaust times 10 times to obtain polyethylene sheets.

[0038] (3) Measure the diameter, thickness and mass of the polyethylene sheet, and calculate its density.

[0039] (4) Testing: The polyethylene sheet was tested by a PANalytical DY3880 fluorescence spectrometer with a test power of 2.4 kW and a test time of 10 min.

[0040] According to the test results, combined with the formula A% = ρ / ρ0×B%×(1+m0 / m), the element content of the PE-2 sample was obtained, where ρ0 is 1.0 g / cm 3 , CH2 content was calculated by difference method, and the results are shown in Table 2:

[0041] Table 2

[0042]

[0043]

[0044] Embodiment 3:

[0045] Test element content of powder PE-3 sample:

[0046] (1) Accurately weigh and record the mass m of the PE-3 sample and the mass m0 of the cellulose, and blend them by stirring for 10 min.

[0047] (2) A Hal Technology HTYP-20 laboratory tablet press was used for sample preparation. The hot pressing conditions were temperature 120°C, pre-pressing 2.9 MPa, boosting 4.8 MPa, pre-pressing time 2 min, boosting time 3 min, and exhaust times 8 times to obtain polyethylene sheets.

[0048] (3) Measure the diameter, thickness and mass of the polyethylene sheet, and calculate its density.

[0049] (4) The polyethylene sheet was tested using a PANalytical DY3880 fluorescence spectrometer with a test power of 3.6 kW and a test time of 5 min.

[0050] According to the test results, combined with the formula A% = ρ / ρ0×B%×(1+m0 / m), the element content of the PE-3 sample was obtained, where ρ0 is 1.0 g / cm 3 , CH2 content was calculated by difference method, and the results are shown in Table 3:

[0051] Table 3

[0052]

[0053]

[0054] Embodiment 4:

[0055] Test element content of powder PE-4 sample:

[0056] (1) Accurately weigh and record the mass m of the PE-4 sample and the mass m0 of the cellulose, and blend them by stirring for 10 min.

[0057] (2) A Hal Technology HTYP-20 laboratory tablet press was used for sample preparation. The hot pressing conditions were temperature 100°C, pre-pressing 3.0 MPa, boosting 4.7 MPa, pre-pressing time 1 min, boosting time 4 min, and exhaust times 6 times to obtain polyethylene sheets.

[0058] (3) Measure the diameter, thickness and mass of the polyethylene sheet, and calculate its density.

[0059] (4) The polyethylene sheet was tested using a PANalytical DY3880 fluorescence spectrometer with a test power of 3.6 kW and a test time of 10 min.

[0060] According to the test results, combined with the formula A% = ρ / ρ0×B%×(1+m0 / m), the element content of the PE-4 sample was obtained, where ρ0 is 1.0 g / cm 3 , CH2 content was calculated by difference method, and the results are shown in Table 4:

[0061] Table 4

[0062]

[0063] Comparative Example 1:

[0064] Test element content of PE-1 pellet sample:

[0065] (1) A Hal Technology HTYP-20 laboratory tablet press was used for sample preparation. The hot pressing conditions were temperature 180°C, pre-pressing 2.8 MPa, boosting 4.7 MPa, pre-pressing time 1 min, boosting time 2 min, and exhaust times 6 times to obtain polyethylene sheets.

[0066] (2) The polyethylene sheet was tested using a PANalytical DY3880 fluorescence spectrometer with a test power of 2.4 kW and a test time of 5 min.

[0067] According to the test results, the element content of the PE-1 sample was obtained, and the CH2 content was calculated by the difference method. The results are shown in Table 5:

[0068] Table 5

[0069]

[0070] Comparative Example 2:

[0071] Test element content of powder PE-3 sample:

[0072] (1) A Hal Technology HTYP-20 laboratory tablet press was used for sample preparation. The hot pressing conditions were temperature 180°C, pre-pressing 2.9 MPa, boosting 4.8 MPa, pre-pressing time 2 min, boosting time 3 min, and exhaust times 8 times to obtain polyethylene sheets.

[0073] (2) Testing: The polyethylene sheet was tested by a PANalytical DY3880 fluorescence spectrometer with a test power of 3.6 kW and a test time of 5 min.

[0074] According to the test results, the element content of the PE-3 sample was obtained, and the CH2 content was calculated by the difference method. The results are shown in Table 6:

[0075] Table 6

[0076]

[0077] Comparative Example 3:

[0078] According to the standard SH / T 1829-2020 "Determination of trace elements in plastic polyethylene and polypropylene resins - Inductively coupled plasma emission spectrometry", the four PE samples PE-1, PE-2, PE-3 and PE-4 were tested for elements. The testing instrument was Agilent 5800 inductively coupled plasma spectrometer. The test results are shown in Table 7:

[0079] Table 7

[0080]

[0081]

[0082] From the above detection, it can be seen that Examples 1 to 4 adopt the element detection method of the present invention, while Example 3 adopts the ICP-OES method. The detection results of the two are very close, and the detection method of the present invention for PE samples is accurate and simpler.

[0083] From the results of Example 1 and Comparative Example 1, and Example 3 and Comparative Example 2, under the same test conditions, the sample preparation method of the present invention in which polyethylene and cellulose are blended to form a bond between the two gives more accurate results.

[0084] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for detecting the element content of polyethylene, characterized in that: The detection method comprises the following steps: (1) Sample preparation: Weigh the polyethylene sample and cellulose separately, record the mass, mix the two evenly, and hot-press them into polyethylene sheets; (2) Testing: The prepared polyethylene sheet is tested by fluorescence spectrometer; (3) Analysis: According to the following formula, the element content of polyethylene is obtained by combining the quality of polyethylene and cellulose, the density of polyethylene sheets and the results of fluorescence spectrum test: A%=ρ / ρ0×B%×(1+m0 / m) Where A is the element content in the actual polyethylene material; ρ is the density of the polyethylene sheet; ρ0 is the default density during fluorescence spectrometer testing; B is the element content shown in the fluorescence spectrometer test results; m0 is the cellulose mass; and m is the polyethylene sample mass.

2. The detection method according to claim 1, characterized in that: In the step (1), the polyethylene sample is powder or pellets.

3. The detection method according to claim 1, characterized in that: The mass ratio of the polyethylene sample to the cellulose in the polyethylene sheet prepared in the step (1) is m:m0=3-4:

1.

4. The detection method according to claim 1, characterized in that: The polyethylene sheet prepared in the step (1) is in the shape of a circular sheet with a diameter of 38 to 40 mm, a thickness of 2.0 to 2.5 mm, and a mass of 2.00 to 2.50 g.

5. The detection method according to claim 1, characterized in that: The hot pressing conditions in step (1) are: temperature 100-120° C., pre-pressing 2.8-3.0 MPa, boosting 4.7-5.0 MPa, pre-pressing time 1-2 min, boosting time 2-4 min, and exhaust times 6-10 times.

6. The detection method according to claim 1, characterized in that: The conditions for the fluorescence spectrometer test in step (2) are: test power 2.4-3.6 kW, test time 5-10 min.

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