A PP-based standard sample for testing impact resistance and density and its preparation method

Abstract

This invention relates to a PP-based standard sample for testing impact resistance and density, and its preparation method, belonging to the field of plastic physical testing technology. The PP-based standard sample for testing impact resistance and density of this invention comprises the following components by weight: 50-90 parts PP resin, 5-40 parts toughening agent, 25-40 parts filler, 1-10 parts compatibilizer, 0.1-5 parts antioxidant, and 0.1-1 parts processing aid; the PP resin has a melt flow rate of 12-16 g / 10 min at 230℃ and a 2.16 kg load. By selecting the content of each component, this invention enables the prepared PP-based standard sample to possess good impact resistance and density properties, as well as excellent stability and uniformity, reducing the influence of external factors such as temperature and humidity on the standard sample.

Description

Technical Field

[0001] This invention belongs to the field of plastic physical testing technology, specifically relating to a PP-based standard sample for testing impact resistance and density and its preparation method. Background Technology

[0002] Impact performance refers to a material's ability to resist impact loads. It is primarily used to determine a material's brittleness and toughness, and is one of the important performance indicators for evaluating material properties. Density is a measure of mass within a specific volume, calculated by dividing the mass of an object by its volume. Density can be used to identify the materials that make up an object, determine whether an object is solid or hollow, and is one of the characteristics of a substance. In daily life, PP material is one of the five major general-purpose plastics, mainly due to its abundant supply, low price, excellent performance, and wide range of applications, leading to rapid growth in the automotive, machinery, and household sectors. Density balances and impact testers are devices used to evaluate the density and impact performance of materials. To obtain accurate test results, ensuring the accuracy of the testing machine is crucial. Therefore, it is necessary not only to regularly calibrate and periodically check the testing machine, but also to constantly monitor and evaluate the equipment's condition and standardize personnel operation. To improve the accuracy of test results, laboratories often optimize testing equipment or operating procedures, but this cannot fully evaluate the accuracy of the test results and has certain limitations.

[0003] To obtain accurate test results, factors beyond equipment condition and human operation also play a role. Currently, common density standard materials are liquids and metals. These two types of standard materials have high requirements for storage environment, as storage can affect the density standard value. Furthermore, the purchase cost of standard materials is relatively high, and the density values ​​of metals and liquids exhibit some polarization. For example, when the test medium is water, the density of a metal or liquid can only confirm the equipment's ability to detect the density of that metal or liquid; it is not very accurate for similar detection ranges. Therefore, samples with a typical density range for modified plastics are often used. The patent "A Standard Sample for Unnotched Impact Performance Testing and Its Preparation Method" describes a standard sample with good uniformity and stability during unnotched impact performance testing, suitable for inspecting and calibrating unnotched impact performance testing equipment. This patent mainly uses standard samples for unnotched impact performance testing. After the impact test, the sample cross-section is uneven, failing to meet the requirements of the density testing standard: the sample surface should be smooth and without depressions. In the immersion liquid, air bubbles may remain in the depressions on the sample surface, affecting the test results. Therefore, this sample cannot simultaneously guarantee density testing.

[0004] Density and impact testing require verification of equipment status and personnel operation to ensure the accuracy of test results. Currently, laboratories cannot identify anomalies in advance; verification is only carried out step-by-step by checking various parts of the equipment and personnel operations after an anomaly complaint occurs. This process is cumbersome and labor-intensive. However, periodic testing of samples to verify equipment and standardize personnel operation is simpler. It not only allows for the timely detection of equipment problems and operational errors but also helps trace the causes of test anomalies, serving as an effective means of daily equipment status and personnel supervision. However, there is currently a lack of a standard sample available on the market that can be used simultaneously for the pre-testing inspection and calibration of density and impact equipment, and for evaluating the consistency of test results between laboratories. Therefore, a homogeneous and stable standard sample needs to be prepared that can be used for both tests, saving verification costs and sample storage space. Provided its homogeneity and stability are confirmed, it can be used for inter-laboratory proficiency testing comparisons, internal laboratory accuracy verification of testing methods, instrument stability verification, quality control management, uncertainty assessment, and personnel competency evaluation. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a PP-based standard sample for testing impact resistance and density, as well as a method for its preparation.

[0006] To achieve the above objectives, the technical solution adopted by this invention is as follows: a PP-based standard sample for testing impact resistance and density, comprising the following components by weight: 50-90 parts PP resin, 5-40 parts toughening agent, 25-40 parts filler, 1-10 parts compatibilizer, 0.1-5 parts antioxidant, and 0.1-1 parts processing aid; wherein the PP resin has a melt flow rate of 12-16 g / 10 min at 230℃ and a 2.16 kg load. PP resin has a high cost-performance ratio and is abundant and readily available; the impact resistance and density of PP resin are stable and easy to adjust, making it easier to meet the needs of plastic impact resistance and density testing; the PP resin density standard sample has stronger weather resistance than the liquid density standard sample. ， Furthermore, it is perfectly suited for verifying plastic density testing. Therefore, this invention selects PP resin as the substrate to prepare standard samples for impact resistance and density.

[0007] In a preferred embodiment of the PP-based standard sample for testing impact resistance and density according to the present invention, the toughening agent is at least one of PE resin, POE resin, and SBS resin. The inventors of this application have discovered that the properties of PP material are greatly affected by temperature, and that PP material has poor weather resistance. By adding different fillers in a compound formulation, a standard sample can be obtained that can be used for both impact and density testing. This standard sample exhibits reduced shrinkage after molding and high impact resistance.

[0008] In a preferred embodiment of the PP-based standard sample for testing impact resistance and density according to the present invention, the weight ratio of PP resin to toughening agent is PP resin: toughening agent = 2 to 8: 1. Through extensive experiments, the inventors of this application have discovered that when the weight ratio of toughening agent to PP resin is PP resin: toughening agent = 2 to 8: 1, the prepared standard sample exhibits better stability and uniformity.

[0009] In a preferred embodiment of the PP-based standard sample for testing impact resistance and density according to the present invention, the filler is at least one of calcium carbonate, barium sulfate, and glass fiber. The filler is one of the main factors affecting the density and impact resistance of PP; therefore, the influence of the material's own properties on the sample needs to be considered when selecting the filler. Nano-calcium carbonate and long glass fibers have oleophilic and hydrophobic surfaces, good compatibility with resin, and improve the impact resistance and density properties of the standard sample, while also enhancing the sample's heat resistance, weather resistance, and water resistance. More preferably, the average particle size of the filler is 1–5 μm.

[0010] In a preferred embodiment of the PP-based standard sample for testing impact resistance and density according to the present invention, the average length of the glass fiber in the sample is 0.1 to 0.5 mm.

[0011] In a preferred embodiment of the PP-based standard sample for testing impact resistance and density according to the present invention, the compatibilizer is at least one of maleic anhydride-grafted polyethylene and maleic anhydride-grafted polypropylene. The inventors of this application have discovered that using at least one of maleic anhydride-grafted polyethylene and maleic anhydride-grafted polypropylene as a compatibilizer results in good dispersibility and prevents the aggregation of filler particles; maleic anhydride-grafted polyethylene and maleic anhydride-grafted polypropylene have appropriate compatibility with PP resin and fillers, and good thermal stability; the addition of maleic anhydride-grafted polyethylene and maleic anhydride-grafted polypropylene improves the flowability during molding and processing without affecting the sample's performance, and is non-toxic and low-cost.

[0012] In a preferred embodiment of the PP-based standard sample for testing impact resistance and density according to the present invention, the compatibilizer comprises maleic anhydride-grafted polyethylene and maleic anhydride-grafted polypropylene in a weight ratio of 1:1. The applicant's research has found that the compounding of maleic anhydride-grafted polyethylene and maleic anhydride-grafted polypropylene can increase the compatibility between the materials and improve the barrier effect against water penetration, thus providing a good shielding effect and reducing the impact of climate on the standard sample, thereby improving the weather resistance and stability of the product. Furthermore, when maleic anhydride-grafted polyethylene and maleic anhydride-grafted polypropylene are added in a weight ratio of 1:1 as a compatibilizer, the prepared standard sample exhibits good impact resistance and density properties, as well as high stability and uniformity.

[0013] In a preferred embodiment of the PP-based standard sample for testing impact resistance and density according to the present invention, the antioxidant is at least one of hindered phenolic antioxidants or phosphite antioxidants. The addition of antioxidants ensures the weather resistance and aging resistance of the standard sample, allowing it to be stored and used for a long time with minimal impact on test results. More preferably, the antioxidant is a mixture of antioxidant 1010 and antioxidant 168 in a weight ratio of 1:1-2.

[0014] The present invention also provides a method for preparing the PP-based standard sample for detecting impact resistance and density, comprising the following steps:

[0015] (1) Polypropylene resin, toughening agent, filler, compatibilizer, antioxidant and processing aid are sequentially fed into a high-speed mixer for mixing and stirring. After melting and mixing, the mixture is extruded and granulated, and then dried to obtain PP granules.

[0016] (2) Inject the PP granules into the PP-based standard sample for testing impact resistance and density.

[0017] In a preferred embodiment of the method for preparing PP-based standard samples for testing impact resistance and density according to the present invention, the apparatus for extrusion granulation after melt mixing is a twin-screw extruder; the twin-screw extruder has an aspect ratio of 25-50, a main extruder speed of 300-600 rpm, and a barrel temperature of 170-230℃; the injection molding temperature is 190-250℃, the pressure is 55-60 Bar, and the speed is 25-30%.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention provides a PP-based standard sample for testing impact resistance and density. By selecting the types of toughening agents, fillers, and compatibilizers, and by optimizing the weight ratio of toughening agents to PP resin and the content of compatibilizers, the prepared PP-based standard sample has good impact resistance and density properties. It can simultaneously meet the verification requirements of a 2.75J pendulum cantilever beam notched impact and the verification requirements of samples within the conventional density range of modified plastics. It also has excellent stability and uniformity, reducing the influence of external factors such as temperature and humidity on the standard sample. The PP-based standard sample for testing impact resistance and density of the present invention is simple to prepare, has good molding ability, and has wide adaptability, which can meet the requirements of different testing conditions in the standard. Detailed Implementation

[0019] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0020] The raw materials used in the embodiments and comparative examples of the present invention are described below, but are not limited to these materials:

[0021] PP resin 1: PP K9017, Formosa Plastics Co., Ltd., melt flow rate at 230℃ and 2.16kg load is 14.5g / 10min;

[0022] PP resin 2: PP HP500N, CNOOC Shell Petrochemicals Co., Ltd., melt flow rate of 12g / 10min at 230℃ and 2.16kg load;

[0023] PP resin 3: PP PPH-M16, Sino-Korean Petrochemical Co., Ltd., melt flow rate at 230℃ and 2.16kg load is 16g / 10min;

[0024] PP resin 4: PP K8009, SK Chemicals International Trading (Shanghai) Co., Ltd., melt flow rate of 7 g / 10 min at 230℃ and 2.16 kg load.

[0025] PP resin 5: PP 320 powder, Yueyang Xinghui New Material Co., Ltd., melt flow rate of 30g / 10min at 230℃ and 2.16kg load;

[0026] Toughening agent 1: PE, PE HD85612 IM, Sinopec Chemical Sales Co., Ltd. Central China Branch, melt flow rate of 7 g / 10 min under test conditions of 190℃ and 2.16 kg; styrene-butadiene-styrene block copolymer, melt flow rate of 2.5 g / 10 min under test conditions of 200℃ and 5 kg, specific grade: YH-792E, provided by Sinopec Chemical Sales Co., Ltd. Central China Branch; the weight ratio of PE resin to styrene-butadiene-styrene block copolymer in toughening agent 1 is 1:1;

[0027] Toughening agent 2: POE, POE ENGAGE 8137, DOWCHEMICAL PACIFIC LTD, melt flow rate of 15 g / 10 min under test conditions of 190℃ and 2.16 kg, specific grade; styrene-butadiene-styrene block copolymer, melt flow rate of 6 g / 10 min under test conditions of 200℃ and 5 kg, specific grade: YH-188, provided by Sinopec Baling Petrochemical Branch; the weight ratio of POE resin to styrene-butadiene-styrene block copolymer in toughening agent 2 is 1:1;

[0028] Filler 1: Commercially available barium sulfate product, with an average particle size of 1.8 μm;

[0029] Filler 2: The average length of the glass fiber is 2mm, and the density is 2.4-2.76g / cm³. 3 ;

[0030] Filler 3: The average length of the glass fiber is 5mm, and the density is 2.4-2.76g / cm³. 3 ;

[0031] Compatibilizer 1: Maleic anhydride grafted polyethylene, BYNEL41E871, DuPont, USA;

[0032] Compatibilizer 2: Maleic anhydride-grafted polypropylene, M9600, SK Korea;

[0033] Antioxidant: A mixture of hindered phenolic antioxidants and commercially available phosphite antioxidants, wherein the mass ratio of hindered phenolic antioxidants to phosphite antioxidants is 1:1, and the mixture is commercially available;

[0034] Processing aids: Dispersant: Oxidized polyethylene wax, commercially available; Lubricant: OW-2, commercially available; The mass ratio of the dispersant to the lubricant is 1:1.

[0035] Unless otherwise specified, the experimental methods used in the examples and comparative examples are conventional methods, and the materials and reagents used are commercially available unless otherwise specified; and the components used in the examples and comparative examples are consistent unless otherwise specified.

[0036] Examples 1-16, Comparative Examples 1-2

[0037] The composition of the PP-based standard samples used for testing impact resistance and density in Examples 1 to 16 of this invention is shown in Table 1 below.

[0038] The composition of the PP-based standard samples used for testing impact resistance and density in Comparative Examples 1 and 2 of this invention is shown in Table 2 below.

[0039] The preparation method of PP-based standard samples for testing impact resistance and density in Examples 1-16 and Comparative Examples 1-2 of this invention is as follows: Resin, toughening agent, filler, compatibilizer, antioxidant, and processing aid are weighed according to the specified proportions and sequentially added to a high-speed mixer for mixing and stirring. After uniform mixing, a premix is ​​obtained. The premix is ​​added to a twin-screw extruder, where the materials are fully melted and fused under the shearing and mixing action of the screws. After extrusion, granulation, and drying, PP granules are obtained. The obtained PP granules are then added to an injection molding machine to process into density standard samples. The extruder processing conditions are as follows: twin-screw extruder length-to-diameter ratio 25-40, main extruder speed 300-600 rpm, barrel temperature 170-230℃; the injection molding conditions are: injection temperature 190-250℃, pressure 55-60 Bar, and speed 25-30%.

[0040] Table 1 shows the composition of PP-based standard samples used in Examples 1-16 and Comparative Examples 1-2 for testing impact resistance and density.

[0041]

[0042]

[0043] Example of effect

[0044] Performance Testing: To verify the effectiveness of the plastic density and impact standard samples described in this invention, uniformity and stability tests were conducted on the products of each embodiment and comparative example. The test methods are as follows:

[0045] (1) Homogeneity test: According to CNAS-GL003-2018 "Guidelines for evaluating the homogeneity and stability of proficiency testing samples", one-way ANOVA was used to test the homogeneity among the test samples. Taking the product of Example 1 as an example, 10 groups of prepared Example 1 samples were randomly selected, and two standard samples were taken from each group. The standard samples were conditioned in a constant temperature and humidity chamber at (23±2)℃ and (50±5)%RH for 24 hours, and then tested according to the requirements of GB / T 1843-2008 cantilever beam notch test and GB / T 1033.1-2008 immersion method. Other examples and comparative samples were tested using the same method. According to the degree of freedom and significance level, the critical value of uniformity for each product is F0.05(9,10)=3.02. If the statistical value F<F0.05(9,10)=3.02, it is considered that there is no significant difference between groups and within groups, that is, the sample is uniform. The smaller the value, the more uniform the product. If the F value ≥ the critical value F0.05(9,10)=3.02, it indicates that the product is not uniform enough.

[0046] (2) Stability test: According to CNAS-GL003:2018 "Guideline for Evaluation of Homogeneity and Stability of Proficiency Testing Samples", the consistency between two means in the t-test method was used to test the stability of the sample. The homogeneity test data was used as one of the means. Twenty prepared samples were randomly selected at 15-day intervals. The standard sample was conditioned in a constant temperature and humidity chamber at (23±2)℃ and (50±5)%RH for 24 hours and then tested. The average value of this test data was used as the average value of another parallel group. The consistency between two means in the t-test method was used to test the stability of the sample. The homogeneity test data was used as one of the means. The t-values ​​of the products of each embodiment were calculated using the two average samples. If the t-value < the significance level t0.05(38) = 2.024, it indicates that the sample is stable.

[0047] The test results are shown in Tables 2-5.

[0048] Table 2

[0049]

[0050] Table 3

[0051]

[0052]

[0053] Table 4

[0054]

[0055] Table 5

[0056]

[0057]

[0058] As can be seen from Examples 1-16, the PP-based standard samples for testing impact resistance and density described in this invention exhibit good uniformity (F values ​​did not exceed the critical value) and stability. In the examples, the average length of the processed glass fibers was 0.1-0.5 mm. In Example 16, the average length of the glass fibers in the standard sample was 0.7 mm. As shown in Examples 6 and 16, when the average length of the glass fibers in the prepared standard sample is not between 0.1 and 0.5 mm, the uniformity and stability of the standard sample are poor. Based on the data from the examples and Comparative Examples 1-2, it is evident that products prepared using PP resin at 230°C, a 2.16 kg load, and a melt flow rate of 12-16 g / 10 min or higher exhibit very poor uniformity (F values ​​exceed the critical value), and the standard deviation in the stability test is significantly higher than that of the examples. Data from Examples 5 and 12-13 show that the uniformity and stability of the standard product are related to the type and content of the compatibilizer. When the compatibilizer is maleic anhydride-grafted polyethylene and maleic anhydride-grafted polypropylene in a weight ratio of 1:1, the obtained standard product has good uniformity and stability. Data from Examples 5 and 14-15 show that the uniformity and stability of the standard product are related to the weight ratio of the toughening agent to the PP resin. When the weight ratio of the toughening agent to the PP resin exceeds the range defined in this invention, the prepared standard product has poor uniformity and stability.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A PP-based reference sample for detecting impact resistance and density, characterized in that, The composition comprises the following components by weight: 50-90 parts of PP resin, 5-40 parts of toughening agent, 25-40 parts of filler, 1-10 parts of compatibilizer, 0.1-5 parts of antioxidant, and 0.1-1 part of processing aid; the PP resin has a melt flow rate of 12-16 g / 10 min at 230 ℃ under a load of 2.16 kg. The compatibilizer is maleic anhydride grafted polyethylene and maleic anhydride grafted polypropylene.

2. The PP based reference sample for detecting impact resistance and density according to claim 1, characterized in that, The toughening agent is at least one of PE resin, POE resin, and SBS resin.

3. The PP based reference sample for detecting impact resistance and density according to claim 1, characterized in that, The weight ratio of the PP resin to the toughening agent is PP resin:toughening agent=2-8:

1.

4. The PP based reference sample for detecting impact resistance and density according to claim 1, characterized in that, The filler is at least one of calcium carbonate, barium sulfate, and glass fiber.

5. The PP based reference sample for detecting impact resistance and density according to claim 4, characterized in that, The average length of the glass fiber in the sample is 0.1-0.5 mm.

6. The PP based reference sample for detecting impact resistance and density according to claim 1, characterized in that, The compatibilizer comprises maleic anhydride grafted polyethylene and maleic anhydride grafted polypropylene at a weight ratio of 1:

1.

7. The PP based reference sample for detecting impact resistance and density according to claim 1, characterized in that, The antioxidant is at least one of hindered phenolic antioxidant or phosphite antioxidant.

8. The method for preparing PP-based reference samples for impact and density testing according to any one of claims 1 to 7, characterized in that, The method comprises the following steps: (1) sequentially feeding polypropylene resin, toughening agent, filler, compatibilizer, antioxidant, and processing aid into a high-speed mixer for mixing and stirring, and then extruding and granulating after melting and mixing, and then drying to obtain PP granules; (2) injecting the PP granules to obtain the PP-based standard sample for impact resistance and density testing.

9. The method for preparing PP-based standard samples for testing impact resistance and density according to claim 8, characterized in that, The device for extruding and granulating after melting and mixing is a double-screw extruder; the length-diameter ratio of the double-screw extruder is 25-50, the rotation speed of the main machine is 300-600 rpm, and the barrel temperature is 170-230 ℃; the injection temperature is 190-250 ℃, the pressure is 55-60 Bar, and the speed is 25-30%. The device for extruding and granulating after melting and mixing is a double-screw extruder; the length-diameter ratio of the double-screw extruder is 25-50, the rotation speed of the main machine is 300-600 rpm, and the barrel temperature is 170-230 ℃; the injection temperature is 190-250 ℃, the pressure is 55-60 Bar, and the speed is 25-30%.

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