A standard sample for detecting notched impact performance and a preparation method thereof

Abstract

The application discloses a standard sample for non-notched impact performance detection and a preparation method thereof, and relates to the technical field of standard samples. The standard sample for non-notched impact performance detection comprises the following components in parts by weight: 60-90 parts of copolymerized polypropylene, 1-9 parts of a toughening agent, 5-20 parts of inorganic fillers, 0.1-2 parts of an antioxidant and 0.05-1 parts of a coupling agent. The standard sample has good uniformity and stability when non-notched impact performance detection is carried out, and is suitable for testing and calibrating the state of a non-notched impact performance detection device.

Description

Technical Field

[0001] This invention relates to the field of standard sample technology, and in particular to a standard sample for unnotched impact performance testing and its preparation method. Background Technology

[0002] Impact properties refer to a material's ability to resist impact loads. Impact strength is primarily used to determine a material's brittleness and toughness. In engineering applications, impact strength is an important performance indicator and is widely used in material performance evaluation.

[0003] Impact testing machines are used to evaluate the impact performance of materials. The accuracy of sample testing depends on the accuracy of the equipment, making its accuracy crucial. Currently, equipment calibration mainly relies on annual measurements, primarily checking equipment parameters. However, these measurements have long cycles, making it impossible to monitor and evaluate the equipment's status continuously. International standards organizations use V-notch standard samples to calibrate impact testing machines. Therefore, impact standards can validate impact testing machines and be used for routine equipment monitoring. Furthermore, standards not only calibrate equipment but also serve as proficiency testing samples, allowing for consistency comparisons of personnel operations and personnel supervision.

[0004] There are currently some studies on the preparation of impact test specimens and proficiency testing samples, such as:

[0005] CN1074543C discloses a method for manufacturing a notched impact calibration sample for calibrating an impact testing machine. The chemical composition (weight %) of the steel material is C 0.02-0.09, S < 0.01, with the remainder being Fe and unavoidable impurities. The steel material is smelted, cast, and rolled to obtain a steel plate of the required thickness. The smaller portion of the middle of the steel plate along the width direction is then prepared as a standard sample.

[0006] The plastic impact testing standard specifies the selection of different pendulums based on different absorbed energies. Therefore, equipment calibration requires various standard samples. Plastic injection molding is low-cost and high-volume, while metal standard samples have complex processing and higher costs. Furthermore, metal generally has a higher impact absorption capacity, making metal standard samples unsuitable for verifying plastic impact testing machines. Notched impact samples, due to their notches, experience stress concentration during testing, resulting in lower impact strength. This means that equipment calibration cannot cover the entire range. Unnotched impact samples, on the other hand, have higher impact strength. Therefore, unnotched impact standards can be used to calibrate and verify the maximum pendulum weight. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a standard sample for unnotched impact performance testing and its preparation method.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A standard sample for unnotched impact performance testing, the standard sample comprising the following components in parts by weight: 60-90 parts of copolymer polypropylene (PP), 1-9 parts of toughening agent, 5-20 parts of inorganic filler, 0.1-2 parts of antioxidant, and 0.05-1 parts of coupling agent.

[0010] Currently, there are few unnotched impact standard specimens available on the market. This invention uses commonly used plastic PP as the base material. The copolymer PP with a small amount of ethylene monomer introduced into its structure has better dimensional stability than homopolymer PP. By adding toughening agents and fillers and controlling the amount of each component, the impact strength of the prepared PP material can span different ranges, which can meet the requirements of several pendulums used in conventional unnotched impact performance testing of plastics. It also has good uniformity and long-term stability, making it suitable for inspecting the condition of unnotched impact performance testing equipment and evaluating the testing skills of operators.

[0011] Preferably, the copolymer polypropylene, measured according to standard GB / T 3682.1-2018 at 230℃ and 2.16 kg, has a melt flow rate of 5~55 g / 10 min. Copolymer polypropylene, due to the introduction of a small amount of ethylene monomer into its structure, exhibits better dimensional stability than homopolymer polypropylene, thus resulting in more stable impact strength of the standard samples with polypropylene substrate. A higher melt flow index (MFI) indicates better flow properties, but a very high MFI leads to relatively poor impact resistance. By controlling the melt flow rate of the polypropylene resin, PP-based standard samples for unnotched impact performance testing can be obtained with better uniformity and stability.

[0012] Preferably, the toughening agent is at least one of polyethylene (PE), POE, and ethylene propylene diene monomer (EPDM) rubber.

[0013] More preferably, the toughening agent is a compound of polyethylene and POE; the weight ratio of PE to POE in the compound is (2.4~3.5):1. PE has good impact resistance, but low tensile strength, and relatively poor creep resistance and aging resistance; POE has good compatibility with PP resin and good stress transfer ability, which can significantly improve the toughness of the composite material, but it will have an adverse effect on tensile strength and flexural strength. The inventors of this application have confirmed through experiments that there is a synergistic effect between POE and PE, and the toughening effect is significantly better than that of POE or PE alone on PP. When the two are compounded in the above ratio, the prepared polypropylene composite material has better uniformity and stability.

[0014] Preferably, the polyethylene has a melt flow rate of 2~20 g / 10 min measured at 190℃ and 2.16 kg according to standard GB / T 3682.1-2018; the POE has a melt flow rate of 0.5~15 g / 10 min measured at 190℃ and 2.16 kg according to standard GB / T 3682.1-2018.

[0015] Preferably, the inorganic filler is at least one selected from talc, nano-calcium carbonate, mica, and wollastonite; the coupling agent is a titanate coupling agent. Titanate coupling agents can improve the dispersibility of the filler and enhance the mechanical properties and anti-aging properties of the material.

[0016] Preferably, the inorganic filler is a compound of talc and nano-calcium carbonate; the weight ratio of talc to nano-calcium carbonate in the compound is (1.5~2.5):1. Talc can increase dimensional stability and has good dispersibility; nano-calcium carbonate also helps to improve the dimensional stability of the product and can improve the processing performance of plastics. The inventors of this application have experimentally verified that when the weight ratio of talc to nano-calcium carbonate meets the above-mentioned limitations, the prepared polypropylene composite material has better uniformity and stability, and is more suitable as a standard sample for unnotched impact performance testing.

[0017] Preferably, the antioxidant is at least one of hindered phenolic antioxidants and phosphite antioxidants. The hindered phenolic antioxidant is antioxidant 1010, antioxidant 1076, etc.; the phosphite antioxidant is antioxidant 168, antioxidant 618, etc. More preferably, the antioxidant is a compound of hindered phenolic antioxidant and phosphite antioxidant in a weight ratio of (0.8~1.2):1. The hindered phenolic antioxidant and phosphite antioxidant have a synergistic effect, which can give the prepared polypropylene composite material long-lasting antioxidant properties.

[0018] Meanwhile, the present invention also discloses a method for preparing the standard sample, the method comprising the following steps:

[0019] (1) Mix all components evenly according to the proportions;

[0020] (2) Add the uniformly mixed material into a twin-screw extruder for extrusion granulation;

[0021] (3) The granules are injection molded into a sample to obtain the standard sample.

[0022] Preferably, in step (1), a high-speed mixer is used for mixing for 1-3 minutes; in step (2), the specific process parameters of the twin-screw extruder are as follows: extruder temperature is 80-250℃, main machine speed is 250-600 rpm; the length-to-diameter ratio of the twin-screw extruder is (35-45):1; in step (3), the injection molding conditions are: injection molding machine temperature is 180-250℃, injection pressure and holding pressure are 40-60 bar, and the back pressure gauge is controlled at 1-2 MPa. After injection molding, the mixture is conditioned under standard conditions (temperature 23±2℃, humidity 50±5%) for at least 24 hours before testing.

[0023] Compared to existing technologies, the advantages of this invention are as follows: This invention provides laboratories engaged in plastic testing with standard samples for routine evaluation of unnotched impact testing systems, which can help increase the frequency of daily equipment monitoring. By selecting the components of toughening agents and inorganic fillers, the uniformity and long-term stability of the standard samples are greatly improved. Detailed Implementation

[0024] 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.

[0025] The materials used in the examples and comparative examples are as follows:

[0026] Copolymer polypropylene 1: According to standard GB / T 3682.1-2018, under test conditions of 230℃ and 2.16kg, the melt flow rate is 55g / 10min, PP EP648U, provided by CNOOC Shell Petrochemicals Co., Ltd.;

[0027] Copolymer Polypropylene 2: According to standard GB / T 3682.1-2018, under test conditions of 230℃ and 2.16kg, the melt flow rate is 30g / 10min. PP EP548R, Sinopec Chemical Sales (Tianjin) Co., Ltd.

[0028] Copolymer polypropylene 3: According to standard GB / T 3682.1-2018, the melt mass flow rate measured at 230℃ and 2.16kg is 8g / 10min, PP SP179 (Lanzhou Chemical), Southwest Chemical Sales Branch of China National Petroleum Corporation;

[0029] Copolymer polypropylene 4: According to standard GB / T 3682.1-2018, under test conditions of 230℃ and 2.16kg, the melt flow rate is 100g / 10min, PP7945E1, Chengdu Kingfa Non-Bonded Factory;

[0030] Homopolymer polypropylene: The melt mass flow rate measured at 230℃ and 2.16kg according to standard GB / T 3682.1-2018 is 25g / 10min. PP Z30S, Dushanzi Petrochemical Branch of China National Petroleum Corporation.

[0031] Polyethylene 1: According to standard GB / T 3682.1-2018, the melt mass flow rate measured at 190℃ and 2.16kg is 7g / 10min, PE HD85612 IM, China Petrochemical Chemical Sales Co., Ltd. Central China Branch;

[0032] Polyethylene 2: According to standard GB / T 3682.1-2018, the melt mass flow rate measured at 190℃ and 2.16kg is 2g / 10min; LLDPE DFDA-7042, Sichuan Zhongmeida Plastics Co., Ltd.;

[0033] Polyethylene 3: According to standard GB / T 3682.1-2018, the melt mass flow rate measured at 190℃ and 2.16kg is 20g / 10min. LLDPE DNDA8320 Daqing Petrochemical, Southwest Chemical Sales Branch of China National Petroleum Corporation;

[0034] Polyethylene 4: According to standard GB / T 3682.1-2018, the melt mass flow rate measured at 190℃ and 2.16kg is 1.0g / 10min, LLDPE ENABLE2010PA, Guangdong Kingfa Science & Technology Co., Ltd.

[0035] POE 1: The melt mass flow rate measured at 190℃ and 2.16kg according to standard GB / T 3682.1-2018 is 1.2g / 10min. POE DF810, Mitsui Group, Japan;

[0036] POE 2: The melt mass flow rate measured at 190℃ and 2.16kg according to standard GB / T 3682.1-2018 is 0.5g / 10min. POE DF605, Mitsui Group, Japan;

[0037] POE 3: The melt mass flow rate measured at 190℃ and 2.16kg according to standard GB / T 3682.1-2018 is 15g / 10min. POE ENGAGE 8137, DOW CHEMICAL PACIFIC LTD.;

[0038] POE 4: The melt mass flow rate measured at 190℃ and 2.16kg according to standard GB / T 3682.1-2018 is 35g / 10min. POE DF7350, Mitsui Group, Japan;

[0039] Talc: Commercially available;

[0040] Nano calcium carbonate: Commercially available;

[0041] Coupling agent 1: Bis(dioctyloxypyrophosphate) ethylene titanate, commercially available;

[0042] Coupling agent 2: Silane coupling agent KH550, commercially available;

[0043] Antioxidants: Antioxidant 1010, commercially available; Antioxidant 168, commercially available; the weight ratio of Antioxidant 1010 to Antioxidant 168 is 1:1.

[0044] The talc, nano-calcium carbonate, coupling agent 1, coupling agent 2, and antioxidant used in the examples and comparative examples are all the same substance.

[0045] Examples 1-10

[0046] Examples of the standard samples described in this invention, specifically Examples 1-10, are shown in Table 1, and their preparation methods are as follows:

[0047] (1) Add each component to the high-speed mixer according to the proportion and mix for 2 minutes to obtain the premix;

[0048] (2) The premixed material is added to a twin-screw extruder and extruded to granulate to obtain granules; the specific process parameters of the twin-screw extruder are as follows: Zone 1 temperature 80-120℃, Zone 2 temperature 190-210℃, Zone 3 temperature 210-220℃, Zone 4 temperature 210-220℃, Zone 5 temperature 210-220℃, Zone 6 temperature 210-220℃, Zone 7 temperature 210-230℃, Zone 8 temperature 210-230℃, Zone 9 temperature 210-230℃, main machine speed 400 rpm; the length-to-diameter ratio of the twin-screw extruder is 40:1;

[0049] (3) Place the granules into the injection molding machine and inject them into a sample strip; the specific parameters of the injection molding machine are as follows: the injection molding machine temperature is 200℃, the injection pressure and holding pressure are 50 bar, and the back pressure gauge is controlled at 1 MPa;

[0050] (4) After adjusting for 24 hours under standard conditions, perform the test again.

[0051] Comparative Example 1

[0052] Comparative Example 1 is a polypropylene composite material, the formulation of which is shown in Table 1, and the preparation method is the same as that of Example 1.

[0053] Table 1 (parts by weight)

[0054]

[0055] Examples 11-13

[0056] The difference between Examples 11-13 and Example 2 of the standard samples described in this invention is only that the types of copolymer polypropylene are different, namely copolymer polypropylene 2-4.

[0057] Examples 14-16

[0058] The only difference between Examples 14-16 and Example 2 of the standard sample described in this invention is that the types of polyethylene are different, namely polyethylene 2-4.

[0059] Examples 17-19

[0060] The difference between Examples 17-19 and Example 2 of the standard sample described in this invention is only that the types of POE are different, namely POE 2-4.

[0061] Example 20

[0062] This invention provides an embodiment of the standard sample. The difference between this embodiment and Embodiment 2 is that the coupling agent is different; this embodiment is a silane coupling agent, KH550.

[0063] Comparative Example 2

[0064] A polypropylene composite material, the only difference between the polypropylene composite material and Example 2 is that homopolymer polypropylene is used instead of copolymer polypropylene.

[0065] The performance of the examples and comparative examples was tested according to the standard GB / T 1843-2008. The unnotched impact performance test was carried out in 10 batches, with two samples tested in each batch. The test results are recorded in Table 2.

[0066] Table 2 (Impact Strength kJ / m) 2 )

[0067]

[0068] The homogeneity of the samples was verified using the requirements and methods for homogeneity testing in section 4.1 and section 4.2 of the "CNAS-GL03-2018 Guidelines for Evaluation of Homogeneity and Stability of Proficiency Testing Samples". The results are shown in Table 3.

[0069] Table 3

[0070]

[0071] As shown in Table 3, the F values ​​of Examples 1 to 20 are all less than the critical value F. 0 .05(9 ,10) (3.02) This result indicates that the polypropylene composite material prepared according to the formulation of this invention showed no significant differences between samples during unnotched impact performance testing, demonstrating good homogeneity. Specifically, the F-values ​​of Examples 1-5, 11-12, 14-15, and 17-18 were all less than 1.4, indicating relatively better homogeneity. In Example 6, only polyethylene was used as a toughening agent, resulting in relatively poor homogeneity; in Examples 8-10, the weight ratio of talc powder and nano-calcium carbonate was not within the range of (1.5-2.5):1, leading to slightly poorer homogeneity.

[0072] Examples 13, 16, and 19 show that the melt flow rates of polypropylene, PE, and POE are outside the preferred range, resulting in relatively high F-values ​​for the prepared standard samples. This indicates that the melt flow rate of polypropylene, PE, and POE significantly affects the homogeneity of the standard samples. In Example 20, a silane coupling agent was used, which, compared to titanate coupling agents, also resulted in relatively poorer homogeneity of the prepared standard samples.

[0073] In Comparative Example 1, the addition of inorganic filler exceeded 20 parts, resulting in relatively poor dispersion in the system and affecting the uniformity of the polypropylene composite material. Comparative Example 2 used homopolymer polypropylene, which, compared to copolymer polypropylene, exhibited even worse uniformity during unnotched impact performance testing.

[0074] After the standard samples were placed for 180 days, the impact performance was tested according to the standard GB / T 1843-2008. 20 samples were taken and divided into 10 groups. 2 samples were tested in each group. The average value of the test results was recorded in Table 4.

[0075] Table 4 (Impact Strength kJ / m) 2 )

[0076]

[0077] The stability of the samples was tested using the t-test method in the "CNAS-GL03-2018 Guidelines for the Evaluation of Homogeneity and Stability of Proficiency Testing Samples". The homogeneity test data was used as one mean, and the average of the test data from 20 samples after 180 days was used as the other mean. The results are shown in Table 5.

[0078] Table 5

[0079]

[0080] The test results above show that the t-values ​​for Examples 1 to 20 are all less than the critical value t. 0.05(20+20-2) (2.024) This result indicates that the polypropylene composite material prepared according to the formulation of this invention shows no significant difference between samples over different time spans during unnotched impact performance testing, demonstrating good stability. The performance differences between the examples and comparative examples are similar to the homogeneity test results. Among them, Example 7, which used only POE as a toughening agent, showed relatively better homogeneity test results, but slightly worse stability test results.

[0081] 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 standard sample for notched impact property detection, characterized by, Comprise the following ingredients by weight: copolymerized polypropylene 60~90 parts, toughening agent 1~9 parts, inorganic filler 5~20 parts, antioxidant 0.1~2 parts and coupling agent 0.05~1 parts; The toughening agent is a compound of polyethylene and POE; the weight ratio of polyethylene and POE in the compound is (2.4~3.5):1; The copolymerized polypropylene has a melt mass flow rate of 5~55g / 10min measured at 230℃ and 2.16kg according to standard GB / T 3682.1-2018; The polyethylene has a melt mass flow rate of 2~20g / 10min measured at 190℃ and 2.16kg according to standard GB / T 3682.1-2018; the POE has a melt mass flow rate of 0.5~15g / 10min measured at 190℃ and 2.16kg according to standard GB / T 3682.1-2018.

2. The standard sample of claim 1, wherein, The inorganic filler is at least one of talcum powder, nano calcium carbonate, mica and wollastonite; the coupling agent is a titanate coupling agent.

3. The standard sample of claim 2, wherein, The inorganic filler is a compound of talcum powder and nano calcium carbonate; the weight ratio of talcum powder and nano calcium carbonate in the compound is (1.5~2.5):

1.

4. The standard sample of claim 1, wherein, The antioxidant is at least one of hindered phenolic antioxidant and phosphite antioxidant.

5. The standard sample of claim 4, wherein, The antioxidant is a compound of hindered phenolic antioxidant and phosphite antioxidant with a weight ratio of (0.8~1.2):

1.

6. A method of preparing a standard sample according to any one of claims 1 to 5, characterized in that, The method comprises the following steps: (1) uniformly mix the components according to the ratio; (2) extrude and granulate the uniformly mixed material in a double-screw extruder; (3) injection mold the granules into a sample bar to obtain the standard sample.

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