Device and method for measuring high-temperature contact angle of viscous resin

Abstract

The invention discloses a device and a method for measuring a high-temperature contact angle of viscous resin, and relates to the field of testing of physical properties of materials. In order to overcome the problems that the resin is difficult to absorb and drop due to high viscosity, the wiredrawing phenomenon is generated, the measurement is difficult and the like, a heating device is additionally arranged on the basis of a traditional contact angle tester, and a common glass injector is changed into a stainless steel injector, so that the measurement of the high-temperature contact angle is realized. According to the invention, by designing the sample preparation mode and changing the drop volume and the trigger mode, the contact angle between the resin and the fiber woven cloth can be accurately measured, and the wettability of the resin to the fiber woven cloth is better represented.

Description

Technical Field

[0001] The invention relates to the field of material physical property testing, and in particular to a device and method for measuring the high-temperature contact angle of a viscous resin. Background Art

[0002] As the call for lightweighting continues to grow, the use of composite materials in various fields has also increased year by year. Among them, the interface of composite materials, as a key influencing factor of the mechanical properties of materials, has always been the focus of many researchers. The interface of composite materials is inseparable from the study of the wetting properties of the resin matrix on the fiber reinforcement. If the fiber reinforcement and the resin matrix cannot be completely and well combined, the composite material will contain more defects and holes, causing stress concentration and reduced load transfer capacity, which in turn affects the mechanical properties of the composite material, especially the shear properties. Therefore, determining the wetting properties of the resin matrix on the fiber reinforcement is a key link in studying the interface properties of composite materials.

[0003] Contact angle is one of the indicators to measure wettability. The sessile drop method is the most widely used method for contact angle testing. It is often used to characterize the wettability between water or other reagents and solid planar materials. The contact angle is measured by making tangents through a microscope and image software. According to the results of the literature standard survey, the reference standards for contact angle measurement are mainly GB / T 24368-2009, GB / T 30693-2014, etc., which are mainly for the measurement of contact angles between water and glass and plastic films. However, the resin matrix required for the preparation of composite materials has problems such as high viscosity, poor fluidity, and difficult sampling. There are still few studies on the contact angle test of such materials.

[0004] Chongqing University once used the Wilhelmy hanging plate method to measure the dynamic contact angle between a single glass fiber and epoxy resin, but this method is more suitable for fibers with greater hardness and can only measure the contact angle between a single fiber and the resin, which is quite different from the actual preparation process of composite materials. With the surge in demand for composite materials, the compatibility and wettability of the resin matrix and fiber reinforcement materials in the preparation process of composite materials cannot be ignored. Therefore, accurately measuring the contact angle between the resin matrix and the fiber reinforcement is one of the problems that need to be solved urgently. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and propose a high-temperature contact angle measurement device and method for viscous resins. By designing a high-temperature syringe and a heating device, matching the resin sample preparation method with the contact angle software parameter setting, a high-temperature contact angle measurement method for resin matrix and fiber reinforced material is established.

[0006] The technical solution adopted by the present invention to solve the above problems is:

[0007] A high-temperature contact angle measuring device for viscous resin comprises a light source, a liquid injection pump fixing frame, a liftable sample stage, a microscope and a computer; it also comprises a high-temperature syringe and a heating device. The high-temperature syringe can be detachably mounted on the liquid injection pump fixing frame and is used for loading and pushing resin sample liquid; the heating device is used for controllably heating the high-temperature syringe to turn the resin sample in the high-temperature syringe into liquid.

[0008] Furthermore, the high-temperature syringe comprises a needle, a syringe, a piston and a sealing rubber ring located at the bottom end of the piston. The needle, the syringe and the piston of the high-temperature syringe are made of stainless steel.

[0009] Furthermore, the heating device comprises a temperature control box and a heating sleeve, the heating sleeve is jacketed on the high-temperature syringe for heating the resin sample, and the temperature control box is connected to the heating sleeve for controlling the heating temperature.

[0010] A method for measuring the high temperature contact angle of a viscous resin is implemented based on the above device and comprises the following steps:

[0011] 1) Place the resin sample in a beaker and then place it in a water bath for heating until the resin sample has good fluidity;

[0012] 2) Immediately use a high-temperature syringe to absorb the resin liquid, install the heating sleeve on the periphery of the high-temperature syringe, and then install them together on the injection pump fixing frame and lock them, turn on the temperature control box, heat the heating sleeve to the target temperature and maintain a constant temperature;

[0013] 3) Perform pre-injection operation on the high-temperature syringe to exhaust the gas in the needle until the resin liquid is about to flow out; place the fiber cloth on the liftable sample table and lay it flat, ready for testing;

[0014] 4) Adjust the height of the liftable sample table and the high-temperature syringe so that they appear simultaneously in the video monitoring interface of the computer, adjust the reference line on the computer to be consistent with the plane of the fiber cloth, input the drip volume parameter and extrude the resin liquid, select the trigger mode and shoot in real time, move the high-temperature syringe downward until the resin liquid contacts the fiber cloth, then move the needle upward, and start to automatically measure the contact angle after the resin liquid drips;

[0015] 5) When the resin liquid is dripped and spread on the fiber cloth, ten photos are taken continuously to record the contact angle during the spreading process and calculate the average value.

[0016] Furthermore, when the fiber cloth is placed in step 3), its edge on one side close to the microscope should be vertically aligned with the needle of the high-temperature syringe.

[0017] Furthermore, in step 4), the drop volume parameter is selected to be 6-8 μL.

[0018] Furthermore, the triggering mode selected in step 4) is sequential triggering or delayed triggering.

[0019] Furthermore, when the delayed trigger mode is selected in step 4), the extended time is set to 0.5-2s.

[0020] Furthermore, after step 5) is completed, an organic solvent is selected to clean the high-temperature syringe several times until it is clean.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The present invention can be applied to the contact angle test of various resins and fiber cloths, and has stronger versatility;

[0023] (2) Add a sealing rubber ring to the stainless steel syringe to reduce the inhalation of air and affect the accuracy of the test;

[0024] (3) The present invention determines the appropriate drop volume, avoiding the phenomenon that the drop is too small and the resin viscosity is too high to drip, and also reduces the measurement inaccuracy caused by the large drop volume and gravity.

[0025] (4) The present invention selects a delayed trigger measurement method to avoid the "drawing" phenomenon generated during the dripping of resin droplets and affecting the measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The figure is a schematic diagram of the structure of a high-temperature contact angle measurement device for viscous resin.

[0027] In the figure: 1-light source, 2-liquid injection pump fixing frame, 3-high temperature syringe, 4-liftable sample stage, 5-microscope, 6-computer, 7-heating sleeve, 8-temperature control box.

[0028] Figure 2 Schematic diagram of the structure of the high-temperature injector.

[0029] In the figure: 9-needle, 10-syringe, 11-piston, 12-rubber ring.

[0030] Figure 3 Schematic diagram of sample placement.

[0031] Figure 4 Contact angle measurement results before test parameter optimization.

[0032] Figure 5 Contact angle measurement results after optimizing test parameters. DETAILED DESCRIPTION

[0033] In order to make the various technical features and advantages or technical effects in the above technical solutions of the present invention more obvious and easy to understand, they are described in detail below with reference to the accompanying drawings.

[0034] Example:

[0035] This embodiment specifically implements the present invention to provide a method for measuring the high temperature contact angle of a viscous resin, and measures the contact angle of the viscous resin to characterize the wettability of the resin on the fiber cloth. Figure 1 The high-temperature contact angle measurement device for a viscous resin shown is implemented. The device is the same as a conventional fully automatic video contact angle tester in that it includes a light source 1, an injection pump fixture 2, a syringe, a liftable sample table 4, a microscope 5 and a computer 6. However, conventional testers are only suitable for contact angle measurements between solid materials and water or other reagents at room temperature. In order to achieve the high-temperature contact angle measurement of viscous resins, the present invention makes improvements on the basis of the original tester: first, a heating device is added, including a heating sleeve 7 and a temperature control box 8, which can achieve heating of not less than 200°C and constant temperature control. The size of the heating sleeve matches the high-temperature syringe to achieve good heat transfer. Second, the ordinary glass syringe is replaced with a high-temperature syringe 3, made of stainless steel, and its structure is as follows: Figure 2 As shown, it mainly consists of a needle 9, a syringe 10, a piston 11 and a rubber ring 12 (located in the syringe) at the bottom of the piston. The rubber ring 11 can improve the sealing of the syringe and prevent air from entering when the resin is absorbed. The outer diameter of the selected needle should be larger than the contact angle of water. The outer diameter of the needle commonly used in the test is 0.52mm. A needle with an outer diameter of more than 1mm can be selected. In this embodiment, the outer diameter of the stainless steel needle selected is 1.26mm according to the viscosity of the resin.

[0036] The steps of this method for measuring the high temperature contact angle of viscous resin are as follows:

[0037] 1) Take a certain amount of epoxy resin sample, put it into a beaker, and then place it in a water bath for water bath heating, set the temperature to 50°C, and keep warm for 20 minutes, so that the epoxy resin sample has good fluidity and can be easily absorbed by the stainless steel syringe. If the fluidity is poor, continue to increase the water bath temperature and extend the insulation time. In other embodiments, the heating temperature can be set according to the type of resin sample, generally in the range of 50 to 90°C.

[0038] 2) Use a high-temperature syringe to slowly absorb the resin, clean the residual resin on the needle with cotton, install the heating sleeve on the periphery of the high-temperature syringe, and then install them together in the injection pump fixing frame and lock them, turn on the temperature control box of the heating device, set the temperature to 50°C, quickly heat it to the target temperature and keep it at a constant temperature for 10-20 minutes.

[0039] 3) Perform a pre-injection operation on the high-temperature syringe to exhaust the gas in the needle until the epoxy resin liquid flows out; place the fiber cloth on the sample table and lay it flat, with the outer edge of the fiber cloth sample vertically aligned with the high-temperature syringe needle (such as Figure 3 As shown), the microscope can focus on the fiber cloth sample and the resin droplet at the same time to ensure clear photos during contact angle testing and increase test reliability. After the focus is clear, prepare for the test.

[0040] 4) Adjust the height of the liftable sample stage and the high-temperature syringe so that they appear simultaneously in the video monitoring interface of the computer software. Adjust the baseline in the software to keep it consistent with the plane of the fiber cloth, set the relevant parameters and conduct the contact angle test: input the appropriate drop volume of 7μL, which is necessary to ensure that the viscous resin drips out from the needle, and to avoid the inaccuracy of the measurement results due to gravity caused by the excessive drop volume. Click the drop, the needle squeezes out the resin liquid, select the trigger mode and shoot in real time. The trigger mode should match the characteristics of the resin and be distinguished from reagents such as water. The selected trigger mode includes follow-up triggering and delayed triggering. The follow-up triggering: after the drop contacts the sample, when the needle moves upward, it is triggered instantly when it separates from the needle, and the software starts to automatically measure the angle. Delayed triggering: You can set an extended time to start measuring the contact angle at a specified time. Due to the viscous nature of the resin, after contacting the fiber cloth, when the needle moves upward, a long "wire drawing" phenomenon will appear. The droplet will not separate from the needle until the wire drawing reaches a certain degree. When triggered at this time, the droplet still has a long "tail", and the contact angle measurement is inaccurate. Therefore, it is necessary to set a delayed trigger to start automatic measurement after the droplet completely drips onto the fiber cloth. The delay time is determined by the viscosity of the resin and is generally set within the range of 0.5-2s. In this embodiment, the trigger mode selects a delayed trigger, the delay time is set to 1s, and real-time measurement is performed. Move the high-temperature syringe downward until the resin liquid contacts the fiber cloth and stops, then move the needle upward, and after 1s, the liquid completely drips and the contact angle is automatically measured.

[0041] 5) When the resin droplet falls on the fiber cloth and gradually spreads, the software takes ten photos in succession, records the contact angle of the spreading process and calculates the average value.

[0042] After the above measurements are completed, clean the high-temperature syringe, select acetone as the cleaning solvent, soak the resin in acetone to dissolve it, and then rinse it 2-3 times.

[0043] Comparative Example:

[0044] The contact angle between epoxy resin and fiber cloth was tested using unoptimized test parameters. The specific steps are as follows:

[0045] 1) This test method is based on the design of a fully automatic video contact angle tester. The high-temperature syringe used is made of stainless steel, and the outer diameter of the selected stainless steel needle is 1.26 mm.

[0046] 2) Take a certain amount of epoxy resin, put it into a beaker, and then place it in a water bath for water bath heating. The temperature is set to 50°C and kept warm for 20 minutes. The epoxy resin sample has good fluidity.

[0047] 3) Use a high-temperature syringe to slowly absorb the resin, clean the residual resin on the needle with cotton, install the heating sleeve on the periphery of the high-temperature syringe, and then install them together in the injection pump fixing frame and lock them, turn on the heating device, set the temperature to 50°C, quickly heat it to the target temperature and keep it at a constant temperature for 10-20 minutes.

[0048] 4) Fill the high-temperature syringe with liquid and expel the gas in the needle until epoxy resin liquid flows out; place the fiber cloth on the sample table and flatten it, aligning the outer edge of the fiber cloth with the syringe needle so that the microscope can focus on the fiber cloth sample and the resin droplet at the same time. After the focus is clear, prepare for testing.

[0049] 5) Adjust the height of the sample stage and the syringe so that they appear simultaneously in the video monitoring interface of the software. Adjust the baseline in the software to keep it consistent with the plane of the fiber cloth. Perform the test according to the conventional test parameters: input the drop volume of 3μL, click the drop, the needle squeezes out the resin liquid, select the trigger mode as continuous trigger, and perform real-time measurement; move the syringe downward until the resin liquid contacts the fiber cloth and stops, then move the needle upward, and automatically measure the contact angle after the liquid starts to drip. The test results are as follows: Figure 5 shown.

[0050] 6) The software takes ten pictures continuously, records the contact angle during the spreading process and calculates the average value.

[0051] 7) Clean the high-temperature syringe, select acetone as the cleaning solvent, soak the resin in acetone to dissolve it, and then rinse it 2-3 times.

[0052] Figure 4 This is the contact angle measurement result before test parameter optimization. Test parameters: drop volume 3μL, followed by triggering. Figure 5 This is the contact angle measurement result after optimizing the test parameters: drop volume 7μL, delay 1s trigger. Figure 4 and Figure 5It can be seen that when the conventional parameter test is selected, the drop volume is 3μL, and the trigger mode is selected as the subsequent trigger. Because the resin is relatively viscous, too little liquid is squeezed out of the injection needle. The subsequent trigger means that when the resin contacts the fiber cloth, the needle is lifted up, and the test starts at the moment when the resin and the needle fall off. Due to the resin drawing, the software cannot test the contact angle. When the optimized parameter test is selected, the drop volume is selected as 7μL, the trigger mode is selected as the delayed trigger, and the delay time is selected as 1s, the needle can squeeze out a complete droplet. The delayed trigger can be automatically triggered after the "drawing" phenomenon ends, realizing the measurement of the contact angle.

[0053] Although the present invention has been disclosed as above by way of embodiments, it is not intended to limit the present invention. Appropriate modifications or equivalent substitutions of the technical solutions of the present invention made by ordinary technicians in the field should all be included in the protection scope of the present invention. The protection scope of the present invention shall be based on what is defined in the claims.

Claims

1. A high temperature contact angle measuring device for viscous resin, comprising a light source, a liquid injection pump fixing frame, a liftable sample stage, a microscope and a computer; characterized in that: It also includes a high-temperature syringe and a heating device. The high-temperature syringe can be detachably mounted on the injection pump fixing frame and is used for loading and injecting the resin sample liquid; the heating device is used for controllably heating the high-temperature syringe to turn the resin sample in the high-temperature syringe into liquid.

2. The device according to claim 1, characterized in that The high-temperature syringe comprises a needle, a syringe, a piston and a sealing rubber ring located at the bottom end of the piston. The needle, the syringe and the piston of the high-temperature syringe are made of stainless steel.

3. The device according to claim 1, characterized in that The heating device comprises a temperature control box and a heating sleeve. The heating sleeve is covered on the high-temperature syringe and is used to heat the resin sample. The temperature control box is connected to the heating sleeve and is used to control the heating temperature.

4. A method for measuring the high temperature contact angle of a viscous resin, implemented based on the device according to any one of claims 1 to 3, characterized in that: The following steps are involved: 1) Place the resin sample in a beaker and then place it in a water bath for heating until the resin sample has good fluidity; 2) Immediately use a high-temperature syringe to absorb the resin liquid, install the heating sleeve on the periphery of the high-temperature syringe, and then install them together on the injection pump fixing frame and lock them, turn on the temperature control box, heat the heating sleeve to the target temperature and maintain a constant temperature; 3) Perform pre-injection operation on the high-temperature syringe to exhaust the gas in the needle until the resin liquid is about to flow out; place the fiber cloth on the liftable sample table and lay it flat, ready for testing; 4) Adjust the height of the liftable sample table and the high-temperature syringe so that they appear simultaneously in the video monitoring interface of the computer, adjust the reference line on the computer to be consistent with the plane of the fiber cloth, input the drip volume parameter and extrude the resin liquid, select the trigger mode and shoot in real time, move the high-temperature syringe downward until the resin liquid contacts the fiber cloth, then move the needle upward, and start to automatically measure the contact angle after the resin liquid drips; 5) When the resin liquid is dripped and spread on the fiber cloth, ten photos are taken continuously to record the contact angle during the spreading process and calculate the average value.

5. The method according to claim 4, characterized in that When placing the fiber cloth in step 3), the edge of the fiber cloth on the side close to the microscope should be vertically aligned with the needle of the high-temperature syringe.

6. The method according to claim 4, characterized in that In step 4), the drop volume parameter is selected to be 6-8 μL.

7. The method according to claim 4, characterized in that The trigger mode selected in step 4) is sequential trigger or delayed trigger.

8. The method according to claim 7, characterized in that When the delayed trigger mode is selected in step 4), the extended time is set to 0.5-2s.

9. The method according to claim 4, characterized in that Step 5) After the operation is completed, select an organic solvent to clean the high-temperature syringe several times until it is clean.

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