CN111595775A - Method for evaluating hot-melt welding performance of high polymer - Google Patents
Method for evaluating hot-melt welding performance of high polymer Download PDFInfo
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Abstract
The invention provides a method for evaluating the hot-melt welding performance of a polymer, which comprises the following steps: a) carrying out vacuum film pressing on the polymer granules to obtain a polymer film; b) preparing a sample of the polymer film obtained in the step a), preheating two film sample strips, and then performing rolling welding to obtain a welded film; c) cutting the welded film obtained in the step b) into a rectangular sample strip, carrying out T-shaped peeling test, and evaluating the hot-melt welding performance of the polymer according to the test result. Compared with the prior art, the method provided by the invention can scientifically and effectively evaluate the welding performance of the high polymer material, further can adjust the operation conditions of actual welding production according to the obtained change curve of the peel strength, and solves the defect that the welding quality can be evaluated and the welding conditions can only be adjusted after the high polymer welding is finished in the prior art, so that the welding defective rate of the high polymer material is reduced, the material loss is reduced, and the method plays an important role in improving the evaluation standard of the high polymer hot-melt welding quality.
Description
Technical Field
The invention relates to the technical field of high polymer materials, in particular to a method for evaluating the hot-melt welding performance of a high polymer.
Background
The polymer material has been widely applied to various fields of national economy, and the use of the polymer material cannot be separated from high-precision aerospace to clothes and food residence of ordinary people. One material to product needs shaping, namely a forming processing step, so that the product has practical functions, and due to the influence of a material processing technology, many products with complex structures cannot be formed in one step, but are formed by combining multiple materials or parts. Currently, three ways of mechanical fasteners, adhesives and welding can be used to combine the various components; of the three joining methods, the welding process is most effective.
Plastic welding is an effective method for permanently joining plastic parts, and only thermoplastics with identical or similar molecular chain structures can be welded. During welding, molecular chains move violently, surface molecular chains of the two weldments diffuse mutually, the surface disappears, and a transition layer is formed. Therefore, the diffusion time is prolonged, and the bonding strength is also increased. There are many welding methods, and currently, many methods such as ultrasonic welding, laser welding, hot plate welding, friction welding, vibration welding, high-frequency welding, hot air welding, induction welding, and the like are used, and the difference mainly lies in the difference of heating modes. Hot plate welding is the simplest mass production technique for plastic joining, taking hot plate welding as an example; placing a high-temperature hot plate between the surfaces of the to-be-welded seams, heating for a period of time, drawing out the hot plate after softening, attaching the two surfaces under pressure, keeping for a period of time, and cooling the molten surface to finish welding; the hot plate welding temperature is generally between 180 ℃ and 230 ℃ (different materials are different for determining the temperature range), and is determined according to the thickness and the type to be welded; factors influencing the welding quality are many, including the temperature of a heating plate, the heating time, the pressurizing pressure, the pressurizing time, the structure of a weldment, the plasticizing degree of high polymer resin and the like; in addition, the alignment degree of the die can also influence the welding quality, and the defects of poor crack welding, large crater, internal knotting and the like occur; these defects increase the defective rate, lead to material loss, and increase the cost.
At present, the prior art lacks an effective evaluation method for judging the welding quality of a weldment with a certain formula in advance, and can only judge the welding quality of the weldment with the formula according to the welding result in production: whether the welding position is firm and whether the welding scar exists or not is directly perceived, and then the welding heating time, the temperature and other conditions are adjusted by workers according to experience, so that the welding quality of the weldment is improved. However, the technical scheme has the defects of large material loss, strong dependence on operation experience of workers and the like, cannot be used as a standard for evaluating welding quality, and has no popularization and learning.
Disclosure of Invention
In view of the above, the present invention provides a method for evaluating hot-melt welding performance of a polymer, which can scientifically and effectively evaluate welding performance of a polymer material, and solve the problem that welding quality can only be evaluated and welding conditions can only be adjusted after the completion of polymer welding in the prior art, so as to reduce defective welding rate of the polymer material, reduce material loss, and play an important role in further improving evaluation standards of hot-melt welding quality of the polymer material.
The invention provides a method for evaluating the hot-melt welding performance of a polymer, which comprises the following steps:
a) carrying out vacuum film pressing on the polymer granules to obtain a polymer film;
b) preparing a sample of the polymer film obtained in the step a), preheating two film sample strips, and then performing rolling welding to obtain a welded film;
c) cutting the welded film obtained in the step b) into a rectangular sample strip, carrying out T-shaped peeling test, and evaluating the hot-melt welding performance of the polymer according to the test result.
Preferably, the temperature of the vacuum film pressing in the step a) is 110-180 ℃, the melting time is 2-3 min, the pressure relief time is 3-5 times, the pressure is 8-12 MPa, and the pressure maintaining time is 1-2 min.
Preferably, the sample preparation process in step b) specifically comprises:
cutting the polymer film to obtain a film sample strip; the width of the film sample strip is 3 cm-5 cm, the length is 6 cm-8 cm, and the thickness is 1 mm-1.5 mm.
Preferably, the preheating temperature in the step b) is 100-200 ℃ and the time is 2-50 s.
Preferably, the device used for the roll welding in step b) is an open mill.
Preferably, the roll welding process in step b) is specifically:
and heating the open mill to a preheating temperature, preheating the two film sample strips on the roll surface, then attaching the two film sample strips together, and completing welding through a gap between the two rolls of the open mill to obtain the welded film.
Preferably, the gap between the two rollers in the step b) is 1 mm-2 mm.
Preferably, the width of the rectangular sample strip in step c) is 0.8 cm-1.2 cm, and the length is 5 cm-10 cm.
Preferably, the apparatus for the T-peel test in step c) is a universal tensile testing machine.
Preferably, the stretching speed of the T-shaped peeling test in the step c) is 1 mm/min-10 mm/min, and the stretching temperature is 23-24 ℃; the sample strips are repeated for 3 to 5 times under each welding condition, and the average value is taken.
The invention provides a method for evaluating the hot-melt welding performance of a polymer, which comprises the following steps: a) carrying out vacuum film pressing on the polymer granules to obtain a polymer film; b) preparing a sample of the polymer film obtained in the step a), preheating two film sample strips, and then performing rolling welding to obtain a welded film; c) cutting the welded film obtained in the step b) into a rectangular sample strip, carrying out T-shaped peeling test, and evaluating the hot-melt welding performance of the polymer according to the test result. Compared with the prior art, the method provided by the invention can scientifically and effectively evaluate the welding performance of the high polymer material, further can adjust the operation conditions of actual welding production according to the obtained change curve of the peel strength, and solves the defect that the welding quality can be evaluated and the welding conditions can only be adjusted after the high polymer welding is finished in the prior art, so that the welding defective rate of the high polymer material is reduced, the material loss is reduced, and the method plays an important role in further improving the evaluation standard of the high polymer hot-melt welding quality.
In addition, the method provided by the invention only uses an open mill and a tensile testing machine for testing, the device is generally and easily available, and expensive instruments such as a differential scanning calorimeter are not needed; and the detection requires few materials, the operation process is simple and convenient, and the welding quality can be detected in the mixing granulation stage, so that the welding guide device plays a role in guiding the actual production welding.
Drawings
FIG. 1 is a photograph of T-peel test bars of example 1;
FIG. 2 is a photograph of a T-peel test of a sample strip in example 1;
FIG. 3 is a graph showing the peel strength versus displacement of PVC resin particles of example 1 at different preheating times;
FIG. 4 is a scanning electron micrograph of the surface of an unwelded PVC composite film of example 1;
FIG. 5 is a scanning electron microscope photograph of the surface of the sample after peeling for a preheating time of 40s in example 1;
FIG. 6 is a graph showing the peel strength versus displacement for different preheating times of the PVC resin particles of example 2;
FIG. 7 is a graph showing the peel strength versus displacement for different preheating times of the PVC resin particles of example 3;
FIG. 8 is a graph showing the peel strength vs. preheating time of three types of PVC resin particles in examples 1 to 3;
FIG. 9 is a graph showing the peel strength versus displacement for different preheating times of the PVC resin particles of example 4;
FIG. 10 is a graph showing the peel strength versus displacement for different preheating times of the PVC resin particles of example 5;
FIG. 11 is a graph showing the peel strength versus displacement for different preheating times of the PVC resin particles of example 6;
FIG. 12 is a graph showing the peel strength versus displacement for different preheating times of the PVC resin particles of example 7;
FIG. 13 is a graph showing the peel strength vs. preheating time of four types of PVC resin particles in examples 4 to 7;
FIG. 14 is a graph of peel strength versus displacement for different preheat times for the EGMA1 particles of example 8;
fig. 15 is a stress-strain curve for EGMA1 and EGMA 2;
FIG. 16 is a graph of peel strength versus displacement for different preheat times for the EGMA2 particles of example 9;
FIG. 17 is a graph of peel strength vs. preheat time for two EGMA particles of examples 8-9;
FIG. 18 is a peel strength versus displacement curve for different preheat times for mSEBS particles of example 10;
FIG. 19 is a peel strength-preheat time curve for mSEBS particles.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a method for evaluating the hot-melt welding performance of a polymer, which comprises the following steps:
a) carrying out vacuum film pressing on the polymer granules to obtain a polymer film;
b) preparing a sample of the polymer film obtained in the step a), preheating two film sample strips, and then performing rolling welding to obtain a welded film;
c) cutting the welded film obtained in the step b) into a rectangular sample strip, carrying out T-shaped peeling test, and evaluating the hot-melt welding performance of the polymer according to the test result.
The invention firstly carries out vacuum film pressing on the polymer granules to obtain the polymer film. The invention has no special limitation on the specific types of the polymer granules, and is specifically determined according to the types of the polymers with the hot-melting welding performance to be measured; in a preferred embodiment of the present invention, the method specifically includes: polyvinyl chloride (PVC), ethylene-acrylate-glycidyl methacrylate random copolymer (EGMA), maleic anhydride grafted styrene-ethylene-co-butylene-styrene triblock copolymer (mSEBS).
The preparation method of the polymer granules is not particularly limited, and the polymer granules are prepared by premixing the polymer material and the additive (or not adding the additive) and granulating by a double-screw extruder, which is well known to those skilled in the art.
In the invention, the vacuum film pressing device is preferably a vacuum film pressing machine, so that the whole vacuum film pressing process is kept in a vacuum-pumping state; the temperature of the vacuum film pressing is preferably 110-180 ℃, and the melting time is preferably 2-3 min; the pressure relief frequency of the vacuum film pressing is preferably 3 to 5 times, and more preferably 3 to 4 times; the pressure of the vacuum lamination is preferably 8MPa to 12MPa, and more preferably 10 MPa; the pressure maintaining time of the vacuum film pressing is preferably 1 min-2 min.
After the high polymer film is obtained, the invention prepares the sample of the obtained high polymer film, and then takes two film sample strips for preheating and then carries out rolling welding to obtain the welded film. In the present invention, the sample preparation process preferably includes:
cutting the polymer film to obtain a film sample strip; the width of the film sample strip is preferably 3 cm-5 cm, and more preferably 3 cm; the length of the film sample strip is preferably 6 cm-8 cm, and more preferably 6 cm-7 cm; the thickness of the film sample strip is preferably 1mm to 1.5mm, more preferably 1.1mm to 1.2 mm.
In the invention, the preheating temperature is preferably 100-200 ℃, and more preferably 110-190 ℃; the preheating time is preferably 2s to 50s, more preferably 5s to 40 s.
In the present invention, the apparatus used for the roll welding is preferably an open mill; in the preferred embodiment of the present invention, a small open mill known to those skilled in the art is used. In the present invention, the rolling welding process is preferably specifically:
and heating the open mill to a preheating temperature, preheating the two film sample strips on the roll surface, then attaching the two film sample strips together, and completing welding through a gap between the two rolls of the open mill to obtain the welded film. In the present invention, the roll gap is preferably 1mm to 2mm, more preferably 1.4mm to 1.6 mm.
After the welded film is obtained, the welded film is cut into rectangular sample strips, T-shaped peeling test is carried out, and the hot-melt welding performance of the high polymer is evaluated according to the test result. In the present invention, the width of the rectangular sample strip is preferably 0.8cm to 1.2cm, more preferably 1 cm; the length of the rectangular sample strip is preferably 5 cm-10 cm, and more preferably 7 cm; the thickness of the rectangular sample strip is not particularly limited, and specifically is the corresponding thickness of the welded film obtained after the rolling welding process.
In the present invention, the apparatus for the T-peel test is preferably a universal tensile testing machine; the stretching speed of the T-shaped peeling test is preferably 1 mm/min-10 mm/min, and more preferably 10 mm/min; the stretching temperature of the T-shaped peeling test is preferably 23-24 ℃, and more preferably 23.5 ℃; preferably, the sample strip is repeated for 3 to 5 times under each welding condition of the T-shaped peeling test, and an average value is obtained; to reduce errors.
In the present invention, the test results preferably include a peel strength-displacement curve and a peel strength-preheating time curve as test results, and the polymer hot-melt welding performance is further evaluated.
The invention provides a method for evaluating the hot-melt welding performance of a polymer, which comprises the following steps: a) carrying out vacuum film pressing on the polymer granules to obtain a polymer film; b) preparing a sample of the polymer film obtained in the step a), preheating two film sample strips, and then performing rolling welding to obtain a welded film; c) cutting the welded film obtained in the step b) into a rectangular sample strip, carrying out T-shaped peeling test, and evaluating the hot-melt welding performance of the polymer according to the test result. Compared with the prior art, the method provided by the invention can scientifically and effectively evaluate the welding performance of the high polymer material, further can adjust the operation conditions of actual welding production according to the obtained change curve of the peel strength, and solves the defect that the welding quality can be evaluated and the welding conditions can only be adjusted after the high polymer welding is finished in the prior art, so that the welding defective rate of the high polymer material is reduced, the material loss is reduced, and the method plays an important role in further improving the evaluation standard of the high polymer hot-melt welding quality.
In addition, the method provided by the invention only uses an open mill and a tensile testing machine for testing, the device is generally and easily available, and expensive instruments such as a differential scanning calorimeter are not needed; and the detection requires few materials, the operation process is simple and convenient, and the welding quality can be detected in the mixing granulation stage, so that the welding guide device plays a role in guiding the actual production welding.
To further illustrate the present invention, the following examples are provided for illustration.
Example 1
Heating the PVC plasticizer to 40 ℃, adding the PVC plasticizer into a high-speed mixer to be mixed and plasticized with PVC resin powder, and then extruding and granulating the mixture through a double-screw extruder to obtain PVC resin particles.
Firstly, pressing PVC resin particles into a film in a vacuum film pressing machine, wherein the film pressing temperature is 160 ℃, melting is carried out for 2min, pressure is released for 3 times, pressure is maintained for 1min under 10MPa, and the whole process is kept in a vacuumizing state to obtain a PVC composite film; cutting the pressed film into rectangular sample strips with the width of 3cm, the length of 7cm and the thickness of 1.2 mm; setting the temperature of a small open mill to 180 ℃, preheating the cut rectangular sample strips on the surfaces of rollers for 2s, 5s, 10s, 20s and 40s respectively, then attaching two film sample strips together, and passing through a gap between the two rollers of the open mill, wherein the gap between the two rollers is 1.6mm, completing welding to obtain a welded film, further cutting the welded film into rectangular sample strips with the width of 1cm and the length of 7cm (shown in figure 1, and figure 1 is a picture of a T-shaped stripping test sample strip in the embodiment 1), and carrying out a T-shaped stripping test on a universal tensile testing machine (shown in figure 2, and figure 2 is a picture of a T-shaped stripping test sample strip in the embodiment 1), wherein the tensile rate is 10mm/min, and the tensile temperature is 23.5 ℃; the sample strip is repeated for 3-5 times under each welding condition, and the average value is obtained.
FIG. 3 is a graph showing the peel strength versus displacement curve of PVC resin particles (a 40 ℃ sample of plasticizer) in example 1 for different preheating times; when the displacement terminal point is reached, the sample strip is completely stripped; as can be seen from FIG. 3, the preheating time was increased from 2s to 40s, the peel strength was also gradually increased from 150N/m to 2300N/m, and the rate of increase in peel strength was slowed as the preheating time was increased.
FIG. 4 is a SEM photograph of the surface of the unwelded PVC composite film of example 1, showing that the surface of the unwelded PVC composite film is relatively flat; FIG. 5 is a SEM photograph (2000 times magnification) of the peeled surface of the sample after preheating for 40s in example 1, and it can be seen that the surface of the welded sample was roughened after peeling and had a large number of protrusions, which is completely different from the unwelded surface of FIG. 4.
Example 2
The welding performance of the plasticizer 60 ℃ PVC resin particles was evaluated by the following procedure, which is the same as example 1, except that the PVC plasticizer was heated to 60 ℃ and then added to a high-speed mixer to be mixed and plasticized with PVC resin powder.
FIG. 6 is a graph of peel strength versus displacement for different preheating times of the PVC resin particles (plasticizer 60 ℃ samples) of example 2; when the displacement terminal point is reached, the sample strip is completely stripped; as can be seen from FIG. 6, the preheating time is increased from 2s to 20s, the peel strength is also gradually increased from 100N/m to 1600N/m, the preheating time is continuously prolonged to 40s, the increase degree of the peel strength is small, and the plateau is reached.
Example 3
The welding performance of the plasticizer 80 ℃ PVC resin particles was evaluated by the following procedure, which is the same as example 1, except that the PVC plasticizer was heated to 80 ℃ and then added to a high-speed mixer to be mixed and plasticized with PVC resin powder.
FIG. 7 is a graph showing the peel strength versus displacement for different preheating times of the PVC resin particles (plasticizer 80 ℃ samples) in example 3; when the displacement terminal point is reached, the sample strip is completely stripped; as can be seen from FIG. 7, the preheating time was increased from 2s to 10s, the peel strength was rapidly increased from 150N/m to 1400N/m, and the peel strength was slowly increased to 2000N/m as the preheating time was increased.
FIG. 8 is a graph showing the peel strength vs. preheating time of three types of PVC resin particles in examples 1 to 3; comparing the change trends of the peeling strength of the PVC resin particles with three different plasticizer temperatures to the curve of the preheating time, it can be seen that the peeling strength of the PVC resin particles with the plasticizer of 80 ℃ is increased fastest, the PVC resin particles with the plasticizer of 40 ℃ is second, and the PVC resin particles with the plasticizer of 60 ℃ is slowest in the short-time (less than 10s) welding, therefore, in the actual welding production, if the required welding time of the PVC resin particles with the plasticizer of 80 ℃ is 4s, when the plasticizer temperature is reduced, the welding time (such as 4.5s or 5s) can be properly prolonged, thereby achieving the same welding effect; in addition, the degree of deformation varies depending on the peel strength of different samples, and the displacement end point of complete peeling also varies.
Example 4
Mixing PVC resin powder with plasticizer, stabilizer, calcium powder and other assistants in a high-speed mixer, extruding and pelletizing in a double-screw extruder to obtain various parts, and welding to form complete product. Therefore, the twin-screw extrusion granulation process is also an important factor influencing the welding performance of PVC; in the extrusion granulation process, uneven feeding can cause unstable current, the flowability of some powder is poor, feeding is difficult, a screw is easy to hold, the feeding amount is small, and the current is relatively large. Therefore, the host current of the twin-screw extruder was kept at 6.5A during the granulation of PVC, and the difference in welding properties was examined by performing the extrusion granulation.
Firstly, pressing PVC resin particles into a film in a vacuum film pressing machine, wherein the film pressing temperature is 160 ℃, melting is carried out for 2min, pressure is released for 3 times, pressure is maintained for 1min under 10MPa, and the whole process is kept in a vacuumizing state to obtain a PVC composite film; cutting the pressed film into rectangular sample strips with the width of 3cm, the length of 7cm and the thickness of 1.2 mm; setting the temperature of a small open mill to 180 ℃, preheating the cut rectangular sample strips on the surfaces of rollers for 2s, 5s, 10s and 20s respectively, then bonding two film sample strips together, completing welding through a gap between two rollers of the open mill, wherein the gap between the two rollers is 1.6mm, obtaining a welded film, further cutting the welded film into rectangular sample strips with the width of 1cm and the length of 7cm, and performing a T-shaped peeling test on a universal tensile testing machine, wherein the tensile rate is 10mm/min and the tensile temperature is 23.5 ℃; the sample strip is repeated for 3-5 times under each welding condition, and the average value is obtained.
FIG. 9 is a graph of peel strength versus displacement for different preheating times for the PVC resin particles of example 4 (sample current of 6.5A); when the displacement terminal point is reached, the sample strip is completely stripped; as can be seen from FIG. 9, the preheating time was increased from 2s to 20s, the peel strength was gradually increased from 70N/m to 1300N/m, and the displacement endpoint reaching complete peeling was increased as the peel strength was increased.
Example 5
The welding performance of the PVC resin particles at a twin-screw extruder host current of 8A was evaluated in the same manner as in example 4, except that the twin-screw extruder host current was maintained at 8A.
FIG. 10 is a graph of peel strength versus displacement for different preheating times for the PVC resin particles of example 5 (current 8A sample); when the displacement terminal point is reached, the sample strip is completely stripped; as can be seen from FIG. 10, the preheating time was increased from 2s to 20s, the peel strength was gradually increased from 70N/m to 1700N/m, and the displacement endpoint reaching complete peeling was increased as the peel strength was increased.
Example 6
The welding performance of the PVC resin particles at a twin-screw extruder main machine current of 10A was evaluated in the same manner as in example 4, except that the twin-screw extruder main machine current was maintained at 10A.
FIG. 11 is a graph of peel strength versus displacement for different preheating times for the PVC resin particles of example 6 (current 10A samples); when the displacement terminal point is reached, the sample strip is completely stripped; as can be seen from FIG. 11, the preheating time was increased from 2s to 20s, the peel strength was gradually increased from 33N/m to 1690N/m, and the displacement end point to complete peeling was increased as the peel strength was increased.
Example 7
The welding performance of the PVC resin particles of the twin-screw extruder main machine current 14A was evaluated in the same manner as in example 4 except that the twin-screw extruder main machine current was maintained at 14A.
FIG. 12 is a graph of peel strength versus displacement for different preheating times for the PVC resin particles of example 7 (sample of Current 14A); when the displacement terminal point is reached, the sample strip is completely stripped; as can be seen from FIG. 12, the preheating time was increased from 2s to 20s, the peel strength was gradually increased from 47N/m to 1630N/m, and the displacement endpoint reaching complete peeling was increased as the peel strength was increased.
FIG. 13 is a graph showing the peel strength vs. preheating time of four types of PVC resin particles in examples 4 to 7; comparing the change trends of the curves of the peeling strength of the PVC resin particles of the host currents of the four different double-screw extruders to the preheating time, it can be seen that the peeling strength of the PVC resin particles of the host currents of 6.5A is the lowest at the preheating time of 20s, and is only 1300N/m; the peel strength of the PVC resin particles of the host machine currents 8A, 10A and 14A is relatively close to 1700N/m; the current of the main machine of the double-screw extruder is too low (6.5A), which is not beneficial to welding, and the welding strength is low; comparing the change trends of the peel strengths of the PVC resin particles of 8A, 10A, and 14A, the peel strength of the PVC resin particle of host current 10A increases fastest, the PVC resin particle of host current 8A is next lowest, and the PVC resin particle of host current 14A is slowest; therefore, there is an optimum current value, and the welding time is required to be prolonged if the current is too high or too low; in addition, the degree of deformation varies depending on the peel strength of different samples, and the displacement end point of complete peeling also varies.
Example 8
The welding performance of EGMA1 was evaluated as follows.
Firstly, pressing EGMA1 particles into a film in a vacuum film pressing machine, wherein the film pressing temperature is 110 ℃, melting is carried out for 3min, pressure relief is carried out for 4 times, pressure is maintained for 2min under 10MPa, and the whole process is kept in a vacuumizing state to obtain an EGMA1 film; cutting the pressed film into rectangular sample strips with the width of 3cm, the length of 7cm and the thickness of 1.1 mm; setting the temperature of a small open mill to 120 ℃, preheating the cut rectangular sample strips on the roll surfaces for 10s, 20s and 40s respectively, then adhering two film sample strips together, completing welding through a gap between two rolls of the open mill, wherein the gap between the two rolls is 1.4mm, obtaining a welded film, further cutting the welded film into rectangular sample strips with the width of 1cm and the length of 7cm, and carrying out a T-shaped stripping test on a universal tensile testing machine, wherein the tensile rate is 10mm/min and the tensile temperature is 23.5 ℃; the sample strip is repeated for 3-5 times under each welding condition, and the average value is obtained.
FIG. 14 is a graph of peel strength versus displacement for different preheat times for the EGMA1 particles of example 8; when the displacement terminal point is reached, the sample strip is completely stripped; as can be seen from FIG. 14, when the preheating time was 10s, the peel strength was only 40N/m, and when the preheating time was increased to 20s, the peel strength rapidly increased to 3900N/m, and when the preheating time was continuously increased to 40s, the peel strength increased to 4200N/m, and the increase was reduced.
Example 9
The welding performance of EGMA2 was evaluated as follows, and the procedure was the same as in example 8, except that the mechanical properties of EGMA1 were better than that of EGMA2 (see fig. 15, which is a stress-strain curve of EGMA1 and EGMA2, and the young's modulus and elongation at break of EGMA1 were higher than those of EGMA 2).
FIG. 16 is a graph of peel strength versus displacement for different preheat times for the EGMA2 particles of example 9; when the displacement terminal point is reached, the sample strip is completely stripped; as can be seen from FIG. 16, when the preheating time was 10s, the peel strength was only 78N/m, and when the preheating time was increased to 20s, the peel strength rapidly increased to 1800N/m, and when the preheating time was continuously increased to 40s, the peel strength increased to 1980N/m, and the increase was reduced.
FIG. 17 is a graph of peel strength vs. preheat time for two EGMA particles of examples 8-9; comparing the change trends of the curves of the peel strength of the two different EGMA films and the preheating time, the growth trends of the peel strength of the two EGMA films are the same, but the EGMA1 film has higher peel strength and faster growth, and the time required by welding is shorter; in addition, the degree of deformation varies depending on the peel strength of different samples, and the displacement end point of complete peeling also varies.
Example 10
The welding performance of the mSEBS was evaluated as follows.
Firstly, pressing mSEBS particles into a film in a vacuum film pressing machine, wherein the film pressing temperature is 180 ℃, melting is carried out for 3min, pressure is released for 4 times, pressure is maintained for 2min under 10MPa, and the whole process is kept in a vacuumizing state to obtain an mSEBS film; cutting the pressed film into rectangular sample strips with the width of 3cm, the length of 7cm and the thickness of 1.1 mm; setting the temperature of a small open mill to 190 ℃, preheating the cut rectangular sample strips on the surfaces of rollers for 5s, 10s, 20s and 40s respectively, then bonding two film sample strips together, completing welding through a gap between two rollers of the open mill, wherein the gap between the two rollers is 1.4mm, obtaining a welded film, further cutting the welded film into rectangular sample strips with the width of 1cm and the length of 7cm, and performing a T-shaped peeling test on a universal tensile testing machine, wherein the tensile rate is 10mm/min and the tensile temperature is 23.5 ℃; the sample strip is repeated for 3-5 times under each welding condition, and the average value is obtained.
FIG. 18 is a peel strength versus displacement curve for different preheat times for mSEBS particles of example 10; when the displacement terminal point is reached, the sample strip is completely stripped; as is clear from FIG. 18, when the preheating time was 5s, the peel strength was 400N/m, when the preheating time was increased to 10s, the peel strength rapidly increased to 2300N/m, when the preheating time was continuously increased to 20s, the peel strength increased to 2400N/m, the increase was reduced, and when the preheating time was continuously increased to 40s, the peel strength decreased to 1800N/m instead.
FIG. 19 is a peel strength-preheat time curve for mSEBS particles; from the trend of the curve of the peel strength of the mSEBS film against the preheating time, it can be seen that the welding of the mSEBS film for a long time results in a decrease in the welding strength.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. A method for evaluating the hot-melt welding performance of high polymers comprises the following steps:
a) carrying out vacuum film pressing on the polymer granules to obtain a polymer film;
b) preparing a sample of the polymer film obtained in the step a), preheating two film sample strips, and then performing rolling welding to obtain a welded film;
c) cutting the welded film obtained in the step b) into a rectangular sample strip, carrying out T-shaped peeling test, and evaluating the hot-melt welding performance of the polymer according to the test result.
2. The method according to claim 1, wherein the temperature of the vacuum film pressing in the step a) is 110-180 ℃, the melting time is 2-3 min, the pressure relief times are 3-5, the pressure is 8-12 MPa, and the pressure holding time is 1-2 min.
3. The method according to claim 1, wherein the sample preparation process in step b) is specifically:
cutting the polymer film to obtain a film sample strip; the width of the film sample strip is 3 cm-5 cm, the length is 6 cm-8 cm, and the thickness is 1 mm-1.5 mm.
4. The method according to claim 1, wherein the preheating in step b) is carried out at a temperature of 100 ℃ to 200 ℃ for a time of 2s to 50 s.
5. The method of claim 1, wherein the roll welding in step b) is performed using an open mill.
6. The method according to claim 5, wherein the rolling welding in step b) is performed by:
and heating the open mill to a preheating temperature, preheating the two film sample strips on the roll surface, then attaching the two film sample strips together, and completing welding through a gap between the two rolls of the open mill to obtain the welded film.
7. The method of claim 6, wherein the roll gap in step b) is between 1mm and 2 mm.
8. The method according to claim 1, wherein the rectangular splines in step c) have a width of 0.8cm to 1.2cm and a length of 5cm to 10 cm.
9. The method of claim 1, wherein the T-peel testing apparatus in step c) is a universal tensile testing machine.
10. The method according to claim 9, wherein the T-peel test in step c) has a tensile rate of 1mm/min to 10mm/min and a tensile temperature of 23 ℃ to 24 ℃; the sample strips are repeated for 3 to 5 times under each welding condition, and the average value is taken.
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