CN119238905B

CN119238905B - Forming method of ultra-high molecular weight polyethylene strip

Info

Publication number: CN119238905B
Application number: CN202411771314.1A
Authority: CN
Inventors: 王宗宝; 崔秋月; 张利
Original assignee: Ningbo University
Current assignee: Ningbo University
Priority date: 2024-12-04
Filing date: 2024-12-04
Publication date: 2025-10-28
Anticipated expiration: 2044-12-04
Also published as: CN119238905A

Abstract

The application discloses a forming method of an ultra-high molecular weight polyethylene strip, which comprises the following steps of 1, mixing ultra-high molecular weight polyethylene resin and a low molecular weight solvent to prepare uniform suspension, extruding at high temperature, cooling and shaping to obtain a gel film, 2, carrying out uniaxial high-temperature ultra-heat stretching on the gel film, 3, extracting the stretched gel film to remove the low molecular weight solvent, and then carrying out hot air drying to obtain a dried film, 4, longitudinally cutting the dried film to form a strip, and 5, carrying out low-multiple uniaxial heat stretching on the strip to remove pores to obtain the final ultra-high molecular weight polyethylene strip. The gel film is subjected to uniaxial hot stretching under the condition that a low molecular weight solvent is not removed, and the low molecular weight solvent is favorable for promoting the formation of high-orientation crystals such as fibrous extended chain crystal orientation, follow-up extended chain crystal and the like remained in the gel film, so that the tensile mechanical property and the like of the final strip are favorable for improving.

Description

Forming method of ultra-high molecular weight polyethylene strip

Technical Field

The application relates to the technical field of high polymers, in particular to a method for forming an ultra-high molecular weight polyethylene strip.

Background

Ultra-high molecular weight polyethylene is a thermoplastic engineering plastic with excellent comprehensive properties, and the molecular weight is generally 100-600 ten thousand or more. The film made of ultra-high molecular weight polyethylene has excellent wear resistance and good adhesion resistance, and has wide application in civil, medical and military industries and the like, so that the realization of industrial production of the film has great significance. For many years, those skilled in the art of ultra-high molecular weight polyethylene materials and related applications have sought a process suitable for the commercial production of ultra-high molecular weight polyethylene films. In particular, how to obtain ultra-high molecular weight polyethylene tapes with excellent properties has become a technical problem which the related art has been eager to solve.

To prepare the ultra-high molecular weight polyethylene strip with excellent mechanical properties, a gel forming method can be adopted, the ultra-high molecular weight polyethylene is firstly mixed with a proper solvent and dissolved at high temperature to prepare a solution, then a gel film is generated through gel forming, the gel film is firstly extracted and dried, then the dried film is cut to form a strip, and then uniaxial multistage hot stretching is carried out to obtain the ultra-high molecular weight polyethylene finished product strip.

Because the resin has ultrahigh molecular weight, the viscosity is very large when all the resin is completely dissolved, and the conditions for preparing uniform solution are harsh, so that high-concentration uniform solution is difficult to obtain, and because the required dissolving temperature of the resin is very high, the molecular weight of the ultrahigh molecular weight polyethylene is greatly reduced, and the mechanical property of the final strip is affected.

Patent CN115302751a discloses a process for preparing an ultra-high molecular weight polyethylene film retaining extended chain crystals, which realizes that only folded chain crystals with lower melting point in ultra-high molecular weight polyethylene are dissolved under low temperature conditions and partial dissolution of extended chain crystals in resin is retained by precisely controlling temperature in the preparation process of ultra-high molecular weight polyethylene solution, thereby reducing viscosity of the ultra-high molecular weight polyethylene solution and reducing molecular weight reduction caused by high processing temperature. The extended chain crystals remained in the dissolution process are used as efficient nucleating agents for the ultra-high molecular weight polyethylene crystallization, and the extended chain crystals and the folded chain crystals are formed in the hot stretching process after the extraction and drying are induced.

Through intensive system research in the ultra-high molecular weight polyethylene stretching process of reserved extended chain crystals, it is found that if the gel film is subjected to uniaxial hot stretching, the reserved fibrous extended chain crystals are easier to orient due to the existence of a low molecular weight solvent, and the formation of high-orientation crystals such as subsequent extended chain crystals is easier to promote, so that the stretching mechanical properties and other properties of the final strip are greatly improved, and a unique ultra-high molecular weight polyethylene strip molding process is formed.

Disclosure of Invention

In order to further effectively improve the mechanical properties of the ultra-high molecular weight polyethylene strip, the application provides a forming method of the ultra-high molecular weight polyethylene strip.

The application provides a molding method of an ultra-high molecular weight polyethylene strip, which comprises the following steps,

Step 1, mixing ultra-high molecular weight polyethylene resin and a low molecular weight solvent to prepare uniform suspension, extruding at high temperature, and cooling and shaping to obtain a gel film;

step 2, carrying out uniaxial high-temperature super heat stretching on the gel film;

Step 3, extracting the stretched gel film to remove a low molecular weight solvent, and drying the gel film by hot air to obtain a dried film;

step 4, longitudinally cutting the dried film to form a strip;

and 5, performing low-multiple uniaxial hot stretching on the strip to remove pores, and obtaining the final ultra-high molecular weight polyethylene strip.

By adopting the technical scheme, the gel film is subjected to uniaxial hot stretching under the condition that the low molecular weight solvent is not removed, so that the low molecular weight solvent is favorable for promoting the formation of fibrous extended chain crystal orientation, follow-up extended chain crystal and other high-orientation crystals remained in the gel film, and further favorable for greatly improving the performances such as the stretching performance of the final strip.

Preferably, in the high-temperature extrusion process in the step 1, the temperature of a feeding section of the twin-screw extruder used is 80-130 ℃, the temperature of a compression section is 130-200 ℃, the temperature of a homogenizing section is 130-200 ℃, the temperature of a die head is 130-200 ℃, and the rotating speed of the twin-screw extruder is 30-400 r/min.

By adopting the technical scheme, most of extended chain crystals in the ultra-high molecular weight polyethylene resin can be dissolved after the temperatures of the compression section, the homogenization section and the die head of the double-screw extruder exceed 200 ℃. And below 130 ℃, the platelets in the ultra-high molecular weight polyethylene resin are almost retained, so that the dissolution effect of the ultra-high molecular weight polyethylene resin is affected to reduce the fluidity, and the extruded gel film is uneven.

Preferably, the temperature of the compression section, the homogenization section and the die head of the twin-screw extruder is 130-170 ℃.

By adopting the technical scheme, when the temperature of the compression section, the homogenization section and the die head of the double-screw extruder is controlled at 130-170 ℃, most of extended chain crystals in the ultra-high molecular weight polyethylene resin can be reserved and not dissolved, and meanwhile, the fluidity of the ultra-high molecular weight polyethylene resin after dissolution is ensured, so that the gel film is uniform.

Preferably, the temperature of uniaxial super-heat stretching in the step 2 is 90-130 ℃, the stretching speed is 5-80 m/min, and the stretching ratio is 6-18 times.

Preferably, the uniaxial super-heat stretching temperature is 100-120 ℃.

By adopting the technical scheme, the hot stretching temperature is low, the orientation of the reserved extended chain crystals and the promotion effect on the generation of the subsequent high-orientation crystals are not obvious enough, the hot stretching temperature is high, the ultra-high molecular weight polyethylene gel film is easy to be detangled, the mechanical property of the strip is reduced, the hot stretching process is unstable, and the film quality is unstable.

Preferably, the stretching rate of the uniaxial high-temperature super-heat stretching is 10-60 m/min.

By adopting the technical scheme, the stretching rate is low, and the oriented molecular chains are easier to be de-oriented under the action of the low molecular weight solvent, so that the mechanical property of the final ultra-high molecular weight polyethylene strip is influenced, the production efficiency is also influenced, and the stretching stability of the gel film is influenced when the stretching rate is too high.

Preferably, the stretching ratio of the uniaxial high-temperature super-heat stretching is 10-15 times.

By adopting the technical scheme, the single-axis thermal stretching multiple of the gel film is low, the quantity of the newly formed extended chain crystals promoted by the extended chain crystals reserved in the stretching process is insufficient, the mechanical property of the final strip cannot be greatly improved, and the stability of stretching can be influenced due to the fact that the single-axis stretching multiple of the gel film is too high.

Preferably, the low molecular weight solvent is one or more of decalin, white oil or long linear alkane.

By adopting the technical scheme, the low molecular weight solvent can dissolve the ultra-high molecular weight polyethylene resin relatively easily, thereby facilitating the formation of high-orientation crystals such as the retained fibrous extended chain crystal orientation, the subsequent extended chain crystal and the like in the hot stretching process of the gel film.

Preferably, the low molecular weight solvent is a long linear alkane.

By adopting the technical scheme, as the long straight-chain alkane is normal alkane with components of C12 to C16, the chain structure of the long straight-chain alkane is similar to that of the ultra-high molecular weight polyethylene, and the retention of extended chain crystals in the dissolution of the ultra-high molecular weight polyethylene resin and the formation of high-orientation crystals in the hot stretching process of the gel film are more easily and accurately regulated.

Preferably, in the step 1, the mass ratio of the ultra-high molecular weight polyethylene to the low molecular weight solvent is (0.18-0.45): 1.

By adopting the technical scheme, the method of partially dissolving the ultra-high molecular weight polyethylene resin by a small amount reduces the actual dissolved concentration, and the retained high rigidity of the extended chain crystals enables the solution to form the characteristic similar to the liquid crystal solution, so that the viscosity of the ultra-high molecular weight polyethylene solution can be greatly reduced. However, too low a resin content may result in too low entanglement of the prepared gel film to affect mechanical properties, and too high a resin content may affect partial dissolution effects. The above range is preferable in order to achieve both the dissolution effect of the ultra-high molecular weight polyethylene resin and the mechanical properties of the tape.

Preferably, the temperature of the hot stretching of the strip after the extraction and drying in the step 5 is 120-150 ℃, and the stretching ratio is 1.5-4 times.

By adopting the technical scheme, the problems of unstable hot stretching process, unstable film quality and the like caused by low hot stretching temperature and weak melting recrystallization effect, which can not completely eliminate pores caused by extraction and drying, and the problems of high hot stretching temperature, easy detangling in the ultra-high molecular weight polyethylene film and the like are solved. Meanwhile, the longitudinal heat stretching multiple is low, pores in the dried film cannot be completely eliminated, the mechanical properties of the final film are affected, and the stretching stability of the film is affected by the fact that the uniaxial stretching multiple is too high.

In summary, the application has the following beneficial effects:

1. As the gel film is subjected to uniaxial high-temperature super-heat stretching under the condition that the low-molecular-weight solvent is not removed, the method is beneficial to promoting the orientation of the fibrous extended chain crystals remained in the gel film and the formation of high-orientation crystals such as the follow-up extended chain crystals, thereby greatly improving the stretching performance and other performances of the final ultra-high-molecular-weight polyethylene strip;

2. According to the application, the temperatures of the compression section, the homogenization section and the die head of the double-screw extruder are controlled at 130-170 ℃, so that most of extended chain crystals in the ultra-high molecular weight polyethylene resin can be reserved and not dissolved, and meanwhile, the fluidity of the ultra-high molecular weight polyethylene resin after dissolution is ensured, so that the produced gel film is relatively uniform;

3. In the application, long straight-chain alkane is selected as a low molecular weight solvent, and the long straight-chain alkane is normal alkane with components of C12 to C16. The chain structure of the long straight-chain alkane is similar to that of the ultra-high molecular weight polyethylene, so that the retention of the extended chain crystals in the dissolution of the ultra-high molecular weight polyethylene resin and the formation of the high-orientation crystals in the hot stretching process of the gel film can be more easily and accurately controlled;

4. The magnification of the single-axis high-temperature super-heat stretching of the gel film is 10-15 times, so that the fibrous extended chain crystal in the ultra-high molecular weight polyethylene resin can be oriented, the mechanical property of the ultra-high molecular weight polyethylene strip is ensured, and the stability of the single-axis high-temperature super-heat stretching of the gel film is not influenced.

Drawings

FIG. 1 is an X-ray diffraction pattern of an ultra high molecular weight polyethylene tape in example 1 of the present application.

FIG. 2 is an X-ray diffraction pattern of the ultra high molecular weight polyethylene tape of comparative example 1 of the present application.

Detailed Description

The present application will be described in further detail with reference to the accompanying drawings, examples and comparative examples.

Example 1

A method for forming ultra-high molecular weight polyethylene strips comprises the following steps,

Step 1, mixing ultra-high molecular weight polyethylene resin with the viscosity average molecular weight of 7.12 multiplied by 10 ⁶ g/mol and long straight-chain alkane according to the mass ratio of 0.32:1 to prepare uniform suspension, then sending the suspension into a double-screw extruder to be dissolved at high temperature to obtain solution, passing through a metering pump and a slot die head, and cooling and shaping the solution through a polishing cold roll at 20 ℃ to obtain a gel film;

step 3, immersing the stretched gel film into an extraction tank with ultrasonic waves to extract and remove long linear alkane, and drying by hot air to obtain a dried film;

step 4, longitudinally cutting the dried film to form a strip;

and 5, uniaxially and thermally stretching the strip at the temperature of 135 ℃ to remove pores, wherein the stretching ratio is 3 times, so that the final ultra-high molecular weight polyethylene strip is obtained.

Wherein the temperature of the feeding section of the double-screw extruder is 105 ℃, the temperature of the compression section is 170 ℃, the temperature of the homogenizing section is 170 ℃, the temperature of the die head is 170 ℃, and the rotating speed of the double-screw extruder is 200r/min. The temperature of uniaxial super heat stretching of the gel film is 100 ℃, the stretching rate is 45m/min, and the stretching ratio is 10 times. The long linear alkane may be a C12 to C16 normal alkane, may be a single length linear normal alkane or a mixture of long linear alkanes, and is preferably n-pentadecane unless otherwise specified in the examples below.

Example 2

Step 1, mixing ultra-high molecular weight polyethylene resin with the viscosity average molecular weight of 7.12 multiplied by 10 ⁶ g/mol and decalin according to the mass ratio of 0.18:1 to prepare uniform suspension, then feeding the suspension into a double-screw extruder to be dissolved at high temperature to obtain solution, and cooling and shaping the solution through a metering pump and a slot die head by a polishing cold roller at 10 ℃ to obtain a gel film;

step 3, immersing the stretched gel film into an extraction tank with ultrasonic waves to extract and remove decalin, and drying by hot air to obtain a dried film;

step 4, longitudinally cutting the dried film to form a strip;

and 5, uniaxially and thermally stretching the strip at 120 ℃ to remove pores, wherein the stretching ratio is 4 times, so that the final ultra-high molecular weight polyethylene strip is obtained.

Wherein, the temperature of the feeding section of the double-screw extruder is 80 ℃, the temperature of the compression section is 130 ℃, the temperature of the homogenizing section is 130 ℃, the temperature of the die head is 130 ℃, and the rotating speed of the double-screw extruder is 30r/min. The temperature of uniaxial super heat stretching of the gel film is 90 ℃, the stretching speed is 5m/min, and the stretching ratio is 6 times.

Example 3

Step 1, mixing ultra-high molecular weight polyethylene resin with the viscosity average molecular weight of 7.12 multiplied by 10 ⁶ g/mol and white oil according to the mass ratio of 0.45:1 to prepare uniform suspension, then feeding the suspension into a double-screw extruder to be dissolved at high temperature to obtain solution, and cooling and shaping the solution through a metering pump and a slot die head by a polishing cold roller at the temperature of 30 ℃ to obtain a gel film;

step 3, immersing the stretched gel film into an extraction tank with ultrasonic waves to extract and remove white oil, and drying by hot air to obtain a dried film;

step 4, longitudinally cutting the dried film to form a strip;

And 5, uniaxially and thermally stretching the strip at 150 ℃ to remove pores, wherein the stretching ratio is 1.5 times, so that the final ultra-high molecular weight polyethylene strip is obtained.

Wherein, the temperature of the feeding section of the double-screw extruder is 130 ℃, the temperature of the compression section is 200 ℃, the temperature of the homogenizing section is 200 ℃, the temperature of the die head is 200 ℃, and the rotating speed of the double-screw extruder is 400r/min. The temperature of uniaxial super heat stretching of the gel film is 130 ℃, the stretching rate is 80m/min, and the stretching ratio is 18 times. Here, the white oil is 70 # white oil of Tandall TOTAL LYRAN C B.

Comparative example 1

The comparative example differs from example 1 only in that step 2 is not included and in step 5, multistage stretching is performed to 30 times at 120 to 150 ℃.

Comparative example 2

The comparative example differs from example 2 only in that step 2 is not included and in step 5, multistage stretching is performed to 24 times at 120 to 150 ℃.

Comparative example 3

The difference between this comparative example and example 3 is that step 2 is not included and step 5 is multi-stage stretched to 27 times at 120 to 150 ℃.

The ultra high molecular weight polyethylene tapes of examples 1 to 3 and comparative examples 1 to 3 were tested for tensile mechanical, thermal and crystallization properties by the following methods,

Thermal performance testing

Cutting the ultra-high molecular weight polyethylene strip into small blocks, weighing 5-10 mg, placing in a standard aluminum crucible, protecting by using dry nitrogen flow, testing the thermal performance of the ultra-high molecular weight polyethylene strip by using a Differential Scanning Calorimeter (DSC) device, heating from 25 ℃ to 200 ℃ at a heating rate of 10 ℃ per minute, and recording the thermal performance curve of the strip.

Crystallinity and orientation test

The crystallinity and orientation of the ultra-high molecular weight polyethylene tapes were tested by a wide angle X-ray diffraction (WAXD) device, with an X-ray wavelength of 0.124nm. The two-dimensional WAXD results were collected by Pilatus K detector with a resolution of 172X 172 μm ² and a detector-to-sample distance of 210mm. The obtained wasd data was processed using FIT2D software. And carrying out one-dimensional integration on the two-dimensional WAXD graph to obtain an intensity distribution curve in the 2 theta direction. And then carrying out peak-splitting fitting on the curve, and calculating the proportion of the amorphous region to the crystalline region, so as to calculate the crystallinity. The calculation formula is as follows, xc=Ac/(Ac+aa), wherein Ac and Aa respectively represent areas under the crystallization peak and the amorphous peak of the I (2 theta) -2 theta curve.

The crystal orientation degree of the ultrathin molecular weight polyethylene strip is measured by adopting the Hermas method, the stretching direction of the strip is taken as a reference direction, the crystal face is set as hkl, and the orientation parameters can be expressed as follows:

Wherein, phi is azimuth angle, and I (phi) is scattering intensity along azimuth angle. The degree of orientation f can be calculated by the following formula:

when f= -0.5, the normal direction of the crystal plane is perpendicular to the reference direction, when f=1, the normal direction of the crystal plane is parallel to the reference direction, and when f=0, the normal of the crystal plane is freely oriented.

Tensile mechanical property test:

The tensile mechanical property test of ultra-high molecular weight polyethylene strips was carried out at room temperature using a universal mechanical tester, and the strips were drawn at a speed of 50mm/min and subjected to mechanical property characterization using at least five samples for each strip to obtain the average and standard deviation.

According to the above-described detection method, test results of examples 1 to 3 and comparative examples 1 to 3 were obtained as shown in the following table 1:

TABLE 1

Detecting items	Example 1	Example 2	Example 3	Comparative example 1	Comparative example 2	Comparative example 3
							Melting point (° C)	150.5	148.2	149.1	145.5	143.0	144.2
Crystallinity (%)	96.9	94.4	95.2	93.1	91.1	92.0
							Degree of orientation	0.95	0.93	0.94	0.91	0.89	0.90
Tensile Strength (GPa)	5.04±0.25	4.29±0.21	4.64±0.22	3.51±0.18	3.10±0.16	3.31±0.17
							Tensile modulus (GPa)	185.16±9.32	152.67±7.68	159.74±7.89	132.3±6.58	121.8±6.02	125.8±6.12

As can be seen from the comparison of the test results of examples 1 to 3 and comparative examples 1 to 3, respectively, and the illustrations of fig. 1 and 2, when the gel film was subjected to uniaxial high temperature super heat stretching without removing the low molecular weight solvent, the fibrous extended chain crystal orientation was more easily maintained and the formation of highly oriented crystals such as the subsequent extended chain crystals was more easily promoted, thereby effectively improving the tensile strength and tensile modulus of the final ultra high molecular weight polyethylene tape.

Example 4

This comparative example differs from example 1 only in that the compression section, homogenization section and die temperature of the twin screw extruder are 200 ℃.

Example 5

This comparative example differs from example 1 only in that the compression section, homogenization section and die temperature of the twin screw extruder are 130 ℃.

Comparative example 4

This comparative example differs from example 1 only in that the compression section, homogenization section and die temperature of the twin screw extruder are 120 ℃.

Comparative example 5

This comparative example differs from example 1 only in that the compression section, homogenization section and die temperature of the twin screw extruder are 210 ℃.

The ultra-high molecular weight tapes of examples 4 and 5 and comparative examples 4 and 5 were tested according to the test methods of table 1 above, and at the same time, the test results of ultra-high molecular weight polyethylene tapes are shown in table 2 below,

TABLE 2

Detecting items	Example 4	Example 5	Comparative example 4	Comparative example 5
					Melting point (° C)	150.6	148.1	/	145.2
Crystallinity (%)	96.8	93.4	/	91.4
					Degree of orientation	0.94	0.93	/	0.91
Tensile Strength (GPa)	4.89±0.29	4.14±0.24	/	3.45±0.19
					Tensile modulus (GPa)	178.23±11.25	140.34±8.98	/	134.65±6.68
Film formability	Film formation is more smooth and stable	Smooth and stable film formation	Can not smoothly and stably form a film	Smooth and stable film formation

As can be seen from comparison of the test results of examples 1, 4, 5 and comparative examples 4 and 5, the ultra-high molecular weight polyethylene tapes finally prepared have better tensile strength and tensile modulus when the temperatures of the compression section, the homogenizing section and the die head of the twin-screw extrusion are controlled to be 130-200 ℃, especially 130-170 ℃.

Example 6

This example differs from example 1 only in that the low molecular weight solvent is decalin.

Example 7

The only difference between this example and example 1 is that the low molecular weight solvent is white oil.

The ultra high molecular weight polyethylene tapes of example 6 and example 7 were tested according to the test methods of table 1 above, the test results are shown in table 3 below,

TABLE 3 Table 3

Detecting items	Example 6	Example 7
			Melting point (° C)	149.1	149
Crystallinity (%)	95.2	95
			Degree of orientation	0.94	0.94
Tensile Strength (GPa)	4.89±0.26	4.81±0.26
			Tensile modulus (GPa)	174.8±9.23	173.9±9.21

As can be seen from comparison of the detection results of examples 1, 6 and 7, the low molecular weight solvent is long linear alkane, which is favorable for improving the mechanical properties of the final ultra-high molecular weight polyethylene strip.

Example 8

The difference between this example and example 1 is that the uniaxial super heat stretching ratio of the jelly glue film is 15 times.

Example 9

The difference between this example and example 1 is that the uniaxial super heat stretching ratio of the jelly glue film is 6 times.

Example 10

The difference between this example and example 1 is that the jelly thin film was uniaxially super heat stretched at a stretch ratio of 18 times.

The ultra high molecular weight polyethylene tapes of examples 8 to 10 were tested according to the test method of table 1 above, the specific test results are shown in table 4 below,

TABLE 4 Table 4

Detecting items	Example 8	Example 9	Example 10
				Melting point (° C)	151.2	148.9	151.3
Crystallinity (%)	97.4	94.9	97.5
				Degree of orientation	0.96	0.93	0.96
Tensile Strength (GPa)	5.48±0.29	4.23±0.20	5.54±0.58
				Tensile modulus (GPa)	197.63±11.24	155.21±7.84	199.88±21.44
Film formability	Smooth and stable film formation	Smooth and stable film formation	Easy rupture of membranes in stretching process

By combining the detection results of the embodiment 1 and the embodiment 8 to the embodiment 10, when the stretching rate of the gel film by uniaxial super heat stretching is 10-15 times, the mechanical property of the ultra-high molecular weight polyethylene strip can be ensured, and meanwhile, the stretching stability of the ultra-high molecular weight polyethylene gel film is not influenced.

Example 11

The difference between this example and example 1 is only that the temperature of uniaxial super heat stretching of the jelly glue film is 120 ℃.

Example 12

The present example differs from example 1 only in that the temperature of uniaxial super heat stretching of the jelly glue film is 90 ℃.

Example 13

The difference between this example and example 1 is only that the temperature of uniaxial super heat stretching of the jelly glue film is 130 ℃.

The ultra high molecular weight polyethylene tapes of examples 11 to 13 were tested according to the test method of table 1 above, the specific test results are shown in table 5 below,

TABLE 5

Detecting items	Example 11	Example 12	Example 13
				Melting point (° C)	151.5	148.3	149.4
Crystallinity (%)	97.3	94.4	95.8
				Degree of orientation	0.96	0.93	0.94
Tensile Strength (GPa)	5.42±0.25	4.42±0.28	4.82±0.26
				Tensile modulus (GPa)	195.65±9.37	164.18±10.52	179.54±10.24

As can be seen from comparison of the detection results of examples 1, 11 to 13, when the temperature of uniaxial super thermal stretching of the gel film is 100-120 ℃, the reserved extended chain crystals can be rapidly oriented, the formation of subsequent high-oriented crystals is promoted, and the molecular chains in the gel film are not easy to be detangled in the stretching process, and the thermal stretching process is stable, so that the mechanical property of the finally obtained ultra-high molecular weight polyethylene strip is better.

The present embodiment is only for explanation of the present application and is not to be construed as limiting the present application, and modifications to the present embodiment, which may not creatively contribute to the present application as required by those skilled in the art after reading the present specification, are all protected by patent laws within the scope of claims of the present application.

Claims

1. A molding method of ultra-high molecular weight polyethylene strips is characterized by comprising the following steps,

Step 1, mixing ultra-high molecular weight polyethylene resin and long linear alkane to prepare uniform suspension, extruding at high temperature, and cooling and shaping by a polishing cold roller at 20 ℃ to obtain a gel film;

Step 3, extracting the stretched gel film to remove long linear alkane, and drying the gel film by hot air to obtain a dried film;

step 4, longitudinally cutting the dried film to form a strip;

Step 5, carrying out low-multiple uniaxial hot stretching on the strip to remove pores, and obtaining a final ultra-high molecular weight polyethylene strip;

Wherein the temperature of the uniaxial high-temperature super heat stretching in the step 2 is 90-130 ℃, the stretching speed is 5-80 m/min, the stretching ratio is 6-18 times, the high-temperature extrusion in the step 1 is realized by a double screw extruder, the temperature of a feeding section of the double screw extruder is 80-130 ℃, the temperature of a compression section is 130-170 ℃, the temperature of a homogenizing section is 130-170 ℃, the temperature of a die head is 130-170 ℃, the rotating speed of the double screw extruder is 30-400 r/min, and the mass ratio of the ultra-high molecular weight polyethylene resin to long linear alkane in the step 1 is (0.18-0.45): 1.

2. The method for forming a polyethylene tape with ultrahigh molecular weight according to claim 1, wherein the temperature of uniaxial high-temperature super-heat stretching of the gel film is 100-120 ℃.

3. The method for forming a polyethylene tape according to claim 1, wherein the stretching ratio in the uniaxial high temperature super heat stretching process is 10 to 15 times.

4. The method of claim 1, wherein the temperature of uniaxial hot stretching of the dried ultra-high molecular weight polyethylene strip is 120-150 ℃ and the stretching ratio is 1.5-4 times.