CN103980595B - A kind of modified ultra-high molecular weight polyethylene for 3D printing and preparation method thereof - Google Patents

Abstract

A 3D printing modified ultra-high molecular weight polyethylene material, the composition of which is as follows in parts by weight: 80-95 parts of ultra-high molecular weight polyethylene, 30-40 parts of low-density polyethylene, 10-15 parts of carbon nanotubes, and 1- 10 parts, modifier 1-5 parts, antioxidant 0.1-0.5 parts, coupling agent 0.1-0.5 parts; the modified UHMWPE material of the present invention has good melt fluidity, heat resistance and wear resistance properties, making ultra-high molecular weight polyethylene more in line with the characteristics of 3D printing materials, and making it have broad application prospects in 3D printing technology.

Description

A kind of modified ultra-high molecular weight polyethylene for 3D printing and preparation method thereof

technical field

The invention relates to a modified ultra-high molecular weight polyethylene material and a preparation method thereof, in particular to a modified ultra-high molecular weight polyethylene material for 3D printing and a preparation method thereof.

Background technique

3D printing technology mainly includes SLA, FDM, SLS, LOM and other processes. Among them, both fused deposition modeling (FDM) and selective laser sintering (SLS) technologies use thermoplastics as the basic 3D printing materials.

As a thermoplastic engineering plastic with a very high molecular weight with a linear structure, the molecular structure of ultra-high molecular weight polyethylene (UHMWPE) is basically the same as that of ordinary polyethylene materials. However, due to its high molecular weight, UHMWPE has excellent impact resistance, wear resistance, self-lubrication, chemical corrosion resistance and other properties that are unparalleled by other plastics. Moreover, UHMWPE has excellent low temperature resistance, and still has high impact strength at -40°C, and can even be used at -269°C. The excellent physical and mechanical properties of UHMWPE make it widely used in the fields of machinery, transportation, textile, paper, mining, construction, military, agriculture, chemical and sports equipment, among which large packaging containers and pipes are the most widely used. In addition, due to the excellent physiological inertia of UHMWPE, it has been used in clinical medicine as heart valves, orthopedic parts, artificial joints, etc.

Although UHMWPE has many excellent properties, it also has many shortcomings. UHMWPE has extremely high molecular weight, and its molecular chain is very long. The entanglement of extremely long molecular chains will cause its melt to be a rubber-like high-viscosity elastomer, with poor fluidity and prone to shear fracture. Low melt flow rate (MFR) (almost zero), high melting point (190-210°C), high viscosity, extremely difficult to process and shape, etc. In addition, compared with other engineering plastics, it has the disadvantages of low surface hardness, low heat distortion temperature, poor bending strength and creep resistance, poor wear resistance, and low strength, which makes the molding and processing of UHMWPE very difficult and serious. It hinders its application, making it not ideal as a 3D printing material.

CN1433443A relates to a method of forming a composite with nanofibers embedded in a polymer matrix, the method comprising mixing nanofibers in a plastic matrix to form agglomerates, and uniformly distributing the nanofibers by subjecting the agglomerates to hydrodynamic stress ; the hydrodynamic stress breaks apart the agglomerates, which in combination with additional extensional flow can be used to achieve small diameters and alignments. The resulting composite can be formed using fused deposition (FDM), where a roll of nanofiber-reinforced polymer is used as the wire feedstock for the FDM process. In this process, nanofiber composite threads (approximately 2 mm in diameter) are extruded through a millimeter-sized die, producing rows of composite threads to make sheets and 3D parts. The raw material used in this patent is a nanofiber-reinforced polymer wire. The disadvantage is that the FDM of the nanofiber composite wire is very complicated and difficult to handle.

CN1812878A relates to a powder suitable for 3D printing, the powder includes a blend of thermoplastic particles and binder particles, wherein the thermoplastic particles can be selected from polyolefins. When the patented powder is used for 3D printing, a solvent is required. Therefore, the 3D printing system of CN1812878A is a liquid composition, and its disadvantage is that it needs to use solvents or dispersants that are harmful to humans and the environment in many cases, and the operation is complicated, and it is not easy to uniformly disperse or dissolve.

CN102093646A relates to a material for 3D printing rapid prototyping and its preparation method. The rapid prototyping material includes a modified powder material A and a binder B, wherein: the preparation of the modified powder material A: adding the powder material and the first solvent Grind in a ball mill or grinder to obtain a powder material pretreatment material; add surfactants, lubricants, and organic resins to the second solvent one by one, stir and disperse for 2-3 hours to obtain a modified liquid; powder material pretreatment material Mix with modifying liquid, put into a grinder, mix and grind at room temperature, dry, grind and pulverize to obtain modified powder material A; when used, 1 part of modified powder material A is mixed with 0.01-0.07 part of binder B. The 3D molding system used in this patent is a solution system, and its disadvantage is that the material needs to be ground and modified during the preparation process, and supercritical drying is used, which makes the operation complicated.

US2004/0232583A1 relates to a method of manufacturing a three-dimensional object comprising: a) providing a layer of a powdery substrate; b) selectively applying at least one microwave-absorbing first Sensitive substances; c) treating said layer at least once with microwave radiation. Therein it is broadly mentioned that the group selected from polyester, polyvinyl chloride, polyacetal, polypropylene, polyethylene, polystyrene, polycarbonate, PMMI, PMMA, ionomer, polyamide, copolyester, copoly Polymers of amides, terpolymers, ABS or mixtures thereof. US2004/0232583A1 is silent on modifying polyethylene to make it suitable for 3D printing.

US3,847,888 relates to an ultra-high molecular weight linear polyethylene having a molecular weight of at least 1×10 ⁶ and a density of 0.92-0.99. It does not mention the application of the ultra-high molecular weight linear polyethylene in 3D printing materials.

None of the prior art mentions the modification of ultra-high molecular weight polyethylene to make it suitable for 3D printing. Therefore, the purpose of the present invention is to propose a method for improving the melt fluidity of UHMWPE materials in view of the current characteristics of low melt flow rate, high viscosity, poor fluidity and extremely difficult to be processed by injection molding. By adding an appropriate amount of low-density polyethylene, flow modifier, coupling agent and inorganic filler, etc., the melt fluidity of the material can be improved, and its mechanical properties such as heat resistance and wear resistance can be improved at the same time. The MFR value of the obtained material is increased from almost zero to more than 2g/10min (the experimental method is carried out according to GB/T3682-2000 (ISO1133)), making it suitable for use as a 3D printing material.

Contents of the invention

The present invention relates to a modified ultra-high molecular weight polyethylene material for 3D printing, which comprises the following components in parts by weight, preferably consists of the following components:

The ultra-high molecular weight polyethylene is commercially available, its molecular weight can be greater than 1.5 million, for example, 1.5-3 million, its density is between 0.93-0.96 g/cm ³ , and its heat distortion temperature is 85-90°C. The usage amount of the ultra-high molecular weight polyethylene is preferably 82-92 parts, more preferably 85-90 parts.

The low-density polyethylene is polyethylene produced by high-pressure polymerization, which is commercially available, and its density is usually 0.93-0.95 g/cm ³ , and its melt index is usually 2.0-2.10 g/10min. The dosage of the low-density polyethylene is preferably 30-38 parts, more preferably 30-35 parts.

The carbon nanotubes can be various carbon nanotubes, such as single-walled carbon nanotubes and multi-walled carbon nanotubes. The inventors surprisingly found that the carbon nanotubes are activated by nitric acid in a conventional method, and the specific surface area of the carbon nanotubes can be greatly increased by the nitric acid activation, and the active sites can be increased to improve the dispersibility in the matrix. The specific process of nitric acid activation is to reflux the carbon nanotubes in concentrated nitric acid (65%) for 2h-2.5h while dispersing (such as stirring, ultrasonic dispersion, preferably ultrasonic dispersion), and then washing with distilled water until neutral. The amount of the carbon nanotubes is preferably 10-14 parts, more preferably 10-13 parts.

The inorganic filler is selected from molybdenum disulfide, glass microspheres, talcum powder and superfine silicon micropowder. Preferably, the molybdenum disulfide is molybdenum disulfide particles with a particle size of 1000-1500 mesh. Preferably, the glass microspheres are glass microspheres with a particle size of 10-50 microns and a wall thickness of 1-2 microns. Preferably, the fineness of the talc powder is not less than 5000 mesh. Preferably, the particle size of the ultrafine silica powder is 0.1-0.3 microns. The amount of the inorganic filler is preferably 1-8 parts, more preferably 1-5 parts.

The modifier is selected from polyesters or poly(meth)acrylates. The polyester is for example polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN) or polybutylene naphthalate alcohol esters (PBN). The poly(meth)acrylate can be polymethyl(meth)acrylate, polyethyl(meth)acrylate, poly(propyl)acrylate, polybutyl(meth)acrylate, poly(meth)acrylate base) cyclohexyl acrylate, etc. The dosage of the modifier is preferably 1-4 parts, more preferably 1-3 parts.

In a preferred embodiment, the modified ultrahigh molecular weight polyethylene material of the present invention also contains an antioxidant. Preferably, the antioxidant is antioxidant CA. Its amount is 0.1-0.5 parts, preferably 0.1-0.4 parts.

In another preferred embodiment, the modified ultra-high molecular weight polyethylene material of the present invention also contains a coupling agent. The coupling agent is selected from titanate and silane. The titanate can be isopropyl tris(isostearyl) titanate, isopropyl tris(dioctyl pyrophosphate) titanate or bis(dioctyl pyrophosphoryl)oxyacetate titanium, Preferred is isopropyl tris(isostearyl) titanate. The silane is preferably a KH-550 type silane coupling agent. The selected coupling agent can reduce the viscosity of the synthetic resin melt, improve the dispersion of the filler to improve the processing performance, and then make the product obtain good surface quality and mechanical, thermal and electrical properties. The dosage of the coupling agent is 0.1-0.5 part, preferably 0.1-0.4 part.

In one aspect of the present invention, it also relates to the use of the modified ultra-high molecular weight polyethylene material of the present invention in 3D printing.

In another aspect of the present invention, it also relates to a 3D printing method characterized by using the modified ultra-high molecular weight polyethylene material of the present invention.

The present invention also relates to a method for preparing the modified ultra-high molecular weight polyethylene material for 3D printing of the present invention, which is characterized in that each component is extruded and granulated.

The present inventors have surprisingly found that if the inorganic filler is first mixed with a solution of modifier and coupling agent, then the resulting mixture is mixed with other components of the composite material of the present invention after drying, and the resulting mixture Extrusion granulation, thereby obtaining a composite material with uniform dispersion, and the obtained composite material has excellent melt flow rate, which is very suitable for 3D printing.

More specifically, the method has the following process steps:

1) Disperse the inorganic filler in the dispersion medium, then add modifier and coupling agent, disperse and dry;

2) mixing ultra-molecular weight polyethylene, low-density polyethylene, carbon nanotubes, the inorganic filler and antioxidant obtained in step 1);

3) Extruding pellets obtained in step 2) to obtain a modified ultra-high molecular weight polyethylene material.

In step 1), the inorganic filler is preferably dried before being dispersed into the dispersion medium. The dispersion medium used in step 1) can be ethanol, water, acetone, preferably ethanol. The dispersion can be carried out by means of stirring, ultrasonic dispersion, preferably by means of ultrasonic dispersion.

In step 2), the mixing can be performed in a high-speed mixer.

The extrusion granulation in step 3) can be performed using a single-screw extruder or a twin-screw extruder. In the case of using a twin-screw extruder, the extrusion process parameters are: the temperature distribution of each section of the barrel from the feed inlet to the die is 230-240, 240-250, 250-260, 250-260, 240- 250, 240-250°C, the host speed is 300-350r/min.

In a preferred embodiment, the present invention also relates to a method for preparing the modified ultra-high molecular weight polyethylene material for 3D printing of the present invention, characterized in that the method comprises the following process steps:

1) First dry the inorganic filler, disperse it in the dispersion medium, stir evenly, add modifier and coupling agent in proportion under stirring, and then stir evenly. Then vibrate and disperse in an ultrasonic oscillator, and dry to constant weight.

2) Mix ultra-molecular weight polyethylene, low-density polyethylene, carbon nanotubes, the mixture of inorganic filler, modifier and coupling agent obtained in step 1), and antioxidant in a high-speed mixer in proportion.

3) extruding and granulating step 2) to obtain modified UHMWPE.

Preferably, the preparation process of the modified ultra-high molecular weight polyethylene material is as follows:

1) First dry the inorganic filler at 160°C for 4 hours, weigh it and disperse it in the ethanol medium, stir it with an electric mixer for 30 minutes until it is uniform, add the modifier and coupling agent to the dispersion medium in proportion, and stir it for 30 minutes minutes until uniform. Then, shake and disperse in an ultrasonic oscillator for 1 hour, then dry to constant weight, and set aside.

2) Add ultra-molecular weight polyethylene, low-density polyethylene, carbon nanotubes, the inorganic filler obtained in step 1), and antioxidant to a high-speed mixer and mix evenly.

3) Put the material uniformly mixed in step 2) into a twin-screw extruder to extrude and granulate to prepare modified UHMWPE pellets. Extrusion process parameters: The temperature distribution of each section of the barrel from the feed port to the die is 230-240, 240-250, 250-260, 250-260, 240-250, 240-250°C, and the speed of the main engine is 300r/min.

In order to test, the pellets obtained in step 3 were also injection molded into standard samples through an injection molding machine. Injection molding process parameters: barrel temperature from the feed inlet to the die, the temperature distribution of each section of the barrel is 200-210, 210-220, 220-230, 230-240, 240-250, 245-255 ℃; injection pressure 45MPa; injection speed (gauge velocity) 30cm ³ /s; injection time 4s; cooling time 11s.

The outstanding features of the present invention are:

1. The modified UHMWPE material of the present invention has good melt fluidity (>2g/10min), which makes it very suitable for 3D printing.

2. The modified UHMWPE material of the present invention has high heat resistance and wear resistance.

3. The present invention has low production cost, simple production process and easy industrial production.

Detailed ways

The present invention will be further described in detail through specific embodiments below, but it should not be understood that the scope of the present invention is limited to the following examples. Without departing from the above-mentioned method idea of the present invention, various replacements or changes made according to common technical knowledge and customary means in this field shall be included in the scope of the present invention.

As used herein, "parts" and percentages are by weight unless otherwise specified.

The MFR test is carried out in accordance with GSB15-1312-2012, the Izod impact strength and Izod notched impact strength test are carried out in accordance with GB1043-79, the tensile strength is carried out in accordance with GBT1040-2006, the elongation at break test is carried out in accordance with ISO6239, and the thermal deformation temperature test is carried out in accordance with GB/T1633-2000 is implemented, and the friction coefficient test is implemented according to GB10006-1988. In the following examples, the carbon nanotubes used are carbon nanotubes activated with nitric acid, and the specific process is as follows: the carbon nanotubes are refluxed in concentrated nitric acid (65%) for 2 hours while ultrasonically dispersed, and then washed to medium with distilled water. sex.

Example 1

1) First dry molybdenum disulfide at 160°C for 4 hours, weigh and disperse in ethanol medium, stir with electric mixer for 30 minutes until uniform, 5 parts of modifier polymethyl methacrylate, 0.2 parts of coupling Add isopropyl tri(isostearyl) titanate into the dispersion medium, and stir for another 30 minutes until uniform. Then, shake and disperse in an ultrasonic oscillator for 1 hour, then dry to constant weight, and set aside.

2) 95 parts by weight of UHMWPE, 30 parts of low density polyethylene, 10 parts of carbon nanotubes, 5 parts of molybdenum disulfide, 0.1 part of antioxidant CA, and the product obtained in step 1) are added to the high-speed Mix evenly in a mixer, fully mix and grind for 1 hour and then discharge.

3) Add the mixture obtained in step 2) into a twin-screw extruder with an aspect ratio of 36 to extrude and granulate to prepare UHMWPE pellets. The residence time of the material in the extruder was 3 minutes. The temperature of the extruder is set in order: the temperature distribution of each section of the barrel from the feed port to the die is 230, 240, 250, 250, 240, and 240 °C, and the speed of the main engine is 300r/min.

4) Inject the pellets obtained in step 3) into a standard sample through an injection molding machine. Injection molding process parameters: the temperature distribution of each section of the barrel from the feed port to the die is 200, 210, 220, 230, 240, 245 ° C; injection pressure 45MPa; injection speed (gauge speed) 30cm ³ /s; injection time 4s; Cooling time 11s.

The main properties of pure UHMWPE and modified UHMWPE-1 were tested, and the test results are as follows:

Test items Pure UHMWPE Modified UHMWPE-1 MFR/(10min) ^-1 0 2.54 Izod impact strength/kJ m ^-2 not broken 90 Notched Izod Impact Strength/kJ·m ^-2 10 70 Tensile strength/MPa 34 twenty two Elongation at break/% 350 380 Heat distortion temperature/℃ 85 80 coefficient of friction 0.07 0.32

Example 2

1) 90 parts by weight of UHMWPE, 35 parts of low-density polyethylene, 10 parts of carbon nanotubes, 10 parts of talcum powder, 2 parts of polymethyl methacrylate, 0.5 parts of antioxidant CA, 0.5 parts of iso Propyl tri(isostearyl) titanate was added into a high-speed mixer and mixed uniformly, fully mixed and ground for 1 hour, and then discharged.

2) Add the mixture obtained in step 1) into a twin-screw extruder with an aspect ratio of 36 to extrude and granulate to prepare UHMWPE pellets. The residence time of the material in the extruder was 5 minutes. The temperature of the extruder is set in order: the temperature distribution of each section of the barrel from the feed port to the die is 235, 245, 250, 255, 240, 240 °C, and the speed of the main engine is 300r/min.

3) The pellets obtained in step 3 are injection molded into a standard sample through an injection molding machine. Injection molding process parameters: the temperature distribution of each section of the barrel from the feed port to the die is 205, 215, 220, 235, 240, and 250°C; the injection pressure is 45MPa; the injection speed (gauge speed) is 30cm ³ /s; the injection time is 4s; Cooling time 11s.

The main properties of pure UHMWPE and modified UHMWPE-2 were tested, and the test results are as follows:

Test items Pure UHMWPE Modified UHMWPE-2 MFR/(10min) ^-1 0 2.04 Izod impact strength/kJ m ^-2 not broken 88 Notched Izod Impact Strength/kJ·m ^-2 10 62 Tensile strength/MPa 34 twenty two Elongation at break/% 350 410 Heat distortion temperature/℃ 85 83.2 coefficient of friction 0.09 0.25

Example 3

1) 95 parts by weight of UHMWPE, 40 parts of low-density polyethylene, 15 parts of carbon nanotubes, 10 parts of glass beads, 3 parts of polymethyl methacrylate, 0.5 parts of antioxidant CA, 0.5 parts of silane are added to Mix evenly in a high-speed mixer, fully mix and grind for 1 hour and then discharge.

2) Add the mixture obtained in step 1) into a twin-screw extruder with an aspect ratio of 36 to extrude and granulate to prepare UHMWPE pellets. The residence time of the material in the extruder was 5 minutes. The temperature of the extruder is set in order: the temperature distribution of each section of the barrel from the feed port to the die is 240, 250, 260, 260, 250, 250 °C, and the main engine speed is 300r/min.

3) The pellets obtained in step 3 are injection molded into a standard sample through an injection molding machine. Injection molding process parameters: the temperature distribution of each section of the barrel from the feed port to the die is 210, 220, 230, 240, 250, and 255°C; the injection pressure is 45MPa; the injection speed (gauge speed) is 30cm ³ /s; the injection time is 4s; Cooling time 11s.

The main properties of pure UHMWPE and modified UHMWPE-3 were tested.

The result is as follows:

Test items Pure UHMWPE Modified UHMWPE-3 MFR/(10min) ^-1 0 2.45 Izod impact strength/kJ m ^-2 not broken 92 Notched Izod Impact Strength/kJ·m ^-2 10 67 Tensile strength/MPa 34 twenty four Elongation at break/% 350 385 Heat distortion temperature/℃ 85 80 coefficient of friction 0.10 0.28

Example 4

1) 80 parts by weight of UHMWPE, 40 parts of low-density polyethylene, 15 parts of carbon nanotubes, 10 parts of silicon micropowder, 5 parts of poly(meth)ethyl acrylate, 0.3 parts of antioxidant CA, 0.1 parts Parts of silane were added to a high-speed mixer and mixed evenly, fully mixed and ground for 1 hour, and then discharged.

2) Add the mixture obtained in step 1) into a twin-screw extruder with an aspect ratio of 36 to extrude and granulate to prepare UHMWPE pellets. The residence time of the material in the extruder was 3 minutes. The temperature of the extruder is set in order: the temperature distribution of each section of the barrel from the feed port to the die is 235, 250, 255, 260, 250, and 250°C, and the speed of the main engine is 300r/min.

3) The pellets obtained in step 3 are injection molded into a standard sample through an injection molding machine. Injection molding process parameters: the temperature distribution of each section of the barrel from the feed inlet to the die is 200, 215, 230, 235, 240, and 255°C; the injection pressure is 45MPa; the injection speed (gauge speed) is 30cm ³ /s; the injection time is 4s; Cooling time 11s.

The main properties of pure UHMWPE and modified UHMWPE-4 were tested.

The result is as follows:

Test items Pure UHMWPE Modified UHMWPE-4 MFR/(10min) ^-1 0 3.36 Izod impact strength/kJ m ^-2 not broken 98 Notched Izod Impact Strength/kJ·m ^-2 10 69

Tensile strength/MPa 34 twenty four Elongation at break/% 350 421 Heat distortion temperature/℃ 85 74 coefficient of friction 0.10 0.26

It can be seen from the above examples that by adding an appropriate amount of low-density polyethylene, flow modifier, coupling agent and inorganic filler, the melt fluidity of the melt is greatly improved, and its heat resistance and wear resistance are improved at the same time. Mechanical properties such as resistance make it suitable for use as 3D printing materials.

Claims (14)

1. The use of modified ultra-high molecular weight polyethylene material in 3D printing, characterized in that the modified ultra-high molecular weight polyethylene material comprises the following components in parts by weight: 2. The use according to claim 1, characterized in that the carbon nanotubes are single-walled carbon nanotubes or multi-walled carbon nanotubes. 3. Use according to claim 1, characterized in that the carbon nanotubes are activated with nitric acid. 4. The use according to claim 1, characterized in that the inorganic filler is selected from molybdenum disulfide, glass microspheres, talcum powder or ultrafine silicon micropowder. 5. Use according to claim 1, characterized in that the modifying agent is selected from polyesters or poly(meth)acrylates. 6. The use according to claim 1, characterized in that the modified ultra-high molecular weight polyethylene material also contains an antioxidant. 7. The use according to claim 1, characterized in that said modified ultra-high molecular weight polyethylene material also contains a coupling agent. 8. A 3D printing method, characterized in that using a modified ultra-high molecular weight polyethylene material, characterized in that the modified ultra-high molecular weight polyethylene material comprises the following components in parts by weight: 9. The method according to claim 8, characterized in that the carbon nanotubes are single-walled carbon nanotubes or multi-walled carbon nanotubes. 10. The method according to claim 8, characterized in that the carbon nanotubes are activated with nitric acid. 11. The method according to claim 8, characterized in that the inorganic filler is selected from molybdenum disulfide, glass microspheres, talcum powder or ultrafine silicon micropowder. 12. The method according to claim 8, characterized in that the modifying agent is selected from polyesters or poly(meth)acrylates. 13. The method according to claim 8, characterized in that said modified ultra-high molecular weight polyethylene material also contains an antioxidant. 14. The method according to claim 8, characterized in that said modified ultra-high molecular weight polyethylene material also contains a coupling agent.