CN113912968A - Heat-resistant modified PTFE (polytetrafluoroethylene) heat-shrinkable material as well as preparation method and application thereof - Google Patents
Heat-resistant modified PTFE (polytetrafluoroethylene) heat-shrinkable material as well as preparation method and application thereof Download PDFInfo
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- C08J2427/12—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers not modified by chemical after-treatment containing fluorine atoms
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Abstract
The invention belongs to the field of materials, and particularly relates to a heat-resistant modified PTFE (polytetrafluoroethylene) heat-shrinkable material as well as a preparation method and application thereof. The heat-resistant modified PTFE heat-shrinkable material provided by the invention is prepared by mixing raw materials, performing, removing an extrusion aid, sintering, quenching, crosslinking modification and expanding and shaping; the raw materials comprise, by mass: 90-100 parts of PTFE resin; 0-15 parts of PFA resin; 10-30 parts of extrusion aid; 2-30 parts of rare earth oxide; 2-10 parts of wear-resistant filler. According to the invention, the rare earth oxide is introduced into the PTFE heat-shrinkable material, so that the damage of free radicals in the system to PTFE molecular chains is effectively reduced, and the thermal stability of the matrix is improved; and a specific preparation process is combined, so that the high-temperature resistance of the material is further improved, and the requirement of long-time use at the high temperature of 350 ℃ can be met.
Description
Technical Field
The invention belongs to the field of materials, and particularly relates to a heat-resistant modified PTFE (polytetrafluoroethylene) heat-shrinkable material as well as a preparation method and application thereof.
Background
The high-temperature-resistant heat-shrinkable tube is a heat-shrinkable protective sleeve capable of bearing an extremely high-temperature environment, can be tightly bound on the outer layer of a wrapped object after being heated to provide the effects of mechanical protection, insulation, corrosion resistance and the like, is widely applied to the fields of aerospace, electronic power, automobiles, machinery, communication, rail transit, petrochemical industry and the like, takes an aircraft engine environment as an example, a wiring system in an engine area is subjected to the erosion of various high-temperature fuel media for a long time, and needs to provide external protection by means of a special high-temperature-resistant heat-shrinkable tube.
The temperature resistance grade of the existing high-temperature-resistant heat-shrinkable tube is generally-65-260 ℃, and effective external protection cannot be provided in a high-temperature environment above 260 ℃, so that development of a heat-shrinkable tube with more excellent high-temperature resistance is necessary.
Disclosure of Invention
In view of the above, the present invention provides a heat-resistant modified PTFE heat-shrinkable material, and a preparation method and an application thereof.
The invention provides a heat-resistant modified PTFE (polytetrafluoroethylene) heat-shrinkable material which is prepared by mixing raw materials, performing, removing an extrusion aid, sintering, quenching, crosslinking modification and expanding and shaping; the raw materials comprise, by mass:
the rare earth oxide is one or more of cerium dioxide, cerium oxide, lanthanum oxide, zirconium dioxide and yttrium oxide.
Preferably, the surface of the rare earth oxide is subjected to an organosilication treatment.
Preferably, the compression ratio of the PTFE resin is (400-1500): 1.
preferably, the PFA resin has a melt index of 14 to 70g/10 min.
Preferably, the extrusion aid is one or more of toluene, petroleum ether, kerosene and isoparaffin.
Preferably, the wear-resistant filler is one or more of aluminum oxide, silicon dioxide, calcium oxide, silicon carbide, silicon nitride and kaolin.
The invention provides a preparation method of a heat-resistant modified PTFE (polytetrafluoroethylene) heat-shrinkable material, which comprises the following steps of:
a) mixing 90-100 parts by mass of PTFE resin, 0-15 parts by mass of PFA resin, 10-30 parts by mass of extrusion aid, 2-30 parts by mass of rare earth oxide and 2-10 parts by mass of wear-resistant filler to obtain paste-like master batch;
b) performing the paste-like master batch to obtain a preformed piece;
c) removing the extrusion aid in the preformed piece, and then sintering to obtain a sintered piece;
d) quenching the sintered part to obtain a quenched part;
e) carrying out cross-linking modification treatment on the quenching piece to obtain a heat-resistant modified PTFE heat-shrinkable material semi-finished product;
f) and expanding and shaping the semi-finished product of the heat-resistant modified PTFE heat-shrinkable material to obtain the heat-resistant modified PTFE heat-shrinkable material.
Preferably, in the step d), the quenching treatment specifically comprises:
the sintered part is subjected to a heating treatment and then rapidly cooled down.
Preferably, in step e), the method for the crosslinking modification treatment is irradiation; the irradiation equipment is Co-60 radioactive source irradiation equipment or a high-energy electron accelerator; the irradiation atmosphere is nitrogen or argon; the irradiation dose is 5-100 Mard; the irradiation dose rate is 5-50 kGy/h.
The invention provides a heat-resistant modified PTFE heat shrinkable tube which is made of the heat-resistant modified PTFE heat shrinkable material in the technical scheme or the heat-resistant modified PTFE heat shrinkable material prepared by the preparation method in the technical scheme.
Compared with the prior art, the invention provides a heat-resistant modified PTFE heat-shrinkable material and a preparation method and application thereof. The heat-resistant modified PTFE heat-shrinkable material provided by the invention is prepared by mixing raw materials, performing, removing an extrusion aid, sintering, quenching, crosslinking modification and expanding and shaping; the raw materials comprise, by mass: 90-100 parts of PTFE resin; 0-15 parts of PFA resin; 10-30 parts of extrusion aid; 2-30 parts of rare earth oxide; 2-10 parts of wear-resistant filler; the rare earth oxide is one or more of cerium dioxide, cerium oxide, lanthanum oxide, zirconium dioxide and yttrium oxide. According to the invention, the rare earth oxide is introduced into the PTFE heat-shrinkable material, so that the damage of free radicals in the system to PTFE molecular chains is effectively reduced, and the thermal stability of the matrix is improved; and a specific preparation process is combined, particularly, crosslinking modification is carried out, so that a crosslinking structure is formed in the material, and the high temperature resistance of the material is further improved by combining the antioxidation effect of the rare earth oxide, so that the material can meet the requirement of long-time use in a high-temperature environment of 350 ℃.
Detailed Description
The technical solutions in the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all 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 heat-resistant modified PTFE (polytetrafluoroethylene) heat-shrinkable material which is prepared by mixing raw materials, performing, removing an extrusion aid, sintering, quenching, crosslinking modification and expanding and shaping; the raw materials comprise, by mass:
in the heat-resistant modified PTFE heat-shrinkable material provided by the invention, in raw materials, the PTFE (polytetrafluoroethylene) resin is preferably a PTFE resin with a medium-high compression ratio, and the compression ratio is preferably (400-1500): 1, specifically 400:1, 450:1, 500:1, 550:1, 600:1, 650:1, 700:1, 750:1, 800:1, 850:1, 900:1, 950:1, 1000:1, 1050:1, 1100:1, 1150:1, 1200:1, 1250:1, 1300:1, 1350:1, 1400:1, 1450:1, or 1500: 1.
In the heat-resistant modified PTFE heat-shrinkable material provided by the invention, the content of the PTFE resin can be 90 parts by mass, 91 parts by mass, 92 parts by mass, 93 parts by mass, 94 parts by mass, 95 parts by mass, 96 parts by mass, 97 parts by mass, 98 parts by mass, 99 parts by mass or 100 parts by mass.
In the raw materials of the heat-resistant modified PTFE heat-shrinkable material provided by the invention, the melt index of the PFA (fusible polytetrafluoroethylene) resin is preferably 14-70 g/10min, more preferably 14-30 g/10min, and specifically can be 14g/10min, 20g/10min, 25g/10min, 30g/10min, 35g/10min, 40g/10min, 45g/10min, 50g/10min, 55g/10min, 60g/10min, 65g/10min or 70g/10 min; the density of the PFA resin is preferably 1.5-3 g/cm3More preferably 2.14 to 2.16g/cm3Specifically, it may be 1.5g/cm3、1.6g/cm3、1.7g/cm3、1.8g/cm3、1.9g/cm3、2g/cm3、2.1g/cm3、2.14g/cm3、2.16g/cm3、2.2g/cm3、2.3g/cm3、2.4g/cm3、2.5g/cm3、2.6g/cm3、2.7g/cm3、2.8g/cm3、2.9g/cm3Or 3g/cm3。
In the heat-resistant modified PTFE heat-shrinkable material provided by the present invention, the content of the PFA resin may be specifically 0 part by mass, 1 part by mass, 2 parts by mass, 3 parts by mass, 4 parts by mass, 5 parts by mass, 6 parts by mass, 7 parts by mass, 8 parts by mass, 9 parts by mass, 10 parts by mass, 11 parts by mass, 12 parts by mass, 13 parts by mass, 14 parts by mass, or 15 parts by mass in the raw material.
In the heat-resistant modified PTFE heat-shrinkable material provided by the invention, in raw materials, the extrusion assistant is preferably one or more of toluene, petroleum ether, kerosene and isoparaffin; the boiling range of the petroleum ether is preferably 40-120 ℃, more preferably 50-100 ℃, and most preferably 60-90 ℃; the isoparaffin is preferably Isopar G mineral spirits, which is supplied by exxonmobil.
In the raw material of the heat-resistant modified PTFE heat-shrinkable material provided by the invention, the content of the extrusion aid can be 10 parts by mass, 11 parts by mass, 12 parts by mass, 13 parts by mass, 14 parts by mass, 15 parts by mass, 16 parts by mass, 17 parts by mass, 18 parts by mass, 19 parts by mass, 20 parts by mass, 21 parts by mass, 22 parts by mass, 23 parts by mass, 24 parts by mass, 25 parts by mass, 26 parts by mass, 27 parts by mass, 28 parts by mass, 29 parts by mass or 30 parts by mass.
In the raw materials of the heat-resistant modified PTFE heat-shrinkable material provided by the invention, the rare earth element in the rare earth oxide has a special outer electronic layer structure, and the introduction of the rare earth element into the PTFE heat-shrinkable material can influence the thermal degradation reaction of PTFE, effectively reduce the damage of free radicals in the system to PTFE molecular chains and improve the thermal stability of the PTFE heat-shrinkable material. In the invention, the rare earth oxide is cerium dioxide, cerium oxide and lanthanum oxide (La)2O3) Zirconium dioxide and yttrium oxide (Y)2O3) One or more of; the particle size of the rare earth oxide is preferably 10-100 nm, and specifically can be 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm or 100 nm. In the present invention, the surface of the rare earth oxide is preferably subjected to an organosilication treatment; the organosilicon reagent used for the organic silicification treatment is preferably epoxy trimethoxy silane and/or vinyl triethoxy silane; the preferable dosage ratio of the organic silicon reagent to the rare earth oxide is (100-200) mL:100g, specifically 100mL:100g, 110mL:100g, 120mL:100g, 130mL:100g, 140mL:100g, 150mL:100g, 160mL:100g, 170mL:100g, 180mL:100g, 190mL:100g or 200mL:100 g.
In the heat-resistant modified PTFE heat shrinkable material provided by the invention, in the raw material, the rare earth oxide is preferably surface organic silicification-treated cerium dioxide and/or surface organic silicification-treated yttrium oxide. Wherein the surface-organosilicated ceria is preferably prepared by the following steps:
firstly, cerium dioxide is dispersed in a liquid phase to obtain a dispersion liquid; then mixing the dispersion liquid with an organic silicon reagent for reaction; after the reaction is finished, carrying out solid-liquid separation, and carrying out post-treatment on the solid-phase product to obtain the cerium dioxide with the surface subjected to organic silicification treatment. The liquid phase preferably comprises ethanol and water, and the volume ratio of the ethanol to the water is preferably (5-15): 1, more preferably 9: 1; the amount ratio of the cerium oxide to the liquid phase is preferably 100 g: (50-300) mL, more preferably 100 g: 120 mL; the temperature of the dispersion is preferably 15-35 ℃, and more preferably 25 ℃; the dispersion is carried out under the condition of stirring, the rotating speed of the stirring is preferably 100-300 rpm, more preferably 180rpm, and the stirring time is preferably 10-40 min, more preferably 30 min; the organosilicon agent is preferably an epoxytrimethoxysilane; the temperature of the mixing reaction is preferably 40-60 ℃, and more preferably 50 ℃; the mixing reaction time is preferably 2-4 h, and more preferably 3 h; the mixing reaction is preferably carried out under the condition of stirring, and the rotating speed of the stirring is preferably 100-300 rpm, more preferably 200 rpm; the post-treatment step preferably comprises ethanol washing and drying, the drying mode is preferably vacuum drying, the drying temperature is preferably 50-80 ℃, more preferably 60 ℃, and the drying time is preferably 6-12 hours, more preferably 8 hours.
In the heat-resistant modified PTFE heat-shrinkable material provided by the invention, in the raw material, the yttrium oxide subjected to surface organic silicification treatment is preferably prepared according to the following steps:
firstly, mixing an organic silicon reagent with an alcohol-water mixed solution, then adjusting the pH value of the mixed solution to weak acidity, then mixing the weak acidic solution with yttrium oxide for reaction, carrying out solid-liquid separation, and carrying out post-treatment on a solid-phase product to obtain yttrium oxide with the surface subjected to organic silicification treatment. Wherein, the modifier is preferably vinyl triethoxysilane; the alcohol-water mixed solution preferably comprises ethanol and water, and the volume ratio of the ethanol to the water is preferably (5-15): 1, more preferably 9: 1; the volume ratio of the organic silicon reagent to the alcohol-water mixed solution is preferably 1: (0.5-2), more preferably 1: 1; the mixing temperature of the organic silicon reagent and the alcohol-water mixed solution is preferably 15-35 ℃, more preferably 25 ℃, the mixing stirring speed is preferably 50-150 rpm, more preferably 80rpm, and the mixing time is preferably 10-60 min, more preferably 30 min; the range of the weakly acidic pH value is preferably 5.5-6.5, and specifically can be 5.5, 5.6, 5.7, 5.8, 5.9, 6, 6.1, 6.2, 6.3, 6.4 or 6.5; the temperature of the mixing reaction is preferably 60-80 ℃, and more preferably 70 ℃; the mixing reaction time is preferably 4-8 h, and more preferably 6 h; the mixing reaction is preferably carried out under the condition of stirring, and the rotating speed of the stirring is preferably 50-200 rpm, more preferably 100 rpm; the post-treatment step preferably comprises ethanol washing and drying, the drying mode is preferably vacuum drying, the drying temperature is preferably 50-80 ℃, more preferably 60 ℃, and the drying time is preferably 6-12 hours, more preferably 8 hours.
In the heat-resistant modified PTFE heat-shrinkable material provided by the present invention, the content of the rare earth oxide may specifically be 2 parts by mass, 3 parts by mass, 4 parts by mass, 5 parts by mass, 6 parts by mass, 7 parts by mass, 8 parts by mass, 9 parts by mass, 10 parts by mass, 11 parts by mass, 12 parts by mass, 13 parts by mass, 14 parts by mass, 15 parts by mass, 16 parts by mass, 17 parts by mass, 18 parts by mass, 19 parts by mass, 20 parts by mass, 21 parts by mass, 22 parts by mass, 23 parts by mass, 24 parts by mass, 25 parts by mass, 26 parts by mass, 27 parts by mass, 28 parts by mass, 29 parts by mass, or 30 parts by mass in the raw material. In one embodiment of the present invention, the rare earth oxide is composed of surface organosilication-treated ceria and surface organosilication-treated yttria, wherein the content of the surface organosilication-treated ceria is preferably 5 to 20 parts by mass, and more preferably 10 parts by mass; the content of the surface-organosilicated yttrium oxide in the raw material is preferably 1 to 10 parts by mass, and more preferably 5 parts by mass.
In the raw materials of the heat-resistant modified PTFE heat-shrinkable material provided by the invention, the wear-resistant filler is preferably one or more of aluminum oxide, silicon dioxide, calcium oxide, silicon carbide, silicon nitride and kaolin; the particle size of the wear-resistant filler is preferably 30-100 nm, and specifically can be 30nm, 35nm, 40nm, 45nm, 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm, 95nm or 100 nm.
In the heat-resistant modified PTFE heat-shrinkable material provided by the invention, the content of the wear-resistant filler can be specifically 2 parts by mass, 2.5 parts by mass, 3 parts by mass, 3.5 parts by mass, 4 parts by mass, 4.5 parts by mass, 5 parts by mass, 5.5 parts by mass, 6 parts by mass, 6.5 parts by mass, 7 parts by mass, 7.5 parts by mass, 8 parts by mass, 8.5 parts by mass, 9 parts by mass, 9.5 parts by mass or 10 parts by mass.
In the heat-resistant modified PTFE heat-shrinkable material provided by the invention, the mixing temperature is preferably 10-25 ℃, and more preferably 15-18 ℃; the mixing speed is preferably 5-50 rpm, and more preferably 10-25 rpm; the mixing time is preferably 15-50 min, and more preferably 25-30 min. In the invention, in order to fully immerse the extrusion aid into the resin molecules, the extrusion aid is preferably kept stand for a period of time after the mixing is finished, the temperature of the standing is preferably 15-50 ℃, more preferably 25-35 ℃, and the time of the standing is preferably 12-48 hours, more preferably 24 hours.
In the heat-resistant modified PTFE heat-shrinkable material provided by the present invention, the specific process of preforming preferably comprises: the master batch obtained after mixing is firstly pressed into a blank material, and then the blank material is extruded by pushing to obtain a preformed piece. Wherein the pressing pressure is preferably 0.2-2 MPa, and more preferably 0.5-1.5 MPa; the compression speed of the pressing is preferably 20-60 mm/min, and more preferably 40-50 mm/min; the pressing temperature is preferably 20-40 ℃, and more preferably 30 ℃; the blank is preferably a tube blank; the pressure of the pushing extrusion is preferably 3-12 MPa, and more preferably 5-9 MPa; the push extrusion speed is preferably 50-150 mm/min, and more preferably 80-100 mm/min; the temperature of the extrusion is preferably 40-70 ℃, and more preferably 50-65 ℃.
In the heat-resistant modified PTFE heat-shrinkable material provided by the invention, the extrusion assistant removing mode is preferably hot baking; the temperature of the heat drying is preferably 150-300 ℃, and more preferably 180-240 ℃; the drawing speed of the hot drying is preferably 50-200 mm/min, and more preferably 100-150 mm/min. In the invention, the mixture is preferably kept stand for a period of time after the heat drying is finished, the temperature of the standing is preferably 15-50 ℃, more preferably 25-35 ℃, and the time of the standing is preferably 12-48 hours, more preferably 18-24 hours.
In the heat-resistant modified PTFE heat-shrinkable material provided by the invention, the sintering temperature is above the melting point of PTFE resin, preferably 280-400 ℃, and more preferably 300-380 ℃; the sintering speed is preferably 50-150 mm/min, and more preferably 100-130 mm/min.
In the heat-resistant modified PTFE heat-shrinkable material provided by the present invention, the specific process of the quenching treatment preferably includes: firstly, heating the sintered part obtained after sintering, and then quickly cooling. Wherein the temperature of the heating treatment is preferably 300-400 ℃, and more preferably 350-380 ℃; the rapid cooling reduction mode is preferably to place the heated workpiece in cold water, and the temperature of the cold water is preferably 0-15 ℃, and more preferably 5-10 ℃. In the present invention, the part subjected to rapid cooling down in the cold water is preferably dehydrated and dried after being taken out; the temperature of the dehydration drying is preferably 30-50 ℃, and more preferably 40 ℃; the time for dehydration and drying is preferably 6-18 h, and more preferably 8-12 h.
In the heat-resistant modified PTFE heat-shrinkable material provided by the invention, the crosslinking modification treatment method is preferably irradiation; the irradiation equipment is preferably Co-60 radioactive source irradiation equipment or a high-energy electron accelerator; the irradiation atmosphere is preferably nitrogen or argon; the irradiation dose is preferably 2-200 Mard, and more preferably 5-100 Mard; the irradiation dose rate is preferably 5-50 kGy/h, and more preferably 25 kGy/h.
In the heat-resistant modified PTFE heat-shrinkable material provided by the invention, the heating temperature for expansion and shaping is preferably 300-450 ℃, and more preferably 350-390 ℃; the expansion pressure for expansion shaping is preferably 1-10 bar, and more preferably 2-5 bar; the expansion shaping mode is preferably water-cooling shaping, and the water temperature of the water-cooling shaping is preferably 5-15 ℃, and more preferably 8-12 ℃. In the invention, after the water-cooling shaping is finished, dehydration drying is preferably carried out; the temperature of the dehydration drying is preferably 40-80 ℃, and more preferably 55-65 ℃; the time for dehydration and drying is preferably 12-48 h, and more preferably 24 h.
The invention also provides a preparation method of the heat-resistant modified PTFE heat-shrinkable material, which comprises the following steps:
a) mixing 90-100 parts by mass of PTFE resin, 0-15 parts by mass of PFA resin, 10-30 parts by mass of extrusion aid, 2-30 parts by mass of rare earth oxide and 2-10 parts by mass of wear-resistant filler to obtain paste-like master batch;
b) performing the paste-like master batch to obtain a preformed piece;
c) removing the extrusion aid in the preformed piece, and then sintering to obtain a sintered piece;
d) quenching the sintered part to obtain a quenched part;
e) carrying out cross-linking modification treatment on the quenching piece to obtain a heat-resistant modified PTFE heat-shrinkable material semi-finished product;
f) and expanding and shaping the semi-finished product of the heat-resistant modified PTFE heat-shrinkable material to obtain the heat-resistant modified PTFE heat-shrinkable material.
In the preparation method provided by the invention, in the step a), the specific types and the dosage of the raw material components are already introduced in the above, and are not described again; the mixing temperature is preferably 10-25 deg.C, more preferably 15-18 deg.C, and specifically can be 10 deg.C, 11 deg.C, 12 deg.C, 13 deg.C, 14 deg.C, 15 deg.C, 16 deg.C, 17 deg.C, 18 deg.C, 19 deg.C, 20 deg.C, 21 deg.C, 22 deg.C, 23 deg.C, 24 deg.C or 25 deg.C; the mixing speed is preferably 5-50 rpm, more preferably 10-25 rpm, and specifically may be 5rpm, 10rpm, 15rpm, 20rpm, 25rpm, 30rpm, 35rpm, 40rpm, 45rpm or 50 rpm; the mixing time is preferably 15-50 min, more preferably 25-30 min, and specifically can be 15min, 20min, 25min, 30min, 35min, 40min, 45min or 50 min.
In the preparation method provided by the invention, the step a) preferably specifically comprises the following steps:
a1) mixing 90-100 parts by mass of PTFE resin, 0-15 parts by mass of PFA resin and 10-30 parts by mass of extrusion aid to obtain a resin mixture;
a2) and mixing the resin mixture, 2-30 parts by mass of rare earth oxide and 2-10 parts by mass of wear-resistant filler to obtain the paste-like master batch.
In the preparation method provided by the invention, in the step a1), the mixing temperature is preferably 10-25 ℃, more preferably 15-18 ℃, and specifically 10 ℃, 11 ℃, 12 ℃, 13 ℃, 14 ℃, 15 ℃, 16 ℃, 17 ℃, 18 ℃, 19 ℃, 20 ℃, 21 ℃, 22 ℃, 23 ℃, 24 ℃ or 25 ℃; the mixing speed is preferably 5-50 rpm, more preferably 10-25 rpm, and specifically may be 5rpm, 10rpm, 15rpm, 20rpm, 25rpm, 30rpm, 35rpm, 40rpm, 45rpm or 50 rpm; the mixing time is preferably 10-30 min, more preferably 20-22 min, and specifically may be 10min, 11min, 12min, 13min, 14min, 15min, 16min, 17min, 18min, 19min, 20min, 21min, 22min, 23min, 24min, 25min, 26min, 27min, 28min, 29min or 30 min.
In the preparation method provided by the invention, in the step a2), the mixing temperature is preferably 10-25 ℃, more preferably 15-18 ℃, and specifically 10 ℃, 11 ℃, 12 ℃, 13 ℃, 14 ℃, 15 ℃, 16 ℃, 17 ℃, 18 ℃, 19 ℃, 20 ℃, 21 ℃, 22 ℃, 23 ℃, 24 ℃ or 25 ℃; the mixing speed is preferably 5-50 rpm, more preferably 10-25 rpm, and specifically may be 5rpm, 10rpm, 15rpm, 20rpm, 25rpm, 30rpm, 35rpm, 40rpm, 45rpm or 50 rpm; the mixing time is preferably 1-10 min, more preferably 5-8 min, and specifically may be 1min, 2min, 3min, 4min, 5min, 6min, 7min, 8min, 9min or 10 min.
In the preparation method provided by the invention, in the step a), in order to fully immerse the extrusion aid into the resin molecules, the extrusion aid is preferably kept standing for a period of time after the mixing is finished. Wherein the temperature of the standing is preferably 15-50 ℃, more preferably 25-35 ℃, and specifically can be 15 ℃, 20 ℃, 25 ℃, 30 ℃, 35 ℃, 40 ℃, 45 ℃ or 50 ℃; the standing time is preferably 12-48 h, more preferably 24h, and specifically can be 12h, 16h, 20h, 24h, 28h, 32h, 36h, 40h, 44h or 48 h.
In the preparation method provided by the present invention, in step b), the specific process of preforming preferably includes: the master batch obtained after mixing is firstly pressed into a blank material, and then the blank material is extruded by pushing to obtain a preformed piece. Wherein the pressing pressure is not excessively high, preferably 0.2 to 2MPa, more preferably 0.5 to 1.5MPa, and specifically may be 0.5MPa, 0.6MPa, 0.7MPa, 0.8MPa, 0.9MPa, 1MPa, 1.1MPa, 1.2MPa, 1.3MPa, 1.4MPa or 1.5 MPa; the compression speed of the pressing is preferably 20-60 mm/min, more preferably 40-50 mm/min, and specifically can be 40mm/min, 41mm/min, 42mm/min, 43mm/min, 44mm/min, 45mm/min, 46mm/min, 47mm/min, 48mm/min, 49mm/min or 50 mm/min; the pressing temperature is preferably 20-40 deg.C, specifically 20 deg.C, 21 deg.C, 22 deg.C, 23 deg.C, 24 deg.C, 25 deg.C, 26 deg.C, 27 deg.C, 28 deg.C, 29 deg.C, 30 deg.C, 31 deg.C, 32 deg.C, 33 deg.C, 34 deg.C, 35 deg.C, 36 deg.C, 37 deg.C, 38 deg.C, 39 deg.C or 40 deg.C; the equipment used for pressing is preferably a molding equipment; the blank is preferably a tube blank; the pushing extrusion preferably adopts a high-pressure low-speed mode; the pressure of the pushing extrusion is preferably 3-12 MPa, more preferably 5-9 MPa, and specifically can be 3MPa, 4MPa, 5MPa, 6MPa, 7MPa, 8MPa, 9MPa, 10MPa, 11MPa or 12 MPa; the extrusion speed is preferably 50-150 mm/min, more preferably 80-100 mm/min, and specifically can be 50mm/min, 55mm/min, 60mm/min, 65mm/min, 70mm/min, 75mm/min, 80mm/min, 85mm/min, 90mm/min, 95mm/min, 100mm/min, 105mm/min, 110mm/min, 115mm/min, 120mm/min, 125mm/min, 130mm/min, 135mm/min, 140mm/min, 145mm/min or 150 mm/min; the temperature of the extrusion is preferably 40 to 70 ℃, more preferably 50 to 65 ℃, and specifically 50 ℃, 51 ℃, 52 ℃, 53 ℃, 54 ℃, 55 ℃, 56 ℃, 57 ℃, 58 ℃, 59 ℃, 60 ℃, 61 ℃, 62 ℃, 63 ℃, 64 ℃ or 65 ℃; the extrusion equipment is preferably equipped with vacuum sizing to ensure dimensional stability during continuous extrusion.
In the preparation method provided by the invention, in the step c), the extrusion aid is removed preferably by baking; the temperature of the heat drying is preferably 150-300 ℃, more preferably 180-240 ℃, and specifically can be 180 ℃, 185 ℃, 190 ℃, 195 ℃, 200 ℃, 205 ℃, 210 ℃, 215 ℃, 220 ℃, 225 ℃, 230 ℃, 235 ℃ or 240 ℃; the heating mode of the hot drying is preferably sectional (partition) heating; the drawing speed of the hot drying is preferably 50-200 mm/min, more preferably 100-150 mm/min, and specifically can be 100mm/min, 105mm/min, 110mm/min, 115mm/min, 120mm/min, 125mm/min, 130mm/min, 135mm/min, 140mm/min, 145mm/min or 150 mm/min. In the invention, after the heat drying is finished, the mixture is preferably kept still for a period of time; wherein the temperature of the standing is preferably 15-50 ℃, more preferably 25-35 ℃, and specifically can be 15 ℃, 20 ℃, 25 ℃, 30 ℃, 35 ℃, 40 ℃, 45 ℃ or 50 ℃; the standing time is preferably 12-48 h, more preferably 18-24 h, and specifically can be 12h, 18h, 24h, 30h, 36h, 42h or 48 h.
In the preparation method provided by the invention, in the step c), the sintering temperature is above the melting point of the PTFE resin, preferably 280-400 ℃, more preferably 300-380 ℃, and specifically can be 280 ℃, 285 ℃, 290 ℃, 295 ℃, 300 ℃, 305 ℃, 310 ℃, 315 ℃, 320 ℃, 325 ℃, 330 ℃, 335 ℃, 340 ℃, 345 ℃, 350 ℃, 355 ℃, 360 ℃, 365 ℃, 370 ℃, 375 ℃, 380 ℃, 385 ℃, 390 ℃, 395 ℃ or 400 ℃; the heating mode of the sintering is preferably sectional (partition) heating; the sintering speed is preferably 50-150 mm/min, more preferably 100-130 mm/min, and specifically can be 50mm/min, 55mm/min, 60mm/min, 65mm/min, 70mm/min, 75mm/min, 80mm/min, 85mm/min, 90mm/min, 95mm/min, 100mm/min, 105mm/min, 110mm/min, 115mm/min, 120mm/min, 125mm/min, 130mm/min, 135mm/min, 140mm/min, 145mm/min or 150 mm/min.
In the preparation method provided by the present invention, in step d), the specific process of the quenching treatment preferably includes: the sintered part is subjected to a heating treatment and then rapidly cooled down. Wherein the temperature of the heat treatment is preferably 300-400 deg.C, more preferably 350-380 deg.C, and specifically 300 deg.C, 305 deg.C, 310 deg.C, 315 deg.C, 320 deg.C, 325 deg.C, 330 deg.C, 335 deg.C, 340 deg.C, 345 deg.C, 350 deg.C, 355 deg.C, 360 deg.C, 365 deg.C, 370 deg.C, 375 deg.C, 380 deg.C, 385 deg.C, 390 deg.C, 395 deg.C or 400 deg.C; the rapid cooling reduction method is preferably to place the heated workpiece in cold water, wherein the temperature of the cold water is preferably 0 to 15 ℃, more preferably 5 to 10 ℃, and specifically 5 ℃, 6 ℃, 7 ℃, 8 ℃, 9 ℃ or 10 ℃. In the present invention, the part subjected to rapid cooling down in the cold water is preferably dehydrated and dried after being taken out; the temperature of the dehydration drying is preferably 30-50 ℃, and specifically can be 30 ℃, 35 ℃, 40 ℃, 45 ℃ or 50 ℃; the time for dehydration and drying is preferably 6-18 h, more preferably 8-12 h, and specifically 6h, 8h, 10h, 12h, 14h, 16h or 18 h. In the invention, the crystallinity of the PTFE material can be reduced through quenching treatment, thereby being beneficial to the expansion molding of the PTFE pipe after subsequent crosslinking modification.
In the preparation method provided by the invention, in the step e), the crosslinking modification treatment is preferably performed by irradiation; the irradiation equipment is preferably Co-60 radioactive source irradiation equipment or a high-energy electron accelerator; the irradiation atmosphere is preferably nitrogen or argon; the irradiation dose is preferably 2-200 Mard, more preferably 5-100 Mard, and specifically can be 5Mard, 10Mard, 12Mard, 15Mard, 20Mard, 25Mard, 30Mard, 35Mard, 40Mard, 45Mard, 50Mard, 55Mard, 60Mard, 65Mard, 70Mard, 75Mard, 80Mard, 85Mard, 90Mard, 95Mard or 100 Mard; the irradiation dose rate is preferably 5-50 kGy/h, and specifically can be 5kGy/h, 10kGy/h, 15kGy/h, 20kGy/h, 25kGy/h, 30kGy/h, 35kGy/h, 40kGy/h, 45kGy/h or 50 kGy/h.
In the preparation method provided by the invention, in the step f), the heating temperature for expanding and shaping is preferably 300-450 ℃, more preferably 350-390 ℃, and specifically can be 300 ℃, 305 ℃, 310 ℃, 315 ℃, 320 ℃, 325 ℃, 330 ℃, 335 ℃, 340 ℃, 345 ℃, 350 ℃, 355 ℃, 360 ℃, 365 ℃, 370 ℃, 375 ℃, 380 ℃, 385 ℃, 390 ℃, 395 ℃, 400 ℃, 405 ℃, 410 ℃, 415 ℃, 420 ℃, 425 ℃, 430 ℃, 435 ℃, 440 ℃, 445 ℃ or 450 ℃; the expansion pressure for expansion shaping is preferably 1-10 bar, more preferably 2-5 bar, and specifically can be 1bar, 2bar, 3bar, 4bar, 5bar, 6bar, 7bar, 8bar, 9bar or 10 bar; the preferable shaping mode of the expansion shaping is water-cooling shaping, and the water temperature of the water-cooling shaping is 5-15 ℃, more preferably 8-12 ℃, and specifically can be 5 ℃, 6 ℃, 7 ℃, 8 ℃, 9 ℃, 10 ℃, 11 ℃, 12 ℃, 13 ℃, 14 ℃ or 15 ℃. In the invention, after the water-cooling shaping is finished, dehydration drying is preferably carried out; the temperature of the dehydration drying is preferably 40-80 ℃, more preferably 55-65 ℃, and specifically can be 40 ℃, 45 ℃, 50 ℃, 55 ℃, 60 ℃, 65 ℃, 70 ℃, 75 ℃ or 80 ℃; the time for dehydration and drying is preferably 12-48 h, and specifically can be 12h, 16h, 20h, 24h, 28h, 32h, 36h, 40h, 44h or 48 h.
According to the technical scheme provided by the invention, the rare earth oxide is introduced into the PTFE heat-shrinkable material, so that the damage of free radicals in the system to PTFE molecular chains is effectively reduced, and the thermal stability of the matrix is improved; and a specific preparation process is combined, particularly, crosslinking modification is carried out, so that a crosslinking structure is formed in the material, and the high temperature resistance of the material is further improved by combining the antioxidation effect of the rare earth oxide, so that the material can meet the requirement of long-time use in a high-temperature environment of 350 ℃.
For the sake of clarity, the following examples and comparative examples are given in detail below.
In the following examples and comparative examples of the present invention, in order to improve the binding force between the rare earth oxide and the matrix PTFE resin, the surface modification treatment is performed on the rare earth oxide by selecting a silane coupling agent to improve the dispersibility, and the main treatment process is as follows:
(1) 100g of CeO was added to the flask2(particle size of 30nm), adding 120mL of ethanol/water (90/10, v/v) mixed solution, mechanically stirring at 25 deg.C for 15min, rotating at 180rpm for 30min to ensure that CeO is present2Fully dispersing into the mixed solution; then adding 150mL of silane coupling agent epoxy group trimethoxy silane, heating to 50 ℃, and stirring at a high speed of 200rpm for 3 h; after the reaction is finished, centrifuging, removing supernatant, washing with ethanol to remove unreacted coupling agent, centrifuging, washing for 3 times, and vacuum drying the residue at 60 ℃ for 8h to obtain the CeO with the surface subjected to organic silicification2。
(2) 150mL of the silane coupling agent vinyltriethoxysilane was added to the flask, and 150mL of ethanol/water (90/10, v/v) was added and mixedMechanically stirring the solution at 80rpm for 30min at room temperature to hydrolyze the coupling agent; then the pH was adjusted to slightly acidic pH (pH 6.0) and 100g Y was added2O3Heating the powder (particle size of 40nm) to 70 deg.C, mechanically stirring at 100rpm for 6 hr, centrifuging after reaction, removing supernatant, washing with ethanol for 3 times, centrifuging, and vacuum drying the residue at 60 deg.C for 8 hr to obtain surface organosilication treated Y2O3。
Example 1
(1) At the temperature of 18 ℃, 100 parts by mass of PTFE resin, 18 parts by mass of petroleum ether and CeO with the surface subjected to organic silicification treatment are weighed215 parts by mass of Al2O32 parts by mass; wherein the compression ratio of the PTFE resin is 900: 1; the boiling range of the petroleum ether is 60-90 ℃; the Al is2O3Has a particle diameter of 20 nm. After the raw materials are weighed, premixing the weighed PTFE resin and petroleum ether by a mixer at the speed of 25rpm for 20min at the temperature of 17 ℃; after fully mixing, sequentially adding weighed CeO with the surface being subjected to organic silicification treatment2And Al2O3Carrying out secondary premixing at the speed of 15rpm for 5min and the temperature of 17 ℃; and then placing the mixture into a 30 ℃ thermostat for standing for 24 hours to ensure that the petroleum ether is fully immersed into resin molecules to obtain the paste-shaped master batch.
(2) Prefabricating the paste-like master batch into a tube blank through mould pressing equipment; in the prefabricating process, the uniform feeding is performed for multiple times in a segmented manner, so that the uneven wall thickness caused by uneven feeding is avoided, the pressure is controlled to be 1MPa, the compression speed is controlled to be 45mm/min, and the temperature is controlled to be 30 +/-2 ℃. And then extruding and molding the tube blank by pushing and extruding equipment, compacting the tube body by adopting a high-pressure low-speed extrusion mode, wherein the extrusion temperature is 55 ℃, the extrusion pressure is 6MPa, and the extrusion speed is 80 mm/min.
(3) Hot baking the extruded pipe to remove the extrusion aid (petroleum ether); wherein the heating temperature zone of the device for hot drying is a three-section temperature zone, the first zone is 200 ℃, the second zone is 220 ℃, the third zone is 225 ℃, and the traction speed of hot drying is 110 mm/min. And after the heat drying is finished, placing the pipe at 25 +/-3 ℃ for 18-24 h.
(4) Sintering and forming the pipe without the extrusion aid by high-temperature sintering equipment in a sectional heating mode; wherein the sintering speed is 120mm/min, and the temperature of each zone is 290 ℃, 340 ℃, 360 ℃, 375 ℃ and 320 ℃ in sequence.
(5) And (3) carrying out high-temperature treatment on the sintered and molded pipe at 370 ℃, then rapidly cooling in cold water, wherein the temperature of the cold water is 10 ℃, and then dehydrating and drying the cooled pipe at 40 ℃ for 8-12 h.
(6) Performing irradiation modification on the pipe processed in the step (5) by using a high-energy electron accelerator to realize irradiation crosslinking of PTFE; wherein the irradiation atmosphere is nitrogen, the irradiation dose is 12Mard, and the irradiation dose rate is 25 kGy/h.
(7) Expanding and forming the semi-finished pipe obtained in the step (6) through high-temperature expansion; wherein the expansion temperature is 380-385 ℃, the expansion pressure is 2-4 bar, water cooling shaping is adopted after expansion, and the water temperature is 10 +/-2 ℃; and then, drying the pipe subjected to water cooling and shaping for 24 hours at the temperature of 60 +/-5 ℃ in vacuum to obtain the heat-resistant modified PTFE heat-shrinkable tube.
Example 2
(1) Weighing 100 parts by mass of PTFE resin, 4 parts by mass of PFA resin, 20 parts by mass of Isopar G solvent oil and CeO with the surface subjected to organic silicification treatment at the temperature of 18 DEG C210 parts by mass of surface-organosilicated Y2O35 parts by mass of SiO22 parts by mass; wherein the compression ratio of the PTFE resin is 900: 1; the PFA resin has a melt index of 14-30 g/10min and a density of 2.14-2.16 g/cm3(ii) a The SiO2Has a particle diameter of 40 nm. After the raw materials are weighed, premixing the weighed PTFE resin, PFA resin and solvent oil by a mixer at the speed of 20rpm for 20min at the temperature of 17 ℃; after fully mixing, sequentially adding weighed CeO with the surface being subjected to organic silicification treatment2Surface organosilicated Y2O3And SiO2Carrying out secondary premixing at the speed of 15rpm for 5min and the temperature of 17 ℃; and then placing the mixture into a thermostat at 28 ℃ for standing for 24 hours to ensure that the solvent oil is fully immersed into resin molecules to obtain the paste-shaped master batch.
(2) Prefabricating the paste-like master batch into a tube blank through mould pressing equipment; in the prefabricating process, the uniform feeding is performed for multiple times in a segmented manner, so that the uneven wall thickness caused by uneven feeding is avoided, the pressure is controlled to be 1MPa, the compression speed is controlled to be 45mm/min, and the temperature is controlled to be 30 +/-2 ℃. And then extruding and molding the tube blank by pushing and extruding equipment, compacting the tube body by adopting a high-pressure low-speed extrusion mode, wherein the extrusion temperature is 55 ℃, the extrusion pressure is 6MPa, and the extrusion speed is 95 mm/min.
(3) Hot baking the extruded pipe to remove the extrusion aid (Isopar G solvent oil); wherein the heating temperature zone of the equipment for hot drying is a three-section temperature zone, the first zone is 190 ℃, the second zone is 205 ℃, the third zone is 210 ℃, and the traction speed of hot drying is 120 mm/min. And after the heat drying is finished, placing the pipe at 25 +/-3 ℃ for 18-24 h.
(4) Sintering and forming the pipe without the extrusion aid by high-temperature sintering equipment in a sectional heating mode; wherein the sintering speed is 125mm/min, and the temperature of each zone is 305 ℃, 345 ℃, 360 ℃, 375 ℃ and 320 ℃ in sequence.
(5) And (3) carrying out high-temperature treatment on the sintered and molded pipe at 370 ℃, then rapidly cooling in cold water, wherein the temperature of the cold water is 10 ℃, and then dehydrating and drying the cooled pipe at 40 ℃ for 8-12 h.
(6) Performing irradiation modification on the pipe processed in the step (5) by using a high-energy electron accelerator to realize irradiation crosslinking of PTFE; wherein the irradiation atmosphere is nitrogen, the irradiation dose is 15Mard, and the irradiation dose rate is 25 kGy/h.
(7) Expanding and forming the semi-finished pipe obtained in the step (6) through high-temperature expansion; wherein the expansion temperature is 380-385 ℃, the expansion pressure is 2-4 bar, water cooling shaping is adopted after expansion, and the water temperature is 10 +/-2 ℃; and then, drying the pipe subjected to water cooling and shaping for 24 hours at the temperature of 60 +/-5 ℃ in vacuum to obtain the heat-resistant modified PTFE heat-shrinkable tube.
Example 3
(1) Weighing 100 parts by mass of PTFE resin, 8 parts by mass of PFA resin, 20 parts by mass of Isopar G solvent oil and CeO with the surface subjected to organic silicification treatment at the temperature of 18 DEG C215 parts by mass of SiO22 parts by mass; wherein the compression ratio of the PTFE resin is 900: 1; the PFA resin has a melt index of 14 to 30g/10min, and a density of 2.14 to 2.16g/cm3(ii) a The SiO2Has a particle diameter of 40 nm. After the raw materials are weighed, premixing the weighed PTFE resin, PFA resin and solvent oil by a mixer at the speed of 25rpm for 20min at the temperature of 17 ℃; after fully mixing, sequentially adding weighed CeO with the surface being subjected to organic silicification treatment2And SiO2Carrying out secondary premixing at the speed of 15rpm for 5min and the temperature of 17 ℃; and then placing the mixture into a thermostat at 28 ℃ for standing for 24 hours to ensure that the solvent oil is fully immersed into resin molecules to obtain the paste-shaped master batch.
(2) Prefabricating the paste-like master batch into a tube blank through mould pressing equipment; in the prefabricating process, the uniform feeding is performed for multiple times in a segmented manner, so that the uneven wall thickness caused by uneven feeding is avoided, the pressure is controlled to be 1MPa, the compression speed is controlled to be 45mm/min, and the temperature is controlled to be 30 +/-2 ℃. And then extruding and molding the tube blank by pushing and extruding equipment, compacting the tube body by adopting a high-pressure low-speed extrusion mode, wherein the extrusion temperature is 55 ℃, the extrusion pressure is 6MPa, and the extrusion speed is 100 mm/min.
(3) Hot baking the extruded pipe to remove the extrusion aid (Isopar G solvent oil); wherein the heating temperature zone of the equipment for hot drying is a three-section temperature zone, the first zone is 190 ℃, the second zone is 205 ℃, the third zone is 210 ℃, and the traction speed of hot drying is 130 mm/min. And after the heat drying is finished, placing the pipe at 25 +/-3 ℃ for 18-24 h.
(4) Sintering and forming the pipe without the extrusion aid by high-temperature sintering equipment in a sectional heating mode; wherein the sintering speed is 130mm/min, and the temperature of each zone is 305 ℃, 345 ℃, 360 ℃, 375 ℃ and 320 ℃ in sequence.
(5) And (3) carrying out high-temperature treatment on the sintered and molded pipe at 370 ℃, then rapidly cooling in cold water, wherein the temperature of the cold water is 10 ℃, and then dehydrating and drying the cooled pipe at 40 ℃ for 8-12 h.
(6) Performing irradiation modification on the pipe processed in the step (5) by using a high-energy electron accelerator to realize irradiation crosslinking of PTFE; wherein the irradiation atmosphere is nitrogen, the irradiation dose is 15Mard, and the irradiation dose rate is 25 kGy/h.
(7) Expanding and forming the semi-finished pipe obtained in the step (6) through high-temperature expansion; wherein the expansion temperature is 380-385 ℃, the expansion pressure is 2-4 bar, water cooling shaping is adopted after expansion, and the water temperature is 10 +/-2 ℃; and then, drying the pipe subjected to water cooling and shaping for 24 hours at the temperature of 60 +/-5 ℃ in vacuum to obtain the heat-resistant modified PTFE heat-shrinkable tube.
Comparative example 1
(1) At the temperature of 18 ℃, 100 parts by mass of PTFE resin, 18 parts by mass of petroleum ether and CeO with the surface subjected to organic silicification treatment are weighed215 parts by mass of Al2O32 parts by mass; wherein the compression ratio of the PTFE resin is 900: 1; the boiling range of the petroleum ether is 60-90 ℃; the Al is2O3Has a particle diameter of 20 nm. After the raw materials are weighed, premixing the weighed PTFE resin and petroleum ether by a mixer at the speed of 25rpm for 20min at the temperature of 17 ℃; after fully mixing, sequentially adding weighed CeO with the surface being subjected to organic silicification treatment2And Al2O3Carrying out secondary premixing at the speed of 15rpm for 5min and the temperature of 17 ℃; and then placing the mixture into a 30 ℃ thermostat for standing for 24 hours to ensure that the petroleum ether is fully immersed into resin molecules to obtain the paste-shaped master batch.
(2) Prefabricating the paste-like master batch into a tube blank through mould pressing equipment; in the prefabricating process, the uniform feeding is performed for multiple times in a segmented manner, so that the uneven wall thickness caused by uneven feeding is avoided, the pressure is controlled to be 1MPa, the compression speed is controlled to be 45mm/min, and the temperature is controlled to be 30 +/-2 ℃. And then extruding and molding the tube blank by pushing and extruding equipment, compacting the tube body by adopting a high-pressure low-speed extrusion mode, wherein the extrusion temperature is 55 ℃, the extrusion pressure is 6MPa, and the extrusion speed is 80 mm/min.
(3) Hot baking the extruded pipe to remove the extrusion aid (petroleum ether); wherein the heating temperature zone of the device for hot drying is a three-section temperature zone, the first zone is 200 ℃, the second zone is 220 ℃, the third zone is 225 ℃, and the traction speed of hot drying is 110 mm/min. And after the heat drying is finished, placing the pipe at 25 +/-3 ℃ for 18-24 h.
(4) Sintering and forming the pipe without the extrusion aid by high-temperature sintering equipment in a sectional heating mode; wherein the sintering speed is 120mm/min, and the temperature of each zone is 290 ℃, 340 ℃, 360 ℃, 375 ℃ and 320 ℃ in sequence.
(5) And (3) carrying out high-temperature treatment on the sintered and molded pipe at 370 ℃, then rapidly cooling in cold water, wherein the temperature of the cold water is 10 ℃, and then dehydrating and drying the cooled pipe at 40 ℃ for 8-12 h.
(6) Expanding and forming the pipe processed in the step (5) through high-temperature expansion; wherein the expansion temperature is 380-385 ℃, the expansion pressure is 2-4 bar, water cooling shaping is adopted after expansion, and the water temperature is 10 +/-2 ℃; and then, drying the pipe subjected to water cooling and shaping for 24 hours at the temperature of 60 +/-5 ℃ in vacuum to obtain the heat-resistant modified PTFE heat-shrinkable tube.
Comparative example 2
(1) Weighing 100 parts by mass of PTFE resin, 4 parts by mass of PFA resin, 20 parts by mass of Isopar G solvent oil and SiO at the temperature of 18 DEG C22 parts by mass; wherein the compression ratio of the PTFE resin is 900: 1; the PFA resin has a melt index of 14-30 g/10min and a density of 2.14-2.16 g/cm3(ii) a The SiO2Has a particle diameter of 40 nm. After the raw materials are weighed, premixing the weighed PTFE resin, PFA resin and solvent oil by a mixer at the speed of 20rpm for 20min at the temperature of 17 ℃; after mixing thoroughly, SiO is added2Carrying out secondary premixing at the speed of 15rpm for 5min and the temperature of 17 ℃; and then placing the mixture into a thermostat at 28 ℃ for standing for 24 hours to ensure that the solvent oil is fully immersed into resin molecules to obtain the paste-shaped master batch.
(2) Prefabricating the paste-like master batch into a tube blank through mould pressing equipment; in the prefabricating process, the uniform feeding is performed for multiple times in a segmented manner, so that the uneven wall thickness caused by uneven feeding is avoided, the pressure is controlled to be 1MPa, the compression speed is controlled to be 45mm/min, and the temperature is controlled to be 30 +/-2 ℃. And then extruding and molding the tube blank by pushing and extruding equipment, compacting the tube body by adopting a high-pressure low-speed extrusion mode, wherein the extrusion temperature is 55 ℃, the extrusion pressure is 6MPa, and the extrusion speed is 95 mm/min.
(3) Hot baking the extruded pipe to remove the extrusion aid (Isopar G solvent oil); wherein the heating temperature zone of the equipment for hot drying is a three-section temperature zone, the first zone is 190 ℃, the second zone is 205 ℃, the third zone is 210 ℃, and the traction speed of hot drying is 120 mm/min. And after the heat drying is finished, placing the pipe at 25 +/-3 ℃ for 18-24 h.
(4) Sintering and forming the pipe without the extrusion aid by high-temperature sintering equipment in a sectional heating mode; wherein the sintering speed is 125mm/min, and the temperature of each zone is 305 ℃, 345 ℃, 360 ℃, 375 ℃ and 320 ℃ in sequence.
(5) And (3) carrying out high-temperature treatment on the sintered and molded pipe at 370 ℃, then rapidly cooling in cold water, wherein the temperature of the cold water is 10 ℃, and then dehydrating and drying the cooled pipe at 40 ℃ for 8-12 h.
(6) Performing irradiation modification on the pipe processed in the step (5) by using a high-energy electron accelerator to realize irradiation crosslinking of PTFE; wherein the irradiation atmosphere is nitrogen, the irradiation dose is 15Mard, and the irradiation dose rate is 25 kGy/h.
(7) Expanding and forming the semi-finished pipe obtained in the step (6) through high-temperature expansion; wherein the expansion temperature is 380-385 ℃, the expansion pressure is 2-4 bar, water cooling shaping is adopted after expansion, and the water temperature is 10 +/-2 ℃; and then, drying the pipe subjected to water cooling and shaping for 24 hours at the temperature of 60 +/-5 ℃ in vacuum to obtain the heat-resistant modified PTFE heat-shrinkable tube.
Performance detection
The heat-resistant modified PTFE heat-shrinkable tubes prepared in the above examples and comparative examples were subjected to a performance test by the specific method: the mechanical property of the heat-resistant modified PTFE heat-shrinkable tube is tested by adopting an American Instron 5982 type electronic universal material testing machine, the dielectric strength of the heat-resistant modified PTFE heat-shrinkable tube is tested by adopting a Beijing Huazhong HCDJC-50KV type dielectric strength testing instrument, and the thermal shock property and the hot air aging property of the heat-resistant modified PTFE heat-shrinkable tube are tested by adopting a GOTECHNGT-7017-NL high-temperature aging testing machine.
The tests show that the performances of examples 1-3 and comparative examples 1-2 are shown in Table 1:
TABLE 1 Performance test results of Heat-resistant modified PTFE Heat-shrinkable tubes
As can be seen from table 1, the heat-resistant modified PTFE heat-shrinkable tube prepared in comparative example 1 is not subjected to special radiation modification treatment, and a cross-linked network structure is not formed inside, and in a 400 ℃ x 4h heat shock test, since the heat shock temperature is significantly higher than the melting point of the heat-resistant modified PTFE heat-shrinkable tube, the hose is melted and deformed, and cannot maintain the original shape, and in a 350 ℃ x 168h heat air aging process, the suspended heat-resistant modified PTFE heat-shrinkable tube is severely deformed by stretching due to the action of gravity in an aging oven, and cannot be subjected to a performance test; although the heat-resistant modified PTFE heat-shrinkable tube prepared in comparative example 2 has a heat-shrinkable characteristic, since no rare earth filler is added, the tube becomes hard after being subjected to a hot air aging treatment at 350 ℃ for 168 hours, loses mechanical properties, and has no service characteristics, and in a thermal shock test at 400 ℃ for 4 hours, a suspended sample is locally deformed and extended and cannot maintain the original shape; in the embodiment, the heat-resistant modified PTFE heat-shrinkable tube prepared by introducing the rare earth oxide and performing special radiation modification treatment has no obvious change in the sample state in a 400 ℃ x 4h thermal shock test, still has high mechanical property after being subjected to 350 ℃ x 168h hot air aging treatment, and has the 350 ℃ high temperature resistance.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (10)
1. A heat-resistant modified PTFE thermal shrinkage material is prepared by raw materials through mixing, preforming, extrusion aid removing, sintering, quenching, crosslinking modification and expansion shaping; the raw materials comprise, by mass:
the rare earth oxide is one or more of cerium dioxide, cerium oxide, lanthanum oxide, zirconium dioxide and yttrium oxide.
2. The heat-resistant modified PTFE heat shrinkable material of claim 1, wherein the surface of the rare earth oxide is organosilicated.
3. The heat-resistant modified PTFE heat-shrinkable material according to claim 1, wherein the compression ratio of the PTFE resin is (400-1500): 1.
4. the heat-resistant modified PTFE heat-shrinkable material according to claim 1, wherein the PFA resin has a melt index of 14 to 70g/10 min.
5. The heat resistant modified PTFE heat shrink of claim 1, wherein the extrusion aid is one or more of toluene, petroleum ether, kerosene, and isoparaffin.
6. The heat resistant modified PTFE heat shrink of claim 1, wherein the wear resistant filler is one or more of alumina, silica, calcium oxide, silicon carbide, silicon nitride, and kaolin.
7. A preparation method of a heat-resistant modified PTFE heat-shrinkable material comprises the following steps:
a) mixing 90-100 parts by mass of PTFE resin, 0-15 parts by mass of PFA resin, 10-30 parts by mass of extrusion aid, 2-30 parts by mass of rare earth oxide and 2-10 parts by mass of wear-resistant filler to obtain paste-like master batch;
b) performing the paste-like master batch to obtain a preformed piece;
c) removing the extrusion aid in the preformed piece, and then sintering to obtain a sintered piece;
d) quenching the sintered part to obtain a quenched part;
e) carrying out cross-linking modification treatment on the quenching piece to obtain a heat-resistant modified PTFE heat-shrinkable material semi-finished product;
f) and expanding and shaping the semi-finished product of the heat-resistant modified PTFE heat-shrinkable material to obtain the heat-resistant modified PTFE heat-shrinkable material.
8. The preparation method according to claim 7, wherein in the step d), the quenching treatment comprises the following specific processes:
the sintered part is subjected to a heating treatment and then rapidly cooled down.
9. The method of claim 7, wherein in step e), the method of the crosslinking modification treatment is irradiation; the irradiation equipment is Co-60 radioactive source irradiation equipment or a high-energy electron accelerator; the irradiation atmosphere is nitrogen or argon; the irradiation dose is 5-100 Mard; the irradiation dose rate is 5-50 kGy/h.
10. A heat-resistant modified PTFE heat shrinkable tube is characterized in that the heat-resistant modified PTFE heat shrinkable tube is made of the heat-resistant modified PTFE heat shrinkable material in any one of claims 1 to 6 or the heat-resistant modified PTFE heat shrinkable material prepared by the preparation method in any one of claims 7 to 9.
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