Modified plastic surfaces with perfluoropolymers and method for producing same

Abstract

Modified plastic surfaces with perfluoropolymers are provided, whereby plastic surfaces that are intended for use under tribological conditions have substantially improved assembly properties and/or sliding friction properties and exhibit a very low degree of wear. Accordingly, modified plastic surfaces with perfluoropolymers are provided in which modified perfluoropolymer (micro)powders are present at the surface of plastics that comprise olefinically unsaturated double bonds at least at the surface such that the modified perfluoropolymer (micro)powders are chemically covalently bonded via a radical coupling of the olefinically unsaturated double bonds with perfluoropolymer (peroxy) radicals of the modified perfluoropolymer (micro)powders after a reactive conversion under mechanical stress at room temperature.

Claims

1. Modified plastic surfaces with perfluoropolymers in which modified perfluoropolymer (micro)powders are present at the surface of plastics that comprise olefinically unsaturated double bonds at least at the surface such that the modified perfluoropolymer (micro)powders are chemically covalently bonded via a radical coupling of the olefinically unsaturated double bonds with perfluoropolymer (peroxy) radicals of the modified perfluoropolymer (micro)powders after a reactive conversion under mechanical stress at room temperature.

2. The modified plastic surfaces according to claim 1 in which molded parts and/or component parts composed of polymers having groups with olefinically unsaturated double bonds in the side chain and/or in the main chain at the surface are present as plastics.

3. The modified plastic surfaces according to claim 2 in which elastomers/rubber or rubber prior to vulcanization or thermoplastic elastomers or thermoplastics or thermosets are present as polymers with olefinically unsaturated double bonds, each at the surface.

4. The modified plastic surfaces according to claim 2 in which SBR (styrene-butadiene rubber), NBR (nitrile rubber), HNBR (hydrogenated nitrile rubber), XNBR (carboxylated nitrile rubber), EPDM (ethylene propylene diene rubber), BR (polybutadiene rubber), IR (isoprene rubber), NR (natural rubber), SBS (styrene-butadiene-styrene copolymer), SEBS (styrene-ethylene-butylene-styrene copolymer), SEPS (styrene-ethylene-propylene-styrene copolymer), SEEPS (styrene-ethylene-ethylene-propylene-styrene copolymer), MBS (methacrylate-butadiene-styrene copolymer) and mixtures thereof, ABS (acrylonitrile butadiene-styrene copolymer) and blends of ABS with PA (polyamide) or ABS and PC (polycarbonate), BMC (bulk molding compound) or SMC (sheet molding compound) on a UP (unsaturated polyester) resin base or vinyl ester resin base as a pre-preg and/or cured material that still has olefinically unsaturated double bonds at the surface, or on an epoxy resin base as a pre-preg and/or cured material, wherein after subsequent modification the surface has groups with olefinically unsaturated double bonds, are present as polymers.

5. The modified plastic surfaces according to claim 1 in which modified perfluoropolymer (micro)powders are present which have been modified by means of radiation-chemical and/or plasma-chemical treatment.

6. The modified plastic surfaces according to claim 1 in which modified PTFE and/or PFA and/or FEP are present as modified perfluoropolymer (micro)powders.

7. The modified plastic surfaces according to claim 1 in which the surface of the plastics is at least partially or locally covered and covalently coupled with modified perfluoropolymer (micro)powder.

8. The modified plastic surfaces according to claim 1 in which modified perfluoropolymer (micro)powders with particle sizes in the range from 60 nm to 500 μm are present.

9. A method for producing modified plastic surfaces with perfluoropolymer (micro)powders, in which method modified perfluoropolymer (micro)powders with a perfluoropolymer (peroxy) radical concentration of >5.Math.10.sup.16 spin/g.sub.perflurompolymer are applied at room temperature to a solid surface of plastics that comprise olefinically unsaturated double bonds at least at the surface and a reactive conversion is carried out under mechanical stress during and/or after the application of the modified perfluoropolymer (micro)powders, wherein a subsequent annealing of the plastic surface with the modified perfluoropolymer (micro)powders is excluded.

10. The method according to claim 9 in which radiation chemical- and/or plasma chemical-modified PTFE (micro)powder and/or PFA (micro)powder and/or FEP (micro)powder are used as modified perfluoropolymer (micro)powders.

11. The method according to claim 9 in which the perfluoropolymer (micro)powders have been modified with radiation dose of >50 kGy and have a concentration of >5.Math.10.sup.16 spin/g.sub.perflurompolymer of perfluoropolymer (peroxy) radicals.

12. The method according to claim 9 in which the perfluoropolymer (micro)powders have been radiation-chemically modified in the presence of reactants.

13. The method according to claim 9 in which molded parts and/or component parts composed of polymers having groups with olefinically unsaturated double bonds in the side chain and/or in the main chain at least at the surface are used as plastics and modified.

14. The method according to claim 13 in which elastomers/rubber or rubber prior to vulcanization or thermoplastic elastomers or thermoplastics or thermosets are used as polymers with olefinically unsaturated double bonds, each at the surface.

15. The method according to claim 13 in which SBR (styrene-butadiene rubber), NBR (nitrile rubber), HNBR (hydrogenated nitrile rubber), XNBR (carboxylated nitrile rubber), EPDM (ethylene propylene diene rubber), BR (polybutadiene rubber), IR (isoprene rubber), NR (natural rubber), SBS (styrene-butadiene-styrene copolymer), SEBS (styrene-ethylene-butylene-styrene copolymer), SEPS (styrene-ethylene-propylene-styrene copolymer), SEEPS (styrene-ethylene-ethylene-propylene-styrene copolymer), MBS (methacrylate-butadiene-styrene copolymer) and mixtures thereof, ABS (acrylonitrile butadiene-styrene copolymer) and blends of ABS with PA (polyamide) or ABS and PC (polycarbonate), BMC (bulk molding compound) or SMC (sheet molding compound) on a UP (unsaturated polyester) resin base or vinyl ester resin base as a pre-preg and/or cured material that still has olefinically unsaturated double bonds at the surface, or on an epoxy resin base as a pre-preg and/or cured material, wherein after subsequent modification the surface has groups with olefinically unsaturated double bonds, are used as polymers.

16. The method according to claim 9 in which the modified perfluoropolymer (micro)powders are applied to the plastic surface at room temperature.

17. The method according to claim 9 in which modified perfluoropolymer (micro)powders are applied to a solid plastic surface which has a temperature of up to 200° C.

18. The method according to claim 9 in which the reactive conversion is achieved under mechanical stress via compressive stress without or with carrier bodies composed of metal and/or ceramic and/or plastic and/or via stressing by accelerated carrier bodies composed of metal and/or ceramic and/or plastic, wherein the mechanical stress is applied during and/or after the application of the radiation-chemically and/or plasma-chemically modified perfluoropolymer (micro)powders to the solid plastic surface.

19. The method according to claim 9 in which the application of the modified perfluoropolymer (micro)powders is carried out before the reactive conversion under mechanical stress and the modified perfluoropolymer (micro)powder is positioned on the solid plastic surface via electrostatic adsorption.

Description

COMPARATIVE EXAMPLE 1

(1) On a 60 m×60 mm steel plate, a vulcanized NBR plate with dimensions of 50 m×50 mm and a thickness of 2 mm is positioned and covered with a thin layer of PFA powder (PFA 6502 TAZ, 3M/Dyneon, electron-irradiated with 500 kGy) with a perfluoroalkyl (peroxy) radical concentration of >10.sup.20 spin/g.sub.PFA. A 60 m×60 mm steel plate is placed thereon. On this steel plate, another vulcanized NBR plate with dimensions of 50 m×50 mm and a thickness of 2 mm is placed, whereon another 60 m×60 mm steel plate is placed. This stack is positioned in a press with a punch diameter of 120 mm and pressurized with 100 kN at room temperature. After 10 minutes, the pressure is released and the stack is removed. The NBR plate that was covered with PFA powder is removed and thoroughly washed with ethanol, with a light brushing thereby taking place using a paintbrush. After the drying of the plate, the surface feels like that of the starting material. Water does not drip off the surface, but rather flows away slowly as in the case of the starting material.

(2) No PFA is visible across the entire area in the REM image, and no fluorine is visible in the EDX image. Except for faint traces close to the limit of detection, no fluorine is detectable in the EDX spectrum, which means that no surface modification took place under pressure only.

(3) Tribological analyses in the block/ring test showed that stick-slip phenomena occur, and that no differences from the starting material emerge in terms of the sliding friction properties.

COMPARATIVE EXAMPLE 2

(4) On a 60 m×60 mm steel plate, a vulcanized NBR plate with dimensions of 50 m×50 mm and a thickness of 2 mm is positioned and covered with a thin layer of PFA powder (PFA 6502 TAZ, 3M/Dyneon, electron-irradiated with 500 kGy) with a perfluoroalkyl (peroxy) radical concentration of >10.sup.20 spin/g.sub.PFA. A 60 m×60 mm steel plate is placed thereon. On this steel plate, another vulcanized NBR plate with dimensions of 50 m×50 mm and a thickness of 2 mm is placed, whereon another 60 m×60 mm steel plate is placed. This stack is positioned in a press with a punch diameter of 120 mm and pressurized with 100 kN at a temperature of 80° C. After 10 minutes, the pressure is released and the stack is removed. The NBR plate that was covered with PFA powder is removed and thoroughly washed with ethanol, with a light brushing thereby taking place using a paintbrush. After the drying of the plate, the surface feels like that of the starting material.

(5) The results are analogous to Comparative Example 1, which means that no surface modification took place under pressure and temperature only, nor did any differences from the starting material emerge in terms of the sliding friction properties.

COMPARATIVE EXAMPLE 3

(6) On a 60 m×60 mm steel plate, a vulcanized NBR plate with dimensions of 50 m×50 mm and a thickness of 2 mm is positioned and covered with a thin layer of PTFE powder (TF9205, 3M/Dyneon, not irradiated, thermomechanically degraded, without radicals). A 60 m×60 mm steel plate is placed thereon. On this steel plate, another vulcanized NBR plate with dimensions of 50 m×50 mm and a thickness of 2 mm is placed, whereon another 60 m×60 mm steel plate is placed. This stack is positioned in a press with a punch diameter of 120 mm and pressurized with 100 kN at a temperature of 120° C. A vibrator is then positioned along the middle plate, with which vibrator this plate is induced to vibrate. After 10 minutes, the test is ended, the pressure is released, and the stack is removed. The NBR plate that was covered with TF9205 powder is removed and thoroughly washed with ethanol, with a light brushing thereby taking place using a paintbrush. After the drying of the plate, the surface feels like that of the starting material.

(7) The results are analogous to Comparative Example 1, which means that no surface modification took place with radical-free perfluoropolymer powder under pressure, temperature and shearing, nor did any differences from the starting material emerge in terms of the sliding friction properties.

EXAMPLE 1

(8) Analogously to Comparative Example 1, the stack is prepared, positioned in the press and pressurized at room temperature under the same conditions. A vibrator is then positioned along the middle plate, with which vibrator this plate is induced to vibrate. After 10 minutes, the pressure is released and the stack is removed. The NBR plate that was covered with PFA powder (PFA 6502 TAZ, 3M/Dyneon, electron-irradiated with 500 kGy) with a perfluoroalkyl (peroxy) radical concentration of >10.sup.20 spin/g.sub.PFA is removed and thoroughly washed with ethanol, with a light brushing thereby taking place using a paintbrush. After the drying of the plate, a glossy surface is visible which feels very smooth and on which the water drips off.

(9) PFA particles are visible across the entire area in the REM image, and in the EDX image fluorine can be seen distributed very intensively and uniformly on the NBR surface. In the EDX spectrum, a marked fluorine peak is detectable, which means that a surface modification was achieved under pressure and vibration (shearing), even without temperature.

(10) Tribological analyses in the block/ring test showed that no stick-slip phenomena emerge with these surface-modified NBR materials. Sliding friction coefficients between 0.20 and 0.23 were measured, which means that these surface-modified NBR materials differ in terms of the sliding friction properties compared to the unmodified starting material.

EXAMPLE 2

(11) On a 100 m×100 mm steel plate, a vulcanized NR plate with dimensions of 50 m×50 mm and a thickness of 2 mm is positioned and covered by and screwed together with a 100 mm×100 mm steel plate which at the center has a circular hole as a window with a diameter of 20 mm, such that the NR is only visible in the opening. The 2 steel plates with the NR sample are fixed on a hot stage and heated to 100° C. On the visible/accessible NR in the window, PTFE micropowder (Zonyl MP 1200, DuPont, previously radiation-modified by the manufacturer, spin number of 1.37×10.sup.18 spin/g.sub.PTFE) is then added and rubbed in on the NR surface in a circular motion using a stiff brush. After 2 minutes, the test is stopped and the NR plate is removed. The NR plate that was locally covered with PTFE powder, is suctioned and thoroughly washed with ethanol, with a light brushing thereby taking place using a paintbrush. After the drying of the plate, the locally treated surface is visible as a glossy area which feels very smooth and from which the water drips off in contrast to the untreated border zones.

(12) PTFE particles are visible across the entire area in the REM image, and in the EDX image fluorine can be seen distributed intensively and uniformly on the NR surface. In the EDX spectrum of the locally treated surface, a marked fluorine peak is detectable, which means that a surface modification was achieved under pressure, temperature, and friction (shearing). Tribological analyses in the block/ring test showed that no stick-slip phenomena emerge with these surface-modified NR materials. Sliding friction coefficients between 0.22 and 0.25 were measured, which means that these surface-modified NR materials differ in terms of the sliding friction properties compared to the unmodified starting material.

EXAMPLE 3

(13) On a 100 m×100 mm steel plate, a vulcanized SBR plate with dimensions of 50 m×50 mm and a thickness of 2 mm is positioned and covered by and screwed together with a 100 mm×100 mm steel plate which at the center has a circular hole as a window with a diameter of 20 mm, such that the SBR is only visible in the opening. The 2 steel plates with the SBR sample are fixed on a hot stage and heated to 50° C. On the visible/accessible SBR in the window, PTFE micropowder (Algoflon L620, Solvay, previously radiation-modified by the manufacturer, spin number of 6.5×10.sup.19 spin/g.sub.PTFE) and steel balls with a diameter of 0.5 mm are then added. With a circular plastic punch (PA66/30GF), the steel balls are moved with the PTFE in a rolling manner on the surface under pressure and with a circular motion, such that the PTFE micropowder is treated on the accessible surface of the SBR. After approx. 5 minutes, the test is stopped, the steel balls are removed using a magnet, and the excess PTFE is suctioned away. The SBR plate is removed, and the site locally treated with PTFE powder is thoroughly washed with ethanol, with a light brushing thereby taking place using a paintbrush. After the drying of the plate, the locally treated surface is visible as a glossy area which feels very smooth and on which the water drips off in contrast to the untreated border zones.

(14) PTFE particles are visible across the entire area in the REM image, and in the EDX image fluorine can be seen distributed intensively and uniformly on the SBR surface. In the EDX spectrum of the locally treated surface, a marked fluorine peak is detectable, which means that a surface modification was achieved under pressure, temperature, and friction (shearing).

(15) Tribological analyses in the block/ring test showed that no stick-slip phenomena emerge with these surface-modified SBR materials. Sliding friction coefficients between 0.22 and 0.24 were measured, which means that these surface-modified SBR materials differ in terms of the sliding friction properties compared to the unmodified starting material.

EXAMPLE 4

(16) An ABS plate with dimensions of 50 m×50 mm and a thickness of 2 mm is covered by and screwed together with a 50 m×50 mm steel plate which at the center has a circular hole as a window with a diameter of 20 mm, such that the ABS is only visible in the opening. On the visible/accessible ABS in the window, PFA micropowder (PFA 6502 TAZ, 3M/Dyneon, electron-irradiated with 500 kGy) with a perfluoroalkyl (peroxy) radical concentration of >10.sup.20 spin/gpFA, which powder was previously processed with PAO (polyalphaolefin oil) into paste, is then applied as a paste in a thin layer. Using a sonotrode, the PFA paste on the ABS surface is subjected to an ultrasound treatment with short pulses under light pressure and with a circular motion. After approx. 2 minutes, the test is stopped. The ABS plate that was locally treated with PFA powder paste is first thoroughly washed with naphtha and then with ethanol, with a light brushing thereby taking place using a paintbrush. After the drying of the plate, the locally treated surface is visible as a glossy area which feels smooth and on which the water drips off in contrast to the untreated ABS border zones.

(17) PFA particles are visible across the entire area in the REM image, and in the EDX image fluorine can be seen distributed intensively and uniformly on the locally treated ABS surface. In the EDX spectrum of the locally treated surface, a marked fluorine peak is detectable, which means that a surface modification was achieved with the ultrasound treatment.

(18) Tribological analyses in the block/ring test showed that no stick-slip phenomena emerge with these surface-modified ABS materials. Sliding friction coefficients between 0.18 and 0.22 and wear coefficients of 1.8 to 6.1×10.sup.−6 mm.sup.3/Nm were measured, which means that these surface-modified ABS materials differ in terms of the sliding friction and wear properties compared to the unmodified ABS starting material. When unmodified, ABS materials as amorphous materials are not suitable as tribomaterial with regard to sliding friction and wear.

EXAMPLE 5

(19) A partially cured SMC plate on a UP resin base with dimensions of 100 m×100 mm and a thickness of 2 mm is covered by and screwed together with a 100 m×100 mm steel plate which at the center has a rectangular 20 m×50 mm gap as a window, such that the SMC is only visible in the opening. On the visible/accessible SMC in the window, PFA micropowder (PFA 6502 TAZ, 3M/Dyneon, electron-irradiated with 500 kGy) with a perfluoroalkyl (peroxy) radical concentration of >10.sup.20 spin/g.sub.PFA, which powder was previously wetted with ethanol and processed with water into paste, is then applied as a paste in a thin layer. Using a sonotrode, the PFA paste on the SMC surface is subjected to an ultrasound treatment under light pressure and with a circular motion. After approx. 1 minute, the test is stopped. The SMC plate that was locally treated with PFA is rinsed with an aqueous surfactant solution. After the drying, the plate undergoes final curing in a mold. Afterwards, the plate is thoroughly washed with ethanol, with a light brushing thereby taking place using a paintbrush. After the drying of the plate, the locally treated surface is visible as a glossy area which feels very smooth and on which the water drips off in contrast to the untreated border zones.

(20) PFA particles are visible across the entire area in the REM image, and in the EDX image fluorine can be seen distributed intensively and uniformly on the treated SMC surface. In the EDX spectrum of the locally treated surface, a marked fluorine peak is detectable, which means that a surface modification was achieved with the ultrasound treatment.

(21) Tribological analyses in the block/ring test showed that no stick-slip phenomena emerge with these surface-modified SMC materials. Sliding friction coefficients between 0.18 and 0.21 and wear coefficients of 0.48 to 1.51×10.sup.−7 mm.sup.3/Nm were measured, which means that these surface-modified SMC materials differ in terms of the sliding friction properties compared to the unmodified starting material.