METHOD FOR TREATING A POLYMER PART IN ORDER TO MODIFY ITS ROUGHNESS AND/OR TO FUNCTIONALISE IT

Abstract

A method for treating a polymer part comprising a step of bringing the part into contact with vapours of solvent(s), capable of at least partially solubilising the part, this contacting step being carried out under vacuum. Application of this method for modifying the roughness of the part and/or functionalising it.

Claims

1.-11. (canceled)

12. A method for treating a polymer part, which is a method for modifying the roughness of the surface of said polymer part and for functionalising said polymer part, comprising a step of bringing said part into contact with vapours of solvent(s), capable of at least partly solubilising said part, this contacting step being carried out under vacuum and comprising, before the contacting step or after the contacting step, a step of depositing over all or part of the part at least one functionalising material, the functionalising material(s) being electrically conductive polymers and/or organophosphorus polymers.

13. The treatment method according to claim 12, wherein the contacting step is performed under vacuum, such that the residual pressure during this step is 100 mbar to 200 mbar.

14. The treatment method according to claim 12, wherein the contacting step is performed at ambient temperature.

15. The treatment method according to claim 12, further comprising, after the contacting step, a step of stopping the exposure of the part to the vapours of solvent(s).

16. The treatment method according to claim 12, comprising a step of eliminating the solvent(s) present in the part obtained at the end of the contacting step.

17. The treatment method according to claim 16, wherein the eliminating step is performed by: heating the part to a temperature higher than the boiling temperature of the solvent(s); subjecting the part to a vacuum atmosphere; and/or applying a scanning loop for recondensing the solvent(s) trapped in the part.

18. The treatment method according to claim 12, wherein the polymer part comprises one or more polymers selected from polyamides, polyurethanes, polycarbonates, poly(meth)acrylates, polysulfones, polyolefins, styrenic polymers, polyethers, poly(meth)acrylics, polyoxazolines, polyacetates and mixtures thereof.

19. The treatment method according to claim 12, wherein the polymer part is based on a polyamide, such as polyamide 12.

20. The treatment method according to claim 12, wherein the solvent(s) are selected from halogenated solvents, aromatic solvents, ketonic solvents, alcoholic solvents which may be halogenated, acids and mixtures thereof.

21. The treatment method according to claim 12, wherein when the polymer part is based on polyamide 12 and the solvent is hexafluoroisopropanol.

22. The treatment method according to claim 12, wherein the solvent(s) are capable of solubilising the functionalising material(s).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0085] FIG. 1 shows two photographs of the part before treatment (left part) and the part after treatment (right part) according to the modalities of example 1 below.

[0086] FIG. 2 is a graph illustrating, for example 1, the evolution of the roughness Ra (in μm) as a function of the treatment time t (in min, 0 min, 5 min, 10 min, 20 min and 30 min respectively).

[0087] FIG. 3 is a graph illustrating, for example 2, the roughness Ra (in p.m) for substrate S1 (lower part) before and after depositing (parts a) and b) respectively) and for substrate S2 (lower part) before and after depositing (parts a) and b) respectively).

[0088] FIG. 4 is a graph illustrating, for example 2, the surface resistance S (in Ω/□) for substrates S1 and S2 before depositing (part a), for substrate S1 (lower part) after depositing (part b) and for substrate S2 (lower part) after depositing (part c).

[0089] FIG. 5 is a graph illustrating, for example 2, the surface resistance S (in Ω/□) for substrate S1 (lower part) before and after treatment (parts a) and b) respectively) and for substrate S2 (lower part) before and after treatment (parts c) and d) respectively);

[0090] FIG. 6 is a graph illustrating, for example 2, the roughness Ra (in μm) for substrate S1 for the upper part before and after treatment (parts a) and b) respectively) and for the lower part before and after treatment (parts c) and d) respectively) and for substrate S2 for the upper part before and after treatment (parts e) and f) respectively) and for the lower part before and after treatment (parts g) and h) respectively).

[0091] FIG. 7 is a graph illustrating, for example 3, the roughness Ra (in μm) for the control blanks (i.e. without a flame-retardant layer and not treated according to the method of the invention) and parts treated according to the method of the invention (parts a) and b) respectively).

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

EXAMPLE 1

[0092] This example illustrates the use of the treatment method of the invention to demonstrate the effectiveness of the latter in reducing the roughness of a part comprising polyamide 12 made by 3D printing.

[0093] The part to be treated is a disc with a thickness of 5 mm and diameter of 5 cm produced by 3D printing, this part being made from a material comprising polyamide 12 and carbon black having an initial roughness (before treatment) on its first face of 8.2 μm and an initial roughness (before treatment) on its second face (opposite the first face) of 15.4 μm.

[0094] The treatment process is carried out in a reactor-type device and, more specifically, an airtight glass reactor having an internal volume of 900 mL consisting of two parts: a container and a lid held together by silicon grease. A glass crystalliser of 5 cm diameter with a magnetic bar is disposed in the lower part of the reactor and is designed to receive the liquid solvent prior to vaporisation. The reactor is placed on a magnetic stirrer and the reactor lid is connected to a diaphragm vacuum pump.

[0095] The following steps are implemented in succession:

[0096] the solvent hexafluoroisopropanol (10 g) is placed in the crystalliser;

[0097] b) the part to be treated is placed and held in the upper part of the reactor by means of a metal support, such that it is about 5 cm above the level of the solvent placed in the crystalliser;

[0098] c) the reactor is closed by positioning the lid on the container and sealing the lid and the container by means of silicon grease;

[0099] d) the solvent placed in the crystalliser is subjected to sufficient but not too much magnetic agitation (800 rpm) to avoid any direct projections on the part;

[0100] e) the reactor is placed under vacuum so that the residual pressure is 100 mbar then isolated once this residual pressure has been reached (maintenance of static vacuum);

[0101] f) the contact time between the part and the solvent vapours is measured from the moment the value of 100 mbar is reached in the reactor;

[0102] g) after 20 minutes of treatment, the reactor is depressurised;

[0103] h) the reactor is open and the part is removed;

[0104] the removed part is then placed in a circulating air oven at a temperature of 60° C. for 5 minutes;

[0105] j) the part is then washed in a 600 mL beaker containing 500 mL water under agitation (800 rpm) for 10 minutes;

[0106] k) the part is left in the open air for a few minutes to evaporate the water; I) the part can then be manipulated.

[0107] According to a first variant, from step h), the subsequent steps may be as follows:

[0108] the part is placed in an air circulation oven at a temperature of 60° C. for 30 minutes;

[0109] j) the part can then be manipulated.

[0110] According to a second variant, from step f), the subsequent steps may be as follows:

[0111] g) after 20 minutes of treatment, the reactor is kept under vacuum (dynamic vacuum) for 20 minutes;

[0112] h) the reactor is depressurised; the reactor is opened and the part is removed;

[0113] k) the part is placed in a circulating air oven at a temperature of 60° C. for 5 minutes;

[0114] l) the part can then be manipulated.

[0115] After the treatment, the parts obtained have a roughness of 1.6 μm on the first face and a roughness of 2.4 μm on the second face.

[0116] An example of a part before treatment and a part after treatment are represented in photographic form for the part before treatment (left part) and for the part after treatment (right part) in the accompanying FIG. 1 attached. The right part shows a part with a smooth surface compared to the left part showing a part with a rough surface.

[0117] The method of treatment according to the invention is therefore extremely effective in reducing the roughness of a polymer part.

[0118] The roughness was also measured as a function of the treatment time (0 min, 5 min, 10 min, 20 min and 30 min), the other operating parameters being those already mentioned above. The results are shown in the accompanying FIG. 2 attached, which is a graph illustrating the evolution of the roughness Ra (in μm) as a function of the treatment time t (0 min, 5 min, 10 min, 20 min and 30 min respectively). For each treatment period the left bar corresponds to the roughness of the first face and the right bar corresponds to the roughness of the second face.

[0119] It was found that the longer the treatment time the lower the roughness of the surface obtained. It is thus possible to adjust the treatment time according to the desired roughness.

EXAMPLE 2

[0120] This example illustrates the implementation of the treatment method of the invention to demonstrate its effectiveness in encapsulating a conductive PEDOT:PSS layer in a polymer part based on polyamide 12.

[0121] The parts to be treated in this example consist of two polyamide 12 substrates having a rectangular form and the following dimensions: 30 mm*50 mm*5 mm (denoted S1 and S2 respectively).

[0122] Each of the substrates S1 and S2 is coated on the lower part of one face by spraying a layer of PEDOT:PSS (the upper part being left blank for reference), the quantity of polymer deposited being less on substrate S1 than on substrate S2.

[0123] Once the layer of polymer has been deposited, a secondary doping step in ethylene glycol was performed for 30 minutes to improve the electronic conductivity. Lastly, the two substrates were washed in ethanol before being dried at 120° C. for 30 minutes.

[0124] The roughness and surface resistance measurements were carried out by using a mechanical profilometer and a 4-point probe respectively, the results being shown in:

[0125] FIG. 3, which is a graph illustrating the roughness Ra (in μm) for substrate S1 (lower part) before and after depositing (parts a) and b) respectively) and for the substrate S2 (lower part) before and after depositing (parts a) and b) respectively) but before the implementation of the treatment;

[0126] FIG. 4, which is a graph illustrating the surface resistance S (in Ω/□) for substrates S1 and S2 before depositing (part a), for substrate S1 (lower part) after depositing (part b) and for substrate S2 (lower part) after depositing (part c) but before treatment.

[0127] The Ra measurements are between 8 and 11 p.m. The areas without PEDOT:PSS have high resistance (close to 10.sup.11 Ω/□). The resistances obtained with the S1 and S2 substrates (lower parts) are between 10.sup.3Ω/□ and 10.sup.2 Ω/□ respectively reflecting an electronically conductive layer.

[0128] The two substrates S1 and S2 are then subjected to a treatment according to the invention similar to the one described in example 1 below, except that the duration of exposure to the vapours is limited here to 10 minutes.

[0129] At the end of this treatment, the measurements of surface resistance S and roughness Ra were repeated, the results being shown respectively in:

[0130] FIG. 5, which is a graph illustrating the surface resistance S (in Ω/□) for substrate S1 (lower part) before and after treatment (parts a) and b) respectively) and for substrate S2 (lower part) before and after treatment (parts c) and d) respectively);

[0131] FIG. 6, which is a graph illustrating the roughness Ra (in μm) of the substrate S1 for the upper part before and after treatment (parts a) and b) respectively) and for the lower part before and after treatment (parts c) and d) respectively) and for substrate S2 for the upper part before and after treatment (parts e) and f) respectively) and for the lower part before and after treatment (parts g) and h) respectively).

[0132] The main conclusions are as follows:

[0133] the treatment according to the invention reduces the roughness of the lower part and the upper part of each of the substrates;

[0134] the surface resistances remain below 10.sup.5 Ω/□ whether treated or not, which attests to the maintenance of electronic conductivity properties;

[0135] the surface resistance seems to increase slightly after the treatment according to the invention, which may attest to the fact that the polyamide 12 after solubilisation has reprecipitated on the surface of the conductor, which given the insulating nature of polyamide 12, induces an increase in surface resistance.

[0136] Regarding the roughness values achieved after the treatment, a treatment of 10 minutes results in an effectiveness of 75-80% for the layer of PA 12 alone (without PEDOT), whereas it is 55 to 70% for the layer of PA 12+PEDOT.

[0137] The effectiveness of the roughness is linked to the thickness of the layer of PEDOT (less effective for substrate S2 compared to substrate S1) (due to the lower permeation kinetics of the hexafluoroisopropanol vapour through the layer of PEDOT).

[0138] The chemical treatment of the present invention thus makes it possible to encapsulate the functional materials (electronic conductors in this case) while reducing the surface roughness.

EXAMPLE 3

[0139] This example illustrates the implementation of the treatment method of the invention to demonstrate its effectiveness in functionalising polymer parts based on polyamide 12 with a view to improving their flame retardant properties while decreasing the roughness of the parts treated in this way.

[0140] The parts to be treated in this example are parallelepiped parts made of polyamide 12 and having the following dimensions: 127 mm*12.7 mm*5 mm.

[0141] On one of the faces of each of the parts a solution is sprayed comprising an organophosphorus monomer (bis[2-(methacryloyloxy)ethyl]phosphate), azobisisobutyronitrile (AiBN) (which acts as a radical initiator) and acetone.

[0142] Once the solution has been deposited, a heat treatment is carried out at 100° C. for a period of 12 hours, which allows the solution to polymerise on the surface of the parts and thus form a dense and stable layer on the surface of the parts.

[0143] The parts are then subjected to a treatment according to the invention similar to the one described in example 1 below, except that the duration of exposure to vapours is limited here to 10 minutes.

[0144] After treatment, the roughness Ra is measured with a mechanical profilometer, the results being shown in FIG. 7, which illustrates the roughness Ra (in μm) for the control blanks (i.e. parts without a flame retardant layer and not treated according to the method of the invention) and parts treated according to the method of the invention (parties a) and b) respectively).

[0145] Thus, it was found that the treatment applied to previously treated fire-retardant parts reduced the Ra roughness of the parts by more than 60%. This results in roughnesses in the order of 2 μm.

[0146] The evaluation of the flame retardant behaviour of the treated parts is also performed according to standard UL94V0. In this case, a flame is applied to the vertically placed parts for 10 seconds. The residual combustion and afterglow time and the flow of flaming droplets from the sample are then assessed. Two ignitions are applied for this test. Five parts per condition (control blanks and parts treated according to this example) were tested.

[0147] While the blanks have flows of flaming droplets with each ignition, no combustion, incandescence, or flow of flaming droplets were observed for the fire-retardant and chemically polished treated parts (effectiveness of the fire-retardant property proven).

[0148] Furthermore, from the effect of the flammability test the blanks show a faded effect, whereas for the treated parts, the formation of a crust from the effect of the flame makes it possible to avoid any ignition or ignited flows (which attests to the effectiveness of the flame-retardant properties).

[0149] In conclusion, the treatment according to the invention carried out on PA 12 parts, previously treated with fire retardant by a deposit of polymer materials based on organophosphorus compounds, makes it possible to considerably reduce the surface roughness of the parts while retaining very good fire resistance.

[0150] The treatment according to the invention thus makes it possible to improve the adhesion of the functional materials (fireproof in this case) while reducing the surface roughness.