WO2011004053A1

WO2011004053A1 - Nanocomposite inorganic fullerene and polyamide materials with enhanced thermal, tribological, and mechanical-dynamic properties, and use thereof as coatings

Info

Publication number: WO2011004053A1
Application number: PCT/ES2010/070480
Authority: WO
Inventors: Mohammed Naffakh Cherradi-Hadi; María de los Ángeles GÓMEZ RODRÍGUEZ; Ignacio JIMÉNEZ GUERRERO
Original assignee: Consejo Superior De Investigaciones Científicas (Csic)
Priority date: 2009-07-09
Filing date: 2010-07-09
Publication date: 2011-01-13
Also published as: ES2352628B1; ES2352628A1

Abstract

The invention relates to a polymer composition which includes a polyamide matrix containing nanoparticles of inorganic fullerenes, wherein said nanoparticles have at least two small dimensions with a size of less than 200 nm. Further, the invention relates to the method for obtaining said composition and to the use thereof in the production of plastic parts or in coating materials.

Description

NANOCOMPUEST MATERIALS OF POLYAMIDS AND FULERENS

INORGANIC WITH THERMAL, TRIBOLOGICAL PROPERTIES AND

IMPROVED MECHANICAL-DYNAMICS AND ITS APPLICATION AS

COATINGS

The present invention falls within the field of the plastics industry and, in particular, in the sector of polymeric nanocomposites dedicated to obtaining lighter materials and higher thermal, mechanical and tribological performance.

STATE OF THE TECHNIQUE

The nanocomposite materials or nanocomposites, are those formed by a matrix material to which a second component is added in the form of particles of nanometric dimension that improve the properties of said matrix. In general, the use of mineral loads of the type talc, mica, calcium carbonate, etc., to reinforce a polymer makes it possible to significantly improve mechanical properties such as stiffness, but reduces toughness, transparency and surface quality. , while increasing the weight and viscosity of the melt. On the contrary, the reduction of particle size (on a nanometric scale), as well as the percentage of charge incorporated (less than 10%), produces tangible results by increasing the properties of the nanocomposite, such as stiffness, fire resistance , The thermal and dimensional stability, and the barrier properties, without sacrificing other properties such as weight, toughness and transparency. In this sense, ready-to-use nanocomposite products can be found on the market, especially formulations based on Nylon and laminar particles. Since in 1988 the group of "Toyota's Central Research and Development Laboratories" developed the first polymer nanocomposites with clays, where presented the synthesis of nanocomposites of nylon-6 / montmorillonite (cf. US 4,739,007), in which, with small amounts of the inorganic compound, a substantial improvement of the properties was obtained, other suppliers such as Bayer (Durethan KU2-2601, Nylon 6), Honeywell Polymer (Aegis ™ NC, Nylon 6), Foster Corporation (SET ™ nanocomposite, Nylon 12), Natualnano (Nylon / halloisite-type clay nanotubes) and PoIyOne (Nylon 6 / nano-clays by in-situ polymerization) offer a wide range of nanocomposites based on Nylon according to the property (s) that is intended to be enhanced. As for nanocomposites based on carbon nanotubes, the majority of cars produced in the USA. UU. since the end of the 90s they contain carbon nanotubes mixed with the Nylon to protect against static electricity in the fuel system. In this regard, some general articles have been published in the form of reviews that refer to polymeric nanocomposites (cf. Moniruzzaman, M .; Winey, KI Macromolecules 39, 5194-5205 (2006); Pavlidou, S .; Papaspyrides, CD Proq Polym. Sci. 33, 1119-1198 (2008)). However, progress in this type of materials is being limited due to the fundamental role of the stages of modification of the nano-loads, which have a significant impact on the cost of the finished product.

In addition, other products are known, such as those of the Quadrant EPP supplier based on Nylon 6 and the sheets or laminar particles of M0S2. The product is called Nylatron ^® and offers a wide range of engineering applications such as gear wheels, bearings, gears and anti-wear pads. Also, Nylatron ^® is used in numerous sectors, such as in the maritime sector, mining, railways, steel foundries, etc. On the other hand, previous studies on the incorporation of WS2 inorganic fulerene nanoparticles in thermoplastic polymers such as Isotactic polypropylene (iPP) and phenylene polysulfide (PPS), have shown the influence of inorganic fulerene nanoparticles on the thermal and mechanical properties of the resulting material (cf. Naffakh, M., et al., J. Polvm. Sci Part B: Polvm. Phvs. 45, 2309-2321 (2007); Naffakh, M., et al., J. Phys. Chem. B. 113, 7107-7115 (2009))

Other studies on polymer matrices of epoxy and polyether ether ketone (PEEK) have shown the improvement of the tribological properties (cf. Rapoport, L. et al., Adv. Enq. Mat. 6, 44-48 (2004); Hou, X., et al., Surf. Coat. TechnoL 202, 2287 (2008)).

There is therefore a need for an alternative in the search for materials that could be used to produce new advanced polymer nanocomposites by simple methods with low cost.

DESCRIPTION OF THE INVENTION

The present invention relates to a new type of polymeric nanocomposites based on polyamides and inorganic fulerene (Fl) nanoparticles, obtaining the most spectacular results in terms of improving physical properties in general for materials of this type. Particularly the inventors have observed a significant improvement in the mechanical, thermal and tribological properties of polyamides by adding nanoparticles of inorganic fulerenes.

The use of inorganic fulerenes as nanoparticles for obtaining the nanocomposites, presents advantages with respect to the other type of particles of fulerenes already used in the state of the art, such as the improvement of the intrinsic properties of the fulerene type particles, by not having high anisotropy problems such as chalcogenide laminar particles, and also because the mixing and dispersion of almost spherical particles is much better than that of the laminar particles.

Therefore, a first aspect of the invention refers to a polymeric composite material (from now on composition of the invention) formed by a polymer of the family of polyamides, which acts as a matrix material, containing inorganic fulerene nanoparticles, where said nanoparticles have at least two reduced dimensions of a nanometric size or less than 200nm.

A preferred embodiment of the composition of the invention comprises a proportion of nanoparticles of less than 10% by weight with respect to the total composition. More preferably, it is in a proportion less than 5% by weight and even more preferably it is in a proportion between 1 and 2% by weight.

The nanocomposite materials or nanocomposites, are those formed by a matrix material to which a second component in the form of particles of nanometric dimension is added. In the present invention, the polymer that acts as a matrix belongs to the family of polyamides, characterized by containing amide chemical groups (-CONH-).

These polyamides can be found in nature, such as wool or silk, and also be synthetic and can be selected from among the different types of nylon known to any person skilled in the art, such as but not limited to nylon-6, nylon-11 or nylon-66 and aromatic aramides or polyamides, among which are, for example, but not limited to, kevlar® (polyparaphenylene terephthalamide) or nomex®. The nanoparticles that are incorporated to form the compound of the invention are inorganic fulerenos, being understood as "fulerenes" the structures formed by curved basal planes that close on themselves, and by "inorganic fulerenes" those fulerenes whose composition does not enter the element carbon, and that in normal conditions it presents a laminar structure of stacking of basal planes, but that in special conditions of synthesis it gives rise to curved basal planes that close on themselves. The fulerene structures can give rise to closed spherical, ellipsoidal or nanotube structures. The inorganic fulerene nanoparticles must have at least two reduced dimensions of nanometric size, having the shape of nanotubes when they have two reduced dimensions and an extended one, form of nanoelipsoids when the three dimensions are reduced but not equal, and of nanospheres when the three dimensions They are reduced and equal to each other.

With respect to the chemical nature of inorganic fulerene, they can be chalcogenides, that is, binary compounds of the chalcogen elements (O, S, Se, Te) in oxidation state (-2) and laminar structure, or laminar halides, that is, binary compounds of the halogens (F, Cl, Br, I) in oxidation state (-1). In general, but without pretending to be a limitation, the most common compounds in the form of inorganic fulerenes can be sulphides or selenides of transition elements (elements of groups 3 to 12 of the periodic table), such as for example WS ₂ , MoS ₂ , NbS ₂ , TaS ₂ or VS ₂ and their MoSe ₂ or WSe ₂ selenides.

The compound of the invention is obtained by physically mixing its components at high temperatures, in a single stage, without the need to add modifiers (or compatibilizers) or surfactants. This invention represents an alternative contribution to the development of new polyamide compounds by an environmental method. compatible with the industrial processes that are used to prepare plastics, such as extrusion or injection. The addition of modifiers or surfactants can be carried out in a simple way in the mixing chamber, although, as described above, none of these extra additives is necessary, however, their addition can reduce processing times.

Therefore, another aspect of the present invention relates to a process for obtaining the composition of the invention, characterized by the mixing, preferably mechanical, at high temperature of a molten polyamide and the inorganic fulerene nanoparticles. By "high temperature" is meant in the present invention a temperature of about 4O ⁰ C above the melting point of the polyamide used. Therefore, depending on said polyamide this temperature could vary. In an estimated range the temperature could vary between 200 and 300 ⁰ C for the nylon, and from 300 ° C-500 ° C for the aramid.

The compounds obtained with the process of this invention can be used to obtain engineering articles by conventional methods, such as: forming, extrusion, compression molding or injection. Examples of these articles may be filaments, fibers, films, rods and tubes or any other geometry or form factor applicable to the polyamide sector.

Therefore, another aspect of the invention refers to the use of the composition of the invention, for the manufacture of any type of articles by means of processing techniques from melting such as forming, molding, extrusion or injection. Since some of the most interesting properties of the compounds of the invention are the tribological ones, that is, their low friction and the reduction of mechanical wear by rubbing with other parts, the application as a protective coating of this material is of primary interest.

Therefore, another aspect of the present invention refers to the use of the composition of the invention as a tribological polymeric coating for any type of parts or materials.

The pieces to be coated can be both flat and curved geometries and can be selected from plastic, ceramic or metal. In addition, the present invention relates to a method for coating a material comprising the application of films of thickness between 1 and 100 microns of the composition of the invention, in a molten or semi-molten state, on the flat or curved surfaces of the piece of said material to be coated.

Throughout the description and the claims, the word "comprises" and its variants are not intended to exclude other technical characteristics, additives, components or steps. For those skilled in the art, other objects, advantages and characteristics of the invention will emerge partly from the description and partly from the practice of the invention. The following examples and drawings are provided by way of illustration, and are not intended to be limiting of the present invention.

BRIEF DESCRIPTION OF THE FIGURES Figure 1. Shows the scanning electron microscopy image of the Nylon-6/2% IF-WS ₂ nanocomposite.

Figure 2. It shows the thermogravimetric curves of the nanocomposites of Nylon-6 / l F-WS ₂ in an oxidative atmosphere.

Figure 3. Represents the dynamic records of the storage module (a) and the loss factor (b) of the Nylon-6 / l F-WS ₂ nanocomposites at 1 Hz. The values of the storage module of the storage units are also presented. nanocomposites at room temperature (c).

Figure 4. Shows the friction tests of pure Nylon-6 and its nanocomposite with 1% IF-WS ₂ . Figure 5. Shows the scanning electron microscopy image of the Nylon-11 nanocomposite with 1% by mass of MoS ₂ nanotubes.

Figure 6. Shows a diagram of the method of application of nanocomposite coatings object of the invention on cylindrical parts.

EXAMPLES OF REALIZATION.

EXAMPLE 1. Manufacture of Nylon-6 matrix nanocomposite materials with spherical nanoparticles of WS ₂ inorganic fulerene. Characterization of its thermal, mechanical and tribological properties.

In the first example, a family of nanocomposite materials has been obtained by incorporating different concentrations of FI-WS ₂ nanoparticles to the polyamide of greater industrial use, the nylon-6 Nearly spherical or slightly ellipsoidal FI-WS ₂ nanoparticles were used, with an aspect ratio between 1 and 1.3, and an average diameter of 80 nm. For this, the Nylon-6 was mixed, which was previously subjected to a drying process at 12O ⁰ C for 24 hours, with FI-WS ₂ concentrations of 0.1, 0.5, 1 and 2% by weight, in a micro-extruder (Thermo-Haake Minilab system), using the following optimal processing conditions: temperature = 24O ⁰ C, time = 10 min and screw speed = 150 rpm. Subsequently, the resulting mixtures were compression molded into a press in the form of 0.5 mm thick films.

Characterization of the properties of the IF-WS? / Nylon- 6 nanocomposites

a) Dispersion of particles. Figure 1 shows an image of scanning electron microscopy, in which the dispersion of independent inorganic fulerenes is observed. b) Thermal stability. The thermal stability of the nanocomposite was evaluated by thermogravimetric analysis using a Mettler TA4000 / TG50 thermobalance. The temperature range studied was 50 to 600 ⁰ C with a heating rate of 20 ° C / min, as shown in Figure 2. The incorporation of FI-WS ₂ produced a spectacular increase in the thermal stability of Nylon- 6, resulting in an increase of 4O ⁰ C in the initial degradation temperature from 298 ⁰ C to 338 ⁰ C, for nanocomposites reinforced with 2% by weight of IF-WS ₂ . c) Mechanical properties. The mechano-dynamic properties for the nanocomposite series were measured by subjecting a series of rectangular geometry specimens (~ 19.5 ^ 5x0.5 mm ³ ) to strain deformations. The temperature range used was from -15O ⁰ C to 18O ⁰ C. In In all cases a heating rate of 2 ° C / min was used and a dynamic force of 6 N was applied. A maximum displacement of 30 microns was set. All measurements were carried out at frequencies of 0.1, 1 and 10 Hz. As an example, Figure 3 shows the variation of the storage module and the loss factor at 1 Hz. At room temperature, the values of the storage module obtained (Figure 3c) indicate that the nanoparticles contribute to a dramatic increase in the stiffness of the nanocomposites with respect to pure Nylon-6. This is probably due to the good dispersion of the nanoparticles that leads to a greater surface of particle-polymer contact. On the other hand, the variation of the loss factor (tanδ) as a function of the temperature and the concentration, indicates that the presence of IF-WS2 does not modify the values of the temperatures of secondary transitions (β, γ) of the Nylon-6. However, in the temperature range associated with the vitreous transition of Nylon-6, the slight reduction in the width of the transition could be related to the formation of the amorphous phase, less heterogeneous in the presence of the nucleating nanoparticles of IF-WS2. d) Tribological properties. Here the influence of the nanoparticles of IF-WS ₂ on the tribological properties of Nylon-6 is demonstrated.

Figure 4 shows the evolution of the coefficient of friction in ball-to-disk tests carried out with a chrome-plated steel ball under a load of 5 N. As can be seen in Figure 4, pure Nylon 6 is a material that has good properties in Regarding friction and wear resistance. Its coefficient of friction is of the order of 0.1. The incorporation of IF-WS2 produces a reduction in the friction coefficient of pure Nylon-6 of the order of 25% (0.075). The final product obtained with the process of this invention can better withstand the loads. And therefore, it can extend the life of Nylon-6 in situations of high tribological requirements, such as high wear resistance. EXAMPLE 2. Manufacture of nanocomposite materials of Nylon-11 matrix with MoS ₂ inorganic leaflets in the form of nanotubes.

In the second example we want to state the generality in the choice of the components of the composite material. Three parameters of the nanocomposite system have been varied: (i) firstly the matrix polymer, which is now nylon-11, has been varied, (ii) secondly, the chemical composition of the inorganic fulerene material, which is now M0S, has been varied ₂ , and (iü) thirdly, the geometry of the nanoparticle has been varied, which are now nanotubes with an average diameter of 100 nm and an average length of 1 millimeter. The results of particle dispersion (shown in Figure 5), and increase in thermal, mechanical and tribological properties are comparable to those presented in Example 1, using the same synthesis conditions and concentrations of Fl-M0S2 as in the example one.

EXAMPLE 3. Method of application of coatings of the nanocomposites object of the invention on pieces with flat and cylindrical symmetry.

The third example of embodiment refers to the application of the material object of the invention as coating parts to improve its surface properties. The method of application of the coating consists of three stages: (i) firstly the nanocomposite material object of the invention is previously prepared in the form of films of thickness between 1 and 100 microns, (ii) then the film is heated until it reaches to a molten or semi-molten state, and (iii) the hot film is applied on the flat or curved surfaces of the piece to be coated. As a concrete example, flat plates and steel cylinders have been coated with the nanocomposite material described in example 1. For this purpose Firstly, films of the nanocomposite of Example 1 of a thickness of 20 microns were prepared by processing from the melt, in particular by pressing between parallel plates. In the case of coatings on flat substrates, the nanocomposite films are heated to their melting temperature (240 °) by placing them on a polyimide non-stick film in contact with a heating plate, and the flat face of the piece to be coated is placed on contact with the molten nanocomposite material, producing the metal-polymer bond. Since the adhesion of the nanocomposite against steel is less than that of the pure polyamide against steel, a polyamide-steel joint is previously made on which the nanocomposite coating is subsequently placed. In the case of cylindrical parts, the same scheme is followed, rolling the cylindrical surface on the molten polymer material, as indicated in the scheme of Figure 6.

Claims

1. Polymeric composition comprising a polyamide matrix containing nanoparticles of inorganic fulerenes, wherein said nanoparticles have at least two reduced dimensions of a size smaller than 200 nm.

2. Composition according to claim 1, wherein the polyamide is nylon or an aramid.

3. Composition according to any of claims 1 or 2, wherein the nanoparticles are in the form of nanotubes, nanospheres or nanoelipsoids.

4. Composition according to any one of claims 1 to 3, wherein the nanoparticles are sulfides or selenides of transition elements.

5. Composition according to any of claims 1 to 4, wherein the nanoparticles are in a proportion less than 10% by weight of the final composition.

6. Composition according to claim 5, wherein the nanoparticles are in a proportion less than 5% by weight of the final composition.

7. Method for obtaining the composition according to any of claims 1 to 6, characterized by high temperature mixing of a molten polyamide and inorganic fulerene nanoparticles.

8. Method according to claim 7, which further comprises the addition of compatibilizers and surfactants.

9. Use of the composition according to any of claims 1 to 6, for the manufacture of plastic parts.

10. Use of the composition according to any of claims 1 to 6, for the manufacture of articles by means of forming, molding, extrusion or injection techniques.

11. Use of the composition according to any of claims 1 to 6, as a tribological polymeric coating of materials.

12. Use of the composition according to claim 11, wherein the materials are flat or curved pieces that are selected from plastic, ceramic or metal.

13. Method for coating a material comprising the application of films of thickness between 1 and 100 microns of the composition described in any of claims 1 to 6, in a molten or semi-molten state, on the flat or curved surfaces of the part of said material to be coated.

14. Method according to claim 13, wherein the material is plastic, ceramic or metal.