CH713639B1 - Watch component in composite material comprising an organic matrix reinforced with graphene. - Google Patents

Abstract

The present invention relates to a watch component (I) made of a composite material comprising an organic matrix reinforced with graphene, said organic matrix being made of a polymer having a Young's modulus E t greater than or equal to 2 and, preferably , at 3 GPa.

Description

TECHNICAL AREA

The present invention relates to the watchmaking field and, more specifically, to a watch component made of a synthetic material reinforced with graphene.

PRIOR ART

In watchmaking, metal alloys are widely used for their remarkable mechanical properties (hardness, ductility, rigidity, absence of brittleness, etc.). Mention may be made of the use of austenitic stainless steels, brass or even titanium alloys for watch cases, dials, hands, etc. However, they have the disadvantage of being relatively heavy with densities greater than 4 for titanium alloys and greater than 8 for brasses or stainless steels. They are also expensive and require a machining step for the final shaping. Synthetic materials with their low density and their direct forming in injection molds make it possible to overcome these disadvantages. However, they have the drawback of being less efficient in terms of mechanical properties than metal alloys.

To date, there is still a demand in watchmaking for materials combining the advantages of metal alloys and synthetic materials. More specifically, there is a demand for materials combining lightness, mechanical strength, ductility, as well as other properties such as corrosion resistance and wear resistance.

SUMMARY OF THE INVENTION

[0004] The object of the present invention is thus to provide a composite material exhibiting a compromise between the mechanical properties of metal alloys and those of synthetic materials, for use in watch components.

To this end, the present invention provides a watch component made of a synthetic material reinforced with graphene. This synthetic material comprises a matrix made from a so-called high or ultra high performance polymer such as PEEK.

The watch component made from this material has the advantage of being light thanks to the low density of the material with values of the order of 1.3 while having superior mechanical properties thanks to the reinforcement of the matrix with graphene.

[0007] Other characteristics and advantages of the present invention will become apparent from the following description of a preferred embodiment, presented by way of non-limiting example with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

Figures 1 and 2 represent respectively a watch case and a casing ring made with a composite material according to the invention.

DESCRIPTION OF THE INVENTION

The present invention relates to a watch component made of a synthetic material reinforced with graphene. The horological component can be a covering component such as a watch case, a caseband, a back, a bezel, a push-button, a bracelet link, a bracelet, a dial, a casing ring, etc. or a component of the movement such as a bridge or a plate, etc. By way of illustration, FIGS. 1 and 2 represent a watch case 1 and a casing ring 2 designed with a composite material, according to the invention.

The composite material comprises an organic matrix made with a so-called high or ultra high performance polymer. These are polymers that withstand extreme environments. Their performance is based on high chemical, thermal, pressure, fatigue and abrasion resistance. These materials are also known for their high strength properties and high moduli.

The high or ultra high performance polymers generally exhibit tensile strength properties greater than or equal to 70 or even 80 MPa with an elongation at break greater than or equal to 3% and a Young's modulus greater than or equal to 3GPa. Certain high-performance polymers such as PVDF may nevertheless exhibit weaker properties with a Young's modulus greater than or equal to 2GPa, a tensile strength greater than or equal to 30 MPa with, as a corollary, an elongation at break greater than or equal. at 20% which can go up to values of 300%.

The polymers chosen according to the invention are characterized more precisely by their Young Et's modulus greater than or equal to 2 and, preferably, to 3GPa according to the ISO 527-1: 2012 standard. Preferably, the ultra-high performance polymers are PAEK (Polyaryletherketone), PEEK (Polyetheretherketone), PEKK (Polyetherketonketone), PFSA (Perfluorosulfonic acid), PI (Polyimide), SRP ('Self-reinforced' polyphenylene), PAI (Polyamide-imides), HTS) (High temperature sulfone) and the high performance polymers are PPS (Polyphenylene sulfide), PSU (Polysulfone), PPSU (Polyphenylsulfone), PPA (Polyphthalamide), PFA (Perfluoroalkoxy), MFA (Perfluoromethylalkoxy), PVDF (Polyvinylidene fluoride). More preferably, the polymer chosen is PEEK.

According to the invention, graphene and, more precisely, a graphene powder is combined with one of these polymers of the high to ultra high performance type to obtain a polymer / graphene composite with rigidity and ultimate properties (elastic limit , tensile strength, elongation, etc.) high. The content by weight of graphene in the composite is between 0.1 and 15%, preferably between 0.5 and 10%, more preferably between 1 and 5% (limits included). The addition of graphene to the polymer makes it possible to develop an infinite number of rigid candidates, which can be injected by transformation methods well known to those skilled in the art. According to the invention, graphene obtained from various manufacturing processes (chemical vapor deposition, mechanical and chemical exfoliation, etc.) can be used. By way of example, the graphene according to the invention can be an FLG (Few-Layer Graphene) graphene which has an average thickness of 4 to 6 nm and is composed of 3 to 5 carbon layers.

The composite material reinforced with graphene exhibits, among other things, improved flexural and tensile properties with, according to ISO 527-1: 2012, a yield point stress σy as well as a breaking stress σb greater than or equal to 80 MPa and, preferably to 90 MPa, a strain in the flow εys greater than or equal to 3%, and preferably to 4%, and a Young's modulus Et greater than or equal to 3.5 and, preferably, to 4GPa. Furthermore, the Ef flexural modulus according to the ISO 178: 2010 standard is greater than or equal to 3.5 and, preferably, 4GPa. The reinforced material has a density of between 1 and 3g / cm <3> determined according to the ISO 1183-1: 2012 standard.

The final performance of the mixture does not depend only on the proportion of graphene in the polymer but also on the method of incorporating graphene into the polymer matrix. By using a mixing extruder of the “twin screw extruder” type, it is possible to disperse the graphene in the matrix to obtain unusual performance properties in terms of rigidity, thermal conductivity, electrical conductivity, breaking limits, anisotropy, phase ratio. crystalline / amorphous. These properties can be adjusted according to the specifications of the final part.

The results obtained from PEEK / graphene mixtures according to the invention are given below.

Examples

The formulas were developed from PEEK and Nanoxplore heXo-G V4 graphene. Three formulas were tested. A first reference does not contain graphene and is referenced PEEK in table 2 below. In a second formula according to the invention, the material comprises 2% by weight of graphene. In a third formula according to the invention, the material comprises 5% by weight of graphene. Table 1 shows the characteristics of the Nanoxplore heXo-G V4 graphene. It is an FLG (Few-Loyer Graphene) graphene produced by ball mill technology. Average thickness (nm) 4-6 Average dimension of the straw (µm) 3 Volume density (g / cm <3>) 0.13 BET surface (m <2> / g) 100-150 Carbon powder appearance (% by weight)> 93 Oxygen (wt%) <4 Ash (wt%) 2.7

Table 1

The mixtures were produced in an extruder of the "twin screw extruder" type and injected at a temperature of 390 ° C.

The mechanical properties of the samples were measured as well as their densities. Table 2 shows the results of density measurements, tensile tests and bending tests. The tensile tests were carried out according to ISO 527-1: 2012. In accordance with this standard, the yield point stress σy, also called the elastic apparent limit, the ultimate stress σb, the strain in flow εy and the Young's modulus Et were measured. The density measurements p were carried out according to the ISO 1183-1: 2012 standard. Furthermore, the flexural modulus Efa was measured according to the ISO 178: 2010 standard. Each test was repeated twice for each grade, table 2 shows the average. Ref PEEK 1.29 3900 97.6 81.9 5.1 3780 + 2% graphene 1.32 4500 97.3 96.6 5 4465 + 5% graphene 1.31 4510 96 94.8 4.2 4510

Table 2

It is observed that the materials with graphene exhibit a tensile stress σb increased by nearly 20% while keeping an elastic deformation εysimilar of the order of 5%. Likewise, a significant increase in Young's modulus Et and in flexural modulus Efest observed with increases of 15% and almost 20% respectively. Few differences are observed between the samples reinforced with 2 or 5% graphene, 2% graphene in the case of a PEEK matrix already making it possible to obtain improved performance.

Claims (7)

1. Timepiece component made from a composite material comprising an organic matrix reinforced with graphene, said organic matrix being made from a polymer having a Young Et's modulus greater than or equal to 2 and, preferably, to 3GPa. 2. Watch component according to claim 1, characterized in that the percentage by weight of graphene in the composite material is between 0.1 and 15%, preferably between 0.5 and 10% and more preferably between 1 and 5%. 3. Watch component according to claim 1 or 2, characterized in that the organic matrix is made from a polymer chosen from the list comprising PAEK, PEEK, PEKK, PI, SRP, PAI, HTS, PPS, PSU, PPSU and PPA. . 4. Watch component according to claim 3, characterized in that the polymer is PEEK. 5. Timepiece component according to one of claims 1 to 4, characterized in that the composite material has a yield point stress σyet a tensile stress σbrrespectively greater than or equal to 90 MPa, a deformation at the flow threshold εysuperior or equal to 3% and, preferably, greater than or equal to 4%, a Young Et's modulus greater than or equal to 3.5 and, preferably, to 4GPa. 6. Watch component according to one of claims 1 to 5, characterized in that it is chosen from the list comprising a watch case, a casing ring, a caseband, a back, a bezel, a push-button, a link. bracelet, a bracelet, a dial, a bridge and a plate. 7. Watch comprising the horological component according to one of claims 1 to 6.