TW202116380A - Monofilament string for a racket - Google Patents

Abstract

The present invention relates to a monofilament string (1) for a racket (5), comprising a core (2) consisting of a single filament and a sheath (3) extending around the core (2) and in contact with the core (2), wherein: - the core (2) is made of a first material comprising at least a polyamide, - the sheath (3) is made of a second material comprising at least a polyamide, wherein the second material comprises graphene or graphane nanoparticles with a concentration ranging from 0.1% to 5% in weight, preferably from 0.1% to 2% in weight, and more preferably from 0.1% to 1% in weight of the weight of the sheath.

Description

Monofilament thread for rackets

Field of invention

The present invention relates to monofilament threads and a group of such threads used in rackets, such as tennis rackets, squash rackets, badminton rackets or the like.

Background of the invention

In the field of racket sports, a racket is made of a handle and a hoop. A set of lines extends across the hoop in two orthogonal directions and is intended to withstand the impact of a ball, shuttlecock or the like.

The technological evolution in this field is being promoted towards more and more competitive rackets, involving major improvements in the string structure and manufacturing, especially in the materials that make up the string.

According to a general point of view, the system sought has a racket whose string shows good or at least mediocre energy, control, comfort and durability characteristics. The energy characteristic refers to the ability of the line to increase the speed of the ball leaving the line when the athlete hits the ball. The control characteristic refers to the ability of the line to influence the behavior of the ball, thereby making it possible for the athlete to accurately hit the ball to a predetermined position, decelerate the ball and affect the rotation of the ball. The comfort characteristic refers to the ability of the line to reduce the vibration of the racket caused by the line that is hit by the ball when the player hits the ball. And finally, the durability characteristic refers to the thread with less deterioration of its structure over time and use, which in particular causes less tension loss, so that the thread can maintain its energy, control and/or comfort characteristics.

Among the different types of threads, threads made of natural gut have low stiffness, which allows players to accelerate the ball without high physical strength. However, it provides poor ball control. This is also true for multifilament threads usually made of polyamide.

Monofilament threads and multifilament threads are usually made of polyethylene, polyester or polyamide. The thread made of polyethylene and polyester has high stiffness, which enables players to become precise and have good ball control. However, the athlete needs to have high physical strength in order to accelerate the ball. A thread made of polyamide shows these characteristics and also provides a powerful ability to dissipate racket vibration, but tends to quickly deteriorate and lose tension.

Therefore, there is a need for a monofilament thread that shows a good balance between energy characteristics and control characteristics, and at the same time has good comfort and durability characteristics.

In particular, a monofilament thread is required, which exhibits high energy characteristics, so that the athlete can easily increase the speed of the ball without high physical strength, and at the same time, allows the athlete to have good ball control and a reasonable amount of time (preferably game time, It takes several hours for experienced athletes, especially 2 to 4 hours) to maintain a substantially constant tension.

The document FR 2 934 958 aims to enhance the durability of the racquet string, and discloses a monofilament string comprising a central core, a peripheral protective layer, and an intermediate reinforcing layer positioned between the central core and the peripheral protective layer and made of composite materials.

The middle reinforcing layer improves the durability of the thread by increasing the stiffness of the thread while impairing the elasticity of the thread, but this leads to a decrease in the energy characteristics of the thread because the ability of the thread to bend under the impact of the ball is weakened.

The document WO2018234376 discloses a monofilament thread that improves the balance between energy characteristics and control characteristics. However, the durability of the thread over time and use needs to be further improved.

Documents US 2008/0206559 and US 2012/0237767 have reported that carbon nanotubes are used as additives in wear-resistant coatings wrapped around multifilament threads. However, such carbon nanotubes significantly stiffen the materials including them, and thus make the materials difficult to process.

Summary of the invention

One object of the present invention is to provide a monofilament thread that overcomes the above-mentioned disadvantages.

In particular, the present invention aims to provide a monofilament thread that exhibits a good balance between energy characteristics and control characteristics, and at the same time has good comfort and durability characteristics, as well as enhanced elapsed time and durability compared with existing threads. At the same time, the wire can be manufactured by a co-extrusion process.

To this end, an object of the present invention is a monofilament thread for a racket, the monofilament thread comprising a core composed of a single thread and a sheath extending around the core and in contact with the core, wherein: -The core is made of the first material containing at least polyamide, -The sheath is made of a second material containing at least polyamide, Wherein the second material is a polyamide matrix, based on the weight of the sheath, the polyamide matrix is 0.1% to 5% by weight, preferably 0.1% to 2% by weight, and more preferably 0.1% to 1% by weight Concentrations within the weight% range include graphene or graphane nano-particles.

In the present invention, "polyamide matrix" means a matrix containing at least one polyamide homopolymer and/or copolymer. Specifically, the matrix may include PA6, PA6.6, PA11, PA12, PA4.6 and/or copolymers thereof. The matrix may include other polymers, and the total weight percentage of polyamide is greater than the total weight percentage of the other polymer(s). The matrix may also include fillers or additives.

By incorporating graphene or graphane into the material used to form the sheath, the characteristics of the thread remain substantially the same in terms of comfort, control, and energy. However, the durability of the thread over time and use, that is, its ability to not deteriorate has been significantly improved.

In addition, the graphene or graphane content is selected to be low enough so that the monofilament can be manufactured by a co-extrusion process. In particular, during coextrusion, the monofilament must be stretched to exhibit the required mechanical properties. Excessive graphene or graphane content provides excessive rigidity of the material during the coextrusion process, which hinders proper stretching, resulting in poor monofilament mechanical properties. However, due to the low graphene or graphane content used in the present invention, the monofilament can be stretched to a sufficient degree during the coextrusion process and thereby achieve the desired mechanical properties.

Graphene is an allotrope of carbon, in the form of a two-dimensional, atomic-scale hexagonal lattice, with one atom forming each vertex.

Graphane is a form of hydrogenated graphene. More precisely, graphane is a two-dimensional polymer of carbon and hydrogen, with the chemical formula unit (CH) _n , where n is a large integer.

Such graphene or graphane nano particles make the wire structure stable, and the nano size of the carbon particles does not make the wire severely hardened. It is different from some based on fluorine, molybdenum disulfide or especially Kevlar fibers. The other additives are the opposite.

Graphene nanoparticles also improve the temperature resistance and the sliding of one line on the other. By avoiding premature deterioration of the line, it also improves the stability over time.

The term "rigidity" as used herein refers to the tensile modulus (also known as "Young's modulus" or "elastic modulus") of the material. Materials with high rigidity exhibit high tensile modulus and therefore low elasticity.

The term "geometric stiffness" or simply "stiffness" used in this article is similar to the term "rigid", but is related to structure. The stiffness of the structure depends on the rigidity of the material it is made of and its spatial characteristics.

According to other optional features of monofilament thread: -Monofilament thread is obtained by co-extrusion of core and sheath; -The second material includes at least one of the following: polyamide 6, polyamide 6.6, polyamide 11, polyamide 12, polyamide 66 and mixtures thereof; -The first material includes polyamide 6 and the first copolymer of polyamide 6 and polyamide 6.6, and the second material includes the second copolymer of polyamide 6 and polyamide 6.6; -The tensile modulus of the first material is greater than the tensile modulus of the second material. -The second material further includes at least one additive selected from the group consisting of: a slip agent and a hydrophobic agent.

Another object of the present invention is a racket comprising a set of monofilament strings described previously.

Another object of the present invention is a process for manufacturing monofilaments as described above. In this process, the core and sheath are formed by a co-extrusion process. The process further includes drawing the monofilament.

Detailed description of the preferred embodiment

The present invention proposes a monofilament string for a racket.

The monofilament thread includes a core and a sheath coaxial with the core and made of a polyamide matrix including graphene or graphane nanoparticles.

The polyamide matrix comprises at least one polyamide homopolymer and/or copolymer, which is preferably selected from the following: polyamide 6, polyamide 6.6, polyamide 11, polyamide 12, polyamide 66 And its mixtures.

The matrix may include other polymer(s) other than the polyamide polymer. However, the total weight percentage of polyamide is always greater than the total weight percentage of other polymer(s). The polyamide matrix may also include fillers or additives.

The polyamide matrix provides high stiffness to the monofilament thread, which enables players to become precise and have good ball control; and provides the monofilament thread with a powerful ability to dissipate racket vibration, which improves comfort.

The presence of graphene or graphane nano-particles in the polyamide matrix maintains the good properties provided by the polyamide matrix, and at the same time strongly improves the durability of the thread and the use. Therefore, the string set of the racket maintains its good characteristics in terms of comfort, control and energy for a period of time for continuous improvement, and even when the string is under high pressure, if it does not prevent the string from breaking, it strongly reduces the string fracture. In other words, the ability of the thread to not deteriorate is significantly improved.

In terms of imparting enhanced durability to the wire without excessively increasing the stiffness, the graphene or graphane nanoparticle in an amount of 20% by weight or less relative to the weight of the part including the nanoparticle is the best of. Preferably, the weight percentage of graphene or graphane nanoparticles is in the range of 0.1% to 5%, more preferably 0.1% to 2%, and even more preferably 0.1% to 1%.

Graphene and graphane are excellently suitable for incorporation into the polyamide matrix, and both of them provide enhanced durability properties. Graphene and graphane particles are regarded as two-dimensional (2D) particles due to their flaky structure extending in a plane. In contrast, carbon nanotubes, which are other types of carbon nanoparticles, are three-dimensional (3D) particles, because they can be regarded as carbon flakes that are wound around themselves to form a cylinder.

The enhanced durability comes from the specific mechanical and thermal properties of carbon nanoparticles.

In more detail, in the graphite corresponding to the stack of graphene layers, the carbon planes are weakly related to each other. On the contrary, in each graphene plane, the carbon atoms are connected by extremely stable bonds. This is also true for graphane nanoparticles. Therefore, the material is mechanically very stiff in the plane (over one hundred times of steel of the same thickness), while being deformable. Combined with shock-absorbing materials, carbon nanoparticles can form extremely strong and flexible materials. For example, the Young's modulus of graphene is about 1.0 TPa (Tera Pascal), which makes graphene a very stiff material.

Graphene and graphane nanoparticles are also extremely light. For example, the density of graphene is about 2.25 g/cm ³ , which is extremely low.

Therefore, graphene and graphene nanoparticles used in suitable concentrations as mentioned above exhibit high rigidity and lightness, thereby stabilizing the wire structure without severely hardening the wire, and are compatible with those based on fluorine, molybdenum disulfide or In particular, some other additives of Kevlar fiber are the opposite.

An important aspect that has an impact on the energy characteristics of the racquet string is the sliding of the strings on each other and the friction generated by the contact of the strings when sliding. In more detail, when the player hits the ball, the ball engages the wire, bending the wire and thereby sliding on each other in the first direction while being pressed against each other. After hitting the ball, the ball leaves the line, returning the line to its initial resting position and sliding on each other in a second direction opposite to the first direction.

In addition to rigidity and lightness, graphene and graphane nanoparticles provide good sliding properties to the wires, which reduces the friction between the wires during sliding.

Graphene and graphane nanoparticles show high thermal conductivity and thermal stability. The thermal conductivity of graphene is about 5000 Wm ^-1 .K ^-1 , which is 10 times higher than copper, 20 times higher than aluminum, and 2 times higher than graphite. Therefore, graphene and graphane nanoparticles provide the string with an improved ability to regulate and disperse the heat in the string set of the racket.

An embodiment of the monofilament thread of the present invention is shown in FIG. 1.

The monofilament thread 1 includes a core 2 composed of a single filament, and a sheath 3 extending around the core and contacting the core. The core 2 has a circular cross-section and the sheath 3 has an annular cross-section, and the sheath is coaxial with the core.

The core 2 is made of a first material comprising a first copolymer of polyamide 6 and polyamide 6.6 (first copolymer PA 6/6.6), and the sheath is made of a first material comprising polyamide 6 and polyamide 6.6. The second material of the di-copolymer (the second copolymer PA 6/6.6, which can be the same as the first copolymer) is made.

Polyamide 6 and polyamide 6.6 are thermoplastic semi-crystalline polymers that exhibit good mechanical properties. They are all fairly rigid polymers, but the tensile modulus of polyamide 6 is higher than that of polyamide 6.6.

For example, the tensile modulus of polyamide 6 is generally between 700 MPa (Mega Pascal) and 800 MPa, while the tensile modulus of copolymer PA 6/6.6 is generally 500 MPa And 600 MPa.

The polyamide matrix including graphene or graphane nanoparticles is in the sheath.

According to an embodiment (not shown), the polyamide matrix including graphene or graphane nanoparticles is in both the core and the sheath.

According to a preferred embodiment, the graphene or graphane nanoparticle is only in the sheath, and the weight of the sheath represents 0.1% to 5% by weight, preferably 0.1% to 2% by weight, and more preferably 0.1 Weight% to 1% by weight.

The mechanical properties of copolymer PA 6/6.6 are generally somewhere between the mechanical properties of polyamide 6 and the mechanical properties of polyamide 6.6. Block copolymer PA 6/6.6 is better, because the characteristics of the latter may be very close to the better characteristics of polyamide 6 and polyamide 6.6, without suffering the corresponding loss of other desired characteristics, depending on the copolymer PA 6/6.6 The structure of the copolymer PA 6/6.6, the respective ratio of polyamide 6 and polyamide 6.6, and the production process of copolymer PA 6/6.6.

Therefore, the copolymer PA 6/6.6 has a tensile strength between the tensile strength of polyamide 6 and the tensile strength of polyamide 6.6, or substantially equal to the tensile strength of polyamide 6.6.

The first material is preferably selected so as to have a greater tensile modulus than the tensile modulus of the second material.

For this purpose, the first material contains polyamide 6 in addition to the first copolymer PA 6/6.6. Polyamide 6 provides the first material with high rigidity and strong ability to dissipate mechanical action (energy) during elastic deformation.

The core 2 thus provides the monofilament thread 1 with high geometric stiffness and the ability to strongly absorb/dissipate the mechanical action applied to the thread when the thread is hit by a ball or the like, which produces better ball control, and The vibration transmitted through the screen 8 and the handle 9 of the racket 5 shown in FIG. 2 is reduced.

One result is racket 5 so that players can decelerate the ball after receiving and hitting the ball in order to better control the ball. Another result is that athletes experience less vibration and impact when hitting the ball for better comfort, thereby preventing injuries, such as tennis elbow, for example in the case of tennis rackets.

Preferably, the sheath does not contain polyamide 6. However, it must be understood that the second material may contain polyamide 6, but its amount is significantly lower compared to the first material. In this case, the weight percentage of polyamide 6 in the second material (relative to the second material) is significantly lower than the weight percentage of polyamide 6 in the first material (relative to the first material).

Similarly, the amount of polyamide 6 in the copolymer PA 6/6.6 of the first and second materials is also adjusted so that the tensile modulus of the first material is greater than the tensile modulus of the second material. Advantageously, the weight percentage of polyamide 6 in the copolymer PA 6/6.6 of the second material is lower than the weight percentage of polyamide 6 in the copolymer PA 6/6.6 of the first material.

Therefore, the tensile modulus of the second material (sheath) is lower than the tensile modulus of the first material (core). Therefore, compared with the first material, the second material is more elastic, absorbs less energy and releases more energy during elastic deformation.

The sheath 3 thus provides the monofilament thread 1 with the ability to strongly release the mechanical action applied to the thread when the thread is hit by a ball or the like.

One result is that the racket allows the player to strongly accelerate the ball when hitting the ball.

The thread 1 is preferably obtained by co-extruding the core 2 and the sheath 3.

The co-extruded core 2 and sheath 3 form an interface 4 at the contact area between the core and the sheath, in which the core and the sheath are tightly connected.

As previously described, the core 2 and sheath 3 of the thread 1 are similar in terms of chemical structure. The core and sheath are actually made of polyamide-based materials, namely copolymer PA 6/6.6.

The strong mechanical and chemical cohesion of the core 2 and the sheath 3 at the interface 4 allows the core and sheath to work together when the thread is mechanically required, thereby further improving the overall mechanical properties of the thread, especially its durability and its ability to affect the rotation of the ball .

In the wire, the weight ratio of the sheath 3 is small compared to the weight ratio of the core 2. Specifically, the sheath preferably represents 5% to 20% by weight of the total weight of the thread 1, more preferably 8% to 16% by weight. The core preferably represents 80% to 95% by weight of the total weight of the thread, more preferably 84% to 92% by weight.

In terms of thickness, the thickness of the sheath 3 represents 2% to 7% of the total thickness of the wire 1, preferably 3% to 6%, and the thickness of the core 2 represents 93% to 98%, preferably 94% of the total thickness of the wire 1. To 97%.

In more detail, the thickness of the sheath is preferably in the range of 20 micrometers and 50 micrometers, and the thickness of the core (which corresponds to the diameter) is in the range of 1200 micrometers and 1500 micrometers.

Together with the composition of the first and second materials of the core and the sheath, such a high weight ratio of the core to the sheath makes it possible to have a thread with high control characteristics.

Unexpectedly, although the resulting weight ratio of the sheath is low, the sheath is sufficient to provide high-energy properties to the thread, especially by imparting explosive properties to the thread. In the context of the present invention, "explosive" means that the racket returns the ball at a great speed.

The combination of core and sheath thus provides a good balance between control characteristics and energy characteristics.

Of course, depending on the user's intention to play the ball, the composition and ratio of the core and sheath can be adjusted to provide the best trade-off between control characteristics and energy characteristics.

In order to further reduce the friction between the wires during sliding, the sheath advantageously contains one or more additives that promote the sliding of the wires relative to each other, thereby providing the wires with enhanced power and rebound ability, and in general, enhanced energy characteristics.

The additives are preferably selected from the group consisting of slip aids and hydrophobic agents.

Among the slip aids, preferred additives are selected from: erucamide, such as stearyl erucamide; ethylene distearylamide; polydimethylsiloxane based on polyamide Alkane; Polyamide-based silicone with ultra-high molecular weight; Fluorine-based polymer; Molybdenum disulfide-loaded polymer.

Among the hydrophobic agents, the preferred additives are selected from: silicone-based polymers with ultra-high molecular weight, polydimethylsiloxane-based polymers, silicon dioxide-based compounds, and ceramic nanoparticle-based compounds .

For the purpose of reducing friction between threads during sliding, coatings of such additives or other substances can also be applied on the peripheral surface of the sheath, especially during the manufacturing of the threads.

According to an embodiment, in addition to or as an alternative to the presence of a slip or hydrophobic agent in the sheath, a coating may be applied to the outer surface of the sheath. The coating may have non-slip and/or water-repellent properties.

The monofilament thread according to the present invention has the following characteristics: -The shock absorption capability provided by core 2, which is due to the low elasticity of the core; -The power and rebound ability provided by the sheath 3. This is due to the sheath's high elasticity and low friction; -High durability characteristics, its structure and tension are less degraded over time and use. This is due to the relatively high tensile modulus of polyamide 6 and copolymer PA 6/6.6. The aforementioned properties of the thread, as well as the overall mechanical properties, are further improved by co-extruding the core and sheath, and forming an interface 4 therebetween.

Therefore, the monofilament thread shows a good balance between energy characteristics and control characteristics, while also having good comfort and durability characteristics.

Due to the presence of graphene or graphane nano particles in the sheath, the monofilament thread according to the present invention also has the following characteristics:-Increased rigidity and durability and acceptable lightness due to graphene or graphane nano particles The particles have a structure that strengthens the wire without making the wire severely hardened (due to the nanometer size of the graphene or graphane particles), nor does it cause the wire to seriously increase in weight (due to the low weight of the graphene or graphane particles). Density) ability;-Further improved power and rebound ability, this is due to the reduction of friction between the lines when sliding. Experimental results

Experimental tests and measurements have been performed on three different monofilament wires in order to determine their mechanical properties, and to record the influence of graphene on the mechanical properties of the wires.

The monofilament thread tested in each of the following five examples is the same. They have the same polyamide structure, but the amount of graphene in the sheath is different.

Graphene nanoparticles have a thickness between 1 nm and 2 nm and a lateral dimension between 0.5 μm and 5 μm.

The graphene nanoparticles are provided in the form of powder, which is mixed with plastic particles fed into an extruder.

Alternatively, graphene nanoparticle powder may be mixed with a polyamide polymer to obtain a compound, and the particles made from the compound may then be fed into an extruder.

The tested monofilament thread is as follows: -Line A (1% graphene)-monofilament line, which includes: ●The core containing polyamide 6 and the first copolymer of polyamide 6 and polyamide 6.6, ●The sheath containing the second copolymer of polyamide 6 and polyamide 6.6 ●1% graphene in the sheath; -Line B (3% graphene)-monofilament line, which includes: ●The core containing polyamide 6 and the first copolymer of polyamide 6 and polyamide 6.6, ●The sheath containing the second copolymer of polyamide 6 and polyamide 6.6 ●3% graphene in the sheath -Line C (no graphene)-monofilament line, which includes: ●The core containing polyamide 6 and the first copolymer of polyamide 6 and polyamide 6.6, ●The sheath containing the second copolymer of polyamide 6 and polyamide 6.6.

Each monofilament sample undergoes one hundred 250 Newton (Newton; N) tensile stress cycles for 10 minutes: the sample is stretched and relaxed one hundred times. For each cycle, measure the tensile strength, Young's modulus, tension maintenance, elongation and plastic deformation of the line, and calculate the average value of one hundred cycles. Example 1: The influence of graphene on tensile strength

The graph in Figure 3 shows the evolution of the tensile strength (TS) of the line as a function of the amount of graphene in the sheath.

Adding 1% graphene to the sheath increases the tensile strength of the wire from 564 N to 600 N.

In the case of 3% graphene in the sheath, the tensile strength of the wire is 587 N, which is slightly lower than the case of 1% graphene but higher than that of the case without graphene.

Therefore, adding graphene to the wire improves the tensile strength. Example 2: The influence of graphene on Young's modulus

The graph in Figure 4 shows the evolution of the Young's modulus (Y) of the line as a function of the amount of graphene in the sheath.

Adding 1% graphene to the sheath increases the Young's modulus of the wire from 1629 N/mm ² to 1726 N/mm ² .

Adding graphene to 3% in the sheath further increases the Young's modulus of the wire to 1774 N/mm ² . Example 3: The effect of graphene on tension maintenance

Each wire sample undergoes a tensile stress (TSS) with an initial value of 250 N for a duration of 10 minutes. The tensile stress of the wire sample naturally decreases with the passage of time. After 10 minutes, the residual tensile stress applied to each wire sample was measured, and the residual tensile stress remained corresponding to the tension of the wire, in Newton (N) as the unit. The results are shown on the graph in Figure 5.

Add 1% graphene to the sheath to maintain the tension of the thread from 223.7 N to 225.8 N.

Graphene is further added to the sheath to 3% to further increase the tension of the thread to 226.5 N.

Tension maintenance affects the durability of the thread, and makes it possible to maintain the mechanical properties of the thread at the same level when the thread is used. Example 4: The effect of graphene on elongation

The graph in Fig. 6 shows the evolution of elongation (E) under 25 kg stress as a function of the amount of graphene in the sheath, which corresponds to a standard tension tennis racket.

Adding 1% graphene to the sheath reduces the elongation of the wire from 10.1% to 9.6%.

Further adding graphene to 3% in the sheath does not change the elongation, which remains at 9.6%. Example 5: The influence of graphene on plastic deformation

The graph in Figure 7 shows the evolution of the plastic deformation (P) of the line as a function of the amount of graphene in the sheath.

Adding 1% graphene to the sheath reduces the plastic deformation of the wire from 0.94% to 0.87%.

Adding graphene to 3% in the sheath further reduces the plastic deformation of the wire to 0.80%.

It was also observed that the deformation was much lower than that of the natural gut D (1.36%). This highlights the better stability of the monofilament thread over time. This is because the less plastic deformation of the thread, the higher the stability of the racket string during deformation.

In short, adding graphene to the wire makes it possible to improve the mechanical properties (string tensile strength, Young's modulus, tension maintenance, elongation and plastic deformation), thereby improving the durability of the racket string (better tension maintenance) , Less time deformation), while maintaining good playing characteristics (comfort, control and energy).

1: Monofilament thread 2: core 3: sheath 4: interface 5: Racket 6: group 8: Screen 9: handle

With reference to the drawings, other features and advantages of the present invention will become apparent from the following embodiments, in the drawings: -Figure 1 is a cross-sectional view of the second embodiment of the monofilament thread of the present invention, wherein the monofilament thread includes a core and a sheath, and the sheath includes graphene or graphane nanoparticles; -Figure 2 is a schematic diagram of a racket containing a set of monofilament strings according to the present invention; -Figure 3 is a graph showing the influence of graphene nanoparticles on the tensile strength of different monofilament threads; -Figure 4 is a graph showing the influence of graphene nanoparticles on the tensile stress modulus of different monofilaments; -Figure 5 is a graph showing the influence of graphene nanoparticles on the tensile mechanical resistance of different monofilament threads; -Figure 6 is a graph showing the influence of graphene nanoparticles on the elongation of different monofilaments; -Figure 7 is a graph showing the influence of graphene nanoparticles on the plastic deformation of different monofilaments.

1: Monofilament thread

2: core

3: sheath

4: interface

Claims (8)

A monofilament thread for a racket. The monofilament thread comprises a core composed of a single thread and a sheath extending around the core and in contact with the core, wherein: -The core is made of a first material containing at least one polyamide, -The sheath is made of a second material containing at least one polyamide, Wherein, based on the weight of the sheath, the second material contains graphene or graphene at a concentration in the range of 0.1% to 5% by weight, preferably 0.1% to 2% by weight, and more preferably 0.1% to 1% by weight Graphane Nanoparticles. The monofilament thread of claim 1, wherein the monofilament thread is obtained by co-extruding the core and the sheath. Such as the monofilament thread of claim 1 or claim 2, wherein the second material comprises at least one of the following: polyamide 6, polyamide 6.6, polyamide 11, polyamide 12, polyamide 66, and Its mixture. Such as the monofilament thread of any one of claims 1 to 3, in which: -The first material includes polyamide 6 and a first copolymer of polyamide 6 and polyamide 6.6, -The second material includes a second copolymer of polyamide 6 and polyamide 6.6. The monofilament thread of any one of claims 1 to 4, wherein the first material has a larger tensile modulus than the second material. The monofilament thread according to any one of claims 1 to 4, wherein the second material further comprises at least one additive selected from the group consisting of: a slip agent and a hydrophobic agent. A racket comprising a set of monofilament strings such as any one of claims 1 to 6. A method for manufacturing the monofilament thread according to any one of claims 1 to 6, wherein the core and the sheath are formed by a co-extrusion method, the method including stretching the monofilament.

Images