Flexible knitted strippable cloth as well as preparation method and application thereof

Abstract

The invention provides flexible knitted peelable cloth and a preparation method and application thereof.The flexible knitted peelable cloth comprises two surface layers and a spacing layer arranged between the two surface layers, yarn of the spacing layer penetrates and is connected between the two surface layers to form the three-dimensional spacing layer, and yarn of at least one surface layer comprises PTFE fiber filaments; through the structural design and limitation of yarn types, the obtained flexible knitted peelable cloth has excellent peelability and gas conductivity, is very suitable for being used in an autoclave forming process of a composite material, and can effectively improve the forming effect of the obtained composite material.

Description

Technical Field

[0001] The invention belongs to the technical field of composite material molding, and in particular relates to a flexible knitted peelable cloth and a preparation method and application thereof. Background Art

[0002] Fiber reinforced composite materials are a new type of material that has good mechanical properties and lightweight characteristics. Peelable cloth is a process auxiliary material in the molding and curing process of composite components. It is also a material placed between the mold and the component to prevent the resin from sticking to the mold. It is often used between the product and the mold to isolate the two and is widely used in composite molding.

[0003] At present, the strippable cloth is mainly woven by ordinary warp and weft yarns through interweaving. For example, CN209425988U discloses a grinding-free demoulding cloth, including a high-density woven demoulding cloth, a resin layer is arranged at the bottom of the high-density woven demoulding cloth, a scratch-resistant coating is arranged at the bottom of the resin layer, and an easy demoulding layer is arranged at the bottom of the scratch-resistant coating. The high-density woven demoulding cloth, the resin layer, the scratch-resistant coating and the easy demoulding layer are arranged in sequence from top to bottom. The grinding-free demoulding cloth can be used in the vacuum infusion molding process. After the high-density woven demoulding cloth is removed, the product surface does not need to be treated and can be directly sprayed with paint, which is convenient to use; the resin layer has the function of blocking the penetration of resin; the scratch-resistant coating enhances the friction resistance of the resin layer and reduces the damage of the resin layer during the laying process; the easy demoulding layer facilitates the separation of the product from the mold, and is highly practical; however, the air permeability of the grinding-free demoulding cloth provided by the utility model is poor, and the release property still needs to be improved.

[0004] Therefore, developing a flexible knitted peelable fabric with excellent peelability and gas conductivity is a technical problem that urgently needs to be solved in this field. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a flexible knitted peelable cloth and a preparation method and application thereof. The flexible knitted peelable cloth has excellent peelability and gas conductivity, is very suitable for use in the autoclave molding process of composite materials, and can effectively improve the molding effect of composite materials.

[0006] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a flexible knitted peelable fabric, the flexible knitted peelable fabric comprising two surface layers and a spacer layer disposed between the two surface layers, wherein the spacer layer contains yarns that penetrate and connect between the two surface layers to form a three-dimensional spacer layer;

[0008] And the yarn of at least one of the surface layers includes PTFE fiber filaments.

[0009] On the one hand, the flexible knitted peelable cloth provided by the present invention comprises two surface layers, and the yarn of at least one of the surface layers comprises PTFE fiber filaments. The PTFE fiber filaments are used to knit at least one of the two surface layers, so that at least one surface of the obtained flexible knitted peelable cloth has excellent peelability, thereby facilitating separation from the composite material; on the other hand, a spacer layer is also provided between the two surface layers, and the yarn of the spacer layer is defined to penetrate and connect between the two surface layers to form a three-dimensional structure, so that the spacer layer can provide sufficiently high support to ensure that the gas can be smoothly conducted in the three-dimensional spacer layer under pressure, thereby making the obtained peelable cloth also have excellent gas conductivity; in the autoclave molding process of the composite material, the flexible knitted peelable cloth provided by the present invention is selected, which not only improves the peeling performance of the prepreg and the peelable cloth, but also can functionally integrate the release property of the conventional peelable cloth and the conductivity of the breathable felt, so that the breathable felt can be omitted in the autoclave lamination, thereby solving the problem of the fiber scraps of the conventional needle-punched breathable felt causing pollution to the composite material parts, and can effectively improve the molding effect of the composite material.

[0010] In some preferred embodiments, the thickness of the flexible knitted peelable cloth is 0.3-0.5 mm, for example, 0.3 mm, 0.32 mm, 0.34 mm, 0.36 mm, 0.38 mm, 0.4 mm, 0.42 mm, 0.44 mm, 0.46 mm, 0.48 mm or 0.5 mm, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0011] In some preferred embodiments, the peel strength of the flexible knitted peelable fabric is ≤20N / 50mm, for example, 20N / 50mm, 18N / 50mm, 16N / 50mm, 14N / 50mm, 12N / 50mm, 10N / 50mm or 8N / 50mm, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0012] In the present invention, the test method for the peel strength of the flexible knitted peelable fabric may refer to GB / T 2792.

[0013] In some preferred embodiments, the flexible knitted peelable fabric is 20 cm thick. 2And the air permeability under the test of 200Pa is ≥2200mm / s, for example, 2200mm / s, 2300mm / s, 2400mm / s, 2500mm / s, 2600mm / s, 2700mm / s, 2800mm / s, 2900mm / s or 3000mm / s, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0014] In the present invention, the test method for the air permeability of the flexible knitted peelable fabric can refer to GB / T5453.

[0015] In some preferred embodiments, the PTFE fiber filament is a monofilament with a linear density of 180 to 400D, for example, 180D, 200D, 220D, 240D, 260D, 280D, 300D, 320D, 340D, 360D, 380D or 400D, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range; 300D is further preferred.

[0016] In some preferred embodiments, the breaking strength of the PTFE fiber filament is ≥3.2cN / dtex, for example, 3.2cN / dtex, 3.4cN / dtex, 3.6cN / dtex, 3.8cN / dtex, 4cN / dtex, 4.2cN / dtex, 4.4cN / dtex, 4.6cN / dtex, 4.8cN / dtex or 5cN / dtex, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range; it is further preferably ≥3.5cN / dtex.

[0017] In the present invention, the test method for the breaking strength of the PTFE fiber filaments may refer to GB / T 14344.

[0018] In some preferred embodiments, the dry heat shrinkage rate of the PTFE fiber filament after heat treatment at 250°C for 30 minutes is ≤5%, for example 5%, 4.5%, 4%, 3.5%, 3%, 2.5%, 2%, 1.5% or 1%, etc., as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range; further preferably, it is ≤3.0%.

[0019] In the present invention, the test method for the dry heat shrinkage of the PTFE fiber filaments may refer to GB / T 6505.

[0020] In some preferred embodiments, the yarns of the two surface layers are PTFE fiber filaments;

[0021] And / or, the yarn in one of the surface layers is PTFE fiber filaments, and the yarn in the other surface layer is any one of polyester fiber, polyamide 6 fiber or polyamide 66 fiber, or a combination of at least two of them.

[0022] In some preferred embodiments, the yarn of the spacer layer includes any one of polyester fiber, polyamide 6 fiber or polyamide 66 fiber, or a combination of at least two of them.

[0023] In some preferred embodiments, the linear density of the yarn of the spacer layer is 100-200D, for example, 100D, 110D, 120D, 130D, 140D, 150D, 160D, 170D, 180D, 190D or 200D, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range; further preferred is 150D.

[0024] In the present invention, the appearance color of the flexible knitted peelable cloth can be white or colorful, and can also contain tracing lines with other colors.

[0025] In a second aspect, the present invention provides a method for preparing the flexible knitted peelable fabric as described in the first aspect, the preparation method comprising: using a double-sided circular knitting machine for weaving to obtain the flexible knitted peelable fabric.

[0026] In some preferred embodiments, the double-sided circular knitting machine has a machine gauge of 32G and 72 yarn supply paths.

[0027] In some preferred embodiments, the weaving method includes: on a double-sided circular knitting machine, using double rib needles, forming a basic structure every 6 routes, the 3F and 6F cylinder needles work to form a surface layer, the 2F and 5F dial needles work to form another surface layer, the 1F and 4F dial needles and cylinder needles work simultaneously to connect the two surface layers to form a spacer layer, completing the weaving to obtain the flexible knitted peelable cloth.

[0028] In some preferred embodiments, a yarn arrangement step is further included before the weaving.

[0029] In some preferred embodiments, the weaving further includes the steps of smelting, cleaning, shaping, and slitting and winding.

[0030] In the present invention, the above-mentioned steps of yarn arrangement, smelting, cleaning and shaping, and slitting and winding are all conventional steps in the art, and the present invention does not impose any special limitation thereto.

[0031] In a third aspect, the present invention provides a use of the flexible knitted peelable fabric as described in the first aspect in an autoclave molding process for composite materials.

[0032] When laying the material in the autoclave molding process of the composite material, if both surface layers of the flexible knitted peelable cloth contain PTFE fiber filaments, then any one surface can be close to the prepreg; if only one of the two surfaces of the flexible knitted peelable cloth contains PTFE fiber filaments, then the side containing the PTFE fiber filaments needs to be close to the prepreg.

[0033] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The flexible knitted peelable cloth provided by the present invention comprises two surface layers and a spacer layer arranged between the two surface layers, the yarn of the spacer layer penetrates and is connected between the two surface layers to form a three-dimensional spacer layer, and the yarn of at least one of the surface layers comprises PTFE fiber filaments; through the above-mentioned structural design and the limitation of the yarn types, the obtained flexible knitted peelable cloth has both excellent peelability and gas conductivity, and in the composite material autoclave molding process, the release property of conventional peelable cloth and the conductivity function of breathable felt can be integrated, which not only improves the peeling performance, but also solves the problem of fiber scraps of conventional needle-punched breathable felt falling off and causing pollution to composite material parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A schematic diagram of the cross-sectional structure of the flexible knitted peelable fabric provided by the present invention;

[0037] Figure 2 A schematic diagram of the organizational structure of the flexible knitted peelable fabric provided by the present invention;

[0038] Among them, 1-surface layer, 2-interval layer. DETAILED DESCRIPTION

[0039] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0040] Unless otherwise specified, the raw materials involved in the following examples and comparative examples are conventional materials in the art and can be purchased from commercial products.

[0041] Example 1

[0042] A flexible knitted peelable fabric with a thickness of 0.4 mm, and a schematic diagram of its cross-sectional structure is shown as follows: Figure 1As shown, it comprises two surface layers 1 and a spacer layer 2 arranged between the two surface layers 1;

[0043] The yarns of the two surface layers 1 are both PTFE fiber filaments (linear density of 300D, breaking strength of 4.5 cN / dtex, dry heat shrinkage (@250°C×30min) of 3.0%);

[0044] The yarn of the spacer layer 2 is polyester fiber (line density is 150D), and the polyester fiber is connected through the two surface layers 1 to form a three-dimensional spacer layer 2;

[0045] The preparation method of the flexible knitted peelable fabric provided in this embodiment includes: after arranging the yarn, using a double-sided circular knitting machine with a machine gauge of 32G and a yarn supply number of 72 to weave, using double rib needle arrangement, the specific organizational structure diagram is as follows Figure 2 As shown: every 6 routes form a basic structure, the 3F and 6F cylinder needles work to form a surface layer, the 2F and 5F dial needles work to form another surface layer, the 1F and 4F dial needles and cylinder needles work at the same time to connect the two surface layers to form a spacer layer, and after weaving is completed, it is smelted, cleaned, shaped, and slit and rolled to obtain the flexible knitted peelable fabric.

[0046] Example 2

[0047] A flexible knitted peelable fabric with a thickness of 0.3 mm, having the same structure as that of Example 1, including two surface layers and a spacer layer disposed between the two surface layers;

[0048] Among them, the yarn of one surface layer is PTFE fiber filament (linear density of 300D, breaking strength of 4.2cN / dtex, dry heat shrinkage (@250℃×30min) of 4.0%), and the yarn of the other surface layer is polyamide 6 fiber (linear density of 150D);

[0049] The yarn of the spacer layer is polyamide 6 fiber (linear density is 150D), and the polyamide 6 fiber is connected through the two surface layers to form a three-dimensional spacer layer;

[0050] The preparation method of the flexible knitted peelable fabric provided in this embodiment includes: after arranging the yarn, using a double-sided circular knitting machine with a machine number of 32G and a yarn supply number of 72 to weave, using double rib needle arrangement, every 6 routes form a basic structure, the 3F and 6F cylinder needles work to form a surface layer, the 2F and 5F needle dial needles work to form another surface layer, the 1F and 4F needle dial needles and cylinder needles work at the same time to connect the two surface layers to form a spacer layer, and after weaving is completed, it is smelted, cleaned, shaped, and slit and rolled to obtain the flexible knitted peelable fabric.

[0051] Example 3

[0052] A flexible knitted peelable fabric with a thickness of 0.5 mm, having the same structure as that of Example 1, including two surface layers and a spacer layer disposed between the two surface layers;

[0053] Among them, the yarn of one surface layer is PTFE fiber filament (linear density of 300D, breaking strength of 4.0cN / dtex, dry heat shrinkage (@250℃×30min) of 4.5%), and the yarn of the other surface layer is polyamide 66 fiber (linear density of 150D);

[0054] The yarn of the spacer layer is polyamide 66 fiber (linear density is 150D), and the polyamide 66 fiber is connected through the two surface layers to form a three-dimensional spacer layer;

[0055] The preparation method of the flexible knitted peelable fabric provided in this embodiment includes: after arranging the yarn, using a double-sided circular knitting machine with a machine number of 32G and a yarn supply number of 72 to weave, using double rib needle arrangement, every 6 routes form a basic structure, the 3F and 6F cylinder needles work to form a surface layer, the 2F and 5F needle dial needles work to form another surface layer, the 1F and 4F needle dial needles and cylinder needles work at the same time to connect the two surface layers to form a spacer layer, and after weaving is completed, it is smelted, cleaned, shaped, and slit and rolled to obtain the flexible knitted peelable fabric.

[0056] Comparative Example 1

[0057] A peelable cloth, which differs from Example 1 in that polyester fibers with a linear density of 300D are used to replace PTFE fiber filaments with a linear density of 300D, and other materials, structures and preparation methods are the same as those in Example 1.

[0058] Performance Testing:

[0059] (1) Peel force: Tested according to the method provided in GB / T 2792.

[0060] (2) Air permeability: Tested according to the method provided in GB / T 5453.

[0061] The flexible knitted peelable fabrics provided in Examples 1 to 3 and Comparative Example 1 were tested according to the above test method. The test results are shown in Table 1:

[0062] Table 1

[0063] Peel force (N / 50mm) Air permeability (mm / s) Example 1 13.0 3200 Example 2 15.5 2600 Example 3 16.0 2800 Comparative Example 1 34.0 2400

[0064] From the data in Table 1, we can see that:

[0065] The flexible knitted peelable fabrics provided in Examples 1 to 3 have a peeling force of only 13.0 to 16.0 N / 50 mm and an air permeability of up to 2600 to 3200 mm / s, and have both excellent peelability and air permeability.

[0066] Compared with Example 1, the peelable cloth provided in Comparative Example 1 has a higher peeling force and a lower air permeability, and both the air permeability and peelability are poor.

[0067] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A flexible knitted peelable fabric, characterized in that: The flexible knitted peelable fabric comprises two surface layers and a spacer layer arranged between the two surface layers, wherein the yarn of the spacer layer penetrates and connects between the two surface layers to form a three-dimensional spacer layer; And the yarn of at least one of the surface layers includes PTFE fiber filaments.

2. The flexible knitted peelable fabric according to claim 1, characterized in that: The thickness of the flexible knitted peelable cloth is 0.3-0.5 mm.

3. The flexible knitted peelable fabric according to claim 1 or 2, characterized in that: The PTFE fiber filament is a monofilament, and the linear density is 180-400D.

4. The flexible knitted peelable fabric according to any one of claims 1 to 3, characterized in that: The yarns of the two surface layers both include PTFE fiber filaments; And / or, the yarn of one of the surface layers is PTFE fiber filament, and the yarn of the other surface layer is any one of polyester fiber, polyamide 6 fiber or polyamide 66 fiber, or a combination of at least two of them.

5. The flexible knitted peelable fabric according to any one of claims 1 to 4, characterized in that: The yarn of the spacer layer comprises any one of polyester fiber, polyamide 6 fiber or polyamide 66 fiber or a combination of at least two thereof; Preferably, the linear density of the yarn of the spacer layer is 100-200D.

6. A method for preparing the flexible knitted peelable fabric according to any one of claims 1 to 5, characterized in that: The preparation method comprises: using a double-sided circular knitting machine for weaving to obtain the flexible knitted peelable fabric.

7. The preparation method according to claim 6, characterized in that: The weaving method comprises: on a double-sided circular knitting machine, double rib needles are used to form a basic structure every 6 routes, the 3F and 6F cylinder needles work to form a surface layer, the 2F and 5F dial needles work to form another surface layer, the 1F and 4F dial needles and cylinder needles work simultaneously to connect the two surface layers to form a spacer layer, and the weaving is completed to obtain the flexible knitted peelable cloth.

8. The preparation method according to claim 6 or 7, characterized in that: The method also includes a yarn arrangement step before the weaving.

9. The preparation method according to any one of claims 6 to 8, characterized in that: After the weaving, the steps of smelting, cleaning, shaping and slitting and winding are also included.

10. Use of the flexible knitted peelable fabric according to any one of claims 1 to 5 in an autoclave molding process for composite materials.

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