Preparation method of polypropylene self-reinforced composite material

Abstract

The invention relates to the technical field of production of fiber-reinforced thermoplastic composite prepreg and composite laminated plates thereof, in particular to a production method of high-strength polypropylene fiber-reinforced polypropylene resin unidirectional prepreg and a composite material. The method mainly comprises the following steps: straightly and tightly arranging and unfolding a certain number of polypropylene fibers, extruding a casting film from polypropylene resin through a screw, laminating and infiltrating the polypropylene resin and the polypropylene fibers, and pressing and coiling through a cold pressing roller to prepare the unidirectional belt. The one-way prepreg of the polypropylene self-reinforced composite material is paved according to a certain paving direction and thickness and then is subjected to hot pressing to prepare a polypropylene self-reinforced composite material laminated plate with a certain size and thickness. Or slitting the polypropylene self-reinforced composite material unidirectional prepreg, weaving the slit unidirectional prepreg with relatively narrow width, cutting and paving according to a certain size, or mixing and paving with a single-line prepreg tape, and performing hot pressing to form the polypropylene composite material laminated plate.

Description

Technical Field

[0001] The invention relates to the technical field of composite material production, in particular to a polypropylene self-reinforced composite material unidirectional prepreg and a production method of the composite material. Background Art

[0002] Fiber-reinforced thermoplastic composite materials have high comprehensive performance and high molding efficiency. They are widely used in automotive structural parts, automotive interior and exterior decoration, sporting goods, luggage and other fields. Prepreg plays a vital bridging role as an intermediate material between fiber and thermoplastic resin raw materials and fiber-reinforced thermoplastic material sheets or parts. At present, the main methods for preparing thermoplastic composite prepregs are solution impregnation and melt impregnation. However, the solvent recovery and treatment of the solution impregnation method is very troublesome, the cost is high, and it is impossible to achieve complete recovery, which will cause great pollution to the environment; the melt impregnation method has high production efficiency and is clean and environmentally friendly. However, the surface of polypropylene fiber is inert, and the melting point is close to that of polypropylene resin. The melt impregnation method makes it difficult to composite the fiber and resin, and the interface bonding between the fiber and the resin is poor. The porosity is large and the molding quality is unstable.

[0003] The unidirectional prepreg of polypropylene self-reinforced composite material is a fiber-reinforced thermoplastic prepreg in a single direction prepared by compounding polypropylene fiber and polypropylene cast film. The unidirectional prepreg can be cut to stack multiple layers of unidirectional prepreg in the same direction or different directions layer by layer on a polypropylene self-reinforced composite material with a certain thickness and a certain ply angle after hot pressing. As an intermediate product of composite materials, the production and preparation of unidirectional prepreg of polypropylene self-reinforced composite material is very important. At present, there are two main processes for polypropylene self-reinforced composite materials: one is to weave polypropylene fiber into fabric, cross-stack it with another polypropylene film, melt the film by hot pressing to complete the impregnation of polypropylene fiber, and then cool it to form a polypropylene self-reinforced composite material. The fiber fabric weaving cost involved here is high, and the multiple melting of polypropylene resin brings energy waste, high cost, and great difficulty in compounding, high porosity, and unstable performance. Another process is to melt and extrude two different polypropylene resins together to form a three-layer film cut into flat wire, or a round core and outer skin, and then weave it into a fabric and perform multi-layer hot pressing compounding. In the compounding process, bonding and compounding are achieved by melting the epidermis. The polypropylene self-reinforced composite material obtained by this method has high performance, but the equipment investment is huge and the manufacturing cost is high. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a polypropylene fiber self-reinforced composite material unidirectional prepreg and a composite material thereof with low porosity, high strength and excellent comprehensive mechanical properties.

[0005] Another object of the present invention is to provide a high-strength polypropylene self-reinforced composite unidirectional prepreg and a preparation method of the composite material thereof which is low in cost, high in efficiency and can be industrially produced.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: to provide a method for preparing a polypropylene self-reinforced composite material, comprising the following steps:

[0007] 1) The polypropylene fiber is drawn out from the creel, enters the pre-drawing roller, and then enters the traction device to be flattened, so that each bundle of polypropylene fiber is fully unfolded, and the fibers are straightened and neatly arranged under the traction action;

[0008] Preferably, the strength of a single bundle of polypropylene fibers is 4-10 g / D (grams per denier), and the width of the fiber bundle is different according to the denier of the yarn, and the width of the single bundle of polypropylene fibers is 0.2 mm-6 mm. The width of a single prepreg of a polypropylene self-reinforced composite material is generally 300-1500 mm, and the number of fiber barrels on the corresponding creel is generally 50-1000 barrels.

[0009] 2) The polypropylene resin is formed into a cast film through a screw extruder, and then coated onto the densely arranged polypropylene fibers. The fibers and the molten resin film are repeatedly combined by a pressing roller, and then cooled and shaped to obtain a polypropylene self-reinforced composite material unidirectional prepreg;

[0010] 3) cutting the shaped polypropylene self-reinforced composite material unidirectional prepreg to form a flat-wire-shaped unidirectional prepreg with a smaller width, and then weaving the flat-wire-shaped polypropylene unidirectional prepreg into a fabric;

[0011] 4) The fabric in step 3) can be made into materials according to a certain size and direction, and multiple layers are stacked together and then hot-pressed to obtain the polypropylene self-reinforced fiber composite material; or the polypropylene self-reinforced composite material unidirectional prepreg described in step 2) is cut, stacked in multiple directions and at multiple angles, and then hot-pressed to obtain the polypropylene self-reinforced composite material.

[0012] Preferably, in step 1), the polypropylene fiber is drawn from the fiber creel at a drawing speed of 2-15 m / min and a pressure of the pre-drawing roller of 2-3 MPa.

[0013] Preferably, in step 2), the polypropylene resin is cast onto the straightly arranged polypropylene fibers through a screw extruder, and the cast film and the fibers together form a three-layer structure of polypropylene cast film / polypropylene fiber / polypropylene cast film, the resin content is 40%-60%, the pulling speed is 2-15m / min, and the resin extrusion temperature is 220℃-260℃.

[0014] In step 3), the high-strength polypropylene self-reinforced composite material is cut into flat wires by polypropylene unidirectional tapes, and the flat wires are woven into fabrics. The width of the flat wires is 0.2-20 mm, the thickness is 0.1 mm-0.5 mm, and the fabrics are plain, twill and satin.

[0015] In step 4), the polypropylene self-reinforced composite unidirectional prepreg is mixed and layered in the directions and order of 0°, 45°, 30°, 60° and 90°, and then hot-pressed, and the layering angles are preferably 0°, -45°, 45° and 90°.

[0016] Preferably, in step 4), the hot pressing molding temperature is 170° C.-200° C., the hot pressing time is 5 min-10 min, and the pressure is 1 MPa-5 MPa.

[0017] In the prior art, in the preparation of polypropylene self-reinforced composite materials, one method is to alternately lay polypropylene fiber fabrics and polypropylene resin films and then directly perform compression molding, but this method has unstable molding quality, low production efficiency and high production cost. Another method is to simultaneously melt and extrude two different polypropylene films, cut them into narrow strips or directly stretch them into filaments after stretching, one polypropylene is used as the internal core layer, and the other polypropylene is used as the surface skin layer. This method has high requirements on equipment and technology, large investment and high cost.

[0018] The polypropylene self-reinforced composite material unidirectional prepreg is formed by online impregnation of the unidirectional prepreg of the present application, and then multiple layers are stacked at different angles and hot-pressed for composite molding, or the unidirectional prepreg tape of the polypropylene self-reinforced composite material obtained by the present application is cut and then woven to form a woven fabric, which is mixed or hot-pressed separately. The polypropylene self-reinforced composite material laminate has stronger designability, high production efficiency and lower production cost. Since the fibers in the unidirectional prepreg are straight, the resin is more evenly distributed, there are fewer defects such as bubbles and pores, and the performance of the polypropylene self-reinforced composite material is higher.

[0019] The advantages of the present invention are: the production method of polypropylene fiber self-reinforced unidirectional prepreg and composite material can greatly save production and investment costs, improve production efficiency, and improve product quality compared with the existing method. The two-way composite of polypropylene fiber and polypropylene cast film makes it easier for the resin to impregnate the fiber, the resin distribution is more uniform, there are fewer defects such as bubbles and pores, and the interface bonding force of the prepared prepreg is improved. The porosity is reduced by more than 25%, and the tensile strength of the prepared composite material is increased by more than 50%. In addition, during the production process, no environmental pollution is caused, and the products produced can also be recycled and reused to avoid waste. The whole process is green and pollution-free.

[0020] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The present invention is a polypropylene self-reinforced composite material unidirectional prepreg and a composite material production process thereof DETAILED DESCRIPTION

[0022] Refer to the attached Figure 1 , the present invention will be further described below in conjunction with embodiments.

[0023] like Figure 1 As shown, the production process system of high-strength polypropylene fiber self-reinforced unidirectional prepreg and its composite materials includes: 1 polypropylene fiber creel, 2 screw extruder, 3 cast polypropylene molten film, 4 polypropylene fiber and resin molten film pressing roller, 5 polypropylene self-reinforced composite material unidirectional prepreg winding, 6 polypropylene self-reinforced composite material laminate composite hot press, 7 polypropylene self-reinforced composite material prepreg tape slitting narrow tape, 8 polypropylene self-reinforced composite material prepreg tape slitting narrow tape braid, 9 polypropylene self-reinforced composite material unidirectional prepreg tape or slitting narrow tape braid stacked in a certain direction and thickness.

[0024] In the embodiment, the polypropylene fiber is PPH-T03 drawing grade polypropylene produced by Sinopec; the polypropylene resin is F500EPS produced by Sinopec.

[0025] Example 1

[0026] A polypropylene fiber self-reinforced composite unidirectional laminate is prepared according to the following method:

[0027] 1. The polypropylene fiber is drawn out from the creel 1, enters the pre-drawing roller (with a pressure of 0.3 MPa), and then enters the traction device for flattening, so that each bundle of polypropylene fibers is fully unfolded, and the fibers are straightened and neatly arranged under the traction action; 500 barrels of polypropylene fiber yarn, the width of a single bundle of yarn is 1 mm, and the total width of all fibers after widening is 1000 mm, the polypropylene resin is melted and plasticized by the screw extruder 2, and extruded from the head through a slit die (resin extrusion temperature 240°C), and the molten polypropylene film is coated on the surface of the polypropylene fiber, and then pressed by the pressing roller 4, and after cooling, it is wound by the winding roller 5, and the traction speed is 5 m / min. The final polypropylene self-reinforced composite material unidirectional prepreg (a three-layer structure of polypropylene cast film / polypropylene fiber / polypropylene cast film, with a resin content of 50%) has a width of 1 m and a thickness of 0.2 mm.

[0028] 2. Cutting and laying: The prepared polypropylene self-reinforced composite unidirectional prepreg is cut into single-layer sheets with a length and width of 300 mm×300 mm, and 10 single-layer sheets of the same size are laid in the same direction of the fiber direction.

[0029] 3. Hot pressing: The stacked prepreg tapes are transferred to a hot press for hot pressing. The hot pressing temperature is 180°C, the pressure is maintained for 5 minutes, and the pressure is 3MPa. The surface polypropylene resin is melted to bond the layers together. Finally, the product is cooled and shaped to complete the preparation of the polypropylene self-reinforced composite unidirectional board. The density of the prepared polypropylene self-reinforced composite board is 0.91g / cm 3 The tensile strength along the fiber direction is 336 MPa, which is much higher than the tensile strength of 115 MPa of polypropylene self-reinforced composites prepared with polypropylene fiber fabrics and polypropylene films (Yeon-Taek Hwang, etc. The influence of consolidation temperature on in-plane and interlaminar mechanical properties of self-reinforced polypropylene composite, Composite Structures, 2019, 210: 767-777).

[0030] Example 2

[0031] A polypropylene self-reinforced composite material plate is prepared according to the following method:

[0032] 1. The polypropylene fiber is drawn out from the creel 1, enters the pre-drawing roller (with a pressure of 0.3 MPa), and then enters the traction device for flattening, so that each bundle of polypropylene fibers is fully unfolded, and the fibers are straightened and neatly arranged under the traction action; 500 barrels of polypropylene fiber yarn, the width of a single bundle of yarn is 1 mm, and the total width of all fibers after widening is 1000 mm, the polypropylene resin is melted and plasticized by the screw extruder 2, and extruded from the head through a slit die, and the molten polypropylene film is coated on the surface of the polypropylene fiber, and then pressed by the pressing roller 4, and after cooling, it is wound by the winding roller 5, and the traction speed is 5 m / min. The final polypropylene self-reinforced composite material unidirectional prepreg (a three-layer structure of polypropylene cast film / polypropylene fiber / polypropylene cast film, with a resin content of 50%) has a width of 1 m and a thickness of 0.2 mm.

[0033] 2. Woven fabric: The 1m wide polypropylene self-reinforced composite unidirectional prepreg is cut by a slitting device. The slit narrow strips are similar to flat wires (width 6mm) and thickness 0.2mm. The narrow strips are woven into plain fabrics by weaving equipment.

[0034] 3. Laying: Cut the plain fabric into 300mm x 300mm in length and width and lay out 5 layers.

[0035] 4. Hot pressing: Move the stacked narrow strip fabric to the hot press for hot pressing. The hot pressing temperature is 180℃, the pressure is maintained for 5 minutes, and the pressure is 3MPa. The surface polypropylene resin is melted to bond the layers. Finally, the product is cooled and shaped to complete the preparation of the polypropylene self-reinforced composite material sheet. The density of the prepared polypropylene self-reinforced composite material sheet is 0.92g / cm 3 The tensile strength along the fiber direction is 214 MPa, which exceeds the tensile strength of 115 MPa of polypropylene self-reinforced composite materials prepared by polypropylene fiber fabric and polypropylene film.

[0036] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention shall be equivalent replacement modes and shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a polypropylene self-reinforced composite material, comprising the following steps: 1) The polypropylene fiber is drawn out from the creel, enters the pre-drawing roller, and then enters the traction device to be flattened, so that each bundle of polypropylene fiber is fully unfolded, and the fibers are straightened and neatly arranged under the traction action; 2) The polypropylene resin is formed into a cast film through a screw extruder, and then coated onto the densely arranged polypropylene fibers. The fibers and the molten resin film are repeatedly combined by a pressing roller, and then cooled and shaped to obtain a polypropylene self-reinforced composite material unidirectional prepreg; 3) cutting the shaped polypropylene self-reinforced composite material unidirectional prepreg to form a flat-wire-shaped unidirectional prepreg with a smaller width, and then weaving the flat-wire-shaped polypropylene unidirectional prepreg into a fabric; 4) The fabric in step 3) can be made into materials in a certain size and direction, and multiple layers are stacked together and then hot-pressed to obtain the polypropylene self-reinforced fiber composite material; Alternatively, the polypropylene self-reinforced composite material unidirectional prepreg described in step 2) is cut, stacked in multiple directions and at multiple angles, and then hot-pressed to obtain the polypropylene self-reinforced composite material.

2. The method according to claim 1, in step 1), the polypropylene fiber is drawn from the fiber creel, the drawing speed is 2-15 m / min, and the pressure of the pre-drawing roller is 2-3 MPa.

3. The method according to claim 1, in step 2), the polypropylene resin is cast onto the straightly arranged polypropylene fibers through a screw extruder, and the cast film and the fibers together form a three-layer structure of polypropylene cast film / polypropylene fiber / polypropylene cast film, the resin content is 40%-60%, the pulling speed is 2-15m / min, and the resin extrusion temperature is 220℃-260℃.

4. The method according to claim 1, in step 3), the high-strength polypropylene self-reinforced composite material is made by cutting polypropylene unidirectional tapes into flat wires, weaving the flat wires into fabrics, the width of the flat wires is 0.2-20 mm, the thickness is 0.1 mm-0.5 mm, and the fabrics are plain, twill and satin.

5. According to the method of claim 1, in step 4), the polypropylene self-reinforced composite material unidirectional prepreg is mixed and layered in the directions and order of 0°, 45°, 30°, 60° and 90°, and then hot-pressed.

6. The method according to claim 1, wherein in step 4), the hot pressing molding temperature is 170°C-200°C, the hot pressing is 5min-10min, and the pressure is 1MPa-5MPa.

7. The method according to claim 1, wherein the specific steps are: The polypropylene fiber is drawn out from the creel 1, enters the pre-drawing roller, and then enters the traction device to be flattened, so that each bundle of polypropylene fibers is fully unfolded, and the fibers are straightened and neatly arranged under the traction action; 500 barrels of polypropylene fiber yarn, the width of a single bundle of yarn is 1mm, and the total width of all fibers after widening is 1000mm, the polypropylene resin is melted and plasticized by the screw extruder 2, and extruded from the head through a slit die, the resin extrusion temperature is 220℃-260℃, the molten polypropylene film is coated on the surface of the polypropylene fiber, and then pressed by the pressing roller 4, after cooling, it is wound by the winding roller 5, the traction speed is 5m / min, and the width of the final polypropylene self-reinforced composite material unidirectional prepreg is 1m, and the thickness is 0.2mm; the polypropylene self-reinforced composite material unidirectional prepreg is a three-layer structure of polypropylene cast film / polypropylene fiber / polypropylene cast film, and the resin content is 40%-60%; Cutting and laying: Cut the prepared polypropylene self-reinforced composite unidirectional prepreg into single-layer sheets with a length and width of 300mm×300mm, and lay 10 single-layer sheets of the same size in the same direction of the fiber direction; Hot pressing: The stacked prepreg tapes are transferred to a hot press for hot pressing at a temperature of 180°C, with a holding pressure of 5 minutes and a pressure of 3MPa; the surface polypropylene resin is melted to bond the layers, and the product is finally cooled and shaped to complete the preparation of the polypropylene self-reinforced composite unidirectional plate. The density of the prepared polypropylene self-reinforced composite plate is 0.91g / cm3, and the tensile strength along the fiber direction is 336MPa.

8. The method according to claim 1, wherein the specific steps are: The polypropylene fiber is drawn out from the creel 1, enters the pre-drawing roller (with a pressure of 0.1-0.5MPa), and then enters the traction device for flattening, so that each bundle of polypropylene fibers is fully unfolded, and the fibers are straightened and neatly arranged under the traction action; 500 barrels of polypropylene fiber yarn, the width of a single bundle of yarn is 1mm, and the total width of all fibers after widening is 1000mm, the polypropylene resin is melted and plasticized by the screw extruder 2, and extruded from the head through a slit die, and the molten polypropylene film is coated on the surface of the polypropylene fiber, and then pressed by the lamination roller 4, and after cooling, it is wound by the winding roller 5, and the traction speed is 5m / min. The width of the polypropylene self-reinforced composite material unidirectional prepreg finally obtained is 1m, and the thickness is 0.2mm; the polypropylene self-reinforced composite material unidirectional prepreg is a three-layer structure of polypropylene cast film / polypropylene fiber / polypropylene cast film, and the resin content is 40%-60%; Woven fabric: 1m wide polypropylene self-reinforced composite unidirectional prepreg is cut by slitting equipment. The cut narrow strips are similar to flat wires with a thickness of 0.2mm. The narrow strips are woven into plain fabrics by weaving equipment. Cut the plain fabric into 300mm x 300mm in length and width, and stack the same 5 layers; Hot pressing: The stacked narrow strip fabric is moved to a hot press for hot pressing. The hot pressing temperature is 180°C, the pressure is maintained for 5 minutes, and the pressure is 3MPa. The surface polypropylene resin is melted to bond the layers. Finally, the product is cooled and shaped to complete the preparation of the polypropylene self-reinforced composite material sheet. The density ρ of the prepared polypropylene self-reinforced composite material sheet is 0.92g / cm 3 , the tensile strength along the fiber direction is 214MPa.

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