CN110054878B

CN110054878B - Elastomer short fiber toughened crystalline polymer product and preparation method thereof

Info

Publication number: CN110054878B
Application number: CN201910344663.8A
Authority: CN
Inventors: 郭建军; 王建业; 张一帆; 李志祥; 孙爱华; 刘丰华; 许高杰
Original assignee: Ningbo Institute of Material Technology and Engineering of CAS
Current assignee: Ningbo Institute of Material Technology and Engineering of CAS
Priority date: 2019-04-26
Filing date: 2019-04-26
Publication date: 2021-07-27
Anticipated expiration: 2039-04-26
Also published as: CN110054878A

Abstract

The invention discloses an elastomer short fiber toughened crystalline polymer product and a preparation method thereof, wherein the preparation method comprises the following steps: thermoplastic elastomer and crystalline resin raw materials are mixed according to the mass percentage of 10-30%: 70-90 percent of the mixture is mixed, melted, blended and granulated by a double-screw extruder, and the blended granules are obtained after drying; the difference between the melting temperature of the thermoplastic elastomer and the melting temperature of the crystalline resin raw material is 10-20 ℃; adding the obtained blended granules into a single-screw extruder for melt extrusion, and performing primary stretching and three-section water tank cooling treatment on the extruded materials to obtain a 3D printing wire material; and placing the obtained 3D printing wire material in a fused deposition modeling 3D printer, stretching the melt for the second time and the third time in the printing process, overlapping the melt on a forming platform to form a three-dimensional structure, and cooling to obtain an elastomer short fiber toughening crystalline polymer product. The invention has the characteristics of simple equipment, easy control of processing technology, capability of forming complex geometric structures and the like.

Description

Elastomer short fiber toughened crystalline polymer product and preparation method thereof

Technical Field

The invention relates to the technical field of high molecular polymer 3D printing consumables, in particular to an elastomer short fiber toughened crystalline polymer product and a preparation method thereof.

Background

Microfiber Composites (MFCs) is a composite material that is favored by researchers, a concept that was introduced by the scientists Evstatiev and Fakirov in 1992. It can effectively improve the compatibility and mechanical property of an immiscible blending system. MFCs have the potential to be lightweight, easy to process, recyclable, and the like, relative to conventional polymer blends and composites. The preparation of MFCs is mainly divided into three steps: firstly, melt blending, secondly, extrusion-drawing with a single or twin screw, and finally, post-processing by die pressing or injection molding.

Fiber-reinforced composites can be classified as either continuous or discontinuous, depending on the length of the fibers. Due to the significant difference in structure between continuous and discontinuous fibers, it is expected that continuous or discontinuous fiber reinforced composites will have significantly different mechanical properties. From a macroscopic point of view, one would expect the continuous fiber reinforced composite to have a higher stiffness than the discontinuous fibers because the presence of stress points similar to grooves at the ends of the discontinuous fibers around the matrix can cause stress concentrations. Therefore, when the stress level is equivalent to the fracture strength of the matrix, cracks are generated. However, at the same polymer fiber content, the number of discontinuous fibers is significantly higher than the continuous fibers, and the plurality of discontinuous fibers acts to stop any cracks originating in the bulk matrix as the crack tips attempt to propagate toward the fibers. When one fiber breaks, the other staple can minimize stress concentrations in the matrix. In fact, in discontinuous fibre-reinforced composites, if one fibre breaks, there is little effect on the whole, since the crack tip always encounters a fibre that may prevent the crack from propagating. Therefore, cracks can be prevented from propagating on the cross section of the composite material, and the discontinuous fibers can enhance the mechanical properties of the composite material.

Polylactic acid has excellent mechanical strength, however, its impact strength is low, limiting its wide use. In order to overcome this drawback, many scientists have studied the modification method of the toughened polylactic acid. The method can be mainly divided into chemical modification and physical modification, and the chemical method comprises the following steps: copolymerization, grafting, crosslinking, and the like; the physical method mainly comprises the following steps: filling, blending, reinforcing, and the like. Among these methods, melt blending of toughened polylactic acid by elastomeric thermoplastic polyurethanes has been widely studied. However, under the traditional processing conditions, the dispersed phase polyurethane is distributed in a spherical or ellipsoidal shape, so that the impact strength of the polylactic acid can be obviously improved. However, the improvement in the impact strength of polylactic acid is accompanied by a large decrease in the tensile strength. Because, the properties of a polymer blend composite are not only dependent on the physical properties of its constituent components, but are also highly dependent on the dispersed phase morphology. Therefore, controlling the phase morphology of such biocompatible thermoplastic polyurethanes is of great scientific interest.

Many researches show that the melting temperatures of two polymers are required to be different by 30-40 ℃ for the preparation of the microfiber composite material, otherwise, the fiber phase is damaged during post-processing forming. As a new method of processing and forming, the fused deposition technology can effectively overcome the limitation, realize the fiber forming distribution of the polymer with smaller melting temperature difference in the product and realize the forming of a complex geometric structure.

Disclosure of Invention

Aiming at the defects in the field, the invention provides a preparation method of an elastomer short fiber toughened crystalline polymer product, aiming at overcoming the limitation of the traditional in-situ fiber composite material preparation technology, and the preparation method has the characteristics of simple equipment, easily controlled processing technology, capability of forming a complex geometric structure and the like.

A method of preparing an elastomeric staple fiber toughened crystalline polymer product comprising:

(1) thermoplastic elastomer and crystalline resin raw materials are mixed according to the mass percentage of 10-30%: 70-90 percent of the mixture is mixed, melted, blended and granulated by a double-screw extruder, and the blended granules are obtained after drying; the difference between the melting temperature of the thermoplastic elastomer and the melting temperature of the crystalline resin raw material is 10-20 ℃;

(2) adding the obtained blended granules into a single-screw extruder for melt extrusion, and performing primary stretching and cooling treatment on the extruded material to obtain a 3D printing wire material;

(3) and placing the obtained 3D printing wire material in a fused deposition modeling 3D printer, stretching the melt for the second time and the third time in the printing process, overlapping the melt on a forming platform to form a three-dimensional structure, and cooling to obtain an elastomer short fiber toughening crystalline polymer product.

In the step (1), the thermoplastic elastomer is an elastomer fiber-forming phase, and the crystalline resin raw material is a crystalline matrix phase.

Preferably, the thermoplastic elastomer and the crystalline resin raw material are dried before mixing to remove the influence of moisture on the mixing effect.

The melting temperature of the thermoplastic elastomer is 150-190 ℃. Preferably, the melting temperature of the thermoplastic elastomer is 160-170 ℃, which is beneficial for the thermoplastic elastomer to form a fiber structure in the matrix.

The melting temperature of the crystalline resin raw material is 160-210 ℃. Preferably, the melting temperature of the crystalline resin raw material is 170-180 ℃, which is beneficial to fused deposition processing and molding.

Preferably, the thermoplastic elastomer is Thermoplastic Polyurethane (TPU), and the crystalline resin material is polylactic acid (PLA). The two polymers are semi-compatible, and are beneficial to the interaction between TPU and PLA for fiber forming.

The double-screw rotating speed of the double-screw extruder for melt blending granulation is 160-180 r/min, the blending temperature is controlled to be 170-200 ℃, and the two components can be fully melted and mixed under the condition, so that the uniform distribution of fibers formed in the later period is facilitated.

The diameter of the blending granules is 1.3-2.5 mm, the length of the blending granules is 5-7 mm, and the blending granules can be uniformly fed and discharged in a single-screw extruder conveniently.

Preferably, in the step (2), the cooling treatment is three-stage water tank cooling treatment, the temperature of the cooling water in the first stage water tank is at least 55 ℃, the temperature of the cooling water in the second stage water tank is 40-50 ℃, and the temperature of the cooling water in the third stage water tank is room temperature. The 3D printing wire material obtained under the condition has smooth surface and higher roundness, and is beneficial to later-stage printing and forming.

In the step (2), the rotating speed of the screw rod of the single-screw extruder during melt extrusion is 6-10 r/min, the extrusion temperature is 175-190 ℃, the diameter of the 3D printing wire material can be effectively controlled under the condition, and the improvement of the precision and the mechanical strength of the printed product is facilitated.

Preferably, the single screw extruder is melt extruded at a draw ratio of at least 4.28, which facilitates fiber formation of the thermoplastic elastomer in the crystalline resin base polymer matrix.

Preferably, the diameter of 3D printing silk material is 1.7 ~ 1.8mm, is favorable to the even ejection of compact of printing nozzle, can effectively improve and print product quality.

In the step (3), preferably, the melt extrusion stretching ratio of the fused deposition modeling 3D printer is 25-30, so that the elastic fiber can be prevented from shrinking and deforming, the elastic fiber can be kept in a stretching state continuously, the elastic fiber can form short fibers, and the toughness of a printed product can be improved.

The fused deposition modeling 3D printer has the printing temperature of 180-230 ℃, the printing speed of 20-70 mm/s and the printing angle of 20-80 degrees. Preferably, the printing temperature of the fused deposition modeling 3D printer is 190-210 ℃, the printing speed is 30-60 mm/s, the printing angle is 40-50 degrees, uniform distribution and solidification of elastomer fibers are facilitated, and the defects of printed products are reduced.

The invention also provides an elastomer short fiber toughened crystalline polymer product prepared by the preparation method of the elastomer short fiber toughened crystalline polymer product.

Compared with the prior art, the invention has the main advantages that:

(1) the melt drawing is fully utilized to realize the short fiber distribution of the elastomer in a crystalline resin matrix with similar melting temperature.

(2) The preparation method of the elastomer short fiber toughened crystalline polymer product is realized through fused deposition molding in a 3D printing technology.

Drawings

FIG. 1 is a schematic flow chart of the preparation of 3D printing consumables by melt blending, extrusion and stretching of the elastomer polyurethane and the crystalline polylactic acid according to the present invention;

FIG. 2 is a scanning electron microscope photograph of a 3D printing standard sample of the TPU fiber toughened polylactic acid prepared in example 1;

FIG. 3 is a scanning electron microscope photograph of the injection molded sample of the elastomer polyurethane and crystalline polylactic acid composite prepared in comparative example 1.

Detailed Description

The invention is further described with reference to the following drawings and specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. The experimental procedures, in which specific conditions are not noted in the following examples, are generally carried out under conventional conditions or conditions recommended by the manufacturers.

The following example shows a flow of preparing a 3D printing consumable by melt blending an elastomeric polyurethane and a crystalline polylactic acid and extrusion-stretching as shown in fig. 1, and includes:

(1) mixing TPU and PLA, and then melting and blending in a double-screw extruder to obtain a PLA/TPU compound;

(2) and extruding the PLA/TPU compound in a single-screw extruder to obtain a wire (Filament), namely the 3D printing consumable.

Example 1

(1) And putting the elastomer polyurethane resin into a vacuum oven at 80 ℃ for drying for 4h to obtain the dried elastomer polyurethane resin for later use.

(2) And (3) putting the crystalline polylactic resin into a vacuum oven at 80 ℃ for drying for 8h to obtain the dried crystalline polylactic resin for later use.

(3) Weighing the following raw materials in percentage by mass: 10% of the dried elastomer polyurethane resin obtained in the step (1), 90% of the dried crystalline polylactic acid resin obtained in the step (2), and the sum of the mass percentages of the two raw materials is 100%.

(4) And (3) mixing the raw materials weighed in the step (3), and carrying out melt blending granulation by using double screws to obtain composite granules with the diameter of 1.3-2.5 mm and the length of 5-7 mm, placing the composite granules at 80 ℃ for vacuum drying for 12 hours for later use, wherein the rotating speed of the double screws is controlled at 160-180 r/min in the extrusion process, and the blending temperature is controlled at 170-200 ℃.

(5) And (3) extruding the composite granules prepared in the step (4) by using a single-screw extruder, controlling the screw speed in the extrusion process to be 8r/min, controlling the extrusion temperature to be 175-190 ℃, setting the traction speed to be 9m/min, continuously and uniformly extruding the composite, cooling the extruded filaments by three sections of water tanks at the temperatures of 55 ℃, 40 ℃ and 25 ℃, controlling the diameters of consumables to be 1.75 +/-0.03 mm, and collecting the consumables by a winding machine to obtain the filaments, namely the 3D printing consumables of the elastomer polyurethane and crystalline polylactic acid composite.

(6) And (3) printing the 3D printing consumable material of the elastomer polyurethane fiber and crystalline polylactic acid composite material prepared in the step (5) by using a HUEWAY 3D-304FDM printer, and preparing a mechanical strength test standard sample with the tensile ratio of 27. The molded sample was printed at a printing temperature of 205 deg.C, a printing speed of 50mm/s, and a printing angle of + -45 deg.C. The distribution morphology of the elastomer polyurethane in the crystalline polylactic acid is shown in fig. 2, and the elastomer polyurethane is distributed in a fiber shape in the matrix and is oriented along the printing direction. The impact properties of the printed samples were tested according to the ISO14125 impact strength test standard and the data are shown in Table 1.

Example 2

(3) Weighing the following raw materials in percentage by mass: 20% of the dried elastomer polyurethane resin obtained in the step (1), 80% of the dried crystalline polylactic acid resin obtained in the step (2), and the sum of the mass percentages of the two raw materials is 100%.

(6) And (3) printing the 3D printing consumable material of the elastomer polyurethane fiber and crystalline polylactic acid composite material prepared in the step (5) by using a HUEWAY 3D-304FDM printer, and preparing a mechanical strength test standard sample with the tensile ratio of 27. The molded sample was printed at a printing temperature of 205 deg.C, a printing speed of 50mm/s, and a printing angle of + -45 deg.C. The impact properties of the printed samples were tested according to the ISO14125 impact strength test standard and the data are shown in Table 1.

Example 3

(3) Weighing the following raw materials in percentage by mass: 30% of the dried elastomer polyurethane resin obtained in the step (1), 70% of the dried crystalline polylactic acid resin obtained in the step (2), and the sum of the mass percentages of the two raw materials is 100%.

Comparative example 1

(6) And (4) granulating the 3D printing supplies obtained in the step (5) by using a granulator at the rotating speed of 30 r/min. And (3) performing injection molding on the prepared composite granules by using an injection molding machine, controlling the injection molding temperature to be 190 ℃, setting the injection pressure to be 15MPa, controlling the mold temperature to be 55 ℃, and setting the pressure maintaining time to be 10s, thereby preparing the polylactic acid/elastomer polyurethane composite material standard impact sample. The distribution morphology of the elastomer polyurethane in the crystalline polylactic acid is shown in fig. 3, and the elastomer polyurethane is distributed in the matrix in a spherical structure. The impact properties of the injection molded specimens were tested according to the ISO14125 impact strength test standard and the data are given in Table 1.

Comparative example 2

(6) And (4) granulating the 3D printing supplies obtained in the step (5) by using a granulator at the rotating speed of 30 r/min. And (3) performing injection molding on the prepared composite granules by using an injection molding machine, controlling the injection molding temperature to be 190 ℃, setting the injection pressure to be 15MPa, controlling the mold temperature to be 55 ℃, and setting the pressure maintaining time to be 10s, thereby preparing the polylactic acid/elastomer polyurethane composite material standard impact sample. The impact properties of the injection molded specimens were tested according to the ISO14125 impact strength test standard and the data are given in Table 1.

Comparative example 3

Table 1 impact strength test data

Numbering	Impact Strength (J/m)
		Example 1	31.2
Example 2	73.8
		Example 3	90.3
Comparative example 1	23.5
		Comparative example 2	59.1
Comparative example 3	76.9

As can be seen from table 1, the elastomeric polyurethane short fibers effectively improve the impact strength of the crystalline polylactic acid composite.

Furthermore, it should be understood that various changes and modifications can be made by one skilled in the art after reading the above description of the present invention, and equivalents also fall within the scope of the invention as defined by the appended claims.

Claims

1. A method of preparing an elastomeric staple fiber toughened crystalline polymer product comprising:

(1) thermoplastic elastomer and crystalline resin raw materials are mixed according to the mass percentage of 10-30%: 70-90 percent of the mixture is mixed, melted, blended and granulated by a double-screw extruder, and the blended granules are obtained after drying; the difference between the melting temperature of the thermoplastic elastomer and the melting temperature of the crystalline resin raw material is 10-20 ℃; the thermoplastic elastomer is thermoplastic polyurethane, and the crystalline resin raw material is polylactic acid;

(2) adding the obtained blended granules into a single-screw extruder for melt extrusion, and performing primary stretching and cooling treatment on the extruded material to obtain a 3D printing wire material; the cooling treatment is three-section water tank cooling treatment, the temperature of the first section water tank cooling water is at least 55 ℃, the temperature of the second section water tank cooling water is 40-50 ℃, and the temperature of the third section water tank cooling water is room temperature; the single screw extruder has a melt extrusion draw ratio of at least 4.28;

(3) placing the obtained 3D printing wire material in a fused deposition modeling 3D printer, performing secondary stretching and tertiary stretching on the melt in the printing process, overlapping the melt on a forming platform to form a three-dimensional structure, and cooling to obtain an elastomer short fiber toughening crystalline polymer product; the melt extrusion stretching ratio of the fused deposition modeling 3D printer is 25-30; the fused deposition modeling 3D printer has a printing angle of 40-50 degrees.

2. The method for preparing the product of the elastomer short fiber toughened crystalline polymer as claimed in claim 1, wherein the melting temperature of the thermoplastic elastomer is 150 to 190 ℃ and the melting temperature of the crystalline resin raw material is 160 to 210 ℃.

3. The method for preparing the product of the elastomer short fiber toughened crystalline polymer as claimed in claim 1, wherein the rotation speed of the twin screws for melt blending granulation of the twin screw extruder is 160-180 r/min, and the blending temperature is controlled to be 170-200 ℃.

4. The method for preparing the elastomer short fiber toughened crystalline polymer product according to claim 1, wherein in the step (2), the screw rotation speed of the single screw extruder during melt extrusion is 6-10 r/min, and the extrusion temperature is 175-190 ℃.

5. The method for preparing the product of the elastomer short fiber toughened crystalline polymer according to claim 1, wherein the printing temperature of the fused deposition modeling 3D printer is 180-230 ℃, and the printing speed is 20-70 mm/s.

6. An elastomeric short fiber toughened crystalline polymer product prepared by the preparation method of any one of claims 1 to 5.