阅读说明：本技术 一种流场诱导提高片状银粉/聚合物复合线材导电性的方法 (Method for improving conductivity of flake silver powder/polymer composite wire through flow field induction ) 是由 陈振兴 卿培林 王玺 徐敬尧 刘建 韦修恺 黎成武 陈柳伊 卢东宁 于 2020-11-18 设计创作，主要内容包括：本发明公开了一种流场诱导提高聚合物中片状银粉取向分散的方法,可提高所得片状银粉/聚合物复合线材的导电性能。片状银粉的片层厚度为纳米尺度,片层表面直径则为微米尺度。该法利用热熔挤出时的熔体拖曳力,使片状银粉在平行流场方向取向分散,从而使复合线材中片状银粉沿线材方向取向排列,形成良好的导电通道。本发明基于流场诱导使片状银粉在聚合物中取向分散的方法,所得复合线材在电学性能、光学性能、机械性能和热性能方面具有各向异性,特别适合于提高复合线材的导电性,对电路的常温3D打印具有重要意义。(The invention discloses a method for improving the oriented dispersion of flake silver powder in a polymer by flow field induction, which can improve the conductivity of an obtained flake silver powder/polymer composite wire. The thickness of the sheet layer of the flake silver powder is in a nanometer scale, and the diameter of the surface of the sheet layer is in a micrometer scale. The method utilizes the melt drag force during hot melt extrusion to ensure that the flake silver powder is oriented and dispersed in the direction parallel to the flow field, so that the flake silver powder in the composite wire is oriented and arranged along the wire direction to form a good conductive channel. The method for orienting and dispersing the flake silver powder in the polymer based on the flow field induction has the advantages that the obtained composite wire has anisotropy in electrical property, optical property, mechanical property and thermal property, is particularly suitable for improving the conductivity of the composite wire, and has important significance for normal-temperature 3D printing of a circuit.)

1. A method for improving the conductivity of a flake silver powder/polymer composite wire by flow field induction is characterized by comprising the following steps:

(1) adding the granular polymer and the flaky silver powder into a mixer in sequence according to a certain weight ratio, and uniformly mixing;

(2) adding the mixture of the polymer and the flake silver powder into a double-screw mixing, plasticizing and extruding all-in-one machine;

(3) after the mixture is mixed and plasticized at a certain temperature, the mixture is conveyed to a long-range extrusion head by a screw rod to obtain a composite wire rod compounded by flake silver powder and polymer,

in the long-range extrusion head, the silver flakes are aligned under the action of the melt drag force.

2. The method for improving the conductivity of the flake silver powder/polymer composite wire through flow field induction according to claim 1, wherein the method comprises the following steps: in the step (1), the granular polymer is a thermoplastic polymer such as polyvinyl butyral, saturated polyester, polyurethane, ethylene-vinyl acetate copolymer and the like.

3. The method for improving the conductivity of the flake silver powder/polymer composite wire through flow field induction according to claim 2, wherein the method comprises the following steps: in the step (1), the flake silver powder is silver powder with the diameter far larger than the thickness, the thickness of the lamella is nanoscale, the diameter of the surface of the lamella is micrometer, the diameter-thickness ratio is larger than 10, and the average particle diameter D₅₀Is 3 to 6 microns.

4. The method for improving the conductivity of the flake silver powder/polymer composite wire through flow field induction according to claim 1, wherein the method comprises the following steps: in the step (1), the mass ratio of the flaky silver powder to the polymer is 30: 70-60: 40.

5. The method for improving the conductivity of the flake silver powder/polymer composite wire through flow field induction according to claim 1, wherein the method comprises the following steps: in the step (2), the double-screw mixing, plasticizing and extruding all-in-one machine adopts a long-range extruding head, the inner diameter of the extruding head is 1 mm, and the ratio of the length to the inner diameter of the extruding head is changed within the range of 50-200.

6. The method for improving the conductivity of the flake silver powder/polymer composite wire through flow field induction according to claim 1, wherein the method comprises the following steps: in the step (3), the temperature range is 130-200 ℃.

Technical Field

The invention relates to the fields of composite materials, printing electronics and the like, in particular to a preparation method of a conductive composite wire.

Background

The conductive silver paste has excellent conductivity and moderate price, and is widely applied to printing electronics. However, the conductive silver paste has the problems of flammability and explosiveness, poor storage stability, need of a special baking system, discharge of non-volatile organic compounds and the like. The conductive composite wire is used as a raw material, and a fused deposition technology (FDM) is adopted to directly print a conductive pattern on a substrate, so that the problems caused by conductive silver paste can be avoided. Considering the low temperature resistance of common base materials such as plastics, paper and the like, the polymer is the most suitable bonding material for the composite wire. The composite wire material composed of the polymer and the conductive particles is the key for normal-temperature 3D printing of the conductive pattern, and becomes a hot spot of domestic and foreign research in recent years. The method is limited by the poor wettability of the molten composite material to the base material, and the contradiction between the conductivity and the base material binding force cannot be solved at home and abroad at present. The polymer content is generally not less than 20% by mass under conditions ensuring good substrate bonding, which means that the silver powder content in the composite wire is not more than 80% by mass, at which point the volume resistivity of the composite wire is generally greater than 3X 10^-3Omega cm, far from meeting the conductive requirement.

The thickness of the sheet layer of the flake silver powder is in a nanometer scale, and the surface of the sheet layer is in a micrometer scale. The flake silver powder can form orientation dispersion (surface-to-surface contact) among particles, and the contact area between the flakes is large, so that the flake silver powder is beneficial to improving the conductivity. It is known that the torque generated by the drag of the melt draw is favorable for the dispersion of the orientation of the flakes. However, in the actual hot-melt extrusion process, besides the drag force generated by the stretching of the melt, the flaky powder is also subjected to the acting forces such as viscous resistance, thermal motion force, colloid attraction force, repulsion force and the like. The magnitude and direction of these forces constantly change, affecting the orientation of the flake-like powder and the electrical conductivity of the composite wire. If the drag force is made to be large enough relative to other acting forces in the process of hot-melting and extruding the flake silver powder/polymer composite wire, the flake silver powder can overcome other resisting moments to rotate and orient under the action of torque (figure 1), and the flake silver powder is oriented and dispersed along the direction parallel to the flow direction of a melt, so that a conductive channel parallel to the direction of the composite wire is constructed, which is undoubtedly significant for improving the conductivity of the composite wire.

Disclosure of Invention

Aiming at the poor orientation dispersion of the flake silver powder in the flake silver powder/polymer composite wire, the method for inducing the orientation dispersion of the flake silver powder by the flow field so as to improve the conductivity of the flake silver powder/polymer composite wire is provided.

In order to achieve the purpose, the invention adopts the following technical scheme:

(1) adding the granular polymer and the flaky silver powder into a mixer in sequence according to a certain mass ratio, and uniformly mixing;

(2) adding the mixture of the polymer and the flake silver powder into a double-screw mixing, plasticizing and extruding all-in-one machine;

(3) after the mixture is kneaded and plasticized at a certain temperature, the mixture is conveyed to a long-range extrusion head (figure 2) by a screw, and a composite wire (figure 3) compounded by flake silver powder and polymer is obtained. In the long-range extrusion head, the silver flakes were aligned under the melt drag force (fig. 4).

In the step (1), the granular polymer is a thermoplastic polymer such as polyvinyl butyral, saturated polyester, polyurethane, ethylene-vinyl acetate copolymer and the like.

In the step (1), the plate-like silver powder has a large diameterSilver powder with thickness ratio of more than 10 and average grain diameter D₅₀Is 3 to 6 microns.

In the step (1), the mass ratio of the flaky silver powder to the polymer is 30: 70-60: 40.

In the step (2), the double-screw mixing, plasticizing and extruding all-in-one machine adopts a long-range extruding head, the inner diameter of the extruding head is 1 mm, and the ratio of the length to the inner diameter of the extruding head is changed within the range of 20-100.

In the step (3), the temperature range is 130-200 ℃.

The invention utilizes the flow field to induce the orientation dispersion of the flake silver powder in the composite wire, and has the following advantages and effects:

(1) the conductivity of the conductive composite wire prepared by the invention is obviously improved;

(2) the conductive composite wire prepared by the invention does not introduce other components and impurities;

(3) the conductive composite wire prepared by the invention can be directly used for 3D printing of a circuit (figure 5).

Drawings

Fig. 1 is a schematic diagram of a silver flake turning over.

FIG. 2 is a drawing of an extrusion head design.

Fig. 3 is a photograph of a composite wire.

FIG. 4 is a sectional scanning electron microscope image of the composite wire.

Fig. 5 is a conductive pattern 3D printed on a PET film sheet using a composite wire.

Detailed description of the preferred embodiment 1

(1) 340 g of polyvinyl butyral, 110 g of saturated polyester and the particle size D are added in succession to a mixer₅₀550 g of flake silver powder with the diameter-thickness ratio of 4 microns and more than 10, and uniformly mixing;

(2) adding the uniform mixture of the polymer and the flake silver powder into a double-screw mixing, plasticizing and extruding all-in-one machine;

(3) the mixture was kneaded and plasticized at 177 ℃ for 4 hours, and then conveyed by a screw to a long-stroke extrusion head having a diameter of 1 mm and a length of 30 mm, to obtain a composite wire composed of a silver flake and a polymer. In the long-range extrusion head, the silver flakes are aligned under the action of the melt drag force.

(4) The conductive pattern is printed on the PET membrane by adopting a fused deposition type 3D printer, the extrusion temperature of the 3D printer is 177 ℃, and the temperature of the substrate is 150 ℃.

The characteristics of the flake silver powder/polymer composite wire prepared in this example are: the diameter of the composite wire is 1 mm, and the volume resistivity is 3.4 multiplied by 10^-4Omega cm, can meet the general conductive requirement. The conductive pattern printed on the PET film sheet has a bonding force rating of 0.