阅读说明：本技术 一种纳米粒子协效大分子膨胀阻燃tpu制件的选择性激光烧结成型工艺 (Selective laser sintering forming process of nanoparticle synergistic macromolecular expansion flame-retardant TPU (thermoplastic polyurethane) workpiece ) 是由 吴唯 胡焕波 李健硕 刘冬梅 于 2021-08-02 设计创作，主要内容包括：本发明属于高分子材料技术领域,提供了一种纳米粒子协效大分子膨胀阻燃TPU制件的选择性激光烧结成型工艺。该工艺包括以下步骤：(1)设计出需要SLS成型的产品造型,转化为STL格式；(2)将STL文件利用预处理程序调整模型的尺寸、位置和方向,然后将其分切成许多厚度为0.05mm～0.7mm的截面,导入到SLS成型设备的快速成型系统中；(3)将纳米CaCO-(3)/三嗪膨胀阻燃剂/TPU复合粉体材料送入到供粉缸中；(4)设置成型温度、激光功率、扫描速度、扫描间距、层厚等参数；(5)进行SLS成型；(6)SLS成型的制件随成型缸自然冷却,待冷却完全后取出制件,经粉末喷枪对制件后处理,以去除制件表面残留粉末。该工艺制备的结构件不仅具有良好的力学性能,还具有较好的阻燃性。(The invention belongs to the technical field of high polymer materials, and provides a selective laser sintering forming process of a nanoparticle synergistic macromolecular intumescent flame retardant TPU (thermoplastic polyurethane) workpiece. The process comprises the following steps: (1) design out of needMolding the SLS molded product, and converting into STL format; (2) adjusting the size, position and direction of the model by utilizing the STL file through a preprocessing program, then cutting the STL file into a plurality of sections with the thickness of 0.05 mm-0.7 mm, and introducing the sections into a rapid forming system of SLS forming equipment; (3) mixing nano CaCO 3 The triazine intumescent flame retardant/TPU composite powder material is fed into a powder supply cylinder; (4) setting parameters such as forming temperature, laser power, scanning speed, scanning interval, layer thickness and the like; (5) carrying out SLS forming; (6) and naturally cooling the SLS molded part along with the molding cylinder, taking out the part after the SLS molded part is completely cooled, and carrying out post-treatment on the part by using a powder spray gun to remove residual powder on the surface of the part. The structural member prepared by the process has good mechanical property and good flame retardance.)

1. A selective laser sintering forming process of a nanoparticle synergistic macromolecular intumescent flame retardant TPU workpiece is characterized by comprising the following steps:

(1) building a model of a product requiring SLS molding;

(2) adjusting the size, position and direction of the model by using a pretreatment program, then cutting the model into a plurality of sections with the thickness of 0.05 mm-0.7 mm, and introducing the sections into SLS forming equipment;

(3) mixing nano CaCO₃Feeding the/triazine base intumescent flame retardant/TPU composite powder material into a powder supply cylinder;

(4) setting parameters such as forming temperature, laser power, scanning speed, scanning interval, layer thickness and the like;

(5) carrying out SLS forming;

(6) and taking out the SLS formed part after the SLS formed part is cooled, and removing residual powder on the surface of the formed part.

2. The selective laser sintering molding process of the nanoparticle synergistic macromolecular intumescent flame retardant TPU workpiece as claimed in claim 1, wherein the setting range of the laser power is 30W-45W.

3. The selective laser sintering molding process of the nanoparticle synergistic macromolecular intumescent flame retardant TPU workpiece as claimed in claim 1, wherein the setting range of the scanning speed is 7000 mm/s-10000 mm/s.

4. The selective laser sintering molding process of the nanoparticle synergistic macromolecular intumescent flame retardant TPU workpiece as claimed in claim 1, wherein the molding temperature is set within a range of 90-120 ℃.

5. The selective laser sintering molding process of the nanoparticle synergistic macromolecular intumescent flame retardant TPU workpiece as claimed in claim 1, wherein the setting range of the scanning interval is 0.08-0.15 mm.

6. The selective laser sintering molding process of the nanoparticle synergistic macromolecular intumescent flame retardant TPU workpiece as claimed in claim 1, wherein the setting range of the layer thickness in step (4) is 0.08-0.15 mm.

7. The selective laser sintering molding process of the nanoparticle synergistic macromolecular expansion flame retardant TPU workpiece as claimed in claim 1, wherein CaCO₃The components of the/triazine based intumescent flame retardant/TPU composite powder material comprise: 100 parts by mass of TPU powder for selective laser sintering, 5-25 parts by mass of triazine-based intumescent flame retardant and nano CaCO₃1-5 parts by mass, 0.3-0.4 part by mass of a flow assistant, 0.3-1 part by mass of an antioxidant and 0.1-1.2 parts by mass of a coupling agent.

8. The selective laser sintering molding process of the nanoparticle synergistic macromolecular intumescent flame retardant TPU workpiece according to claim 7, wherein the triazine intumescent flame retardant is prepared by blending and compounding a triazine macromolecular charring agent (CFA) and ammonium polyphosphate (APP) in a ratio of CFA to APP =1: 2-1: 6.

Technical Field

The invention belongs to the technical field of high polymer materials, and particularly relates to a selective laser sintering forming process of a nanoparticle synergistic macromolecular intumescent flame retardant TPU (thermoplastic polyurethane) product, in particular to an SLS (selective laser sintering) forming process applicable to preparation of automobile parts and interior trim parts with complex shapes.

Background

Thermoplastic Polyurethane (TPU) is a novel and multifunctional high-molecular engineering thermoplastic plastic with rubber elasticity, has good elasticity and aging resistance strength, and is environment-friendly. In recent years, TPU is widely used for manufacturing automobile parts and interior trim parts, but TPU belongs to flammable materials, has a limit oxygen index of only 18%, is violent in flame in a combustion process, is accompanied by a large amount of heat release and a large amount of toxic and harmful gas and smoke, and has a serious droplet phenomenon, so that the TPU is required to have certain flame retardant performance for the automobile parts and the interior trim parts.

At present, injection molding is generally adopted for processing and manufacturing automobile parts and interior trim parts, and although mass production can be realized, the cost is higher for manufacturing special-shaped parts and interior trim parts with complex shapes, such as automobile instrument panels, corrugated pipes and the like, and the manufacturing process of a mold is quite complex. The rapid prototyping technology is also called additive manufacturing technology and 3D printing technology, is a general name of a series of layer-by-layer part manufacturing technologies, and can be used for directly producing required models from CAD files by using a nearly full-automatic process, so that the development time and cost of product prototypes can be remarkably reduced. For the machining and forming of complex shapes, the cost can be greatly reduced, the forming period can be shortened, the utilization rate of materials can be improved, and the precision of finished parts can be improved. Rapid prototyping techniques include Fused Deposition Modeling (FDM), layered solid modeling (LOM), binder jet printing (3DP), Stereolithography (SLA), Selective Laser Melting (SLM), Selective Laser Sintering (SLS), and the like.

Selective Laser Sintering (SLS) is a technique for rapid prototyping that is suitable for rapid prototyping of thermoplastic polymer materials, metal materials, and ceramic materials. The working principle of the rapid forming system of the SLS process is shown in figure 1, the process device consists of a powder supply cylinder and a forming cylinder (a die cavity), a powder supply cylinder piston (a powder supply piston) rises during work, a layer of powder is uniformly paved on the forming cylinder piston (a working piston) by a powder paving roller, and a computer controls a two-dimensional scanning track of a laser beam according to a prototype slicing model and selectively sinters solid powder materials to form one layer of a part. The entire table is heated to a temperature slightly below the melting temperature of the powder prior to sintering to reduce thermal distortion and facilitate bonding to the previous layer. And after finishing one layer, the working piston descends one layer thick, the powder laying system lays new powder, and the laser beam is controlled to scan and sinter the new layer. The steps are repeated in a circulating way, and the three-dimensional part is obtained after the layers are overlapped.

Compared with other rapid prototyping technologies, the SLS technology has the following advantages: (1) the material selection is wide; (2) a supporting structure is not needed in the printing process; (3) any complex structural part can be manufactured, including hollow structures, hollow structures and the like; (4) the material utilization rate is high, and the unused powder material can be continuously used.

The influence of the SLS process parameters on the component performance is achieved by the energy provided during the powder sintering forming process. The energy required for sintering and forming the powder of SLS is provided by two forms: one is thermal energy, provided by infrared thermal radiation of heating lamps in the SLS printer forming silo; the other is laser, which is provided by infrared laser with the wavelength of 10.6 μm, and the powder material absorbs part of laser energy and converts the laser energy into heat energy, namely the thermal effect of infrared rays. Due to the two kinds of energy input, the powder is instantly changed from a solid state to a molten state during laser scanning, and powder material particles which are originally independent from each other are sintered together, so that the particles are bonded with each other, and the purpose of molding is achieved. The energy input in the SLS forming process is adjusted by adjusting the forming temperature and the laser energy density. The laser Energy Density (ED) is defined as in formula (1):

wherein, P is laser power, H is scanning interval, and ν is scanning speed. The forming temperature and the laser energy density are proper, if the numerical value is too small, powder particles cannot be bonded, and the formed product has a loose structure; if the value is too large, the powder absorbs too much energy, which can cause the over-burning and warping deformation, even scorching of the molded product. The thickness of the laser scanning layer determines the precision of the formed part, and a proper value should be selected. In summary, the processing parameters to be adjusted in the SLS forming process mainly include the forming temperature, the laser power, the scanning speed, the scanning distance, and the layer thickness.

Disclosure of Invention

The purpose of the invention is as follows: in order to overcome the problem that the traditional forming method is difficult to manufacture special-shaped flame-retardant TPU parts and interior trim parts, the invention aims to provide nano CaCO₃The selective laser sintering forming process of the/triazine-based intumescent flame retardant/TPU flame-retardant part has the advantages of simple process and high flexibility, can realize the structural abnormity of the part, and meets the requirements of different occasions. Nano CaCO produced by the process₃The/triazine-based intumescent flame retardant/TPU finished piece not only has good mechanical property, but also has a flame retardant function and excellent comprehensive performance.

The purpose of the invention is realized by the following technical scheme:

a selective laser sintering forming process of a nanoparticle synergistic macromolecular intumescent flame retardant TPU workpiece comprises the following steps:

(1) adjusting the size, position and direction of the designed STL file with an integrated three-dimensional structure by using a preprocessing program, and then cutting the STL file into a plurality of sections with the thickness of 0.05-0.7 mm;

(2) introducing the structure into software, setting SLS technological parameters, setting the forming temperature to be 90-120 ℃, the laser power to be 30-45W, the scanning speed to be 7000-10000 mm/s, the scanning interval to be 0.08-0.15 mm and the powder spreading thickness to be 0.08-0.15 mm, and then mixing the mixed nano CaCO₃Carrying out SLS forming on the triazine intumescent flame retardant/TPU composite powder to obtain a finished piece;

(3) and naturally cooling the obtained workpiece in the mold cavity, taking out the workpiece after the workpiece is completely cooled, and carrying out post-treatment on the workpiece by using a powder spray gun to remove residual powder on the surface of the workpiece to obtain a final finished product.

Compared with the traditional forming method (injection molding, extrusion molding and the like) of the heat-resistant polymer material, the TPU special-shaped part with the flame retardant property formed by SLS has the advantages of random and complex shape, high size and current precision, short cycle from design to forming, high utilization rate of raw materials and low production cost. The nanoparticle synergistic macromolecular intumescent flame retardant TPU manufactured by the process has good flame retardance. In the combustion process, the triazine-based intumescent flame retardant is used as a flame retardant main body, wherein an acid source, a carbon source and a gas source react to finally form a carbon layer on the surface of a TPU workpiece to isolate combustible gas, so that the flame retardant purpose is achieved, and the nano CaCO₃Plays a role of a flame-retardant synergist and further plays a flame-retardant effect of the intumescent flame retardant.

Further, the nanoparticle synergistic macromolecular intumescent flame retardant TPU product comprises the following components: 100 parts by mass of TPU powder for selective laser sintering, 5-25 parts by mass of triazine-based intumescent flame retardant and nano CaCO₃1-5 parts by mass, 0.3-0.4 part by mass of a flow assistant, 0.3-1 part by mass of an antioxidant, 0.1-1.2 parts by mass of a coupling agent and 1-5 parts by mass of an anti-dripping agent.

Further, the particle size range of the TPU powder for SLS is 50-200 mu m.

Further, the triazine-based intumescent flame retardant is prepared by compounding a triazine charring agent (CFA) and ammonium polyphosphate (APP) in a mass ratio of CFA to APP of 1: 2-1: 6.

Wherein, the acid source and the gas source of the triazine-based intumescent flame retardant are ammonium polyphosphate (APP), and the carbon source is triazine macromolecular charring agent (CFA) with an end-capped end with a benzene ring structure. The CFA has small water solubility, is not easy to absorb moisture, has good thermal stability and good compatibility with non-polar polymers, and can react with an acid source more easily in the combustion process to form a porous carbon layer to prevent the TPU substrate from contacting with flame and combustible gas. And adding nano CaCO₃The particles can react with phosphoric acid generated by dehydration of APP or be directly heated and decomposed to form CaO which is attached to the surface of the carbon layer to inhibit combustion; CO release₂The gas dilutes the combustible gas to achieve the purpose of synergistic flame retardance.

Further, the triazine charring agent is a triazine macromolecular charring agent with an internal structure introduced with a benzene ring, and the synthesis process is as follows: weighing 37g of cyanuric chloride, measuring 100ml of acetone, adding the acetone into a three-necked flask with a magnetic stirrer, simultaneously dripping aniline and NaOH aqueous solution into the flask, adjusting the pH to be neutral, putting the flask into an ice bath to enable the reaction temperature to be 0-5 ℃, reacting for 1 hour to form yellow precipitate, filtering a reaction product, washing the reaction product with deionized water, and drying the product at 50 ℃ in vacuum to obtain yellow powder which is an intermediate product. 48.2g of the intermediate product are weighed out and 250ml of CH are measured₃And adding CN into a three-neck flask, inserting a stirring paddle, a thermometer and a condenser tube, stirring the mixture at room temperature, then respectively adding 12g of diethylenetriamine and 40.4g of triethylamine, stirring for 60min, then heating in a water bath to 100 ℃, refluxing for 8h, cooling to room temperature, washing with deionized water after filtering, and drying in vacuum at 80 ℃ for 24h to obtain the light yellow powdery CFA char forming agent.

Further, the flow aid is gas phase Al₂O₃Fumed silica and nano TiO₂Nano SiO₂And one or more of nano SiC powder.

Further, the antioxidant is a hindered phenol antioxidant and/or a phosphite antioxidant.

Further, the coupling agent is silane coupling agent, and the dosage range of the silane coupling agent is triazine base expansion flame retardant and nano CaCO₃Adding of the total mass0.5％～2％。

Further, the anti-dripping agent is Polytetrafluoroethylene (PTFE).

The limit oxygen index of the prepared material can reach about 30% in the combustion process, the vertical combustion can reach UL-94V-0 level, and no molten drop is generated in the combustion process. The triazine-based macromolecular synergistic expansion flame-retardant TPU powder containing the nano particles is subjected to Selective Laser Sintering (SLS)3D printing and forming, and can be used for preparing corrugated pipes of an air inlet duct outside an automobile, heat shields of an engine (air inlet) and exhaust pipe, automobile instrument panels and other special-shaped automobile structural accessories with complex shapes, so that the flame retardance of the automobile parts is improved, and serious consequences and property loss caused by fire are reduced; meanwhile, the intelligent manufacturing represented by 3D printing has unique advantages for manufacturing workpieces with complex shapes.

Compared with the prior art, the invention has the following beneficial effects:

(1) the invention discloses a selective laser sintering forming process of a nanoparticle synergistic macromolecular expansion flame-retardant TPU (thermoplastic polyurethane) product, which solves a series of problems of complex forming process, higher cost, low utilization rate of raw materials, insufficient precision and the like of special-shaped automobile parts and interior parts of TPU with flame-retardant performance. The mass production of special-shaped parts and interior trim parts can be realized. The beneficial effect is very obvious.

(2) The selective laser sintering forming process of the nanoparticle synergistic macromolecular intumescent flame retardant TPU workpiece disclosed by the invention is simple in process and high in flexibility, can realize the abnormity of the workpiece, and meets various appearances required by different occasions.

Drawings

FIG. 1 is a schematic diagram of selective laser sintering.

FIG. 2 is a schematic structural diagram of the triazine macromolecular charring agent of the invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to specific experimental data, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The following examples provide a selective laser sintering molding process for a nanoparticle synergistic macromolecular intumescent flame retardant TPU article₃The/triazine based intumescent flame retardant/TPU heat resistant article comprises the following components: 100 parts of TPU powder for selective laser sintering, 15 parts of triazine-based intumescent flame retardant and nano CaCO₃3 parts by mass of flow assistant nano SiO₂0.3 part by mass, 0.5 part by mass of phosphite antioxidant, 0.35 part by mass of silane coupling agent and 2 parts by mass of anti-dripping agent PTFE. Wherein, the compounding ratio of CFA and APP in the triazine-based intumescent flame retardant is 1:3, the CFA is specifically a triazine macromolecular charring agent with an end-capped benzene ring structure, and the structure is shown in figure 2.

Example 1:

(1) adjusting the size, position and direction of a model of an STL file of the designed integrated three-dimensional structure standard sample by using a preprocessing program, and then cutting the STL file into a plurality of sections with the thickness of 0.2 mm;

(2) introducing the structure into software, setting SLS technological parameters, forming temperature of 100 deg.C, laser power of 35W, scanning speed of 9000mm/s, scanning interval of 0.08mm, and powder spreading thickness of 0.08mm, and mixing with nano CaCO₃Carrying out SLS molding on the/triazine based intumescent flame retardant/TPU composite powder to obtain a finished piece;

(3) and placing the obtained standard sample workpiece in a mold cavity for natural cooling, taking out the workpiece after the standard sample workpiece is completely cooled, and performing post-treatment on the workpiece by using a powder spray gun to remove residual powder on the surface of the workpiece to obtain a final standard sample finished product.

Example 2:

(1) adjusting the size, position and direction of a model of the STL file of the designed integrated three-dimensional structure standard sample by using a preprocessing program, and then cutting the STL file into a plurality of sections with the thickness of 0.5 mm;

(2) the structure is led into software, SLS technological parameters are set, the forming temperature is 110 ℃, the laser power is 35W, and the scanning speed is set8000mm/s, scanning interval 0.1mm, powder spreading thickness 0.12mm, and mixing with CaCO₃Carrying out SLS molding on the/triazine based intumescent flame retardant/TPU composite powder to obtain a finished piece;

(3) and placing the obtained standard sample workpiece in a mold cavity for natural cooling, taking out the workpiece after the standard sample workpiece is completely cooled, and performing post-treatment on the workpiece by using a powder spray gun to remove residual powder on the surface of the workpiece to obtain a final standard sample finished product.

Example 3:

(1) adjusting the size, position and direction of a model of the STL file of the designed integrated three-dimensional structure standard sample by using a preprocessing program, and then cutting the STL file into a plurality of sections with the thickness of 0.5 mm;

(2) introducing the structure into software, setting SLS technological parameters, forming temperature 95 deg.C, laser power 40W, scanning speed 8000mm/s, scanning distance 0.15mm, and powder spreading thickness 0.1mm, and mixing with CaCO₃Carrying out SLS molding on the/triazine based intumescent flame retardant/TPU composite powder to obtain a finished piece;

(3) and placing the obtained standard sample workpiece in a mold cavity for natural cooling, taking out the workpiece after the standard sample workpiece is completely cooled, and performing post-treatment on the workpiece by using a powder spray gun to remove residual powder on the surface of the workpiece to obtain a final standard sample finished product.

Example 4:

(1) adjusting the size, position and direction of a model of the STL file of the designed integrated three-dimensional structure standard sample by using a preprocessing program, and then cutting the STL file into a plurality of sections with the thickness of 0.5 mm;

(2) introducing the structure into software, setting SLS technological parameters, forming temperature at 105 deg.C, laser power at 45W, scanning speed at 9000mm/s, scanning distance at 0.14mm, and powder spreading thickness at 0.12mm, and mixing with nano CaCO₃Carrying out SLS molding on the/triazine based intumescent flame retardant/TPU composite powder to obtain a finished piece;

(3) and placing the obtained standard sample workpiece in a mold cavity for natural cooling, taking out the workpiece after the standard sample workpiece is completely cooled, and performing post-treatment on the workpiece by using a powder spray gun to remove residual powder on the surface of the workpiece to obtain a final standard sample finished product.

Example 5:

(1) adjusting the size, position and direction of a model of the STL file of the designed integrated three-dimensional structure standard sample by using a preprocessing program, and then cutting the STL file into a plurality of sections with the thickness of 0.5 mm;

(2) introducing the structure into software, setting SLS technological parameters, forming temperature 120 deg.C, laser power 35W, scanning speed 10000mm/s, scanning interval 0.12mm, powder spreading thickness 0.13mm, and mixing with nano CaCO₃Carrying out SLS molding on the/triazine based intumescent flame retardant/TPU composite powder to obtain a finished piece;

(3) and placing the obtained standard sample workpiece in a mold cavity for natural cooling, taking out the workpiece after the standard sample workpiece is completely cooled, and performing post-treatment on the workpiece by using a powder spray gun to remove residual powder on the surface of the workpiece to obtain a final standard sample finished product.

Example 6:

(1) adjusting the size, position and direction of a model of the STL file of the designed integrated three-dimensional structure standard sample by using a preprocessing program, and then cutting the STL file into a plurality of sections with the thickness of 0.1 mm;

(2) introducing the structure into software, setting SLS technological parameters, forming temperature of 100 deg.C, laser power of 45W, scanning speed of 7000mm/s, scanning interval of 0.08mm, and powder spreading thickness of 0.11mm, and mixing with nano CaCO₃Carrying out SLS molding on the/triazine based intumescent flame retardant/TPU composite powder to obtain a finished piece;

(3) and placing the obtained standard sample workpiece in a mold cavity for natural cooling, taking out the workpiece after the standard sample workpiece is completely cooled, and performing post-treatment on the workpiece by using a powder spray gun to remove residual powder on the surface of the workpiece to obtain a final standard sample finished product.

Example 7:

(1) adjusting the size, position and direction of a model of the STL file of the designed integrated three-dimensional structure standard sample by using a preprocessing program, and then cutting the STL file into a plurality of sections with the thickness of 0.1 mm;

(2) introducing the structure into software, setting SLS technological parameters, forming temperature 115 deg.C, laser power 40W, and scanningThe speed is 9500mm/s, the scanning distance is 0.15mm, the powder spreading thickness is 0.14mm, and then the mixed nano CaCO is added₃Carrying out SLS molding on the/triazine based intumescent flame retardant/TPU composite powder to obtain a finished piece;

(3) and placing the obtained standard sample workpiece in a mold cavity for natural cooling, taking out the workpiece after the standard sample workpiece is completely cooled, and performing post-treatment on the workpiece by using a powder spray gun to remove residual powder on the surface of the workpiece to obtain a final standard sample finished product.

Example 8:

(1) adjusting the size, position and direction of a model of the STL file of the designed integrated three-dimensional structure standard sample by using a preprocessing program, and then cutting the STL file into a plurality of sections with the thickness of 0.3 mm;

(2) introducing the structure into software, setting SLS technological parameters, forming temperature of 95 deg.C, laser power of 45W, scanning speed of 8500mm/s, scanning interval of 0.13mm, powder spreading thickness of 0.09mm, and mixing with nano CaCO₃Carrying out SLS molding on the/triazine based intumescent flame retardant/TPU composite powder to obtain a finished piece;

(3) and placing the obtained standard sample workpiece in a mold cavity for natural cooling, taking out the workpiece after the standard sample workpiece is completely cooled, and performing post-treatment on the workpiece by using a powder spray gun to remove residual powder on the surface of the workpiece to obtain a final standard sample finished product.

Example 9:

(1) adjusting the size, position and direction of a model of an STL file of the designed integrated three-dimensional structure standard sample by using a preprocessing program, and then cutting the STL file into a plurality of sections with the thickness of 0.4 mm;

(2) introducing the structure into software, setting SLS technological parameters, forming temperature of 110 deg.C, laser power of 45W, scanning speed of 7500mm/s, scanning distance of 0.11mm, and powder spreading thickness of 0.12mm, and mixing with nano CaCO₃Carrying out SLS molding on the/triazine based intumescent flame retardant/TPU composite powder to obtain a finished piece;

(3) and placing the obtained standard sample workpiece in a mold cavity for natural cooling, taking out the workpiece after the standard sample workpiece is completely cooled, and performing post-treatment on the workpiece by using a powder spray gun to remove residual powder on the surface of the workpiece to obtain a final standard sample finished product.

Example 10:

(1) adjusting the size, position and direction of a model of the STL file of the designed integrated three-dimensional structure standard sample by using a preprocessing program, and then cutting the STL file into a plurality of sections with the thickness of 0.5 mm;

(2) introducing the structure into software, setting SLS technological parameters, forming temperature at 120 deg.C, laser power at 45W, scanning speed at 9000mm/s, scanning distance at 0.1mm, and powder spreading thickness at 0.12mm, and mixing with nano CaCO₃Carrying out SLS molding on the/triazine based intumescent flame retardant/TPU composite powder to obtain a finished piece;

(3) and placing the obtained standard sample workpiece in a mold cavity for natural cooling, taking out the workpiece after the standard sample workpiece is completely cooled, and performing post-treatment on the workpiece by using a powder spray gun to remove residual powder on the surface of the workpiece to obtain a final standard sample finished product.

Effect verification:

the performance test of the standard sample of the nanoparticle synergistic macromolecular intumescent flame retardant TPU obtained from the above examples 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 was carried out according to the following standard.

The tensile test was carried out according to GB/T528, the test specimens were standard dumbbell type II test specimens, 75mm in total length, 40mm in gauge length, 4mm in width, 2mm in thickness and 50mm/min in tensile speed. The tensile strength and elongation at break of the test specimens were recorded.

A simple beam (notched) impact test was performed according to GB/T1043.1-2008. The length of the sample is 80mm, the width is 10mm, the thickness is 4mm, the distance between the supporting lines is 60mm, and the notch is 0.25mm of the I-shaped notch. The impact strength of the test specimens was recorded.

Limited Oxygen Index (LOI) tests were performed according to ASTM D2863. LOI is defined as the limit of the oxygen concentration required for the test specimens perpendicular to the fixture with glass lamp cover insulation, by igniting the upper portion of the specimen with an igniter under a nitrogen/oxygen mixture atmosphere for a 3 minute burn or to the upper 5cm mark. According to the test standard, the test specimen has a length of 130mm, a width of 6mm and a thickness of 3 mm. The LOI value of the sample was recorded.

The vertical burning test was conducted in accordance with ASTM D3801. Adjusting the flame of the Bunsen burner for igniting the sample strips to be 20mm blue flame, moving the lower ends of the vertically suspended sample strips into the flame of 10mm, moving the flame after igniting for 10s, and recording the sustained combustion time of the sample strips as t₁(ii) a After extinguishing, ignition with the bunsen burner was continued for 10s, and the duration of burning of the sample strip after removal of the flame was recorded as t₂(ii) a Smoldering time of t₃. Absorbent cotton was placed 12cm under the sample strips, and the samples were observed and recorded for dripping due to combustion and for ignition of the absorbent cotton, and the UL-94 ratings of the samples were classified into V-0, V-1, and V-2, as shown in Table 1. According to the test standard, the test specimen has a length of 130mm, a width of 13mm and a thickness of 1.6 mm. The UL-94 rating of the test specimen was recorded.

All samples were thermostated at 25 ℃ for 24 hours before testing. The test temperature was 25 ℃. The results of the performance tests on the standard test specimens of the examples are shown in Table 2.

TABLE 1 UL-94 Classification Standard for Polymer materials

Table 2 results of performance test of standard test specimens of respective examples

Note: NB denotes no fracture

The invention has many applications, and the above description is only a preferred embodiment of the invention. It should be noted that the above examples are only for illustrating the present invention, and are not intended to limit the scope of the present invention. It will be apparent to those skilled in the art that various modifications can be made without departing from the principles of the invention and these modifications are to be considered within the scope of the invention.