阅读说明：本技术 一种轻质保温秸秆复合材料的制备方法 (Preparation method of light heat-preservation straw composite material ) 是由 宋永明 庄鹏燕 凌彩珊 张聪聪 杨思雯 许泽生 曹磊 于 2021-05-07 设计创作，主要内容包括：一种轻质保温秸秆复合材料的制备方法,它涉及秸秆复合材料的制备方法。本发明要解决现有秸秆人造板在制板过程会产生有毒的废气,且热压时间长,成本高的问题。制备方法：一、称取；二、制备预混料；三、秸塑复合板的制备；四、粘接。本发明用于轻质保温秸秆复合材料的制备。(A preparation method of a light heat-preservation straw composite material relates to a preparation method of a straw composite material. The invention aims to solve the problems that the existing straw artificial board can generate toxic waste gas in the board making process, and the hot pressing time is long and the cost is high. The preparation method comprises the following steps: firstly, weighing; secondly, preparing a premix; thirdly, preparing the straw-plastic composite board; fourthly, bonding. The invention is used for preparing the light heat-preservation straw composite material.)

1. The preparation method of the light heat-preservation straw composite material is characterized by comprising the following steps of:

firstly, weighing:

weighing 83 to 87 parts of straws, 13 to 17 parts of maleic anhydride grafted polyethylene, 0.4 to 0.6 part of stearic acid and 0.4 to 0.6 part of PE wax according to the mass parts;

secondly, preparing premix:

mixing and granulating the weighed straws, maleic anhydride grafted polyethylene, stearic acid and PE wax, and then cooling and crushing to obtain a premix;

thirdly, preparing the straw-plastic composite board:

uniformly spreading the premix into a mold, then placing the mold in a hot press, preheating for 3-5 min under the condition that the temperature of an upper pressing plate and a lower pressing plate is 145-155 ℃ and the pressure is 4-5 MPa, keeping the pressure for 7-9 min under the condition that the temperature of the upper pressing plate and the lower pressing plate is 145-155 ℃ and the pressure is 1-2 MPa, cold pressing for 30 s-1 min under the conditions that the temperature of the upper pressing plate and the lower pressing plate is 15-20 ℃ and the pressure is 1-2 MPa, demolding, naturally cooling, and finally standing at room temperature to obtain the straw-plastic composite plate;

fourthly, bonding:

bonding and standing the straw-plastic composite boards at two sides and the polyurethane foam board in the middle, then placing the straw-plastic composite boards on a lower pressing plate of a cold press, keeping the temperature of the upper pressing plate and the lower pressing plate at 65-75 ℃ for 20-30 min under the condition that the upper pressing plate is 0.5-1 cm away from the surface of a sample, demolding and naturally cooling to obtain the light heat-preservation straw composite material.

2. The preparation method of the light heat-preservation straw composite material as claimed in claim 1, wherein the total parts by mass of the straw, the maleic anhydride grafted polyethylene, the stearic acid and the PE wax weighed in the step one are 100 parts.

3. The preparation method of the light heat-preservation straw composite material as claimed in claim 1, wherein the straw in the first step is rice straw, wheat straw or corn straw.

4. The preparation method of the light heat-preservation straw composite material as claimed in claim 1, wherein the straw in the first step is obtained after being dried for 12-18 h at the temperature of 100-105 ℃.

5. The preparation method of the light heat-preservation straw composite material as claimed in claim 1, wherein the mixing in the second step is carried out at a high speed for 3-5 min under the condition that the rotation speed is 1500-2000 r/min.

6. The preparation method of the light heat-preservation straw composite material according to claim 1, wherein the specific granulation setting parameters in the second step are as follows: the temperature of the first zone is 150 ℃, the temperature of the second zone is 145 ℃, the temperature of the third zone is 150 ℃, the temperature of the fourth zone is 155 ℃, the temperature of the fifth zone is 150 ℃, the temperature of the sixth zone is 150 ℃, the rotating speed of the main engine is 50r/min, and the feeding speed is 35 r/min; and crushing the mixture in the second step until the particle size is 0.5-2 mm.

7. The preparation method of the light heat-preservation straw composite material according to claim 1, characterized in that the thickness of the straw-plastic composite plate in the third step is 2 mm-4 mm.

8. The preparation method of the light heat-preservation straw composite material as claimed in claim 1, wherein the standing is carried out for 22-26 h at room temperature in the third step.

9. The preparation method of the light heat-preservation straw composite material as claimed in claim 1, wherein the thickness of the polyurethane foam board in the fourth step is 1 cm-1.5 cm.

10. The preparation method of the light heat-insulating straw composite material according to claim 1, wherein in the fourth step, the straw-plastic composite plates are bonded at two sides by using an epoxy resin adhesive, and the polyurethane foam plate is bonded at the middle.

Technical Field

The invention relates to a preparation method of a straw composite material.

Background

China is a big agricultural country and the straw resources are very rich. With the rapid development of modern rural economy and productivity, how to effectively utilize crop straws becomes a hot topic of debate in the field of energy and environment. Therefore, the method has important practical significance in discussing the resource utilization of the crop straws and reasonably developing and utilizing the technology. At present, the utilization of crop straws in China is still in a primary stage, and the utilization can be mainly summarized into the following 4 types: straw returning, straw energy regeneration, straw feed conversion and straw building material utilization.

The straw building material is a general name of building materials which are formed by taking crop straws as main raw materials, adding auxiliary materials and reinforcing materials according to a certain proportion and through a physical, chemical or combination mode of the two materials and have special functions and structural characteristics. The straw building material has the advantages of no radiation, no pollution and no toxicity, and people find that the straw building material has no difference with functions of other building materials after long-time use, and the structure of a building is very stable. The straw building material is developed vigorously, the problem of comprehensive utilization of the straw is solved, haze harm caused by straw combustion is prevented, and the straw building material has remarkable economic and social benefits.

The straw brick is characterized in that straw is arranged and packaged by a straw packaging machine, so that the original loose straw becomes compact, then is cut into bricks, and is piled up to build a house by using the straw brick. The straw brick has many excellent qualities, such as high hardness and can bear a certain load. The house environment of building with the straw brick is comfortable, reduces external noise, and along with the country advocates energy-saving material vigorously, advocates the recycling of straw, more and more enterprises and colleges are dedicated to the research of recycling of straw, because the low price of straw brick, it is effectual to keep warm, receives people's liking deeply.

The artificial straw board is a board formed by processing straws in a series of processes. The artificial straw board can be divided into two types according to the processing technology: gluing with adhesives and glueless gluing. The processing technology of gluing by using the adhesive comprises the following steps: the other method is to mechanically process the straws into fibers, use urea-formaldehyde resin as an adhesive and form an artificial straw board with a certain density by hot pressing. The glue-free gluing process comprises the following steps: the straw is self-knotted by utilizing the self-properties of the straw and adopting a certain processing technology, such as high temperature and high pressure, and then is hot-pressed into a plate. The thermoforming method of glue-free gluing is totally divided into three forms: common hot pressing, steam explosion pretreatment and steam injection hot pressing. The occurrence of the artificial straw board increases a way for recycling and treating the straw, and the problem how to reduce pollution of the used adhesive and optimize the adhesive-free gluing process is needed to be researched.

Straw cement-based composite material is characterized in that straw fibers after a series of treatments are added into a cement matrix, and straws are used as reinforcing materials, so that the durability and mechanical property of cement are improved, and the problem of straw utilization is solved. Materials with different characteristics can be obtained by different processes, for example, in a specified interval, the mixing amount of the fly ash and the urea-formaldehyde resin is increased, the water absorption rate of the material is reduced, and the water resistance is enhanced; the material obtained by the action of the wheat straw and the additive has excellent heat preservation performance.

The straw building material is developed vigorously, the problem of comprehensive utilization of the straw can be solved, haze harm caused by straw combustion is prevented, remarkable economic benefit, social benefit and environmental benefit are achieved, the industrial production technology, the preparation process, the formula optimization, the performance improvement technology and the supporting equipment of the straw building material are further problems which need to be solved urgently, and the straw building material has a good development prospect.

The rigid polyurethane foam is a high molecular polymer prepared by mixing isocyanate and polyether serving as main raw materials through special equipment under the action of various auxiliary agents such as a foaming agent, a catalyst, a flame retardant and the like and performing high-pressure spraying and on-site foaming. Polyurethane has both soft and hard foams. The soft bubbles are in an open pore structure, and the hard bubbles are in a closed pore structure; soft foams are classified into skinned and non-skinned. The main function of the polyurethane soft foam is buffering, and is commonly used for sofa furniture, pillows, cushions, toys, clothes and sound insulation linings. The polyurethane rigid foam is a novel synthetic material with heat preservation and waterproof functions, has low heat conductivity coefficient, is only 0.022-0.033W/(m.K), is equivalent to half of an extruded sheet, and has the lowest heat conductivity coefficient in all heat preservation materials. The hard polyurethane foam plastic is mainly applied to heat preservation of building outer walls, integration of roof waterproof and heat preservation, heat preservation and heat insulation of refrigerators, pipeline heat preservation materials, building boards, refrigerated trucks, cold storage heat insulation materials and the like. The business fields mainly comprise door and window engineering installation, home decoration and the like.

However, the development of the straw artificial board still has some restriction factors at present, and the restriction factors are mainly the use of adhesives in the board making process. At present, the production lines of the artificial straw boards which are built at home and abroad almost adopt isocyanate as an adhesive, and the method increases the production process and materials and improves the production cost of the products. Secondly, the market price of the isocyanate is always high, and the input of the adhesive even accounts for more than 50% of the product cost by adopting the isocyanate as an adhesive. In addition, during the production process, free isocyanate is generated during glue mixing and paving, the toxic waste gas can poison the respiratory tract and the lung of people, protection is needed, and harmful gas is collected and treated in a harmless way, and the necessary equipment and measures can increase the production cost.

The hot pressing time also imposes production constraints. The straw has loose structure, the main components are cellulose, hemicellulose and lignin, the content of fiber cells (60%) is lower than that of wood (75% -98%), the content of solution extract is higher, ash content is large, and compared with wood, the mechanical strength of the straw is much lower. Because the crop straws have more gaps, small density and low heat transfer efficiency, the hot pressing time of the straw artificial board is much longer than that of a wood shaving board or a wood medium-density fiberboard under the same conditions (such as the density and the thickness of the board are the same). The relatively long hot pressing time results in decreased production efficiency, increased heating costs, and increased production costs.

Disclosure of Invention

The invention provides a preparation method of a light heat-insulation straw composite material, aiming at solving the problems that the existing straw artificial board can generate toxic waste gas in the board making process, and has long hot pressing time and high cost.

A preparation method of a light heat-preservation straw composite material is carried out according to the following steps:

firstly, weighing:

weighing 83 to 87 parts of straws, 13 to 17 parts of maleic anhydride grafted polyethylene, 0.4 to 0.6 part of stearic acid and 0.4 to 0.6 part of PE wax according to the mass parts;

secondly, preparing premix:

mixing and granulating the weighed straws, maleic anhydride grafted polyethylene, stearic acid and PE wax, and then cooling and crushing to obtain a premix;

thirdly, preparing the straw-plastic composite board:

uniformly spreading the premix into a mold, then placing the mold in a hot press, preheating for 3-5 min under the condition that the temperature of an upper pressing plate and a lower pressing plate is 145-155 ℃ and the pressure is 4-5 MPa, keeping the pressure for 7-9 min under the condition that the temperature of the upper pressing plate and the lower pressing plate is 145-155 ℃ and the pressure is 1-2 MPa, cold pressing for 30 s-1 min under the conditions that the temperature of the upper pressing plate and the lower pressing plate is 15-20 ℃ and the pressure is 1-2 MPa, demolding, naturally cooling, and finally standing at room temperature to obtain the straw-plastic composite plate;

fourthly, bonding:

bonding and standing the straw-plastic composite boards at two sides and the polyurethane foam board in the middle, then placing the straw-plastic composite boards on a lower pressing plate of a cold press, keeping the temperature of the upper pressing plate and the lower pressing plate at 65-75 ℃ for 20-30 min under the condition that the upper pressing plate is 0.5-1 cm away from the surface of a sample, demolding and naturally cooling to obtain the light heat-preservation straw composite material.

The invention has the beneficial effects that:

according to the invention, the biomass environment-friendly material is taken as a base material, no adhesive is added in the preparation process of the straw artificial board, only a small amount of filler (stearic acid and PE wax are added to increase the crosslinking strength), the self property of the straw is completely utilized to crosslink the straw into the board, the board can be completely degraded, the hot pressing time is shortened, the energy consumption is saved, and only maleic anhydride grafted polyethylene is added as plastic. Straw-plastic composite board inner knotThe resultant strength is 2.10MPa, the bending strength is high (the bending strength is 29.03MPa, the elastic modulus is 3.15GPa), the heat conductivity coefficient is 0.3215W/m.K, and the density is 1.27g/cm²The water absorption thickness expansion rate is 35.31%.

The straw composite material and the polyurethane foam board are physically bonded, the polyurethane hard foam body is a novel synthetic material with heat preservation and waterproof functions, and the surface of the polyurethane hard foam body is provided with a flame-retardant coating and has certain fire resistance. Through a specific curing process, the performance of the polyurethane foam board and the straw board after being compounded is excellent, the bonding performance is good (the internal bonding strength is 0.32MPa), the bending strength is high (the bending strength is 3.51MPa, and the elastic modulus is 0.09GPa), the heat conductivity coefficient is small, the density is small, the weight is light, and the acoustic performance is excellent.

The invention is beneficial to reducing carbon emission and realizing carbon cycle. Through the utilization of the biomass materials, the discharge of wastes is reduced, and the utilization rate of agricultural production is increased. The invention belongs to an environment-friendly product, and has certain environmental benefit; the raw materials are low in price, have certain economic benefit and are suitable for mass production of manufacturers.

The invention relates to a preparation method of a light heat-preservation straw composite material.

Drawings

FIG. 1 is a diagram of a light heat-insulating straw composite material prepared in the first embodiment;

FIG. 2 is a diagram of a light heat-insulating straw composite material prepared in the first embodiment after a bending performance test;

FIG. 3 is a diagram of a light weight insulation straw composite prepared in the first embodiment after the internal bonding strength test;

FIG. 4 is a 200 times optical microscope picture of the light heat-insulating straw composite material prepared in the first embodiment;

FIG. 5 is a 100 times optical microscope picture of the light heat-insulating straw composite material prepared in the first embodiment.

Detailed Description

The first embodiment is as follows: the embodiment provides a preparation method of a light heat-preservation straw composite material, which is carried out according to the following steps:

firstly, weighing:

weighing 83 to 87 parts of straws, 13 to 17 parts of maleic anhydride grafted polyethylene, 0.4 to 0.6 part of stearic acid and 0.4 to 0.6 part of PE wax according to the mass parts;

secondly, preparing premix:

mixing and granulating the weighed straws, maleic anhydride grafted polyethylene, stearic acid and PE wax, and then cooling and crushing to obtain a premix;

thirdly, preparing the straw-plastic composite board:

uniformly spreading the premix into a mold, then placing the mold in a hot press, preheating for 3-5 min under the condition that the temperature of an upper pressing plate and a lower pressing plate is 145-155 ℃ and the pressure is 4-5 MPa, keeping the pressure for 7-9 min under the condition that the temperature of the upper pressing plate and the lower pressing plate is 145-155 ℃ and the pressure is 1-2 MPa, cold pressing for 30 s-1 min under the conditions that the temperature of the upper pressing plate and the lower pressing plate is 15-20 ℃ and the pressure is 1-2 MPa, demolding, naturally cooling, and finally standing at room temperature to obtain the straw-plastic composite plate;

fourthly, bonding:

bonding and standing the straw-plastic composite boards at two sides and the polyurethane foam board in the middle, then placing the straw-plastic composite boards on a lower pressing plate of a cold press, keeping the temperature of the upper pressing plate and the lower pressing plate at 65-75 ℃ for 20-30 min under the condition that the upper pressing plate is 0.5-1 cm away from the surface of a sample, demolding and naturally cooling to obtain the light heat-preservation straw composite material.

The straw powder adopted by the embodiment is a biomass material, has wide source and low price, and is green and environment-friendly. As agricultural waste, the wood-plastic composite board has high production capacity, is easy to obtain, has chemical properties similar to wood, and is a new product in the artificial board industry. In the preparation process of the artificial straw board, no adhesive is added, and the artificial straw board is crosslinked into a board by using the self property of the straw at high temperature and high pressure. The straw board and the epoxy resin adhesive have good adhesive performance, and the final product has excellent bonding strength. The waste straws are recycled, so that the burning and carbon emission of the straws are reduced, the environment is effectively protected, and the air is purified.

The beneficial effects of the embodiment are as follows:

the embodiment uses biomass for environmental protectionThe material is a base material, no adhesive is added in the preparation process of the straw artificial board, only a small amount of filler (stearic acid and PE wax increase the crosslinking strength) is added, the self properties of the straws are completely utilized to crosslink into a board, the board can be completely degraded, the hot pressing time is shortened, the energy consumption is saved, and only maleic anhydride grafted polyethylene is added to the added plastic. The straw-plastic composite board has the advantages of internal bonding strength of 2.10MPa, high bending strength (the bending strength is 29.03MPa, the elastic modulus is 3.15GPa), heat conductivity coefficient of 0.3215W/m.K and density of 1.27g/cm²The water absorption thickness expansion rate is 35.31%.

The straw composite material and the polyurethane foam board are physically bonded in the embodiment, the polyurethane hard foam body is a novel synthetic material with heat preservation and waterproof functions, and the surface of the polyurethane hard foam body is provided with the flame-retardant coating which has certain fire resistance. Through a specific curing process, the performance of the polyurethane foam board and the straw board after being compounded is excellent, the bonding performance is good (the internal bonding strength is 0.32MPa), the bending strength is high (the bending strength is 3.51MPa, and the elastic modulus is 0.09GPa), the heat conductivity coefficient is small, the density is small, the weight is light, and the acoustic performance is excellent.

The embodiment is beneficial to reducing carbon emission and realizing carbon circulation. Through the utilization of the biomass materials, the discharge of wastes is reduced, and the utilization rate of agricultural production is increased. The embodiment belongs to an environment-friendly product and has certain environmental benefit; the raw materials are low in price, have certain economic benefit and are suitable for mass production of manufacturers.

The second embodiment is as follows: the first difference between the present embodiment and the specific embodiment is: the total parts by mass of the straws, the maleic anhydride grafted polyethylene, the stearic acid and the PE wax weighed in the step one are 100 parts. The rest is the same as the first embodiment.

The third concrete implementation mode: this embodiment is different from the first or second embodiment in that: the straws in the step one are rice straws, wheat straws or corn straws. The other is the same as in the first or second embodiment.

The fourth concrete implementation mode: the difference between this embodiment mode and one of the first to third embodiment modes is: the straws in the step one are dried for 12 to 18 hours at the temperature of between 100 and 105 ℃ to obtain the straw food. The other is the same as in the first or second embodiment.

The specific embodiment is dried and then taken out to avoid contacting with moisture as much as possible in the process of configuration.

The fifth concrete implementation mode: the difference between this embodiment and one of the first to fourth embodiments is: the mixing in the second step is specifically that the mixture is rotated at a high speed for 3min to 5min under the condition that the rotating speed is 1500r/min to 2000 r/min. The rest is the same as the first to fourth embodiments.

The sixth specific implementation mode: the present embodiment is different from one or more of the first to fifth embodiments in that: the granulation in the second step specifically sets parameters: the temperature of the first zone is 150 ℃, the temperature of the second zone is 145 ℃, the temperature of the third zone is 150 ℃, the temperature of the fourth zone is 155 ℃, the temperature of the fifth zone is 150 ℃, the temperature of the sixth zone is 150 ℃, the rotating speed of the main engine is 50r/min, and the feeding speed is 35 r/min; and crushing the mixture in the second step until the particle size is 0.5-2 mm. The rest is the same as the first to fifth embodiments.

The seventh embodiment: the difference between this embodiment and one of the first to sixth embodiments is: the thickness of the straw-plastic composite board in the third step is 2 mm-4 mm. The others are the same as the first to sixth embodiments.

The specific implementation mode is eight: the present embodiment differs from one of the first to seventh embodiments in that: standing for 22-26 h at room temperature in the third step. The rest is the same as the first to seventh embodiments.

The specific implementation method nine: the present embodiment differs from the first to eighth embodiments in that: the thickness of the polyurethane foam plate in the fourth step is 1 cm-1.5 cm. The other points are the same as those in the first to eighth embodiments.

The detailed implementation mode is ten: the present embodiment differs from one of the first to ninth embodiments in that: and in the fourth step, the straw-plastic composite board is adhered on two sides by using an epoxy resin adhesive in a manner that a polyurethane foam board is arranged in the middle. The other points are the same as those in the first to ninth embodiments.

The curing agent of the embodiment is an ammonia component, generates a small amount of toxic gas in the bonding process, and is non-toxic after being cured.

The following examples were used to demonstrate the beneficial effects of the present invention:

the first embodiment is as follows:

a preparation method of a light heat-preservation straw composite material is carried out according to the following steps:

firstly, weighing:

weighing 85 parts of straw, 14 parts of maleic anhydride grafted polyethylene, 0.5 part of stearic acid and 0.5 part of PE wax in parts by mass;

secondly, preparing premix:

mixing and granulating the weighed straws, maleic anhydride grafted polyethylene, stearic acid and PE wax, and then cooling and crushing to obtain a premix;

thirdly, preparing the straw-plastic composite board:

uniformly spreading 100g of premix into a 3mm mold, then placing the mold in a hot press, preheating for 5min under the condition that the temperature of an upper pressing plate and a lower pressing plate is 150 ℃, maintaining the pressure for 9min under the conditions that the temperature of the upper pressing plate and the temperature of the lower pressing plate are 150 ℃ and the pressure of the upper pressing plate and the lower pressing plate are 4MPa, cold pressing for 1min under the conditions that the temperature of the upper pressing plate and the lower pressing plate are 20 ℃ and the pressure of the upper pressing plate and the lower pressing plate is 1MPa, demolding, naturally cooling, and finally standing at room temperature to obtain a straw-plastic composite plate;

fourthly, bonding:

and (3) bonding and standing in a manner that straw-plastic composite plates are arranged on two sides and a polyurethane foam plate is arranged in the middle, then placing on a lower pressing plate of a cold press, preserving heat for 30min under the conditions that the temperature of the upper pressing plate and the lower pressing plate is 60 ℃ and the distance between the upper pressing plate and the surface of the sample is 1cm, demolding and naturally cooling to obtain the light heat-preservation straw composite material.

The straws in the step one are rice straws.

The straw in the step one is obtained after being dried for 14 hours at the temperature of 103 ℃.

The mixing in the second step is specifically that the mixture is rotated at a high speed for 3min under the condition that the rotating speed is 1500 r/min.

The granulation in the second step specifically sets parameters: the temperature of the first zone is 150 ℃, the temperature of the second zone is 145 ℃, the temperature of the third zone is 150 ℃, the temperature of the fourth zone is 155 ℃, the temperature of the fifth zone is 150 ℃, the temperature of the sixth zone is 150 ℃, the rotating speed of the main engine is 50r/min, and the feeding speed is 35 r/min; and crushing the mixture in the second step until the particle size is 0.5-2 mm.

The thickness of the straw-plastic composite board in the third step is 3 mm.

Standing at room temperature for 24h in the third step.

The polyurethane foam sheet described in step four had a thickness of 1 cm.

And in the fourth step, the straw-plastic composite boards are bonded by using an epoxy resin adhesive (A: B ═ 1:1) in a mode that the straw-plastic composite boards are arranged at two sides and the polyurethane foam board is arranged in the middle.

Comparison experiment one: the comparative experiment differs from the first example in that: in the first step, 75 parts of straw, 24 parts of maleic anhydride grafted polyethylene, 0.5 part of stearic acid and 0.5 part of PE wax are weighed according to parts by weight. The rest is the same as the first embodiment.

Comparative experiment two: the comparative experiment differs from the first example in that: in the first step, 80 parts of straw, 19 parts of maleic anhydride grafted polyethylene, 0.5 part of stearic acid and 0.5 part of PE wax are weighed according to parts by weight. The rest is the same as the first embodiment.

A third comparative experiment: the comparative experiment differs from the first example in that: in the first step, 90 parts of straw, 9 parts of maleic anhydride grafted polyethylene, 0.5 part of stearic acid and 0.5 part of PE wax are weighed according to parts by weight. The rest is the same as the first embodiment.

And a fourth comparative experiment: the comparative experiment differs from the first example in that: and in the fourth step, the straw-plastic composite boards are adhered and placed in a way that the straw-plastic composite boards are arranged on two sides and the PE foam board is arranged in the middle. The rest is the same as the first embodiment.

A fifth comparative experiment: the comparative experiment differs from the first example in that: and in the fourth step, the straw-plastic composite boards are adhered and placed in a way that the straw-plastic composite boards are arranged on two sides and the PS foam board is arranged in the middle. The rest is the same as the first embodiment.

Table 1 examples and comparative experiments one to three prepared straw plastic composite board performance indexes

Table 2 Performance indexes of light heat-insulating straw composite material prepared in example one and comparative experiments from four to five

FIG. 1 is a diagram of a light heat-insulating straw composite material prepared in the first embodiment; as can be seen, the resulting product had a smooth surface.

FIG. 2 is a diagram of a light heat-insulating straw composite material prepared in the first embodiment after a bending performance test; as can be seen, the cross-section was uniform after the bending property test.

FIG. 3 is a diagram of a light weight insulation straw composite prepared in the first embodiment after the internal bonding strength test; as can be seen from the figure, the epoxy resin adhesive has better performance for gluing the straw-plastic composite board and the polyurethane foam, and is broken from the polyurethane foam board.

FIG. 4 is a 200 times optical microscope picture of the light heat-insulating straw composite material prepared in the first embodiment; FIG. 5 is a 100 times optical microscope picture of the light heat-insulating straw composite material prepared in the first embodiment. As can be seen from the figure, the shape of the straw powder can be clearly seen on the surface of the sample, the surface is compact, and the straw powder is irregularly crosslinked. The surface is smooth and flat.