Degradable biological composite material based on PCL and straw filler

Abstract

The invention discloses a degradable biological composite material based on PCL and straw filler and a preparation method of the degradable biological composite material, and relates to the technical field of biodegradable composite materials, the biological composite material takes PCL as a matrix and triticale straw and oat straw as filler, and the degradation performance is remarkably improved on the basis of maintaining the performance of the composite material; the straw filler has the advantages of being low in cost, wide in source, renewable, environmentally friendly and the like. The formula and the preparation process of the PCL / straw composite material are simple, the operability is high, and the PCL / straw composite material has wide application potential, especially in the field of degradable biological composite materials. Part of materials of the composite material are derived from natural renewable substances, the composite material has good biodegradability and environment-friendly characteristics, meanwhile, the processing stability of the PCL matrix is ensured, and the composite material is suitable for products such as packaging materials and transplantable seedling pots.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of degradable biological composite materials, and relates to a composite material based on biodegradable polymers and natural plant fibers; in particular, the present application relates to a degradable biological composite material taking polycaprolactone (PCL) as a matrix and taking agricultural waste straw as a filler and a preparation method. BACKGROUND

[0002] Plant fiber reinforced polymer composites are widely used in many fields due to their light weight, low cost, easy forming and other advantages. However, most of the current composites still use non-degradable polymers such as polyethylene (PE) and polypropylene (PP) as the matrix, and their waste will cause persistent pressure on the environment. With the improvement of environmental protection requirements, the development of composites based on biodegradable polymers has become an important research direction.

[0003] Polycaprolactone (PCL) is an aliphatic polyester with good biocompatibility, processing performance and controllable degradation, and is one of the ideal matrices for preparing degradable composites. At the same time, the yield of crop waste straw is huge, and its resource utilization is an effective way to solve the problems of environmental pollution and resource waste. Previous studies have shown that biomass fillers such as coconut shell fibers, coffee shells and almond shells can be combined with PCL to affect the performance of the composite and accelerate its degradation.

[0004] Triticale and oats are widely planted as grain and forage crops in China, and a large amount of straw is abandoned every year. The traditional burning treatment not only wastes resources but also pollutes the environment. The application of straw as a reinforcing filler in degradable composites can realize "waste treatment with waste", reduce environmental pollution caused by straw burning or random disposal, and realize resource recycling.

[0005] At present, there are few studies on triticale straw and oat straw, two specific agricultural wastes. These two straws have certain differences in chemical composition and fiber structure from other straws, and the interface interaction, performance influence rule and degradation regulation mechanism after being combined with PCL are not clear. Through reasonable formula and process method, a composite material with good performance and controllable degradation rate is prepared, which has important practical significance for promoting the resource utilization of agricultural wastes and expanding the application field of plant fiber reinforced polymer composites. SUMMARY

[0006] The purpose of the present application is to provide a degradable biological composite material based on PCL and straw filler, which has soil environment degradable performance to solve the problems in the background art.

[0007] To achieve the above object, the present application provides the following technical scheme: a degradable biological composite material based on PCL and straw filler, raw materials including the following components: triticale straw 30-50 parts, oat straw 30-50 parts, PCL matrix 50-70 parts, organic solvent 50-70 parts, coupling agent 3-5 parts, nano-montmorillonite 1-3 parts; the preparation method of the degradable biological composite material is as follows: S1, pretreating the straw; S2, putting the straw segments into a washing container, stirring and soaking multiple times until there is no obvious impurity in the distilled water, then draining and drying in an oven; S3, crushing and sieving the dried straw segments, drying again in an oven to obtain straw powder filler; S4, adding the coupling agent and nano-montmorillonite to the straw powder, mixing to obtain a blend A containing straw, coupling agent and nano-montmorillonite; S5, drying PCL at 40℃, dissolving the dried PCL in an organic solvent, and mechanically stirring to form a homogeneous solution; S6, adding the obtained blend A to the homogeneous solution, continuously stirring to form a uniform composite slurry B; S7, placing the composite slurry B in an oven to completely volatilize the organic solvent, obtaining a solid mixture C, granulating the mixture C to obtain granules for preparing the composite material; S8, placing the granules in a heated mold, closing the mold, heating and pressing the mold in a hot press, performing 1-3 times of exhaust and vacuumizing, continuing to heat and press for a period of time, then pressure-keeping cooling to room temperature; S9, polishing and deburring the rough sample after demolding, then obtaining a standard sample for testing the degradation performance.

[0008] Further, in S1, the straw includes triticale straw and oat straw; the straw is cut into straw segments of 10-15 cm, and then larger impurities in the straw are removed using a 6 cm sieve.

[0009] Further, in S2, the treated straw segments are put into a washing container, so that the straw is completely immersed in distilled water, the straw is stirred for 15 minutes using a stirrer, then the straw is soaked for 25 minutes, the soaked water is poured out and fresh water is added, the straw is stirred and soaked again, and the process is repeated three times until there is no obvious impurity in the washed water, the straw segments are taken out of the water and placed on a sieve to naturally drain, when there is no obvious water droplet, the straw segments are placed in an oven and dried at 60℃ for 24 hours.

[0010] Further, in S3, the straw segments after drying in S2 are crushed and passed through a 100-mesh sieve to obtain straw powder, and the straw powder is dried again in an oven at 60 DEG C until the moisture content of the straw is 3-5%, to obtain rye straw powder (RP) and oat straw powder (OP) respectively.

[0011] Further, in S4, the silane coupling agent is at least one of gamma-aminopropyl triethoxysilane and gamma-(methacryloyloxy)propyl trimethoxysilane, the coupling agent and nano-montmorillonite are added to RP and OP respectively, and a high-speed mixer is used to stir uniformly at a speed of 500-800 revolutions / minute for 15-20 minutes.

[0012] Further, in S5, the organic solvent is at least one of chloroform, toluene, and dichloromethane, the mass-volume ratio of PCL to the organic solvent is 1: (4-6) g / mL, the dissolution temperature is 25-30 DEG C, the mechanical stirring time is 20-40 minutes, and the speed is 300-600 revolutions / minute.

[0013] Further, in S6, the mechanical stirring time is 40-60 minutes, and the speed is 300-600 revolutions / minute.

[0014] Further, in S7, the composite slurry B is placed in an oven at 40 DEG C to volatilize the organic solvent, the obtained solid mixture C is cut into granules using a granulator, the shaped granules are placed at room temperature for 12 hours, and then dried in an oven at 40 DEG C for 24 hours.

[0015] Further, in S8, the process conditions for hot pressing are as follows: hot pressing temperature 110-150 DEG C, hot pressing pressure 0.8-1.5 MPa, and hot pressing time 10-20 minutes.

[0016] Further, in S9, the tensile, bending, and impact samples are respectively molded according to the standards GB / T1040.2-2022, GB / T9341-2008, and GB / T1043.1-2008, and the degradation performance is tested by the soil burial method. The present application has the following advantages

[0017] Compared with the prior art, the present application has the following advantages: 1. Resource environmental protection: using agricultural waste straw as the main raw material, the resource utilization and high-value utilization of waste are realized, which is in line with the concept of circular economy and sustainable development, and at the same time, the environmental pollution caused by traditional straw burning is reduced.

[0018] 2. Adjustable and controllable degradation: By adjusting the mass fraction of straw filler, the degradation rate of the composite material can be effectively regulated. The addition of straw provides a channel for water and microbial invasion, thereby achieving controllable design of material life and meeting the specific needs of product service life in different application scenarios.

[0019] 3. Good interface bonding: Through the process of solution blending combined with hot pressing, the uniform dispersion of straw filler in the PCL matrix is ensured. The interface interaction within the composite material is mainly achieved through hydrogen bonding and mechanical intercalation, which maintains the degradability of PCL while obtaining a stable composite structure.

[0020] 4. Simple process, easy to promote: The preparation method adopted in the present application has mild process conditions and simple operation, without the need for complex surface modification or expensive equipment, which is conducive to industrialized production and market promotion. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is the preparation flowchart of the present application; Figure 2 is the mass loss rate of materials 1-7 after degradation in the present application; Figure 3 is the change of mechanical properties of materials 1-6 after degradation in the present application; Figure 4 is the macroscopic change of the surface morphology of materials 1-7 after degradation in the present application; Figure 5 is the microscopic change of the surface morphology of materials 1-7 after degradation in the present application. DETAILED DESCRIPTION

[0022] In the following, the present application will be further described in conjunction with specific embodiments. It should be noted that the degradable biological composites based on PCL and straw filler prepared by the raw material components of Example 1, Example 2, Example 3, Example 4, Example 5, Example 6 and Example 7 are respectively material 1, material 2, material 3, material 4, material 5, material 6 and material 7. Material 7 is a control group. The following descriptions of each embodiment or each technical feature can be arbitrarily combined to form a new embodiment without conflict. The reagents or instruments used, such as without special instructions, are conventional products obtained by market purchase. Example 1

[0023] The triticale straw powder (RP) obtained by S3 was dried in an oven at 40℃ for 24 hours. Then, PCL and RP were weighed out at a mass ratio of 70:30. Next, 3 parts of coupling agent and 1 part of nano-montmorillonite were added to the RP and mixed thoroughly. Then, PCL was dissolved in an organic solvent at a mass-to-volume ratio of 1:5 and mechanically stirred at room temperature for 30 minutes until completely dissolved. After forming a homogeneous solution, the well-mixed blend of RP, coupling agent, and nano-montmorillonite was added, and stirring continued for 50 minutes to ensure uniform dispersion. The well-mixed slurry was transferred to a rectangular container and dried in an oven at 40℃ for 24 hours. After the organic solvent had completely evaporated, a solid mixture was obtained. The mixture was granulated, placed in a molding die, and hot-pressed at 120℃ and 1MPa for 15 minutes. After holding the pressure and cooling to room temperature, a composite material with a triticale straw content of 30wt.% was obtained after demolding. Example 2

[0024] The triticale straw powder (RP) obtained by S3 was dried in an oven at 40℃ for 24 hours. Then, PCL and RP were weighed out at a mass ratio of 60:40. Next, 3 parts of coupling agent and 1 part of nano-montmorillonite were added to the RP and mixed thoroughly. Then, PCL was dissolved in an organic solvent at a mass-to-volume ratio of 1:5 and mechanically stirred at room temperature for 30 minutes until completely dissolved. After forming a homogeneous solution, the well-mixed blend of RP, coupling agent, and nano-montmorillonite was added, and stirring continued for 50 minutes to ensure uniform dispersion. The well-mixed slurry was transferred to a rectangular container and dried in an oven at 40℃ for 24 hours. After the organic solvent had completely evaporated, a solid mixture was obtained. The mixture was granulated, placed in a molding die, and hot-pressed at 120℃ and 1MPa for 15 minutes. After holding the pressure and cooling to room temperature, the composite material with a triticale straw content of 40wt.% was obtained after demolding. Example 3

[0025] The triticale straw powder (RP) obtained by S3 was dried in an oven at 40℃ for 24 hours. Then, PCL and RP were weighed out at a mass ratio of 50:50. Next, 3 parts of coupling agent and 1 part of nano-montmorillonite were added to the RP and mixed thoroughly. Then, PCL was dissolved in an organic solvent at a mass-to-volume ratio of 1:5 and mechanically stirred at room temperature for 30 minutes until completely dissolved. After forming a homogeneous solution, the well-mixed blend of RP, coupling agent, and nano-montmorillonite was added, and stirring continued for 50 minutes to ensure uniform dispersion. The well-mixed slurry was transferred to a rectangular container and dried in an oven at 40℃ for 24 hours. After the organic solvent completely evaporated, a solid mixture was obtained. The mixture was granulated, placed in a molding die, and hot-pressed at 120℃ and 1MPa for 15 minutes. After holding the pressure and cooling to room temperature, the composite material with a triticale straw content of 50wt.% was obtained after demolding. Example 4

[0026] Oat straw powder (OP) obtained from S3 was dried in an oven at 40°C for 24 hours. Then, PCL and OP were weighed out at a mass ratio of 70:30. Next, 3 parts of coupling agent and 1 part of nano-montmorillonite were added to the OP and mixed thoroughly. Then, PCL was dissolved in an organic solvent at a mass-to-volume ratio of 1:5, and mechanically stirred at room temperature for 30 minutes until completely dissolved. After forming a homogeneous solution, the well-mixed blend of OP, coupling agent, and nano-montmorillonite was added, and stirring continued for 50 minutes to ensure uniform dispersion. The well-mixed slurry was transferred to a rectangular container and dried in an oven at 40°C for 24 hours. After complete evaporation of the organic solvent, a solid mixture was obtained. The mixture was granulated, placed in a molding die, and hot-pressed at 120°C and 1 MPa for 15 minutes. After holding the pressure and cooling to room temperature, a composite material with an oat straw content of 30 wt.% was obtained after demolding. Example 5

[0027] Oat straw powder (OP) obtained from S3 was dried in an oven at 40°C for 24 hours. Then, PCL and OP were weighed out at a mass ratio of 60:40. Next, 3 parts of coupling agent and 1 part of nano-montmorillonite were added to the OP and mixed thoroughly. Then, PCL was dissolved in an organic solvent at a mass-to-volume ratio of 1:5, and mechanically stirred at room temperature for 30 minutes until completely dissolved. After forming a homogeneous solution, the well-mixed blend of OP, coupling agent, and nano-montmorillonite was added, and stirring continued for 50 minutes to ensure uniform dispersion. The well-mixed slurry was transferred to a rectangular container and dried in an oven at 40°C for 24 hours. After complete evaporation of the organic solvent, a solid mixture was obtained. The mixture was granulated, placed in a molding die, and hot-pressed at 120°C and 1 MPa for 15 minutes. After holding the pressure and cooling to room temperature, a composite material with an oat straw content of 40 wt.% was obtained after demolding. Example 6

[0028] Oat straw powder (OP) obtained from S3 was dried in an oven at 40°C for 24 hours. Then, PCL and OP were weighed out at a mass ratio of 50:50. Next, 3 parts coupling agent and 1 part nano-montmorillonite were added to the OP and mixed thoroughly. Then, PCL was dissolved in an organic solvent at a mass-to-volume ratio of 1:5 and mechanically stirred at room temperature for 30 minutes until completely dissolved. After forming a homogeneous solution, the well-mixed blend of OP, coupling agent, and nano-montmorillonite was added, and stirring continued for 50 minutes to ensure uniform dispersion. The well-mixed slurry was transferred to a rectangular container and dried in an oven at 40°C for 24 hours. After complete evaporation of the organic solvent, a solid mixture was obtained. The mixture was granulated, placed in a molding die, and hot-pressed at 120°C and 1 MPa for 15 minutes. After holding the pressure and cooling to room temperature, the composite material with an oat straw content of 50 wt.% was obtained after demolding. Example 7

[0029] Without adding straw, coupling agents, or nano-montmorillonite, PCL was directly dissolved in an organic solvent at a mass-to-volume ratio of 1:5, and the subsequent steps were the same as in Example 1.

[0030] Furthermore, degradation performance tests were conducted on materials 1, 2, 3, 4, 5, 6, and 7, using the following methods: 1. The degradation performance of materials 1 to 7 was tested by the soil burial method. The material samples were buried in soil with a humidity of 40% ± 5% and cultured in a constant temperature incubator at 25℃ ± 3℃ for 60 days. After that, they were taken out, cleaned, dried, weighed and the mass loss rate was calculated. The changes in their surface morphology were observed and the degree of degradation was comprehensively evaluated.

[0031] 2. Bending properties after degradation: The test was conducted in accordance with GB / T9341-2008 using an E43.104 microcomputer-controlled electronic universal testing machine (METS Industrial Systems (China) Co., Ltd.). The test results were recorded for 5 tests and the average value was calculated.

[0032] 3. Impact strength after degradation: The test was conducted in accordance with GB / T1043.1-2008 using a G-P01 type simply supported beam impact testing machine (Kroni (Beijing) Instrument Co., Ltd.). The test results of 5 tests were recorded and the average value was calculated.

[0033] 4. Microstructure after degradation: The microstructure of the impact fracture surface and the degradation surface of the composite material was observed using a Hitachi S-3400N scanning electron microscope. All samples were subjected to gold sputtering for 60 seconds.

[0034] Furthermore, degradation test results showed that the mass loss rates of materials 1 to 6 reached 20.21%, 26.65%, 33.68%, 20.96%, 27.84%, and 36.43%, respectively, while the control group material 7 only had a loss rate of 9.19%. This indicates that the addition of straw filler significantly improved the degradation performance of the composite material.

[0035] Furthermore, the mechanical properties of the composite material gradually decreased with the extension of soil burial degradation time, indicating that under the action of soil microorganisms and water, straw and PCL matrix underwent synergistic degradation, which destroyed the molecular chain of the composite material and caused it to degrade gradually.

[0036] Furthermore, materials 1 to 6 differ in the type and ratio of straw filler, but all exhibit good degradation performance. This indicates that adjusting the type and ratio of straw within a certain range can regulate the degradation rate of the composite material to some extent, but the overall degradation performance is better than that of materials without straw. It has broad prospects in environmentally friendly packaging materials (such as express packaging boxes and cushioning pads), disposable products (such as straws and water cups), and agricultural fields (such as mulch film and transplantable seedling pots).

[0037] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A biodegradable biocomposite material based on PCL and straw filler, characterized in that, The raw materials include the following components: 30-50 parts of triticale straw, 30-50 parts of oat straw, 50-70 parts of PCL matrix, 50-70 parts of organic solvent, 3-5 parts of coupling agent, and 1-3 parts of nano-montmorillonite; the preparation method of the biodegradable biocomposite material is as follows: S1. Pre-treat the straw; S2. Place the straw sections into a washing container, stir and soak repeatedly until the distilled water is free of obvious impurities, drain the water and put it into an oven to dry. S3. After the dried straw segments are crushed and sieved, they are dried again in an oven to obtain straw powder filler. S4. Add coupling agent and nano-montmorillonite to straw powder, and after mixing, obtain blend A containing straw, coupling agent and nano-montmorillonite; S5. Dry the PCL at 40°C, dissolve the dried PCL in an organic solvent, and mechanically stir to form a homogeneous solution; S6. Add the obtained blend A to the above homogeneous solution and stir continuously to form a uniform composite slurry B. S7. Place the above composite slurry B in an oven to allow the organic solvent to evaporate completely, obtaining a solid mixture C. Granulate the material C to obtain the granules for preparing the composite material. S8. Place the above granules into the heated mold. After closing the mold, heat and press the mold in the hot press. After venting and vacuuming 1-3 times, continue to heat and pressurize for a period of time, and then keep the pressure and cool to room temperature. S9. Grind and deburr the demolded blank sample to obtain a standard sample for degradation performance testing.

2. The biodegradable biocomposite material based on PCL and straw filler according to claim 1, characterized in that: In S1, the straw includes rye straw and oat straw; the straw is cut into 10-15cm sections, and then a 6cm sieve is used to remove larger impurities present in the straw.

3. The biodegradable biocomposite material based on PCL and straw filler according to claim 1, characterized in that: In step S2, the treated straw segments are placed in a washing container, ensuring the straw is completely submerged in distilled water. The straw is stirred for 15 minutes and then soaked for another 25 minutes. The soaking water is then drained, and water is added back in. The process of stirring and soaking is repeated three times until the washing water is free of obvious impurities. The straw segments are then removed from the water and placed on a sieve to allow them to drain naturally. When no obvious water drips, the straw segments are placed in an oven and dried at 60°C for 24 hours.

4. The biodegradable biocomposite material based on PCL and straw filler according to claim 1, characterized in that: In step S3, the straw segments dried in step S2 are crushed and passed through a 100-mesh sieve to obtain straw powder. The straw powder is then dried again in an oven at 60°C until the straw moisture content is 3%-5%, thereby obtaining triticale straw powder (RP) and oat straw powder (OP).

5. The biodegradable biocomposite material based on PCL and straw filler according to claim 1, characterized in that: In S4, the silane coupling agent is at least one of γ-aminopropyltriethoxysilane and γ-(methacryloyloxy)propyltrimethoxysilane. The coupling agent and nano-montmorillonite are added to RP and OP respectively, and then stirred evenly using a high-speed mixer at a speed of 500-800 rpm for 15-20 minutes.

6. The biodegradable biocomposite material based on PCL and straw filler according to claim 1, characterized in that: In S5, the organic solvent is at least one of chloroform, toluene, and dichloromethane, the mass-to-volume ratio of PCL to the organic solvent is 1:(4-6) g / mL, the dissolution temperature is 25-30℃, the mechanical stirring time is 20-40 minutes, and the stirring speed is 300-600 rpm.

7. The biodegradable biocomposite material based on PCL and straw filler according to claim 1, characterized in that: In S6, the mechanical stirring time is 40-60 minutes and the rotation speed is 300-600 rpm.

8. The biodegradable biocomposite material based on PCL and straw filler according to claim 1, characterized in that: In S7, the organic solvent of the composite slurry B is evaporated in an oven at 40°C, and the resulting solid mixture C is pelletized by a pelletizer. The shaped pellets need to be placed at room temperature for 12 hours and then dried in an oven at 40°C for 24 hours.

9. The biodegradable biocomposite material based on PCL and straw filler according to claim 1, characterized in that: In S8, the hot pressing process conditions are: hot pressing temperature 110-150℃, hot pressing pressure 0.8-1.5MPa, and hot pressing time 10-20 minutes.

10. The biodegradable biocomposite material based on PCL and straw filler according to claim 1, characterized in that: In S9, the tensile, bending, and impact specimens are molded according to the standards GB / T1040.2-2022, GB / T9341-2008, and GB / T1043.1-2008, respectively. Degradation performance was tested using the soil burial method.

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