Preparation method of high-strength antibacterial degradable bamboo fiber / polylactic acid bamboo-plastic composite material

Abstract

The invention provides a preparation method of a high-strength antibacterial degradable bamboo fiber / polylactic acid bamboo-plastic composite material, which comprises the following steps: preparing bamboo fibers, preparing a PDMS (Polydimethylsiloxane)-SiO2 mixed modifier, preparing PDMS-SiO2 modified bamboo fibers, preparing a ZnO-containing suspension, preparing nano ZnO modified bamboo fibers, preparing a master batch, and carrying out compression molding. The high-strength antibacterial degradable bamboo fiber / polylactic acid bamboo-plastic composite material is obtained. The prepared bamboo-plastic composite material can prolong the service life and has good antibacterial performance.

Description

Technical Field

[0001] The invention belongs to the technical field of bamboo-plastic composite material processing, and in particular relates to a method for preparing a high-strength antibacterial and degradable bamboo fiber / polylactic acid bamboo-plastic composite material. Background Art

[0002] Natural plant fiber reinforced polymer materials are environmentally friendly, non-toxic and renewable. Polylactic acid (PLA) is a biodegradable polyester whose raw materials mainly come from renewable materials such as corn, cassava, and sugarcane. It can eliminate or alleviate the pollution of plastics to the environment, but PLA's own shortcomings such as high cost and poor toughness limit its application.

[0003] As a kind of natural plant fiber, bamboo fiber has the characteristics of rich resources, short growth cycle, high strength and good toughness. Using bamboo fiber in the manufacture of PLA composite materials can not only reduce costs, but also effectively improve the performance of composite materials. However, bamboo fiber contains substances such as sugars and water, which provide breeding conditions for microorganisms such as bacteria. Therefore, it is easily contaminated by them, which damages its various properties and seriously affects its utilization value. Bamboo fiber contains more polar hydroxyl and phenolic hydroxyl functional groups. When blended with hydrophobic material PLA, the interfacial bonds are often weak, exposing some of its components to the outside, providing a carbon source for microorganisms, resulting in damage to the mechanical properties of the composite material.

[0004] Traditional antibacterial treatment methods mostly use chemical agents, which often contain harmful substances, which not only threaten human health, but also easily pollute the environment. Existing antibacterial treatment technologies are difficult to maintain antibacterial properties for a long time. The antibacterial effect of the material will be significantly weakened after a certain period of time, affecting the service life of the material. Although many antibacterial technologies can have a certain effect, they often affect the mechanical properties of the material, or quickly fail in harsh environments, causing the composite material to age and break easily in long-term applications, which seriously restricts the development of bamboo plastic materials. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing a high-strength antibacterial and degradable bamboo fiber / polylactic acid bamboo-plastic composite material in view of the deficiencies of the above-mentioned prior art. The bamboo-plastic composite material prepared by the method can extend the service life and has good antibacterial properties.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing a high-strength antibacterial and degradable bamboo fiber / polylactic acid bamboo plastic composite material, the method comprising:

[0007] S1. Preparation of bamboo fiber:

[0008] Select 3-5 year old bamboo, cut bamboo material with a length of 2m and a height of 1m above the ground, remove the green bamboo and yellow bamboo, split into bamboo strips with a width of 10mm, roll and crush, and dry at a temperature of 90℃ to obtain dried bamboo fiber;

[0009] S2. Preparation of PDMS-SiO 2 Mixed modifier:

[0010] Mixing polydimethylsiloxane and ethyl acetate to obtain a PDMS solution;

[0011] Mix ethyl orthosilicate, methanol and ethanol to obtain SiO 2 Sol;

[0012] The PDMS solution and the SiO 2 Sol mixing to obtain PDMS-SiO 2 Modifiers;

[0013] S3. Preparation of PDMS-SiO 2 Modified bamboo fiber:

[0014] The dried bamboo fiber obtained in S1 was immersed in the PDMS-SiO 2 The modified agent was stirred at room temperature, and then allowed to stand until the solvent evaporated, and then filtered, washed, and vacuum dried to obtain PDMS-SiO 2 Modified bamboo fiber;

[0015] S4. Preparation of a ZnO-containing suspension:

[0016] adding polyethyleneimine and ZnO nanoparticles into methanol to obtain a suspension containing ZnO;

[0017] S5. Preparation of nano ZnO modified bamboo fiber:

[0018] The PDMS-SiO 2 The modified bamboo fiber is immersed in the ZnO-containing suspension obtained in S4, and then a silane coupling agent is added, and the mixture is stirred at room temperature. After stirring, the mixture is allowed to stand until the solvent evaporates, and then filtered, washed, and vacuum dried to obtain PDMS-SiO 2 -ZnO modified bamboo fiber;

[0019] S6. Preparation of masterbatch:

[0020] The PDMS-SiO 2 -ZnO modified bamboo fiber and polylactic acid are mixed, dried at 90°C for 24 hours, crushed to obtain a powdered mixture, placed in a twin-screw extruder for melt extrusion, water-cooled, pelletized, and dried to obtain a masterbatch;

[0021] S7, Compression molding:

[0022] The masterbatch obtained in S6 is heated to a molten state, injected into a mold for hot pressing, cooled, dried at room temperature, polished, edge trimmed, and assembled to obtain a high-strength antibacterial and degradable bamboo fiber / polylactic acid bamboo plastic composite material.

[0023] Preferably, the rolling gap in S1 is 2 mm, the crushing speed is 32000 r / min; the mesh size of the bamboo fiber after drying in S1 is 60-100 mesh; and the moisture content of the bamboo fiber after drying is less than 3%.

[0024] Preferably, the mass ratio of polydimethylsiloxane to ethyl acetate in the PDMS solution in S2 is 1:10; 2 The mass ratio of ethyl orthosilicate, methanol and ethanol in the sol is 1:10:15; the PDMS-SiO 2 PDMS solution and SiO in the modifier 2 The mass ratio of the sol is 1:1.

[0025] Preferably, the stirring rate in S3 and S5 is 300 rpm, and the stirring time is 2 h; the vacuum drying conditions in S3 and S5 are: drying in a vacuum drying oven at a temperature of 90° C. for 24 h.

[0026] Preferably, the mass ratio of polyethyleneimine, ZnO nanoparticles and methanol in the ZnO-containing suspension in S4 is 1:1:10.

[0027] Preferably, the PDMS-SiO 2 The mass ratio of the modified bamboo fiber, the ZnO-containing suspension and the silane coupling agent is 1:10:(1-2); the model of the silane coupling agent is KH550.

[0028] Preferably, the PDMS-SiO 2 -The mass ratio of ZnO modified bamboo fiber and polylactic acid is 3:7.

[0029] Preferably, the feed rate of the twin-screw extruder in S6 is 120 g / min, the temperature is heated to 180°C, the screw speed is 100 r / min to 200 r / min; the aspect ratio of the masterbatch is 32:1; and the drying conditions are: drying at 80°C for 8 hours.

[0030] Preferably, the hot pressing conditions in S6 are: hot pressing at a temperature of 150° C. to 200° C. and a pressure of 15 MPa to 18 MPa for 10 min to 20 min.

[0031] Preferably, the high-strength antibacterial and degradable bamboo fiber / polylactic acid bamboo plastic composite material described in S6 has a tensile strength of 40.08 MPa to 41.08 MPa, a flexural strength of 85.51 MPa to 89.51 MPa, and an impact strength of 4.56 MPa to 4.84 MPa.

[0032] The present invention proposes a solution to solve the problem that the bamboo-plastic material has poor interface compatibility and is susceptible to microbial contamination such as bacteria. First, the bamboo fiber is impregnated with polydimethylsiloxane (PDMS)-silicon dioxide (SiO 2 ) modifier (PDMS molecules can fill the microcracks and pores on the surface of bamboo fibers and improve their structural uniformity. The methyl (-CH 3 ) groups cover the surface of bamboo fiber, which can reduce its surface free energy; silicon dioxide has a high specific surface area and porous structure, forming a micro-nano rough structure on the surface of bamboo fiber); then ZnO nanoparticles are added to methanol to prepare a ZnO-containing suspension, in which polyethyleneimine (PEI) is added as a dispersant. The active oxygen generated on the surface of ZnO nanoparticles destroys the cell membrane of bacteria, inhibits their metabolic function, and gives the material antibacterial properties; PEI is a water-soluble polymer, and its amine group is protonated in aqueous solution to form -NH 3 + , destroying the integrity of bacterial cell membranes through electrostatic adsorption, enhancing its antibacterial effect; it can also be adsorbed to the surface of ZnO particles through hydrogen bonds or electrostatic effects, forming a stable polymer protective layer on the surface to prevent direct contact between particles, thereby reducing agglomeration and enhancing the particle stability of the suspension by increasing the zeta potential). The modified bamboo fiber was immersed in the above solution, and the silane coupling agent KH550 was added as a coupling agent. The Si-OH produced by the hydrolysis of KH550 can react with the -OH on the surface of the nanoparticles to form a covalent bond, which is used as a bridge between the organic polymer and the nanoparticles, enhancing the interfacial bonding effect between the bamboo fiber and polylactic acid (PLA), and reducing the surface hydrophilicity of the inorganic material. Finally, PDMS-SiO 2 -ZnO modified bamboo fiber and PLA were placed in a twin-screw extruder and blended to obtain an antibacterial and degradable bamboo-plastic composite material with good interface compatibility.

[0033] Compared with the prior art, the present invention has the following advantages:

[0034] 1. The present invention uses polydimethylsiloxane (PDMS), zinc oxide nanoparticles (ZnO) and silicon dioxide (SiO 2 ) and other environmentally friendly and non-toxic materials to reduce harmful effects on the human body and the environment, making the preparation process greener and safer. 2The modifier is used to modify the bamboo fiber, improve the interface strength between the bamboo fiber and the plastic, and significantly improve the water resistance, wear resistance and mechanical strength of the material, so that it can still maintain excellent performance in a humid or high temperature environment, avoiding aging or damage to the material. The antibacterial function of the bamboo fiber is modified by a suspension containing ZnO, and the antibacterial properties of the bamboo plastic material are enhanced, so that it can effectively inhibit the growth of bacteria during use and extend the service life. PEI (polyethyleneimine) is added as a dispersant to improve the dispersion and uniformity of ZnO on the surface of the bamboo fiber and enhance the antibacterial ability of the material; Silane coupling agent is added as a coupling agent to ensure that the polarity difference between the bamboo fiber and polylactic acid (PLA) is reduced, and the interface stress of the prepared composite material is the same in all directions, ensuring the interface strength and mechanical stability of the bamboo plastic material.

[0035] 2. The preparation process of the present invention is simple, does not involve complicated operations, and the selected reagents are all environmentally friendly and non-toxic materials. The prepared high-strength antibacterial and degradable bamboo fiber / polylactic acid bamboo plastic composite material can significantly extend the service life and has excellent antibacterial properties. The present invention has significant advantages in environmental performance, antibacterial efficiency and durability, and has opened up a new direction for the application of bamboo plastic composite materials.

[0036] The present invention is further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a scanning electron microscope image and an EDS element distribution map of the bamboo-plastic composite material prepared in Example 1 of the present invention.

[0038] Figure 2 This is the X-ray diffraction pattern (XRD) of the bamboo-plastic composite material prepared in Example 1 of the present invention.

[0039] Figure 3 This is the infrared spectrum (FTIR) of the bamboo-plastic composite material prepared in Example 1 of the present invention.

[0040] Figure 4 This is a graph showing the antibacterial test of the bamboo-plastic composite material prepared in Example 1 of the present invention against Staphylococcus aureus. DETAILED DESCRIPTION

[0041] Example 1

[0042] The preparation method of the high-strength antibacterial and degradable bamboo fiber / polylactic acid bamboo plastic composite material (mouse) of this embodiment is as follows:

[0043] S1. Preparation of bamboo fiber:

[0044] A 3-year-old bamboo is selected, and a bamboo material with a length of 2m and a height of 1m above the ground base is cut, and the green bamboo and the yellow bamboo are planed off, and the bamboo strips with a width of 10mm are split, and the strips are crushed after rolling, and dried at a temperature of 90°C to obtain a dried bamboo fiber with a moisture content of less than 3% (the moisture content of the dried bamboo fiber in this embodiment is 2.5%); the mesh number of the dried bamboo fiber is 60-100 mesh; the rolling gap is 2mm, and the crushing speed is 32000r / min;

[0045] S2. Preparation of PDMS-SiO 2 Mixed modifier:

[0046] Mixing polydimethylsiloxane (PDMS) and ethyl acetate to obtain a PDMS solution;

[0047] Tetraethyl orthosilicate (TEOS), methanol and ethanol were mixed to obtain SiO 2 Sol;

[0048] The PDMS solution and the SiO 2 Sol mixing to obtain PDMS-SiO 2 Modifier; the mass ratio of polydimethylsiloxane and ethyl acetate in the PDMS solution is 1:10; the SiO 2 The mass ratio of ethyl orthosilicate, methanol and ethanol in the sol is 1:10:15; the PDMS-SiO 2 PDMS solution and SiO in the modifier 2 The mass ratio of the sol is 1:1;

[0049] S3. Preparation of PDMS-SiO 2 Modified bamboo fiber:

[0050] The dried bamboo fiber obtained in S1 was immersed in the PDMS-SiO 2 The modified agent was stirred at room temperature at a stirring rate of 300 rpm for 2 h, and then allowed to stand until the solvent evaporated, and then filtered, washed, and dried in a vacuum drying oven at a temperature of 90 ° C for 24 h to obtain PDMS-SiO 2 Modified bamboo fiber;

[0051] Modifying silica with PDMS and filling it on the surface of bamboo fiber can improve the structural uniformity. The methyl group (-CH 3 ) groups, after covering the surface of bamboo fiber, can reduce its surface polarity and effectively improve its interface strength with polylactic acid matrix. 2 The Si-O-Si covalent bonds of the nanoparticles can improve the dispersibility of the nanoparticles, reduce their mobility and aggregation tendency, and provide conditions for the subsequent attachment of inorganic antibacterial nanoparticles.

[0052] S4. Preparation of a ZnO-containing suspension:

[0053] Adding PEI (polyethyleneimine) and ZnO nanoparticles into methanol to obtain a ZnO-containing suspension; the mass ratio of PEI, ZnO nanoparticles and methanol in the ZnO-containing suspension is 1:1:10;

[0054] S5. Preparation of nano ZnO modified bamboo fiber:

[0055] The PDMS-SiO 2 The modified bamboo fiber was immersed in the ZnO-containing suspension obtained in S4, and then the silane coupling agent KH550 was added, and the mixture was stirred at a stirring rate of 300 rpm for 2 h at room temperature. After the stirring was completed, the mixture was allowed to stand until the solvent evaporated, and then filtered, washed, and dried in a vacuum drying oven at a temperature of 90 °C for 24 h to obtain PDMS-SiO 2 -ZnO modified bamboo fiber; the PDMS-SiO 2 The mass ratio of modified bamboo fiber, ZnO-containing suspension and silane coupling agent KH550 is 1:10:1;

[0056] The positive charge on the surface of zinc oxide nanoparticles can adsorb bacterial cell membranes and destroy their structure, leading to bacterial death. On the other hand, they can produce reactive oxygen species (ROS), causing lipid peroxidation of bacterial membranes, inhibiting transmembrane respiration and leakage of substances within bacteria, further enhancing the antibacterial effect. Polyethyleneimine (PEI) is introduced as a dispersant. PEI is a water-soluble polymer whose amine groups are protonated in aqueous solution to form –NH 3 + , destroying the integrity of bacterial cell membranes through electrostatic adsorption, thus enhancing its antibacterial effect; in addition, it can be adsorbed to the surface of ZnO particles through hydrogen bonding or electrostatic action, forming a stable polymer protective layer on the surface to prevent direct contact between particles, thereby reducing agglomeration and enhancing the particle stability of the suspension by increasing the zeta potential; KH550 coupling agent helps to enhance the SiO 2 , the bonding force between ZnO composite particles and bamboo fiber substrate, thereby preparing a bamboo-plastic composite material with chemical stability, mechanical stability and antibacterial properties.

[0057] S6. Preparation of masterbatch:

[0058] The PDMS-SiO 2 -ZnO modified bamboo fiber (abbreviated as BF-PDMS-SiO 2-ZnO) and polylactic acid (PLA) were mixed, dried at 90°C for 24 hours, crushed to obtain a powdered mixture, placed in a twin-screw extruder for melt extrusion, water-cooled, pelletized, and dried at 80°C for 8 hours to obtain a masterbatch with an aspect ratio of 32:1; the PDMS-SiO 2 -The mass ratio of ZnO modified bamboo fiber to polylactic acid is 3:7; the feeding speed of the twin-screw extruder is 120 g / min, the temperature is heated to 180°C, and the screw speed is 100 r / min;

[0059] S7, Compression molding:

[0060] The masterbatch obtained in S6 was heated to a molten state, injected into a mold, and hot-pressed for 20 min at a temperature of 150°C and a pressure of 18 MPa. After cooling, it was dried at room temperature, polished, edge-trimmed, and assembled to obtain a high-strength antibacterial and degradable bamboo fiber / polylactic acid bamboo plastic composite material (high-strength antibacterial and degradable bamboo plastic mouse, denoted as PDMS-SiO 2 -ZnO / BF-PLA).

[0061] The prepared bamboo plastic products have a stable and uniform structure and uniform distribution of tension in all directions, thus avoiding quality defects that may occur during the processing and use of the materials.

[0062] The high-strength antibacterial and degradable bamboo fiber / polylactic acid bamboo plastic composite material (PDMS-SiO 2 -ZnO / BF-PLA) for performance testing, and PDMS-SiO 2 / BF-PLA and BF-PLA were used as controls.

[0063] PDMS-SiO 2 The preparation method of / BF-PLA is:

[0064] S1. Preparation of bamboo fiber:

[0065] A 3-year-old bamboo is selected, and a bamboo material with a length of 2m and a height of 1m above the ground base is cut, and the green bamboo and the yellow bamboo are planed off, and the bamboo strips with a width of 10mm are split, and the bamboo strips are crushed after rolling, and the bamboo fiber with a moisture content of less than 3% is obtained under the condition of a temperature of 90°C (the moisture content of the dried bamboo fiber in this embodiment is 2.8%); the mesh number of the dried bamboo fiber is 60-100 mesh; the rolling gap is 2mm, and the crushing speed is 32000r / min;

[0066] S2. Preparation of PDMS-SiO 2 Mixed modifier:

[0067] Mixing polydimethylsiloxane (PDMS) and ethyl acetate to obtain a PDMS solution;

[0068] Tetraethyl orthosilicate (TEOS), methanol and ethanol were mixed to obtain SiO 2 Sol;

[0069] The PDMS solution and the SiO 2 Sol mixing to obtain PDMS-SiO 2 Modifier; the mass ratio of polydimethylsiloxane and ethyl acetate in the PDMS solution is 1:10; the SiO 2 The mass ratio of ethyl orthosilicate, methanol and ethanol in the sol is 1:10:15; the PDMS-SiO 2 PDMS solution and SiO in the modifier 2 The mass ratio of the sol is 1:1;

[0070] S3. Preparation of PDMS-SiO 2 Modified bamboo fiber:

[0071] The dried bamboo fiber obtained in S1 was immersed in the PDMS-SiO 2 The modified agent was stirred at room temperature at a stirring rate of 300 rpm for 2 h, and then allowed to stand until the solvent evaporated, and then filtered, washed, and dried in a vacuum drying oven at a temperature of 90 ° C for 24 h to obtain PDMS-SiO 2 Modified bamboo fiber (abbreviated as BF-PDMS-SiO 2 );

[0072] S4. Preparation of masterbatch:

[0073] The BF-PDMS-SiO 2 After mixing with polylactic acid (PLA), the mixture was dried at 90°C for 24 hours, crushed to obtain a powdered mixture, melt-extruded in a twin-screw extruder, water-cooled, pelletized, and dried at 80°C for 8 hours to obtain a masterbatch with an aspect ratio of 32:1. 2 The mass ratio of polylactic acid to polylactic acid is 3:7; the feed rate of the twin-screw extruder is 120 g / min, the temperature is heated to 180° C., and the screw speed is 100 r / min;

[0074] S5, Compression molding:

[0075] The masterbatch obtained in S4 was heated to a molten state, injected into a mold, and hot-pressed for 20 min at a temperature of 150 °C and a pressure of 18 MPa. After cooling, it was dried at room temperature, polished, edge trimmed, and assembled to obtain a bamboo-plastic composite material, which was recorded as PDMS-SiO2 / BF-PLA.

[0076] The preparation method of BF-PLA is:

[0077] S1. Preparation of bamboo fiber:

[0078] A 3-year-old bamboo is selected, and bamboo material with a length of 2m and a height of 1m above the ground base is cut, and the green bamboo and the yellow bamboo are planed off, and the bamboo strips with a width of 10mm are split, and the strips are crushed after rolling, and dried bamboo fiber with a moisture content of less than 3% is obtained under the condition of a temperature of 90°C; the mesh number of the dried bamboo fiber is 60-100 meshes; the rolling gap is 2mm, and the crushing speed is 32000r / min, and the obtained bamboo fiber is recorded as BF;

[0079] S2. Preparation of masterbatch:

[0080] The bamboo fiber obtained in S1 and polylactic acid (PLA) are mixed, dried at 90°C for 24 hours, crushed to obtain a powdered mixture, placed in a twin-screw extruder for melt extrusion, water-cooled, pelletized, and dried at 80°C for 8 hours to obtain a masterbatch with an aspect ratio of 32:1; the mass ratio of the bamboo fiber to the polylactic acid is 3:7; the feed rate of the twin-screw extruder is 120g / min, the temperature is heated to 180°C, and the screw speed is 100r / min;

[0081] S3, Compression molding:

[0082] The masterbatch obtained in S2 was heated to a molten state, injected into a mold, and hot-pressed for 20 minutes at a temperature of 150°C and a pressure of 18 MPa. After cooling, it was dried at room temperature, polished, edge-trimmed, and assembled to obtain a bamboo-plastic composite material, recorded as BF-PLA.

[0083] PDMS-SiO 2 -ZnO / BP-PLA, PDMS-SiO 2 / BF-PLA and BF-PLA were tested as follows:

[0084] (I) Performance test:

[0085] Tensile properties: refer to ASTM D638 standard, test rate is 5mm / min;

[0086] Bending performance: refer to ASTM D790-03 standard, the test rate is 2mm / min;

[0087] Impact performance: according to the standard, the V-notch depth is 0.8mm and the pendulum impact energy is 15J; the specific test data are shown in Table 1:

[0088] Table 1 Performance test

[0089] Test items <![CDATA[PDMS-SiO 2 -ZnO / BF-PLA]]> <![CDATA[PDMS-SiO 2 / BF-PLA]]> BF-PLA Tensile strength(MPa) 41.08 37.35 29.36 Tensile modulus(GPa) 2.07 1.69 1.41 Bending strength(MPa) 89.51 84.63 71.35 Flexural modulus(GPa) 2.94 2.66 2.31 Impact strength(MPa) 4.56 5.55 4.07 Tensile break rate (%) 23.12 18.88 17.04

[0090] The static mechanical properties of the prepared bamboo-plastic composite fiber before and after modification are shown in Table 1, including flexural strength and modulus, tensile strength and modulus, impact strength and elongation at break. Compared with the unmodified BF-PLA, the modified BF-PLA fiber after PDMS and SiO 2 Modified composite material PDMS-SiO 2 The flexural strength and flexural modulus, tensile strength and tensile modulus, impact strength and elongation at break of / BF-PLA increased by 18.61% and 15.15%, 27.21% and 19.86%, 36.36% and 10.80%, respectively, indicating that PDMS and SiO 2 The modified BF significantly improved its interfacial compatibility with PLA, and the PDMS interacted with the bamboo fiber through hydrogen bonding, which reduced the surface polarity and improved its dispersibility in the polymer matrix. 2 The connection bridge between the nanoparticles and BF successfully constructed a micro-nanostructure on the BF surface, increased the roughness of the BF surface, and enhanced the mechanical meshing between BF and PLA matrix. 2 The micro-nanostructure has a large specific surface area and high specific surface energy, so BF has a strong bonding force with the polymer matrix. Under the action of external force, a stress concentration effect is generated, thereby absorbing more energy. 2 It has special characteristics such as small size, surface, optical and macroscopic quantum size effects, resulting in nanoscale effects, large specific surface area and strong interface bonding effects. 2 Modified BF realizes the construction of a two-phase compatible interface, making PDMS-SiO 2 / BF-PLA's tensile strength and flexural strength are improved.

[0091] After the introduction of KH550 silanized ZnO, the PDMS-SiO 2 The flexural strength and flexural modulus, tensile strength and tensile modulus, impact strength and tensile fracture rate of ZnO / BF-PLA increased by 25.45% and 27.27%, 39.92% and 46.81%, and 12.04% and 35.68%, respectively. The significant improvement in its mechanical properties is attributed to the uniform dispersion of ZnO nanoparticles as rigid particles on the surface of BF, and the rich hydroxyl groups in its structure enhance the interaction between BF and the polymer matrix, thus showing better tensile and flexural properties.

[0092] (ii) Scanning electron microscope (SEM):

[0093] The surface morphology of bamboo fibers before and after modification was observed by scanning electron microscopy (SEM), and the elemental composition of the sample surface was analyzed by energy dispersive spectroscopy (EDS). Figure 1 shown.

[0094] Figure 1 ad are the SEM images of BF at 100μm, 50μm and 5μm magnifications and the distribution of different elements (C, O, Si, Zn). Its surface is relatively smooth, and the interweaving of fiber bundles can be clearly seen. Bamboo fiber is mainly composed of cellulose, hemicellulose and lignin, and the surface is covered with tiny fibers, starch and other impurities. Therefore, from the EDS mapping, C and O elements were mainly detected from the surface of BF.

[0095] Figure 1 eh is 100μm, 50μm and 5μm respectively. 2 The (unified concept) SEM images and distribution diagrams of different elements (C, O, Si, Zn) are shown in Figure 2. 2 After modification, it can be observed that the surface of bamboo fiber is covered with a rough coating, which fills the gaps between fibers. This indicates that PDMS spontaneously forms an ordered structure on the surface of BF and is combined with SiO 2 A micro-nano structure is formed, and protrusions of different sizes appear on the surface, thereby increasing the surface roughness.

[0096] Figure 1 il are 100μm, 50μm and 5μm respectively. 2 -ZnO scanning electron microscope image and distribution of different elements (C, O, Si, Zn). After introducing KH550 silanized nano ZnO and adding PEI as a dispersant, the surface roughness of BF is further enhanced, the coating is more uniform and smooth, and ZnO particles can be observed to be evenly distributed on its surface. This is because PEI has rich amino groups (-NH 2 ) coordinates with ZnO, changing its surface energy order to form a uniform and ordered structure, and the Si-OH produced by the hydrolysis of the silane coupling agent KH550 can react with the -OH on the surface of the nanoparticles to form a covalent bond, enhancing its stability.

[0097] (III) X-ray diffraction pattern (XRD)

[0098] like Figure 2 As shown in the XRD spectrum of untreated BF, two peaks can be observed at 17° and 22.5°, which belong to the crystalline region of cellulose and correspond to the (110) and (200) crystal planes, respectively. 2After treatment, BF-PDMS-SiO 2 The XRD spectrum of PDMS-SiO 2 The synthesis process of modified bamboo fiber does not affect its crystal structure. The very weak peak at 20°-30° can be characterized as amorphous SiO 2 After the introduction of ZnO, it can be observed that BF-PDMS-SiO 2 -ZnO XRD spectrum showed new peaks at 32°, 34° and 36°, which can be attributed to the diffraction of ZnO (100), (002) and (101) crystal planes, indicating that ZnO was successfully deposited on the surface of bamboo fiber. The crystallinity (CrI) of the modified fibers was improved, indicating that the PDMS, SiO 2 The modification of nano ZnO can effectively remove the amorphous part of the fiber. Studies have shown that natural fibers with high crystallinity can help enhance the interfacial bonding between them and the polymer matrix.

[0099] (IV) Infrared spectroscopy analysis (FTIR)

[0100] The chemical structure of the BF surface before and after modification was studied by FTIR, such as Figure 3 As shown. At 3430cm -1 A broad band was observed near the α-hydroxyl group, which belongs to the stretching vibration of –OH and –NH in bamboo fiber. 2 At 2960cm -1 The new absorption vibration peak that appears near -CH 3 The asymmetric stretching vibration at 2900 cm -1 The absorption peak signal enhancement at -CH 3 and -CH 2 Symmetric stretching vibration at 1263cm -1 The enhanced absorption peak signals on the left and right can be attributed to -CH 3 The deformation vibration of PDMS is also a characteristic peak of PDMS. In addition, the Si-O bond at 808 cm -1 The characteristic absorption peak near SiO 2 The particles are connected to PDMS through Si-O bonds. It is worth noting that when the silane coupling agent KH550 and nano-ZnO are introduced, the BF-PDMS-SiO 2 -ZnO absorption peaks are increased to a greater extent. Specifically, nano-ZnO has a peak absorption of 3430 cm -1 and 2900cm -1The absorption peak signal at 440cm-1 is significantly enhanced, mainly due to the bending vibration of -OH on the surface of nano-ZnO. The characteristic ultraviolet absorption peak of nano-ZnO is around 440cm-1, indicating that nano-ZnO forms Si-O-Zn bonds with KH550 through dehydration condensation of -OH on the surface, making nano-ZnO uniformly modified on the BF surface.

[0101] (V) Antibacterial performance test

[0102] The antibacterial properties of the prepared bamboo-plastic composite material were tested for 60 days according to GB / T 31402-2015. Figure 4 It can be seen that after being cultured in a constant temperature incubator, the antibacterial ability of the bamboo-plastic composite material before and after modification was observed. After 24 hours of constant temperature and humidity culture, the antibacterial performance of pure PLA material was almost 0, and no antibacterial circle was produced around the composite material; similarly, no antibacterial circle was produced in the culture dish where BF-PLA was placed, indicating that it had no antibacterial ability; PDMS-SiO 2 -ZnO / BF-PLA showed an obvious inhibition zone within 60 days, and its diameter reached 5.25±0.26mm, indicating that PDMS-SiO 2 -ZnO / BF-PLA has a long-term and efficient antibacterial ability against Staphylococcus aureus, which is due to the good bactericidal ability of ZnO nanoparticles loaded on the surface of BF. ZnO nanoparticles generate electron-hole pairs under light, which react with water and oxygen to generate hydroxyl radicals (·OH), superoxide anions (O 2 - ) and hydrogen peroxide (H 2 O 2 ) and other reactive oxygen species (ROS), which damage bacterial cell membranes, proteins and DNA, leading to bacterial death; at the same time, the ZnO 2+ It can penetrate the cell membrane and bind to DNA, causing breakage or damage, thereby hindering bacterial replication and transcription.

[0103] Example 2

[0104] The preparation method of the high-strength antibacterial and degradable bamboo fiber / polylactic acid bamboo plastic composite material (keyboard) of this embodiment is as follows:

[0105] S1. Preparation of bamboo fiber:

[0106] Select 5-year-old bamboo, cut the bamboo material with a length of 2m above the ground foundation of 1m, planed off the green bamboo and yellow bamboo, split into bamboo strips with a width of 10mm, rolled and crushed, and dried at a temperature of 90℃ to obtain dried bamboo fiber with a moisture content of less than 3%; the mesh number of the dried bamboo fiber is 60-100 mesh; the rolling gap is 2mm, and the crushing speed is 32000r / min;

[0107] S2. Preparation of PDMS-SiO 2 Mixed modifier:

[0108] Mixing polydimethylsiloxane and ethyl acetate to obtain a PDMS solution;

[0109] Mix ethyl orthosilicate, methanol and ethanol to obtain SiO 2 Sol;

[0110] The PDMS solution and the SiO 2 Sol mixing to obtain PDMS-SiO 2 Modifier; the mass ratio of polydimethylsiloxane and ethyl acetate in the PDMS solution is 1:10; the SiO 2 The mass ratio of ethyl orthosilicate, methanol and ethanol in the sol is 1:10:15; the PDMS-SiO 2 PDMS solution and SiO in the modifier 2 The mass ratio of the sol is 1:1;

[0111] S3. Preparation of PDMS-SiO 2 Modified bamboo fiber:

[0112] The dried bamboo fiber obtained in S1 was immersed in the PDMS-SiO 2 The modified agent was stirred at room temperature at a stirring rate of 300 rpm for 2 h, and then allowed to stand until the solvent evaporated, and then filtered, washed, and dried in a vacuum drying oven at a temperature of 90 ° C for 24 h to obtain PDMS-SiO 2 Modified bamboo fiber;

[0113] S4. Preparation of a ZnO-containing suspension:

[0114] Adding PEI (polyethyleneimine) and ZnO nanoparticles into methanol to obtain a ZnO-containing suspension; the mass ratio of PEI, ZnO nanoparticles and methanol in the ZnO-containing suspension is 1:1:10;

[0115] S5. Preparation of nano ZnO modified bamboo fiber:

[0116] The PDMS-SiO 2 The modified bamboo fiber was immersed in the ZnO-containing suspension obtained in S4, and then the silane coupling agent KH550 was added, and the mixture was stirred at a stirring rate of 300 rpm for 2 h at room temperature. After the stirring was completed, the mixture was allowed to stand until the solvent evaporated, and then filtered, washed, and dried in a vacuum drying oven at a temperature of 90 °C for 24 h to obtain PDMS-SiO 2 -ZnO modified bamboo fiber; the PDMS-SiO2 The mass ratio of modified bamboo fiber, ZnO-containing suspension and silane coupling agent KH550 is 1:10:2;

[0117] S6. Preparation of masterbatch:

[0118] The PDMS-SiO 2 -ZnO modified bamboo fiber and polylactic acid were mixed, dried at 90°C for 24 hours, crushed to obtain a powdered mixture, placed in a twin-screw extruder for melt extrusion, water-cooled, pelletized, and dried at 80°C for 8 hours to obtain a masterbatch with an aspect ratio of 32:1; the PDMS-SiO 2 -The mass ratio of ZnO-modified bamboo fiber to polylactic acid is 3:7; the feeding speed of the twin-screw extruder is 120 g / min, the temperature is heated to 180°C, and the screw speed is 200 r / min;

[0119] S7, Compression molding:

[0120] The masterbatch obtained in S6 is heated to a molten state, injected into a mold, and hot-pressed for 10 minutes at a temperature of 200°C and a pressure of 15 MPa. After cooling, it is dried at room temperature, polished, edge-trimmed, and assembled to obtain a high-strength antibacterial and degradable bamboo fiber / polylactic acid bamboo-plastic composite material (a high-strength antibacterial and degradable bamboo-plastic keyboard).

[0121] The high-strength antibacterial and degradable bamboo fiber / polylactic acid bamboo plastic composite material prepared in this embodiment has a tensile strength of 40.08 MPa, a tensile modulus of 2.50 GPa, a flexural strength of 85.51 MPa, a flexural modulus of 2.85 GPa, an impact strength of 4.84 MPa, and a tensile fracture rate of 24.12%.

[0122] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiment according to the technical essence of the invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a high-strength antibacterial and degradable bamboo fiber / polylactic acid bamboo plastic composite material, characterized in that: The method is: S1. Preparation of bamboo fiber: Select 3-5 year old bamboo, cut bamboo material with a length of 2m and a height of 1m above the ground, remove the green bamboo and yellow bamboo, split into bamboo strips with a width of 10mm, roll and crush, and dry at a temperature of 90℃ to obtain dried bamboo fiber; S2. Preparation of PDMS-SiO2 mixed modifier: Mixing polydimethylsiloxane and ethyl acetate to obtain a PDMS solution; Mixing tetraethyl orthosilicate, methanol and ethanol to obtain SiO2 sol; Mixing the PDMS solution and the SiO2 sol to obtain a PDMS-SiO2 modifier; S3. Preparation of PDMS-SiO2 modified bamboo fiber: The dried bamboo fiber obtained in S1 is immersed in the PDMS-SiO2 modifier obtained in S2, stirred at room temperature, and then allowed to stand until the solvent evaporates, and then filtered, washed, and vacuum dried to obtain PDMS-SiO2 modified bamboo fiber; S4. Preparation of a ZnO-containing suspension: adding polyethyleneimine and ZnO nanoparticles into methanol to obtain a suspension containing ZnO; S5. Preparation of nano ZnO modified bamboo fiber: The PDMS-SiO2 modified bamboo fiber obtained in S3 is immersed in the ZnO-containing suspension obtained in S4, and then a silane coupling agent is added, and the mixture is stirred at room temperature. After stirring, the mixture is allowed to stand until the solvent evaporates, and then filtered, washed, and vacuum dried to obtain the PDMS-SiO2-ZnO modified bamboo fiber; S6. Preparation of masterbatch: The PDMS-SiO2-ZnO modified bamboo fiber obtained in S5 and polylactic acid are mixed, dried at 90°C for 24 hours, crushed to obtain a powdered mixture, placed in a twin-screw extruder for melt extrusion, water-cooled, pelletized, and dried to obtain a masterbatch; S7, Compression molding: The masterbatch obtained in S6 is heated to a molten state, injected into a mold for hot pressing, cooled, dried at room temperature, polished, edge trimmed, and assembled to obtain a high-strength antibacterial and degradable bamboo fiber / polylactic acid bamboo plastic composite material.

2. The method for preparing a high-strength antibacterial and degradable bamboo fiber / polylactic acid bamboo plastic composite material according to claim 1, characterized in that: The rolling gap in S1 is 2 mm, and the crushing speed is 32000 r / min; the mesh number of the bamboo fiber after drying in S1 is 60 mesh to 100 mesh; and the moisture content of the bamboo fiber after drying is less than 3%.

3. The method for preparing a high-strength antibacterial and degradable bamboo fiber / polylactic acid bamboo plastic composite material according to claim 1, characterized in that: The mass ratio of polydimethylsiloxane and ethyl acetate in the PDMS solution in S2 is 1:10; the mass ratio of tetraethyl orthosilicate, methanol and ethanol in the SiO2 sol is 1:10:15; the mass ratio of PDMS solution and SiO2 sol in the PDMS-SiO2 modifier is 1:

1.

4. The method for preparing a high-strength antibacterial and degradable bamboo fiber / polylactic acid bamboo plastic composite material according to claim 1, characterized in that: The stirring rate in S3 and S5 is 300 rpm, and the stirring time is 2 h. The vacuum drying conditions in S3 and S5 are both: drying in a vacuum drying oven at a temperature of 90° C. for 24 h.

5. The method for preparing a high-strength antibacterial and degradable bamboo fiber / polylactic acid bamboo plastic composite material according to claim 1, characterized in that: The mass ratio of polyethyleneimine, ZnO nanoparticles and methanol in the ZnO-containing suspension described in S4 is 1:1:

10.

6. The method for preparing a high-strength antibacterial and degradable bamboo fiber / polylactic acid bamboo plastic composite material according to claim 1, characterized in that: The mass ratio of the PDMS-SiO2 modified bamboo fiber, the ZnO-containing suspension and the silane coupling agent in S5 is 1:10:(1-2); the model of the silane coupling agent is KH550.

7. The method for preparing a high-strength antibacterial and degradable bamboo fiber / polylactic acid bamboo plastic composite material according to claim 1, characterized in that: The mass ratio of the PDMS-SiO2-ZnO modified bamboo fiber and polylactic acid described in S6 is 3:

7.

8. The method for preparing a high-strength antibacterial and degradable bamboo fiber / polylactic acid bamboo plastic composite material according to claim 1, characterized in that: The feed rate of the twin-screw extruder in S6 is 120g / min, the temperature is heated to 180°C, and the screw speed is 100r / min~200r / min; the aspect ratio of the masterbatch is 32:1; the drying conditions are: drying at 80°C for 8h.

9. The method for preparing a high-strength antibacterial and degradable bamboo fiber / polylactic acid bamboo plastic composite material according to claim 1, characterized in that: The hot pressing conditions in S6 are: hot pressing at a temperature of 150° C. to 200° C. and a pressure of 15 MPa to 18 MPa for 10 min to 20 min.

10. The method for preparing a high-strength antibacterial and degradable bamboo fiber / polylactic acid bamboo plastic composite material according to claim 1, characterized in that: The high-strength antibacterial and degradable bamboo fiber / polylactic acid bamboo plastic composite material described in S6 has a tensile strength of 40.08MPa to 41.08MPa, a flexural strength of 85.51MPa to 89.51MPa, and an impact strength of 4.56MPa to 4.84MPa.

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