Bamboo fiber reinforced degradable composite material master batch and preparation method thereof

Abstract

The invention discloses a bamboo fiber reinforced degradable composite material master batch and a preparation method thereof in the field of bio-based degradable materials, the master batch takes polylactic acid as a matrix and natural bamboo fiber as a reinforcement, and a silane modified nano titanium dioxide attapulgite hybrid material and a strontium aluminate loaded mesoporous silica nano activator are introduced. During preparation, firstly, the bamboo fibers are subjected to alkali treatment pretreatment to improve the reaction activity of the bamboo fibers; polylactic acid, polybutylene terephthalate adipate, a plasticizer, a lubricant, two inorganic modified compounds and the pretreated bamboo fibers are mixed at a high speed, melt blending and extrusion are carried out through a double-screw extruder, cooling and pelletizing are carried out, and the composite material is obtained. The obtained master batch has good processability and comprehensive performance, is suitable for injection molding, extrusion and other molding processes, can be widely applied to the fields of environment-friendly packaging, daily products and the like, and is green and environment-friendly in the whole process.

Description

Technical Field

[0001] This invention relates to the field of bio-based biodegradable materials technology, specifically to a bamboo fiber reinforced biodegradable composite material masterbatch and its preparation method. Background Technology

[0002] With the increasing global awareness of environmental protection and the deepening implementation of sustainable development strategies, the development and application of bio-based biodegradable materials has become an important research direction in the field of materials science. Among these, the preparation of green materials using natural plant fibers as reinforcements and composites with biodegradable polymer matrices shows enormous development potential. Bamboo fiber, as a widely available, rapidly growing, and renewable natural fiber, is considered one of the ideal reinforcing materials for manufacturing green composite materials due to its high specific strength and modulus, as well as its good environmental friendliness. However, a core technical challenge urgently needs to be addressed in the application of bamboo fiber in composite materials: the surface of bamboo fiber is rich in hydroxyl groups, exhibiting strong hydrophilicity, while common biodegradable polymer matrices, such as polylactic acid, are hydrophobic. This significant difference in polarity leads to poor interfacial compatibility and weak interfacial bonding. The weak interfacial bonding prevents stress from being effectively transferred from the polymer matrix to the bamboo fiber, severely restricting the full development of the composite material's mechanical properties and potentially causing accelerated performance degradation in humid environments due to moisture intrusion at the interface, greatly limiting its application in high-performance products.

[0003] To improve the interfacial adhesion between bamboo fiber and the polymer matrix, the industry has explored various physical and chemical modification methods. Common approaches include alkali treatment, acetylation, or the use of silane coupling agents to reduce the hydrophilicity of the fiber or introduce functional groups on its surface that can better interact with the matrix. While these methods improve the interfacial condition to some extent, they still have many limitations. Many modification processes are complex, energy-intensive, or require large amounts of chemical reagents, potentially causing new environmental problems and not fully aligning with the principles of green environmental protection from a life-cycle assessment perspective. Furthermore, existing modification technologies often focus on solving the single problem of interfacial adhesion, lacking systematic solutions to the comprehensive challenges faced by composite materials in practical use, such as insufficient water resistance and uncontrollable degradation behavior. For example, simply improving the interface may not effectively inhibit the diffusion and penetration of water molecules, while excessively fast or slow degradation rates can affect the material's applicability in different application scenarios.

[0004] Therefore, developing novel modifiers and composite material preparation technologies that can fundamentally improve the interfacial compatibility between bamboo fiber and biodegradable plastics, while simultaneously endowing the materials with excellent water resistance and controllable degradation properties, has become crucial for advancing this field. The ideal solution should be to construct a robust, multifunctional interfacial layer between bamboo fiber and the polymer matrix through innovative material design. This interfacial layer should not only provide strong mechanical anchoring and chemical bonding but also act as a smart barrier, regulating the migration of water molecules and the diffusion of degradation media, thereby achieving the goal of maintaining stable performance during the service life and degrading at the expected rate after use. This requires the modifier itself to possess multiple functional groups, a specific microstructure, and responsiveness to environmental factors; currently, there is a lack of mature technologies and products on the market that can simultaneously meet these stringent requirements. Summary of the Invention

[0005] The purpose of this invention is to provide a bamboo fiber reinforced biodegradable composite material masterbatch and its preparation method, which solves the existing technical problems of poor interfacial compatibility between bamboo fiber and biodegradable plastic matrix, insufficient mechanical properties of composite materials, and uncontrollable degradation behavior.

[0006] The present invention achieves the above objectives through the following technical solutions: A method for preparing a bamboo fiber reinforced biodegradable composite material masterbatch, comprising the following steps: S1. Pulverize raw bamboo to obtain bamboo powder. Dry the bamboo powder under vacuum at 58-62℃ to obtain dried bamboo powder. Put the dried bamboo powder into sodium hydroxide solution and treat it at 78-82℃ to obtain treated bamboo fiber. After filtering and washing with water until neutral, the treated bamboo fiber is dried under vacuum again at 78-82℃ to obtain pretreated bamboo fiber. S2. Polylactic acid, polybutylene terephthalate-adipate, glyceryl triacetate, and zinc stearate are added to a mixer for premixing. Then, pretreated bamboo fiber, silane-modified nano-titanium dioxide-attapulgite hybrid material, and strontium aluminate-supported mesoporous silica nano-activator are added and mixed further to obtain a well-mixed material. The well-mixed material is fed into a twin-screw extruder, and after shearing and kneading, it is extruded through a die. The extruded strips are cooled in a water bath and cut into granules. The granules are then dried at 78-82℃.

[0007] In this invention, the core mechanism for preparing bamboo fiber reinforced biodegradable composite masterbatch lies in the interfacial synergy and structural reconstruction during the multi-component melt blending process. Pre-treated bamboo fibers undergo alkali treatment to partially remove lignin and hemicellulose, exposing more hydroxyl groups on the cellulose surface, thus enhancing fiber roughness and reactivity. During the melt blending stage, polylactic acid and polybutylene terephthalate (PET) form a continuous phase under shear force. Silane-modified nano-titanium dioxide attapulgite hybrid material becomes entangled with polymer molecular chains through its surface organic functional groups. Simultaneously, its inorganic nanoparticles interact mechanically with the bamboo fiber surface through mechanical interlocking and hydrogen bonding, effectively improving the interfacial compatibility between the hydrophilic fiber and the hydrophobic matrix. Strontium aluminate-supported mesoporous silica nano-activators utilize their mesoporous structure to adsorb polymer chains and promote the hydrolytic crosslinking of polylactic acid ester bonds through the basic sites of strontium aluminate. Simultaneously, ionic bonding sites are formed in the interfacial region, interacting with the hydroxyl groups of bamboo fibers and the carboxyl groups of the polymer to construct a three-dimensional crosslinked network. Glyceryl triacetate, acting as a plasticizer, inserts into the polymer molecular chains, weakening interchain forces and improving melt flowability. Zinc stearate, on the other hand, reduces processing resistance and interfacial energy through oriented alignment at the interface. Ultimately, under the shearing and mixing action of a twin-screw extruder, the components form a multidimensional synergistic interfacial structure through physical entanglement, chemical bonding, and ionic interactions, achieving a robust bond between bamboo fiber and the matrix, intelligent control of degradation rate, and comprehensive optimization of masterbatch processing flowability.

[0008] According to a preferred embodiment of the present invention, in step S1, the treatment time at 78-82°C is 2-4 hours.

[0009] According to a preferred embodiment of the present invention, in step S2, the temperatures of the twin-screw extruder from the feed inlet to the die head are 180-185°C, 190-195°C, 200-205°C, 190-195°C and 185-190°C, respectively.

[0010] According to a preferred embodiment of the present invention, the preparation method of the silane-modified nano-titanium dioxide-attapulgite hybrid material includes: A1, dispersing nano-titanium dioxide and attapulgite clay in anhydrous ethanol, ultrasonically treating to obtain a suspension; transferring the suspension to a four-necked flask, heating to 64-66℃ and maintaining a constant temperature, and adding a mixed solution of γ-aminopropyltriethoxysilane and hexadecyltrimethylammonium bromide dropwise under stirring; after the addition is complete, continuing the reaction to obtain a reaction mixture; A2, separating the reaction mixture by centrifugation to obtain a solid product, washing the solid product alternately with anhydrous ethanol and deionized water to obtain a washed product, drying the washed product in a vacuum drying oven at 78-82℃, and then treating it with a ball mill.

[0011] In this invention, the preparation mechanism of silane-modified nano-titanium dioxide-attapulgite hybrid material is mainly based on surface functionalization and interfacial synergy. Nano-titanium dioxide and attapulgite clay are ultrasonically dispersed in anhydrous ethanol to form a uniform suspension. The unique rod-shaped structure of the attapulgite clay and its abundant silanol groups provide active sites for subsequent reactions. Under heating and stirring conditions, γ-aminopropyltriethoxysilane first hydrolyzes to generate silanol. The silanol groups undergo condensation reactions with the hydroxyl groups on the surfaces of the attapulgite clay and nano-titanium dioxide, forming strong Si-O-Si and Si-O-Ti covalent bonds. Simultaneously, the amino functional groups at the silane terminus further interact electrostatically with the quaternary ammonium salt structure of hexadecyltrimethylammonium bromide, thereby constructing an organic molecular layer on the surface of the inorganic particles. This hybrid structure not only inhibits the aggregation of nanoparticles through steric hindrance but also introduces long alkyl chains to improve compatibility with the polymer matrix. The resulting core-shell structure material has a core composed of nano-titanium dioxide supported by attapulgite clay, which provides high specific surface area and reactivity, while the outer shell is an interfacial compatibility layer composed of silane and quaternary ammonium salt, which realizes efficient stress transfer and interfacial bonding between inorganic fillers and organic matrix.

[0012] According to a preferred embodiment of the present invention, in step A1, the reaction continues for 12-14 hours.

[0013] According to a preferred embodiment of the present invention, in step A2, the drying time in a vacuum drying oven at 78-82°C is 24-30 hours.

[0014] According to a preferred embodiment of the present invention, the preparation method of the strontium aluminate-supported mesoporous silica nano-activator includes: B1, mixing strontium carbonate and alumina, ball milling, placing the mixture in a muffle furnace, calcining at 1350-1400°C, cooling with the furnace, and ball milling again to obtain strontium aluminate nanopowder; B2, adding tetraethyl orthosilicate to a mixed solution composed of anhydrous ethanol, deionized water, ammonia, and hexadecyltrimethylammonium bromide, continuously stirring and reacting at 38-42°C to obtain mesoporous silica sol; dispersing the strontium aluminate nanopowder in the mesoporous silica sol, ultrasonicating, and obtaining a wet gel by rotary evaporation; drying the wet gel at 115-125°C, and finally calcining at 500-600°C.

[0015] In this invention, the preparation of strontium aluminate-supported mesoporous silica nano-activators involves a combination of high-temperature solid-state reaction and sol-gel method. First, strontium carbonate and alumina are mixed by ball milling and calcined at high temperature, resulting in a solid-state reaction to generate strontium aluminate crystals. During this process, strontium and aluminum ions rearrange in the crystal lattice to form a stable spinel structure. Subsequently, in the preparation of the mesoporous silica sol, tetraethyl orthosilicate is hydrolyzed and condensed under alkaline conditions to form a silicon-oxygen network structure. Simultaneously, hexadecyltrimethylammonium bromide acts as a template agent, forming micelles through self-assembly, guiding the polymerization of silica around it to generate regular mesoporous channels. When strontium aluminate nanoparticles are dispersed in this sol, the particles can enter the mesopores through capillary forces and are further uniformly distributed under ultrasonic treatment. The solvent is then removed by rotary evaporation, fixing the strontium aluminate particles to the inner walls of the silica mesopores. Finally, after medium-temperature calcination, the template agent is removed, and strontium aluminate forms Si-O-Al and Si-O-Sr bonds with the residual silanol groups on the silica surface, enhancing the loading stability. In the resulting composite material, mesoporous silica provides a high specific surface area and pore confinement effect as a support, while strontium aluminate, as a pH-responsive component, can release alkaline ions in specific environments to regulate degradation behavior. At the same time, its surface active sites can also form coordination bonds with the hydroxyl groups of bamboo fiber, strengthening the interfacial crosslinking network.

[0016] According to a preferred embodiment of the present invention, in step B1, the calcination time at 1350-1400°C is 4-6 hours.

[0017] According to a preferred embodiment of the present invention, in step B2, the reaction is continuously stirred at 38-42°C for 6-8 hours.

[0018] The present invention also provides a method for preparing the bamboo fiber reinforced biodegradable composite material masterbatch described above. The bamboo fiber reinforced biodegradable composite material masterbatch includes the following raw materials in parts by weight: 50-70 parts by weight of polylactic acid; 20-40 parts by weight of bamboo fiber; 3-8 parts by weight of silane-modified nano-titanium dioxide-attapulgite hybrid material; 2-6 parts by weight of strontium aluminate-supported mesoporous silica nano-activator; 5-15 parts by weight of polybutylene terephthalate-adipate; 1-3 parts by weight of glyceryl triacetate; and 0.5-2 parts by weight of zinc stearate.

[0019] The beneficial effects of this invention are as follows: The bamboo fiber reinforced biodegradable composite material masterbatch and its preparation method provided by this invention achieve synergistic improvement of multiple technical effects by introducing two key inorganic modifying compounds, significantly surpassing the performance level of existing technologies.

[0020] Firstly, this invention achieves a breakthrough in the core mechanical properties and interfacial bonding of composite materials. Two inorganic modifying compounds, through diversified mechanisms of action, significantly improve the interfacial compatibility between hydrophilic bamboo fibers and the hydrophobic polymer matrix. The silane-modified nano-titanium dioxide attapulgite hybrid material, on the one hand, generates a strong mechanical interlocking effect between the fiber and the matrix through its nanoscale physical morphology; on the other hand, the organic functional groups introduced on its surface can form strong chemical bonds with the polymer molecular chains. Simultaneously, the strontium aluminate-supported mesoporous silica nano-activator utilizes its high specific surface area and surface activity to form ionic crosslinking points in the interfacial region, further strengthening the interfacial adhesion. As a result of this multi-mechanism synergistic effect, stress can be efficiently transferred from the relatively flexible polymer matrix to the high-modulus bamboo fibers, comprehensively improving the tensile strength, flexural modulus, and impact toughness of the composite material, while effectively reducing stress concentration and early failure caused by interfacial defects, thus extending the material's service life.

[0021] Secondly, this invention successfully solves the industry challenge of balancing water resistance and controllable degradation in traditional bio-based composite materials. Through a dense interface design and the introduction of a hydrophobic barrier by inorganic modified compounds, the penetration and diffusion pathways of water molecules are effectively blocked, resulting in a significant reduction in water absorption in humid environments and a substantial improvement in dimensional stability and mechanical property retention. More importantly, the strontium aluminate-supported mesoporous silica nano-activator endows the material with intelligent degradation response characteristics. Under normal operating conditions, the composite material exhibits stable performance; however, when placed in specific composting or soil environments, strontium aluminate can respond to environmental pH, regulating the hydrolysis rate of polymer molecular chains, thereby achieving on-demand design of the material's degradation behavior. This intelligent characteristic of "stable during use and rapidly degradable after disposal" allows the material to meet the requirements of different application scenarios regarding service life and waste disposal, possessing environmental adaptability unmatched by traditional materials.

[0022] Finally, from the perspective of material processing performance and comprehensive application value, this invention exhibits significant advantages. The optimized formulation design and preparation process ensure uniform dispersion and good compatibility of each component during melt blending, resulting in masterbatch with excellent melt flowability and thermal stability. This allows it to adapt to various conventional processing methods such as injection molding and extrusion, demonstrating broad industrialization prospects. All components of the entire system meet environmental protection requirements, and the final product can be completely biodegraded under natural conditions after use, truly achieving green environmental protection throughout its entire life cycle from raw materials, processing, use to disposal. This masterbatch not only boasts mechanical properties comparable to some traditional petroleum-based plastic products but also possesses the dual advantages of controlled degradation and environmental friendliness, offering broad market application potential and significant social and environmental benefits in fields such as electronic product packaging, automotive interiors, disposable environmentally friendly products, and building decoration materials. Detailed Implementation

[0023] The present application will now be described in further detail. It should be noted that the following specific embodiments are only used to further illustrate the present application and should not be construed as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.

[0024] The following is information on domestic suppliers of key related equipment and materials: The polylactic acid was purchased from Shanghai Tongjieliang Biomaterials Co., Ltd.

[0025] The polybutylene terephthalate (PET) was purchased from Wuhan Xinxinjiali Biotechnology Co., Ltd.

[0026] The triglyceride was purchased from Jiangsu Licheng Chemical Co., Ltd.

[0027] The nano-titanium dioxide was purchased from Hubei Tianci Electronic Materials Co., Ltd.

[0028] The strontium carbonate was purchased from Sichuan Huanan Inorganic Salts Co., Ltd.

[0029] The alumina was purchased from Zibo Honghao Crystal Materials Co., Ltd.

[0030] Example 1 Preparation of silane-modified nano-titanium dioxide-attapulgite hybrid material: 10g of nano-titanium dioxide and 10g of attapulgite clay were dispersed in 200g of anhydrous ethanol and treated with an ultrasonic cell disruptor at 800W for 30min to form a homogeneous suspension. The suspension was transferred to a 2000mL four-necked flask, heated to 65℃ and kept constant. 5g of the mixture was slowly added dropwise using a constant-pressure dropping funnel while stirring at 400r / min. A mixed solution of γ-aminopropyltriethoxysilane and 2g hexadecyltrimethylammonium bromide was added dropwise over a period of 30 min. After the addition was complete, the reaction was continued at this temperature for 12 h. After the reaction was completed, the reaction mixture was transferred to a centrifuge tube and centrifuged at 8000 r / min for 15 min to obtain a solid product. The supernatant was discarded, and the product was washed three times alternately with 100 mL of anhydrous ethanol and 100 mL of deionized water, centrifuged under the same conditions after each wash. The washed product was evenly spread in a petri dish and dried in a vacuum drying oven at 80℃ for 24 h, with the vacuum level maintained at -0.08 MPa. The dried block product was transferred to a planetary ball mill and ball-milled at 350 r / min for 2 h. After passing through a 300-mesh sieve, silane-modified nano-titanium dioxide-attapulgite hybrid material was obtained and sealed and stored in a desiccator for later use.

[0031] Preparation of strontium aluminate-supported mesoporous silica nano-activators: 20g of strontium carbonate and 20g of alumina were mixed at a stoichiometric ratio of 1:1 and placed in a 500mL zirconia ball mill jar. 200g of zirconia grinding balls were added, and the mixture was ball-milled at 300r / min for 4h. The ball-milled powder was placed in an alumina crucible and placed in a muffle furnace. The temperature was increased to 1350℃ at a rate of 5℃ / min and calcined for 5h. Then, the temperature was cooled to room temperature with the furnace at a rate of 2℃ / min. The calcined product was ball-milled again for 2h to obtain strontium aluminate nanoparticles. 20g of tetraethyl orthosilicate was slowly added to a mixed solution consisting of 100g of anhydrous ethanol, 50g of deionized water, and 5g of 25% ammonia solution. Simultaneously, 3g of hexadecyl sulfate was added. Trimethylammonium bromide was used as a template agent and reacted under a 40°C water bath with continuous stirring at 500 rpm for 7 h to obtain a milky white mesoporous silica sol. 10 g of strontium aluminate nanoparticles were slowly added to the mesoporous silica sol and ultrasonically treated with an ultrasonic disperser at 900 W for 2 h. The uniformly dispersed mixture was transferred to a rotary evaporator and rotary evaporated to a gel state at a 60°C water bath temperature, 60 rpm, and -0.1 MPa vacuum. The wet gel was transferred to a forced-air drying oven and dried at 120°C for 7 h. Finally, the dried product was placed in a muffle furnace and calcined at 550°C at a rate of 3°C / min for 3 h. After natural cooling, strontium aluminate-supported mesoporous silica nano-activator was obtained.

[0032] Preparation of bamboo fiber reinforced biodegradable composite masterbatch: Raw bamboo was pulverized using a plant pulverizer and passed through a 100-mesh sieve. 30g of bamboo powder was evenly spread on a tray and dried in a 60℃ vacuum drying oven for 12 hours. The dried bamboo powder was then added to 600mL of a 5% sodium hydroxide solution and mechanically stirred in an 80℃ constant temperature water bath for 3 hours at a stirring speed of 200r / min. The treated bamboo fiber was filtered using a Buchner funnel and repeatedly washed with deionized water until the filtrate was neutral. The washed bamboo fiber was then dried again in an 80℃ vacuum drying oven to constant weight to obtain pretreated bamboo fiber. 60g of polylactic acid, 10g of polybutylene terephthalate (PET), 2g of triglyceride, and 1g of zinc stearate were added to an SHR-10A high-speed mixer and premixed at 500r / min for 5 minutes. Then, 30g of... Pretreated bamboo fiber, 5g silane-modified nano-titanium dioxide-attapulgite hybrid material, and 4g strontium aluminate-supported mesoporous silica nano-activator were mixed for 10 minutes at a speed of 800 rpm. The mixed material was then fed into a TE-35 co-rotating twin-screw extruder. The temperatures of the five zones of the extruder from the feed inlet to the die head were set to 180℃, 190℃, 200℃, 190℃, and 185℃, respectively. The die head temperature was 185℃, the screw speed was 200 rpm, and the feed rate was 15 kg / h. The extruded strips were immediately fed into a 3m long cooling water tank at a temperature of 25℃. The strips were then cut into cylindrical particles with a diameter of 3mm and a length of 4mm by a GLS-200 pelletizer. The pellets were dried in an 80℃ forced-air drying oven for 4 hours to obtain bamboo fiber reinforced biodegradable composite material masterbatch.

[0033] Example 2 Preparation of silane-modified nano-titanium dioxide-attapulgite hybrid material: 12g of nano-titanium dioxide and 8g of attapulgite clay were dispersed in 220g of anhydrous ethanol and treated with an ultrasonic cell disruptor at 800W for 30min to form a homogeneous suspension. The suspension was transferred to a 2000mL four-necked flask, heated to 65℃ and kept constant. 6g of the mixture was slowly added dropwise using a constant-pressure dropping funnel while stirring at 400r / min. A mixed solution of γ-aminopropyltriethoxysilane and 1 g of hexadecyltrimethylammonium bromide was added dropwise over a period of 30 min. After the addition was complete, the reaction was continued at this temperature for 13 h. After the reaction was completed, the reaction mixture was transferred to a centrifuge tube and centrifuged at 8000 r / min for 15 min to obtain a solid product. The supernatant was discarded, and the product was washed three times alternately with 100 mL of anhydrous ethanol and 100 mL of deionized water, centrifuged under the same conditions after each wash. The washed product was evenly spread in a petri dish and dried in a vacuum drying oven at 80 °C for 26 h, with the vacuum level maintained at -0.08 MPa. The dried block product was transferred to a planetary ball mill and ball-milled at 350 r / min for 2 h. After passing through a 300-mesh sieve, silane-modified nano-titanium dioxide-attapulgite hybrid material was obtained and sealed and stored in a desiccator for later use.

[0034] Preparation of strontium aluminate-supported mesoporous silica nano-activators: 18g of strontium carbonate and 18g of alumina were mixed at a stoichiometric ratio of 1:1 and placed in a 500mL zirconia ball mill jar. 200g of zirconia grinding balls were added, and the mixture was ball-milled at 300r / min for 4h. The ball-milled powder was placed in an alumina crucible and placed in a muffle furnace. The temperature was increased to 1370℃ at a rate of 5℃ / min and calcined for 4h. Then, the temperature was cooled to room temperature with the furnace at a rate of 2℃ / min. The calcined product was ball-milled again for 2h to obtain strontium aluminate nanoparticles. 18g of tetraethyl orthosilicate was slowly added to a mixed solution consisting of 110g of anhydrous ethanol, 45g of deionized water, and 4g of 25% ammonia solution, while 2g of hexadecane was added simultaneously. Trimethylammonium bromide was used as a template agent and reacted with continuous stirring at 500 r / min for 7 h in a 39 °C water bath to obtain a milky white mesoporous silica sol. 8 g of strontium aluminate nanoparticles were slowly added to the mesoporous silica sol and ultrasonically treated with an ultrasonic disperser at 900 W power for 2 h. The uniformly dispersed mixture was transferred to a rotary evaporator and rotary evaporated to a gel state at a 60 °C water bath temperature, 60 r / min speed and -0.1 MPa vacuum. The wet gel was transferred to a forced-air drying oven and dried at 118 °C for 6 h. Finally, the dried product was placed in a muffle furnace and heated to 530 °C at 3 °C / min, held at that temperature for 4 h, and naturally cooled to obtain a strontium aluminate-supported mesoporous silica nano-activator.

[0035] Preparation of bamboo fiber reinforced biodegradable composite masterbatch: Raw bamboo was pulverized using a plant pulverizer and passed through a 100-mesh sieve. 25g of bamboo powder was evenly spread on a tray and dried in a 60℃ vacuum drying oven for 12 hours. The dried bamboo powder was then added to 500mL of a 5% sodium hydroxide solution and mechanically stirred in a 79℃ constant temperature water bath for 3 hours at a stirring speed of 200r / min. The treated bamboo fiber was filtered using a Buchner funnel and repeatedly washed with deionized water until the filtrate was neutral. The washed bamboo fiber was then dried again in an 80℃ vacuum drying oven to constant weight to obtain pretreated bamboo fiber. 65g of polylactic acid, 8g of polybutylene terephthalate-adipate, 1.5g of triglyceride, and 0.8g of zinc stearate were added to an SHR-10A high-speed mixer and premixed at 500r / min for 5 minutes. Then, 2g of... 5g of pretreated bamboo fiber, 6g of silane-modified nano-titanium dioxide-attapulgite hybrid material, and 3g of strontium aluminate-supported mesoporous silica nano-activator were mixed for 10 minutes at a speed of 800 rpm. The mixed material was then fed into a TE-35 co-rotating twin-screw extruder. The temperatures of the five zones of the extruder from the feed inlet to the die head were set to 182℃, 192℃, 202℃, 192℃, and 187℃, respectively. The die head temperature was 187℃, the screw speed was 200 rpm, and the feeding rate was 15 kg / h. The extruded strips were immediately fed into a 3m long cooling water tank with the water temperature controlled at 25℃. The strips were then cut into cylindrical particles with a diameter of 3mm and a length of 4mm by a GLS-200 pelletizer. The pellets were dried in an 80℃ forced-air drying oven for 4 hours to obtain bamboo fiber reinforced biodegradable composite material masterbatch.

[0036] Example 3 Preparation of silane-modified nano-titanium dioxide-attapulgite hybrid material: 8g of nano-titanium dioxide and 12g of attapulgite clay were dispersed in 180g of anhydrous ethanol and treated with an ultrasonic cell disruptor at 800W for 30min to form a homogeneous suspension. The suspension was transferred to a 2000mL four-necked flask, heated to 65℃ and kept constant. 4g of the mixture was slowly added dropwise using a constant-pressure dropping funnel while stirring at 400r / min. A mixed solution of γ-aminopropyltriethoxysilane and 3g hexadecyltrimethylammonium bromide was added dropwise over a period of 30 min. After the addition was complete, the reaction was continued at this temperature for 13 h. After the reaction was completed, the reaction mixture was transferred to a centrifuge tube and centrifuged at 8000 r / min for 15 min to obtain a solid product. The supernatant was discarded, and the product was washed three times alternately with 100 mL of anhydrous ethanol and 100 mL of deionized water, and centrifuged under the same conditions after each wash. The washed product was evenly spread in a petri dish and dried in a vacuum drying oven at 80℃ for 28 h, with the vacuum degree maintained at -0.08 MPa. The dried block product was transferred to a planetary ball mill and ball-milled at 350 r / min for 2 h. After passing through a 300-mesh sieve, silane-modified nano-titanium dioxide-attapulgite hybrid material was obtained and sealed and stored in a desiccator for later use.

[0037] Preparation of strontium aluminate-supported mesoporous silica nano-activators: 22g of strontium carbonate and 22g of alumina were mixed at a stoichiometric ratio of 1:1 and placed in a 500mL zirconia ball mill jar. 200g of zirconia grinding balls were added, and the mixture was ball-milled at 300r / min for 4h. The ball-milled powder was placed in an alumina crucible and placed in a muffle furnace. The temperature was increased to 1380℃ at a rate of 5℃ / min and calcined for 5h. Then, the temperature was cooled to room temperature with the furnace at a rate of 2℃ / min. The calcined product was ball-milled again for 2h to obtain strontium aluminate nanoparticles. 22g of tetraethyl orthosilicate was slowly added to a mixed solution consisting of 90g of anhydrous ethanol, 55g of deionized water, and 6g of 25% ammonia solution, while 4g ​​of hexadecyl sulfate was added simultaneously. Trimethylammonium bromide was used as a template agent and reacted under a 41°C water bath with continuous stirring at 500 r / min for 7 h to obtain a milky white mesoporous silica sol. 12 g of strontium aluminate nanoparticles were slowly added to the mesoporous silica sol and ultrasonically treated with an ultrasonic disperser at 900 W power for 2 h. The uniformly dispersed mixture was transferred to a rotary evaporator and rotary evaporated to a gel state at a 60°C water bath temperature, 60 r / min speed and -0.1 MPa vacuum. The wet gel was transferred to a forced-air drying oven and dried at 122°C for 7 h. Finally, the dried product was placed in a muffle furnace and heated to 570°C at 3°C / min, held at that temperature for 3 h, and naturally cooled to obtain a strontium aluminate-supported mesoporous silica nano-activator.

[0038] Preparation of bamboo fiber reinforced biodegradable composite masterbatch: Raw bamboo was pulverized using a plant pulverizer and passed through a 100-mesh sieve. 35g of bamboo powder was evenly spread on a tray and dried in a 60℃ vacuum drying oven for 12 hours. The dried bamboo powder was then added to 700mL of a 5% sodium hydroxide solution and mechanically stirred in an 81℃ constant temperature water bath for 3 hours at a stirring speed of 200r / min. The treated bamboo fiber was filtered using a Buchner funnel and repeatedly washed with deionized water until the filtrate was neutral. The washed bamboo fiber was then dried again in an 80℃ vacuum drying oven to constant weight to obtain pretreated bamboo fiber. 55g of polylactic acid, 12g of polybutylene terephthalate-adipate, 2.5g of triglyceride, and 1.2g of zinc stearate were added to an SHR-10A high-speed mixer and premixed at 500r / min for 5 minutes. Then, the following were added... 35g of pretreated bamboo fiber, 4g of silane-modified nano-titanium dioxide-attapulgite hybrid material, and 5g of strontium aluminate-supported mesoporous silica nano-activator were mixed for 10 minutes at a speed of 800 rpm. The mixed material was then fed into a TE-35 co-rotating twin-screw extruder. The temperatures of the five zones of the extruder from the feed inlet to the die head were set to 183℃, 193℃, 203℃, 193℃, and 188℃, respectively. The die head temperature was 188℃, the screw speed was 200 rpm, and the feeding rate was 15 kg / h. The extruded strips were immediately fed into a 3m long cooling water tank with the water temperature controlled at 25℃. The strips were then cut into cylindrical particles with a diameter of 3mm and a length of 4mm by a GLS-200 pelletizer. The pellets were dried in an 80℃ forced-air drying oven for 4 hours to obtain bamboo fiber reinforced biodegradable composite material masterbatch.

[0039] Comparative Example 1 The preparation method is the same as in Example 1, except that the bamboo fiber reinforced biodegradable composite material masterbatch is prepared as follows: raw bamboo is crushed using a plant pulverizer, passed through a 100-mesh sieve, and 30g of bamboo powder is evenly spread on a tray and dried in a 60℃ vacuum drying oven for 12h; the dried bamboo powder is added to 600mL of 5% sodium hydroxide solution and mechanically stirred in an 80℃ constant temperature water bath for 3h at a stirring speed of 200r / min; the treated bamboo fiber is filtered using a Buchner funnel and repeatedly washed with deionized water until the filtrate is neutral, and the washed bamboo fiber is dried again in an 80℃ vacuum drying oven to constant weight to obtain pretreated bamboo fiber; 60g of polylactic acid, 10g of polybutylene terephthalate-adipate, 2g of triacetin, and 1g of zinc stearate are added to an SHR-10A high-speed mixer. In the mixing machine, premix at 500 r / min for 5 min; then add 30 g of pretreated bamboo fiber, increase the mixer speed to 800 r / min and continue mixing for 10 min; feed the mixed material into a TE-35 co-rotating twin-screw extruder, with the extruder's five temperature zones set from the feed inlet to the die head as 180℃, 190℃, 200℃, 190℃ and 185℃ respectively, the die head temperature at 185℃, the screw speed at 200 r / min, and the feeding rate at 15 kg / h; the extruded strips immediately enter a 3 m long cooling water tank, with the water temperature controlled at 25℃, and then are cut into cylindrical particles with a diameter of 3 mm and a length of 4 mm by a GLS-200 pelletizer; the cut particles are dried in an 80℃ forced-air drying oven for 4 h to obtain bamboo fiber reinforced biodegradable composite material masterbatch.

[0040] Comparative Example 2 The preparation method is the same as in Example 1, except that the preparation of the silane-modified nano-titanium dioxide-attapulgite hybrid material is the same as in Example 1. Preparation of bamboo fiber reinforced biodegradable composite masterbatch: Raw bamboo was pulverized using a plant pulverizer, passed through a 100-mesh sieve, and 30g of bamboo powder was evenly spread on a tray and dried in a 60℃ vacuum drying oven for 12 hours. The dried bamboo powder was added to 600mL of a 5% sodium hydroxide solution and mechanically stirred in an 80℃ constant temperature water bath for 3 hours at a stirring speed of 200r / min. The treated bamboo fiber was filtered using a Buchner funnel and repeatedly washed with deionized water until the filtrate was neutral. The washed bamboo fiber was then dried again in an 80℃ vacuum drying oven to constant weight to obtain pretreated bamboo fiber. 60g of polylactic acid, 10g of polybutylene terephthalate-adipate, 2g of triglyceride, and 1g of zinc stearate were added to an SHR-10A high-speed mixer and premixed at 500r / min for 5 minutes. Then add 30g of pretreated bamboo fiber and 5g of silane-modified nano-titanium dioxide-attapulgite hybrid material, increase the mixer speed to 800r / min and continue mixing for 10min; feed the mixed material into a TE-35 co-rotating twin-screw extruder, set the temperatures of the five zones of the extruder from the feed inlet to the die head to 180℃, 190℃, 200℃, 190℃ and 185℃ respectively, the die head temperature to 185℃, the screw speed to 200r / min, and the feeding rate to 15kg / h; the extruded strips immediately enter a 3m long cooling water tank, the water temperature is controlled at 25℃, and then cut into cylindrical particles with a diameter of 3mm and a length of 4mm by a GLS-200 pelletizer; dry the cut particles in an 80℃ forced-air drying oven for 4h to obtain bamboo fiber reinforced biodegradable composite material masterbatch.

[0041] Comparative Example 3 The preparation method is the same as in Example 1, except that the preparation of the strontium aluminate-supported mesoporous silica nano-activator is the same as in Example 1. Preparation of bamboo fiber reinforced biodegradable composite masterbatch: Raw bamboo was pulverized using a plant pulverizer, passed through a 100-mesh sieve, and 30g of bamboo powder was evenly spread on a tray and dried in a 60℃ vacuum drying oven for 12h. The dried bamboo powder was added to 600mL of a 5% sodium hydroxide solution and mechanically stirred in an 80℃ constant temperature water bath for 3h at a stirring speed of 200r / min. The treated bamboo fiber was filtered using a Buchner funnel and repeatedly washed with deionized water until the filtrate was neutral. The washed bamboo fiber was then dried again in an 80℃ vacuum drying oven to constant weight to obtain pretreated bamboo fiber. 60g of polylactic acid, 10g of polybutylene terephthalate-adipate, 2g of triglyceride, and 1g of zinc stearate were added to an SHR-10A high-speed mixer and premixed at 500r / min. 5 min; then add 30g of pretreated bamboo fiber and 4g of strontium aluminate-supported mesoporous silica nano-activator, increase the mixer speed to 800 r / min and continue mixing for 10 min; feed the mixed material into a TE-35 co-rotating twin-screw extruder, set the temperatures of the five zones of the extruder from the feed inlet to the die head to 180℃, 190℃, 200℃, 190℃ and 185℃ respectively, the die head temperature to 185℃, the screw speed to 200 r / min, and the feeding rate to 15 kg / h; the extruded strips immediately enter a 3m long cooling water tank, the water temperature is controlled at 25℃, and then cut into cylindrical particles with a diameter of 3mm and a length of 4mm by a GLS-200 pelletizer; dry the cut particles in an 80℃ forced-air drying oven for 4h to obtain bamboo fiber reinforced biodegradable composite material masterbatch.

[0042] Performance testing and results analysis According to existing national and industry standards, the following methods were used to test the performance of the bamboo fiber reinforced biodegradable composite masterbatches prepared in Examples 1-3 and Comparative Examples 1-3: Tensile performance testing was conducted using a universal testing machine. A standard dumbbell-shaped specimen, injection-molded, was installed in a fixture with a clamping distance of 50 mm. A uniform tensile load of 5 mm / min was applied until the specimen broke. The maximum load value and elongation at fracture were recorded. The tensile strength and elongation at break were calculated. The arithmetic mean of five valid samples were used for each test condition. Bending performance testing employed the three-point bending method. A cuboid specimen of specified dimensions was placed on two support rollers with a span of 64 mm. A pressure head applied a downward load at a speed of 2 mm / min. The load-displacement curve during the bending deformation process was recorded. The bending strength and bending modulus were calculated based on the maximum load. Five valid samples were used for each test condition. Impact performance testing uses a cantilever beam impact testing machine. A notch of a specified depth is machined in the middle of a standard rectangular specimen. The specimen is accurately fixed on the impact testing machine, and a pendulum is released to impact the unnotched side of the specimen. The energy consumed in breaking the specimen is recorded, and the impact energy consumed per unit notched section is calculated. Ten valid samples are tested under each condition. For water absorption testing, the specimen is first dried to constant weight in a 50℃ vacuum drying oven, and the initial mass is recorded. Then, it is completely immersed in 23℃ distilled water. After 24 hours, it is removed, the surface moisture is blotted with filter paper, and it is immediately weighed. The water absorption rate is calculated based on the mass difference before and after immersion. Three parallel samples are tested under each condition. For heat distortion temperature testing, the specimen is placed in the oil bath of a heat distortion testing machine. After applying a specified bending load, the temperature is uniformly increased at a rate of 120℃ / h. The temperature at which the specimen reaches the specified deflection is recorded. Three parallel samples are tested under each condition. The biodegradation rate test involves burying the dried and weighed samples in a specific composting environment, controlling the temperature at 58℃ and the humidity at 50%. After 90 days, the samples are removed, surface adhering substances are cleaned, and the samples are dried and weighed. The biodegradation rate is calculated based on the mass loss. Three parallel samples are tested under each condition.

[0043] Table 1: Performance test results of each embodiment and comparative example ; As shown in Table 1, a comprehensive analysis of the performance test results clearly demonstrates that Examples 1-3 effectively solved the three major technical problems compared to Comparative Examples 1-3: poor interfacial compatibility between bamboo fiber and the biodegradable plastic matrix, insufficient mechanical properties of the composite material, and uncontrollable degradation behavior. Comparative Example 1, without any modifiers, had a tensile strength of only 45.2 MPa, a flexural strength of 60.8 MPa, and an impact strength of 8.9 kJ / m. 2The results indicate that the unmodified bamboo fiber has a weak interface bond with the plastic matrix, resulting in severely insufficient mechanical properties. Simultaneously, its water absorption rate is as high as 3.8%, indicating numerous interface defects leading to poor water resistance. The biodegradability rate of 82.5% indicates that the degradation process is too rapid and uncontrollable. Comparative Example 2, which only added silane-modified nano-titanium dioxide attapulgite hybrid material, showed improved mechanical properties but still significantly lower than the Example group, indicating that a single interface modifier cannot achieve optimal interface strengthening. Comparative Example 3, which only added strontium aluminate-supported mesoporous silica nano-activator, reduced its biodegradability rate to 68.9%, indicating that the degradation process was inhibited but the control precision was insufficient, while the improvement in mechanical properties was limited. In contrast, Examples 1-3, using two modifiers simultaneously, produced a significant synergistic effect: Example 1 achieved a tensile strength of 68.5 MPa, a 51.5% increase compared to Comparative Example 1; a flexural strength of 92.1 MPa, a 51.5% increase; and an impact strength of 15.3 kJ / m. 2 The biodegradability was increased by 71.9%; the water absorption rate decreased to 1.2%, a reduction of 68.4%; and the biodegradability remained within the ideal range of 75.6%. These data fully demonstrate that when the two modified compounds work together, the silane-modified nano-titanium dioxide attapulgite hybrid material significantly enhances the interfacial bonding through mechanical interlocking and chemical bonding, while the strontium aluminate-supported mesoporous silica nano-activator achieves precise control of degradation through pH-responsive characteristics. At the same time, the two synergistically improve the interfacial water resistance, ultimately enabling the composite material to achieve excellent comprehensive performance while maintaining good degradability, successfully solving the core problem in the existing technology.

Claims

1. A method for preparing a bamboo fiber reinforced degradable composite master batch, characterized by the steps of Comprise: S1, the raw bamboo is crushed to obtain bamboo powder, the bamboo powder is dried at 58-62 DEG C under vacuum to obtain dried bamboo powder; the dried bamboo powder is put into sodium hydroxide solution, treated at 78-82 DEG C, to obtain treated bamboo fiber; the treated bamboo fiber is filtered, washed to neutral, and then vacuum dried at 78-82 DEG C again, to obtain pretreated bamboo fiber; S2, polylactic acid, polybutylene adipate terephthalate, glycerol triacetate and zinc stearate are added to a mixing machine for premixing; then pretreated bamboo fiber, silane modified nano titanium dioxide-palygorskite hybrid material and strontium aluminate loaded mesoporous silica nano activator are added, and mixing is continued, to obtain mixed material; the mixed material is sent into a double screw extruder, sheared and mixed, and then extruded through a die; the extruded strip is cooled in a water tank, and then cut into particles, which are dried at 78-82 DEG C.

2. The method for preparing the bamboo fiber reinforced degradable composite master batch according to claim 1, characterized in that, In step S1, the treatment time at 78-82 DEG C is 2-4h.

3. The method for preparing bamboo fiber reinforced biodegradable composite material masterbatch according to claim 1, characterized in that, In step S2, the temperature of the double screw extruder from the feeding port to the die head is 180-185 DEG C, 190-195 DEG C, 200-205 DEG C, 190-195 DEG C and 185-190 DEG C in turn.

4. The method for preparing bamboo fiber reinforced biodegradable composite material masterbatch according to claim 1, characterized in that, The preparation method of the silane modified nano titanium dioxide-palygorskite hybrid material comprises: A1, dispersing nano titanium dioxide and palygorskite clay in anhydrous ethanol, and ultrasonic treatment to obtain a suspension; the suspension is transferred to a four-necked flask, heated to 64-66 DEG C, and a mixed solution of γ-aminopropyl triethoxysilane and cetyltrimethylammonium bromide is added dropwise under stirring; after the dropwise addition is completed, the reaction is continued to obtain a reaction mixture; A2, the reaction mixture is separated by centrifugation to obtain a solid product, which is washed alternately with anhydrous ethanol and deionized water to obtain a washed product, which is dried in a 78-82 DEG C vacuum drying oven, and then treated by a ball mill.

5. The method for preparing bamboo fiber reinforced biodegradable composite material masterbatch according to claim 4, characterized in that, In step A1, the reaction time is 12-14h.

6. The method for preparing bamboo fiber reinforced biodegradable composite material masterbatch according to claim 4, characterized in that, In step A2, the drying time in the 78-82 DEG C vacuum drying oven is 24-30h.

7. The method for preparing bamboo fiber reinforced biodegradable composite material masterbatch according to claim 1, characterized in that, The preparation method of the strontium aluminate loaded mesoporous silica nano activator comprises: B1, mixing strontium carbonate and aluminum oxide, ball milling, and then calcining in a muffle furnace at 1350-1400 DEG C, and then ball milling after cooling in the furnace to obtain strontium aluminate nano powder; B2, adding tetraethyl orthosilicate into a mixed solution composed of anhydrous ethanol, deionized water, ammonia water and cetyltrimethylammonium bromide, and continuously stirring and reacting at 38-42 DEG C to obtain a mesoporous silica sol; dispersing the strontium aluminate nano powder in the mesoporous silica sol, ultrasonic treatment, and then rotary evaporation to obtain a wet gel; drying the wet gel at 115-125 DEG C, and finally calcining at 500-600 DEG C.

8. The method for preparing bamboo fiber reinforced biodegradable composite material masterbatch according to claim 7, characterized in that, In step B1, the calcining time at 1350-1400 DEG C is 4-6h.

9. The method for preparing bamboo fiber reinforced biodegradable composite material masterbatch according to claim 7, characterized in that, In step B2, the continuously stirring and reacting time at 38-42 DEG C is 6-8h.

10. A bamboo fiber reinforced degradable composite masterbatch prepared according to the method of any one of claims 1-9, characterized in that, The raw materials include the following components in parts by weight: 50-70 parts by weight of polylactic acid; 20-40 parts by weight of bamboo fiber; 3-8 parts by weight of silane-modified nano-titanium dioxide-attapulgite hybrid material; 2-6 parts by weight of strontium aluminate loaded mesoporous silica nano-activator; 5-15 parts by weight of polybutylene adipate terephthalate; 1-3 parts by weight of glycerol triacetate; and 0.5-2 parts by weight of zinc stearate.