A ceramicized flame-retardant pbt composite material containing a biobased carbon source and a preparation method thereof

Abstract

This invention discloses a ceramicized flame-retardant PBT composite material containing a bio-based carbon source and its preparation method, belonging to the field of polymer materials technology. The composite material uses PBT resin as a matrix and contains the following components: 5-30 parts of bio-based carbon source, 5-25 parts of phosphorus-based flame retardant, 5-20 parts of ceramicizing agent, and 5-20 parts of flux, or 0.1-2 parts of anti-dripping agent and 0.1-1 parts of antioxidant. Specifically, the bio-based carbon source is esterified cellulose or hyperbranched bio-based polyester. This invention constructs a quaternary synergistic system of bio-based carbon source-phosphorus-based flame retardant-ceramicizing agent-flux, which catalyzes the formation of a robust and dense ceramic protective layer during combustion, endowing the material with excellent flame-retardant properties, achieving a UL-94 V-0 rating and a limiting oxygen index greater than 30%, while maintaining the mechanical properties of the matrix. The process is simple, suitable for industrial production, and can be widely used in fields with high flame-retardant safety requirements, such as electronics, electrical appliances, and automobiles.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a ceramicized flame-retardant PBT composite material containing a bio-based carbon source and its preparation method. Background Technology

[0002] Polybutylene terephthalate (PBT) is an important engineering plastic widely used in the electronics, electrical appliances and automotive industries. However, its inherent flammability and the dripping phenomenon during combustion pose significant safety hazards. Flame retardant modification is the key to broadening its application, but existing technologies all have limitations to varying degrees.

[0003] Traditional halogenated flame retardant systems, such as bromine-antimony systems, while exhibiting high flame retardant efficiency, release toxic and corrosive fumes during combustion, making it difficult to meet increasingly stringent environmental regulations. Inorganic hydroxide flame retardants, such as aluminum hydroxide and magnesium hydroxide, while environmentally friendly, require extremely high addition amounts to achieve effective flame retardant ratings, typically exceeding 50% of the matrix resin weight, severely impairing the processing flowability, mechanical strength, and surface quality of PBT products. Halogen-free intumescent flame retardant systems, particularly the classic combination of ammonium polyphosphate as the acid source, pentaerythritol as the carbon source, and melamine as the gas source, face numerous challenges in their application to PBT: ammonium polyphosphate has poor compatibility with the PBT matrix, easily migrating and precipitating during processing and use, leading to unstable flame retardant performance and affecting product appearance; while pentaerythritol, as a carbon source, suffers from hygroscopicity, insufficient thermal stability, and poor compatibility with PBT, often negatively impacting the material's mechanical properties and long-term durability. In addition, the char layer formed by the system after heating has low strength and insufficient density, and is prone to cracking under high temperature or external airflow impact, resulting in a decrease in flame retardant performance.

[0004] Ceramicization flame retardant technology achieves its physical barrier function by forming a ceramic layer. However, the effective implementation of this technology depends on the precise matching of the thermal decomposition behaviors of components such as acid sources, carbon sources, and fluxes to ensure the rapid construction of a continuous and dense ceramic protective layer within the critical temperature window of polymer thermal degradation. Current technologies often involve simply compounding glass powder with conventional flame retardants, which fails to achieve this kinetic synergy. Furthermore, the introduction of large amounts of inorganic fillers inevitably leads to the degradation of the matrix resin properties. More importantly, the lack of a carbon source with good compatibility with PBT, high thermal stability, and ideal char formation efficiency has become a major bottleneck restricting the breakthrough of ceramicization flame retardant technology in PBT. Summary of the Invention

[0005] To overcome the problems of poor compatibility, easy migration and precipitation, insufficient thermal stability, and poor quality of char layer of traditional phosphorus-nitrogen intumescent flame retardants (especially carbon source components) with PBT matrix in the prior art, the main purpose of this invention is to provide a ceramicized flame-retardant PBT composite material containing a bio-based carbon source, which not only endows PBT material with high flame retardant performance and effective ceramicization characteristics, but also maintains its inherent mechanical properties and processing characteristics to the maximum extent.

[0006] Another objective of this invention is to provide a method for preparing the ceramicized flame-retardant PBT composite material containing a bio-based carbon source. The method uses synthetic bio-based material as the carbon source and forms a synergistic halogen-free flame-retardant system with phosphorus-based flame retardants, ceramicizing agents, and fluxing agents. This system allows the PBT composite material to form a dense ceramic layer during combustion, achieving high flame retardancy, low smoke toxicity, and good overall performance. The process is simple and easy to scale up for mass production.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a ceramicized flame-retardant PBT composite material containing a bio-based carbon source, comprising the following components by weight: 100 parts of PBT resin, 5-30 parts of bio-based carbon source, 5-25 parts of phosphorus-based flame retardant, 5-20 parts of ceramicizing agent, 5-20 parts of fluxing agent, or further comprising 0.1-2 parts of anti-dripping agent and / or 0.1-1 parts of antioxidant;

[0009] The bio-based carbon source is a micron or nano-scale particle, fiber, or spherical structure with an average particle size or radial dimension between 0.1 and 50 μm. The molecular structure contains an aromatic ring structure, a long-chain alkyl group with no less than 8 carbon atoms, or a hyperbranched structure. The residual carbon rate after thermal decomposition at 800°C is no less than 20 wt%. It is obtained from renewable biomass raw materials through chemical modification or polymerization reaction.

[0010] The renewable biomass raw material is selected from one or more of cellulose, lignin, starch, vegetable oil and its derivatives, or biomass compounds;

[0011] The chemical modification or polymerization reaction includes esterification, etherification, crosslinking, polycondensation, or graft copolymerization.

[0012] Preferably, the bio-based carbon source is cellulose microcrystals or nanofibers modified by long-chain fatty acid esterification, and more preferably, decanoic acid esterified cellulose nanocrystals.

[0013] Preferably, the bio-based carbon source is a hyperbranched polyester formed by polycondensation reaction of plant oil-based polyols and bio-based dicarboxylic acids, and more preferably itaconic acid-glycerol hyperbranched polyester.

[0014] As a preferred embodiment, the ceramicized flame-retardant PBT composite material comprises the following components by weight: 100 parts PBT resin, 10-20 parts bio-based carbon source, 10-20 parts phosphorus-based flame retardant, 5-20 parts ceramicizing agent, 5-20 parts fluxing agent, 0.1-2 parts anti-dripping agent, and 0.1-1 parts antioxidant.

[0015] Preferably, the phosphorus-based flame retardant is one or more of ammonium polyphosphate, aluminum hypophosphite, aluminum diethylphosphite, or melamine polyphosphate.

[0016] Preferably, the ceramic-forming agent is one or more of silicon dioxide, alumina, kaolin, or wollastonite.

[0017] Preferably, the flux is one or more of zinc borate, zinc molybdate, or low-melting-point borosilicate glass powder.

[0018] Preferably, the anti-dripping agent is polytetrafluoroethylene.

[0019] A second aspect of the present invention provides a method for preparing a ceramicized flame-retardant PBT composite material containing a bio-based carbon source, comprising the following steps:

[0020] a) Raw material pretreatment: Vacuum dry PBT resin at 100-120℃ for 4-6 hours;

[0021] b) Premix: Place the dried PBT resin, bio-based carbon source, phosphorus flame retardant, ceramic agent, flux and other additives in a high-speed mixer and mix for 5-15 minutes at room temperature to obtain a uniform premix.

[0022] c) Melt blending and granulation: The premixed material is fed into a twin-screw extruder and subjected to melt extrusion, water cooling, traction, and pelletizing to obtain the final product.

[0023] Preferably, in step c), the processing temperature of the twin-screw extruder is: 220-230℃ in zone 1, 230-240℃ in zone 2, 235-245℃ in zone 3, 235-245℃ in zone 4, and 235-245℃ at the die head; the screw speed is 300-400 rpm.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] I. Using renewable biomass as raw material, a highly efficient bio-based carbon source is obtained through synthesis and modification, achieving halogen-free flame retardancy and overcoming the environmental and safety issues of traditional halogenated flame retardants releasing toxic fumes during combustion. Simultaneously, due to its good compatibility with the PBT matrix, the impact on the material's mechanical properties is significantly reduced.

[0026] II. This invention constructs a quaternary system of bio-based carbon source-phosphorus flame retardant-ceramic agent-fluxter, which produces a significant synergistic effect during combustion: the phosphorus flame retardant acts as an acid source, catalyzing the cross-linking of the carbon source and PBT itself into char; the flux melts at a specific temperature, flows and encapsulates the carbon layer and the ceramic agent skeleton, forming a robust, dense, continuous and highly adhesive three-dimensional network ceramic protective layer, effectively isolating heat and oxygen, thereby giving the PBT composite material a high flame retardant rating of UL-94V-0 (1.6mm) and a limiting oxygen index of over 30%, improving the problems of poor compatibility, easy migration and precipitation, insufficient thermal stability and poor char quality of traditional phosphorus-nitrogen intumescent flame retardants (especially their carbon source components) with the PBT matrix.

[0027] Third, the preparation method of the ceramicized flame-retardant PBT composite material in this invention is simple, with clear parameters, and suitable for large-scale industrial production. The resulting composite material achieves extremely high flame-retardant properties while maintaining good mechanical strength and processing fluidity, and also possesses excellent electrical insulation and heat resistance. It can meet the stringent requirements for comprehensive material performance in the electronics, automotive, and other fields, making it an ideal material for manufacturing high-end electronic connectors, automotive engine peripheral parts, new energy battery modules, and other products with extremely high safety and reliability requirements. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments and comparative examples. It should be understood that the embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0029] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0030] Example 1: Synthesis of decanoic acid esterified cellulose nanocrystals (CNC-C10)

[0031] Raw materials: Cellulose nanocrystals (CNC, derived from wood pulp, diameter 10-20nm, length 100-400nm), decanoyl chloride, pyridine, N,N-dimethylformamide (DMF, anhydrous).

[0032] 5 g of dried CNC was dispersed in 250 mL of anhydrous DMF and sonicated in an ice-water bath for 1 hour. 10 mL of pyridine was added to the dispersion as a catalyst and acid absorber. Under nitrogen protection and mechanical stirring, 50 mL of anhydrous DMF solution containing 15 g of decanoyl chloride was slowly added dropwise using a constant pressure dropping funnel, with the addition time controlled at 30 minutes. After the addition was completed, the ice-water bath was removed, the reaction system was heated to 80 °C, and the reaction was continued for 12 hours under nitrogen protection and stirring.

[0033] After the reaction was completed, the reaction mixture was cooled to room temperature and poured into 500 mL of anhydrous ethanol to terminate the reaction, resulting in the formation of a white precipitate. The precipitate was collected by centrifugation and washed repeatedly with fresh anhydrous ethanol and centrifuged three times to remove residual reagents and byproducts. The final product was dried in a vacuum drying oven at 60 °C for 24 hours to obtain a loose white powder, namely decanoic acid esterified cellulose nanocrystals (CNC-C10).

[0034] According to TGA testing, its carbon residue rate under a nitrogen atmosphere at 800℃ is 28.5%.

[0035] Example 2: Synthesis of itaconic acid-glycerol hyperbranched polyester (IG-HBP)

[0036] Ingredients: Itaconic acid, glycerin, p-toluenesulfonic acid (PTSA).

[0037] In a three-necked flask equipped with a magnetic stirrer, a water separator, and a condenser, itaconic acid (26.0 g, 0.2 mol) and glycerol (13.8 g, 0.15 mol), along with 0.2 g of p-toluenesulfonic acid as a catalyst, were added. The mixture was slowly heated to 150 °C under a nitrogen atmosphere and reacted at this temperature for 5 hours, during which time the generated water was removed using the water separator. Subsequently, the system pressure was reduced to -0.095 MPa, and the reaction was continued at 150 °C for 1 hour to remove residual water and unreacted monomers, yielding a pale yellow, viscous hyperbranched polyester product (IG-HBP).

[0038] According to TGA testing, its carbon residue rate under a nitrogen atmosphere at 800℃ is 22.1%.

[0039] Examples 3-5 and Comparative Examples 1-2

[0040] Preparation of ceramic flame-retardant PBT composite materials: Composite materials of each example and comparative example were prepared according to the proportions (unit: parts by weight) shown in Table 1.

[0041] Table 1

[0042]

[0043] Preparation method:

[0044] Pretreatment: Dry the PBT resin in a vacuum drying oven at 110°C for 5 hours.

[0045] Premixing: According to the proportions in Table 1, add the dried PBT resin and all other components into a high-speed mixer and mix at 1000 rpm for 8 minutes at room temperature until the mixture is homogeneous.

[0046] Melt blending and granulation: The mixed premixed material is poured into the main feed port of a co-rotating twin-screw extruder (length-to-diameter ratio 40:1). The temperatures of each section of the extruder are set as follows: Zone 1 225℃, Zone 2 235℃, Zone 3 240℃, Zone 4 240℃, and Die head 240℃. The screw speed is set to 350 rpm. After melt extrusion, water cooling, traction, and pelletizing, composite material particles are obtained.

[0047] Injection molding: After drying the composite material granules at 100°C for 4 hours, they are injection molded into standard test strips using an injection molding machine for performance testing.

[0048] Performance Tests and Results

[0049] The performance of the composite material specimens prepared above was tested, and the results are shown in Table 2.

[0050] Table 2: Test Results

[0051]

[0052] Comparative Example 1 (pure PBT) exhibited poor flame retardant performance and produced molten droplets during combustion. Comparative Example 2, using a traditional APP / PER expansion system, formed a conventional expanded char layer. While achieving a V-0 rating, it had a relatively low LOI value and suffered significant loss in mechanical properties (especially impact strength) (a decrease of approximately 36%), resulting in loose char residue and limited protective effect. Examples 3-5 employed a bio-based carbon source and a ceramicized system, forming a robust and dense ceramic layer that achieved a UL94V-0 rating. Furthermore, their LOI values ​​were significantly higher than Comparative Example 2, demonstrating superior flame retardant efficiency. Simultaneously, the retention rate of mechanical properties, particularly impact strength, was far higher than Comparative Example 2. The impact strength of Example 3 was approximately 29% higher than Comparative Example 2, indicating that the bio-based carbon source synthesized in this invention has better compatibility with the PBT matrix. Example 4, combining two bio-based carbon sources, exhibited excellent LOI values, demonstrating a positive synergistic effect between carbon sources with different structures.

[0053] In summary, this invention successfully provides a ceramicized flame-retardant PBT composite material and its preparation method that combine high flame retardancy, excellent ceramicization effect, and good mechanical properties. It can be widely used in fields with high requirements for flame retardancy and safety, such as electronics, electrical appliances, and automobiles.

[0054] The above are merely preferred embodiments of the present invention and are not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A ceramicized flame-retardant PBT composite material containing a bio-based carbon source, characterized in that, The product comprises the following components by weight: 100 parts PBT resin, 5-30 parts bio-based carbon source, 5-25 parts phosphorus flame retardant, 5-20 parts ceramicizing agent, 5-20 parts fluxing agent, or may also contain 0.1-2 parts anti-dripping agent and / or 0.1-1 parts antioxidant. The bio-based carbon source is a micron or nano-scale particle, fiber, or spherical structure with an average particle size or radial dimension between 0.1 and 50 μm. The molecular structure contains an aromatic ring structure, a long-chain alkyl group with no less than 8 carbon atoms, or a hyperbranched structure. The residual carbon rate after thermal decomposition at 800°C is no less than 20 wt%. It is obtained from renewable biomass raw materials through chemical modification or polymerization reaction. The renewable biomass raw material is selected from one or more of cellulose, lignin, starch, vegetable oil and its derivatives, or biomass compounds; The chemical modification or polymerization reaction includes esterification, etherification, crosslinking, polycondensation, or graft copolymerization.

2. The ceramicized flame-retardant PBT composite material containing a bio-based carbon source according to claim 1, characterized in that, The bio-based carbon source is cellulose microcrystals or nanofibers modified by long-chain fatty acid esterification.

3. The ceramicized flame-retardant PBT composite material containing a bio-based carbon source according to claim 1, characterized in that, The bio-based carbon source is a hyperbranched polyester formed by polycondensation reaction of plant oil-based polyols and bio-based dicarboxylic acids.

4. The ceramicized flame-retardant PBT composite material containing a bio-based carbon source according to claim 1, characterized in that, The bio-based carbon source is decanoic acid esterified cellulose nanocrystals and / or itaconic acid-glycerol hyperbranched polyester.

5. The ceramicized flame-retardant PBT composite material containing a bio-based carbon source according to claim 1, characterized in that, The ceramicized flame-retardant PBT composite material comprises the following components by weight: 100 parts PBT resin, 10-20 parts bio-based carbon source, 10-20 parts phosphorus-based flame retardant, 5-20 parts ceramicizing agent, 5-20 parts fluxing agent, 0.1-2 parts anti-dripping agent, and 0.1-1 parts antioxidant.

6. The ceramicized flame-retardant PBT composite material containing a bio-based carbon source according to claim 1, characterized in that, The phosphorus-based flame retardant is one or more of ammonium polyphosphate, aluminum hypophosphite, aluminum diethylphosphite, or melamine polyphosphate.

7. The ceramicized flame-retardant PBT composite material containing a bio-based carbon source according to claim 1, characterized in that, The ceramic-forming agent is one or more of silicon dioxide, alumina, kaolin, or wollastonite.

8. The ceramicized flame-retardant PBT composite material containing a bio-based carbon source according to claim 1, characterized in that, The flux is one or more of zinc borate, zinc molybdate, or low-melting-point borosilicate glass powder; And / or the anti-dripping agent is polytetrafluoroethylene.

9. A method for preparing the ceramicized flame-retardant PBT composite material containing a bio-based carbon source as described in any one of claims 1 to 8, characterized in that, Includes the following steps: a) Raw material pretreatment: Vacuum dry PBT resin at 100-120℃ for 4-6 hours; b) Premix: Place the dried PBT resin, bio-based carbon source, phosphorus flame retardant, ceramic agent, fluxing agent and other additives in a high-speed mixer and mix for 5-15 minutes at room temperature to obtain the premix. c) Melt blending and granulation: The premixed material is fed into a twin-screw extruder and subjected to melt extrusion, water cooling, traction, and pelletizing to obtain the final product.

10. The method for preparing the ceramicized flame-retardant PBT composite material containing a bio-based carbon source according to claim 9, characterized in that, In step c), the processing temperature of the twin-screw extruder is: Zone 1 220-230℃, Zone 2 230-240℃, Zone 3 235-245℃, Zone 4 235-245℃, and the die head 235-245℃; the screw speed is 300-400 rpm.

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