Gutta-percha-based composite material and preparation method thereof

Abstract

The invention belongs to the technical field of polylactic acid composite materials, and particularly relates to a gutta-percha-based composite material and a preparation method thereof. The gutta-percha-based composite material is prepared from the following raw materials in parts by weight: 70 to 80 parts of polylactic acid, 10 to 20 parts of gutta-percha, 3 to 8 parts of modified fiber, 1 to 4 parts of reinforcing filler, 0.4 to 0.8 part of antioxidant and 1 to 3 parts of cross-linking agent, a preparation process of the modified fiber comprises the following steps: (1) adding pretreated linen fiber into an ethanol solution containing tetrabutyl titanate, then adding a silane coupling agent for heating reaction, and after the reaction is completed, cleaning and drying to obtain primarily modified linen fiber; and (2) adding the linen fiber modified for the first time into N, N-dimethylformamide, then adding hydroxyethyl acrylate and an initiator, carrying out a heating reaction, and after the reaction is completed, filtering, washing and drying to obtain the modified fiber. The composite material has excellent mechanical properties and thermal stability.

Description

Technical Field

[0001] This invention belongs to the field of polylactic acid composite material technology, specifically relating to a Eucommia ulmoides gum-based composite material and its preparation method. Background Technology

[0002] Polylactic acid (PLA) is a polyester polymer obtained by polymerizing lactic acid as the main raw material. It is a novel biodegradable thermoplastic polyester with excellent properties such as being environmentally friendly, non-toxic, and heat-resistant, and has a very broad application prospect. However, PLA itself is brittle and has poor impact resistance, which limits its application in various fields. Therefore, it needs to be modified to improve its toughness and flexibility.

[0003] Eucommia gum (EUG) is a natural biopolymer material derived from the leaves, bark, and fruit shells of the Eucommia tree. It is an environmentally friendly and renewable resource. EUG has strong crystallization ability, exhibiting the properties of an elastomer. Furthermore, it also displays the characteristics of a thermoplastic, making it easy to process. Based on EUG's unique rubber-plastic dual nature, depending on its degree of cross-linking, EUG can be used in plastics, rubber, and other fields. However, its low mechanical properties and poor impact strength limit its application range.

[0004] In existing technologies, toughening modification is often achieved by adding different mass fractions of EUG to PLA. However, the addition of EUG affects the mechanical properties and thermal stability of PLA to varying degrees. Therefore, a deeper investigation of PLA / EUG composite formulations is needed to further optimize the performance of PLA / EUG composite materials. Summary of the Invention

[0005] The primary objective of this invention is to provide a Eucommia ulmoides-based composite material with excellent mechanical properties and thermal stability.

[0006] The second objective of this invention is to provide a method for preparing Eucommia ulmoides gum-based composite materials, which is simple and easy to implement.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A Eucommia ulmoides gum-based composite material comprises the following raw materials in parts by weight: 70-80 parts polylactic acid, 10-20 parts Eucommia ulmoides gum, 3-8 parts modified fiber, 1-4 parts reinforcing filler, 0.4-0.8 parts antioxidant, and 1-3 parts crosslinking agent; The preparation process of the modified fiber is as follows: (1) The pretreated flax fiber was added to an ethanol solution containing tetrabutyl titanate, and then a silane coupling agent was added for heating reaction. After the reaction was completed, the flax fiber was washed and dried to obtain the first modified flax fiber. (2) Take the first modified flax fiber and add it to N,N-dimethylformamide, then add hydroxyethyl acrylate and initiator for heating reaction. After the reaction is completed, filter, wash and dry to obtain the modified fiber.

[0008] Furthermore, in step (1), the mass ratio of the ethanol solution to the pretreated flax fiber is 1:(0.02-0.05); the volume ratio of the tetrabutyl titanate to the ethanol solution is 1:(12-15); the mass fraction of the silane coupling agent in the ethanol solution is 1-2%; and the silane coupling agent is vinyltriethoxysilane.

[0009] Furthermore, the preparation process of the pretreated flax fiber is as follows: flax fiber is added to a sodium hydroxide solution with a mass fraction of 15-25%, soaked for 1-3 hours, and then filtered to obtain the pretreated flax fiber.

[0010] Furthermore, the heating reaction in step (1) is carried out at a temperature of 40-50°C for 5-10 hours.

[0011] Furthermore, in step (2), the mass ratio of the first modified flax fiber, hydroxyethyl acrylate, and initiator is 1:(0.1-0.15):(0.005-0.01); the initiator is azobisisobutyronitrile; the heating reaction temperature is 90-100℃ and the time is 1.5-3.5h.

[0012] Furthermore, the preparation process of the reinforcing filler is as follows: talc powder is added to an aqueous ethanol solution, and then γ-aminopropyltriethoxysilane is added for heating reaction. After the reaction is completed, the mixture is filtered, washed, and dried to obtain the reinforcing filler.

[0013] Furthermore, the mass ratio of talc to γ-aminopropyltriethoxysilane is 1:(0.1-0.2); the volume fraction of the ethanol aqueous solution is 75%; and the heating reaction temperature is 50-60℃ for 2-3 hours.

[0014] Furthermore, the weight-average molecular weight of the eucommia gum is (1-5) × 10⁻⁶. 5 KDa; the polylactic acid is poly-L-lactic acid or poly-D-lactic acid; the antioxidant is antioxidant 168 or antioxidant 1098; the crosslinking agent is dicumyl peroxide.

[0015] The preparation method of the above-mentioned Eucommia ulmoides gum-based composite material includes the following steps: According to the stated weight ratio, polylactic acid, eucommia gum, modified fiber, reinforcing filler, antioxidant, and crosslinking agent are mixed evenly, and then melt-extruded, granulated, and dried using a twin-screw extruder to obtain eucommia gum-based composite material.

[0016] Furthermore, the extrusion temperature of the twin-screw extruder is 150-180℃, and the rotation speed is 90-110 r / min; the drying temperature is 70-80℃, and the drying time is 6-9 h.

[0017] The beneficial technical effects of this invention are as follows: 1. The Eucommia ulmoides gum-based composite material of the present invention includes polylactic acid, Eucommia ulmoides gum, modified fiber, reinforcing filler and other components. The performance of the composite material was tested and found to have excellent mechanical properties and thermal stability.

[0018] 2. The modified fiber of this invention can improve the mechanical properties of composite materials. This invention uses tetrabutyl titanate and a silane coupling agent to treat flax fibers, forming stable Ti-O-Si covalent bonds on the surface of the flax fibers. This reduces the moisture absorption rate of the fibers and improves the weather resistance of the composite material. The vinyl groups introduced by the silane coupling agent undergo a graft copolymerization reaction with hydroxyethyl acrylate under the action of an initiator, forming flexible long chains of hydroxyethyl acrylate on the surface of the flax fibers. These flexible long chains improve the dispersibility of the fibers and, through physical interlocking, form an entangled network structure with polylactic acid, thereby improving the tensile strength, impact toughness, and other mechanical properties of the composite material.

[0019] 3. The addition of reinforcing fillers in this invention can improve the thermal stability of the composite material. By modifying talc powder with a silane coupling agent, the amino groups it contains reduce the surface energy of the talc powder, which helps to disperse it evenly in the material. In addition, the amino groups can form hydrogen bonds with the carbonyl groups in polylactic acid, playing a reinforcing role and improving the thermal stability of the material. Attached Figure Description

[0020] Figure 1 This is a SEM image of the modified fiber obtained in Example 1 of the present invention. Detailed Implementation

[0021] The following is a further detailed description of the present invention in conjunction with specific preferred embodiments, and it should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention. Specific conditions not specified in the embodiments are performed according to conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, all reagents or instruments used are conventional products obtained through commercial channels.

[0022] In the embodiments and comparative examples of this invention, the weight-average molecular weight of Eucommia ulmoides gum is 2 × 10⁻⁶. 5 KDa.

[0023] (I) Implementation Examples Example 1 This embodiment provides a Eucommia ulmoides gum-based composite material, comprising the following raw materials in parts by weight: 80 parts of poly-L-lactic acid, 20 parts of Eucommia ulmoides gum, 8 parts of modified fiber, 4 parts of reinforcing filler, 0.8 parts of antioxidant 168, and 3 parts of dicumyl peroxide (DCP).

[0024] The preparation process of the aforementioned modified fibers is as follows: (1) With a mass ratio of flax fiber to sodium hydroxide solution of 1:7, flax fiber was added to a sodium hydroxide solution with a mass fraction of 25% and soaked at room temperature for 3 hours. After filtration, the pretreated flax fiber was obtained. With a mass ratio of ethanol solution to pretreated flax fiber of 1:0.05, the pretreated flax fiber was added to an ethanol solution containing tetrabutyl titanate (volume ratio of tetrabutyl titanate to ethanol solution of 1:15). Vinyltriethoxysilane was then added, wherein the mass fraction of vinyltriethoxysilane in the ethanol solution was 2%. The reaction was carried out at 50°C for 5 hours. After the reaction was completed, the flax fiber was washed and dried to obtain the first modified flax fiber. (2) Based on the ratio of the first modified flax fiber, hydroxyethyl acrylate, azobisisobutyronitrile, and N,N-dimethylformamide (DMF) to N,N-dimethylformamide (DMF), the first modified flax fiber was added to DMF, followed by the addition of hydroxyethyl acrylate and azobisisobutyronitrile. The mixture was reacted at 100°C for 1.5 h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain the modified fiber. The SEM image of the modified fiber is shown in [reference needed]. Figure 1 Observations show that the modified fiber surface is covered by a uniform spherical structure. This unique morphology increases the fiber's specific surface area and surface roughness, which is crucial for improving its mechanical interlocking (anchoring effect) and chemical bonding ability with the matrix.

[0025] The preparation process of the above-mentioned reinforcing filler is as follows: Talc powder was added to a 75% (v / v) aqueous ethanol solution at a mass ratio of 1:0.2 to KH550, and then KH550 was added. The mixture was reacted at 60°C for 2 hours. After the reaction was completed, the mixture was filtered, washed, and dried to obtain the reinforcing filler.

[0026] This embodiment also provides a method for preparing the above-mentioned Eucommia ulmoides gum-based composite material, as follows: According to the stated weight ratio, poly-L-lactic acid, eucommia gum, modified fiber, reinforcing filler, antioxidant 168, and DCP are mixed evenly, and then extruded and granulated through a twin-screw extruder. The temperature of the twin-screw extruder is set in sections from the feed inlet to the die head as 150℃, 160℃, 170℃, 180℃, 175℃, 175℃, 170℃, 170℃, and 160℃, and the rotation speed is 110 r / min. Finally, it is dried at 80℃ for 6 hours to obtain the eucommia gum-based composite material.

[0027] Example 2 This embodiment provides a Eucommia ulmoides gum-based composite material, comprising the following raw materials in parts by weight: 73 parts poly-L-lactic acid, 16 parts Eucommia ulmoides gum, 5 parts modified fiber, 2 parts reinforcing filler, 0.6 parts antioxidant 168, and 2 parts DCP.

[0028] The preparation process of the aforementioned modified fibers is as follows: (1) With a mass ratio of flax fiber to sodium hydroxide solution of 1:7, flax fiber was added to a sodium hydroxide solution with a mass fraction of 20% and soaked at room temperature for 2 hours. After filtration, the pretreated flax fiber was obtained. With a mass ratio of ethanol solution to pretreated flax fiber of 1:0.04, the pretreated flax fiber was added to an ethanol solution containing tetrabutyl titanate (the volume ratio of tetrabutyl titanate to ethanol solution was 1:14). Vinyltriethoxysilane was then added, wherein the mass fraction of vinyltriethoxysilane in the ethanol solution was 1.5%. The reaction was carried out at 45°C for 7 hours. After the reaction was completed, the flax fiber was washed and dried to obtain the first modified flax fiber. (2) Based on the ratio of the first modified flax fiber, hydroxyethyl acrylate, azobisisobutyronitrile, and DMF of 1g:0.12g:0.008g:20mL, the first modified flax fiber was added to DMF, and then hydroxyethyl acrylate and azobisisobutyronitrile were added. The mixture was reacted at 95°C for 2h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain the modified fiber.

[0029] The preparation process of the above-mentioned reinforcing filler is as follows: Talc powder and γ-aminopropyltriethoxysilane (KH550) were added to a 75% (v / v) aqueous ethanol solution at a mass ratio of 1:0.15, followed by the addition of KH550. The mixture was reacted at 55°C for 2.5 h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain the reinforcing filler.

[0030] This embodiment also provides a method for preparing the above-mentioned Eucommia ulmoides gum-based composite material, as follows: According to the stated weight ratio, poly-L-lactic acid, eucommia gum, modified fiber, reinforcing filler, antioxidant 168, and DCP are mixed evenly, and then extruded and granulated using a twin-screw extruder. The temperature of the twin-screw extruder is set in sections from the feed inlet to the die head as 150℃, 160℃, 170℃, 180℃, 175℃, 175℃, 170℃, 170℃, and 160℃, and the rotation speed is 100 r / min. Finally, it is dried at 75℃ for 8 hours to obtain the eucommia gum-based composite material.

[0031] Example 3 This embodiment provides a Eucommia ulmoides gum-based composite material, comprising the following raw materials in parts by weight: 70 parts poly-D-lactic acid, 10 parts Eucommia ulmoides gum, 3 parts modified fiber, 1 part reinforcing filler, 0.4 parts antioxidant 1098, and 1 part DCP.

[0032] The preparation process of the aforementioned modified fibers is as follows: (1) With a mass ratio of flax fiber to sodium hydroxide solution of 1:7, flax fiber was added to a sodium hydroxide solution with a mass fraction of 15% and soaked at room temperature for 1 hour. After filtration, the pretreated flax fiber was obtained. With a mass ratio of ethanol solution to pretreated flax fiber of 1:0.02, the pretreated flax fiber was added to an ethanol solution containing tetrabutyl titanate (volume ratio of tetrabutyl titanate to ethanol solution of 1:12). Vinyltriethoxysilane was then added, wherein the mass fraction of vinyltriethoxysilane in the ethanol solution was 1%. The reaction was carried out at 40°C for 10 hours. After the reaction was completed, the flax fiber was washed and dried to obtain the first modified flax fiber. (2) Based on the ratio of the first modified flax fiber, hydroxyethyl acrylate, azobisisobutyronitrile, and DMF of 1g:0.1g:0.005g:20mL, the first modified flax fiber was added to DMF, followed by the addition of hydroxyethyl acrylate and azobisisobutyronitrile. The mixture was reacted at 90°C for 3.5h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain the modified fiber.

[0033] The preparation process of the above-mentioned reinforcing filler is as follows: Talc powder was added to a 75% (v / v) aqueous ethanol solution at a mass ratio of 1:0.1 to KH550, and then KH550 was added. The mixture was reacted at 50°C for 3 hours. After the reaction was completed, the mixture was filtered, washed, and dried to obtain the reinforcing filler.

[0034] This embodiment also provides a method for preparing the above-mentioned Eucommia ulmoides gum-based composite material, as follows: According to the stated weight ratio, poly-D-lactic acid, eucommia gum, modified fiber, reinforcing filler, antioxidant 1098, and DCP are mixed evenly, and then extruded and granulated using a twin-screw extruder. The temperature of the twin-screw extruder is set in sections from the feed inlet to the die head as 150℃, 160℃, 170℃, 180℃, 175℃, 175℃, 170℃, 170℃, and 160℃, and the rotation speed is 90 r / min. Finally, the mixture is dried at 0℃ for 9 hours to obtain the eucommia gum-based composite material.

[0035] (ii) Comparative Example Comparative Example 1 The difference between this comparative example and Example 1 is that flax fiber is used instead of the modified fiber, while the rest is the same as in Example 1.

[0036] Comparative Example 2 The difference between this comparative example and Example 1 is that talc powder is used instead of reinforcing filler, while the rest is the same as in Example 1.

[0037] The properties of the materials obtained by this invention are described below.

[0038] Tensile strength and elongation at break: Tested according to ASTM-D638, with a tensile rate of 5 mm / min and a test temperature of 23℃. Each sample was tested 5 times, and the average value was taken. The results are shown in Table 1. Notched impact strength of cantilever beams: The test was conducted according to ASTM D256-2024, with a notch size of 2 mm. Each sample was tested 5 times, and the average value was taken. The results are shown in Table 1. Thermogravimetric analysis: Thermogravimetric analysis was performed on each sample using a thermogravimetric analyzer. The weight of each sample was 8 mg. The detection conditions were: under a nitrogen atmosphere, the temperature was raised from room temperature to 600℃ at a heating rate of 20℃ / min, and the initial decomposition temperature was recorded. The results are shown in Table 1.

[0039] Table 1 As shown in Table 1, compared with Example 1, the mechanical properties of the composite material obtained by using flax fiber instead of the modified fiber in Comparative Example 1 are significantly reduced. These results indicate that the modified fiber obtained in this invention can improve the mechanical properties of the composite material. Further analysis shows that treating flax fiber with tetrabutyl titanate and a silane coupling agent forms stable Ti-O-Si covalent bonds on the surface of the flax fiber, which can reduce the moisture absorption rate of the fiber and improve the weather resistance of the composite material. The vinyl groups introduced by the silane coupling agent undergo a graft copolymerization reaction with hydroxyethyl acrylate under the action of an initiator, forming flexible long chains of hydroxyethyl acrylate on the surface of the flax fiber. These flexible long chains can improve the dispersibility of the fiber and form an entangled network structure with polylactic acid through physical interlocking, thereby improving the tensile strength, impact toughness, and other mechanical properties of the composite material.

[0040] Compared to Example 1, the thermal stability of the composite material obtained in Comparative Example 2, which used talc instead of the reinforcing filler, was significantly reduced. These results indicate that the reinforcing filler obtained in this invention can improve the thermal stability of the composite material. Further analysis shows that after modifying talc with a silane coupling agent, the amino groups it contains reduce the surface energy of the talc, which helps to ensure uniform dispersion in the material. Furthermore, the amino groups can form hydrogen bonds with the carbonyl groups in polylactic acid, playing a reinforcing role and improving the thermal stability of the material.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. The basic principles and main features of the present invention have been described above with specific implementation schemes. Based on the present invention, some modifications or substitutions can be made, but these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of protection claimed by the present invention.

Claims

1. A Eucommia ulmoides-based composite material, characterized in that, The raw materials include the following parts by weight: 70-80 parts polylactic acid, 10-20 parts eucommia gum, 3-8 parts modified fiber, 1-4 parts reinforcing filler, 0.4-0.8 parts antioxidant, and 1-3 parts crosslinking agent; The preparation process of the modified fiber is as follows: (1) The pretreated flax fiber was added to an ethanol solution containing tetrabutyl titanate, and then a silane coupling agent was added for heating reaction. After the reaction was completed, the flax fiber was washed and dried to obtain the first modified flax fiber. (2) Take the first modified flax fiber and add it to N,N-dimethylformamide, then add hydroxyethyl acrylate and initiator for heating reaction. After the reaction is completed, filter, wash and dry to obtain the modified fiber.

2. The Eucommia ulmoides gum-based composite material according to claim 1, characterized in that, In step (1), the mass ratio of the ethanol solution to the pretreated flax fiber is 1:(0.02-0.05); the volume ratio of the tetrabutyl titanate to the ethanol solution is 1:(12-15); the mass fraction of the silane coupling agent in the ethanol solution is 1-2%; and the silane coupling agent is vinyltriethoxysilane.

3. The Eucommia ulmoides gum-based composite material according to claim 2, characterized in that, The preparation process of the pretreated flax fiber is as follows: flax fiber is added to a sodium hydroxide solution with a mass fraction of 15-25% and soaked for 1-3 hours. After filtration and separation, the pretreated flax fiber is obtained.

4. The Eucommia ulmoides gum-based composite material according to claim 1, characterized in that, The heating reaction in step (1) is carried out at a temperature of 40-50℃ for 5-10 hours.

5. The Eucommia ulmoides gum-based composite material according to claim 1, characterized in that, In step (2), the mass ratio of the first modified flax fiber, hydroxyethyl acrylate, and initiator is 1:(0.1-0.15):(0.005-0.01); the initiator is azobisisobutyronitrile; the heating reaction temperature is 90-100℃ and the time is 1.5-3.5h.

6. The Eucommia ulmoides gum-based composite material according to claim 1, characterized in that, The preparation process of the reinforcing filler is as follows: talc powder is added to an aqueous ethanol solution, and then γ-aminopropyltriethoxysilane is added for heating reaction. After the reaction is completed, the filler is filtered, washed, and dried to obtain the reinforcing filler.

7. The Eucommia ulmoides gum-based composite material according to claim 6, characterized in that, The mass ratio of talc to γ-aminopropyltriethoxysilane is 1:(0.1-0.2); the volume fraction of the ethanol aqueous solution is 75%; the heating reaction temperature is 50-60℃ and the time is 2-3h.

8. The Eucommia ulmoides gum-based composite material according to claim 1, characterized in that, The weight-average molecular weight of the Eucommia ulmoides gum is (1-5)×10. 5 KDa; the polylactic acid is poly-L-lactic acid or poly-D-lactic acid; the antioxidant is antioxidant 168 or antioxidant 1098; the crosslinking agent is dicumyl peroxide.

9. A method for preparing the Eucommia ulmoides gum-based composite material according to any one of claims 1-8, characterized in that, Includes the following steps: According to the stated weight ratio, polylactic acid, eucommia gum, modified fiber, reinforcing filler, antioxidant, and crosslinking agent are mixed evenly, and then melt-extruded, granulated, and dried using a twin-screw extruder to obtain eucommia gum-based composite material.

10. The method for preparing the Eucommia ulmoides gum-based composite material according to claim 9, characterized in that, The extrusion temperature of the twin-screw extruder is 150-180℃, and the rotation speed is 90-110 r / min; the drying temperature is 70-80℃, and the drying time is 6-9 h.

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