A method for dispersing a multi-component filler for polylactic acid composites

Abstract

The application discloses a dispersion method for a multi-component filler of a polylactic acid composite material, and belongs to the technical field of polylactic acid material modification. The dispersion method comprises the following steps: forming an adsorption layer on the surface of millimeter-level polylactic acid particles by using an interface regulator, and then blending the polylactic acid particles with the adsorption layer on the surface with micro or nano fillers to form a mixture, wherein the interface regulator comprises dimethyl silicone oil with a viscosity of 500-1500 cSt. The application realizes uniform dispersion of the fillers in different scales. The polylactic acid and filler mixed system dispersed by the method can be used for melt blending extrusion and molding to obtain polylactic acid composite materials, and the toughness and strength of the polylactic acid composite materials can be improved.

Description

Technical Field

[0001] This invention relates to the field of polylactic acid material modification technology, and more specifically, to a method for dispersing multi-component fillers for polylactic acid composite materials. Background Technology

[0002] Polylactic acid (PLA) shows great potential as a replacement for traditional petroleum-based plastics due to its bio-based origin and biodegradability, especially in electrical insulation applications. However, PLA's molecular structure gives it high rigidity and brittleness, resulting in poor overall toughness. Its notched impact strength is typically low, and its unnotched impact strength is below 20 kJ / m², which cannot meet the stringent toughness requirements of applications such as low-voltage insulated electrical metering box housings (typically requiring an unnotched impact strength of at least 42 kJ / m²).

[0003] To improve the toughness of PLA, a common method is to add toughening agents and perform melt blending modification, such as using core-shell toughening agents (e.g., methyl methacrylate-butadiene-styrene copolymer, MBS). While this method can improve the impact toughness of PLA to some extent, it is often accompanied by a significant "toughness inversion" phenomenon, meaning that key mechanical properties such as tensile strength and flexural strength of the material will decrease significantly (typically by 30% to 40%). Furthermore, in traditional melt blending, polylactic acid particles and toughening fillers are directly melt-mixed. Due to the high viscosity of the polymer melt and the differences in interfacial tension between different components, the toughening fillers (especially nano- or micron-sized fillers) are difficult to disperse uniformly and are prone to agglomeration, forming stress concentration points. This not only weakens the toughening effect but may even degrade other properties of the material (such as dielectric properties).

[0004] Therefore, there is an urgent need in this field to develop a method that can effectively improve the cross-size dispersion of micro- and nano-scale fillers in millimeter-scale PLA matrices, significantly enhancing the toughness of PLA while maintaining or even improving the original tensile and flexural strength of PLA to the maximum extent. This has important practical significance and commercial value for broadening the application of PLA in high-performance fields such as electrical insulation. Summary of the Invention

[0005] To address the aforementioned problems in the prior art, this invention provides a method for dispersing multi-component fillers in polylactic acid composite materials, comprising the following steps:

[0006] Millimeter-scale polylactic acid particles and micron- or nano-scale fillers are available respectively;

[0007] An adsorption layer is formed on the surface of the millimeter-sized polylactic acid particles using an interface modifier;

[0008] Polylactic acid particles with an adsorption layer formed on their surface are blended with the micron or nano-sized filler to form a mixture.

[0009] The interface modifier includes dimethyl silicone oil with a viscosity of 500-1500 cSt.

[0010] In some embodiments of the present invention, the dimethyl silicone oil comprises polydimethylsiloxane or its derivatives or AK diffusion oil.

[0011] In some embodiments of the present invention, the viscosity of the AK diffusion oil is 500~1500 cSt.

[0012] In some embodiments of the present invention, the molecular weight M of polydimethylsiloxane is... w It ranges from 20,000 to 100,000 g / mol.

[0013] In some embodiments of the present invention, the ratio of polylactic acid to interface modifier by weight is as follows: 90 parts polylactic acid and 0.5 to 2.0 parts interface modifier.

[0014] In some embodiments of the present invention, the ratio of polylactic acid to interface modifier by weight is as follows: 90 parts polylactic acid and 0.5 to 1.5 parts interface modifier.

[0015] In some embodiments of the present invention, the interface modifier is introduced in the form of submicron-sized droplets, which spread on the surface of the millimeter-sized polylactic acid particles to form an adsorption layer, wherein the droplet diameter is 0.2~1μm.

[0016] In some embodiments of the present invention, the filler is a toughening agent MBS with an average particle size of 100~500 nm.

[0017] In some embodiments of the present invention, the toughening agent MBS is formulated relative to polylactic acid in the following proportions by weight: 90 parts polylactic acid and 5-30 parts toughening agent MBS.

[0018] In some embodiments of the present invention, the mixture has a pre-composite structure of millimeter-core polylactic acid-micron or nanoshell filler.

[0019] On the other hand, the present invention provides a method for preparing a polylactic acid composite material, the method comprising: forming a mixture of polylactic acid and filler using the dispersion method of the present invention, and obtaining a polylactic acid composite material by melt extrusion and injection molding.

[0020] The present invention has the following beneficial technical effects compared with the prior art:

[0021] 1. Achieving uniform dispersion of fillers across scales: This invention utilizes interface modifiers (including dimethyl silicone oil with a viscosity of 500~1500 cSt) to mediate the uniform adsorption and coating of micro- and nano-sized fillers (such as MBS) on the surface of millimeter-sized PLA particles, forming a "core-shell" pre-composite structure of millimeter-core polylactic acid-micron or nano-shell fillers. This pre-dispersion state is maintained during subsequent melt blending, significantly improving the uniformity of filler dispersion in the final PLA matrix and effectively avoiding agglomeration problems.

[0022] 2. Synergistic Improvement of Mechanical Properties of Polylactic Acid Composites: Due to the uniform dispersion of the filler and the optimized interface, stress transfer between the matrix and the filler can be promoted more effectively. Simultaneously, the uniformly dispersed toughening phase of the filler can more effectively induce matrix yielding and absorb impact energy. In a specific embodiment of this invention, the PLA / MBS composite material prepared using the dispersion method of this invention before melt blending improves PLA toughness while effectively alleviating the problem of PLA strength reduction caused by MBS filler, thus effectively overcoming the "strength-toughness inversion" problem and achieving synergistic enhancement of mechanical properties.

[0023] 3. Enhanced interfacial compatibility and stability: The interfacial layer formed by the interfacial regulator improves the interfacial compatibility between PLA and fillers (such as MBS) with large polarity differences, enhances interfacial bonding force, reduces the possibility of phase separation and interfacial debonding, and improves the overall structural stability and long-term service performance of the composite material.

[0024] 4. Simple process and good versatility: The adsorption and coating step in the dispersion method of the present invention can be completed in conventional mixing equipment. The subsequent extrusion and molding processes are compatible with traditional methods, making it easy to achieve industrial production. Moreover, this method is applicable to composite systems of various fillers (toughening agents, rigid fillers, functional fillers, etc.) and PLA. Attached Figure Description

[0025] Figure 1 SEM images of the fracture surfaces of polylactic acid composite materials prepared in Comparative Example 2 and Examples 1 to 3, wherein: (a) Comparative Example 2; (b) Example 1; (c) Example 2; (d) Example 3.

[0026] Figure 2 The graph shows the unnotched impact strength test results of the polylactic acid composite materials prepared in Comparative Examples 1 and 2, and Examples 1 to 3.

[0027] Figure 3 The figure shows the tensile strength test results of the polylactic acid composite materials prepared in Comparative Examples 1 and 2, and Examples 1 to 3.

[0028] Figure 4 The graph shows the flexural strength test results of the polylactic acid composite materials prepared in Comparative Examples 1 and 2, and Examples 1 to 3. Detailed Implementation

[0029] The present invention will now be described in detail with reference to specific embodiments and exemplary models. These specific descriptions and exemplary models are for illustrative purposes only and do not constitute any limitation on the scope of protection of the present invention.

[0030] The filler dispersion method in the polylactic acid composite material of the present invention is aimed at cross-size dispersion of millimeter-sized polylactic acid particles and micron- or nano-sized fillers. Before melt blending, the millimeter-sized PLA particles are first surface-treated with an interface modifier with low surface energy and good spreadability to form an interface modifier adsorption layer. Then, the adsorption layer is used to induce micron- or nano-sized fillers (such as MBS toughening agent) to preferentially and uniformly adhere to the surface of PLA particles, forming a pre-composite structure of "millimeter core (PLA) - micro / nano shell (filler)". Finally, the mixture with this pre-composite structure is melt-extruded and molded.

[0031] The micron or nano-sized filler described in this invention can be one or more fillers suitable for polylactic acid (PLA) bases, with an average particle size ranging from 100 to 500 nm, preferably from 100 to 200 nm. In an exemplary embodiment of this invention, the filler is selected from the toughening agent MBS commonly used in the art. The ratio of the toughening agent MBS to PLA by weight is as follows: 90 parts PLA, 5-30 parts toughening agent MBS, preferably 10-20 parts toughening agent MBS. An exemplary embodiment of this invention is illustrated using 10 parts toughening agent MBS as an example. In this invention, to avoid the initial agglomeration of the micron or nano-sized filler, it can be pre-dispersed, for example, using a high-speed air jet mill.

[0032] The interface modifier described in this invention can be a dimethyl silicone oil with a low molecular weight and low viscosity, such as polydimethylsiloxane or its derivatives. A polydimethylsiloxane or its derivative with a viscosity of 500-1500 cSt can be selected, with a preferred viscosity range of 900-1100 cSt. The molecular weight M of the polydimethylsiloxane... w The concentration is 20,000 to 100,000 g / mol, with a preferred molecular weight range of 25,000 to 80,000 g / mol. In an optional embodiment, the interface modifier may be selected from those with a viscosity of 500 cSt and a molecular weight of M. w The polydimethylsiloxane is approximately 25,000 g / mol. In another optional embodiment, the interface modifier may be selected from those with a viscosity of 1000 cSt and a molecular weight M. w The polydimethylsiloxane has a concentration of approximately 60,000 g / mol. In another optional embodiment, the interface modifier may be selected from those with a viscosity of 1500 cSt and a molecular weight M.w The polydimethylsiloxane content is approximately 80,000 g / mol.

[0033] In addition, the interface modifier of the present invention may also be an AK diffusion oil with a viscosity of 500~1500 cSt, which can be purchased. In the exemplary embodiment of the present invention, WACKER AK-1000 diffusion oil is selected.

[0034] The viscosity values ​​described in this invention refer to the viscosity values ​​at 25°C.

[0035] The content of the interface regulator described in this invention is calculated in parts by weight, and the ratio relative to polylactic acid is: 90 parts polylactic acid, 0.5-2.0 parts interface regulator, preferably 0.5-1.5 parts. To improve the dispersion uniformity of the interface regulator during the adsorption and coating process, the interface regulator described in this invention can be introduced by physical or chemical treatment to form submicron-sized droplets, allowing the interface regulator to spread and form an adsorption layer on the surface of millimeter-sized polylactic acid particles. For example, submicron-sized droplets can be formed by atomization or droplet addition. The diameter of the formed submicron-sized droplets can be 0.2-1 μm, preferably in the range of 200-500 nm.

[0036] In the dispersion method of the present invention, millimeter-sized PLA particles may be added to a dynamic mixing device, such as a customized dynamic mixing reactor or a high-speed mixer, after pretreatment or without pretreatment.

[0037] Under stirring, the metered interface modifier is uniformly introduced into the mixing equipment via atomization or dropwise addition, allowing it to spread on the surface of the PLA particles and form a uniform interface modifier adsorption layer. This process can be carried out at room temperature or a slightly elevated temperature (e.g., 50±2℃), but the temperature must be below the glass transition temperature of PLA, and the time must be sufficient for the interface modifier to distribute uniformly. The stirring rotor speed is controlled at a low range (e.g., 300±20 rpm) to avoid intense frictional heat.

[0038] While maintaining stirring, slowly add the metered pre-dispersed micron or nano-sized filler (such as MBS powder) into the mixing device. Due to the presence of an interface modifier adsorption layer on the surface of the polylactic acid (PLA) particles, its low surface energy preferentially wets and adsorbs the filler particles. Simultaneously, the interface modifier layer acts as a "binder," selectively and uniformly fixing the micron or nano-sized filler particles to the PLA particle surface through van der Waals forces, hydrogen bonds (if PLA pretreatment introduces hydroxyl groups), and other forces. The temperature can be adjusted appropriately during this process, for example, slowly heating to 70±3℃ at a rate of 0.5℃ / min. Simultaneously, the stirring rate can be adjusted appropriately, for example, increasing it to 500±30 rpm, to optimize adhesion efficiency and uniformity, achieving a target coverage of 80-90%.

[0039] After the above steps, a millimeter-scale PLA particle precomposite with micron or nano fillers (such as MBS) uniformly coated on the surface is obtained, which forms a "millimeter core (PLA)-nano shell (such as MBS)" structure. In this structure, the interfacial adsorption layer formed by the interfacial regulator mediates this cross-scale coating.

[0040] After obtaining the PLA particle precomposite with surface-coated filler using the dispersion method of the present invention, polylactic acid composite materials can be prepared using melt blending granulation and molding processes of polylactic acid-based composite materials known in the art.

[0041] In a specific embodiment of the present invention, the PLA particle precomposite with surface-coated filler obtained by the dispersion method of the present invention is added to a twin-screw extruder for melt blending and granulation.

[0042] In the melt blending extrusion step, temperature gradients are set for each zone of the extruder, for example: Zone 1 (feeding section) 120±10℃, Zone 2 (melting section) 175±5℃, Zone 3 (homogenization section) 180±5℃, and the die head temperature is set as needed. Screw speed and other parameters are adjusted according to the equipment and material system to ensure sufficient plasticization and mixing, while minimizing excessive degradation or migration of the interface modifier under high shear. Since the filler is pre-dispersed uniformly on the surface of PLA particles, this stage of melt blending mainly achieves the melting of the PLA matrix and the homogenization of macroscopic materials, greatly reducing the possibility of secondary agglomeration of filler in the melt. The extruded molten material is rapidly solidified by an air-cooled conveying system and then pelletized to obtain composite particles of PLA and filler with a particle size of Φ2×3 mm.

[0043] After drying the PLA and filler composite particles obtained from extrusion pelleting, the desired products are prepared by injection molding (or other molding methods such as tableting, blown film, etc.).

[0044] In the injection molding process, the following injection molding parameters can be used: the barrel temperature is set sequentially from the feed end to the nozzle as 160±5℃, 175±5℃, 185±3℃, and 180±2℃; the mold temperature is controlled at 50±2℃; and appropriate injection rates (e.g., 60±5 cm³ / s), holding pressures (e.g., 80±5 MPa), and times (e.g., holding pressure 10±2 s, cooling 20±2 s) are set. The injection-molded product can undergo post-treatment, such as standing in a constant temperature and humidity chamber (e.g., 25±2℃, 60±5% RH) for 24±2 h to release internal stress and stabilize the material structure.

[0045] The present invention will be further described in detail below through exemplary embodiments and comparative examples.

[0046] Example 1

[0047] The polylactic acid composite filler dispersion method and the steps for preparing polylactic acid composite materials using this dispersion method in this embodiment are as follows:

[0048] Step 1: Raw material preparation and pretreatment

[0049] 1.1 PLA: Polylactic acid (PLA, 4032D) from Nature Works, USA, with a particle size of 3~4mm was selected.

[0050] 1.2 MBS filler: MBS (S-2023) powder from Mitsubishi Chemicals, Japan was selected. The MBS powder was processed using a high-speed air jet mill at an air pressure of 0.6±0.05 MPa for 3 min to obtain monodisperse particles with an average particle size of 100-200 nm.

[0051] 1.3 Interface regulator: German WACKER AK-1000 diffusion oil with a viscosity of 1000 cSt was selected.

[0052] Step 2: AK-1000 diffusion oil coats PLA particles and fillers.

[0053] 90 parts by weight of PLA were added to a high-speed mixer. Under the conditions of rotor speed of 300±20 rpm and temperature of 40±2℃, 0.5 parts by weight of AK-1000 diffusion oil were ultrasonically atomized for 5 min at a frequency of 2 MHz and a power of 50W to form submicron droplets with a particle size of 200~500 nm. These droplets were then uniformly introduced into the PLA and stirred for 20 min to spread on the surface of the PLA particles and form a uniform diffusion oil adsorption layer.

[0054] While maintaining stirring, slowly add 10 parts by weight of pre-dispersed MBS powder into the mixer. At this time, slowly raise the temperature to 70°C at a rate of 0.5°C / min, and increase the stirring rate to 500±30 rpm, stirring for 30 min to obtain a mixture containing PLA particle precomposite with MBS filler uniformly adsorbed on the surface.

[0055] Step 3: Melt Blending Extrusion

[0056] The mixture obtained in step 2 is added to a twin-screw extruder for melt blending and granulation. The temperatures of each zone of the extruder are set as follows: Zone 1 (feeding section) 130℃, Zone 2 (melting section) 170℃, and Zone 3 (homogenization section) 180℃. Screw speed and other parameters are adjusted according to the equipment and material system. The extruded molten material is rapidly solidified by an air-cooled conveying system and then pelletized to obtain PLA / MBS composite particles with a particle size of Φ2×3 mm.

[0057] Step 4: Injection Molding

[0058] The composite particles obtained after extrusion pelletizing were dried and added to an injection molding machine. The barrel temperature of the injection molding machine was set sequentially from the feed end to the nozzle as 165℃, 175℃, 182℃, and 182℃; the mold temperature was controlled at 50℃; the injection rate was 60±5 cm³ / s; the holding pressure was 80MPa; and the holding time was (holding pressure 10s, cooling 20s). The injection-molded product with a length of 80 mm, a width of 10 mm, and a thickness of 4 mm was placed in a constant temperature and humidity chamber at 25±2℃ and 60±5% RH for 24 hours to release internal stress and stabilize the material structure.

[0059] Example 2

[0060] The filler dispersion method of the polylactic acid composite material in this embodiment differs from that in Example 1 only in the ratio of the interface regulator to polylactic acid. Specifically, the polylactic acid is 90 parts by weight and the AK-1000 diffusion oil is 1.0 part by weight.

[0061] The other steps and conditions of the dispersion method in Example 2 are the same as those in Example 1. The steps and conditions for preparing polylactic acid composite materials using the dispersion method of Example 2 are also the same as those in Example 1.

[0062] Example 3

[0063] The difference between the filler dispersion method of the polylactic acid composite material in this embodiment and that in Example 1 is only in the ratio of the interface regulator to polylactic acid. Specifically, the polylactic acid is 90 parts by weight and the AK-1000 diffusion oil is 1.5 parts by weight.

[0064] The other steps and conditions of the dispersion method in Example 3 are the same as those in Example 1. The steps and conditions for preparing polylactic acid composite material articles using the dispersion method of Example 3 are also the same as those in Example 1.

[0065] Comparative Example 1

[0066] Comparative Example 1 uses the same millimeter-sized polylactic acid raw material as Example 1, the difference being that: Comparative Example 1 did not use any interface modifier to treat the millimeter-sized polylactic acid particles, nor did it add toughening agent MBS.

[0067] Polylactic acid raw material was added to a twin-screw extruder for melt granulation. The other preparation steps of the polylactic acid material in Comparative Example 1 (including melt blending, extrusion granulation, and injection molding) were the same as those in Example 1.

[0068] Comparative Example 2

[0069] The only difference between Comparative Example 2 and Example 1 is that the PLA particles were not treated with an interface regulator before being mixed with the filler MBS, but were directly melt-blended. All other conditions and preparation steps (including melt blending, extrusion pelletizing, and injection molding) were the same as in Example 1.

[0070] To further demonstrate the beneficial technical effects of the filler dispersion method of the present invention, the performance of polylactic acid composite materials prepared by specific embodiments and comparative examples of the present invention will be tested and evaluated below, including scanning electron microscopy (SEM), unnotched impact strength test, tensile strength test, and flexural strength test.

[0071] 1. Observation using scanning electron microscopy (SEM)

[0072] The fracture surfaces of the polylactic acid composite materials of Examples 1 to 3 and Comparative Example 2 were observed using scanning electron microscopy. The observed SEM images are shown below. Figure 1 As shown, in Figure 1 In the diagram, region (a) corresponds to Comparative Example 2; region (b) corresponds to Example 1; region (c) corresponds to Example 2; and region (d) corresponds to Example 3. SEM results show that Comparative Example 2, which did not use an interface modifier for dispersion, exhibits significant phase separation. The degree of interface separation in Example 1 is reduced, with only minor separation observed in localized areas. The cross-section of Example 2 shows a better dispersion state, with the MBS dispersed phase particles or their pores being fine and densely distributed within the PLA continuous phase matrix. This uniform dispersion structure facilitates the effective transfer and dispersion of stress at the interface, thereby more effectively absorbing impact energy and achieving a toughening effect. This microstructure, combined with the impact strength (95.19 kJ / m²) of Example 2 described below, demonstrates that the interface modifier can effectively improve interfacial compatibility.

[0073] Although the MBS phase dispersion uniformity was further improved in Example 3, the dispersed phase particle size was smaller than that of the blend in Example 2. Furthermore, as can be seen from the tensile strength test data described below, the tensile strength of Example 3 decreased (46.64 MPa). In summary, Examples 1 to 3 all improved the dispersion state of MBS in the PLA matrix, with Example 2 showing the best dispersion effect.

[0074] 2. Unnotched impact strength test

[0075] According to the national standard GB / T 1043.2-2018, the impact strength of unnotched simply supported beams was tested on the specimens prepared in Comparative Examples 1 and 2 and Examples 1 to 3. The test specimens were cuboids with a length of 80 mm, a width of 10 mm, and a thickness of 4 mm. A 4 J pendulum was used to repeatedly test the specimens prepared in the same example or comparative example 10 times, and the average value was taken. The test results are as follows. Figure 2 As shown.

[0076] according to Figure 2 It can be seen that the impact strength of the polylactic acid composite material prepared in Comparative Example 1 is 18.24 kJ / m², while the impact strength of Comparative Example 2 is increased to 71.41 kJ / m², which is 291% higher than that of pure PLA without MBS, indicating that MBS can improve the toughness of PLA. By introducing 0.5-1.5 parts of diffusion oil AK-1000 as an interface modifier to form an adsorption layer on the surface of polylactic acid particles before mixing with filler MBS, the impact strength of the blend system is further improved. Among them, the impact strength of Example 2 is as high as 95.19 kJ / m², which is 33.30% higher than that of Comparative Example 2, indicating that AK diffusion oil as an interface modifier effectively inhibits the aggregation behavior of MBS particles, making the dispersion of MBS in the matrix more uniform, thereby improving toughness.

[0077] 3. Tensile strength test

[0078] The tensile strength of the specimens prepared in Comparative Examples 1 and 2, and Examples 1 and 3, was tested using a tensile testing machine. The tensile strength was tested according to the national standard GB / T 1040.1-2018. The test specimens were dumbbell-shaped samples with a gauge length of 80 mm, a width of 10 mm, and a thickness of 4 mm. The specimens were tested repeatedly five times at a tensile rate of 2 mm / min, and the average value was taken. The test results are as follows: Figure 3 As shown.

[0079] Depend on Figure 3 As can be seen, the tensile strength of Comparative Example 1 (pure PLA) is 66.11 MPa, while the tensile strength of Comparative Example 2 decreases to 41.90 MPa, indicating that the addition of MBS reduces the rigidity of PLA. However, the PLA / MBS / AK blends (Examples 1 to 3) formed by treating millimeter-sized PLA particles with 0.5–1.5 parts of an interface modifier (diffusion oil AK-1000) and then mixing them with nano-sized fillers showed a recovery in tensile strength, reaching 49.35 MPa, 49.51 MPa, and 46.64 MPa, respectively. This indicates that improving the dispersibility of MBS in the PLA matrix (i.e., enhancing compatibility) and reducing agglomeration through an interface modifier can further improve the material's plastic deformation capacity and toughness, effectively alleviating the "strength-toughness inversion" problem.

[0080] 4. Bending strength test

[0081] The bending strength of the specimens prepared in Comparative Examples 1 and 2, and Examples 1 and 3 was tested using a bending strength testing machine. The bending strength was tested according to the national standard GB / T 9341-2008. The test specimens were cuboids with a length of 80 mm, a width of 10 mm, and a thickness of 4 mm. The specimens were tested repeatedly five times at a speed of 2 mm / min, and the average value was taken. The test results are as follows: Figure 4 As shown.

[0082] Depend on Figure 4 It can be seen that Comparative Example 1 (PLA without MBS) exhibits the highest flexural strength, at 103.40 MPa. In contrast, the flexural strength of Comparative Example 2 decreases to 69.71 MPa. After treating millimeter-sized PLA particles with 0.5-1.5 parts of AK diffusion oil and then mixing them with nano-sized fillers, the flexural strength recovers to 73.70-77.48 MPa, indicating that AK diffusion oil, acting as an interface modifier, improves MBS dispersibility and enhances interfacial compatibility, thereby increasing flexural strength. Specifically, in Example 2, the group using 1.0 part of AK diffusion oil (Group D) achieves a flexural strength as high as 77.48 MPa, representing an 11.15% increase compared to Comparative Example 2.

[0083] In summary, the filler dispersion method in the polylactic acid composite material provided by the present invention uses an interface regulator to form an adsorption layer on the surface of millimeter-sized PLA particles, and then mixes the polylactic acid particles with the adsorption layer on the surface with micron or nano-sized filler powder to form a mixture of polylactic acid and filler, thereby improving the dispersibility of the filler. When this dispersion method is used to prepare PLA composite materials, it can successfully achieve a synergistic improvement in the toughness and tensile strength properties of PLA composite materials.

[0084] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the term "comprising" does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0085] The above embodiments are only used to illustrate the technical solutions of the present invention and should not be used to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments or equivalent substitutions can be made to some of the technical features without departing from the essence and scope of the present invention. Such modifications or equivalent substitutions still fall within the scope of the present invention.

Claims

1. A method for preparing a polylactic acid composite material, characterized in that, The preparation method includes: Millimeter-sized polylactic acid particles and micron- or nano-sized fillers are provided, wherein the filler is a toughening agent MBS; An adsorption layer is formed on the surface of the millimeter-sized polylactic acid particles using an interface modifier, wherein the interface modifier comprises dimethyl silicone oil with a viscosity of 500~1500 cSt, and the interface modifier is introduced in the form of submicron-sized droplets. Polylactic acid particles with an adsorption layer formed on their surface are blended with the micron or nano-scale filler to form a mixture, the mixture having a pre-composite structure of millimeter-core polylactic acid-micron or nano-shell filler; The mixture is melt extruded and injection molded to obtain a polylactic acid composite material.

2. The preparation method according to claim 1, wherein, The dimethyl silicone oil includes polydimethylsiloxane or its derivatives or AK diffusion oil.

3. The preparation method according to claim 2, wherein, The viscosity of the AK diffusion oil is 900~1100 cSt.

4. The preparation method according to claim 2, wherein, The molecular weight M of polydimethylsiloxane w It ranges from 20,000 to 100,000 g / mol.

5. The preparation method according to claim 1 or 3, wherein, The ratio of polylactic acid to interface modifier by weight is as follows: 90 parts polylactic acid and 0.5 to 2.0 parts interface modifier.

6. The preparation method according to claim 5, wherein, The ratio of polylactic acid to interface modifier by weight is as follows: 90 parts polylactic acid and 0.5 to 1.5 parts interface modifier.

7. The preparation method according to claim 1, wherein, The diameter of the submicron-sized droplets is 0.2~1μm.

8. The preparation method according to claim 1, wherein, The toughening agent MBS has an average particle size of 100~500 nm.

9. The preparation method according to claim 8, wherein, The toughening agent MBS is formulated in the following proportions relative to polylactic acid, by weight: 90 parts polylactic acid and 5-30 parts toughening agent MBS.

Images