Full-biodegradable ramie modified material and preparation method thereof

Abstract

The invention provides a full-biodegradable ramie modified material and a preparation method thereof, and belongs to the technical field of full-biodegradable materials. The ramie modified material comprises the following raw materials: ramie powder, poly (butylene adipate-co-terephthalate), polylactic acid, a coupling agent, absolute ethyl alcohol and cyclopentyl oil. The preparation method comprises the following steps: mixing the ramie powder and the coupling agent, performing primary mixing in a stirring state, then adding the polylactic acid and the poly (adipic acid) / butylene terephthalate, performing secondary mixing, finally adding the absolute ethyl alcohol and the cyclopentyl oil, and performing tertiary mixing to obtain a mixture; and carrying out extrusion and injection molding on the mixture to obtain the ramie modified material. According to the invention, cellulose molecules in ramie can perfectly realize two-phase interface blending and eutectic melting with matrix resin, high-mass-fraction filling of cellulose can be realized, the performance of the ramie modified material is stable, and the requirements of different application scenes are met.

Description

Technical Field

[0001] This invention belongs to the field of fully biodegradable materials technology, and particularly relates to a fully biodegradable ramie modified material and its preparation method. Background Technology

[0002] In recent years, the use of plastics has been increasing, and plastic products are ubiquitous in our daily lives, providing great convenience. However, with the rapid increase in plastic production, the post-processing of waste plastics and the resulting environmental pollution have attracted increasing attention from various countries. Waste plastics decompose very slowly in nature, taking decades or even centuries to completely decompose, causing environmental pollution. Therefore, fully biodegradable plastics have received increasing attention from scholars and industry professionals both domestically and internationally. Currently, the main matrix resins applicable to fully biodegradable plastics are PBAT (polybutylene adipate / terephthalate), PLA (polylactic acid), PHA (polyhydroxyalkanoates), and PPC (polypropylene carbonate), etc. Fully biodegradable plastics prepared using these resins can be widely used in supermarket shopping bags, takeout containers, agricultural mulch films, and other fields. However, research has found that fully biodegradable plastics prepared using only one matrix resin are not only expensive, but also fail to meet product requirements in terms of mechanical properties, thermal properties, barrier properties, and production costs, presenting numerous problems.

[0003] Ramie possesses characteristics such as high fiber yield, rich lignin content, high fiber strength, and complete biodegradability, making it a renewable resource and thus possessing the potential to be a fully biodegradable material. However, due to the large number of hydrogen bonds on the surface of cellulose, hemicellulose, and lignin in ramie, which exhibit strong polarity, while PBAT has weak polarity, the combination of ramie and PBAT resins leads to poor compatibility during mixing, easily resulting in stratification, a higher number of unevenly distributed crystal points in the product, and negatively impacting product performance, leading to a decline in mechanical properties. Therefore, how to combine ramie and PBAT to prepare a fully biodegradable plastic is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, this invention provides a fully biodegradable ramie modified material and its preparation method.

[0005] To achieve the above objectives, the present invention provides the following technical solution: One of the technical solutions of the present invention: This invention provides a fully biodegradable ramie modified material, which comprises the following raw materials: ramie powder, polybutylene adipate / terephthalate (PBAT), polylactic acid (PLA), coupling agent, anhydrous ethanol, and cyclopentadiene oil.

[0006] Beneficial effects: In the preparation of fully biodegradable plastics, the present invention adds cyclopentyl oil, which can volatilize and generate bubbles during the preparation of ramie modified materials, forming a porous structure, reducing the material density while maintaining mechanical strength; moreover, the porous structure formed can increase the contact area of ​​microorganisms and enhance oxygen permeability during the subsequent degradation process, further improving the degradation rate.

[0007] Anhydrous ethanol, as a polar solvent, can effectively dissolve the raw materials or intermediates of biodegradable plastics, promoting a uniform depolymerization reaction.

[0008] Furthermore, the amount of poly(butylene adipate) / (terephthalate) and polylactic acid added is 70 wt.%-87 wt.% of the total mass of the raw materials; The amount of ramie powder added is 10wt.%-30wt.% of the total mass of the raw materials; The coupling agent is added at a rate of 0.5 wt.% to 0.8 wt.% of the total mass of the raw materials. The amount of anhydrous ethanol added is 2.0 wt.%-3.0 wt.% of the total mass of the raw materials; in this application, the amount of anhydrous ethanol (≥99.9%) added must be precisely controlled within 2.0 wt.%-3.0 wt.%, as excessive amounts will slow down the degradation rate and reduce the mechanical strength of the product. The amount of cyclopentyl oil added is 0.5 wt.%-2.0 wt.% of the total mass of the raw materials. Excessive addition will lead to a decrease in the strength of the product or excessive degradation.

[0009] Furthermore, the mass ratio of poly(adipate) / butylene terephthalate to polylactic acid is 0.6-0.8. Furthermore, the ramie powder has a particle size of 500-700 mesh.

[0010] Furthermore, the coupling agent is a silane coupling agent or an aluminate compound, preferably LS60, KH550 or KH560.

[0011] The second technical solution of the present invention: The present invention also provides a method for preparing a fully biodegradable ramie modified material, comprising the following steps: (1) The ramie powder and coupling agent are mixed once under stirring, then the poly(butylene adipate / terephthalate) and polylactic acid are added for a second mixing, and finally anhydrous ethanol and cyclopentyl oil are added for a third mixing to obtain a mixture. (2) The ramie modified material is obtained by extruding and injection molding the mixture.

[0012] Furthermore, the stirring speed in step (1) is 30 rpm; The mixing time for one cycle is 15 minutes; The secondary mixing time is 5 minutes; The three mixing times were 4 minutes.

[0013] Furthermore, in step (1), the ramie powder is mixed with the coupling agent under stirring conditions, and the stirring speed is 20 rpm.

[0014] Furthermore, in step (2), the extrusion process is configured with the following temperatures for each zone of the extruder: 170°C, 170°C, 170°C, 175°C, 175°C, 175°C, 175°C, 175°C, 175°C, 175°C; rotation speed: 150 rpm; main feed frequency: 4.0 Hz; and main motor current: 13 A. In this invention, the mixture is melted and plasticized by the mechanical shearing and compression action of the extruder, ensuring material uniformity.

[0015] Furthermore, in step (2), the injection molding process is set with the temperature of each zone of the injection molding machine at 180 ℃, 190 ℃, and 200 ℃, the injection pressure at 125 bar, and the injection flow rate at 60%.

[0016] In preparing fully biodegradable ramie modified materials, the present invention can add a nucleating agent to induce crystallization, thereby further increasing the crystallization temperature of the ramie modified materials.

[0017] Furthermore, the amount of nucleating agent added is 0.1%-0.3%, and the addition of nucleating agent can increase the crystallization temperature from 68°C to 86°C.

[0018] The beneficial effects of this invention compared to the prior art are as follows: This invention targets the unique crystalline structure of ramie molecules, and designs formulations and adjusts process parameters for modified ramie materials. This allows cellulose molecules in ramie to achieve perfect blending and melting at the two-phase interface with the matrix resin, enabling the filling of ramie cellulose with a high-quality proportion, stabilizing sample performance, reducing production costs, and enhancing market competitiveness.

[0019] This invention involves adding a coupling agent during the preparation of ramie-modified materials to activate ramie powder. The activated ramie powder can then be used to fill the matrix resin PBAT / PLA to prepare a fully biodegradable polymer material. Furthermore, the ramie-modified materials prepared by this invention exhibit tensile strength and flexural strength as high as 58.4 MPa and 110.8 MPa, respectively, and an impact strength of up to 40.6 KJ / m. 2 It can meet the practical needs of different customer groups. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 Infrared spectra of the surface chemical structures of natural ramie powder in this invention and ramie powder activated by coupling agents LS60, KH550 and KH560 in Examples 1, 9 and 10, respectively; Figure 2 Figure 1 shows the SEM images of the cross-sections of the ramie modified materials prepared in Examples 12-14 and the comparative examples of the present invention. Figure 2a is the SEM image of the cross-section of the ramie modified material prepared in the comparative example, Figure 2b is the SEM image of the cross-section of the ramie modified material prepared in Example 12, Figure 2c is the SEM image of the cross-section of the ramie modified material prepared in Example 14, and Figure 2d is the SEM image of the cross-section of the ramie modified material prepared in Example 13. Figure 3 This is a schematic diagram showing the Vicat softening point of the ramie-modified materials prepared in Examples 1-9 of the present invention; Figure 4 The bar chart shows the tensile strength of the ramie-modified materials prepared in Examples 1-9 of this invention. Figure 5 The bar chart shows the flexural strength of the ramie-modified materials prepared in Examples 1-9 of this invention. Figure 6 The bar chart shows the impact strength of the ramie-modified materials prepared in Examples 1-9 of this invention. Detailed Implementation

[0022] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0023] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0024] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0025] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0026] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0027] All raw materials used in the following embodiments of the present invention are commercially available.

[0028] Example 1 A method for preparing a fully biodegradable ramie-modified material includes the following steps: (1) Preheat the high-speed mixer. When the temperature of the high-speed mixer reaches 120°C, add 10wt.% of ramie powder with a particle size of 500-700 mesh, adjust the speed to 20rpm, add 0.4wt.% of coupling agent KH560, then adjust the speed to 30rpm and mix for 15min. Then add 86.8wt.% of PLA and PBAT resin (where the mass ratio of PBAT to PLA is 0.8) and continue mixing for 5min. Finally, add 2.0wt.% of anhydrous ethanol and 0.8wt.% of cyclopentyl oil and mix for 4min. Discharge the mixture to obtain the mixture.

[0029] (2) Turn on the power to the extruder and preheat it. Set the temperature of each zone to 170 ℃, 170 ℃, 170 ℃, 175 ℃, 175 ℃, 175 ℃, 175 ℃, 175 ℃, 175 ℃, 175 ℃, 175 ℃, 175 ℃, 175 ℃, 150 rpm, 4.0 Hz, and 13 A. Put the above mixture into the extruder for extrusion to obtain molten material.

[0030] (3) Set the temperature of each zone of the injection molding machine to 180℃, 190℃ and 200℃, the injection pressure to 125 bar and the injection flow rate to 60%, and inject the above molten material into a sample of ramie modified material through the injection molding machine.

[0031] Examples 2-9 provide a method for preparing a fully biodegradable ramie modified material. The difference between the preparation steps and those in Example 1 is that the mass ratio of PBAT and PLA is different, and the amount of ramie powder and coupling agent added is different. The mass ratio of PBAT and PLA and the amount of ramie powder and coupling agent added in Examples 2-9 are shown in Table 1. The remaining raw materials and preparation methods are the same as in Example 1.

[0032] Table 1 PBAT / PLA Ramie powder (wt.%) Coupling agent (wt.%) Example 1 0.8 10 0.4 Example 2 0.8 20 0.6 Example 3 0.8 30 0.8 Example 4 0.7 10 0.6 Example 5 0.7 20 0.8 Example 6 0.7 30 0.4 Example 7 0.6 10 0.8 Example 8 0.6 20 0.4 Example 9 0.6 30 0.6

[0033] Example 10 A method for preparing a fully biodegradable ramie modified material differs from Example 1 in that the coupling agent is KH550; The remaining steps are the same as in Example 1.

[0034] Example 11 A method for preparing a fully biodegradable ramie modified material differs from Example 1 in that the coupling agent is LS60; The remaining steps are the same as in Example 1.

[0035] Example 12 A method for preparing a fully biodegradable ramie-modified material differs from Example 1 in that: The mass ratio of PLA to PBAT is 6:4, the amount of ramie powder added is 30 wt.%, and the amount of coupling agent added is 0.4 wt.%. The remaining steps are the same as in Example 1.

[0036] Example 13 A method for preparing a fully biodegradable ramie modified material differs from Example 12 in that the amount of coupling agent added is 0.6 wt.%. The remaining steps are the same as in Example 12.

[0037] Example 14 A method for preparing a fully biodegradable ramie-modified material differs from Example 12 in that the amount of coupling agent added is 0.8 wt.%. The remaining steps are the same as in Example 12.

[0038] Comparative Example A method for preparing a fully biodegradable ramie modified material differs from Example 12 in that the amount of coupling agent added is 0. The remaining steps are the same as in Example 12.

[0039] Performance testing: 1. Infrared spectroscopy test The ramie modified materials prepared in Examples 1, 10, and 11 were pulverized into fine powder of approximately 100 mesh using a crusher. Sample powder and KBr were weighed out at a mass ratio of 1:100 and ground evenly in an agate mortar. Simultaneously, natural ramie powder and KBr were weighed out at a mass ratio of 1:100 and ground evenly in an agate mortar. The potassium bromide tableting method was used, and the tableted samples were tested using a Fourier transform infrared spectrometer (FTIR) (Nicolet Impact 420, USA). The infrared spectra of the surface chemical structures of natural ramie powder and ramie powder activated with LS60, KH550, and KH560, respectively, are shown below. Figure 1 As shown.

[0040] Depend on Figure 1 It can be seen that, compared with untreated natural ramie powder, ramie powder activated by LS60 has a higher content of 2850 cm⁻¹. -1 There is a noticeable additional absorption peak at 3400 cm⁻¹, which is due to the stretching vibration of the methylene group, indicating that LS60 has been successfully grafted onto ramie flour, and that esters, organic acids, and other substances in the plant fiber have been removed by the alkaline solution; at a wavenumber of 3400 cm⁻¹... -1 The absorption peak at position -OH is very broad in the infrared spectrum because ramie fibers have a high number of hydroxyl groups on their surface. However, the absorption peak at this wavenumber is significantly narrowed in ramie powder after activation treatment with KH550 and KH560, indicating a decrease in the polarity of ramie fibers. Furthermore, Figure 1 Displayed at a wavenumber of 1030cm -1 There is a distinct vibration peak at this point, which is the stretching vibration peak of Si-O, indicating that coupling agents KH550 and KH560 can effectively coat the ramie powder.

[0041] 2. Microscopic morphology The ramie modified materials prepared in Examples 12-14 and the comparative examples were subjected to brittle fracture in liquid nitrogen. After the surface and cross-section of the ramie modified materials were sputter-coated with gold, the microstructure of the samples was observed using a field emission scanning electron microscope (FESEM) (Gemini SEM 300, Zeiss, Germany) to observe the dispersion of the powder in the matrix resin. The accelerating voltage was 3.0 kV.

[0042] SEM images of the cross-sections of the ramie-modified materials prepared in Examples 12-14 and the comparative examples of this invention are shown below. Figure 2As shown, in the ramie modified material without coupling agent (Figure a), a large amount of ramie powder agglomerated in the matrix resin, and many coarse fibers were even visible. Furthermore, obvious voids were present in the matrix resin, indicating phase separation. When the amount of coupling agent KH560 added was 0.4 wt.% (Figure b), the ramie fibers, activated by KH560, exhibited reduced polarity and were better distributed in the matrix resin. When the amount of coupling agent KH560 added was 0.8 wt.% (Figure c), the surface of the ramie powder was coated with excessive KH560. The hydrophilic groups of KH560 were exposed because they could not directly participate in the reaction with the ramie, resulting in partial discontinuity in the cross-section of the sample. When the amount of coupling agent KH560 added is 0.6 wt.% (as shown in Figure d), the -OH on the surface of ramie powder is fully combined with the silanol bond of KH560, the powder is basically in a weakly hydrophilic state, has good compatibility with the matrix resin, and no ramie powder agglomeration or appearance on the surface of the matrix resin was found.

[0043] 3. Vicat softening point test The thermal stability of the ramie-modified materials prepared in Examples 1-9 was analyzed using a heat distortion Vicat temperature tester (XRW-300C-3, Chengde Jinbo Electronics Co., Ltd.). Heat distortion tests were conducted according to ASTM D64, with a load of 0.45 MPa. Samples were placed flat, measuring 64 mm × 10 mm × 4 mm, and the heating rate was 120 ℃ / h. Each sample group was measured three times, and the average value was taken.

[0044] The Vicat softening points of the ramie-modified materials prepared in Examples 1-9 are shown in the following diagrams. Figure 3 As shown, by Figure 3 It is known that when the ramie powder content is 10 wt.%, the Vicat softening point of the material is relatively high because ramie fiber has a loose structure with many internal pores, making it easy to deform under certain pressure conditions. When the PBAT content in the matrix resin is high, the Vicat softening point of the material is relatively low because the melting point of PBAT itself is only about 107℃, far lower than that of PLA, making it easier to deform. When the PBAT / PLA ratio is 0.7, the ramie powder filling amount is 10 wt.%, and the coupling agent content is 0.6 wt.%, the material has good thermal stability, and the heat distortion temperature can reach 83.4℃. This application can also add a small amount of nucleating agent to the modified material to induce crystallization in order to improve crystallization efficiency, further increasing the crystallization temperature of the modified material.

[0045] 4. Melt Flow Index Melt Flow Rate (MFR) is a numerical value that indicates the flowability of a polymer material during processing. It represents the mass of plastic that flows through a specific cavity per unit time under certain conditions. A higher melt flow rate indicates better flowability of the plastic material, and vice versa.

[0046] The ramie modified materials prepared in Examples 1-9 were subjected to flow-out through a circular tube with a diameter of 2.1 mm at 190°C and 2.16 kg pressure. The mass of melt flowing out within 10 min was calculated, and the results are shown in Table 2.

[0047] Table 2 20s (g) 10 min (g) Example 1 0.743 22.3 Example 2 0.660 19.8 Example 3 0.587 17.6 Example 4 0.683 20.5 Example 5 0.623 18.7 Example 6 0.547 16.4 Example 7 0.627 18.8 Example 8 0.603 18.1 Example 9 0.557 16.7 The melt index of pure PLA resin is approximately 30 g / 10 min, while that of pure PBAT resin is 4.5 g / 10 min. Table 2 shows that when the mass ratio of PBAT / PLA in the matrix resin decreases from 0.8 to 0.6, the melt index of the ramie-modified material also decreases accordingly. When the overall proportion of ramie powder increases from 10 wt.% to 30 wt.%, the flowability of the ramie-modified material deteriorates. This is mainly because the random arrangement of ramie powder in the matrix resin hinders its flow. Increasing the proportion of coupling agent can, on the one hand, fully coat the powder particles, giving the ramie powder good compatibility with the matrix resin; on the other hand, the coupling agent also acts as a lubricant, which is beneficial to improving the flowability of the ramie-modified material.

[0048] 5. Mechanical properties Mechanical properties are a key technical indicator of plant fiber / polymer composites, largely determining their service life. Consequently, numerous studies have reported on the mechanical properties of these composites.

[0049] This invention tests the tensile properties of the ramie-modified materials prepared in Examples 1-9 according to GB / T 1040-2018, at a testing speed of 50 mm / min; tests the flexural properties of the ramie-modified materials prepared in Examples 1-9 according to GB / T 9431-2008, at a testing speed of 50 mm / min; and tests the impact properties of the ramie-modified materials prepared in Examples 1-9 according to GB / T 1843-2008. Tensile strength and flexural strength of the ramie-modified materials are tested using a tensile testing machine, and notched impact strength is tested using a cantilever beam impact testing machine according to GB / T 1043-2008. Each sample is tested 5 times, and the average value is taken. Tensile strength is as follows: Figure 4 As shown, the bending strength is as follows Figure 5 As shown, the impact strength is as follows Figure 6 As shown.

[0050] pass Figure 4-6 It can be seen that the modified ramie material prepared by this invention exhibits significantly improved tensile strength and flexural strength under the combined action of the matrix resin, ramie powder, and modifier. The tensile strength can reach up to 58.4 MPa, and the flexural strength can reach up to 110.8 MPa. Regarding impact strength, because PBAT possesses a certain degree of toughness, the material also demonstrates superior impact strength, reaching up to 40.6 KJ / m². 2 It far exceeds the standard limit and can meet the actual needs of different customer groups.

[0051] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A fully biodegradable ramie-modified material, characterized in that, The ramie modified material includes the following raw materials: Ramie powder, polybutylene adipate / terephthalate, polylactic acid, coupling agent, anhydrous ethanol and cyclopentadiene oil.

2. The fully biodegradable ramie modified material according to claim 1, characterized in that, The amount of poly(butylene adipate) / (terephthalate) and polylactic acid added is 70 wt.%-87 wt.% of the total mass of the raw materials. The amount of ramie powder added is 10wt.%-30wt.% of the total mass of the raw materials; The coupling agent is added at a rate of 0.5 wt.% to 0.8 wt.% of the total mass of the raw materials. The amount of anhydrous ethanol added is 2.0 wt.%-3.0 wt.% of the total mass of the raw materials. The amount of cyclopentyl oil added is 0.5 wt.%-2.0 wt.% of the total mass of the raw materials.

3. The fully biodegradable ramie modified material according to claim 2, characterized in that, The mass ratio of poly(adipate) / butylene terephthalate and polylactic acid is 0.6-0.

8.

4. The fully biodegradable ramie modified material according to claim 2, characterized in that, The ramie powder has a particle size of 500-700 mesh.

5. The fully biodegradable ramie modified material according to claim 2, characterized in that, The coupling agent is a silane coupling agent or an aluminate compound.

6. A method for preparing a fully biodegradable ramie-modified material as described in any one of claims 1-5, characterized in that, Includes the following steps: (1) After mixing the ramie powder and coupling agent, the mixture is kneaded once under stirring. Then, the poly(butylene adipate / terephthalate) and polylactic acid are added for a second kneading. Finally, anhydrous ethanol and cyclopentyl oil are added and kneaded three times to obtain the mixture. (2) The ramie modified material is obtained by extruding and injection molding the mixture.

7. The method for preparing the fully biodegradable ramie-modified material according to claim 6, characterized in that, The stirring speed in step (1) is 20-40 rpm; The mixing time for one cycle is 15-30 minutes; The secondary mixing time is 5-8 minutes; The three mixing times are 3-5 minutes.

8. The method for preparing the fully biodegradable ramie modified material according to claim 6, characterized in that, In step (2), the extrusion process is set with the following temperatures for each zone: 170 ℃, 170 ℃, 170 ℃, 175 ℃, 175 ℃, 175 ℃, 175 ℃, 175 ℃, 175 ℃, 175 ℃, 175 ℃, 175 ℃, 150 rpm, 4.0 Hz for the main feed frequency, and 13 A for the main machine current.

9. The method for preparing the fully biodegradable ramie-modified material according to claim 6, characterized in that, In step (2), the injection molding process is set with temperatures of 180 ℃, 190 ℃, and 200 ℃ in each zone, injection pressure of 125 bar, and injection flow rate of 60%.

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