阅读说明：本技术 一种新的刚性粒子/植物纤维/聚丙烯复合材料制备方法 (Novel preparation method of rigid particle/plant fiber/polypropylene composite material ) 是由 姜爱菊 熊有为 卓可圣 陶枫 张保丰 于 2021-09-09 设计创作，主要内容包括：一种新的刚性粒子/植物纤维/聚丙烯复合材料制备方法,涉及绿色复合材料的制备技术领域,包括以下步骤：(1)植物纤维表面预处理；(2)刚性纳米粒子与硅烷偶联剂分别进行水解,而后密封、超声震荡下混合成接枝植物纤维溶液；(3)对植物纤维进行刚性纳米粒子接枝改性；(4)复合材料共混并成型。本发明提高了植物纤维与聚丙烯基体之间的界面相容性能,制备的刚性纳米粒子接枝植物纤维增强聚丙烯复合材料整体性能优异,其拉伸性能、弯曲性能等力学性能有明显改善；冲击韧性相对其他复合材料也有改善；而且充分利用可再生植物资源,制备的复合材料具有可降解特性,具备环境友好性；同时复合材料成本低廉,工艺简单,利于大规模生产。(A new preparation method of rigid particle/plant fiber/polypropylene composite material relates to the technical field of green composite material preparation, and comprises the following steps: (1) pretreating the surface of the plant fiber; (2) respectively hydrolyzing the rigid nano particles and a silane coupling agent, and then mixing the hydrolyzed rigid nano particles and the silane coupling agent into a grafted plant fiber solution under sealing and ultrasonic oscillation; (3) carrying out rigid nanoparticle grafting modification on the plant fiber; (4) and (3) blending and forming the composite material. The invention improves the interface compatibility between the plant fiber and the polypropylene matrix, the prepared rigid nanoparticle grafted plant fiber reinforced polypropylene composite material has excellent overall performance, and the mechanical properties such as tensile property, bending property and the like are obviously improved; the impact toughness is also improved compared with other composite materials; moreover, renewable plant resources are fully utilized, and the prepared composite material has the characteristics of degradability and environmental friendliness; meanwhile, the composite material is low in cost, simple in process and beneficial to large-scale production.)

1. A novel preparation method of rigid particle/plant fiber/polypropylene composite material is characterized by comprising the following steps:

(1) surface pretreatment of plant fibers: soaking plant fiber in alkali solution, washing with water to neutral, and drying;

(2) respectively hydrolyzing the rigid nano particles and a silane coupling agent, and then mixing the hydrolyzed rigid nano particles and the silane coupling agent into a grafted plant fiber solution under sealing and ultrasonic oscillation;

(3) carrying out rigid nanoparticle grafting modification on plant fibers: putting the plant fiber treated in the step (1) into the solution prepared in the step (2), and infiltrating for 1-6 hours under sealing and ultrasonic vibration to obtain the plant fiber grafted with the rigid nanoparticles;

(4) blending and molding the composite material: and (4) drying the grafted plant fiber obtained in the step (3), blending the dried grafted plant fiber with polypropylene resin through a melting method, and preparing a sample.

2. The method for preparing the novel rigid particle/plant fiber/polypropylene composite material according to claim 1, wherein in the step (1), the plant fiber is jute fiber, sisal fiber, flax fiber or bamboo fiber.

3. The method for preparing the novel rigid particle/plant fiber/polypropylene composite material according to claim 1, wherein in the step (1), the alkali solution is a sodium hydroxide solution with a mass concentration of 3-20%; the soaking time is 1-6 hours, and the temperature is 25-50 ℃.

4. The method for preparing the novel rigid particle/plant fiber/polypropylene composite material according to claim 1, wherein in the step (1), the drying temperature is 60-100 ℃ and the drying time is 5-10 h.

5. The method for preparing the novel rigid particle/plant fiber/polypropylene composite material according to claim 1, wherein in the step (2), the solution for respectively hydrolyzing the rigid nanoparticles and the silane coupling agent is a mixture of deionized water and absolute ethyl alcohol in a mass ratio of 0.25-0.75: 1.

6. The method for preparing the novel rigid particle/plant fiber/polypropylene composite material according to claim 1, wherein in the step (2), the concentrations of the rigid nanoparticle and the silane coupling agent are respectively 1-8 wt%; the hydrolysis temperature is 15-50 ℃, and the high-speed stirring time of the magnetic stirrer is 10-60 min.

7. The method for preparing the novel rigid particle/plant fiber/polypropylene composite material according to claim 1, wherein in the step (2), the ultrasonic oscillation temperature of the mixture of the rigid nanoparticle solution and the silane coupling agent hydrolysis solution is 15-50 ℃ and the ultrasonic oscillation time is 10-60 min.

8. The method for preparing the novel rigid particle/plant fiber/polypropylene composite material as claimed in claim 1, wherein the ultrasonic vibration temperature in step (3) is 15-50 ℃.

9. The method for preparing the novel rigid particle/plant fiber/polypropylene composite material according to claim 1, wherein in the step (4), the melt blending mode is roll mixing, banburying blending or extrusion blending; the forming mode is hot press forming or injection molding.

Technical Field

The invention relates to the technical field of preparation of green composite materials, in particular to a novel preparation method of a rigid particle/plant fiber/polypropylene composite material.

Background

With the development of society and science and technology, the awareness of environmental protection is gradually improved, and the requirements of people on materials are higher and higher. The development of the polymer material in the future is green and harmonious. The plant fiber has higher strength due to the huge hydrogen bond network structure, is a reinforcing filler of a plurality of high polymer materials, and has irreplaceable effect on solving the energy and environmental protection problems by using the plant fiber as a composite material of the filler.

At present, researches on different parameters of plant fibers, such as composite process, catalyst and modified chemical concentration, fiber mass fraction, fiber length, fiber treatment mode and the like, are hot spots. The plant fiber reinforced polypropylene composite material is more and more favored by people, the poor compatibility of the plant fiber and the polypropylene leads to the reduction of the mechanical property of the composite material, the improvement of the compatibility of the plant fiber and the polymer and the research of toughening of the plant fiber/polymer composite material have high application value. The interface compatibility between the fibrilia and the resin matrix can be improved to a certain extent by carrying out physical and chemical methods and nano particle modification on the fibrilia, and the mechanical property of the composite material is improved. However, after the fibrilia is modified by a physical or chemical method, the effect of enhancing the mechanical property of the composite material is limited, and the impact property of the composite material is obviously reduced while the tensile strength and the bending strength of the composite material are improved. In addition, some modification methods have high cost, high pollution and difficult guarantee of modification effect, and the defects restrict the application of the modification methods. The nano particle modification can not only better improve the interface compatibility of the fibrilia and the resin matrix, but also reduce the reduction degree of the impact strength of the fibrilia-reinforced composite material modified by the nano particle modification compared with other modification methods.

Most of the existing methods for modifying nanoparticles are high-pressure impregnation, surface grafting, mechanical blending and the like, and the methods directly compound the nanoparticles and fibers, so that the nanoparticles are easy to agglomerate and the modification effect cannot be fully exerted. Some students graft nano silicon dioxide on plant fibers in an in-situ deposition mode, but the operation process is complicated and industrialization is not easy to realize.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a novel preparation method of a rigid particle/plant fiber/polypropylene composite material.

The technical scheme is as follows: the method comprises the following steps:

(1) surface pretreatment of plant fibers: soaking plant fiber in alkali solution, washing with water to neutral, and drying;

(2) respectively hydrolyzing the rigid nano particles and a silane coupling agent, and then mixing the hydrolyzed rigid nano particles and the silane coupling agent into a grafted plant fiber solution under sealing and ultrasonic oscillation;

(3) carrying out rigid nanoparticle grafting modification on plant fibers: putting the plant fiber treated in the step (1) into the solution prepared in the step (2), and infiltrating for 1-6 hours under sealing and ultrasonic vibration to obtain the plant fiber grafted with the rigid nanoparticles;

(4) blending and molding the composite material: and (4) drying the grafted plant fiber obtained in the step (3), blending the dried grafted plant fiber with polypropylene resin through a melting method, and preparing a sample.

Preferably, in the step (1), the plant fiber is jute fiber, sisal fiber, flax fiber or bamboo fiber.

Preferably, in the step (1), the alkali liquor is a sodium hydroxide solution with the mass concentration of 3-20%; the soaking time is 1-6 hours, and the temperature is 25-50 ℃.

Preferably, in the step (1), the drying temperature is 60-100 ℃ and the drying time is 5-10 h.

Preferably, in the step (2), the solutions for respectively hydrolyzing the rigid nanoparticles and the silane coupling agent are mixed by deionized water and absolute ethyl alcohol in a mass ratio of 0.25-0.75: 1.

Preferably, in the step (2), the concentrations of the rigid nanoparticles and the silane coupling agent are respectively 1 wt% -8 wt%, the hydrolysis temperature is 15-50 ℃, and the high-speed stirring time of the magnetic stirrer is 10-60 min.

Preferably, in the step (2), the ultrasonic oscillation temperature of the mixed rigid nanoparticle solution and the silane coupling agent hydrolysis solution is 15-50 ℃, and the ultrasonic oscillation time is 10-60 min.

Preferably, in the step (3), the ultrasonic oscillation temperature is 15-50 ℃.

Preferably, in the step (4), the melt blending mode is open mixing, banburying blending or extrusion blending; the forming mode is hot press forming or injection molding.

The invention has the beneficial effects that:

1: the method of the invention improves the interface compatibility between the plant fiber and the polypropylene matrix, the prepared rigid nanoparticle grafted plant fiber reinforced polypropylene composite material has excellent overall performance, and the mechanical properties such as tensile property, bending property and the like are obviously improved; the impact toughness is also improved compared with other composite materials;

2: according to the invention, renewable plant resources are fully utilized, and the prepared composite material has the degradable characteristic and is environment-friendly;

3: the composite material prepared by the invention has low cost, rich raw material sources and simple process, and is beneficial to large-scale production.

Drawings

FIG. 1: is a schematic diagram of an extrusion blending composite material in the embodiment 1 of the invention.

Detailed Description

The present invention will be described in further detail below with reference to specific embodiments and with reference to the attached drawings.

Example 1: the preparation method of the novel rigid particle/plant fiber/polypropylene composite material comprises the following steps:

(1) surface pretreatment of plant fibers: simply carding the purchased long-fiber jute fiber, drying for 5 hours at-0.1 Pa and 80 ℃ in a vacuum drying oven, adding 15 percent by weight of sodium hydroxide solution into 200g of the fiber, soaking for 4 hours at 50 ℃, then cleaning the jute fiber by using distilled water until the jute fiber is neutral, dispersing and air-drying, and drying for 5 hours at-0.1 Pa and 80 ℃ in the vacuum drying oven to obtain the alkali-treated jute fiber (short for AJF).

(2) Preparation of a suspension for graft-modified fibers: preparing mixed solution of deionized water and absolute ethyl alcohol, wherein the mixing mass ratio of the deionized water to the absolute ethyl alcohol in the mixed solution is 480 g: 720 g; weighing 50 g of hydrophobic nano-silica (with the particle size of 20nm and the weight of 99 percent), adding the hydrophobic nano-silica into a prepared mixed solution of deionized water and absolute ethyl alcohol, and stirring and mixing the mixture for 30 minutes at a high speed by using a magnetic stirrer to obtain a nano-silica hydrolysis solution with the mass concentration of 4 percent; weighing 50 g of silane coupling agent (KH570), adding into the prepared mixed solution of deionized water and absolute ethyl alcohol, and stirring and mixing at high speed for 30 minutes by using a magnetic stirrer; adding the solution for dissolving the silane coupling agent into the nano silicon dioxide solution, and oscillating the mixed solution for 15min by using an ultrasonic cleaner to obtain the suspension for grafting the jute.

(3) Carrying out rigid particle grafting modification on plant fibers: putting the AJF obtained in the step (1) into the suspension obtained in the step (2), sealing, and carrying out vibration infiltration treatment in an ultrasonic cleaner for 4 hours; obtaining the nanometer silicon dioxide grafted jute fiber.

(4) Drying the nano-silica grafted jute fiber prepared in the step (3) at 80 ℃ for 5 hours, drying polypropylene granules at 80 ℃ for 5 hours, preheating a double-screw extruder to 160-210 ℃, setting the temperature of a machine head at 210 ℃, fixing the rotating speed of a screw at 135 revolutions per minute, adding the polypropylene granules into a hopper, and adding jute long fiber from the sixth section to the seventh section of the screw, as shown in figure 1; the main feeding frequency is 2.0, the traction speed is 200 r/min, and the mass of the jute fiber used in one minute is divided by the mass of the extrusion material of the extruder, so that the mass fraction of the jute fiber in the composite material is 30.6 wt%.

Example 2: the difference from example 1 was that "main feeding frequency 2.5, drawing speed 250 rpm", which was divided the mass of the jute fiber used in one minute by the mass of the extrusion material of the extruder, resulted in a mass fraction of the jute fiber in the composite material of 20.8 wt%.

Example 3: the difference from example 1 was that "main feeding frequency 3.5, drawing speed 300 rpm", which was divided the mass of the jute fiber used in one minute by the mass of the extrusion material of the extruder, resulted in the mass fraction of the jute fiber in the composite material being 14.8 wt%.

Example 4: the difference from example 1 was that "main feeding frequency 5.0, drawing speed 400 rpm", which was divided the mass of the jute fiber used in one minute by the mass of the extrusion material of the extruder, resulted in the mass fraction of the jute fiber in the composite material being 9.8 wt%.

Example 5: compared with the example 4, the difference is the mixed liquid of the deionized water and the absolute ethyl alcohol configured in the step (2), "the mixing mass ratio of the deionized water to the absolute ethyl alcohol in the mixed liquid is 230 g: 345 g", the main feeding frequency is 5.0, the traction speed is 400 r/min, and the mass of the jute fiber used in one minute is divided by the mass of the extrusion material of the extruder, so that the mass fraction of the jute fiber in the composite material is 9.8 wt%.

Example 6: compared with the example 4, the difference is that the mixed liquid of the deionized water and the absolute ethyl alcohol is prepared in the step (2), "the mixing mass ratio of the deionized water to the absolute ethyl alcohol in the mixed liquid is 980 g: 1470 g", the main feeding frequency is 5.0, the traction speed is 400 r/min, and the mass of the jute fiber used in one minute is divided by the mass of the extrusion material of the extruder, so that the mass fraction of the jute fiber in the composite material is 9.8 wt%.

Composite Performance testing

The obtained composite was subjected to tensile properties test (specimen size: effective length: 50mm, width: 12.54mm, thickness: 3.2mm, dumbbell specimen), bending properties test (specimen size: length: 127.5mm, width: 12.4mm, thickness: 3.2mm, rectangular parallelepiped specimen) and impact properties test (specimen size: width: 4.22mm, height: 12.5mm, thickness: 3.2mm, notch width: 2mm) according to ASTM D638, ASTM D790-10, and I05.5, respectively. The performance test was carried out under the same conditions using 10 wt% of ungrafted jute fiber reinforced composite material (abbreviated as UJF/PP) and 10 wt% of alkali-treated jute fiber reinforced composite material (abbreviated as AJF/PP) as control groups. The test results are shown in table 1.

TABLE 1 test results of the properties of composites prepared according to the examples of the present invention and conventional techniques

From the data analysis of examples 4, 5 and 6 in table 1, it can be seen that the concentrations of the nanosilicon dioxide hydrolysis solution and the silane coupling agent hydrolysis solution of the suspension for graft-modified fibers in step (2) also have some influence on the mechanical properties of the composite material.

In example 5, the concentrations of the nano-silica hydrolysis solution and the silane coupling agent hydrolysis solution are both 8 wt%, and experiments show that when the mass concentration of the hydrolysis solution is high, stirring is difficult, so that hydrolysis is insufficient; when the grafted plant fiber is soaked, a layer of thick nano silicon dioxide is formed on the surface of the fiber; the dust is easy to fall off and cause dust emission in the drying and fiber carding processes; and the concentration is too high, the hydrolysis of the nano silicon dioxide and the coupling agent is insufficient, the grafting effect is influenced, and nano silicon dioxide particles which do not participate in grafting agglomerate in a matrix to cause stress concentration, so that the mechanical property of the composite material is reduced.

In example 6, the concentrations of the nano silica hydrolysis solution and the silane coupling agent hydrolysis solution were both 2 wt%, and the effect of enhancing the overall performance of the composite material was not significant due to the low silica content.

In example 4, the mass concentrations of the nano-silica hydrolysis solution and the silane coupling agent hydrolysis solution are both 4 wt%, the grafting effect is better, the waste and dust emission of nano-particles are avoided, and the effect of enhancing the overall performance of the composite material is obvious, which is an optimal implementation scheme.

As can be seen from examples 1-4 in Table 1, compared with the ungrafted jute fiber reinforced composite material, the nano silica grafted jute fiber reinforced polypropylene composite material prepared by the invention has the advantages that the mechanical properties such as tensile strength, tensile modulus, bending strength and bending modulus are obviously improved. The comprehensive mechanical properties of the composite material are not only related to the reinforcing material and the matrix material, but also related to the interface property between the reinforcing material and the matrix material. According to the invention, the nanometer silicon dioxide is hydrolyzed and then grafted on the fibril of the plant fiber through the silane coupling agent, so that the polarity of the surface of the plant fiber is reduced, and the interfacial adhesion between the plant fiber and the base material is greatly improved; compared with other modification methods, the nano-silica graft modification can reduce the reduction degree of the impact strength of the fibrilia-reinforced composite material. In addition, a large number of unsaturated residual bonds exist on the surface of the nano silicon dioxide, the residual bonds have high reactivity, and can form strong binding force with polypropylene resin, so that the interface compatibility between fibers and the resin is improved to a greater extent, and the comprehensive mechanical property of the composite material is obviously improved.

In conclusion, the method improves the interface compatibility between the plant fiber and the polypropylene matrix, the prepared rigid nanoparticle grafted plant fiber reinforced polypropylene composite material has excellent overall performance, and the mechanical properties such as tensile property, bending property and the like are obviously improved; the impact toughness is also improved compared with other composite materials; moreover, renewable plant resources are fully utilized, and the prepared composite material has the characteristics of degradability and environmental friendliness; meanwhile, the composite material has low cost, rich raw material sources and simple process, and is beneficial to large-scale production.

While the present invention has been particularly shown and described with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.