阅读说明：本技术 酯化改性植物纤维/abs复合材料的制备工艺 (Preparation process of esterification modified plant fiber/ABS composite material ) 是由 李大纲 朱钦睿 于 2019-09-17 设计创作，主要内容包括：本发明涉及的是一种酯化改性植物纤维/ABS复合材料的制备工艺,包括以下步骤：(a)纸浆纤维碱处理；(b)特戊酰氯改性反应；(c)纤维与ABS原料预混合及研磨解纤；(d)双螺杆熔融共挤出复合；(e)注塑成型制备复合材料。其中碱处理用来除去纤维素以外的杂质并润胀纤维以便后续改性反应,而特戊酰氯改性反应包含了纤维素纤维表面羟基的氧化和叔丁基的接枝,在此木塑材料复合过程中加入少量聚丙烯酰胺从而形成互联增强结构。该方法的优点：1)原料来源广泛,成本可控；2)改性反应低污染且试剂可回收；3)增强材料,自然条件可降解；4)工艺普适性优良,可连续化生产。(The invention relates to a preparation process of an esterified modified plant fiber/ABS composite material, which comprises the following steps: (a) alkali treatment of paper pulp fibers; (b) pivaloyl chloride modification reaction; (c) premixing fibers and ABS raw materials, and grinding and defibering; (d) melting, co-extruding and compounding the double screws; (e) and (4) injection molding to prepare the composite material. Wherein the alkali treatment is used for removing impurities except cellulose and swelling the fibers so as to facilitate the subsequent modification reaction, the pivaloyl chloride modification reaction comprises the oxidation of hydroxyl groups on the surface of the cellulose fibers and the grafting of tert-butyl groups, and a small amount of polyacrylamide is added in the process of compounding the wood-plastic material so as to form an interconnected reinforced structure. The method has the advantages that: 1) the raw materials are wide in source and controllable in cost; 2) the modification reaction has low pollution and the reagent can be recycled; 3) the reinforced material can be degraded under natural conditions; 4) the process has excellent universality and can be used for continuous production.)

1. A preparation process of an esterification modified plant fiber/ABS composite material comprises the steps of treating fibers with sodium hydroxide alkali, carrying out a pivaloyl chloride modification reaction, carrying out ternary combination on the esterification modified fibers, the ABS and a stabilizer, and carrying out injection molding to process a prefabricated member, thereby finally obtaining the wood-plastic composite material.

2. The process according to claim 1, wherein the alkali treatment comprises soaking the plant fiber suspension in a sodium hydroxide solution having a mass fraction of 16% or less at a constant temperature of less than 40 ℃ and stirring the plant fiber suspension for 1 to 1.5 hours.

3. The preparation process of claim 1, wherein the esterification modification reaction is carried out by selecting a reagent with tert-butyl structure in the molecule of pivaloyl chloride or pivalic acid, heterogeneously grafting and modifying the plant fiber in polar solvent such as NMP or dichloromethane under the catalysis of anhydrous pyridine, sulfuric acid or nitric acid at 80 ℃ or lower, and oxidizing partial hydroxyl of the fiber to obtain the esterified and modified plant fiber.

4. The process of claim 1, wherein the ternary combination of the esterified modified fiber, the ABS and the stabilizer is performed in the sequence of premixing, defibering by a three-roll grinder or a screw shearing device, and finally co-extruding, melting and blending by twin screws. The ABS is not particularly limited in trade mark, and preferably is of a type with good impact toughness, such as HI-100, HI-100H, HI-121 or HI-150 of LG company, and the stabilizer is selected from polyacrylamide, polymethyl methacrylate, polyethylene oxide, polybutylene terephthalate and other polymers with slightly high softening points and good molecular chain flexibility.

5. The preparation method of claim 1, wherein the temperature of the cylinder for injection molding is 10-15 ℃ higher than the melt processing temperature of the twin screw, the temperature setting of the mold of the micro injection molding machine is 15-20 ℃ higher than that of a pure sample, and the pressure holding time is preferably 10-15 seconds according to the filling amount of the plant fiber in the composite material.

6. The plant fiber esterification modification according to claim 3, wherein the mass ratio of pivaloyl chloride to fiber is 1: 1.6, the reaction is catalyzed by excess anhydrous pyridine and stirred in NMP solvent system for 10 hours, and the temperature is maintained at 70-80 ℃.

7. According to the process, the compound proportion is selected according to 45-50 parts of esterified modified fiber, 50-55 parts of ABS powder and 2-5 parts of stabilizing additive.

Technical Field

The invention relates to an esterification modified needle leaf pulp fiber/ABS composite material and a preparation method thereof, belonging to the technical field of composite materials.

Background

The wood-plastic composite material is a material which is formed by compounding natural plant resource extracts with thermosetting or thermoplastic resin. The processing technology has wide applicability, controllable production cost, environmental protection and degradability, and can partially replace the traditional petroleum-based plastic to be applied to the fields of building materials, traffic, decoration and packaging. The ABS engineering plastic has good mechanical property and chemical stability, wherein the polystyrene component and the polybutadiene component provide rigidity and impact toughness for the material, and endow the ABS as a structural material with supporting and protecting capacity. The plant fiber is derived from wood, herbaceous plants and gramineous plants, is rich in cellulose, hemicellulose, lignin, a small amount of pectin, xylose and other components, and has high length-diameter ratio and crystallinity so that the material has high tensile modulus and high tensile strength. In addition, compared with the artificial fiber, the natural fiber has low density, low cost and good regeneration degradability, and the composite of the natural fiber and the ABS thermoplastic resin not only makes up for the deficiency of chemical corrosion resistance of the plant fiber, but also improves the biodegradation capacity and the dimensional stability of the material, and conforms to the low-carbon, environment-friendly and high-quality production concept.

The plant fiber is divided into bast fiber, leaf fiber, seed fiber, fruit fiber, root fiber, wood fiber and the like, while the needle leaf pulp fiber belongs to wood fiber and has high cellulose content and less impurity content, and is a good composite material reinforcing component as a raw material for paper industry with less production and processing by-products. Cellulose fibers in the composite material can be purified by simple physical dissolution, and the surface performance of the fibers is optimized by physical modification methods such as heat treatment, electrostatic treatment, ray irradiation, steam explosion and the like or chemical modification processes such as alkali treatment, chemical coupling, acetylation treatment, cyanoethylation treatment and the like, so that the composite interface bonding of the fibers and resin is enhanced, and the mechanical performance of the composite material is improved.

ABS is an engineering plastic prepared by the block copolymerization of acrylonitrile, styrene and butadiene. Butadiene component and styrene monomer are properly added in the ABS synthesis process aiming at the improvement of the impact resistance or the improvement of the mechanical strength of the material, and the butadiene component and the styrene monomer are defined as the acrylonitrile/styrene copolymer toughened by the polybutadiene rubber phase according to the proportion and the interaction relation of three-phase components in the ABS. The ternary molecular chain structure shows that the benzene ring unit in the styrene increases the rigidity of the material and limits the motion of the chain segment, the chemical resistance provided by the cyano group in the acrylonitrile also brings weak polarity to the ABS, and the conjugated double bond generated after the butadiene is polymerized increases the flexibility of the molecular chain, thereby obtaining the effects of transferring internal stress load and toughening. Because of the weak polarity characteristic of ABS resin, the developed ABS-based composite material mainly selects the same weak polarity of polycarbonate, polyethylene terephthalate or polyvinyl chloride and other blending phases, and the reinforced and toughened composite material is prepared by filling ABS with nonpolar carbon fibers or glass fibers. From ABS thermoplastic characteristics, the processing of ABS-based composite materials is generally applicable to double-screw melt co-extrusion compounding, and then products with fixed shapes are obtained through injection molding.

It is worth noting that the preparation of the plant fiber/ABS composite material is different from the traditional artificial fiber composite process, the surface of the plant fiber is distributed with strong hygroscopic hydroxyl, single fibers are clustered into fiber bundles through hydrogen bonds formed by the hydroxyl, and the hydrophilic characteristic of the surface of the fiber bundles causes a layered state incompatible with the hydrophobic surface of the ABS. The prepared composite material with good fiber dispersion and complete resin coating has great significance for improving mechanical properties, and Suzuki and the like compare the influences of the ball milling method and the double-screw shearing method on plant fiber microfibrillation, fiber dispersion and the mechanical properties of the composite material. Although the ball milling method can ensure uniform microfibrillation with the dimension less than 100 nanometers, the tensile modulus and the strength of the 30% plant fiber filled polypropylene composite material prepared by adopting the twin-screw process microfibrillation are respectively as high as 5.3GPa and 85MPa, which are obviously higher than the 4.1GPa modulus and the 59.6MPa strength of the composite material prepared by the same proportion and treated by the ball milling method. The good dispersion in the process of compounding the plant fiber is obvious in improvement of the mechanical property of the material, and further research on the modification of the plant fiber and the interface bonding with the resin can become an effective way for reinforcing and toughening the composite material. (see Katsuhito Suzuki, Yoko Homma, Yuko Igarashi, et al. Effect of preparation Process of micro fibrous-reinforced Polypropylene dispersion and mechanical properties [ J ]. Cellulose, Springer, 2017.)

Disclosure of Invention

Compared with the prior art that the plant fiber is modified by adopting an organosilane infiltration or chemical vapor deposition method, the pivaloyl chloride esterification modified plant fiber with a tert-butyl structure is carried out in a fixed reaction device, the reaction temperature is moderate, the reaction process is controllable, the chemical grafting modification degree of the fiber is changed along with the increase and decrease of the addition amount of acyl chloride and the content of a catalyst, the modified plant fiber has better heat resistance because part of hydroxyl is oxidized or substituted by ester bonds, the modified plant fiber can effectively slow down the self degradation in the fusion compounding process with ABS, meanwhile, the reduction of the hygroscopicity of the fiber also enhances the coating capability of the low-polarity ABS resin, and the apparent performance of the composite material is obviously improved by properly adding some stabilizing agents and bulking agents. In order to increase the internal dispersibility of the plant fiber in the ABS, the two components are premixed and sheared and defibered by a three-roll grinder before melt coextrusion compounding, and finally the mechanical strength of a sample obtained by injection molding is obviously improved.

The invention provides a preparation method of an esterification modified plant fiber/ABS composite material, and the composite material has excellent mechanical properties.

The invention firstly carries out the modification of the plant fiber, and the method comprises the steps of dissolving the raw material plant fiber by a sodium hydroxide solution and carrying out pivaloyl chloride heterogeneous reaction. Specifically, the method comprises the steps of 1) preparing a sodium hydroxide solution with the mass percentage of 10-16%; 2) adding 2% of plant fiber suspension into sodium hydroxide solution, stirring for 1-1.5 hours at 40 ℃, then carrying out suction filtration on water in the dry suspension, washing the fiber for 1 time by using distilled water, and drying at 60-80 ℃; 3) adding 100-120 g of NMP solvent into the alkali-treated fiber, stirring at about 100 ℃ for a moment to remove residual moisture, then adding 20-30 g of NMP until the solvent immerses the fiber, adding a proper amount of pyridine as a catalyst at 80 ℃ while stirring, then adding pivaloyl chloride as required to start modification, after the reaction is finished, performing suction filtration to obtain the fiber, washing to remove the residual solvent, and drying at 60-80 ℃ to obtain the modified plant fiber.

The invention prepares an esterification modified plant fiber/ABS composite material, which is prepared by firstly defibering and premixing natural fiber with surface modified and ABS through a three-roll grinder, then carrying out melt co-extrusion compounding through a double-screw extruder, and finally carrying out injection molding to obtain a sample. The preparation raw materials of the esterified modified plant fiber/ABS composite material comprise native needle leaf sulfate pulp fiber, pivaloyl chloride modifier, ABS resin and stabilizing additive.

The esterified modified pulp fiber, the ABS resin and the stabilizer are as follows according to mass fraction:

50 parts of esterified modified pulp fiber, 50 parts of ABS resin and 5 parts of stabilizer.

The raw needle-leaved pulp fiber is provided by the light textile industry and is also used as a textile raw material of daily necessities. The raw material is obtained in the form of dry pulp fiberboard with a moisture content of less than 5%, wherein the cellulose content is about 60-70%, the hemicellulose content is about 20-30%, and the content of lignin, pectin, starch, etc. is less than 10%.

The ABS resin is from LG chemical company, has the brand number of HI-100 and the melt index of 11g/10min at 220 ℃, and is subjected to a tensile test at 23 ℃ at a speed of 50mm/min under the standard of ASTM D638, the tensile strength at the yield point is 37MPa, and the tensile modulus is 1560 MPa. The ABS grade has good impact toughness, and the brittleness influence caused by the increase of rigidity can be weakened after the plant fiber is filled.

The stabilizer needs to stabilize a system in the processing and compounding process of the fiber and the ABS resin, and prevents the material performance deterioration caused by large-scale degradation of the fiber. In addition, the stabilizer can also promote resin to better coat the fiber to play a role in compatibilization, and a general molecular chain has related groups of nitrogen and oxygen elements to form a hydrogen bond acceptor or has active hydrogen atoms to become an auxiliary agent of the hydrogen bond donor, so that cyano groups in an ABS chain segment and hydroxyl groups in the fiber can be bridged. According to the invention, polyacrylamide is preferably used as a stabilizer, the apparent performance of a polyacrylamide sample added by 2-5% in the formula is greatly improved, the surface roughness caused by the peeling of the original fiber on the surface of the material is flat and smooth, and the thermochromism phenomenon of the plant fiber and the ABS is relieved by adding the stabilizer. Besides polyacrylamide, polymethyl methacrylate, polyethylene oxide, maleic anhydride grafted polystyrene and a series of cationic polymers can also be used as a stabilizing compatibilizer for modified plant fiber/ABS composite materials. One or more of the components are selected to be added in combination, so that the processing performance and the surface performance of the composite material can be optimized.

the more preferable technical scheme of the method is that the paper pulp fiber raw material is placed in a sodium hydroxide solution with the mass fraction of 16% and stirred and dissolved for 1 hour at 40 ℃, and pivaloyl chloride is added for reaction for 10 hours to prepare the esterified modified plant fiber. Premixing 50 parts of modified plant fiber, 50 parts of ABS and 5 parts of polyacrylamide according to the proportion, preparing a fine particle fiber/ABS resin mixture by calendering and defibrinating through a three-roll grinder, and finally carrying out melt blending and injection molding on a sample through a double-screw extruder.

The composite material can be widely applied to the fields of traffic, building materials, packaging and the like, and compared with pure ABS, the mechanical property of the plant fiber composite ABS material is improved, and meanwhile, the composite material has good environmental protection value, and the degradability of the composite material reduces the recovery pressure of ABS. In addition, the continuous production is ensured by adopting a double-screw co-extrusion device to develop the composite process of the plant fiber and the ABS, the production cost is effectively reduced by using the plant fiber with wide source, and the biomass ABS material with high added value is prepared by the method.

The invention has the beneficial effects that:

The invention provides a preparation method of an esterification modified plant fiber/ABS composite material, which comprises the steps of sequentially carrying out micro-nano defibration and composite fiber and resin by a three-roll grinder and a double-screw extruder, and then forming a sample by an injection molding machine. The modified plant fiber is prepared by firstly carrying out alkali dissolution treatment on raw material fibers to remove amorphous hemicellulose and other impurities, and the cellulose fibers absorb alkali liquor to swell so as to weaken the action of hydrogen bonds among the cellulose fibers and increase the surface area, so that the modification reaction is conveniently and efficiently carried out. And then the fibers are further dispersed in a solvent NMP system, pivaloyl chloride and cellulose are subjected to esterification reaction to enable tert-butyl to replace partial hydroxyl to form cellulose ester, in addition, partial hydroxyl on the surface of the cellulose is subjected to autocatalysis to form carbonyl, the hygroscopicity of the modified plant fibers is reduced, and the polarity of the alkyl group on the graft is similar to that of the ABS main chain component, so that the compatibility of a two-phase composite interface is improved, and the mechanical property of the composite material is enhanced. The applicant of the application finds that a small amount of polyacrylamide is additionally added as a stabilizer to 'lubricate' the interface between the fiber and the ABS, so that the prepared sample has better surface uniformity and better forming effect.

Drawings

The attached drawing is a schematic diagram of the interaction of hydrogen bonds in the compounding process of modified cellulose, ABS and polyacrylamide.

Detailed Description

The technical solutions of the present invention will be described in further detail with reference to specific examples, which are intended to make the present invention more comprehensible and recognizable to those skilled in the art.

Example 1

Cutting paper pulp fiberboard, weighing 6.010g (about 6g), adding into food processor, stirring and breaking into floccules, wherein the stirring is divided into 3 times, 15-20 seconds each time and 5-8 seconds at intervals, to prevent the fibers from being damaged by overheating of motor. 300 ml of distilled water was measured, and the dispersed fibers were immersed in the distilled water with tweezers to prepare a fiber suspension having a mass fraction of 2%. 8.012g (about 8g) of sodium hydroxide pellets are then weighed into 42 ml of distilled water to prepare a sodium hydroxide solution with a mass fraction of 16%, and the lye is slowly poured into the fiber suspension while maintaining magnetic stirring and controlling the temperature at 40 ℃. Stirring for 1 hour, stopping stirring, cooling at normal temperature for a moment, slowly pouring the suspension into a filter funnel filled with two layers of qualitative filter paper, draining by a glass rod, after all water is filtered out, clamping the fibers by tweezers and placing in a beaker, adding a proper amount of distilled water until the fibers are completely soaked, stirring and washing by the glass rod, then pouring the fiber leacheate into the filter for suction filtration again, collecting the fibers, and drying in an oven at 60 ℃.

Example 1'

6g of the dried fiber, 5.430g (about 5.4g) of ABS powder and 0.604g (about 0.6g) of polyacrylamide are weighed to ensure that the three components are about 1: 0.1, and then the dried fiber, ABS powder and polyacrylamide are poured into a food processor together to be dry-mixed for 3 times and stirred for 10 to 15 seconds each time. The premixed raw materials are clamped by tweezers in batches and sheared and defibered by a three-roll grinder (Changzhou English Intelligent mechanical Co., Ltd.), and the ground materials are collected and repeatedly ground for 2 to 3 times until the mixture becomes fine flake particles. Then putting the completely ground material into a Haake MiniLab (thermoelectricity company, USA) twin-screw co-extrusion compounding, controlling the temperature at 170 ℃ and the screw rotating speed at 35r/min, clamping the extruded composite sample strip into a charging barrel of a micro injection molding machine (WZS10D Shanghai precision machinery Co., Ltd.), setting the temperature of the charging barrel at 185 ℃ and the temperature of a die at 110 ℃, keeping the pressure for 15 seconds, and finally taking out the dumbbell type sample from the die.

Example 2

the alkaline treatment was carried out in a similar manner to example 1, except that 6.018g of pulp fiber board was cut out and weighed out, and the pulp fiber board was broken into flocculent fibers by stirring sufficiently with a food processor, and a fiber suspension having a mass fraction of 2% was prepared by adding 300 ml of distilled water. 8.006g of sodium hydroxide granules are weighed and added with 42 ml of distilled water for dissolving to prepare a sodium hydroxide solution with the mass fraction of 16%, the alkali liquor is slowly poured into the mixture while the fiber suspension is magnetically stirred, the mixture is kept at 40 ℃ for 1 hour, then the stirring is stopped, the fiber is obtained by suction filtration, the fiber is washed by the distilled water once, and the washing liquid is continuously removed by suction filtration. After the alkali treatment is finished, 100g of NMP solvent is weighed and added into the fiber, the temperature is raised to 100 ℃ while stirring, after the residual crystal water in the system is removed, 20g of NMP is added, the temperature is lowered to 80 ℃ and stirring is continued, 10.451g of pyridine is weighed and added, after stirring fully for 25 minutes, 3.8 ml of pivaloyl chloride is weighed and added into the reaction system dropwise and uniformly. And stopping the reaction after 10 hours, carrying out suction filtration on the fiber suspension to remove the solvent, washing the fiber once with glacial acetic acid, washing twice with distilled water after suction filtration, continuously carrying out suction filtration and drying, and then putting the fiber into a 60 ℃ oven.

Example 2'

Weighing 7.965g of dried esterified modified fibers, 7.169g of ABS powder and 0.797g of polyacrylamide, fully mixing in a food processor, grinding and defibrating for many times by a three-roll grinder, adding the flake raw materials into a double-screw extruder for melting and compounding, controlling the temperature of a screw at 170 ℃ and the rotating speed of the screw at 35r/min, finally setting the temperature of a plastic injection cylinder at 185 ℃, controlling the temperature of a mould at 100 ℃ and maintaining the pressure for 15 seconds for molding to obtain a tensile test sample strip.

Example 3

Cutting a paper pulp fiberboard, measuring 6.085g of fiber raw material, putting the fiber raw material into a food processor, stirring for 3 times to form fiber floccule, clamping the fiber by using forceps, putting the fiber into 300 ml of distilled water, and stirring to prepare a fiber suspension. 8.028g of sodium hydroxide granules were weighed in addition to 42 ml of distilled water to prepare a 16% strength by weight sodium hydroxide solution, the lye prepared in situ was slowly added to the fibre suspension, the temperature was controlled at 40 ℃ and stirring was carried out. After 1 hour, stopping stirring until the fibers are completely dispersed, performing suction filtration to remove alkali liquor, washing with distilled water once, dispersing and spreading the washed fibers on a woven fabric, and placing on a silica gel tray at normal temperature for drying. Measuring 136g of NMP solvent at one time, adding the NMP solvent to the immersed alkali-treated fiber, keeping the temperature at 100 ℃ for 1-2 minutes to remove residual water, maintaining the temperature at 80 ℃, adding 5.24g of pyridine (only used as a reaction catalyst) in the stirring process, measuring 5.74 ml of pivaloyl chloride after the system is fully mixed, dropwise adding the pivaloyl chloride into a reaction device, continuously stirring for 20 hours, stopping, pouring out the fiber suspension, standing, cooling for a moment, performing suction filtration, washing the fiber once with absolute ethyl alcohol, washing twice with deionized water to remove residual reaction reagents, collecting the esterified modified fiber, and drying in a 60 ℃ oven.

Example 3'

5.692g of esterified modified fiber is weighed, 5.35g of ABS and 0.342g of polyacrylamide are obtained according to the mixing ratio of the fiber, the ABS and the polyacrylamide of 1: 0.1, three components are fully mixed in a food processor and are ground and defibrated in batches by a three-roll grinder, the modified fiber/ABS powder mixture after being ground for many times is melted and extruded by a double screw in the same direction at 170 ℃ and 35r/min, a sample strip is put into a 185 ℃ charging barrel after being extruded, injection molding is carried out at the temperature of a 110 ℃ mold, and the pressure is maintained for 15 seconds, so that the modified fiber composite ABS tensile product is processed.

Comparative examples 1, 2 and 3 differ in that example 1 only had the base treatment of the raw fiber, whereas examples 2 and 3 had the pivaloyl chloride esterification modification of the fiber after the base treatment. In the esterification modification process, sufficient pyridine catalyst is added in the example 2, the mass ratio of the pivaloyl chloride to the fiber is close to 1: 1.6, and the reaction time is 10 hours; however, in example 3, a catalyst was added in a molar ratio of pivaloyl chloride to pyridine of 1: 5, and pivaloyl chloride modifier was added in a mass ratio of acid chloride to fiber of 1: 1 and reacted for 20 hours. Comparative examples 2 and 3 mainly investigate the effect of increasing the amount of catalyst and modifier and prolonging the reaction time on the modification effect, and the difference between the two modification processes compared to the single alkali treatment was further investigated with reference to example 1.

Example 1 ' 2 ' 3 ' samples prepared with plain ABS performance test results are shown in table 1.

From table 1, it can be seen that the fiber/ABS composite material prepared by the 10-hour modification process of example 2 has the highest tensile strength, which is improved by nearly 50% compared to the pure sample, while the modification effect of example 3 is not significant, and the tensile strength of the corresponding material is equivalent to that of the sample that is not modified by the alkali treatment of example 1, and is only slightly improved compared to the pure sample. In addition, the Young modulus of the composite material filled with 50% of fibers in the ABS is greatly improved, the modification effect of the example 2 is optimal, and the compatibility of the esterified modified fibers and the composite interface of the ABS is good, so that the fracture elongation of the sample keeps the characteristics of pure ABS, and the fracture elongation is higher than that of the examples 1 and 3.

TABLE 1 esterified modified pulp fiber composite ABS material Performance data

The fiber is subjected to alkali treatment, on one hand, impurities such as hemicellulose, lignin, pectin and the like in the raw materials are dissolved, and on the other hand, alkali liquor sodium hydroxide can be adsorbed by hydroxyl on the surface of cellulose to form hydrated alkali ions, so that the fiber is swelled and dispersed macroscopically. The reaction contact surface of the fiber after alkali treatment is increased, the modification effect of an esterification reagent is facilitated, the esterification of hydroxyl and the hydrolysis of an ester bond coexist in an esterification modification reaction system, part of the hydroxyl is also subjected to alkaline oxidation to form carbonyl, and finally, the hygroscopicity of the fiber is weakened through modification, and the composite interface binding power of the fiber and a hydrophobic ABS chain segment is enhanced, so that the purpose of improving the mechanical property of the composite material is achieved. Examples 1, 2, 3 modified cellulose fibers having a visible wavenumber of 1600cm after Fourier Infrared Spectroscopy^-1To 1700cm^-1The change rule of carbonyl absorption peak formed by oxidizing hydroxyl group, and 1720cm^-1Characteristic peak of weak ester bond at wavenumber. This indicates that the grafting reaction is inhibited by the oxidation of the hydroxyl group, and it is the controlled oxidation that together with a small amount of t-butyl grafting promotes the improvement of the composite interface. The peak intensity of carbonyl peak of modified fiber in example 2 is most obvious, the tensile strength of sample corresponding to example 2 ' is the highest, the peak intensity of carbonyl absorption after modification in examples 1 and 3 is only slightly higher than that of original fiber, and the tensile strength of sample corresponding to example 1 ' and example 3 ' is not obviously improved compared with pure ABS.

The method is characterized in that the modifying process of the embodiment 2 is optimized by combining the advantages and disadvantages of the mechanical properties of the modified plant fiber/ABS composite material, then the modified fiber, the ABS and the polyacrylamide are blended and molded according to the proportion of 1: 0.1, and finally the composite material is prepared by injection molding and demolding. Tests show that the esterification modification of the fiber in the reaction system comprises hydroxyl alkaline oxidation and alkyl unit grafting, the well-modified fiber is associated by the linkage action of hydrogen bonds provided by amino groups in polyacrylamide, and also cyano groups in ABS are connected with amide hydrogen bonds, polyacrylamide plays a role of 'bridges' in the compounding process to communicate ABS and cellulose fiber, and ABS and plant fiber are tightly bonded under screw kneading so as to reinforce the material.