阅读说明：本技术 一种汽车结构件用低翘曲、高尺寸稳定性的增强sma复合材料及其制备方法 (Low-warpage high-dimensional-stability reinforced SMA composite material for automobile structural member and preparation method thereof ) 是由 徐凯华 于 2019-08-14 设计创作，主要内容包括：本发明涉及了一种汽车结构件用低翘曲、高尺寸稳定性的增强SMA复合材料及其制备方法,具体由以下重量份的原料组成：SMA三元共聚树脂35～70份,玻璃纤维10～40份,增韧剂2～10份,辅助分散剂2～15份,热稳定剂1～8份；本发明的优势在于：解决了当前汽车中一些大型结构件及外覆盖件对于低收缩、低翘曲、高尺寸稳定性材料的迫切需求,通过优选特定规格的SMA材料,与增强玻纤形成适中的界面黏结状况,加上分散剂的使用,确保增强玻纤在加工及注塑成型过程中具有更为均匀的分布和分散效果；材料兼具了低收缩、低翘曲的尺寸特性,以及高抗冲、热稳定性好的性能特征,应用于天窗骨架、全塑尾门骨架、ABC柱饰板支架、副仪表板骨架、发动机舱外饰板等领域时,能有效降低部件的拼接不良率,提升装配品质,有助于车辆在使用后期的避免发生异响及其他的不良现象。(The invention relates to a reinforced SMA composite material with low warpage and high dimensional stability for an automobile structural member and a preparation method thereof, and the reinforced SMA composite material is specifically composed of the following raw materials in parts by weight: 35-70 parts of SMA (styrene-butadiene-styrene) ternary copolymer resin, 10-40 parts of glass fiber, 2-10 parts of a toughening agent, 2-15 parts of an auxiliary dispersing agent and 1-8 parts of a heat stabilizer; the invention has the advantages that: the urgent requirements of some large structural members and outer covering parts on materials with low shrinkage, low warpage and high dimensional stability in the current automobile are solved, the SMA material with a specific specification is preferably selected, a moderate interface bonding condition is formed between the SMA material and the reinforced glass fiber, and the use of a dispersing agent ensures that the reinforced glass fiber has more uniform distribution and dispersion effects in the processing and injection molding processes; the material has the size characteristics of low shrinkage and low warpage, has high impact resistance and good thermal stability, can effectively reduce the joint defective rate of components when being applied to the fields of skylight frameworks, all-plastic tail door frameworks, ABC column decorative plate supports, auxiliary instrument panel frameworks, engine compartment outer decorative plates and the like, improves the assembly quality, and is beneficial to avoiding abnormal sound and other bad phenomena of vehicles in the later use period.)

1. The reinforced SMA composite material with low warpage and high dimensional stability for the automobile structural part is characterized in that: the feed comprises the following raw materials in parts by weight:

2. The reinforced SMA composite material with low warpage and high dimensional stability for automotive structural members as claimed in claim 1, wherein: the SMA terpolymer resin has a Maleic Anhydride (MA) content of 5-25%.

3. The reinforced SMA composite material with low warpage and high dimensional stability for automotive structural members as claimed in claim 1, wherein: the glass fiber is glass fiber chopped strand mat, the monofilament diameter is 10-13 um, and the chopped length is 3-4.5 mm.

4. The reinforced SMA composite material with low warpage and high dimensional stability for automotive structural members as claimed in claim 1, wherein: the toughening agent is ethylene-butyl acrylate-glycidyl methacrylate (E/nBA/GMA) terpolymer.

5. The reinforced SMA composite material with low warpage and high dimensional stability for automotive structural members as claimed in claim 1, wherein: the auxiliary dispersing agent is one or more of needle-shaped wollastonite, high-mesh talcum powder and graphene micro-sheets.

6. The reinforced SMA composite material with low warpage and high dimensional stability for automotive structural members as claimed in claim 1, wherein: the heat stabilizer is one or more of organic compounds with specific structures, such as phosphite ester, hindered phenol and thioester, which can capture free radicals generated by the thermal degradation of polymers.

7. A method for preparing a reinforced SMA composite material with low warpage and high dimensional stability for automotive structural members as claimed in any one of claims 1 to 6, comprising the steps of:

(1) Weighing the SMA ternary resin, the toughening agent, the auxiliary dispersing agent and the heat stabilizer in parts by weight, and uniformly mixing to obtain a mixed raw material;

(2) Placing the dried mixed raw materials into a main feeding bin of a double-screw extruder which is tightly meshed and rotates in the same direction, adding the dried mixed raw materials into a machine barrel of the extruder through a feeding screw, adding glass fiber into the extruder from a side feeding port, wherein the diameter of the screw of the extruder is 36mm, the length-diameter ratio L/D is 44, and the temperature of each subarea of the main machine barrel from the feeding port to a machine head outlet is set as follows: the product is obtained after the processes of melt extrusion, cooling, granulation, drying and the like are carried out at the temperature of 100 ℃, 190 ℃, 200 ℃, 215 ℃, 220 ℃ and the rotating speed of a main engine of 200 revolutions per minute.

Technical Field

the invention belongs to the technical field of high polymer materials, and particularly relates to a reinforced SMA composite material with low warpage and high dimensional stability for an automobile structural member and a preparation method thereof.

Background

At present, the development trend of light weight and environmental protection in the automobile industry is increasingly deep, and the material selection concept and principle of replacing steel with plastic become common knowledge in the automobile industry. The automobile structural parts can be respectively used as main structural parts (such as a body frame, an ABC column, a chassis frame and the like) and secondary structural parts (such as an instrument panel framework, a central channel framework, a door inner panel framework, a tail door framework and the like) according to the degree of bearing external force, and the secondary structural parts are high-performance fiber reinforced thermoplastic plastics to replace steel, so that the earliest and most mature field of automobile lightweight research is realized.

However, the fiber reinforced thermoplastic composite material for the secondary structural member inherently has the advantages of easy processing, low cost, low density, light weight, convenient installation and the like, but one performance defect which is difficult to avoid is the dimensional problems of large and unstable material shrinkage rate, easy warping, reduced isotropy degree and the like, and parts made of the materials are often installed and connected with metal parts, so that the adverse phenomena of large installation seams, abnormal sound, deformation and the like are easily generated in the actual use process. The above-mentioned poor dimension problem is closely related to the base material selected for the fiber reinforced thermoplastic composite material, and the currently commonly used thermoplastic matrix materials such as polypropylene (PP) and Polyamide (PA) are all crystalline polymers, which have strong crystallization tendency, but low crystallization rate and incomplete crystal structure, and secondary crystallization phenomenon will occur when the materials are heated after molding, which affects the dimension performance of the materials.

The SMA resin is a copolymer of styrene and maleic anhydride, and the SMA terpolymer is formed by introducing rubber and a third component for graft copolymerization on the basis of the styrene-maleic anhydride copolymer, so that the defect of insufficient shock resistance of the traditional SMA resin is overcome. The SMA terpolymer contains a certain proportion (5-25%) of maleic anhydride, so that good interface bonding can be formed between the SMA terpolymer and a commonly used reinforcement such as glass fiber without adding an additional graft compatilizer. However, too strong interfacial adhesion adversely affects the dispersion distribution of the glass fiber, thereby affecting the dimensional effect of the material, which is a very rare field in current research. CN1803912A describes a glass fiber reinforced SMA resin for automobile instrument panel, which focuses on improving the problem of insufficient impact resistance of the material by using a preferred toughening agent, and does not relate to the improvement of the dimensional effect of the material; CN103819862A adopts upgrading of composite material processing method, and uses continuous long glass fiber to replace short glass fiber, so as to improve mechanical performance indexes such as material rigidity, impact resistance, etc. to a certain extent.

disclosure of Invention

Aiming at the disadvantages of easy crystallization and strong post-shrinkage of a polypropylene base material and the inherent easy orientation and low interphase bonding degree of long glass fiber reinforcement, the invention aims to overcome the defects of the prior art and provide a reinforced SMA composite material with low warpage and high dimensional stability for an automobile structural member.

The purpose of the invention is realized by the following technical scheme:

A low-warpage and high-dimensional stability reinforced SMA composite material for an automobile structural member comprises the following raw materials in percentage by weight:

Further, the SMA terpolymer resin has a Maleic Anhydride (MA) content of 5-25%.

Further, glass fiber be glass fiber chopped strand mat, its monofilament diameter is 10 ~ 13um, and the chopped length is 3 ~ 4.5 mm.

Further, the toughening agent is an ethylene-butyl acrylate-glycidyl methacrylate (E/nBA/GMA) terpolymer.

Furthermore, the auxiliary dispersant is one or more of needle-shaped wollastonite, high-mesh talcum powder, graphene micro-sheets and other inorganic powder.

Furthermore, the heat stabilizer is one or more of organic compounds with specific structures, such as phosphite ester, hindered phenol, thioester and the like, which can capture free radicals generated by the thermal degradation of the polymer.

A second object of the present invention is to provide a reinforced SMA composite with low warpage and high dimensional stability for automotive structural members, the method comprising the steps of:

(1) Weighing the SMA ternary resin, the toughening agent, the auxiliary dispersing agent and the heat stabilizer in parts by weight, and uniformly mixing to obtain a mixed raw material:

(2) placing the dried mixed raw materials into a main feeding bin of a double-screw extruder which is tightly meshed and rotates in the same direction, adding the dried mixed raw materials into a machine barrel of the extruder through a feeding screw, adding glass fiber into the extruder from a side feeding port, wherein the diameter of the screw of the extruder is 36mm, the length-diameter ratio L/D is 44, and the temperature of each subarea of the main machine barrel from the feeding port to a machine head outlet is set as follows: the product is obtained after the processes of melt extrusion, cooling, granulation, drying and the like are carried out at the temperature of 100 ℃, 190 ℃, 200 ℃, 215 ℃, 220 ℃ and the rotating speed of a main engine of 200 revolutions per minute.

Compared with the prior art, the invention has the following beneficial effects:

1. By selecting the SMA terpolymer with high molecular weight (more than or equal to 10 ten thousand) and specific MA content (5-25%) as matrix resin of the reinforced material, the material is an amorphous copolymer, the crystallization tendency of a molecular chain is low, and the problems of low crystallization efficiency, incomplete crystallization degree and post-shrinkage of a series of finished parts of the material caused by the low crystallization efficiency and the incomplete crystallization degree of the traditional material selection such as PP are effectively solved; and an interface layer structure with moderate bonding is formed between the SMA terpolymer and the glass fiber through the directional control of the MA content in the SMA terpolymer.

2. For the glass fiber reinforced SMA composite material, the dispersion distribution condition of the glass fibers is the most critical factor directly influencing the mechanical property and the size characteristic of the material, so the invention is originally realized by the following steps: the auxiliary dispersing agent for reinforcing the glass fibers is introduced, so that an effective mechanical shearing and mixing buffer layer can be formed between the glass fibers and the machine barrel in the melting processing process, the problems of broken fibers and low material performance caused by excessive shearing of the glass fibers are solved, the processes of opening, splitting, dipping and the like of glass fiber aggregate bundles can be assisted to a certain extent, and the dispersion distribution condition of the glass fibers in the matrix is improved.

3. Compared with a long glass fiber reinforced system, the reinforced SMA composite material with low warpage and high dimensional stability obtained by the technical scheme provided by the invention has no disadvantages in rigidity and impact resistance, the longitudinal and transverse shrinkage rate conditions under the conventional conditions (23 ℃ and 48h) are obviously better, the molding warpage of the material is reduced by at least 2/3, the linear expansion coefficient CLTE of the material under the high and low temperature environment (-30-100 ℃) is also greatly lower, and the numerical difference between the longitudinal direction and the transverse direction is smaller, so that the reinforced SMA composite material has better material isotropy, and has important significance for improving the later assembly and long-term use effect of large-scale automobile structural members.

Detailed Description

The invention is further illustrated by the following specific examples, which are intended to be illustrative only and not limiting.

The raw materials used in the embodiment of the invention are as follows:

SMA-1: SZ08250, POLYSCOPE USA, maleic anhydride content 8%.

SMA-2: M214, Shanghai institute for petrochemical engineering, maleic anhydride content 14%.

SMA-3, SMA700, Shanghai Huawen New Material Co., Ltd., maleic anhydride content 23%. .

Glass fiber: continuous glass chopped strand mat, diameter 10um, chopped length 3mm, Chongqing International composite Limited.

A toughening agent: ethylene-butyl acrylate-glycidyl methacrylate terpolymer PTW, du pont, usa.

Auxiliary dispersant-1: acicular wollastonite with the length-diameter ratio of 15:1 and the effective silicon dioxide content of 50-51 percent, Guangdong Wuling wollastonite, Inc.

Auxiliary dispersant-2: 10000 mesh talc, 60% effective silica, italian epeikob.

auxiliary dispersant-3: the graphene nanoplatelets have the thickness of 10-15nm, the diameter of a lamella (D50) of 7-10um and the carbon content of more than or equal to 97 percent, and are produced by carbon materials GmbH of Wei Li Korea in Shandong.

Weather-resistant stabilizer: polymer hindered phenol antioxidants 1330, Pasteur Germany.

and (3) product performance testing:

impact properties: the test is carried out on a simple beam impact tester according to ISO179-1 standard, the notch of a sample strip is A type, and the test is carried out at normal temperature (23 ℃).

And (3) shrinkage testing: the shrinkage data in the vertical direction (T) and the horizontal direction (/ L) were measured after the injection-molded panels had been placed in a standard environment (23 ℃, 50% RH) for 48h according to ISO 294-4.

And (3) testing warpage: and (3) performing injection molding on a sample plate with a standard size of 355 multiplied by 100 multiplied by 2.0mm, placing the sample plate for 24 hours in a standard environment (23 ℃ and 24 hours), fixing one end of the sample plate on the flat surface, and testing the height value of the other end of the sample plate on the flat surface, namely the warping degree of the material.

coefficient of linear expansion CLTE test: and (3) testing the CLTE data in a vertical direction (vertical) and a horizontal direction (/) on a TMA PT1000 according to a standard flow, wherein the temperature interval is-30-100 ℃, the heating rate is 10 ℃/min, and the CLTE data is tested respectively.

And (3) thermal aging test: according to the method shown in ISO188 standard, the standard sample plate is placed in a forced air drying oven, heated to 120 ℃, placed for 1000 hours under an aerobic condition, taken out and placed in a standard environment (23 ℃, 50% RH) for 24 hours, and the surface condition of the sample plate is observed.