Polyformaldehyde-based composite material and preparation method thereof

Abstract

The invention discloses a polyformaldehyde-based composite material and a preparation method thereof. The polyformaldehyde-based composite material consists of the following components in percentage by mass: 70-90% of polyformaldehyde; 2-10% of silicone master batch; and 5-20% of polytetrafluoroethylene. According to the invention, the silicone master batch is added as a compatilizer between the polymer matrix and the polytetrafluoroethylene filler, so that uniform dispersion and relatively strong interface adhesion of the filler are realized; according to the prepared polyformaldehyde-based composite material, the tensile strength and the impact strength are obviously improved, and the antifriction property and the wear resistance are also obviously improved; the lubricant can be used for lubrication-free dry friction, and has a wide application prospect in the industries of automobiles, household appliances and the like.

Description

Technical Field

[0001] The invention relates to the technical field of self-lubricating materials, and in particular to a polyoxymethylene-based composite material and a preparation method thereof. Background Art

[0002] Polyoxymethylene (POM) is a high-performance engineering plastic known for its excellent mechanical properties, chemical resistance and low friction coefficient. Polytetrafluoroethylene (PTFE) powder is recognized as an excellent solid lubricant in polymer composites due to its unique properties. However, when PTFE powder is added to POM materials as a filler, the mechanical properties and wear resistance of the polymer composites are often affected due to the weak interaction between the POM matrix and the filler and the agglomeration of particles. Summary of the invention

[0003] The purpose of the present invention is to provide a polyoxymethylene-based composite material and a preparation method thereof in view of the deficiencies in the prior art.

[0004] To achieve the above object, the technical solution adopted by the present invention is:

[0005] The first aspect is to provide a polyoxymethylene-based composite material, which is composed of the following components in percentage by mass:

[0006] Polyoxymethylene 70-90%;

[0007] Silicone masterbatch 2-10%;

[0008] Polytetrafluoroethylene 5-20%.

[0009] Furthermore, the polyoxymethylene-based composite material is composed of the following components in percentage by mass:

[0010] Polyoxymethylene 70-80%;

[0011] Silicone masterbatch 5-10%;

[0012] Polytetrafluoroethylene 10-20%.

[0013] Furthermore, the polyoxymethylene-based composite material is composed of the following components in percentage by mass:

[0014] Polyoxymethylene 75%;

[0015] Silicone masterbatch 5%;

[0016] Polytetrafluoroethylene 20%.

[0017] Furthermore, the polytetrafluoroethylene is used as a solid lubricant, and the average particle size of its raw material powder is 10-15 microns.

[0018] Furthermore, the silicone masterbatch contains 30-50 wt % of ultra-high molecular weight siloxane polymer.

[0019] The second aspect is to provide a method for preparing the above-mentioned polyoxymethylene-based composite material, comprising the following steps:

[0020] Step 1, weighing polyoxymethylene, silicone masterbatch, and polytetrafluoroethylene raw materials according to proportion, mixing them evenly, and drying them in a vacuum oven to obtain a premix;

[0021] Step 2: adding 0.1-0.3 wt% of antioxidant to the premix, and performing twin-screw melt blending and extrusion granulation.

[0022] Furthermore, the drying temperature is 80-85° C. and the drying time is 4-8 hours.

[0023] The present invention adopts the above technical solution, which has at least the following technical effects compared with the prior art:

[0024] The present invention achieves uniform dispersion of the filler and strong interface adhesion by adding silicone masterbatch as a compatibilizer between the polymer matrix and the polytetrafluoroethylene filler; the prepared polyoxymethylene-based composite material has significantly improved tensile strength and impact strength, and also significantly improved friction reduction and wear resistance; it can be used for dry friction without lubrication, and has broad application prospects in the automotive, home appliance and other industries. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 These are the test results of the coefficient of friction (COF, A) and the average coefficient of friction (Average COF, B) of the POM / silicone masterbatch composite material in Example 1.

[0026] Figure 2 SEM images of the fracture surfaces of POM / S5 (A) and POM / S5 / P20 (B) composite materials.

[0027] Figure 3 To verify the test results of the tensile strength (Tensile properties, A) and impact strength (Impact properties, B) of the composite material in the example.

[0028] Figure 4 These are the test results of the average friction coefficient (Average COF, A) and wear rate (Wear rate, B) of the composite material in the verification example.

[0029] Figure 5 To verify the wear surface conditions of pure POM (A), POM / P20 (B), and POM / S5 / P20 (C) materials after friction testing. DETAILED DESCRIPTION

[0030] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments, but is not intended to be limiting of the present invention. It should be noted that the embodiments and features in the embodiments of the present invention may be combined with each other without conflict.

[0031] Example 1

[0032] 1wt% (POM / S1), 3wt% (POM / S3) and 5wt% (POM / S5) silicone masterbatch were added to the polyoxymethylene (POM) polymer, and the mixture was melt-blended and extruded into granules by twin-screw extrusion. Figure 1 ), 5wt% of silicone masterbatch was selected as the optimal addition amount.

[0033] As a preferred example, the silicone masterbatch contains 30-50 wt % of ultra-high molecular weight siloxane polymer.

[0034] Among them, the mechanism of action of silicone masterbatch is:

[0035] Due to its non-polarity and low surface energy, silicone masterbatch tends to migrate to the plastic surface during the melting process after being added to the plastic. However, due to its large molecular weight, it cannot completely migrate out, forming a dynamic lubrication layer between the plastic surface and the screw. As the processing proceeds, the lubrication layer is continuously removed and generated, so that the fluidity, mold filling, demolding and processing properties of the resin are continuously improved, thereby reducing the current and equipment torque and increasing the output. After the silicone masterbatch is processed by the twin-screw extruder, it is evenly distributed in the plastic and forms micron-sized oily particles ( Figure 2 ), these oily particles make the product have better appearance, good feel, lower friction coefficient, better wear resistance and scratch resistance.

[0036] Example 2

[0037] This embodiment provides a polyoxymethylene-based composite material, which is composed of the following components in percentage by mass: 85% polyoxymethylene, 5% silicone masterbatch, and 10% polytetrafluoroethylene.

[0038] The above-mentioned polyoxymethylene-based composite material is prepared by the following method: polyoxymethylene, silicone masterbatch, and polytetrafluoroethylene raw materials are weighed in proportion, mixed, and dried in a vacuum oven (80°C, 4 hours) to obtain a premix; 0.2wt% of an antioxidant is added to the premix, and twin-screw melt blending extrusion granulation (POM / S5 / P10) is performed.

[0039] Example 3

[0040] This embodiment provides a polyoxymethylene-based composite material, which is composed of the following components in percentage by mass: 75% polyoxymethylene, 5% silicone masterbatch, and 20% polytetrafluoroethylene.

[0041] The above-mentioned polyoxymethylene-based composite material is prepared by the following method: polyoxymethylene, silicone masterbatch, and polytetrafluoroethylene raw materials are weighed in proportion, mixed, and dried in a vacuum oven (80°C, 4 hours) to obtain a premix; 0.2wt% of an antioxidant is added to the premix, and twin-screw melt blending extrusion granulation (POM / S5 / P20) is performed.

[0042] Comparative Example

[0043] The polyoxymethylene-based composite material was prepared using the raw material composition shown in Table 1 and the preparation method of Example 1.

[0044] Table 1

[0045] Polyoxymethylene Polytetrafluoroethylene powder Silicone Masterbatch POM / P10 90wt% 10wt% - POM / P20 80wt% 20wt% -

[0046] Verification Example

[0047] 1. The tensile strength (measured by a universal testing machine according to GB / T1040 standard, the testing machine is equipped with a 20kN load sensor, and the displacement control of 10mm / min is maintained during all tests) and impact strength (measured according to GB / T1843) of the polyoxymethylene-based composite materials prepared in Examples 1-2 and Comparative Examples were tested. To ensure the repeatability of the results, five samples were used in each group, and the average value was calculated. The results are shown in FIG. Figure 3 As shown: Compared with pure POM, the tensile strength and impact strength of the composites are improved, especially in POM / S5 / P20.

[0048] 2. The tribological properties of the polyoxymethylene-based composite materials prepared in Examples 1-2 and Comparative Examples were tested. The friction contact surface was 100Cr6 steel ball with a diameter of 6 mm. Dry friction was performed. The applied load was 10 N. The sliding speed was 25 mm / s. The test time was 2 hours. The results are shown in Table 1. Figure 4 and Figure 5 :

[0049] 1) The friction coefficient and wear rate of POM / S5 / P20 composite materials were reduced by 78.3% and 70.3% respectively compared with pure POM material;

[0050] 2) Figure 5 The worn surface images in Figure 2 also show the wear mechanism after the friction test. Figure 5 In a, pure POM mainly suffers from severe surface deformation and abrasive wear, while in Figure 5 In b, with the addition of 20wt% PTFE, the corrugated deformation is weakened; Figure 5In c (POM / S5 / P20), there is no sign of wear due to low friction and high surface wear resistance. This excellent tribological behavior of the POM / S5 / P20 composite is attributed to the synergistic effect of PTFE and silicone masterbatch, which leads to mechanical and tribological improvements due to uniform filler dispersion and strong matrix-filler interaction as well as a uniform tribofilm. Since the polymer surface has the lowest coefficient of friction (COF) and self-lubricating properties, there is no damage to the surface of the steel counterpart and no signs of wear when it slides against POM / S5 / P20.

[0051] The above description is only a preferred embodiment of the present invention, and does not limit the implementation mode and protection scope of the present invention. For those skilled in the art, it should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the contents of the specification and illustrations of the present invention should be included in the protection scope of the present invention.

Claims

1. A polyoxymethylene-based composite material, characterized in that: It is composed of the following components in percentage by mass: Polyoxymethylene 70-90%; Silicone masterbatch 2-10%; Polytetrafluoroethylene 5-20%.

2. The polyoxymethylene-based composite material according to claim 1, characterized in that: The polyoxymethylene-based composite material is composed of the following components in percentage by mass: Polyoxymethylene 70-80%; Silicone masterbatch 5-10%; Polytetrafluoroethylene 10-20%.

3. The polyoxymethylene-based composite material according to claim 2, characterized in that: The polyoxymethylene-based composite material is composed of the following components in percentage by mass: Polyoxymethylene 75%; Silicone masterbatch 5%; Polytetrafluoroethylene 20%.

4. The polyoxymethylene-based composite material according to claim 1, characterized in that: The polytetrafluoroethylene is used as a solid lubricant, and the average particle size of its raw material powder is 10-15 microns.

5. The polyoxymethylene-based composite material according to claim 1, characterized in that: The silicone masterbatch contains 30-50 wt % of ultra-high molecular weight siloxane polymer.

6. The method for preparing the polyoxymethylene-based composite material according to any one of claims 1 to 5, characterized in that: The steps include: Step 1, weighing polyoxymethylene, silicone masterbatch, and polytetrafluoroethylene raw materials according to proportion, mixing them evenly, and drying them in a vacuum oven to obtain a premix; Step 2: adding 0.1-0.3 wt% of antioxidant to the premix, and performing twin-screw melt blending and extrusion granulation.

7. The preparation method according to claim 6, characterized in that: The drying temperature is 80-85° C. and the drying time is 4-8 hours.

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