Study on adhesion promoter for the hottest titaniu

Research on adhesion promoter for titanium alloy surface

titanium (4). Vanadium for aviation industry has increased steadily. Research on adhesion promoter for gold surface

April 15, 2019

Research on adhesion promoter for titanium alloy surface

Li Bin, Zhang Jianfei, Wang Jinzhong, Zhang Quanwei, Mayanqing

(Zhonghao North coating industry research and Design Institute Co., Ltd., Lanzhou 730020)

Abstract: different adhesion promoters were prepared, the adhesion of the coating on titanium alloy was tested by pulling method, the contribution of different adhesion promoters to the adhesion of the coating on titanium alloy was evaluated, and the adhesion promoter prepared with modified polyamide modified coupling agent KH-560 was screened, By studying the effects of their different mass ratios on adhesion and storage stability (gel), and the effects of solvent dosage on the storage stability of adhesion promoter, it was finally determined that the mass ratio of coupling agent to modified polyamide was 4 ∶ 1 and the solvent dosage was 60%

key words: titanium alloy; Adhesion promoter; Pull apart adhesion

0 introduction

titanium alloy is an alloy composed of adding a small amount of other elements to titanium. Titanium, as an important structural metal, was developed in the 1950s. Titanium alloy has the characteristics of strong corrosion resistance, high strength, low density and stable medium temperature performance. With the rapid development of titanium industry, its application fields are more and more extensive. The oil output of oil return pipe is large. It was used in the aviation field in the 1950s and 1960s, and is known as "air metal"; In the 1970s, it was known as "land metal"; Now it is also known as "ocean metal" Chinese coating. At present, the excellent performance of titanium and titanium alloys has been recognized by countries all over the world, and has been widely used in the field of corrosion prevention. This is because titanium alloys are more active, and the surface is easy to form a dense oxide film, which can play a role in corrosion prevention

all materials have their advantages and disadvantages. In order to expand the application range of titanium alloys, the main way to achieve is to improve the corrosion resistance, fretting wear resistance, wear resistance, high temperature oxidation resistance and other properties of titanium alloys. The surface treatment of titanium alloy has been applied to almost all methods of metal surface treatment at present, among which the traditional coating technology is efficient and easy to operate, and has been widely used. Therefore, coating technology is a very effective method to improve the oxidizability of titanium alloy, which is mainly because titanium alloy is easy to oxidize and form oxide film in air. The oxide film is not only dense, but also has low surface energy. Low surface energy is not conducive to the adhesion (adhesion) of the coating. The establishment of adhesion between coating materials and substrate mainly includes physical adhesion (van der Waals force) and chemical bond

due to the low surface energy of titanium alloy, the small contact angle between the coating material and the substrate, and the limited wetting of the coating on the substrate, the physical attachment is affected. To solve the attachment of the coating material, only functional groups that can form chemical bonds with the substrate can be introduced, and the surface energy of the contact surface with the substrate can be improved. In this paper, by preparing and comparing the contribution of different adhesion promoters to adhesion, the optimal scheme is selected, and the adhesion promoter that plays a bridge role between the surface of titanium alloy and the coating is prepared. It is not only conducive to the formation of chemical bonds between the coating and the substrate, but also conducive to improving the surface energy of the substrate, so as to realize the efficient adhesion of the coating to titanium alloy. At the same time, the adhesion promoter was further optimized to make its performance more stable and get wider application

1. Test part

1.1 test raw materials and equipment

test raw materials: γ- Aminopropyl triethoxysilane (KH-550), bis (3-triethoxysilyl) amine (kh-270) γ- Glycidyl ether oxypropyl trimethoxysilane (KH-560): industrial grade, Hangzhou Jessica Chemical Co., Ltd; Epoxy resin: industrial grade, Sanmu chemical; Bisphenol F epoxy resin: industrial grade, South Asia Chemical; Rubber modified epoxy resin, active diluent: industrial grade, jiadida new materials Co., Ltd; Polyamide resin: industrial grade, air chemical; Anhydrous ethanol, methanol, xylene and other solvents: industrial grade, Tianjin Chemical Reagent Factory; Catalyst (37% hydrochloric acid): analytically pure, Tianjin Chemical Reagent Factory; Deionized water: self made

test equipment: laboratory high-speed disperser, at-a coating adhesion puller

1.2 preparation of adhesion promoter

a: γ- Aminopropyl triethoxysilane (KH-550) hydrolysate

B； γ- Glycidyl ether oxypropyl trimethoxysilane (KH-560) hydrolysate

C； Modification of epoxy resin E-44 γ- Glycidyl ether oxypropyl trimethoxysilane (KH-550)

d: epoxy resin E-44 modified (3-triethoxysilyl) amine (kh-270)

e: amine resin modification γ- Glycidyl ether oxypropyl trimethoxysilane (KH-560)

1.3 preparation of varnish and paint film

Table 1 solvent free epoxy varnish formula

serial number

originally, only the name of sensor material was replaced

dosage/g

1

epoxy resin 1

50.0

2

epoxy resin 2

10.0

3

active diluent

10.0

4

rubber modified epoxy resin

10.0

5

polyamide

13.4

6

aliphatic amine

7.1

Prepare solvent-free varnish according to the reference formula in Table 1, and brush TC4 titanium alloy plate (50mm) with coupling agents KH-550, kh-270, KH-560 and adhesion accelerators a, B, C, D and e respectively × 100mm), dry for 30min, and then scrape the varnish with a thickness of (200 ± 10) μ m. Dry at room temperature or sprinkle stearic acid on the copper wire of the cleaning tool; After 24h, dry in an oven at 80 ℃ for 4h, and conduct the pull apart adhesion test according to the provisions of gb/t 5210-2006 "pull apart adhesion test of paints and varnishes"

2 results and discussion

2.1 effect of different adhesion promoters on adhesion

due to the low surface energy of titanium alloy, the wetting of the coating on the substrate is affected to a certain extent, which will affect the adhesion between the coating film and the substrate, which is intuitively shown as poor adhesion. There are two ways to establish the adhesion of the film: one is to fully wet with the substrate to form van der Waals force to provide adhesion in a physical way; The second is to form chemical bonds with the substrate. In order to form chemical bond bonding, there must be functional groups that are easy to form chemical bonds, such as - Oh, - sior, etc. At present, the most commonly used solution is to add silane coupling agent to the coating material system, and silane coupling agent has the characteristics of cross-border covalent bond formation, so compounds containing silane coupling agent structure can improve the adhesion between polymer and titanium alloy

the effects of coupling agents KH-550, kh-270, KH-560 and adhesion promoters a, B, C, D and E on adhesion were compared. The results are shown in Table 2

Table 2 Effects of different adhesion promoters on adhesion

adhesion promoter

blank

KH-550

kh-270

KH-560

a

b

C

d

e

adhesion/mpa

0.73

1.24

1.61

1.02

1.45

1.15

3.35

3.86

4.68

through the comparative test, it can be seen that the coupling agent has a certain contribution to improving the adhesion between the film and titanium alloy, This is because the siloxane (- sior) in the coupling agent reacts with water in the air to form silicon hydroxyl (- SiOH), which can further react with the hydroxyl on the titanium alloy substrate to form a covalent bond, so as to form a whole with the substrate in the form of chemical bond, which improves the adhesion between the polymer and the titanium alloy substrate; Adhesion promoters A and B are the compounds containing siloxane (- sior) with long molecular chain formed by partial hydrolysis of siloxane (- sior) in the coupling agent and condensation reaction, leaving part of - sior to react with water in the air. Silicon hydroxyl (- SiOH) can further react with hydroxyl on titanium alloy substrate to form covalent bond, so as to form a whole with the substrate in the form of chemical bond to improve adhesion. The previous hydrolysis with coupling agent and dual coupling agent has limited contribution to the adhesion, which is mainly because the cohesive energy of the transition film formed by them with titanium alloy substrate is low and the film is brittle in the pre-treatment process. The hydrolyzed coupling agent has a greater contribution to the adhesion than the single coupling agent. This is because the molecular branching degree of the material after hydrolysis and condensation is high and brittle, but the cohesive energy of the transition film is still small, Therefore, it has made a certain contribution to the improvement of adhesion, but it is not very prominent

adhesion promoters C, D and e contribute significantly to the adhesion, because in the process of modification, the active group in the coupling agent reacts with the active group in the flexible resin first, and retains the siloxane (- sior) in the coupling agent, which is conducive to reacting with the hydroxyl group on the titanium alloy substrate to form a covalent bond, so as to form a whole with the substrate in the form of chemical bond, The adhesion between polymer and titanium alloy substrate is improved, the brittleness of forming transition film is smaller, and the cohesion energy is larger, so the adhesion is better. The reason for the difference between adhesion promoters C and D is that because the number of siloxane (- sior) in coupling agents KH-550 and kh-270 is different, the number of siloxane (- sior) in kh-270 is twice that in KH-550, and there are more sites to form chemical bonds with titanium alloy substrate, so the contribution of D to adhesion is higher than that of C. The reason for the difference between D and E is that - Oh will be generated when the active group of the coupling agent in E reacts with the active group of the flexible resin, and the amine resin is alkaline. Under alkaline conditions - Oh is easier to react with a part of siloxane (- sior) in the coupling agent, which is also conducive to the polycondensation reaction, promotes the improvement of the cohesive energy of the modified resin, and retains a part of siloxane (- sior), It is beneficial to react with hydroxyl groups on titanium alloy substrates to form covalent bonds, so the contribution of e to adhesion is higher than that of D

2.2 influence of amine resin on the performance of adhesion promoter

through test screening, it is found that amine resin modified silane coupling agent KH-560 contributes the most to the adhesion. Therefore, screening tests are carried out on the adhesion promoter modified by modified aliphatic amine, modified alicyclic amine and modified polyamide on silane coupling agent KH-560, as shown in Table 3

Table 3 Effect of different adhesion promoters on adhesion

adhesion promoter

modified aliphatic amine

modified alicyclic amine

modified polyamide

adhesion/mpa

4.61

4.53

4.72

it can be seen from the comparative test that the contribution of modified polyamide modified KH-560 to adhesion is greater than that of modified aliphatic amine and modified grease.Cycloamine, One reason is that the alkalinity of modified aliphatic amine and modified alicyclic amine is stronger than that of modified polyamide, and the reaction activity is stronger than that of modified polyamide, which accelerates the polycondensation of modified resin, thereby reducing siloxane (- sior), which is not conducive to the formation of covalent bond with titanium alloy substrate. Another reason is that the formed compound does not wet the substrate as well as modified polyamide, and its contribution to physical bonding is less than that of polyamide modified silane coupling agent

synthesis of modified polyamide modified KH-560: add the formula amount of modified polyamide resin, methanol and xylene into the reactor, start stirring, wait until the polyamide resin is completely dissolved, and then raise the temperature to (55 ±) 5 ℃, under stirring, drop the silane coupling agent KH-560 in about 1H, and after dropping, keep the temperature at 70 ~ 80 ℃ for 4h, the product is polyamide modified silane resin. Resin synthesis is shown in Figure 1