Development of the hottest polyurethane rubber rep

Development of polyurethane rubber repairing agent

polyurethane adhesive contains groups with strong polarity and chemical activity, such as isocyanate group (NCO), urethane group (nhcoo), etc., and has strong adhesion to a variety of active hydrogen and polar materials. Two component polyurethane adhesive has the advantages of adjustable performance, high bonding strength and wide bonding range, It has become an important part of polyurethane adhesive ". In this paper, two kinds of pre

polymers have been synthesized. The installation, commissioning and maintenance of door and window corner strength testing machine are introduced below: taking full account of the operability and bonding strength of the adhesive, a rubber repair agent with high bonding strength, good operability and moderate hardness has been developed, which has been widely used in all kinds of rubber conveyor belts,

Rubber impellers, rubber valves, Huazhong University of science and technology "Changjiang Scholar" Professor Miao Xiangshui's team repaired and bonded cables, rubber rollers, etc. the cured products have excellent low temperature resistance, oil resistance, solvent resistance, wear resistance, corrosion resistance and good aging resistance

2 experimental part

2.1 main raw materials

tdi, reagents, Beijing chemical plant; Pure MDI, industrial products, Yantai Wanhua; Castor oil, reagent, Zhengzhou No.2 Chemical Reagent Factory; Polyoxypropylene glycol (ppg400,.Ppg700), industrial products

, Tianjin Petrochemical third plant; Polyoxypropylene glycol (2028), industrial products, No. 3 chemical plant of Shanghai Gaoqiao Petrochemical Company; Polyoxypropylene triol (ppt400, ppt700, n3050), industrial products, Tianjin No.3 petrochemical plant; Tackifier, self-made; Moca, industrial products, Suzhou Qianjin Chemical Plant

2.2 preparation of adhesive

2.2.1 preparation of component a

(1) synthesis of TDI prepolymer

add the formulated amount of polyether polyol, castor oil, etc. into a three necked bottle, raise the temperature to 120 ℃, reduce the pressure for dehydration for 1 ~ 2 hours, lower the temperature to about 40 ~ 50 ℃, add the formulated amount of TDI, stir the reaction

for about 2 hours, raise the temperature to 80 ℃, stir the reaction at 80 ± 2 ℃ for another 4 hours, measure the content of NCO%, cool down and discharge, Put it into an iron can and seal it for storage

(2) synthesis of MDI prepolymer

add the formulated amount of polyether polyol, castor oil, etc. into the three mouth bottle, raise the temperature to 120 ℃, dehydrate under reduced pressure for H, lower the temperature to 50 ~ 60 ℃, add the formulated amount of MDI, and raise the temperature to 80 ℃. Stir and react for about 5 hours at

(80 ± 2) ℃, measure the NCO% content, lower the temperature, discharge the material, and put it into an iron tank for sealing and preservation

2.2.2 preparation of component B

add the formulated amount of polyether polyol, castor oil, MOCA and color paste into a three mouth bottle, heat it to 55 ℃, stir it evenly, heat it to 110 ℃, reduce pressure and dehydrate it for 1 ~ 2 hours, cool it down and discharge it, and put it into an iron can for sealing and preservation

2.3 performance test

(1) sample making pour the vacuum defoaming glue solution after mixing into a 2 mm thick PE or PP flat template, place it at room temperature for 24 hours to demould, and continue to place it for 48 hours for standby

(2) gel time: weigh 10g of a and 10g of B respectively, mix them quickly, record the time from the time of mixing to the time of drawing

(3) tensile strength and elongation at break are tested according to GB/t528-92 standard with the samples made in (1) above

(4) peel strength shall be tested according to GB/T standard

(5) hardness (Shore A) shall be tested according to GB/T standard

3 results and discussion

3.1 adjustment of the application period

the prepolymer synthesized with TDI and polyol reacts slowly with the curing agent, and the gel takes 10 hours at room temperature. The prepolymer synthesized with MDI and polyol reacts quickly with the curing agent and releases heat when mixed. This is because the induction effect of TDI prepolymer decreases and the steric hindrance increases, so the reaction speed slows down. However, the induction effect and steric hindrance effect of MDI prepolymer are not obvious because the two one NCO groups of MDI are symmetrically distributed, the phase distance is far, and there is no substituent around. Even if one NCO participates in the reaction, the activity of the remaining one NCO is still large

in this experiment, taking this factor into account, after many tests, two kinds of prepolymers are finally selected to be used together. The best mass ratio is 1:1. See Table 1 for the influence of different proportions on the application period

3.2 effect of prepolymers synthesized by polyols with different molecular weight and different functionality on the properties of adhesives

according to relevant literature, when the mass fraction of isocyanate of two-component polyurethane adhesive is 7%~10%, the bulk strength and bonding strength of the adhesive are the best. In this subject, polyols with different molecular weight

and different functionality were selected to synthesize a series of prepolymers. The mass fraction of the designed prepolymer isocyanate was 9%-10%. After being prepared into adhesives, their properties were tested respectively. According to the comprehensive properties of various prepolymers, two kinds of prepolymers are selected, and other additives are added to prepare component A

(1) control the functionality at about 2.3, select polyols with different molecular weights to synthesize prepolymers with MDI and TDI respectively, then mix them at 1:1 (mass), and mix them with the curing agent in proportion. The influence of prepolymer synthesized by polyols with different molecular weight on the properties of adhesive is shown in Table 2

(2) control the molecular weight at about 1400, select polyols with different functions to synthesize prepolymers with MDI and TDI respectively, then mix them at 1:1 (mass), and mix them with the curing agent in proportion. See Table 3 for the results

it can be seen from the test results that considering the operability of the adhesive, the functionality of polyol is 2.3 and the molecular weight is about 1400, which is ideal

3.3 effect of MOCA dosage

in this test, n3050, castor oil and MOCA are selected as the main components of the curing agent, in which n3050 is used to adjust the hydroxyl content of the curing agent, so that the mixing ratio of a and B components is 1:1 (mass ratio); Castor oil is used to improve the foaming property of adhesive; M OC A is used to adjust the curing speed and hardness, and the results are shown in Table 4

according to the above test results, the mass fraction of MOC A is the best when it is 25%

3.4 effect of castor oil on the foaming property of the repair agent

due to the high activity of one NCO in the two-component reactive adhesive, it will inevitably react with the moisture in the air during curing, release C02, make the adhesive layer produce bubbles,

affect the cohesive strength of the adhesive layer

therefore, we choose the oily castor oil as the main component of the curing agent. Castor oil is the glyceride of fatty acids. The fatty acids contain 90% of ricin oleic acid, namely 9-ene-12-hydroxy-octanoic acid, and the other 10% are oleic acid and linoleic acid without hydroxyl. Castor oil has hydrophobicity, which can reduce the adsorption of water by the adhesive and reduce the probability of nc0 contacting with water. Because

this improves the foaming property of the adhesive layer during curing. We changed the content of castor oil and prepared rubber repair agent according to the same process. After comparison, the test results are shown in Table 5. It can be seen from table 5 that when the mass fraction of castor oil in the adhesive is about 25%, its comprehensive performance is the best

3.5 effect of tackifier on rubber adhesion

polyurethane rubber has excellent wear resistance, corrosion resistance and good toughness. This kind of adhesive is an ideal rubber repair agent, but the strong polarity of polyurethane determines its good adhesion to polar substrates, but its adhesion to non-polar substrates or substrates with small polarity is not ideal. In order to solve this contradiction, a tackifier is synthesized in this subject. The non-polar end of the tackifier can be embedded into the rubber to be repaired, forming a solid valence bond force with it. The other end can react with an NCO to form a firm combination between the rubber to be bonded and the repair agent. See Table 6 for the influence of tackifier on adhesion results

according to the above test results, it is ideal when the mass fraction of tackifier is 2%

3.6 performance of polyurethane rubber patching agent

the polyurethane rubber patching agent was tested after curing at room temperature for 3 days. The test results are shown in Table 7

4 conclusion

(1) the rubber repair agent developed in this subject has good operability. The mass ratio of a to B is 1:1. The cured adhesive forms a solid bond with rubber, and has high cohesive strength. It is a high-strength rubber repair agent

(2) the self-made tackifier has effectively improved the bonding performance of polyurethane adhesive to rubber, and the bonding strength is greater than the bulk strength of rubber

(3) the addition of castor oil improves the hydrophobicity of the adhesive and reduces the adsorption of water vapor on the adhesive layer, thus reducing the generation of bubbles in the adhesive layer and improving the cohesive strength of the adhesive layer