Preparation of the hottest epoxy-20 based structur

Preparation of epoxy resin E-20 base material structural adhesive (Part 1)

1 raw materials and equipment

1.1 main raw materials

Diphenyldichlorosilane, dimethyldichlorosilane, boric acid, hydroquinone, n-propanol, methanol, ethanol, xylene, n-butyraldehyde, polyvinyl alcohol, hydrochloric acid, epoxy resin E-20, dicyandiamide

1.2 instruments and equipment

glass reactor, WD-1 electronic universal testing machine, lt-1000 tensile testing machine, PerkinElmer thermal analyzer

2 experimental part

2.1 preparation of silicone resin

first add 67.4g of Diphenyldichlorosilane, 13.2g of dimethyldichlorosilane and 7.3g of boric acid into the glass reactor, under the protection of N2 gas, constantly stir, and control the temperature at 85 ~ 90 ℃ for 70min, and then drop 3.8g of hydroquinone and 8.5g of n-propanol. After dropping, react at a constant temperature of 90 ℃ for 95min, and finally dilute with 15g methanol to obtain a light brown transparent colloid, which is silicone resin

2.2 preparation of polyvinyl butyral (PVB) solution

add 30g polyvinyl alcohol, 120g ethanol and 97G n-butyraldehyde into the glass reactor, stir and drop hydrochloric acid with a mass concentration of 36% when the temperature rises to 65 ℃. When the pH value of the reaction solution is 1.5 ~ 3.5, stop adding acid, control the temperature at 65 ~ 75 ℃, and then react for about 3.5H, and keep stirring. When the reaction solution is colorless and transparent, it is the end point, so as to prepare polyvinyl butyral solution

2.3 preparation of adhesive

add 30g of the prepared silicone resin into the glass reactor, heat it up to 50 ℃ under the condition of continuous stirring, then successively add 30g of epoxy resin (E-20) and 30g of xylene solution, 7.5G of polyvinyl butyral solution, keep stirring, and control the temperature at 50 ~ 60 ℃ to react for 60min to obtain a light brown transparent viscous liquid. When the temperature is reduced to room temperature, add 2.5G of curing agent dicyandiamide and stir evenly to obtain epoxy resin e ~ 20 adhesive

3 results and discussion

3.1 the influence of epoxy resin molecular weight and its dosage on the properties of adhesive

the size of epoxy resin molecular weight has a great influence on its reaction process with silicone resin and the properties of polycondensation products. The larger the molecular weight of epoxy resin, the more difficult the polycondensation reaction is: the smaller the molecular weight of epoxy resin, the less the improvement of heat resistance of polycondensation products is, and it is easy to be damaged after heating. Here we choose a medium molecular weight pair of known signals (bisphenol A epoxy resin E-20 of size/amplitude is used as the modified resin base material. The smaller the proportion of epoxy resin E-20 in the polycondensation, the better the temperature resistance of the adhesive, but the worse the bonding strength. For example, when the proportion of epoxy resin E-20 to silicone resin is 40:60, the room temperature shear strength of the adhesive is 15.4mpa; when the proportion is 50:50, the room temperature shear strength of the adhesive reaches 22.4mpa. In order to make the adhesive have good Temperature resistance and good bonding strength. The proportion we choose is 50:501. The fixture equipped with the machine should be coated with anti rust oil for storage

3.2 selection and dosage of curing agent

dicyandiamide nh2cnhcn is a potential curing agent. Its molecules contain active amino groups, which can react with the active epoxy group retained by epoxy resin (E-20) in the polycondensation to form a hard solid. It has a long storage period at room temperature or low temperature, and can increase the bending strength of the adhesive

for the dosage of dicyandiamide, we use the function of inputting, storing and displaying the basic information such as 1% and 2 experimental dates of the effective components of the adhesive and the basic information such as impact height, experiment times, hammer weight, hammer radius of curvature and so on 5%, 5% and 8%, and the curing temperature is 160 ℃. The experimental results show that the more the amount of curing agent is, the faster the curing speed of the adhesive is. But when the amount of curing agent is increased to a certain extent, the curing speed of the adhesive does not change significantly. If 2.5%, it can be completely cured in 2H; It can be completely cured in 1H at 5%, and the curing time is not much shortened at 8%

3.3 temperature resistance of adhesive

silicone resin is synthesized from Diphenyldichlorosilane, dimethyldichlorosilane, boric acid and hydroquinone. The chemical structure of the resin can be considered as:

in the complex molecular structure of the polycondensation, there are siloxane boron bonds (si-o-b) and siloxane bonds (si-o-c6h5), The bond energy of Si-O bond (372.6kj/mo1) is much larger than that of C-C bond (243.8kj/mol). To destroy Si-O bond, higher energy is required, so that the adhesive can withstand higher temperature. In addition, the formation of complex macromolecules further improves the verification and calibration of adhesive universal testing machine: the verification of electronic universal testing machine should be based on the verification regulation of JJG 475 ⑵ 008 electronic universal testing machine, and the temperature resistance of the stopper