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the sealing material
Apr 09, 2018

1 PVC resin

It is the body of the sealing material, can be 65% to 75% of all materials from the sealing conditions of use and use life of life, should choose high average molecular weight of suspension polymerization resin, to ensure that the product have enough tensile properties and good elasticity. However, with the increase of the average molecular weight of PVC resin, the processing liquidity of the resin becomes worse. Therefore, when choosing the suspension method PVC resin, the factors of product performance and processing performance should be taken into consideration.

The composition of two rubber compounds.

It is with PVC resin blend of elastic material, usually 10% to 15% of all materials, according to the principle of polymer blends, want to use PVC resin and the solubility parameters of similar analysing or elastomers, such as nitrile butadiene rubber (powder powder), chloroprene rubber, polyurethane and ELVALOY E - VA - namely CO (ethylene - vinyl acetate - polar monomer terpolymer), etc., these rubber or elastic body after he was added to PVC resin, not only gives sealing strip good elasticity, also can have the effect of PVC plasticizer permanent, so in this permission, can consider to increase the amount of rubber. In the rubber toughening component, we also need to add additives such as anti-aging agent, so as to ensure that the product has sufficient service life.

3heat stabilization system.

PVC resin is heat sensitive resin, and its thermal stability is very poor, such as PVC resin rose to 100 ℃, which can produce decomposition, more than 50 ℃, 1 break down quickly, produces a large amount of hydrogen chloride gas. The resin decomposition temperature is lower than the flow of its processing temperature (170 ℃) that cannot be processed. For this purpose, it is necessary to consider adding sufficient and effective thermal stabilizers in the formulation design. It is characterized by the absorption of hydrogen chloride, so it is called the acceptor of hydrogen chloride, usually with metal soap and lead salt heat stabilizer. The former are such as calcium stearate and lead stearate. The latter, such as dibasic phosphate, tribasic lead sulfate, etc. Because there is a certain synergistic effect between each thermal stabilizer, it should be matched with each other to receive reliable thermal stability effect and reduce the cost as much as possible. Generally, the total amount is about 5%-7% of PVC resin. 

4.

PVC resin is a highly polar polymer, its molecular chain is very powerful, and the PVC material without plasticizer is inelastic and flexible. Adding a proper amount of plasticizer to PVC resin can weaken the force between the PVC macromolecule, reduce the glass temperature of PVC material, and make the material more elastic. At the same time, the addition of plasticizer can reduce the melt viscosity, so that the processing performance can be improved. It can also reduce the plasticizing temperature. 

Sealing strip using plasticizer should consider the principle is: 

(1) pay attention to the plasticizer that can increase the durability of the sealing strip and minimize the use or use of plasticizers, such as dibutyl phthalate (DBP), etc. 

(2) avoid or reduce the pollution on the surface of the product. 

(3) there should be good synergies between the selected plasticizers. Should also be considered when determining the plasticizer dosage, the filling material variety and its content, because they are sealed for the hardness, tensile elongation, compression and brittleness temperature has direct impact on technical, so should be integrated balance. 

The conventional plasticizers used for sealing strips are dioctyl phthalate (DOP) and dioctyl sebacate (DOS), which are used in high-rise and cold zone building seals.