What are the important applications of silicone sealants in engineering?

2019-08-29 10:24:06

The main structure of polyurethane sealant is carbamate formed by the reaction of isocyanate and active hydrogen. It is characterized by good adhesion to various substrates, excellent toughness, good sealing performance, water and gas insulation. But the performance is poor at high temperature and humidity.

Silicone sealant has a structure of siloxane as the main chain, side chain or end group with functional groups, which plays a role in polymerization. Its characteristics are UV aging, thermal aging performance is very stable. But the bonding performance and sealing performance are poor.

Non-structural adhesives have low strength and poor durability. They can only be used for bonding, sealing and fixing of ordinary and temporary properties, but can not be used for bonding of structural parts.

The service life of construction projects is generally more than 50 years. Components bear relatively large and complex stresses, which directly affect the safety of people's lives and property. Structural adhesives should be used for bonding. Structural adhesives are widely used in engineering. They are mainly used for strengthening, anchoring, bonding and repairing components, such as bonding steel, bonding carbon fibers, rebar planting, crack strengthening, sealing, hole repairing, nail sticking, surface protection, concrete bonding, etc.

The glue beater is an automatic equipment specially designed to control the coating of adhesives and other coatings and apply them to the surface of products drip by drip. It feeds the paint into the rubber feeding pipe by compressed air, and then drips or coats the paint according to the pre-set path through program control.

Working Principle: Compressed air is fed into the rubber bottle (syringe), and the rubber is pressed into the feed pipe connected with the piston chamber. When the piston is in the upper stroke, the piston chamber is filled with rubber. When the piston pushes down the needle, the rubber is pressed out from the needle nozzle. The amount of glue emitted is determined by the distance from the piston down, which can be adjusted manually or controlled in software.

Sealant is a kind of sealant with certain cohesiveness, which deforms with the shape of sealing surface and is not easy to flow. It is an adhesive used to fill the gap between configurations and act as a sealant. It has the functions of leak proof, waterproof, vibration proof, sound insulation and heat insulation. It is widely used for sealing construction, transportation, electronic instruments and components. Due to the variety of sealants, strict operation methods, and bad competition in the market, the sealing effect of sealants is not good. Next, we will analyze the phenomena and reasons of sealant unqualified.

The service life of doors and windows sealants is understood by different people as "shelf life" before construction and "durable life" after curing construction respectively; "shelf life": the shelf life of single component polyurethane sealants is directly related to the technology of manufacturers, and the products produced by small manufacturers generally have shorter shelf life; and the shelf life is also related to storage strips. The higher the storage temperature/humidity, the shorter the shelf life. Usually referred to as the shelf-life is at 23 degrees, humidity about 50% shelf-life. The shelf life of ordinary products is more than 9 months, and products with special requirements can reach more than 2 years. However, many products on the market have shelf life less than 3 months. Product failure is characterized by difficult extrusion, or even solidification in packaging.

"Durable life": The durable life after curing is the period for the product (sealant) to exert its function. According to the simulated accelerated aging test in laboratory, the service life of polyurethane sealant is 15-20 years. Because polyurethane sealant is developed relatively late in China, there is no engineering case that has been applied for such a long time in practical application at present. Case.