PU chain extenders play a crucial role in the synthesis of polyurethane (PU) materials. The following is a detailed introduction about PU chain extenders:
definition
PU chain extender refers to low molecular weight alcohols and amine compounds that can extend, expand, or form spatial network cross-linking of molecular chains. In the synthesis of polyurethane materials, chain extenders mainly participate in the chain extension and crosslinking processes of polyurethane, thereby affecting the physical and chemical properties of polyurethane.
type
The types of PU chain extenders mainly include the following:
Polyol chain extenderSuch as 1,4-butanediol, ethylene glycol, propylene glycol, neopentyl glycol and other binary alcohols, as well as propylene glycol, trihydroxypropane and other ternary alcohols. This type of chain extender has a low molecular weight and is easy to react with isocyanates, which has a significant effect on the hard segments of the polymer, thereby affecting the strength and modulus of polyurethane.
Binary amine chain extenderIncluding 3,3 '- dichloro-4,4' - diaminodiphenylmethane (MOCA), 3,5-diamino-p-chlorobenzoate isobutyl ester, diethyltoluene diamine (DETDA), etc. This type of chain extender has a fast reaction speed, but is difficult to control during operation. They react with isocyanates to form urea groups, endowing polyurethane polymers with excellent physical and mechanical properties. Aromatic diamine chain extenders are currently the most common, widely used, and largest quantity of polyurethane chain extenders in the market.
Alcohol amine chain extenderSuch as ethanolamine, diethanolamine, triethanolamine, etc. This type of chain extender contains both hydroxyl and primary, secondary, and tertiary amino groups in both aliphatic and aromatic compounds. It not only has the function of chain extension and cross-linking, but also has a certain function of regulating the shelf life.
function
PU chain extenders have the following main functions in the synthesis of polyurethane materials:
Chain extension and cross-linkingChain extenders can rapidly expand and crosslink with polyurethane reaction systems, thereby forming high molecular weight polyurethane materials.
Adjust reaction rateChain extenders have characteristic functional groups that undergo chemical reactions with the reaction system. They have low molecular weight, are reactive, and can effectively regulate the reaction rate of the reaction system.
improve performanceBy introducing chain extenders, certain characteristics of the chain extender molecules can be incorporated into the polyurethane main chain, improving certain properties of polyurethane such as strength, hardness, heat resistance, etc.
application
PU chain extender is widely used in polyurethane foam, polyurethane elastomer, polyurethane adhesive and other fields. Different types of chain extenders are suitable for different polyurethane materials and application scenarios.
matters needing attention
When using PU chain extenders, the appropriate type and amount of chain extenders should be selected based on the specific polyurethane material and application scenario. At the same time, attention should be paid to the safety and environmental friendliness of chain extenders to avoid adverse effects on human health and the environment.
