Search results
Results from the WOW.Com Content Network
At or near the final stages of production, the material is treated with a chain extender. Typically, chain extenders are bifunctional, i.e., they have two functional groups, which can link together two polymers. Representative classes of chain extenders are diglycidyl ethers, diols, diamines, or dianhydrides. Chain extenders are often applied ...
1,6-Hexanediol can improve the hardness and flexibility of polyesters as it contains a fairly long hydrocarbon chain. In polyurethanes, it is used as a chain extender , and the resulting modified polyurethane has high resistance to hydrolysis as well as mechanical strength, but with a low glass transition temperature.
It is a diamine and thus in polymer science terms is a Chain extender rather than a chain terminator. Chain extenders ( f = 2) and cross linkers ( f ≥ 3) are low molecular weight amine terminated compounds that play an important role in polyurea compounds, elastomers and adhesives .
2-Methylpentamethylenediamine can also be used as a chain extender for polyurethane applications, and in particular with PUDs. [3] [4] Its derivatives like aspartic esters, secondary amines, aldimines and ketoimines serve as curatives in polyurea systems. In polyamides, 2-Methylpentamethylenediamine acts as a crystallinity disruptor.
TPU is a block copolymer consisting of alternating sequences of hard and soft segments or domains formed by the reaction of (1) diisocyanates with short-chain diols (so-called chain extenders) and (2) diisocyanates with long-chain diols. By varying the ratio, structure and/or molecular weight of the reaction compounds, an enormous variety of ...
Elongation of the fatty acid follows the same biosynthetic pathway in Escherichia coli used to produce straight-chain fatty acids where malonyl-CoA is used as a chain extender. [27] The major end products are 12–17 carbon branched-chain fatty acids and their composition tends to be uniform and characteristic for many bacterial species. [26]
In polymer chemistry, chain transfer is a polymerization reaction by which the activity of a growing polymer chain is transferred to another molecule: [1] [2] + + where • is the active center, P is the initial polymer chain, X is the end group, and R is the substituent to which the active center is transferred.
Synthesis of polyurethane from a diisocyanate and a diol. To cap this polymer, chain extenders of either diols or diamines can be added in order to tailor the properties. The mechanical properties of biodegradable polymers can be enhanced with the addition of fillers or other polymers to make a composite, blend, or copolymer.