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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 ...
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.
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 .
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 ...
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.
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.
The most important chain extenders are ethylene glycol, 1,4-butanediol (1,4-BDO or BDO), 1,6-hexanediol, cyclohexane dimethanol and hydroquinone bis(2-hydroxyethyl) ether (HQEE). All of these glycols form polyurethanes that phase separate well and form well defined hard segment domains, and are melt processable.
Polyketide synthases are also broadly divided into three classes: Type I PKSs (multimodular megasynthases that are non-iterative, often producing macrolides, polyethers, and polyenes), Type II PKSs (dissociated enzymes with iterative action, often producing aromatics), and Type III PKSs (chalcone synthase-like, producing small aromatic molecules).