Issues regarding composition changes in the copolymerization of polyoxymethylene
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In copolymerized formaldehyde, as the proportions of impurities such as H2O/HCHO/CH3OH/HCOOH/RT18/RT40 increase or decrease, how should the contents of the main synthetic substances in the copolymer, namely BF3/DOX/TOX/MEAL, be adjusted? Expert advice is sought. . . . . . And also, in the reaction, how do adjustments made to BF3/DOX/TOX/MEAL affect the resulting POM, described from aspects such as melting point, MI, unstable end groups, formaldehyde gas, and WLH; it can also be described from macroscopic aspects such as polymer molecular weight – looking forward to that. . . . . .
That’s a good question; I’m curious about it too. As far as I know, your questions can all be considered in terms of hydroxyl groups. For MI specifically, there’s a balance between different factors; for other issues, it’s best to consult the opinions of other experts!
Why is it said to be converted into a hydroxyl group? Why is this? Why hasn’t anyone mentioned this issue? I’m worried!
Reply to 3#: Wishing everyone happiness. Why is it converted into hydroxyl groups?
I would like to ask what the components of RT18/RT40 are. It would be best for you to conduct qualitative and quantitative analyses. In POM production, H2O, MEAL, and CH3OH all act as chain transfer agents used to regulate the molecular weight, and they are closely related to the MI value.
Reply to 6# hjx03032102: CH3O-(CH2)3OCH3 is RT18; RT40 is the product of the reaction between formaldehyde and dipentene. It remains to be determined how these substances affect polymerization during the reaction. Thank you
Reply to 7# eastvs860202: Substances like these are generally chain transfer agents that terminate the reaction; they affect the molecular weight of the polymer, reducing it. This results in an increase in the MI value； The increase in unstable groups at the ends of the molecular chains results directly in an increase in HO,; therefore, the quality of the monomer is extremely important during the production of polyoxymethylene.
Reply to 7# eastvs860202: For polyoxymethylene, the unstable part is the unoxidized methylene group at the ends; its structure is R-C-OH, and this structure is unstable and tends to decompose when heated. Therefore, post-treatment is necessary for it. What 2# mentioned about converting it into hydroxyl groups is based on this principle – an increase in -OH groups indicates a higher amount of unstable components in the polymer, and during post-treatment, large amounts of formaldehyde are released, which hinders the proper operation of the extruder
It seems the original poster missed mentioning an RT7 as well. The key lies in figuring out how to reduce these impurities; as for how to make adjustments, the poster will find the answer in the summary of subsequent production data
I’m pushing such posts to the top, hoping to find a satisfactory answer on the forum