26 июня, 2015 
Malyar The curing reactions of some of the functional groups incorporated into Acrylic Resins for use in surface coating applications are illustrated below.
(i) Reactions of Hydroxyl Containing Polymers with Amino Formaldehyde Resins
The incorporation of hydroxy monomers such as hydroxy ethyl acrylate into the copolymer results in the formation of pendant hydroxyl groups, — OH, at intervals along the backbone of the polymer chain. These OH groups can be made to react with the methylol groups of amino formaldehyde and phenol formaldehyde resins to produce a coherent, resistant film.
The properties of these films are discussed in detail under the relevant heading in the applications section of this book.
Commercially these reactions are carried out under acid conditions where the OH group condenses with the methylol or butylated methylol groups of the amino or phenolic resoles giving a branched or cross linked structure which can be used as a surface coating. Stoving schedules of 125°C for 30 minutes normally suffice to ensure complete cure.
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A cross linked film suitable for use as a surface coating may be obtained by reacting the pendant OH groups of a copolymer with isocyanate groups. The reaction between the OH group and the NCO group results in the formation of a urethane group.
The highly reactive nature of the NCO groups allows the reaction to occur at relatively low temperatures however side reactions can occur between the NCO groups and other active groups present on the polymer backbone.
The precise details of reaction conditions and catalysts are described under the relevant heading in the applications section of this book.
C — O — CH2—CH2OH + OCN—R —NCO + HOCH2— CH2— О — C- II II
С — О — CH2 — CH2 — OOCHN — R — NHCOO — CH2— CH2- О — C — II II
О о
Acrylic polymer backbone A/VW
Figure 1-34
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