The aim of most chemical recycling procedures is obtaining monomers such as terephthalic acid (TPA), ethylene glycol (EG), bis(2-hydroxyethyl)terephthalate (BHET), and PET oligomers with carboxyl, hydroxyl and amine end groups.
Then products having amine end groups as well as carboxyl and hydroxyl end groups were evaluated as polyurethane surface coating materials (31).
The experimental results are used to build a semi-empirical dynamic mathematical model that predicts the effects of catalyst concentration, temperature, moisture level and time on the concentrations of unreacted carboxyl and amine end groups.
Equations (1) and (2) are dynamic material balances on amine end groups (A), carboxyl end groups (C) and water (W) in the molten polymer phase.
This facilitated the reaction between the acid-functional terpolymer and the amine end
groups of the nylon.
The rheological properties of the ternary blends suggested that excessively high reactivity between amine end groups of PA6 and MAH grafted onto EVA makes the compatibility between PET and PA6 worse, although EVA-g-MAH was expected to work as a compatibilizer for PBT/PA6 blends.
Also, the grafted maleic anhydride readily reacts with the amine end groups of polyamide to give a graft copolymer (5-12).
13 and PA chains are predominantly coupled to EPM-g-MA chains via the PA amine end groups, for blend 4 (10/90, w/w) the MA/amine ratio is 4.
As discussed above, in the case of blends PA-6 degradation can be even more significant, as the water formed during the reaction between PA's amine end groups and EPM-g-MA's anhydride groups can hydrolyze the PA's amide groups increasing chain scission.
For example, the carboxyl moieties can interact though chemical reaction in the melt with the amine end groups of the PA-6,6 to yield PP-g-PA graft copolymers (37).
For the anhydride f-PP compatibilized system containing greater than 10% f-PP, the sudden decrease in impact strength may be explained by considering the total concentration of MAH (grafted and ungrafted) added to the blend, relative to the quantity of available amine end groups on the PA-6,6.
It is not a simple case of favouring amine ends
over acid, or vice versa, however; both have problems.