Preparation of Telechelic Oligomers by the Thermal Degradation of Syndiotactic Polypropylene

Alder Ene functionalization of polypropylene through reactive extrusion

“…Supporting evidence of the benefits of thermolysis was shown by Sawaguchi and Seno, 16 who thermally degraded polypropylene at 370°C in a Pyrex glass tube to produce a telechelic polymer with diisopropenyl (vinylidene) end groups. Based on nuclear magnetic resonance (NMR) analysis, 16 they determined the average functionality of isopropenyl groups per molecule to be 1.8 after an excessively long reaction time of 45 min, showing this method to be highly efficient for producing the desirable vinylidene group.…”

“…Commercial polypropylene resins generally lack this reactive site due to the method of chain termination and even in the new metallocene-based resins where the vinylidene is more prevalent, the high molecular weight of the polymer chain translates into doublebond concentrations too low to accurately identify by modern analytical methods. Therefore, the degree of unsaturation of polypropylene must be increased by ␤-scission 16,17 before this reaction. The enophile of the Alder Ene reaction possesses a double bond, preferably an ␣,␤-disubstituted unsaturated group that is less prone to polymerization, such as maleic anhydride.…”

Synthesis of Long-Subchain Hyperbranched Polypropylene Using Thermally Degraded Products as Precursor

“…The first is physical recycling through melt mixing (such as extrusion) of the used PP with or without fillers, which always encounters the problem of decline in mechanical properties during the procedure. Thus, the final recycled products are usually used in low-end fields. , The second is chemical (or feedstock) recycling through pyrolysis or thermal degradation to convert PP into small molecules that are used as fuel , or oligomers, respectively . For obtaining high value-added products from waste plastic using a small amount of energy, controlled partial degradation might be a more attractive upcycling route compared with the route for recovering the original monomer units from some polymers (such as polyethylene and PP) .…”

“…PP can be thermally degraded into difunctional low-molecular-weight products with two isopropenyl groups at each chain end (PP-TVD, for short) through the β-elimination reaction . These terminal double bonds can be readily converted into more active groups such as hydroxyl and amino groups, which opens the door for using the thermal degradation products of PP to prepare polymers containing the PP block.…”

“…6,7 The second is chemical (or feedstock) recycling through pyrolysis or thermal degradation to convert PP into small molecules that are used as fuel 8,9 or oligomers, respectively. 10 For obtaining high value-added products from waste plastic using a small amount of energy, controlled partial degradation might be a more attractive upcycling route compared with the route for recovering the original monomer units from some polymers (such as polyethylene and PP). 11 Very recently, it has been proposed to pay more attention to the chemical recycling of waste plastic in order to promote a closed-loop plastic economy.…”