Search

A novel macromolecular auxiliary antioxidant with polyethylene (PE) as polymer skeleton and phosphites as side groups is prepared based on commercial ethylene‐vinyl acetate (EVA) copolymers and its potential as polyolefin stabilizers is studied in depth. The synthesis approach of this PE‐grafted antioxidant consists of a typical EVA hydrolysis reaction and a two‐step nucleophilic substitution reaction of PCl3, 2,4‐di‐tert‐butylphenol, and the hydrolysis product. Results of the thermogravimetric analysis show that the macromolecular structures endow the as‐synthesized antioxidant with much better thermal stability than that of the commercial antioxidant 168. In addition, antioxidant behaviors of the PE‐grafted antioxidants in polypropylene (PP) matrix are investigated in detail through characterization of the melt flow index of multiple‐extruded stabilized PP as well as the short‐term oxidation induction time test and the long‐term thermo‐oxidative aging test. Results show that even with extremely low content of the effective antioxidant groups, the as‐synthesized macromolecular antioxidant still has excellent antioxygenic properties. [ABSTRACT FROM AUTHOR]

Novel polyethylene‐based (PE‐based) antioxidants derived from commercially available ethylene‐vinyl acetate copolymer (EVA) with PE as the backbone and hindered phenols as side groups are prepared, and their potential for application as non‐migrating polyolefin stabilizers is investigated. The synthesis route contains the typical hydrolysis of EVA and transesterification reaction between the hydrolysis product and methyl 3‐(3,5‐di‐tert‐butyl‐4‐hydroxyphenyl) propionate. Thermal stabilities of these PE‐based antioxidants (AO‐PE) are studied through thermal analysis under an air atmosphere and shown to be higher than those of antioxidant 1076 and antioxidant 1010 (AO‐1010) due to their macromolecular structures. Antioxidant activities of the AO‐PE are evaluated in polypropylene (PP) by measuring the melt flow index of multiple‐extruded stabilized PP, and the results demonstrate that the antioxidant effectiveness of these antioxidants is strongly related to the molecular weight. [ABSTRACT FROM AUTHOR]

A new synthetic procedure is described for the preparation of dendritic polyethylene brushes with polysiloxane as the main chain, describing for the first time that it is possible to simply and efficiently prepare highly branched architectures for this type of polymer. Furthermore, as a result of the polymer brush architecture, polyethylene acts as the side chains and Si-O-Si as the backbone. The number average molecular weight (Mn) of the polyethylene brushes, which is determined using a multiple angle laser light scattering detector, increases from 5946 to 27 684 g mol-1 while retaining relatively narrow polydispersities (1.5-2.4). The polymer brushes are characterized by solid 29Si NMR and high-temperature ¹H NMR spectra. In addition, X-ray photoelectron spectroscopy and gel permeation chromatography were used to confirm the structure. [ABSTRACT FROM AUTHOR]

Chain-end-functionalized polyethylenes (Cef-PEs: PESSH (Cef1), PESfurfuryl (Cef2), PESNH2 (Cef4), PESNH2•HCl (Cef5), PESCOONa (Cef6), PESCHA(Cef7), PESSO3Na (Cef8), PESOH (Cef9) and PESCOOH (Cef10)) are synthesized by thiol-ene addition of vinyl-terminated polyethylene (v-PE) with 1,2-ethanedithiol, furfurylmercaptan, cysteamine, cysteamine hydrochloride, sodium thioglycolate, L-cysteine hydrochloride, sodium 2-mercaptoethanesulfonate, mercaptoethanol, and thioglycolic acid, respectively. PEStNCO (Cef3) is obtained by subsequent reaction of Cef9 with anhydrous 4,4′-MDI. Cef-PE1-8 are reported for the first time. The conversions of all the reactions are up to 95%-100%. All the Cef-PEs are characterized by NMR, GPC, DSC, FT-IR, and TGA. In the experiments, it is found that alkaline mercaptans and solvents are adverse to the thiol-ene click reactions. [ABSTRACT FROM AUTHOR]

Four novel well-defined polyethylene-bound antioxidants (PE-bound antioxidants) with distinct secondary structures are synthesized via transesterification reactions between methyl 3-(3,5-di- tert-butyl-4-hydroxyphenyl)propionate and hydroxyl-terminated polyethylenes. The results of thermal gravimetric analysis under an air atmosphere demonstrate that the thermal stabilities of PE-bound antioxidants are higher than that of commercial antioxidant Irganox1076 and are strongly related to their chemical structures. Particularly, the most thermally stable PE-bound antioxidant is the one bearing both primary and secondary antioxidant moieties. The antioxidant activities of the PE-bound antioxidants are evaluated in polypropylene by their melt flow index. [ABSTRACT FROM AUTHOR]