Melt free‐radical grafting of maleimides with hindered phenol groups onto polyethylene

Abstract

A monomeric antioxidant, bearing carbamate groups, was synthesized from the reaction of 3,5-di-tert-butyl-4-hydroxybenzyl alcohol and azidomaleimide. Another antioxidant was prepared from the reaction of N-(4-hydroxyphenyl-)maleimide and 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic chloride in the presence of triethylamine. These fictional antioxidants were grafted onto polyethylene (PE) via melt processing with free-radical initiators in a minimax molder. The IR spectra of the grafted PE showed that the monomeric antioxidants were added to PE. IR spectroscopy methods were used for the quantitative determination of the extent of grafting of the monomeric antioxidants. Also, the extent of crosslinking was determined from the gel content. To optimize the reaction conditions, we investigated the effects of the initiator concentration, monomeric antioxidant, reaction time, and temperature on the extent of grafting.

Synthesis and Properties of Polyethylene‐Bound Antioxidants

“…Many approaches have been developed to retard the physical loss of antioxidants, such as producing antioxidants with high MW, immobilizing antioxidants onto nanoparticles, and chemically attaching antioxidants to polymers. Polymer‐bound antioxidants can be prepared by (co)polymerizations of monomers bearing stabilizing functionalities and polymer functionalization of: i) pre‐functionalized polymer bearing reactive groups with low‐MW compounds bearing stabilizing moieties and ii) conventional polymers with monomers bearing stabilizing moieties . Studies already show that the ideal stabilizer should be highly soluble, minimally diffusive, and homogeneously distributed in the polymer matrix .…”

Developing Polypropylene Bonded Hindered Phenol Antioxidants for Expanding Polypropylene Applications in High Temperature Conditions

“…However, there are only few reports [12][13][14][15] discussing PE and PP-bonded hindered phenol antioxidants. Most synthesis routes are based on free-radical mediated copolymerization and grafting reactions with monomers containing hindered phenol moieties [16][17][18][19][20][21]. The free radical grafting reactions on PE and PP polymers are usually accompanied with many side reactions [22], including the chain degradation shown in Scheme 1, low yield, by-products, and colored material.…”

Polyolefin elastomer grafted unsaturated hindered phenol esters: synthesis and antioxidant behavior

“…[1][2][3] Also, radicals and active oxygens from materials which are in direct contact with foods can be responsible for severe diseases or even cancer. [4] To address the issue, it has been suggested to add sufficient amounts of stabilizers based on material type to inhibit degradation.…”

“…[6][7][8][9] This phenomenon results in reduced life time and properties of polymeric materials and possible health risks due to unwanted release of such stabilizers when polymers used for food packaging. [1,2,9] There have been research efforts to develop supramolecular stabilizers with reduced mobility and volatility to improve the long-term stability of polymeric products, especially packaging films and pipes. [10][11][12] The reports generally categorized as two approaches: stabilizer immobilization and high molecular weight, olefin-based antioxidants [13] to provide homogeneous distribution in polymer.…”

“…[14] Also, free radical grafting of antioxidants based on maleimides onto PE and polypropylene, provided covalently bonded stabilizers to matrix. [1] Another approach is copolymerization of monomeric stabilizers with vinyl monomers through radical polymerization and ring-opening metathesis polymerization (ROMP). [11,15] Moreover, few studies have reported coordination copolymerization of monomers having antioxidant moieties with ethylene via organometallic catalysts.…”