Abstract. An investigation was made of grafting trans-ethylene-1,2-dicarboxylic acid (TEDA) onto metallocene-linear low-density polyethylene (mLLDPE) and low-density polyethylene (LDPE) in the course of reactive extrusion. The initiator was 1,3-bis-(tert-butyl-peroxyisopropyl)benzene. The graft efficiency of TEDA has been shown to increase with increasing initiator concentration, irrespective of polyethylene type. The graft values for LDPE were higher than for mLLDPE over the initiator concentration range (0.05 to 0.4 wt%). The rheological properties of mLLDPE were found to undergo more tangible changes during functionalization than those of LDPE. These changes were caused by side reactions, mainly macromolecular crosslinking. It has been established that some carboxyl groups get transformed to anhydride groups in the grafted product. The concentration of end double bonds reduces, but intramolecular unsaturation in both polyethylenes increases. Data are presented on thermal and stress-strain (mechanical) properties of virgin and functionalized polymers, as well as rheological and viscoelastic properties of their melts.

Distinctive features of free-radical grafting of trans-ethylene-1,2-dicarboxylic acid (TEDA) onto macromolecules of molten ethylene-vinyl acetate copolymer (EVA) in the course of reactive extrusion have been investigated along with structure, mechanical characteristics, and high-elastic properties of molten functionalized products (EVA-g-TEDA). It is shown that EVA-g-TEDA yield depends on both the peroxide initiator concentration and content of vinyl acetate units in the copolymer molecular structure. At functionalization, acid grafting is accompanied by secondary reactions of macromolecular degradation and crosslinking. With a low-peroxide initiator concentration (0.1 wt %), degradation prevails; with a higher (0.3 wt %) concentration, crosslinking of macromolecules prevails. It is reported that monomers being grafted attach mostly over secondary carbon atoms in the polymer chain. EVA-g-TEDA appears to have a less perfect crystal structure with a lower-melting temperature and crystallinity as against the starting polymer. The functionalized products display enhanced rigidity and lower deformability in comparison with the initial copolymer. Variations in the swelling ratio and melt strength of EVA-g-TEDA depend on the course of competing secondary processes of macromolecular degradation and crosslinking.

No abstract

No abstract

A number of unsaturated 4-methylene-1,3-dioxolanes were synthesized and described and their polymerization carried out in the presence of radical initiators both in mass and in solution. It has been established by data of IR and PMR spectra of the obtained polymers that the homopolymerization of the synthesized monomers proceeds both with the simultaneous participation of a methylene double bond and a dioxolane cycle with the formation of linear structural links with ketoester fragments, and only with the participation of a methylene group with the formation of links with dioxolane cycles as side groups. It has been revealed that the ratio of forming linear and cyclic structural links depends on monomer concentration and polymerization temperature. It has been established that with increase ofthe monomer concentration during polymerization in solution, the fraction of cyclic elementary links is increased, but in all cases of polymerization, the fraction of linear links prevails over the cyclic one. It has been found that with increase of the polymerization temperature, the fraction of links with the opening of the dioxolane cycle in the macrocycleis increased. The kinetics of the polymerization process was studied, and the reaction orders on monomer and initiator revealed, and the activation energy of the process was calculated. The lower value of the reaction order on monomers in comparison with polymerization of vinyl monomers was explained by availability of two various types of growing radicals in the system and their participation in the chain break reactions.