Solvent-free peroxide-initiated polymer modifications are widely used to improve the physical and/or chemical properties of commodity plastics and elastomers. Although the reactions that underlie polymer grafting are known, our understanding of H-atom transfer reactions in this context is incomplete. Fundamental questions remain unanswered, such as the difference in reactivity between different polymers (polyethylene versus polypropylene and polyisobutylene) and differences in the regiochemical outcomes of grafting reactions upon them. Herein, experimental data pertaining to the H-atom transfers involved in polyolefin graft modifications were obtained to improve our fundamental understanding of these reactions by using radical-trapping techniques and quantum chemical calculations. In this project, experimental measurements of the efficiency of H-atom abstraction by t-butoxyl radicals from polyolefins, and suitable model compounds such as pentane, 2,4-dimethylpentane and 2,2,4,4-tetramethylpentane were determined. Insight is gained from alkyl-trapping experiments to quantify the relative reactivities of the primary, secondary and tertiary positions of the model compounds. Experimental data were compared to quantum chemical calculations, which revealed that entropic effects dictate the regioselectivity and preclude abstraction at the secondary position in favour of the less enthalpically-favourable primary abstraction site. MP2 and CBS-QB3 level calculations were able to reproduce experimental trends in model compound reactivity, while the highly common B3LYP density functional, used in other investigations on the subject, could not. / Thesis (Master, Chemical Engineering) -- Queen's University, 2011-10-20 16:48:38.083

Acryloyloxybenzoic acid (ABA) was prepared by the condensation reaction of acryloyl chloride with p-hydroxybenzoic acid in alkaline medium. The polymerization and grafting of ABA onto Polypropylene were anticipated to occur simultaneously in melt mixing at high temperature. The monomer showed liquid crystalline property. For a better dispersion of ABA in PP before graft copolymerization, a masterbatch of 50-50 (by weight) low density polyethylene + ABA was prepared, which was then used for 5, 10, 15 % ABA + PP mixtures in the Brabender Plasti Corder. Furthermore, these compositions were reprocessed at the same temperature in the molten state. Compression molding was used to prepare films for characterization experiments at 200 &ordm / C under 15000 psi for approximately 3-5 minutes. The graft copolymers were characterized by several techniques / DSC, FTIR, MFI, SEM and mechanical testing. In DSC thermograms the crystallization of PP was seen at approximately 160&ordm / C. An endothermic peak was also assigned to grafted PABA at 280&ordm / C . The incorporation of ABA onto the PP backbone as a graft copolymer (PABA-g-PP) at low percentages results in a possible rearrangement, where tensile strength values increased, while strain decreased. The grafting goes through thermal radicalic mechanism. MFI values were found to increase from 8.7 to 16.35 g/10 min at 10 wt % ABA, then decreased to 10.57 g/10 min at 15 wt % ABA. It is most likely that the presence of PABA produced easy orientational flow up to 10 % of ABA, but at 15 % ABA addition caused a slight decrease in MFI. The tensile test specimens were analyzed by Scanning Electron Microscope. None of the three samples exhibited phase separation. This observation confirms that the graft copolymerization occurrs in a homogenous manner onto PP. The brittle nature of material is observed at all three compositions.

GRAFT COPOLYMERIZATION OF p-ACRYLOYLOXYBENZOIC ACID AND p-METHACRYLOYLOXYBENZOIC ACID ONTO ISOTACTIC POLYPROPYLENE The monomers, p-acryloyloxybenzoic acid (ABA) and p-methacryloyloxybenzoic acid (MBA) were synthesized by condensation reaction of corresponding acid chlorides with p-hydroxybenzoic acid in alkaline medium. The polymerization of the monomers were studied by several techniques. Polyacryloyloxybenzoic acid (PABA) was obtained by &amp / #947 / -radiation induced, solution and bulk melt polymerization by initiation of dicumyl peroxide (DCP). Polymethacryloyloxybenzoic acid (PMBA) could be obtained by only bulk melt polymerization. The graft copolymerization of the monomers onto isotactic polypropylene, IPP, was successfully carried out only with bulk melt polymerization. The IPP used in the graft copolymerization was firstly subjected to &amp / #947 / -radiation to create active sites for grafting. The graft copolymerization of the monomers, ABA and MBA onto IPP were initiated by these active sites. The grafting was studied at constant concentration of the monomers in the reaction mixture (50%) and at different reaction temperatures (170, 185, 202, 215 and 225&deg / C). The maximum grafting of PABA and PMBA were found to be 33.1% and 33.9% in the graft copolymers, respectively. The maximum grafting was reached in shorter times at higher temperatures, and it also increased with the increase of concentration of the monomers in the reaction medium. The graft copolymerization was also carried out by using initiator, DCP at 170&deg / C, however, the grafting extent was lower due to the homopolymerization of the monomers and the direct reactions between peroxides of initiator and peroxides on IPP. The graft copolymers were characterized by several techniques, DSC, WAX, TG/IR, MS, SEM and mechanical testing. The formation of both crystalline forms of (&amp / #61537 / 1 and &amp / #61537 / 2) were observed in the products obtained at 170&deg / C. The graft copolymerization of ABA did not have any significance on the formation of both forms of &amp / #61537 / form, while MBA lead to increase in &amp / #61537 / 2 form. The &amp / #61538 / crystalline modification formed in PABA-g-PP products obtained at 185&deg / C and at higher temperature and also in the second run of DSC studies after fast cooling. &amp / #61538 / form was not observed in graft copolymers of PMBA The decomposition mechanism of PABA, PMBA and the graft coproducts were studied by mass spectrometry and TG/IR. The polymers degraded predominantly by decomposition of side groups giving phenol, benzoic acid, hydroxybenzoic acid, carbondioxide and cyclodiene mainly. The mechanical properties of the graft copolymers showed an improvement particularly in tensile strength and modulus. The maximum tensile strength and modulus of PABA-g-PP were found as 41.1 and 881 MPa, and the values of PMBA-g-PP were measured as 35.9 and 721 MPa, respectively. These values were 28.1 and 486 MPa for irradiated IPP and 33.9 and 632 MPa for virgin IPP, respectively. The copolymerization of ABA did not alter the impact properties of the graft copolymer, while a slight decrease was observed in PMBA-g-PP samples. The tensile and impact fractured surface of the graft copolymers studied by scanning electron microscopy showed homogeneous structure. The brittle nature with some extent of ductility was seen in the samples.

The monomer, p-acryloyloxybenzoic acid (ABA) was synthesized by condensation reaction of acryloyl chloride and p-hydroxybenzoic acid in alkaline medium. Polymerization of the monomer and grafting of the produced polymer (PABA) onto high density polyethylene (HDPE) were expected to be carried simultaneously in melt mixing at high temperature. The graft copolymerization was studied at varying concentrations of the monomer in the reaction mixture at constant temperature (200 0C). Grafted HDPE samples were investigated by several techniques such as DSC, FTIR, MFI and mechanical testing. The tensile tests of PABA-g-HDPE showed an improvement particularly in stress at yield and Young&rsquo / s modulus whereas the strain at break values showed a decrease for all compositions compared to neat HDPE.

1. Investigations of styrene polymerized in wood using ionizing radiation as the chain initiator indicate that property improvements are of the same order as for thermally initiated polymerization. 2. Free radicals have been detected in irradiated cellulose, Dioxane lignin, Spruce Periodate lignin and Beaun’s “Isolated Native Lignin” as well as in wood subjected to radiation. Consequently, wood radical identification is not possible. 3. Analysis of radical concentrations and decay suggest the presence of one or more decaying radical species in irradiated wood. The persistent maximum in radical concentration found corresponds to one or two unique radical sites per molecule; possibly the terminal hydroxyl group. 4. Results suggest that in the grafting reaction the initiation is a direct radical-monomer couple and does not involve decomposing peroxides. / Thesis / Master of Engineering (ME)

Résumé confidentiel / Résumé confidentiel