Search

Poly(methy methacrylate) (PMMA)-SiO2 nanoparticles were prepared via differential microemulsion polymerization. The effects of silica loading, surfactant concentration, and initiator concentration on monomer conversion, particle size, particle size distribution, grafting efficiency, and silica encapsulation efficiency were investigated. A high monomer conversion of 99.9% and PMMA-SiO2 nanoparticles with a size range of 30 to 50 nm were obtained at a low surfactant concentration of 5.34 wt% based on monomer. PMMA-SiO2 nanoparticles showed spherical particles with a core-shell morphology by TEM micrographs. A nanocomposite membrane from natural rubber (NR) and PMMA-SiO2 emulsion was studied for mechanical and thermal properties and pervaporation of water-ethanol mixtures. PMMA-SiO2 nanoparticles which were uniformly dispersed in NR matrix, significantly enhanced mechanical properties and showed high water selectivity in permeate flux. Thus, the NR/PMMA-SiO2 hybrid membranes have great potential for pervaporation process in membrane applications. POLYM. ENG. SCI., 2017. © 2017 Society of Plastics Engineers

Polystyrene-silica (PS-co-RAFT-SiO2) nanoparticles were synthesized via reversible addition-fragmentation chain-transfer (RAFT) emulsifier-free emulsion polymerization using poly (styrenesulfonate-sodium)-RAFT agent (macro-RAFT agent). The effects of macro-RAFT agent to initiator ratio on monomer conversion, particle size, particle size distribution, grafting efficiency and silica encapsulation efficiency were investigated. The particle size decreased with increasing macro-RAFT agent to initiator ratio ([R]:[I]). The PS-co-RAFT-SiO2 nanoparticles exhibited a size range of 23–56 nm with a narrow size distribution for all polymerizations, ⩾99% monomer conversion was achieved. The PS-co-RAFT-SiO2 nanoparticles showed spherical particles with a core-shell morphology as confirmed by TEM photographs. The PS-co-RAFT-SiO2 nanocomposite could be used as filler in natural rubber. Accordingly, NR/PS-R-SiO2 blends had improved thermal and mechanical properties, and also exhibited good oil swelling resistance.

Poly(methyl methacrylate) (PMMA)-graphene emulsion was prepared via reversible addition-fragmentation chain-transfer (RAFT) polymerization using a hydrophilic macro-RAFT agent. In addition, the graphene was prepared using waste graphite from a metal smelting industry to reduce the cost of polymer composites and be more eco-friendly. The graphene oxide (GO) was synthesized via the Hummers method and the modified Hummers method (without using sodium nitrate) and then modified to reduced (r)GO using L-ascorbic acid as the reducing agent. Transmission electron microscopy and zeta potential analyses revealed the PMMA attached to the graphene surface with a good stability. Moreover, the PMMA-graphene composites as the fillers in natural rubber latex could improve the mechanical properties and electrical conductivity of the composite films.

The structural properties and catalytic functionality of two different morphologies of unsupported MoS 2 catalysts were investigated systematically. Hydrodeoxygenation (HDO) of phenol was used as the model reaction to examine the effect of the catalyst structure on the hydrogenolysis and hydrogenation activity and selectivity. The unsupported MoS 2 , with amorphous and highly bent multi-layer structures, was much more active than the highly crystalline structured MoS 2 and resulted in direct oxygen elimination. Co promoter showed a strong effect on the activity and selectivity of Mo sulfides. Temperature programmed reduction (TPR) exhibited the close interaction between Co and Mo in the bimetallic sulfide catalysts resulting in shift of TPR peaks to lower temperatures. The addition of promoter also affected the textural properties of amorphous Mo sulfide by decreasing the surface area, changing the pore characteristics and shifting the pore-size distribution towards smaller sizes. The growth of MoS 2 crystallized particles was inhibited when Co was incorporated. The enhanced catalytic activity observed with the promoter addition was essentially due to the enhancement of the rate of direct-deoxygenation route. The present study indicated that the activity and selectivity for phenol HDO can be controlled by tailoring the morphology and the promoter of the unsupported MoS 2 catalysts.

Unsupported sulfide catalysts are a potentially promising approach towards furthering the understanding and development of a better heterogeneous catalytic system capable of performing the hydrodeoxygenation (HDO) of bio-oil proficiently under mild and short reaction conditions and times, respectively. Amorphous unsupported Ni–Mo sulfide, prepared from ammonium tetrathiomolybdate (ATTM) by a one step hydrothermal method, is already sulfided and so does not need a sulfidation step. The addition of the Ni promoter prevents the growth of Mo sulfide particles and causes a reduction in the surface area and a change in the pore characteristics as the amount of added Ni was increased. Ni sulfide alone (no Mo) showed a completely different morphology and properties compared to those of the Mo-containing sulfides, with or without the copresence of Ni. The activity and selectivity of catalysts was investigated using phenol as a model substrate in the direct-deoxygenation (DDO) and hydrogenation (HYD) reactions in a HDO system. The Ni–Mo sulfide catalyst with optimal Ni amount had a significantly higher phenol conversion efficiency (96.2 mol%), and favored a HYD pathway, than that seen for the Mo sulfide one (71.0 mol%) that favored a DDO pathway. H2-temperature programmed desorption (TPD) suggested that this synergy was mainly derived from a change in the quality and not the number of the active sites. The synergetic effect was a function of the stoichiometric composition with the maximum synergetic effect being obtained at a Ni/(Mo + Ni) ratio of 0.3. This could result from the high dispersion of the active species and the generation of a more active Ni–Mo–S phase.