Macromolecular Reaction Engineering最新文献

A rationale for droplet nucleation during inverse emulsion polymerization (IEP) (reported by previous investigators) is proposed. Based on the idea that smaller monomer droplets are nucleated into polymer particles, while larger droplets serve as reservoirs for monomer (as in a micellar nucleation mechanism) the question of possible monomer-transport limitation during polymerization is explored.

Front Cover: The deposition process during emulsion polymerization is classified as particulate and reaction fouling. The deposited material is composed of latex particles and emulsifier with particle size and number depending on the respective equilibrium composition of the fluid phase. The figure shows the deposition of latex particles after a reaction time of 240 minutes. Further details can be found in article 2300057 by Wolfgang Augustin and co-workers.

Front Cover: Polymer reaction engineering (PRE) is a key competence for process scale-up, but the information collected in daily plant operation is not fully exploited. What do catalytic olefin polymerization plants tell us? In article 2300046, by Vasileios Touloupidis and João B. P. Soares, a method to increase catalyst and process know-how, based on experimentally acquired results from a continuous tandem reactor polymerization process is proposed and validated using small-scale experiments.

Mineral–rubber composites based on phosphorylated butadiene rubber (PhBR), including pure expanded perlite (EP) and modified phosphorylated expanded perlite (PhEP) as fillers, are developed. The process involves forming PhBR and its composites—EP/PhBR and PhEP/PhBR—through the oxidative chlorophosphorylation (OxCh) reaction. An in-depth comparative analysis is conducted on the thermal destruction of the PhBR matrix and the EP/PhBR, and PhEP/PhBR composites. The thermogravimetric (TG)/differential thermogravimetry (DTG) analyses reveal three stages of thermal degradation for the PhBR matrix and both composites, highlighting the notable effects of EP and PhEP in the second and third stages of the degradation process. In comparison, the PhEP/PhBR composite exhibits reduced weight loss, the highest integral procedural decomposition temperature (IPDT) value, and a lower T_max on the DTG curve, compared with the EP/PhBR composite and the PhBR matrix. The mechanism of the thermal destruction reaction and the kinetic parameters E_a and A are calculated using the model-fitting Coats–Redfern method.

Transparent and light films with high electrical conductivity are preferred for flexible electronic applications. Here, a film exhibiting high transparency, electrical conductivity, and flexibility is produced using a polyimide (PI) substrate and multiwalled carbon nanotubes (MWCNTs) through spray coating. Cost-effective MWCNTs are used instead of other electrically conductive materials, including silver nanowire ink, single-walled carbon nanotubes (SWCNTs), and other carbon materials. The average sheet resistance of the prepared MWCNT–PI film is 520.2 Ω □⁻¹ (infinite for the bare PI film), which is lower than the sheet resistances of the SWCNT–PI film reported by another group. This can be attributed to the increase in electrical conductivity of the highly transparent PI film due to the use of MWCNTs. The transparency of the MWCNT–PI film is 71.834% at 550 nm. When MWCNTs and PI are combined, MWCNTs protrude from the surface of the PI film, creating networks and increasing electrical conductivity. Atomic force microscopy analysis reveals that MWCNT networks form on the surface of the MWCNT–PI film. This study suggests the possibility that MWCNTs can also be used as carbon materials for flexible and highly transparent films.

In the present work, the catalyst performances of USY and REY zeolites and MgO, ZnO, and Mg_xAlO_y oxides are investigated in the pyrolysis of virgin high-density polyethylene (HDPE) and of post-consumer polyolefin waste. The influence of operation parameters and catalyst deactivation resistance over four reaction cycles are evaluated. The results indicate that basic oxides do not show relevant cracking activity, so that the only identified effect for these catalysts is the production of liquid products with higher contents of paraffins when compared to thermal pyrolysis. Among the evaluated oxides, Mg_xAlO_y is the most active and resistant to deactivation. The zeolites promote cracking and secondary reactions of isomerization, cyclization, and aromatization. Particularly, USY promotes the production of higher-quality oils and shows higher deactivation resistance, when compared to REY. Additionally, a significant loss of catalyst activity is identified in reactions conducted with post-consumer polyolefin wastes. However, increase in rates of coke formation and the presence of contaminants (such as halogens and metals) are not detected in the catalysts after the reactions.