A Theoretical and Experimental Study for Screening Inhibitors for Styrene Polymerization

Inhibition of Free Radical Polymerization: A Review

Polymerization reactions have caused several severe accidents in the past since they are prone to runaways due to their highly exothermic and auto-accelerating nature. The heat generated during these uncontrolled runaway reactions surpasses the heat removal capacity of the cooling system leading to the auto-acceleration of the reactions. If proper measures are not taken to attenuate this auto-accelerative nature, dangerous consequences ensue, such as rampant boiling of the reaction system fluids or vapor production from secondary reactions. Both these consequences may eventually lead to over-pressurization followed by a thermal explosion. Thus, to eliminate the associated risk, polymerization reactions in industries are carried out in the presence of inhibitors which are injected into the reaction system before the initiation of polymerization. In this review, I have summarized various accidents that have happened in the past due to runaway polymerization implicating that there is an urgent necessity to do further research in this relatively less explored field of polymerization inhibition. To this end, I have completed an exhaustive survey of the various types of inhibitors used in industries and their inhibition mechanisms focusing mainly on the auto-initiated polymerization of styrene, methyl methacrylate, and acrylic acid monomer. Lastly, the synergism in the inhibition performance of a mixture of two types of inhibitors was also compared and discussed in detail.

Treatment of Scrap Tire for Rubber and Carbon Black Recovery

In this study, a chemical dissolution treatment was used to recover rubber and carbon black (CB) from truck tire scrap, with gas oil acting as the solvent and 4-Hydroxy-TEMPO acting as the catalyst for the chemical reactions. Montmorillonite clay was used to separate the rubber solution from the CB and the other non-dissolved tire additives. The recovered rubber and CB were characterized together with the original scrap tire sample by XRD, SEM, BET and thermal analysis, as well as FTIR and 1H NMR spectral analyses. Characterization of the chemical structure of the recovered rubber showed that the main functional groups of styrene−butadiene rubber blend with natural rubber. The thermal behavior and crystalline structure of the recovered rubber, as well as its morphological images, showed that the properties of the rubber sample were acceptable and similar to natural rubber. The recovered CB characterizations showed that the sample after pyrolysis was a highly crystalline nanocomposite structure with a high specific surface area and scattered pores.

Silver-Catalyzed, N-Formylation of Amines Using Glycol Ethers

A silver-catalyzed protocol was found to afford the N-formylation of amines in moderate-to-good yields. Ethylene glycol-derived, oligomeric ethers were found to function as the formylating agent, with 1,4-dioxane affording the best results. This reaction does not require the use of stoichiometric activating reagents, and avoids the use of explosive reagents or toxic gases, such as CO, as the C1 synthon. Mechanistic studies indicate a single-electron transfer-based pathway. This work highlights the ability of silver to participate in unexpected reaction pathways.

Special Issue on “Computational Methods for Polymers”

Polymers play a key role in our daily lives [...]