Deconvolution of Mass Spectral Interferences of Chlorinated Alkanes and Their Thermal Degradation Products: Chlorinated Alkenes

Chlorinated paraffins (CPs) are high production volume chemicals and ubiquitous environmental contaminants. CPs are produced and used as complex mixtures of polychlorinated <i>n</i>-alkanes containing thousands of isomers, leading to demanding analytical challenges. Due to their high degree of chlorination, CPs have highly complex isotopic mass patterns that often overlap, even when applying high resolution mass spectrometry. This is further complicated in the presence of degradation products such as chlorinated alkenes (CP-enes). CP-enes are formed by dehydrochlorination of CPs and are expected thermal degradation products in some applications of CPs, for example, as metal working fluids. A mathematical method is presented that allows deconvolution of the strongly interfered measured isotope clusters into linear combinations of isotope clusters of CPs and CP-enes. The analytical method applied was direct liquid injection into an atmospheric pressure chemical ionization source, followed by quadrupole time-of-flight mass spectrometry (APCI-qTOF-MS), operated in full scan negative ion mode. The mathematical deconvolution method was successfully applied to a thermally aged polychlorinated tridecane formulation (Cl₅–Cl₉). Deconvolution of mass patterns allowed quantifying fractions of interfering CPs and CP-enes. After exposure to 220 °C for 2, 4, 8, and 24 h, fractions of CP-enes within the respective interfering clusters increased from 0–3% at 0 h up to 37–44% after 24 h. It was shown that thermolysis of CPs follows first-order kinetics. The presented deconvolution method allows CP degradation studies with mass resolution lower than 20000 and is therefore a good alternative when higher resolution is not available

In Situ P‑Modified Hybrid Silica–Epoxy Nanocomposites via a Green Hydrolytic Sol–Gel Route for Flame-Retardant Applications

Flame retardance of epoxy resins is usually imparted using suitable additives and/or properly modified curing agents. Herein, via a two-step green synthetic procedure, the chemical modification of the epoxy matrix with reactive silicon and phosphorus precursors is explored to obtain nanocomposites with intrinsic flame-retardant features. Nanoscale phase separation occurs in the first step, forming an inverse micelle system in which polar nanodomains act as nanoreactors for the hydrolysis of silanes (Si precursors), giving rise to silica lamellar nanocrystals (SLNCs). In the second step, inside the silica nanodomains, the formation of stable Si–O–P bonds occurs because the reactivity of phosphoric acid (P precursor) with the oxirane rings of the polymer chain is balanced by its tendency to diffuse into polar nanodomains. Intriguingly, the use of phosphoric acid alone in epoxy composite manufacturing leads to a wormlike morphology of the network, whereas its addition in the presence of silanes results in the formation of SLNCs with a thinner interlayer distance. The morphology of the hybrid Si/P–epoxy nanocomposites, comprising organic and inorganic co-continuous phases, can confer, through a prevalent mechanism in the condensed phase, interesting flame-retardant performances, namely, the absence of dripping during vertical burning tests, the formation of a large amount of coherent char after combustion, and a remarkable reduction (up to 27.7%) in the peak of heat release rate. The above characteristics make these nanostructured hybrid materials very promising for the manufacturing of epoxy systems with enhanced fire behavior (e.g., coatings, sealants, matrices for reinforced composites), even containing a low amount of specific flame retardants and thus keeping good viscoelastic properties