ABSTRACT
The migration of chemicals from polyurethane (PUR) is a concern in many applications, such as adhesives for food packaging. Low molecular weight catalysts, which are prone to migration, need to be eliminated from PUR, in particular those containing Sn or other metals. This is difficult partly due to many uncertainties of autocatalytic polyaddition between isocyanates and polyols. Hexamethylene and tolylene diisocyanates, HDI and TDI, are often reacted with macrodiols to produce prepolymers for PUR. This study measures isocyanate contents during the polyaddition of HDI and TDI with excess macrodiols. Ester-based macrodiols were reacted between 60 °C and 90 °C using 1 : 0.3 and 1 : 0.5 molar ratios to form OH-terminated prepolymers. Time-temperature superposition (TTS) was used to process the values of unreacted isocyanate fractions from several temperatures. Presumed activation energies and kinetic data scatter implied that polymerization has a distinct initial phase of conversion of unreacted diisocyanate into monofunctional adducts by addition to macrodiols, followed by more complex processes. Utilization of the activation energy from the initial phase and TTS application might allow the prediction of kinetic trends without the need for a large volume of accurate data. Such kinetic mapping should be useful for developing catalyst-free PUR with low levels of migrating chemicals.
ABSTRACT
Biodiesel plants are struggling to find value added applications for fatty acid methyl esters (FAME). One option for FAME valorization would be dibasic esters, which can be transesterified with 2-ethylhexyl (2EH) or other alcohols to produce lubricant basestocks and achieve the most widespread viscosity grades VG46 and VG32. Biocatalytic, metathesis and other synthetic pathways are available to produce dibasic esters. Using a ruthenium-based catalyst, methyl oleate was converted into monounsaturated dibasic ester by metathesis and reached VG22 after transesterification with 2EH in this investigation. Synthesized 2EH esters of other dibasic acids showed distinct viscometric trends. Their correlation implied that FAME from gondoic and erucic acids should result in VG32 and VG46 respectively, if converted into 2EH dibasic esters. Pour points demonstrated excellent low temperature fluidity and resistance to heat thinning when monounsaturation was retained. Oxidative stability properties remained acceptable, volatility was lower than that of VG46 mineral oils. Mixed alcohols, acids and esters can also be used for meeting VG specifications or achieving higher biobased contents. Currently petrochemical ester basestocks dominate in high performance hydraulic fluids (HF). However, fractionation of FAME into high-erucic/gondoic esters in biodiesel plants can produce a valuable biobased feedstock for large volume manufacture of HF and other lubricants.
ABSTRACT
Quality control and non-destructive monitoring are of notable interest of food and pharmaceutical industries. It relies on the ability of non-invasive inspection which can be employed for manufacturing process control. We hereby apply terahertz (THz) time-domain spectroscopy as non-destructive technique to monitor pure and degraded oils as well as hydrocarbon chemicals. Significant differences in the spectra of refractive index (RI) and absorption coefficient arising from the presence of ester linkages in the edible and technical oils were obtained. Explicit increase from 1.38 to 1.5 of the RI in all THz spectrum range was observed in hydrocarbons and mono-functional esters with the increase of molar mass. This fact is in contrast of RI dependence on molar mass in multi-functional esters, such as Adipate or vegetable oils, where it is around 1.54. Degradation products, Oleic Acid (OA) and water in particular, lead only to some changes in absorption coefficient and RI spectra of vegetable oils. We demonstrate that complex colloidal and supramolecular processes, such as dynamics of inverse micelles and oil hydrolysis, take part during oil degradation and are responsible for non-uniform dependence of optical properties on extent of degradation.
