High-pressure catalytic and thermal cracking of polyethylene

The thermal cracking and catalytic cracking processes of low-density polyethylene were studied in a closed autoclave. The compositions of gaseous and liquid products were analysed by means of GC/FID and GS/MS chromatographic methods. The fractional composition of liquid products was found by distillation. Increased temperature of PE depolymerisation process increases the production of gaseous products and low-boiling liquid compounds; more aromatic hydrocarbons are formed instead of alkenes. When a lower temperature and longer time are adopted for the process to reach the assumed conversion, more straight chained hydrocarbons are produced. The acidic aluminosilicate catalyst yields more low-boiling liquid fractions, more isoalkanes and more aromatics. The neutral alumina is favourable for the production of alkenes and vacuum gas oil fraction in comparison to a non-catalytic process. The Ni–Mo/Al₂O₃ catalyst is efficient in hydrogenation of depolymerisation products. The reaction products contain only saturated compounds then and no aromatics are formed.     

Calcium Phosphate Materials Prepared from Precipitates with Various Calcium:Phosphorus Molar Ratios

Depending on the calcium:phosphorus molar ratio of the initial precipitates determined by precipitation conditions (calcium:phosphorus molar ratio of reactants and pH of reaction environment), after sintering at 1250°C, monophase, biphase, or triphase ceramics consisting of hydroxyapatite, β-tricalcium phosphate, α-tricalcium phosphate, and calcium oxide were obtained. The phase composition and properties—i.e., density, shrinkage, hardness, bending strength, and roughness—of the fractured surfaces of the isostatically re-pressed sinters were determined.     

Microstructure study of poly(isobutyl acrylate) and poly(<Emphasis Type="Italic">sec</Emphasis>-butyl acrylate) by incremental analysis of <Superscript>13</Superscript>C NMR spectra

Microstructure of poly(isobutyl acrylate) (PiBuA) and poly(sec-butyl acrylate) (PsBuA), prepared by free radical and anionic polymerization, was investigated by ¹³C NMR spectroscopy. The carbonyl signal in the 100 MHz ¹³C NMR spectra of both homopolymers provided sufficient resolution to perform detailed analysis of distribution of configurational sequences at the pentad/heptad level. Application of Bernoulli and first order Markov statistics to determine probabilities of configurational sequences and incremental calculation to estimate chemical shifts of the individual sequences allowed for positive simulation of carbonyl signals.     

Variances of Plane Parameters Fitted to Range Data

Formulas for variances of plane parameters fitted with Nonlinear Least Squares to point clouds acquired by 3D imaging systems (e.g., LADAR) are derived. Two different error objective functions used in minimization are discussed: the orthogonal and the directional functions. Comparisons of corresponding formulas suggest the two functions can yield different results when applied to the same dataset.     

Nanoindentation of WC–Co hardmetals

WC–Co cemented carbide has been investigated using instrumented indentation with maximum applied loads from 0.1 to 10 mN. The hardness and indentation modulus of individual phases and the influence of crystallographic orientation of WC on the hardness and indentation modulus have been studied. The hardness of the Co binder was approximately 10 GPa and that of WC grains up to 50 GPa with relatively large scatter under the indentation load of 1 mN. Investigation of the role of crystallographic orientation of WC grains on hardness at 10 mN load revealed average values of H_ITbasal = 40.4 GPa (E_ITbasal = 674 GPa) and H_ITprismatic = 32.8 GPa (E_Itprismatic = 542 GPa), respectively. The scatter in the measured values at low indentation loads is caused by the effects of surface and sub-surface characteristics (residual stress, damaged region) and at higher loads by “mix-phase” volume below the indenter.