Carla Marega

Forensic differentiation of paper by X-ray diffraction and infrared spectroscopy

The possibility to discriminate between sheets of paper can be of considerable importance in questioned document examinations. 19 similar types of office paper were characterized by infrared spectroscopy and X-ray diffraction to individuate the most discriminating features that could be measured by these techniques. The discriminating value associated to them was also assessed. By using a sequence of these two techniques, all the samples could be differentiated.

Small-angle X-ray scattering from high-density polyethylene: lamellar thickness distributions

Abstract Small-angle X-ray diffraction patterns were recorded for a number of high-density polyethylene samples and were successively analysed by a fit with the calculated patterns corresponding to certain theoretical models. The parameters determined by the above fits were as follows: long-period, crystallinity, mean dimensions of the crystalline lamellae, amorphous thickness, crystallinity and lamellar dimension distributions. Regarding the latter, two mathematical functions were used for the fits, i.e. a symmetrical and an asymmetrical type, and for all of the samples examined the function was determined which gives the best results. Finally, a correlation is suggested between the polymer molecular weight and lamellar dimension distributions.

The Discrimination Potential of Ultraviolet‐Visible Spectrophotometry, Thin Layer Chromatography, and Fourier Transform Infrared Spectroscopy for the Forensic Analysis of Black and Blue Ballpoint Inks

Abstract:  The knowledge of the discriminating power of analytical techniques used for the differentiation of writing inks can be useful when interpreting results. Ultraviolet‐visible (UV‐VIS) spectrophotometry, thin layer chromatography (TLC), and diffuse reflectance Fourier transform infrared spectroscopy (FT‐IR) were used to examine a population of 21 black and 12 blue ballpoint writing inks. Based on corroborative results of these methods, the discrimination power for UV‐VIS, TLC, and FT‐IR was determined to be 100% and 98% for the black and blue inks, respectively. Generally, TLC and UV‐VIS can be used to differentiate the colorant components (i.e., dyes and some pigments) found in inks. As FT‐IR can be utilized to identify some of the noncolorant components, it was determined to be an excellent complementary technique that can be implemented into an analytical scheme for ink analysis.

Phase transition II → I in isotactic poly-1-butene: wide- and small-angle X-ray scattering measurements

Phase transition II → I in isotactic poly-1-butene was studied by wide- and small-angle X-ray scattering in order to follow the change of crystallinity and of the characteristic parameters of the lamellar stacks over time. Small-angle X-ray scattering experimental patterns were analyzed by a fitting method with the profiles calculated from some theoretical distribution models of the lamellar thickness. The mathematical evaluation of small-angle X-ray scattering patterns provided crystallinity values which were compared with those obtained by wide-angle X-ray scattering, in order to obtain information on the lamellar stacks organization. The transition nucleation seems to be localized on lamellar distortion points and the transition itself involves the rearrangement of lamellae and of lamellar stacks.

Structure-property relationship in polyethylene reinforced by polyethylene-grafted multi-walled carbon nanotubes.

Polyethylene-grafted multiwalled carbon nanotubes (PE-g-MWNT) were used to reinforce polyethylene (PE). The nanocomposites possessed not only improved stiffness and strength, but also increased ductility and toughness. The effects on the structure and morphology of composites due to pristine multiwalled carbon nanotubes (MWNT) and PE-g-MWNT were studied and compared using small angle X-ray scattering (SAXS), wide angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). The SAXS long period, crystalline layer thickness and crystallinity of polymer lamellar stacks were found to decrease significantly in MWNT composites, while the decreases were much smaller in PE-g-MWNT composites. PE-g-MWNT allowed a more efficient and unhindered crystallization at a lamellar level, while MWNT disrupted the order of lamellar stacks, probably because of their tendency to aggregate. The SAXS crystallinity and the mechanical properties of the composites showed similar trends as a function of MWNT content. This suggested that the improvement of the interfacial strength between polymer and carbon nanotubes was a result of synergistic effects of better dispersion of the filler, better stress transfer, due to the grafting of polymer and MWNT, and the nucleation of a crystalline phase around MWNT. The latter effect was confirmed by measurements of kinetics of non-isothermal crystallization.

Synthesis methods of fluorinated polyurethanes. 2. Effects on morphology and microstructure

Abstract A series of fluorinated polyurethanes, characterized by a segmented structure containing hard segments based on 4,4′-methylenebis(phenylisocyanate) (MDI) and 1,4-butandiol (BDO), were analyzed by small- and wide-angle X-ray scattering and transmission electron microscopy (TEM) in order to study the influence of the synthesis and of the soft and hard segments length on the structure. Theoretical models of lamellar morphology were used to fit calculated small-angle scattering patterns to the experimental ones. TEM and small-angle X-ray scattering analysis shows that these polymers are characterized by a heterogeneous structure, not only at the molecular level, but also at a macroscopic scale.

Small- and wide-angle X-ray scattering analysis of Ziegler–Natta catalysts: structural disorder, surface area and activity

Abstract An analysis was carried out of some Ziegler–Natta catalysts precursors by small- and wide-angle X-ray scattering in order to get information on the crystallites dimensions, structural disorder and surface areas. The results were correlated with catalytic activities in polymerization of propylene. It was shown that the structural variations, which mainly influence the catalytic activity, are associated with the rotational disorder of the Cl–Mg–Cl triple layers and that the crystallites dimensions and surface areas play a determinant role in the same activity. Furthermore it was shown that the surface areas of the examined samples, determined by BET, are less meaningful than the data obtained by small-angle X-ray scattering, probably for the presence of intra-particle closed pores and/or microporosity.

Influence of regioirregular structural units on the crystallization of isotactic polypropylene

Seven samples of isotactic polypropylene were examined to study the influence on the formation of the y crystalline phase of possible regiodefects along the chain. Wide-angle X-ray diffraction allowed the determination of the percentage of the γ phase in the samples and 13 C-NMR spectroscopy was used to correlate the development of the y phase with the existence of regioirregular structural units along the chain. Furthermore, it was possible to appraise the contributions given by the different families of lamellae to the small-angle X-ray diffraction patterns.

Synthesis and crystal structure of the MgCl2(CH3COOC2H5)2·(CH3COOC2H5) adduct

The reaction of α-MgCl2 with boiling ethyl acetate affords MgCI2(CH3COOC2H5)2·(CH3COOC2H5), which is obtained as crystals suitable for X-ray analysis only from the mother liquor. M=315.5, orthorhombic, space group P21221 (No. 18), a=25.077(3), b=8.616(1), c=7.345(1) A, V=1587.0(3) A3, Z=4, Dx=1.32 g cm−3,λ A(Mo Kα)=0.71069 A, μ=4.17 cm−1, F(000)=664, T=298 K, observed reflections: 1667, R=0.059 and Rw=0.069. The structure is composed of polymeric chains of MgCl2(CH3COOC2H5)2 and the ethyl acetate molecules occupy a mutually trans position.

Preparation, characterization and properties of some lanthanide oxides

Abstract The formation of oxides of the types Ln2O3 and Ln1Ln2O3 is reported. They have been obtained by thermal decomposition of homo- and heterodinuclear complexes of the type Ln2(L)(NO3)4·xH2O or Ln1Ln2(L)(NO3)4·xH2O where H2L is the macrocycle obtained by condensation of 2,6-diformyl-4- chlorophenol and 1,8-diamino-3,6-dioxaoctane. The composition and properties of the oxides, particularly of DyEuO3 and DyNdO3, have been studied by means of X-ray powder diffraction, electron microscopy and X-ray fluorescence techniques together with magnetic investigations. The products obtained have been compared with those prepared by thermal decomposition of the appropriate Ln(NO3)3·xH2O or, where available, with the commercial oxides. The polymorphism of the oxides has been also investigated.