Józef Garbarczyk

Polymorphism of isotactic polypropylene in presence of additives, in blends and in composites

This article is an overview of our investigations of polymorphism in isotactic polypropylene. We suggest the reason for the formation of different forms is perturbations in the mobility of the chains during crystallization. In this work, we try to prove this hypothesis considering the influence of the presence of small organic compounds or external forces, like an electric field, on the process of crystallization. We also analyzed the formation of the polymorphic forms in polypropylene blends and in composites with natural fibers. It was found that in the composites with natural fibers the hexagonal form arises when the fibers are in motion in relation to the polymeric matrix.

Structure of polypropylene/polycarbonate blends crystallized under pressure☆

Abstract An analysis has been carried out of the crystalline structure of a blend consisting of amorphous polycarbonate and semicrystalline isotactic polypropylene (PP) crystallized under pressure. Structure investigations were carried out by means of wide-angle X-ray scattering. The amount of particular phases as well as the degree of crystallinity have been analysed. It was found that during pressure crystallization, as well as the monoclinic α-modification, the triclinic γ-form of PP also occurs, which disappears after recrystallization in non-pressure conditions. The crystallinity of PP in the blends is independent of the composition of the polymeric mixture.

Influence of the pulling of embedded natural fibers on the crystal structure of polypropylene matrix

The formation of hexagonal modification (β) of isotactic polypropylene (iPP) matrix, induced by motion of embedded natural fibers (NF) has been investigated by WAXS method. Untreated and chemically modified flax as well as hemp fibers were used as NF. The motion temperature of NF was found to strongly influence the content of hexagonal modification. If the temperature of motion of NF is lower, then the amount of β-iPP significantly increases. The content of β-iPP also depends on the rate of motion of NF; however, the chemical modification of NF surface reduces the content of this form.

The Flame Retardant for Polypropylene using Magnesium Hydroxide with Intumescent Components

Abstract In this work we present results of our study on flammability of polypropylene samples containing various fire retardants. Moreover, the influence of the flame retardants added to PP on the structure of polypropylene matrix was investigated. The effect of magnesium hydroxide on thermal properties of isotactic polypropylene was measured on a cone calorimeter. The measurements were performed in air at heat flux of 50kW/m2. Melamine polyphosphate, when added to MagShield-PP system, shows the highest fire-retarding effect compared to other intumescent compounds studied, such as pentaerythritol, urea polyphosphate and zinc borate. The weakest effect was recorded for zinc borate-containing composite. Results of the structural study allow to conclude that fire retardants based on magnesium compounds in practice do not change the crystalline structure of isotactic polypropylene. The intumescent fire retardants act as nucleants of hexagonal form of isotactic polypropylene.

Crystal structure and conformational analysis of 2-thioamide derivatives of thiazole

Abstract Molecular and crystal structures of two thioamide derivatives of thiazole were analysed based on X-ray diffraction data and results obtained from quantum chemistry (QC) and molecular mechanics (MM) calculations. It was found that within the thiazole rings, the S1–C2 bond appeared to be more affected by the action of two-substituents rather than the C2–N3 bonds. The ab initio calculations showed that the C2–C6 bond connecting the thioamide group with thiazole is shortened when both the systems are coplanar, but a conjugation is relatively weak and does not enforce such conformation. The QC and MM calculations indicated that the particular parts of the thioamide group may exist in two conformations. However, relatively high energy barrier excluded the possibility of change of one conformation into the other by simple rotation around the C2–C6 or C6–N8 bonds. Moreover, the MM calculations explained that steric hindrance is not the main reason of energy barrier for suggested rotations. The observed cis – trans conformation is stabilised by intramolecular hydrogen bonds.

Molecular structure of 4,4′-sulfandiyl-bis-thiophenol from electron diffraction

Abstract The molecular structure of 4,4′-sulfanidyl-bis-thiophenol (C 12 H 10 S 3 ) has been determined by gas electron diffraction. Assuming identical geometry and D 2h local symmetry for SC 6 H 4 S moieties, the following bond lengths ( r g ) and bond angles were obtained: CH = 1.101 ± 0.005, SH = 1.388 ± 0.019, (CC) mean = 1.400 ± 0.003, (SC) mean = 1.778 ± 0.004 A, C ar SC ar = 103.5 ± 1.3, CC(S)C = 120.4 ± 0.3, C(H)C(H)H = 119.1 ± 0.9 and CSH = 94.6 ± 3.1°. Two ratational forms were found to reproduce the experimental data, characterized by dihedral angles of the benzene rings with respect to the C ar SC ar plane; ϕ 1 = 67.8 ± 2.0°, ϕ 2 = 4.5 ± 7.2°, and ϕ 1 = 69.4 ± 2.0δ, ϕ 2 = −26.6 ± 7.1°. Identical signs of ϕ 1 and ϕ 2 indicate that the two benzene rings are rotated in the same direction about the respective S central C axes.

Structures of blends of poly (p-phenylene sulfide) (PPS) with poly(p-phenylene sulfide ether) (PPSE)

The blends named in the title were investigated by wide-angle X-ray scattering (WAXS). Given relative chemical similarity of the blend components, formation of a homogeneous blend and co-crystallization were distinct possibilities. The results are compatible with the assumption of orthorhombic structure in PPSE, with the same reflex indices as in PPS. Parameters of the unit cell of PPSE computed on that basis are: a = 0.837, b = 0.559 and c = 1.034 nm. The degree of crystallinity of PPS is approximately 10% lower than that of PPSE. In blends separate crystals of the two components appear to be formed; the crystallinity of a given component seems to be neither enhanced nor diminished by the presence of the other component.

Refinement of molecular and crystal structure of poly-(p-phenylene sulphide ether)

The structure of crystal phase of untreated newly synthesized poly-(p-phenylene sulphide ether) (PPSE) was analyzed by means WAXS method and computer modeling. It was shown that PPSE has crystal structure similar to the PPS.

Natural fibers/polypropylene composite: processing and preliminary structural investigations

Biodegradation and physico-mechanical properties allow us to predict a wide application of cellulosic/thermoplastic composites and it is an essential motive for investigations on structure-properties relationship. The preliminary investigations on the structure of composites containing isotactic polypropylene with hemp or flax are presented.