Authors:A. Aboulkas, K. El Harfi, A. El Bouadili, M. Chanâa, and A. Mokhlisse
The pyrolysis of oil shale and plastic wastes is being presently considered as an alternative means of partial substitution
of fossil fuels to generate the necessary energy to supply the increasing energy demand and as well as new technology to reduce
the negative environment of plastic wastes. However, Knowledge of pyrolysis kinetics is of great imponrtance for the design
and simulation of the reactor and in order to establish the optimum process conditions.
In this study, the thermal decomposition of polypropylene, oil shale and their mixture was studied by TG under a nitrogen
atmosphere. Experiments were carried out for various heating rates (2, 10, 20, 50 K min−1) in the temperature range 300–1273 K. The values of the obtained activation energies are 207 kJ mol−1 for polyethylene, 57 kJ mol−1 for the organic matter contained in the oil shale and 174 kJ mol−1 for the mixture. The results indicate that the decomposition of these materials depends on the heating rate, and that polypropylene
acts as catalyst in the degradation of the oil shale in the mixture.
The effects of nucleating agents such as dibenzylidene sorbitol (DBS) (a derivative of sorbitol), pine crystal 1500, sodium and potassium benzoates in commercial grade isotactic polypropylene iPP are studied using differential scanning calorimetry (DSC). Isothermal crystallization kinetics of polypropylene to the alpha phase have been analyzed using Avrami's model. Results indicate that dibenzylidene sorbitol and pine crystal are very effective in increasing the crystallization temperature of the polymer and number of nuclei formed during crystallization.
Authors:B. Osowiecka, A. Bukowski, J. Zieliński, W. Ciesińska, and T. Zieliński
In the following essay the results of the research on nucleation of polypropylene obtained in PKN Orlen SA were presented.
Both, organic (Millad 3988, ADK NA21) and non-organic (talc) mediums were used in the process. The main aim of the examination
was to measure the influence of the above-mentioned mediums on the structure and physicochemical features of polypropylene.
It has been proved that the organic nucleation mediums are more efficient as not only did polypropylene become more transparent,
its structure more homogenous but his melting temperature increased as well. All those changes demonstrate that the nucleation
process has taken place. The favourable changes in the polymer macrostructure were enabled by the process of nucleate molecules
in the process heteronucleation.
Authors:R. Bouza, C. Marco, G. Ellis, Z. Martín, M. Gómez, and L. Barral
Isothermal crystallization and melting of isotactic polypropylene in binary polypropylene-wood flour composites has been studied
by DSC, and the influence of an ethylene-methacrylic acid copolymer interfacial agent analyzed. Wood flour induces a slight
nucleating effect, reducing the basal interfacial free energy of nucleation and increasing the overall crystallization rate.
The interfacial agent generates a compatibilization phenomenon and an increase in the basal interfacial free energies with
respect to the binary composites. In both binary and ternary systems the melting behaviour is a function of undercooling and
is unaltered by the presence of either wood flour or the interfacial agent.
In the present paper the effect of the thermoexfoliated graphite (EG) content (0–0.310 parts by volume), constituent mixing
conditions (a paddle mixer or a disk-and-screw extruder), annealing and aging on thermodestruction processes of polypropylene
(PP)/exfoliated graphite composite materials (CM) by means differential thermal analysis and the thermogravimetric method
have been investigated. The studies have shown that thermodestruction processes in CM based on PP and EG ran in air for expense
of PP thermodestruction. The characteristics of thermodestruction in CM essentially depend on a regime of making and concentration
of components. It is established that processes leading to the formation of less perfect crystalline structures or causing
amorphization of PP (including formation of continuous space structures from EG particles, cluster traps) advances thermodestruction.
The increase in crystallinity extent of PP favors to the decrease in thermodestruction processes.
Authors:D. Zhang, G. Bhat, S. Malkan, and L. Wadsworth
Polypropylene homopolymer (PP) and a copolymer (P/E) were processed using the Reicofil® spunbonding line at the Textiles and
Nonwovens Development Center of the University of Tennessee, Knoxville. The properties of the filament samples taken before
thermal-bonding were determined through a variety of techniques such as differential scanning calorimetry, thermomechanical
analysis, thermal deformation analysis and mechanical properties. The two process variables investigated, primary air temperature
and throughput had a strong influence on the structure and properties of both the filaments and the bonded nonwovens. As the
primary air temperature and throughput decreased, there was a tendency for decrease in filament diameter with a simultaneous
increase in their crystallinity, birefringence and thermal stability. The copolymer filaments showed lower crystallinity and
orientation for all the corresponding processing conditions.
Authors:V. Causin, Carla Marega, Roberta Saini, A. Marigo, and G. Ferrara
The effect of clay dispersion on the crystallization behavior of isotactic polypropylene (iPP)-based nanocomposites is reported.
The Tm0 of the materials was calculated by the method proposed by Marand, the kinetics of crystallization was evaluated by the Avrami
analysis and also the Hoffman-Lauritzen theory of crystallization regimes was applied. Montmorillonite was found to depress
Tm0, to enhance the rate of crystallization and to ease the chain folding of macromolecules. These effects were magnified if
clay was exfoliated, rather than intercalated.
made from an isotactic polypropylene matrix and wood (pine or beech) have
been prepared and tested. To improve adhesion between components, the wood
modification was performed by esterification with maleic, propionic, crotonic,
succinic and phthalic anhydrides. The surface of wood fillers was also modified
by chemical treatment with NaOH as well as by extraction process. Non-isothermal
crystallisation of polypropylene in wood composites is studied by DSC, and
the basic parameters of crystallisation are determined. We discovered that
the composites containing chemical treated wood fillers showed the tendency
reduction the nucleation efficiency of polypropylene. The ability of wood
filler to induce nucleation in polypropylene matrix is dependent on the kind
of chemical modification of surface wood
The thermal stability of a polypropylene copolymer has been examined at several stages during the processing of the material
into its final product in order to obtain information on the influence of processing steps such as grinding and thermal heating
on the expected lifetime of the material. Mass loss kinetics in an inert atmosphere were able to detect differences in thermal
stability, but oxidative differential scanning calorimetry studies proved to be a more sensitive techiique. A comparative
study of a specially prepared series of samples revealed the importance of additives on measured thermal stability and indicated
that both mechanical and thermal processing can cause reduction in measured thermal stability.
Authors:S. Reyes-de Vaaben, A. Aguilar, F. Avalos, and L. Ramos-de Valle
The effect of four nucleating agents on the crystallization of isotactic polypropylene (iPP) was studied by differential scanning
calorimetry (DSC) under isothermal and non-isothermal conditions. The nucleating agents are: carbon nanofibers (CNF), carbon
nanotubes (CNT), lithium benzoate and dimethyl-benzylidene sorbitol.
Avramișs model is used to analyze the isothermal crystallization kinetics of iPP.
Based on the increase in crystallization temperature (Tc) and the decrease in half-life time (τ½) for crystallization, the most efficient nucleating agents are the CNF and CNT, at concentrations as low as 0.001 mass%.
Sorbitol and lithium benzoate show to be less efficient, while the sorbitol needs to be present at concentrations above 0.05
mass% to even act as nucleating agent.