ICTAC Kinetics Committee recommendations for collecting experimental thermal analysis data for kinetic computations

Analysis of the nonisothermal melt and cold crystallization kinetics of poly(aryl ether ether ketone ketone) (PEEKK) was performed by using differential scanning calorimetry (DSC). The Avrami equation modified by Jeziorny could describe only the primary stage of nonisothermal crystallization of PEEKK. And, the Ozawa analysis, when applied to this polymer system, failed to describe its nonisothermal crystallization behavior. A new and convenient approach for the nonisothermal crystallization was proposed by combining the Avrami equation with the Ozawa equation. By evaluating the kinetic parameters in this approach, the crystallization behavior of PEEKK was analyzed. According to the Kissinger method, the activation energies were determined to be 189 and 328 kJ/mol for nonisothermal melt and cold crystallization, respectively.

Nonisothermal melt and cold crystallization kinetics of poly(aryl ether ether ketone ketone)

Non-isothermal crystallization of polymers

Isoconversional Kinetics of Thermally Stimulated Processes

All-polymer solar cells (all-PSCs) exhibit excellent stability and readily tunable ink viscosity, and are therefore especially suitable for printing preparation of large-scale devices. At present, the efficiency of state-of-the-art all-PSCs fabricated by the spin-coating method has exceeded 11%, laying the foundation for the preparation and practical utilization of printed devices. A high power conversion efficiency (PCE) of 11.76% is achieved based on PTzBI-Si:N2200 all-PSCs processing with 2-methyltetrahydrofuran (MTHF, an environmentally friendly solvent) and preparation of active layers by slot die printing, which is the top efficient for all-PSCs. Conversely, the PCE of devices processed by high-boiling point chlorobenzene is less than 2%. Through the study of film formation kinetics, volatile solvents can freeze the morphology in a short time, and a more rigid conformation with strong intermolecular interaction combined with the solubility limit of PTzBI-Si and N2200 in MTHF results in the formation of a fibril network in the bulk heterojunction. The multilength scaled morphology ensures fast transfer of carriers and facilitates exciton separation, which boosts carrier mobility and current density, thus improving the device performance. These results are of great significance for large-scale printing fabrication of high-efficiency all-PSCs in the future.

Aggregation-Induced Multilength Scaled Morphology Enabling 11.76% Efficiency in All-Polymer Solar Cells Using Printing Fabrication

This paper describes the occurrence of four cases of acute food poisoning, involving a total of 50 people, due to the ingestion of lamb and bovine meat containing residues of clenbuterol. Symptoms shown by the intoxicated people may be generally described as gross tremors of the extremities, tachycardia, nausea, headaches and dizziness. Analytical methodology developed for the determination of clenbuterol in meat, liver and blood samples is described. Procedures are described which should be followed when the described symptoms are evident in a group of people who have ingested contaminated meat, and particularly liver of ruminants.

Food poisoning by clenbuterol in Portugal.

Differential scanning calorimetry (dual furnace, null-balance, DSC) and optical microscopy (OM) have been used to study the isothermal crystallization kinetics of poly(oxymethylene)-POM The non-isothermal crystallization of the same material has also been studied by optical microscopy A very controversial problem is whether the isothermal kinetic parameters may be applied to describe the non-isothermal crystallization The results show that the kinetic spherulite growth parameters obtained by non-isothermal optical microscopy are, within the experimental errors involved, the same as those obtained by isothermal optical microscopy or isothermal DSC The importance of this finding is highlighted

POLYMER CRYSTALLIZATION Isothermal and non-isothermal spherulite growth parameters from optical microscopy and differential scanning calorimetry

Origin of the melt memory effect in polymer crystallization

The isothermal crystallization of two engineering polymers — POM and PEEK — was studied, both theoretically and experimentally. The experiments were performed by means of differential scanning calorimetry (DSC) and polarized light optical microscopy (OM).

The isothermal crystallization of engineering polymers — POM and PEEK

To provide insight into the formation of shear-induced precursor structures, three apparently unrelated subjects are analyzed and discussed: the saturation of crystallization from sheared polymer melts, evaluated with a new shear DTA instrument, the steady state in steady shear, and the entanglement-disentanglement transition. It is shown that the same large strains that saturate crystallization also lead to a reversible steady state in steady shear, where the viscosity of the sheared melt is constant in time, and their magnitude is only determined by the temperature of the sheared melt. Features of the melt morphology at this state are discussed, and their importance is highlighted to understand the possible mechanisms behind the formation of shear-induced precursors. Measurements of the reptation time for unsheared samples, and samples sheared up to the steady state, allowed the quantification of the entanglements loss during the transition between these two states (around 2/3), which is interpreted as an entanglement-disentanglement transition. The relevance of this result on assumptions of flow models, particularly the constant number of topological constraints, convective constraint release process, and chain stretch, is discussed.

J. A. Martins

Papers

Food poisoning by clenbuterol in Portugal.

POLYMER CRYSTALLIZATION Isothermal and non-isothermal spherulite growth parameters from optical microscopy and differential scanning calorimetry

Origin of the melt memory effect in polymer crystallization

The isothermal crystallization of engineering polymers — POM and PEEK

Saturation of Shear-Induced Isothermal Crystallization of Polymers at the Steady State and the Entanglement-Disentanglement Transition