Practical approach to thermally stimulated discharge (TSD) method on polymers

The paper deals with the thermally stimulated discharge current (TSD or TSDC) method; exclusively with the short circuited one. Because of its low effective frequency, TSD has excellent resolving power. Problems both of measurement and of the evaluation are analyzed. The effects of experimental circumstances and theoretical considerations are demonstrated by results on different polymers and model calculations as well. In order to get reliable results, the sample preparation must be performed carefully. It is particularly valid in case of solution cast samples. The depolarization curve of a real polymer is always complex, consisting of superimposed relaxation processes. This fact causes unexpected problems in the evaluation. Heating rate slightly affects the peak separation; however, high heating rate might produce thermal inhomogeneity in the sample.     

Combined thermal analysis of fluid plasticizers

Journal of Thermal Analysis and Calorimetry - The paper deals with the study of plasticizers using different thermal methods. The literature data on the melting points of plasticizers proved...     

Thermal analysis of polyurethane elastomers matrix with different chain extender contents for thermal conductive application

Polyurethane elastomers (PUR) based on polypropylene glycol and 4,4′-diphenylmethane diisocyanate were prepared with various monoethylene glycol (mEG) contents. The aim of this study is to find a reliable polymer matrix for composites of improved thermal conductivity and testing fully in order to collect knowledge about its structure. Thermal conductivity was improved from 0.255 to 0.329 W m^?1 K^?1 when increasing chain extender content. This attributed to a high appearance crystalline ordering level when adding high mEG content. Differential scanning calorimetry revealed a low transition temperature of soft segment at the same temperature around ??64 °C, due to constant polyol content. The enthalpy of melting increases with increasing mEG content. This is due to the increasing crystalline phase and hard segment phase separation within the PUR structure. Dynamic mechanical analysis results show the glass transition temperature of soft segment in the same temperature range between ??57 and ??52 °C and intensity peak of tanδ tends to decrease when mEG content was increased. On the other hand, the glass transition temperature of hard segment tends to increase from 10 to 93 °C and has high intensity peak of tanδ with increasing mEG content. Increasing the chain extender content can be enhancing the hard segment length in PUR structure and affecting both soft segment motion and hard segment motion. Increasing hard segment length might be obstructing soft segment motion and influence hard segment motion which is hard to move at low temperatures. Phase separation of soft and hard segment clearly observed using the DMA technique.