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

Abstract

Polyurethane elastomers (PUR) based on polypropylene glycol and 4,4 0-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 tand 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 tand 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.

Synthesis of cross-linked polyurethane elastomers with the inclusion of polar-aromatic moieties (BA, PNBA and 3, 5-DNBA): Electrical and thermo-mechanical properties analysis

“…The main feature of the smaller areas of low-temperature maximum location on tan δ curve is that it is related to the better phase separation of PU soft and hard segment also hard phase incorporation in the glass transition is less. The magnitude of tan δ across the application temperature is defined as the ratio of heat energy absorbed by the sample to energy returns as the sample movement [48].…”

“…For measurements, the sample is placed on the sensor at room temperature and a small amount of heat generated by applying a current of known amplitude to a heating element (spiral) of the sensor is applied. The thermophysical characteristics are inversely proportional to the rate at which the sensor voltage increases [48]. Figure 8 shows the variation of thermal conductivity of pure and BA, PNBA, and DNBA doped PUE with different doping contents.…”

Thermal properties of polyurethane-based composites modified with chitosan for biomedical applications

“…The characteristic feature of PU is a segmental structure comprised of hard and soft segments. The hard segments are built from diisocyanates and short chain extenders, whereas soft segments are derived from polyols [4,5]. Another interesting feature is the microphase separation of hard and soft segments that significantly influence the properties of PU [6].…”

Engineered polysaccharide alpha‐1,3 glucan asisocyanate‐reactivecomponent in viscoelastic polyurethane foams

“…However, the addition of alpha‐1,3‐glucan resulted in reduction in the intensity of major tangent delta transition and shifting of its peak to lower temperatures. Teduction in tangest delta transition intensity has been correlated with reduction in phase separation of polyurethane hard and soft segment 45,46,54,55 . Therefore, unlike SAN particles, the addition of alpha‐1,3‐glucan resulted in increase phase‐mixing, which results in even more restriction of the mobility of amorphous soft segment.…”