Interfacial tension in polymer melts. Part II: Effects of temperature and molecular weight on interfacial tension

Abstract

Interfacial tension is one of the most important parameters that govern the morphology of polymer blends and the quality of adhesion between polymers. However, few data are available on interfacial tension due to experimental difficulties. A pendant drop apparatus was used for the determination of the interfacial tension for the polymer pair polypropylene/polystyrene (PP/PS). The effects of temperature and molecular weight were evaluated. The range of temperatures used was from 178° to 250°C, and the range of molecular weights used was from 1590 to 400,000. The interfacial tension decreased linearly with increasing temperature. With only one exception, higher molecular weight systems showed weaker dependence of interfacial tension on temperature than lower molecular weight systems. Also, polydisperse systems showed a stronger dependency on temperature than the monodisperse systems. The value of the interfacial tension, which increases with molecular weight, appears to level off at molecular weights above the entanglement chain length. For the polymer pair PP/PS, the dependency of the interfacial tension on the number average molecular weight appears to follow the well‐known semi‐empirical (−2/3) power rule over most of the range of molecular weights. Comparable correlations were obtained with values of the power between −1/2 and −1.0.

Transient interfacial tension and dilatational rheology of diffuse polymer-polymer interfaces

“…This is understood from the fact that mixing of long molecules is less favorable, 13 a well known phenomenon that was reported earlier. 33,34 The results also show that the effect of the low molecular weight phase ͑here this is always the drop phase except for the B3 combination͒ on the value of the interfacial tension ͑the A combinations versus the B combinations͒ is more pronounced than the ratio of the molecular weight. For example, the systems B4 and A3 have the same order of asymmetry but a large difference in the interfacial tension ␥ while the systems B3 and B4 have a big difference in asymmetry but relatively small difference in ␥.…”

Interfacial tension of PBT/SAN blends by the drop retraction method

“…In addition, the experimental values stay between the harmonic Table 5 that the change in (-dg/dT) from 0.06 to 0.08 does not change significantly the calculated interfacial tension values. For the PBT/SAN system, it was observed an increase in the interfacial tension as a function of the increase in the PBT molecular weight, as already observed by Kamal 25 for PP/ PS systems. For that system the increase was observed up to a certain molecular weight then it leveled off for further increase.…”

Transient interfacial tension of partially miscible polymers

“…The most easily accessible thermodynamic parameter related to the interfacial zone, that also controls morphology and adhesion properties in polymer blends, is interfacial tension and therefore, the focus is to study its evolution in time. In Peters et al [10] it is concluded that increasing the molecular weight of either phase, matrix or drop, leads to higher values of the interfacial tension, in accordance with the results shown in [1,[11][12][13], and it is reported that, above a critical molecular weight value, a plateau value in interfacial tension is approached. The influence of temperature is studied in [1,11,[13][14][15] and both an increase and Wagner et al [14] even found a maximum in σ (t) for some combinations of chains lengths, attributed to close miscibility gaps.…”