测定聚合物合金的混合热

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AN089PolumersHeat of mixing of polymer alloysby a heat of solution methodExcellence in thermal analysis and calorimetry Reference： P.N. Aukett and C.S Brown， J. Of Thermal Analysis， Vol 33， 1079-1084， (1988).BP Research Center，Sunbury-On-Thames，Middlesex， U.K. Introduction： direct measurement of the heat of mixing (interaction) ofpolymers is not feasibledue to their high viscosity. The indirect approach described here is a heat of solution method， inwhich a Hess’s Law cycle is used to determine the heat of mixing from the individual heats ofsolution of the alloy and its constituent polymers in a common solvent. The main limitation of thisapproach lies in obtaining adequate precision on the experimentally determined heats of solution，as these are large compared to the calculated heat of mixing. With this method the heat of mixing of a 75/25 (% by wt) poly(dimethyl) phenylene oxide/polystyrene alloy has been determined by SETARAM C80 microcalorimeter as 4.9+0.2 J.g-1. The precision of the method shows an improvement compared with published data. Heat of solution method In the heat of solution method a Hess’s Law cycle is used to determine AHm from the heats ofsolution (AHs) of the alloy and its constituents in a common solvent [6， 7]. Figure 1 illustrates thecycle used to determine AHm. AH、 Fig.1 Hess’s law scheme used to calculate AHm from the heats of alloy and its constituenthomopolymers (7) Heat of solution in 1，2-dichlorobenzene (J.g1) Material Mean Range Polystyrene 25.9 ±0.15 0.05 Poly(dimethylphenylene oxide) 55.2 ±0.3 0.1 PPO/PS 75%/25% 40.1 ±0.45 0.2 For more details ask forpublications B0623， B683， B684，B893 Table 1 Heats of solution of homopolymers and alloy 20℃/300℃ www.setaram.com - sales @setaram.com