Heat capacities of aqueous binary and ternary mixtures (with piperazine) of N-(2-aminoethyl)-piperazine and N,N,N′-trimethylethylenediamine at temperatures (303.2–353.2) K

•Heat capacities of aqueous mixtures (with piperazine) of two polyamines were measured.•Two polyamines are N-(2-aminoethyl)piperazine and N,N,N′-trimethylethylenediamine.•The measured data were reported as functions of temperature and composition.•The measured data were represented satisfactorily by the applied correlations.