Thermal conductivity of polymers

Heat capacity of poly(lactic acid)

Mesophases in polyethylene, polypropylene, and poly(1-butene)

Abstract The heat capacity of poly(lactic acid) (PLA) is reported from T=(5 to 600) K as obtained by differential scanning calorimetry (d.s.c.) and adiabatic calorimetry. The heat capacity of solid PLA is linked to its group vibrational spectrum and the skeletal vibrations, the latter being described by a Tarasov equation with Θ1=574 K, Θ2=Θ3=52 K, and nine skeletal vibrations. The calculated and experimental heat capacities agree to ±3% between T=(5 and 300) K. The experimental heat capacity of liquid PLA can be expressed by Cp(liquid)=(120.17+0.076T) J · K−1 · mol−1 and has been compared to the ATHAS Data Bank, using contributions of other polymers with the same constituent groups. The glass transition temperature of amorphous PLA occurs at T=332.5 K with a change in heat capacity of 43.8 J · K−1 · mol−1. Depending on thermal history, semi-crystalline PLA has a melting endotherm between T=(418 and 432) K with variable heats of fusion. For 100% crystalline PLA, the heat of fusion is estimated to be (6.55 ± 0.02) kJ · mol−1 at T=480 K. With these results, the enthalpy, entropy, and Gibbs function of crystalline and amorphous PLA were obtained. For semi-crystalline samples, one can check changes of crystallinity with temperature and judge the presence of rigid-amorphous fractions.

Heat Capacity of Poly(L-lactic acid)

Perfluoropolyethers: Their physical properties and behaviour at high and low temperatures

Linear high polymers heat capacity measurements theory emphasizing simple mechanical systems and contribution of lattice vibrations

H. Baur

Papers

Heat capacities of linear high polymers