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The effect of molar mass on the reorganization behavior of α′-crystals of poly ( l -lactic acid) (PLLA) has been investigated by fast scanning chip calorimetry. The α′-crystals of PLLA were formed by isothermal crystallization of the relaxed melt at 90 °C or lower temperatures, and were then heated at different rates between 2 and 200 K s − 1 . Slow heating permits for all PLLA samples of different molar mass between 2 and 576 kDa reorganization of α′- into α-crystals. It was found that the α′/α-transition is suppressed if heating occurs faster than 10 K s − 1 in case of the sample with a molar mass of 576 kDa, while the critical heating rate to suppress the formation of α-crystals is increased to 30 and 100 K/s in PLLA with molar masses of around 100 kDa and 2 kDa, respectively. The faster kinetics of the α′/α-transition in case of shorter macromolecules may be explained by faster melting of smaller α′-crystals, faster growth of α-crystals from the non-isotropic melt containing remnants/self-seed from molten α′-crystals, and/or a higher number of such α′-crystal remnants/self-seed.

Melting of original crystals and their recrystallization during heating were successfully separated for isothermally crystallized poly(butylene terephthalate) (PBT). The corresponding kinetics was determined and quantitatively discussed for a wide range of heating rates (0.1–100,000 K s -1 ) using fast-scanning chip calorimetry (FSC) and differential scanning calorimetry (DSC). The double melting peaks observed on the FSC curves are assigned to the melting of original crystals (low-temperature peak) and recrystallized and/or reorganized crystals (high-temperature peak). Heating rate dependence of the degree of recrystallization has been evaluated and the kinetics was discussed on the basis of Ozawa's method. Compared with the melt-crystallization and cold-crystallization, recrystallization kinetics is the fastest process. This is because many crystal remnants, which do not transform into the isotropic melt, act as athermal nuclei, and accelerate recrystallization.

The efficiency of linear trans γ-quinacridone to nucleate formation of β-crystals in isotactic polypropylene (iPP) at rapid cooling conditions has been evaluated by a combination of fast scanning chip calorimetry (FSC) and microfocus wide-angle X-ray scattering (WAXS). For samples containing different amount of γ-quinacridone, FSC cooling experiments revealed information about a critical cooling rate above which the crystallization temperature decreases to below 105 °C, that is, to temperatures at which the growth rate of α-crystals is higher than that of β-crystals. Microfocus WAXS analysis was then applied to gain information about the competition of formation of β- and α-crystals in samples prepared at well-defined conditions of cooling at rates up to 1000 K/s in the FSC. For iPP containing 1 and 500 ppm γ-quinacridone, the crystallization temperature is lower than 105 °C on cooling faster about 10 and 70 K/s, respectively, which then on further increase of the cooling rate leads to a distinct reduction of the β-crystal fraction. The study may be considered as a first successful attempt to quantify and interpret β-crystal formation in iPP containing γ-quinacridone at processing-relevant cooling conditions in the shed of light of the different temperature-dependence of the growth rates of α- and β-crystals.

Fast scanning chip calorimetry in its non-adiabatic version allows for heating and cooling at rates up to 106 K s−1, covering all polymer processing relevant rates. Furthermore it allows for systematic studies of nucleation, crystallization, melting and reorganization for a large number of polymers. After an introduction, open problems and the need for further investigation of polymer crystallization are explained, followed by a brief description of the novel technique of fast scanning chip calorimetry and its capability to shed further light on fundamental details of the polymer-crystallization process. In the fourth part, specific examples of non-isothermal and isothermal crystallization studies are provided, including the discussion of the effect of nucleating agents. The possibility to investigate homogeneous nucleation and its kinetics is highlighted too. The fifth part focuses on the analysis of the melting kinetics and the determination of the zero-entropy-production melting temperature.

Aging of glassy isotactic polybutene-1 (iPB-1) below the glass transition temperature (Tg) leads to remarkable acceleration of the subsequent isothermal crystallization due to the promotion of crystal nuclei. The formation and development of crystal nuclei during aging below Tg and during heating to the crystallization temperature have been probed by fast scanning chip calorimetry. The size and stability of the crystal nuclei change with the aging time. A short aging below Tg can only induce nuclei with small sizes which can grow into bigger stable ones during the heating process above Tg if the heating rate is not high enough. With a prolonged aging time below Tg, bigger stable nuclei can also be developed, and its number increases till reaches a maximum value. These results suggest that noncooperative local motions rather than cooperative segmental motions in glassy iPB-1 are responsible for the formation of crystal nuclei during aging below Tg.

The kinetics of crystal nucleation of poly(L-lactic acid) (PLLA) has been analyzed by fast scanning chip calorimetry in a wide temperature range between 313 and 383 K, that is, between temperatures about 30 K below and 40 K above the glass transition temperature. The relaxed melt was rapidly cooled to the analysis temperature and subsequently aged between 10 −1 and 10 4 s, to permit formation of nuclei. The number of formed crystal nuclei has been probed by analysis of the crystallization rate at 393 K. The nucleation rate is maximal at 370–375 K and decreases monotonously with decreasing temperature in the analyzed temperature range. The observation of a monomodal dependence of the nucleation rate on temperature points to predominance of a single nucleation mechanism in the analyzed temperature range, regardless nucleation occurs in the glassy or devitrified amorphous phase. The collected data suggest that nuclei formation at ambient temperature requires a waiting time longer than about 10 8 s. The performed study is considered as a quantitative completion of nucleation-rate data available for PLLA only at temperatures higher than 360 K, suggesting that the nucleation mechanism is independent on temperature in the analyzed temperature range between 313 and 383 K.

The phase separation behavior of polymer blend thin films of 100–150 nm was studied using differential AC Chip calorimetry. By taking advantage of the low sensor and sample mass inherent to chip calorimetry, a new methodology based on temperature jumps was developed. This methodology allowed the construction of the state diagram of polymer blend thin films as evidenced for two model systems (PVME/PS and PVME/Phenoxy) displaying a lower critical solution temperature behavior. The state diagram in thin films was compared to the one obtained in bulk using Modulated Temperature DSC. In comparison with bulk, a lower phase separation temperature and a broadening of the homogeneous glass transition temperatures is observed for both model systems. This might be an indication of a surface induced ‘destabilization’ by composition gradients which are not present in bulk.