Multiple melting behavior in isothermally cold-crystallized isotactic polystyrene

Calorimetric analysis of the multiple melting behavior of melt-crystallized poly(l-lactic acid) with a low optical purity

“…The number-averaged and weight-averaged molecular weights were determined by gel permeation chromatography (GPC) as 71 000 and 118 000 Da, respectively. The rotatory power (½a 25 L ) was measured in chloroform at a concentration of 1 g dL -1 and at 25°C using a Jasco P-1010 polarimeter at a wavelength of 589 nm. The optical purity (OP) was calculated by the following equation:…”

“…Especially, the melting of semicrystalline thermoplastic is a very complex process, which is influenced significantly by the crystallization conditions. Double or multiple melting behavior has been observed in many semicrystalline polymers such as polypropylene (PP) [23,24], polystyrene (PS) [25], poly(ether ether ketone) (PEEK) [26][27][28], poly(ethylene terephthalate) (PET) [29,30], poly(butylene-2,6-naphthalate) (PBN) [31], poly(trimethylene terephthalate) (PTT) [32], and some biodegradable aliphatic polyesters, e.g., poly(butylene succinate) and copolymers [33][34][35]. It is an important research subject in the field of polymer science to gain a basic understanding of the structural evolution related to thermal history (i.e., crystallization conditions) and to provide a deep insight into the crystallization and melting processes of semicrystalline polymers.…”

“…It is an important research subject in the field of polymer science to gain a basic understanding of the structural evolution related to thermal history (i.e., crystallization conditions) and to provide a deep insight into the crystallization and melting processes of semicrystalline polymers. As summarized in the literature [25,36,37], possible origins of the complex melting phenomenon are as follows: (1) the presence of more than one crystal forms (polymorphism), (2) the presence of different morphologies (such as lamellar thickness, distribution, perfection, or stability), (3) melting, recrystallization, and remelting processes during heating, (4) physical aging and/or relaxation of the rigid amorphous fraction, (5) different molecular weight species, and so on.…”

Preparation and Characterization of Anisotropic Submicron Particles From Semicrystalline Polymers

“…Both cold crystallization and double-melting behavior are well-known phenomena. [43][44][45][46] However, the observation of a single melting peak for the macroemulsion prepared from iPS is somewhat unexpected. As we did not fi nd any tabulated values for the enthalpy of cold crystallization for iPS, the degree of cold crystallization was not calculated.…”

The impact of polypropylene‐graft‐maleic anhydride on the crystallization and dynamic mechanical properties of isotactic polypropylene

“…A double melting endotherm for isotactic PP is consistent with the existence of two crystal forms with distinct lamellar thickness and thermal stability. [18][19][20][21][22] Neat MAPP melts at 142 C, $ 20 C below PP. In the MAPP/PP blends, only one melting point around 165 C, characteristic of PP, remains.…”