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Abstract:The isothermal crystallization of poly(ethylene terephthalate) (PET) homopolymers with different molecular weight was studied in a wide temperature range (140-230 °C) using different experimental techniques. Three different morphological regions, labeled r 1 , r 2 and r 3 , were distinguished as a function of crystallization temperature (T c ). In r 1 (low T c ) crystallized samples were characterized by a low crystalline degree with a small spherulite texture containing thin crystals. In r 2 (intermediate T c ) samples showed medium size spherulites composed of two distinct crystalline families (thin and thick crystals). In this temperature range, the crystallization exhibited a maximum value and it was associated with a high content of secondary crystals. In r 3 (high T c ), samples presented considerable amorphous zones and regions consisting of oversized spherulites containing only thick crystals. Time-resolved wide-angle X-ray diffraction measurements, using synchrotron radiation, indicated a rapid evolution of the crystalline degree within the second region, in OPEN ACCESSPolymers 2014, 6 584 contrast with the quite slow evolution observed in the third region. On the other hand, by small-angle X-ray scattering (SAXS) and time-resolved SAXS experiment, it was found that the long period (L) as well as the lamellar thickness (lc) increase as a function of T c , corroborating the formation of the thickest crystals in the third region. From all these observations, a morphological model was proposed for each region.

BACKGROUND A study of copper adsorption onto biosorbents prepared from grapefruit peels (GP) is presented. The objectives of the present analysis were: (1) to evaluate the use of Instant Controlled Pressure Drop (DIC) as a treatment of biosorbents preparation; (2) to assay the modified biosorbents in fixed‐bed columns; and (3) to elucidate an adsorption mechanism of the metal on the modified biosorbents. RESULTS Mercury intrusion porosimetry studies showed that the use of DIC increases the porosity of material 11.3‐fold. Adsorption capacity of GP biosorbents indicate that those prepared using a DIC process had an increase of 32% and by using a subsequent chemical treatment, an enhancement of 69%, compared with simple dried GP peel. In fixed bed adsorption studies, the maximum adsorption capacity of the bed and the minimum adsorbent rate were 52.48 mg g−1 and 24 g L−1, respectively. CONCLUSION Based on the results from the adsorption and characterization studies performed by SEM‐EDS, FTIR and XPS, it is proposed that the adsorption mechanism was a physisorption phenomenon, between oxygen‐containing groups and Cu(II) from water. High adsorption capacity can be achieved using modified GP peels in fixed‐bed columns; therefore, it is feasible to use it as a non‐conventional adsorbent. © 2016 Society of Chemical Industry

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