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Poly(ethylene terephthalate) (PET) is a thermoplastic polyester with excellent thermal and mechanical properties, widely used in a variety of industrial fields. It is a semicrystalline polymer, and most of the industrial success of PET derives from its easily tunable crystallization kinetics, which allow users to produce the polymer with a high crystal fraction for applications that demand high thermomechanical resistance and barrier properties, or a fully amorphous polymer when high transparency of the product is needed. The main properties of the polymer are presented and discussed in this contribution, together with the literature data on the crystal structure and morphology of PET. This is followed by an in-depth analysis of its crystallization kinetics, including both primary crystal nucleation and crystal growth, as well as secondary crystallization. The effect of molar mass, catalyst residues, chain composition, and thermo-mechanical treatments on the crystallization kinetics, structure, and morphology of PET are also reviewed in this contribution. [ABSTRACT FROM AUTHOR]

Linear low‐density polyethylene (PE) containing an inclusion complex composed of β‐cyclodextrin and d‐limonene (CD‐lim) is proposed as an innovative food wrapping material with antimicrobial features. PE/CD‐lim composites are prepared by conventional, high‐volume processing, and the optical and mechanical properties of the developed formulations appear suitable for their use as food packaging materials. Compared to plain PE, the PE/CD‐lim films have improved haze and UV–vis outcomes, but also decreased gloss values. Addition of CD‐lim slightly increases water uptake, up to levels suitable for the foreseen application. It also allows to improve performance of PE as food packaging material, since the PE/CD‐lim composites provide barrier to ultraviolet light, an added value for packaging of fatty acids‐containing food items, whose shelf life is often limited by oxidation caused by UV light. Most importantly, PE/CD‐lim composites exhibit significant antimicrobial properties against a wide range of microorganisms, including fungi and bacteria. Hence, PE films containing CD‐lim display suitable properties to play a role as active food packaging films. Highlights: Development of polyethylene‐based composites containing a natural fillerComposite films with enhanced antimicrobial and antifungal efficiencyImproved transparency to visible light and barrier to UV of the composites [ABSTRACT FROM AUTHOR]

Binary blends of poly(lactic acid) (PLA) and polypropylene carbonate) (PPC) were found to display a peculiar crystallization kinetics. The two biodegradable polymers were blended by melt mixing, to obtain binary blends at various compositions. Temperature-modulated calorimetry and dynamic-mechanical analysis indicated that the blend components are partially miscible, and display two separate glass transitions, at temperatures intermediate to those of the plain polymers. Electron microscopy analysis disclosed the morphology of PLA/PPC blends, made of PPC-rich particles finely dispersed within the PLA-rich matrix. The possible establishment of interactions between the functional groups of the two polymers upon melt mixing has been hypothesized as the reason for partial miscibility and compatibility of the two biodegradable polymers. The PLA/PPC blends display good mechanical properties, with enhanced performance at rupture compared with plain PLA. Most importantly, the addition of PPC affects also the crystallization kinetics of PLA, since the more mobile PPC chains favor diffusion of the stiffer PLA chain segments towards the growing crystals, which fastens the spherulite growth rate of PLA. Such positive influence of an amorphous polymer on crystal growth rate has been demonstrated here for the first time in blends that display phase-separation in the melt., INTRODUCTION The crystallization kinetics of binary polymer blends is largely determined by miscibility of the components [1]. When the polymer pair is miscible, the crystal growth rate of the crystallizable [...]

Composites made of linear low-density polyethylene (LLDPE) and β-cyclodextrin/d-limonene inclusion complex (CD-lim) were prepared by melt extrusion to develop a novel food packaging material. Scanning electron microscopy evidenced a fairly good dispersion of the filler within the polymeric matrix. Infrared spectroscopy coupled with thermogravimetric analysis confirmed the presence of CD-lim in the composites, proving that the applied technology of including the essential oil within β-CD cages allows for preventing a sizable loss of d-limonene despite a high temperature and shear applied upon extrusion processing. Moreover, the influence of the filler on the thermal properties of PE was assessed. It was found that the cyclodextrin-based inclusion complex significantly fastens the crystallization path of the polyethylene matrix with an improved crystallization rate of the PE/CD-lim composites compared to the neat polymer. [ABSTRACT FROM AUTHOR]

Miscibility and thermal and mechanical properties of poly(butylene terephthalate) (PBT) blends with poly(ζ-caprolactone) (PCL) were analyzed as a function of the molecular mass of PCL. It was found that the components are miscible when oligomeric PCL is blended with PBT, probably due to favorable interactions between -OH end groups of poly(ζ-caprolactone) and ester groups of PBT. In the blends containing high molar mass PCL, the concentration of hydroxyl end groups is lower, allowing only partial miscibility of the components. The resulting materials display good mechanical properties, with enhanced performance at rupture compared to plain PBT. POLYM. ENG. SCI., 47:323-329,2007. [C] 2007 Society of Plastics Engineers, INTRODUCTION The blending of two or more polymers is a well-established strategy for achieving a specified portfolio of physical properties. From the standpoint of commercial applications and developments, polymer blending [...]