Loredana Incarnato

STRUCTURE AND RHEOLOGY OF RECYCLED PET MODIFIED BY REACTIVE EXTRUSION

Abstract In this work pyromellitic dianhydride (PMDA) was used as a chain extender to increase the molecular weight of polyethylene-terephthalate (PET) industrial scraps with low intrinsic viscosity ( IV =0.48 dl/g ), coming from a PET processing plant. The reaction was performed in a single step through reactive extrusion. Different percentages of chain extender were used in order to investigate the effect of PMDA content on the molecular structure (average molecular weight, molecular weight distribution, branching) of PET. Rheological and thermal characterizations were performed on treated PET extruded samples. In particular, the increase in the dynamic viscosity at low frequencies and the high pronounced shear thinning behavior observed in the PMDA-treated PET samples were correlated to the broadening of the Mw/Mn and to the long chain branching. These structural changes are also responsible for the decrease in the Tmc and ΔHmc and the increase in the Tcc values increasing the PMDA content in the PET samples. The study was performed also on bottle grade PET ( IV =0.74 dl/g ) for comparison purpose. The results have pointed out that with an amount of PMDA included between 0.50 and 0.75% the chain extending reaction produces an increase of Mw, a broadening of Mw/Mn and branching phenomena, that modify the PET scraps in order to make the recycled polymer suitable for film blowing and blow molding processes.

Preparation and characterization of new melt compounded copolyamide nanocomposites

In this work new copolyamide-layered silicate nanocomposites were prepared by melt compounding using a commercial polyamide 6-based copolymer, with a partially aromatic structure, as thermoplastic matrix. This copolyamide, having a lower melting point and improved mechanical and barrier properties respect to the homopolymer, appears an interesting material for producing nanocomposite packaging films. Hybrids with different organoclay loadings were produced by a twin-screw extruder using different extrusion rates, in order to point out the effects of both processing conditions and hybrid composition on morphology (silicate dispersion and exfoliation, orientation, matrix crystallinity) of nanocomposites. All melt-intercalated samples were submitted to structural (TEM and XRD), thermal and dynamic mechanical measurements. The performed analyses have evidenced that all hybrids exhibit mixed intercalated/exfoliated morphology and that the extent of exfoliation increases with both clay amount and extrusion rate used. Moreover, it was pointed out that the silicate nano-scale dispersion significantly affects the crystalline morphology of copolyamide matrix, stabilizing the γ-crystal phase, and the dynamic mechanical response of the hybrids, whose storage and loss moduli values result sensibly higher than those corresponding to the neat matrix.

Influence of Composition on Properties of Nylon 6/EVOH Blends

In this work, the relationships between composition and properties of Ny6/EVOH system were examined by means of several techniques and the results were interpreted in terms of level of compatibility. Blends of different ratio of Ny6 and EVOH have been processed in a laboratory-based film blowing extrusion apparatus. Rheologi- cal measurements, FTIR and morphological analysis, and thermal and mechanical properties were carried out. Peculiar rheological, thermal, and mechanical behaviors were observed for the blend containing 25% by weight of EVOH. At this composition, FTIR analysis has pointed out that a minimum in molecular motion is achieved as a consequence of a maximum interaction of the polar groups (amide groups of Ny6 and hydroxyl groups of EVOH) involved. Moreover, gas permeability measurements on the blown films have been performed at T 5 30°C.

Transport and mechanical properties of PET/ Rodrun 3000 blown films

Abstract Blends of different ratios of poly(ethylene terephthalate) (PET) and a thermotropic liquid crystalline polymer (TLCP) composed of 40 mol% of polyethyleneterephthalate and 60 mol% of p-hydroxybenzoic acid (Rodrun 3000) have been processed in a laboratory-based film-blowing extrusion apparatus. Gas permeability measurements have been performed on the films in order to evaluate the effect of the mesophase on the transport behaviour of PET films. The transport properties of the blends are dependent upon the state dispersion of the minor phase; thus, scanning electron microscopy has been conducted on the film surfaces to observe the morphological structure of the TLCP developed during the extrusion process. Moreover, the mechanical properties of the films at 2, 10 and 30% (w/w) TLCP contents have been examined in both the transverse and flow directions.

Processing-Structure-Properties Relationships in Blends with Thermotropic Liquid Crystalline Polymers

Abstract In this paper the effect of the inclusion of thermotropic liquid crystalline polymers (TLCP) in thermoplastic polymers is analyzed, with due attention to similar studies reported in the literature. Numerous results relative to TLCP containing blends are considered in terms of structure development in typical processing operations like extrusion and fiber spinning. Several systems have been studied in order to emphasize that different effects can be obtained as regards processing and mechanical properties of the host matrices. As for rheological aspects, it has been verified that TLCP can be considered as effective flow aids, even at low concentrations. The addition of a low percentage (5 to 10 %) of a TLCP with a viscosity lower than that of the matrix produces a significant reduction (25 to 40 %) in the blend viscosity. Moreover, mechanical results have shown that an improvement of the matrix rigidity can be obtained, especially at high percentages of TLCP (30 %), under processing conditions where a highly extensional flow prevails. However, a decrease in the ultimate elongation of the matrices has been found in all systems where a poor adhesion between the two phases exists.

Thermal behaviour of the PET/Rodrun 3000 system

The crystallization behaviour of poly(ethylene terephthalate) (PET) and its blends with a liquid crystal polymer (Rodrun 3000) was studied by differential scanning calorimetry (d.s.c.), under both non-isothermal and isothermal conditions. The theories of Ozawa and Avrami were applied to study the kinetics of non-isothermal and isothermal crystallization respectively. In both cases it was found that a very low percentage of a thermotropic liquid crystal polymer (TLCP) determines an increase in the overall crystallization rate, while increasing the amount of TLCP results in a progressive decrease in the crystallization rate and the melting temperature. However, the crystallinity of PET in the blends was found to increase on increasing the TLCP content.

Relationships between processing‐structure‐migration properties for recycled polypropylene in food packaging∗

In this work the relationships between processing, structure and migration properties of recycled polypropylene (PP) were analysed in relation to the possible use of recycled PP in food packaging applications. PP containers used in food packaging were contaminated with food and then washed, reduced into a processable size, dried and reprocessed by injection moulding. Gel Permeation Chromatography (GPC) analysis, mechanical, and total migration tests were performed on injection moulded samples to verify the effect of the recycling process on the structure and properties of PP. In order to evaluate the effect of the molecular weight on the properties of the recycled polymer, the study was conducted on containers produced by injection moulding made from a low molecular weight (LMW) PP and on containers produced by thermoforming made from a high molecular weight (HMW) PP.

Performance properties, lactic acid specific migration and swelling by simulant of biodegradable poly(lactic acid)/nanoclay multilayer films for food packaging

ABSTRACT The aim of the study was the development of a multifunctional, high-performance, fully biodegradable multilayer polylactic acid (PLA) film for food packaging applications. In particular, sealable multilayer PLA–clay nanocomposite systems with different layouts in terms of composition and relative thickness of the layers, all consisting of a PLA–clay nanocomposite layer between two pure PLA layers for direct food contact, were designed and produced by blown film co-extrusion. The films obtained were analysed for their morphology, functional properties and lactic acid (LA)-specific migration in 50% ethanol. The results showed that, with respect to the unfilled multilayer system, taken as a reference, the nanocomposite films had significant improvements, up to about 40%, in their barriers to oxygen and tensile strengths, and resulted in being more easily sealable over a wide heat-sealing temperature range (80–100°C) with higher seal strength. Moreover, all films had LA migrations always well below the former generic overall migration limit of 60 mg kg–1 food (10 mg dm–2) of European Union Regulation No. 10/2011 (deleted by the amending Regulation No. 2016/1416), even if their morphology was strongly modified during the migration tests due to the strong swelling action of the used simulant (simulant D1 = 50% ethanol (aq.) (v/v)) towards PLA.

Synthesis and characterisation of a nematic homo-polyurethane

The presence of hydrogen bonds in the chemical structure of polymers promotes and stabilises the crystalline phase. For liquid crystalline (LC) polymers, the side insertion of aliphatic units to the mesogenic unit is a suitable artifice to decrease the crystalline stability, without significantly affecting the stability of the LC phases. Here, we report on the synthesis of a LC homo-polyurethane with high hydrogen bond concentration along the chain and bearing an n-pentyl side-chain. Rheological behaviour, thermal analysis, and X-ray diffraction show that the stable LC phase is the nematic.

Structural Characterization of Nylon 6/EvOH System Through Transport Properties

In this paper, the effect of the inclusion of ethylene/vinyl alcohol (EvOH) copolymer in nylon 6 is analyzed with particular attention to the transport properties. Water vapor and dichloromethane transport measurements were performed to provide useful information about polymer-polymer interaction and segmental mobility. Sorption and diffusion tests were carried out at 25°C at several activities to determine both sorption isotherm and diffusivities. Moreover, permeability tests to gases (CO2, O2) were carried out at 30°C. The obtained results indicate the existence of strong hydrogen-bonded interactions of the two polar groups (amidic of nylon 6 and hydroxyl of EvOH) within the amorphous phase. This interaction strongly influences the transport properties of the nylon 6 amorphous component.