Carbon dioxide formation during initial stages of photodegradation of poly(ethyleneterephthalate) (PET) films

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Using Different Co-Adjuvant Activating Agents to Improve Activated Carbon Adsorption Capacities

Activated carbon (AC) has proved to be an effective adsorbent for the removal of an assortment of organic and inorganic pollutants from aqueous or gaseous media. However, the pursuit for more effective and cheaper AC is still very active and a diversity of textural and chemical treatments are described as a way to expand their applications. It is well known that the surface area and surface chemistry of AC strongly affect their adsorption capacity [1-3]. In particular, an increase in the nitrogen content has been related to an increase of the basic character and also to the development of the porous structure. In most published work this was achieved through an AC post treatment, including either a reaction with nitrogen containing reagents, such as ammonia, nitric acid, or a diversity of amines. However, the AC prepared directly from a nitrogen rich precursor through a physical or chemical activation is referred to as presenting the best characteristics, namely high nitrogen content, high basic character, low nitrogen leaching and also a good thermal stability [4]. To improve the AC adsorption capacities for acidic pesticide removal from the aqueous phase, we intend to improve the porous structure and introduce nitrogenated groups directly into the AC matrix, using different co-adjuvant activating agents as a nitrogen source, by chemical activation, with potassium hydroxide, of cork or poly(ethyleneterephthalate) (PET) precursors.

Crystallization and properties of poly(ethylene terephtalate) copolymers containing 5-tert-butyl isophtalic units

The influence of incorporating 5-tert-butyl isophthalic units (tBI) in the polymer chain of poly(ethylene terephthalate) (PET) on the crystallization behavior, crystal structure, and tensile and gas transport properties of this polyester was evaluated. Random poly(ethyleneterephthalate-co-5-tert-butyl isophthalate) copolyesters (PETtBI) containing between 5 and 40 mol% of tBI units were examined. Isothermal crystallization studies were performed on amorphous glassy films at 120 8C and on molten samples at 200 8C by means of differential scanning calorimetry. Furthermore, the non-isothermal crystallization behavior of the copolyesters was investigated. It was observed that both crystallinity and crystallization rate of the PETtBI copolyesters tend to decrease largely with the comonomeric content, except for the copolymer containing 5 mol% of tBI units, which crystallized faster than PET. Fiber X-ray diffraction patterns of the semicrystalline PETtBI copolyesters proved that they adopt the same triclinic crystal structure as PET with the comonomeric units being excluded from the crystalline phase. Although PETtBI copolyesters became brittle for higher contents in tBI, the tensile modulus and strength of PET were barely affected by copolymerization. The ncorporation of tBI units slightly increased the permeability of PET, but copolymers containing up to 20 mol% of the comonomeric units were still able to present barrier properties.

Gas permeation in silicon-oxide/polymer (SiOx/PET) barrier films: role of the oxide lattice, nano-defects and macro-defects

We propose a model for permeation in oxide coated gas barrier films. The model accounts for diffusion through the amorphous oxide lattice, nano-defects within the lattice, and macro-defects. The presence of nano-defects indicate the oxide layer is more similar to a nano-porous solid (such as zeolite) than silica glass with respect to permeation properties. This explains why the permeability of oxide coated polymers is much greater, and the activation energy of permeation much lower, than values expected for polymers coated with glass. We have used the model to interpret permeability and activation energies measured for the inert gases (He, Ne and Ar) in evaporated SiOx films of varying thickness (13-70 nm) coated on a polymer substrate. Atomic force and scanning electron microscopy were used to study the structure of the oxide layer. Although no defects could be detected by microscopy, the permeation data indicate that macro-defects (>1 nm), nano-defects (0.3-0.4 nm) and the lattice interstices (<0.3 nm) all contribute to the total permeation. (C) 2002 Elsevier Science B.V. All rights reserved.

Synthesis and NMR characterization of aliphatic-aromatic copolyesters by reaction of poly(ethylene terephthalate) post-consumer and poly(ethylene adipate)

An aliphatic-aromatic copolyester of poly(ethylene terephthalate), PET, and poly(ethylene adipate), PEA, PET-co-PEA, was synthesized by the high temperature melt reaction of post-consumer PET and PEA. As observed by NMR spectroscopy, the reaction yielded random copolyesters in a few minutes through ester-interchange reactions, even without added catalyst. The copolyesters obtained in the presence of a catalyst presented higher intrinsic viscosity than that obtained without the addition of catalyst, due to simultaneous polycondensation and ester-interchange reactions. The structure of the aliphatic-aromatic copolyesters obtained in different PET/PEA ratio is random as observed by NMR analysis.

Carbon nanotubes induced crystallization of poly(ethylene terephthalate)

We have investigated the crystallization characteristics of melt compounded nanocomposites of poly(ethylene terephthalate) (PET) and single walled carbon nanotubes (SWNTs). Differential scanning calorimetry studies showed that SWNTs at weight fractions as low as 0.03 wt% enhance the rate of crystallization in PET, as the cooling nanocomposite melt crystallizes at a temperature 10 °C higher as compared to neat PET. Isothermal crystallization studies also revealed that SWNTs significantly accelerate the crystallization process. WAXD showed oriented crystallization of PET induced by oriented SWNTs in a randomized PET melt, indicating the role of SWNTs as nucleating sites.

Carbon Nanotubes-Reinforced PET Nanocomposite by Melt-Compounding

Poly(ethylene terephthalate) (PET) nanocomposites with single-walled carbon nanotubes (SWNTs) have been prepared by a simple melt compounding method. With increasing concentration (0-3 wt %) of SWNTs, the mechanical and dynamic mechanical properties improved, corresponding to effective reinforcement. Melt rheological characterization indicated the effective entanglements provided by SWNTs in the melt state as well. Thermogravimetric analysis suggested no influence of SWNTs on the thermal stability of PET. Electrical conductivity measurements on the composite films pointed out that the melt compounded SWNTs can result in electrical percolation albeit at concentrations exceeding 2 wt %.

PET-SWNT nanocomposites through ultrasound assisted dissolution-evaporation

Poly(ethylene terephthalate) (PET) based nanocomposites have been prepared with single walled carbon nanotubes (SWNTs) through an ultrasound assisted dissolution-evaporation method. Differential scanning calorimetry studies showed that SWNTs nucleate crystallization in PET at weight fractions as low as 0.3%, as the nanocomposite melt crystallized during cooling at temperature 24 °C higher than neat PET of identical molecular weight. Isothermal crystallization studies also revealed that SWNTs significantly accelerate the crystallization process. Mechanical properties of the PETSWNT nanocomposites improved as compared to neat PET indicating the effective reinforcement provided by nanotubes in the polymer matrix. Electrical conductivity measurements on the nanocomposite films showed that SWNTs at concentrations exceeding 1 wt% in the PET matrix result in electrical percolation. Comparison of crystallization, conductivity and transmission electron microscopy studies revealed that ultrasound assisted dissolution-evaporation method enables more effective dispersion of SWNTs in the PET matrix as compared to the melt compounding method

Estudo morfológico da blenda polimérica poli(metacrilato de metila)/poli(tereftalato de etileno) reciclado (PMMA/PET)

Among the options for plastics modification more convenient, both from a technical-scientific and economic, is the development of polymer blends by processing in the molten state. This work was divide into two stages, with the aim to study the phase morphology of binary blend PMMA / PET blend and this compatibilized by the addition of the poly(methyl methacrylate-co-glycidyl methacrylate-co-ethyl acrylate) copolymer (MMA-GMA-EA). In the first stage is analyzed the morphology of the blend at a preliminary stage where we used the bottle-grade PET in a Haake torque rheometer and the effect of compatibilizer in this blend was evaluated. In the second stage the blend was processed using the recycled PET in a single screw extruder and subsequently injection molding in the shape of specimens for mechanical tests. In both stages we used a transmission electron microscopy (TEM) to observe the morphologies of the samples and an image analyzer to characterize them. In the second stage, as well as analysis by TEM, tensile test, scanning electron microscopy (SEM) and atomic force microscopy (AFM) was performed to correlate the morphology with the mechanical properties. The samples used in morphological analyzes were sliced by cryo-ultramicrotomy technique for the analysis by TEM and the analysis by SEM and AFM, we used the flat face of the block after cut cryogenic. It was found that the size of the dispersed phase decreased with the addition of MMA-GMA-EA in blends prepared in a Haake. In the tensile test, the values of maximum tensile strength and modulus of elasticity is maintained in a range between the value of pure PMMA the pure PET, while the elongation at break was influenced by the composition by weight of the PMMA mixture. The coupling agent corroborated the results presented in the blend PMMA / PETrec / MMA-GMA-EA (80/15/5 %w/w), obtained by TEM, AFM and SEM. It was concluded that the techniques used had a good morphologic correlation, and can be confirmed for final analysis of the morphological characteristics of the blends PMMA / PET

Influência das espécies do plasma de N2 + O2 nas propriedades físicoquímicas das superfícies do pet

This work reports the influence of the poly (ethylene terephthalate) textile and films surface modification by plasmas of O2 and mixtures (N2 + O2), on their physical and chemical properties. The plasma surface polymeric modification has been used for many researchs, because it does not affect the environment with toxic agents, the alterations remains only at nanometric layers and this technique shows expressive results. Then, due to its good acceptance, the treatment was carried out in a vacuum chamber. Some parameters remained constant during all treatment, such as: Voltage 470 V; Pressure 1,250 Mbar; Current: 0, 10 A and gas flow: 10 cm3/min, using oxygen plasma alternating the treatment time 10 to 60 min with an increase of 10 min to each subsequent treatment. Also, the samples were treated with a gas mixture (nitrogen + oxygen) which was varied only the gas composition from 0 to 100% leaving the treatment time remaining constant to all treatment (10 min). The plasma treatment was characterized in-situ with Optics Emission Spectroscopy (OES), and the samples was characterized by contact angle, surface tension, Through Capillary tests, Raman spectroscopy, Infrared attenuated total reflection (IR-ATR) and atomic force microscopy, scanning electronic Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS). The results showed that oxygen treated fabrics presented high wettability, due to the hydrophilic groups incorporation onto the surface formed through spputering of carbon atoms. For the nitrogen atmosphere, there is the a film deposition of amine groups. Treatment with small oxygen concentration in the mixture with nitrogen has a higher spputered species of the samples

Desenvolvimento e caracterização de compósitos poli(tereftalato de etileno) reciclado (PET reciclado) com flocos de vidro.

The growing concern with the solid residues management, observed in the last decade, due to its huge amount and impact, has motivated the search for recycling processes, where these residues can be reprocessed to generate new products, enlarging the cycle of materials and energy which are present. Among the polymeric residues, there is poly (ethylene terephthalate) (PET). PET is used in food packaging, preferably in the bottling of carbonated beverages. The reintegration of post-consumer PET in half can be considered a productive action mitigation of environmental impacts caused by these wastes and it is done through the preparation of several different products at the origin, i.e. food packaging, with recycling rates increasing to each year. This work focused on the development and characterization mechanical, thermal, thermo-mechanical, dynamic mechanical thermal and morphology of the pure recycled PET and recycled PET composites with glass flakes in the weight fraction of 5%, 10% and 20% processed in a single screw extruder, using the following analytical techniques: thermogravimetry (TG), differential scanning calorimetry (DSC), tensile, Izod impact, Rockwell hardness, Vicat softening temperature, melt flow rate, burn rate, dynamic mechanical thermal analysis (DMTA) and scanning electron microscopy (SEM). The results of thermal analysis and mechanical properties leading to a positive evaluation, because in the thermograms the addition of glass flakes showed increasing behavior in the initial temperatures of thermal decomposition and melting crystalline, Furthermore was observed growing behavior in the mechanical performance of polymer composites, whose morphological structure was observed by SEM, verifying a good distribution of glass flakes, showing difference orientation in the center and in the surface layer of test body of composites with 10 and 20% of glass flakes. The results of DMTA Tg values of the composites obtained from the peak of tan ä showed little reductions due to poor interfacial adhesion between PET and recycled glass flakes.

Processamento e caracterização da blenda poli (metacrilato de metila) (PMMA) elastomerico e poli (tereftalato de etileno) (PET) pós-consumo

This work studied the immiscible blend of elastomeric poly(methyl methacrylate) (PMMA) with poly(ethylene terephthalate) (PET) bottle grade with and without the use of compatibilizer agent, poly(methyl methacrylate-co-glycidyl methacrylate - co-ethyl acrylate) (MGE). The characterizations of torque rheometry, melt flow index measurement (MFI), measuring the density and the degree of cristallinity by pycnometry, tensile testing, method of work essential fracture (EWF), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were performed in pure polymer and blends PMMA/PET. The rheological results showed evidence of signs of chemical reaction between the epoxy group MGE with the end groups of the PET chains and also to the elastomeric phase of PMMA. The increase in the concentration of PET reduced torque and adding MGE increased the torque of the blend of PMMA/PET. The results of the MFI also show that elastomeric PMMA showed lower flow and thus higher viscosity than PET. In the results of picnometry observed that increasing the percentage of PET resulted in an increase in density and degree crystallinity of the blends PMMA/PET. The tensile test showed that increasing the percentage of PET resulted in an increase in ultimate strength and elastic modulus and decrease in elongation at break. However, in the phase inversion, where the blend showed evidence of a co-continuous morphology and also, with 30% PET dispersed phase and compatibilized with 5% MGE, there were significant results elongation at break compared to elastomeric PMMA. The applicability of the method of essential work of fracture was shown to be possible for most formulations. And it was observed that with increasing elastomeric PMMA in the formulations of the blends there was an improvement in specific amounts of essential work of fracture (We) and a decrease in the values of specific non-essential work of fracture (βWp)

Post consumer pet depolymerization by acid hydrolysis

The reaction of post-consumer poly(ethylene terephthalate) with aqueous solutions of sulfuric acid 7.5M was investigated in terms of temperature, time and particle size. The reaction extent reached 80% in four days at 100 degrees C and 90% in 5 hours at 135 degrees C. TPA obtained was purified and considered in the same level of quality of the commercial one after tests of elemental analysis, particle size and color. It was concluded that the hydrolysis occurred preferentially at the chain ends and superficially, having as controller mechanism the acid diffusion into the polymer structure. The shrinking-core model can explain the reaction kinetics.

Additional steps in mechanical recyling of PET

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Application of Nonisothermal Cure Kinetics to the Interaction of Poly(ethylene terephthalate) with Alkyd Resin Varnish

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)