Environmentally Compatible Polymeric Blends and Composites Based on Oxo-Biodegradable Polyethylene

The study of this thesis was focused on materials based on polyethylene (PE), which remains as the largest polymer used in the field of packaging. This polymer is not biodegradable and its waste represents a serious problem to the environment. A proposal of eco-compatible PE based materials will be presented. This is bound to the enhancement of the polyethylene oxo-biodegradability through the blending with biodegradable polymers of biosynthetic origin, [poly(hydroxybutyrate) (PHB) or starch] and commercial prodegradant additives. This work was structured in three chapters. In the first chapter, the compatibilization between PE and PHB was studied. For this purpose, a screening statistical design experiment (DEX) was preformed, in order to assist in the selection of the better compatibilizer and materials proportions. The variables selected were three copolymers, containing both PE and polar segments, and their amount in the blend, which was constrained at the limits of 10 wt-% and 40 wt-% depending on the compatibilizer. These compatibilizers were poly(ethylene-co-vinyl acetate) (EVA), poly(ethylene-co-glycidyl methacrylate) (EGMA) and poly(ethylene-co-methyl acrylate (EMAC). The films were characterized by means of thermal analysis (TGA and DSC), scanning electron microscopy (SEM), wide angle x-ray scattering (WAXS), Photoacoustic Fourier Transform Infrared Spectroscopy (PAS-FTIR), dynamic mechanical thermal analysis (DMTA) and tensile tests (Instron). EGMA was chosen as the compatibilizer to formulate a new series of materials. This compatibilizer promoted the better adhesion between PE and PHB than the others two tested copolymers did. The best formulation was found for PE matrix with 10 wt-% of EGMA (68E22B10G). In the second chapter, PE-PHB-EGMA blends were formulated in presence or not of prodegradant additives (Totally Degradable Plastics Additives - TDPA®) DCP562 (T6) and DCP571 (T7). The formulation strategy followed a central composite design (CCD) where the independent variables were the amount of the biodegradable polymer PHB and of the prodegradant additives T6 and T7. Films were characterized by means of SEM, TGA, DSC, FTIR and Instron. This family of materials was submitted to a thermal aging experiment at three temperatures (45, 55 and 65 °C). Gravimetry, FTIR, SEC, TGA, DSC and Instron were carried out to characterize the thermal aged samples. The prodegradants were effective in promoting PE oxidation. Thermal aged PE-PHB-EGMA-TDPA blends samples showed significant changes on weight gain and carbonyl index (COi) measured in FTIR spectra. By means of COi were evaluated the activation energy (Ea) of thermal degradation applying the Arrhenius equation. Blends containing PHB presented lower values of activation energy (54 kJ/mol for 2B3T6) compared to the equivalent blend without PHB (81 kJ/mol for 3T6). Samples from thermal aging were biodegraded in both aquatic media and soil burial. The biodegradation of the blends in both ambient showed low mineralization. For example, the maximum mineralization of 2B3T6t (85.5PE-9.5EGMA-2PHB-3T6) sample was ca. 4 % after 140 days in soil burial, probably as a consequence of the large extent of crosslinking occurred during the thermal aging, which in this case increased up to 76 %. The last chapter of this thesis comprises two series of experiment concerning PE-Starch composites. In the first one, the compatibilization of compression moulded PE-Starch materials was studied. In the second part, selected composites of compatibilized PE-Starch were prepared by melt blow extrusion. Two different types of starches and two compatibilizers were defined as variables: thermoplastic corn-starch (TPS) and natural corn starch (CS) as fillers and EVA and EGMA as compatibilizers. The results obtained showed that: i) PE-TPS films resulted in very distinct phase separation even when higher amounts of EVA and EGMA were used; ii) In the PE-CS films the compatibilizer EGMA at 20 wt-% provided a good dispersion of starch granules. In addition, blends containing CS produced films more homogeneous than that with TPS. The best compatibilized formulation was used to prepare by melt blow extrusion PE-CS based composites and PE-Biopar blends containing or not T6 and T7 prodegradants, whose films were mechanically tested. The mechanical properties of PE family of materials containing CS and Biopar presented similar values for Young modulus (100-200 MPa). However, films with Biopar presented higher values of tensile strain (ca. 200 %) than films with CS (ca. 100%)

Mechanical and moisture barrier properties of titanium dioxide nanoparticles and halloysite nanotubes reinforced polylactic acid (PLA)

Polylactic acid (PLA) has been larger used in biomedical field due to its low toxicity and biodegradability. The aim of this study was to produce PLLA nanocomposites, by melt extrusion, containing Halloysite nanotubes (HNT) and/or titanium dioxide (TiO2) nanoparticles. Immediately after drying, PLLA was mechanically homogenized with the nanofillers and then melt blended using a single screw extruder (L/D = 30) at a speed of 110 rpm, with three heating zones in which the following temperatures were maintained: 150, 150 and 160ºC (AX Plásticos model AX14 LD30). The film samples were obtained by compression molding in a press with a temperature profile of 235 ± 5ºC for 2.5 min, after pressing, films were cooled up to room temperature. The mechanical tests were performed according to ASTM D882-09 and the water vapor permeability (WVP) was measured according to ASTM E-96, in triplicate. The tensile properties indicated that the modulus was improved with increased TiO2 content up to 1g/100g PLLA. The Young's modulus (YM) of the PLA was increased from 3047 MPa to 3222 MPa with the addition of 1g TiO2/100g PLLA. The tensile strength (TS) of films increases with the TiO2 content. In both cases, the YM and TS are achieved at the 1% content of TiO2 and is due to the reinforcing effect of nanoparticles. Pristine PLA showed a strain at break (SB) of 3.56%, while the SB of nanocomposites were significant lower, for instance the SB of composite containing 7.5 g HNT/100g PLLA was around 1.90 %. The WVP of samples was increased by increasing the nano filler content. It should be expected that an increase of nanofiller content would decrease the mass transfer of water molecules throughout the samples due to the increase in the way water molecules will have to cross to permeate the material. However, this was not observed. Therefore, this result can be explained considering the molecular structure of both fillers, which contain several hydroxyl groups in the surface, making the end material more hydrophilicPostprint (published version

Perceptualand cognitive factors imposing "speed limits" on reading rate: a study with the rapid serial visual presentation

Adults read at high speed, but estimates of their reading rate vary greatly, i.e., from 100 to 1500 words per minute (wpm). This discrepancy is likely due to different recording methods and to the different perceptual and cognitive processes involved in specific test conditions. The present study investigated the origins of these notable differences in RSVP reading rate (RR). In six experiments we investigated the role of many different perceptual and cognitive variables. The presence of a mask caused a steep decline in reading rate, with an estimated masking cost of about 200 wpm. When the decoding process was isolated, RR approached values of 1200 wpm. When the number of stimuli exceeded the short-term memory span, RR decreased to 800 wpm. The semantic context contributed to reading speed only by a factor of 1.4. Finally, eye movements imposed an upper limit on RR (around 300 wpm). Overall, data indicate a speed limit of 300 wpm, which corresponds to the time needed for eye movement execution, i.e., the most time consuming mechanism. Results reconcile differences in reading rates reported by different laboratories and thus provide suggestions for targeting different components of reading rate

Mercerizing/bleaching of natural brazilian fibers: thermal analysis

O crescente consumo de materiais poliméricos originários de fontes não renováveis (base petroquímica), apresentam baixo potencial de biodegradabilidade, e podem demorar desde décadas, até séculos, para se decompor por meio de processos naturais, promovem impactos socioambientais negativos no ambiente. Ao basear-se na percepção de que os recursos naturais não renováveis tendem a escassez, surge a necessidade de buscar recursos de fontes renováveis, como é o caso das fibras vegetais, que são extraídas de plantas renováveis e sustentáveis, e podem ser obtidas de diversas fontes, devido a sua composição química, constituem-se principalmente de celulose e lignina. Diante do desafio de aumentar o campo de aplicação das fibras naturais e dos polímeros biodegradáveis, em uma primeira etapa, foram analisadas as características térmicas de duas fibras naturais existentes oriundas de plantas/árvores/frutos nativos (casca do coco de Babaçu, casca da castanha de Barú) in natura e após o processo de mercerização e branqueamento. Como resultados verificou-se que as fibras naturais empregadas sofrem alterações químicas e estruturais como a remoção dos constituintes amorfos da estrutura: a lignina, hemicelulose, ceras e compostos álcali-solúveis, em virtude do processo de mercerização/branqueamento aplicado. Essas alterações influenciam na estabilidade térmica, que melhoraram nas amostras branqueadas, cerca de 4% para a fibra de babaçu, e 11,71% para a fibra de barú, quando comparadas as fibras in naturaPostprint (published version

Caracterização e biodegradação de filmes de quitosana e proteína isolada de soja incorporados com nanocristais de celulose / Characterization and biodegradation of chitosan and soy protein isolate films incorporated with cellulose nanocrystals

A produção de embalagens oriundas de matérias primas sintéticas vem aumentando exponencialmente, com isso tem ocasionado graves problemas ambientais devido a alta longevidade desses materiais. Surge então a necessidade da substituição de produtos de origem sintética por produtos de fontes renováveis, e o desenvolvimento de novos produtos a partir de processos mais limpos de fabricação. Os nanocristais de celulose são materiais que tem chamado atenção de pesquisadores, devido à suas características físicas e químicas e sua aplicação como reforço em outras matrizes poliméricas. Neste contexto o objetivo deste trabalho foi a obtenção  de nanocristais de celulose, a partir da palha do milho (Zea mays) e incorporação dos nanocristais em matrizes poliméricas de quitosana e proteína isolada de soja, com o intuito de traçar o melhor parâmetro a extração dos nanocristais  e sua caracterização, como também a biodegradabilidade deste filmes. Observou-se que nos filmes de quitosana e SPI, não houve alteração no processo de degradação pelo processo de adição dos nanocristais em comparação com o controle, sugerindo que os nanocristais não interferem na biodegradabilidade das matrizes a qual são inseridos

The effect of fatty acids on the physicochemical properties of edible films composed of gelatin and gluten proteins

In this study, edible films were prepared with different wheat gluten (GLU) and gelatin (GEL) ratios by the solvent casting technique using glycerol (GLY) or sorbitol (SOR) as plasticizers. Fatty acids (caproic, caprylic, capric, lauric, myristic or palmitic) were also added to a previously selected GLU/GEL/sorbitol film, and the effect of GLU:GEL proportion and type of fatty acid on the film properties were tested. Films plasticized with GLY presented a more significant reduction in the elongation at break (EB). In contrast, films plasticized with SOR did not show a significant difference in the EB. The film's water vapor permeability (WVP) and acid solubility increased with increasing proportions of GEL while the water solubility was decreased. On the other hand, the elongation at break of the films decreased with increasing GEL content, which may be associated with its more rigid structure. The addition of fatty acids resulted in lower WVP and the plasticizing effect was dependent on the degree of interaction with the proteins of the film (identified by thermal analysis). The GLU:GEL proportion and the type of fatty acid affect the film properties (mechanical, solubility, opacity, water vapor barrier), allowing the development of new materials with different and useful functional properties according to the desired applicationThe research leading to these results has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 712949 (TECNIOspring PLUS) and from the Agency for Business Competitiveness of the Government of CataloniaPostprint (published version

Effect of a gelatin-based edible coating containing cellulose nanocrystals (CNC) on the quality and nutrient retention of fresh strawberries during storage

Strawberry is a non-climacteric fruit with a very short postharvest shelf-life. Loss of quality in this fruit is mostly due to its relatively high metabolic activity and sensitivity to fungal decay, meanly grey mold (Botrytis cinerea). In this study, the ability of gelatin coatings containing cellulose nanocrystals (CNC) to extend the shelf-life of strawberry fruit (Fragaria ananassa) over 8 days were studied. The filmogenic solution was obtained by the hydration of 5 g of gelatin (GEL) in 100 mL of distillated water containing different amounts of CNC dispersion (10 mg CNC/g of GEL or 50 mg of CNC/g of GEL) for 1 hour at room temperature. After this period, the solution was heated to 70 ºC and maintained at this temperature for 10 minutes. The plasticizer (glycerol) (10g/100g of the GEL) was then added with constant, gentle stirring in order to avoid forming air bubbles and also to avoid gelatin denaturation until complete homogenization. Strawberries (purchased at the local market) were immersed in the filmogenic solution for 1 minute and after coated were dried at 15 ºC by 24 hours. The strawberries were then kept under refrigeration and characterized in terms of their properties (weight loss, ascorbic acid content, titratable acidity, water content). The results have shown that samples covered with GEL/CNC had a significant improvement in its shelflife. For instance, for the control sample (without coating) the weight loss after 8 days of storage was around 65%, while covered samples loss in the range of 31-36%. Edible coating was also effective in the retention of ascorbic acid (AA) in the strawberries, while control sample presented a fast decay in the AA content, covered samples showed a slow decay in the AA concentration. Moreover, the use of GEL/CNC edible coating had an antimicrobial effect in the fruitsPostprint (published version

Phase I/II trial of gemcitabine plus cisplatin and etoposide in patients with small-cell lung cancer

Objective: The objectives of this phase 1/11 study were to define the maximum tolerated dose (MTD), safety, and activity of cisplatin, etoposide, and gemcitabine (PEG) in the treatment of previously untreated patients with small-cell lung cancer (SCLC). Patients and Methods: Chemonaive patients received fixed doses of gemcitabine (1000 mg/m(2) on days I and 8) and cisplatin (70 mg/m(2) on day 2) and escalating doses of etoposide (starting dose of 50 mg/m(2) on days 3,4, and 5) every 3 weeks. No prophylactic granulocyte colony-stimulating factors were used. Results: From September 1998 to April 2000, 56 patients with limited- or extensive-stage SCLC were enrolled and received a total of 235 cycles. Two different etoposide doses were tested in eight patients. At the second level (75 mg/m(2)), two out of two patients experienced dose-limiting toxicities (neutropenia and thrombocytopenia) and no further dose-escalation was attempted, thus an etoposide dose of 50 mg/m 2 was defined as the MTD. In the subsequent phase 11 evaluation, 48 additional patients were enrolled, for a total of 54 patients treated at the MTD. Grade 3/4 neutropenia and thrombocytopenia occurred in 66.7 and 53.7%,, of patients, respectively. Non-hematologic toxicity was mild, with grade 3 diarrhea and fatigue as the main side effects. Two patients died of neutropenic sepsis (one at 75 mg/m(2) and the other at So I n g/In 2 etoposide). Ten complete and 29 partial responses were reported, for an overall response rate of 72.2% (95% confidence interval, 56.6-85.0%). The median duration of response and median survival were 8.0 and 10 months, respectively, with a 1-year survival probability of 37.5%. Conclusions: he combination of PEG is feasible and well tolerated as front-line chemotherapy in SCLC. A randomized comparison of this triplet is underway. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved

Antimicrobial activity of bleached cattail fibers (Typha domingensis) impregnated with silver nanoparticles and benzalkonium chloride

Typha domingensis (Cattail) fiber is a significant natural resource, abundant in cellulose. The study reports the useful utilization of T. domingensis fiber for physicochemical impregnation of silver nanoparticles and benzalkonium chloride, in the development of a material with antimicrobial activity. The fibers were pre-treated with alkaline hydrogen peroxide (bleaching) for partial removal of lignin, pectin and waxes. Subsequently treated in a solution of different concentrations of benzalkonium chloride and Tollens' reagent. The new materials obtained were carefully investigated for their structure and thermal stability, morphology and susceptibility to antimicrobials (Staphylococcus aureus, Escherichia coli, Salmonella typhimuruim, and Salmonella enteritidis). Fourier transform infrared spectra showed the presence of benzalkonium chloride. The morphology analysis showed the silver nanoparticles on the surface of the bleached fibers. The susceptibility profile to antimicrobials was confirmed by the formation of inhibition halos (¿11.26¿mm). Based on the properties of the materials obtained, it can be concluded that the modified cattail fibers have the potential to be used as a functional filler, or coating, in the development of antimicrobial compositesPostprint (published version