Abstract In this study we evaluated the use of eucalyptus lignin as a stabilizer in combination with other stabilizers in a vulcanized elastomeric based on natural rubber. The stabilizers tested were 6PPD (N-1,3-dimethyl-butyl-N'-phenyl-p-phenylenediamine), TMQ (oligomerized 2,2,4-trimethylquinoline), paraffin wax and eucalyptus lignin. At predetermined time intervals, samples were taken from aging conditions and the mechanical properties and additive content were determined. The sample with a combination of wax and lignin in the same formulation showed the greatest resistance to oxidative degradation. In samples with only one stabilizer, the migration test indicated greater diffusion of lignin to the surface. Samples exposed to thermo-oxidative aging showed greater loss in the mechanical properties of tear strength and 6PPD consumption. In the accelerated aging with ozone, all showed a behavior more resistant to aging. We concluded that lignin can be used as a substitute for synthetic stabilizers, without impairing the performance of natural rubber compounds.

Abstract Presently, there are significant research efforts being undertaken to produce bio-based chemicals in a cost-effective way. The polymer chemists and engineers are no exception to this. Additives for polymers correspond to a large section of the plastics market and bio-based products can substitute many of them. The scientific literature has a large number of publications focusing on the preparation and testing of bio-based polymer additives; however, the small number of products that reach the market, which are bio-based, does not reflect this. In terms of the global market, the environmentally friendly appeal of bio-based additives alone is not sufficient; the bio-based product must have similar or better performance than the oil-based and be comparable or lower in cost than the existing products. In this review, we focus on bio-based polymer additives that have already reached the market or have a real possibility of reaching the market in a cost-effective way.

Abstract Off-site measurements of the dimensions of extruder screws are used to monitor their wear. This wear causes the presence of metals in the processed polymer. We detected the presence of iron in polymers processed with corrosive contaminants or abrasive fillers. To this end we processed poly(ethylene terephthalate), PET, pure or contaminated with poly(vinyl chloride), PVC, and other thermoplastics reinforced with glass fibers, talc or vegetal fibers, and analyzed the metals in the processed materials by X-ray fluorescence spectroscopy. We show that iron dispersed in the polymer melt is generated by corrosion from the PET contaminated with PVC and by erosion from abrasive fillers. The contents of iron in the extruded polymers clearly indicate equipment wear. This contaminant acts as a polymer pro-degradant, decreasing its lifetime. Additionally, we show that the lower concentration of iron for composites with vegetal fibers indicates a lower abrasion in comparison to talc and glass fibers.

O interesse por polímeros biodegradáveis tem aumentado devido ao baixo impacto ambiental dos mesmos. No entanto, muitos desses produtos disponíveis no mercado são frágeis, difíceis de processar e têm alto custo. Uma das técnicas para superar essas deficiências é através de blenda com outros polímeros. Este trabalho avaliou várias composições de blenda PHB/PP, utilizando-se um aditivo pró-degradante deste último, de forma a tornar a formulação oxibiodegradável em solo simulado (ASTM D6003). O comportamento mecânico, térmico e químico de corpos de prova de tração das amostras enterradas foi acompanhado através de medidas de resistência à tração, DSC, FTIR, GPC e SEM. Parte das amostras foi envelhecida em estufa a 90 ºC por 10 dias, de forma a acelerar a oxidação do PP pelo aditivo. A blenda composta por 56 wt% de PP / 40 wt% de PHB / 3 wt% de GMA / 1 wt% de MnSt foi a mais susceptível à oxibiodegradação, tendo reduzido depois de 180 dias de enterramento em solo, a tensão de tração em 40%, alongamento na ruptura em 46% e a massa em 24%. Estes valores foram superiores ao próprio PHB puro e o efeito sinérgico ocorrido nestas blendas foi atribuído à aceleração da degradação do PHB pelo PP oxidado.

The interest in biodegradable polymers has increased because of their environmental advantages. Blending them with other polymers is one of the techniques currently employed to overcome their brittleness, poor processing and cost. This work evaluated different blend compositions of PHB/PP, using a pro-degrading additive for this latter, to make the formulation prone to oxo-biodegradability in simulated soil (ASTM D6003). The mechanical, thermal and chemical behavior of buried injection molded tensile bars was monitored through measurements of tensile strength, DSC, FTIR, GPC and SEM. Part of the samples was oven aged at 90 ºC for 10 days in order to accelerate the PP oxidation by the additive. The blend made of 56 wt% of PP / 40 wt% of PHB / 3 wt% of GMA / 1 wt% of MnSt was the most susceptible to oxo-biodegradation, having reduced after 180 days of burring in soil, its tensile stress by 40%, tensile elongation by 46% and mass by 24%. These values were even higher than the ones for the pure PHB. This synergic effect was attributed to the acceleration of PHB degradation by the oxidized PP.

Neste trabalho um eletrólito polimérico nanocompósito baseado em uma argila do tipo montmorilonita e um polímero derivado do poli(óxido de etileno) plastificado com g-butirolactona foi preparado e caracterizado. Apesar da adição de plastificantes à matriz polimérica aumentar a condutividade iônica de eletrólitos poliméricos, a adição de grande quantidade desses aditivos compromete as propriedades mecânicas do sistema, de tal maneira que o ganho em condutividade não compense a perda na natureza "sólida" do meio eletrolítico. Filmes do eletrólito nanocompósito contendo diferentes concentrações de argila foram caracterizados por análise térmica e mecânica e por espectroscopia de impedância eletroquímica. A adição de montmorilonita resultou numa melhora das propriedades mecânicas do eletrólito, além de contribuir para um aumento da condutividade iônica do sistema. O eletrólito compósito foi aplicado em uma célula solar de TiO2/corante pela primeira vez, resultando em um dispositivo com eficiência superior a 3% sob irradiação de 10 mW cm-2.

In this work we report for the first time the preparation and characterization of a novel composite polymer electrolyte based on montmorillonite clay and a poly(ethylene oxide) derivative plasticized with g-butyrolactone and its application in dye sensitized solar cells. Although the plasticizers enhance the ionic conductivity of the polymer electrolytes, they compromise the mechanical stability of the whole system and make the practical application of these devices difficult. Films with composite polymer electrolytes containing different clay content were analyzed by thermal and mechanical analysis and electrochemical impedance spectroscopy. We observed that the addition of the inorganic particles to the polymer matrix promotes not only an enhancement in the mechanical properties but also contributes to the increase the of ionic conductivity of the system. A solid-state dye-sensitized solar cell was assembled for this first time with the electrolyte containing montmorillonite clay, displaying efficiencies higher than 3% at 10 mW cm-2.