Flaxseed gum (FG)-based films were developed with the addition of glycerol as a plasticizer and glutaraldehyde as a crosslinking agent. HCl was added to improve crosslinking and decrease the hydrophilicity of the matrix. Different cellulose nanocrystal (CN) amounts were used as reinforcements in the optimum FG formulation. The crosslinking process at pH 3.5 led to a lower solubility of FG in water (from 100% to 53%) and an increase in thermal stability (from 160 ºC to 209 ºC). FTIR analysis confirmed a reduction in the -OH band due to crosslinking between the hydroxyl groups of FG. A diffuse diffraction pattern was observed for all FG films. The addition of 4% w/w of CN contributed to reduction of water solubility (from 53% to 20.8%) and absorption (from 21.9% to 6.8%). Finally, an improvement was observed in the tensile mechanical properties in the nanocomposites, showing satisfactory results for the proposed formulations, mainly with 8% w/w of CN added to the matrix. Overall, this study demonstrated that FG/CN nanocomposites are promising materials to be use as a sustainable biopolymer for application as bioplastics.

Nanocompósitos de LLDPE/argila montmorilonita e LLDPE/niobato organofilizado foram obtidos através da diluição de um concentrado da respectiva carga em uma extrusora dupla rosca obtendo-se concentrações finais de 1,5 a 10,0% em carga. No presente estudo utilizou-se o ensaio mecânico de tração e o de permeação ao vapor de água e ao oxigênio para caracterizar estes nanocompósitos. No ensaio mecânico de tração observou-se aumento no valor do módulo elástico e diminuição no valor da tenacidade com o aumento da concentração da argila montmorilonita, o que era esperado devido à rigidez da carga. Comportamento semelhante também foi observado no caso dos nanocompósitos de niobato organofilizado, porém de maneira menos acentuada devido à estrutura química do niobato de potássio. Com auxílio do MEV/FEG observou-se que a distribuição da argila é superior a do niobato organofilizado para concentrações inferiores a 10,0% de carga. No ensaio de permeação ocorre diminuição no valor de permeabilidade com o aumento da concentração da argila montmorilonita para ambos os gases utilizados. Na presença do niobato organofilizado observa-se diminuição, seguido de aumento no valor da permeação com o aumento da concentração da carga para ambos os gases utilizados. Além disso, observou-se que a polaridade do gás utilizado é um fator importante no processo de difusão através do nanocompósito.

Linear low density polyethylene-montmorillonite clay and linear low density polyethylene-organophilic niobate nanocomposites were obtained from dilution of masterbatch with 20% w/w of fillers in the LLDPE matrix by melt intercalation using a twin-screw extruder, obtaining nanocomposites with 1.5% up to 10.0% w/w of filler. In this study mechanical and water vapor and oxygen permeation tests were used to characterize the nanocomposites. In mechanical tests an increase of modulus values and decrease of toughness value by increasing concentration of montmorillonite clay were observed. The behavior of LLDPE-organophilic niobate nanocomposites was similar to LLDPE-montmorillonite clay nanocomposites but softer due to hexaniobate structure. The distribution of the organoclay is more homogeneous than organophilic niobate to concentrations below 10.0% filler using the SEM/FEG. It is possible to see a decrease in the permeability value with increasing concentration of montmorillonite clay for both gases used. In the LLDPE-organophilic niobate nanocomposites a decrease of permeability value occurs followed by an increase of permeability value for both gases used, with increasing concentration of organophilic niobate. Furthermore, it was observed that the polarity of the gas used is an important factor in the diffusion process through the nanocomposite.

Poly(butylene terephthalate) (PBT)/ acrylonitrile-butadiene-styrene (ABS) terpolymer blends were prepared in a twin screw extruder and the use of methyl methacrylate-glycidyl methacrylate-ethyl acrylate (MGE) terpolymer as compatibilization additive was evaluated. The effect of different screw profiles and mixing conditions were evaluated on the crystallization of the blends. Differential scanning calorimetry (DSC) was used to evaluate melting and crystallization behaviors of the PBT/ABS blends. The binary PBT/ABS blend has shown a double melting peak when cooled at lower cooling rates, mainly due to its melt-recrystallization during the heating up step. ABS has not affected the melting characteristics of neat PBT. The presence of MGE, as a reactive compatibilizer, in the PBT/ABS blends has reduced its heat of fusion and has partially inhibited its melt-recrystallization under heating. As result, it has prevented the occurrence of double melting peak. The epoxy functional groups of the MGE may react in situ to the carbonyls and hydroxyls end groups of the PBT molecules, thereby hindering the mobility of PBT molecules during the crystallization process due to its grafting to the compatibilizer molecules. The melt mixed blends prepared at lower feeding rate have shown a higher degree of crystallinity for the PBT/ABS blend, probably due to degradation of PBT caused by longer residence time in the extruder. The highest shear stress imposed to the blends at higher screw speed increased the degree of crystallinity of PBT, also due to its degradation.

O aumento de ramificações e da massa molecular em polímeros essencialmente lineares influencia as propriedades no estado fundido desses polímeros. Este comportamento foi observado pela análise dos dados de resistência do fundido, extensibilidade e do conteúdo de gel em amostras de Polipropileno linear (iPP) modificado. A modificação foi obtida utilizando agentes modificadores (monômeros multifuncionais) e radiação gama. Os agentes modificadores empregados foram o Tri-metilol-propano-tri-acrilato (TMPTA) e o Tri-alil-cianurato (TAC). O TMPTA demonstrou ser um agente mais eficiente para a promoção do iPP modificado (reticulado/ramificado), uma vez que o produto final apresentou um valor maior da resistência do fundido do que o material com TAC. No entanto, ambos modificam a morfologia original do iPP constatada pelo deslocamento do pico de fusão para temperaturas menores, pelo aumento da temperatura de cristalização (Tc) e pela presença de múltiplas endotermas.

It well known that in essentially linear polymers the properties of the melt polymers change with increasing molecular weights and degrees of branching. This behavior was observed from data analysis of the strength of the melt polymer, drawability and gel content. In this work isotactic polypropylene (iPP) in the presence of multifunctional monomers was irradiated with gamma radiation. The monomers used were Trimethylolpropane triacrylate (TMPTA) and Triallylcyanurate (TAC). iPP with TMPTA showed the highest strength in the melt and gel content, followed by TAC. It was demonstrated that TMPTA is a powerful agent to crosslinking and branching iPP. Both monomers modified the original morphology of the iPP, the melting peak shifts toward lower temperature and crystallization temperature increased during cooling after the first run. Double melting peaks were observed in the DSC thermograms, which were caused by a double lamellar thickness.

Simulations have shown that temperature changes during the growth of lamelae/ribbons of a polymer crystal induce alterations in the thickness of the lamelar crystal. Therefore, the lamelae/ribbons would melt at different temperatures. This is demonstrated experimentally here for spherulites of Isotactic Polystyrene (iPS). The results were obtained following the melting process of selected spherulite structures through temperature scanning. The samples, in which chosen spherulites were observed, were crystallized from the melting state at successive crystallization temperatures. Observations of these spherulite melting processes were made with an optical polarized microscope, using a hot stage to apply the temperature scan.