Dayanne Diniz Souza Morais

Influence of processing variables on the mechanical behavior of HDPE/clay nanocomposites

Nanocomposites were processed using the technique of melt intercalation, starting from a concentrated polar compatibilizer/organoclay (PE-g-MA/organoclay) prepared in an internal mixer. The concentrate was incorporated into the matrix of HDPE by two methods: I) counter-rotating twin-screw extruder and II) co-rotating twin-screw extruder, using two screw profiles (ROS and 2KB90). After extrusion, the specimens of the extruded composites were injection molded. The X-ray diffraction (XRD) technique was used to analyze the degree of expansion of the prepared clays. To analyze the degree of exfoliation of obtained nanocomposites, XRD and TEM (transmission electron microscopy) were used. The influence of processing variables on mechanical properties was studied through the behavior of the modulus and tensile strength of nanocomposite systems. By XRD and TEM, it was seen that the clay was well dispersed in the matrix and the presence of intercalated and partially exfoliated hybrid structure for nanocomposites was observed when the systems were prepared in counter-rotating twin-screw extruder. A similar behavior was observed in the use of screws (2KB90 or ROS) of the nanocomposites, with a reduction in modulus and tensile strength. Although the mixing process by extruding be the most common industrial practice, and also it is the preferred strategy for the preparation of polymer nanocomposites, much of the literature was directed to the study of chemical modification of clay, type and level of compatibilizer, in order to maximize the compatibility between clay and the polymeric matrix. On the other hand, studies about the role of the processing and configurations of screws are relatively scarce. The main motivation of this work was to expand and to contribute to spread a better understanding of the effects of processing to obtain polymer nanocomposites.

Study of Morphology Membrane of Polymeric Nanocomposites Obtained by Phases Inversion

In this work, were obtained nanocomposite membranes polyamide66/Paraíba bentonite clay, treated with a quaternary ammonium salt in order to make it organophilic. The membranes were prepared as thin films using the technique of phase inversion from the nanocomposites obtained by solution. The membranes were characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetry (TG) and scanning electron microscopy (SEM). By means of X-ray diffractogram, it was revealed that the membranes remained organically treated clay presented exfoliated and/or partially exfoliated structure. From curves of DSC and TG, it was observed that membrane of PA66 with 3% w/w of with treatment clay showed higher thermal stability compared with the same content of clay without treatment. From the SEM photomicrographs, there was a selective layer (skin filter) on top and one porous layer at the bottom of all membranes studied. Moreover, it was verified that the presence of clay provided a significant structural modification in the membranes of polymer nanocomposites.

Hydrolytic and Thermal Degradation of PCL and PCL/Bentonite Compounds

Poly(Ɛ-caprolactone)/montmorillonite (PCL/MMT) and Poly(Ɛ-caprolactone)/organo-modified montmorillonite (PCL/OMMT) compounds at 3% w/w clay content were prepared by melting mixing. The effect of MMT and OMMT on the degradability of PCL injected specimens was investigated in vacuum at 40oC for up to 45 days and in aqueous medium at 40oC for up to 45 days. Selected specimens were collected after 15, 30 and 45 days of exposure. Microstructural changes were monitored during the degradation experiment by means of melt flow rate (MFR), weight loss, X ray diffraction (XRD), mechanical properties, and scanning electron microscopy (SEM). PCL and its compounds revealed not to be prone to hydrolytic degradation with similar results for MFR of samples exposed in vacuum and water. Gain and loss of weight were observed during experiments, probably due to swelling mechanism taking place in two stages, with the amorphous phase being the first to be swelled followed by the crystalline one. By XRD a new peak corresponding to (002) plane was evident for PCL/OMMT. PCL proved to be resistant to degradation since experiments carried out in vacuum or in aqueous medium for up to 45 days were not enough to affect the mechanical integrity of PCL samples.

Analysis of the Efficiency of Surface Treatment of Bentonite Clay for Application in Polymeric Membranes

The bentonite clay fillers are mostly used for the development of nanocomposites, due to having characteristics which provide to obtain in nanometric particles. The bentonite clay was treated with an ammonium quaternary salt to modify it to organophilic clay. The polymeric membranes and nanocomposites were prepared using the phase inversion technique. The bentonite and organophilic clays were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The membranes were characterized by XRD. The results of XRF, XRD and FTIR confirmed the presence of quaternary ammonium salt in the organoclay structure. The XRD diffraction patterns of nanocomposites membrane showed exfoliated and/or partially exfoliated structure. According to the obtained results, it could be seen that the treatment performed on the surface of the clay was quite promising and efficient to be added as nanofillers on polymeric membranes.

Toughening of polystyrene using styrene-butadiene rubber (SBRr) waste from the shoe industry

The vulcanized rubber waste from the shoe industry causes environmental damage when it is incinerated or inappropriately discarded, turning this into a problem of major concern. Therefore, this study had as the main objective the Polystyrene (PS) toughening using different contents of white vulcanized styrene-butadiene rubber (SBRr) waste produced in the shoe industry. The mixtures were initially prepared in a co-rotational double screw extruder and, thereafter, the extruded granules were injection molded. Analyzed were the rheological, mechanical, thermomechanical properties and morphology of the produced blends. The rheological results showed a viscosity increase as the SBRr concentration was augmented, leading to a higher stability when compared to pure Polystyrene. Verified was an increase of impact resistance of 189% to the blend that contained 50% of SBR rather than pure Polystyrene. On the other hand, the traction properties, hardness Shore D, thermal deflection temperature (HDT) and Vicat softening temperature of the blends tended to decrease when compared to pure Polystyrene results. However, as this SBR waste is made up of a complex mixture of SBR, filler, processing additions, curing agents and stabilizers, it probably acted in the sense of not causing such a drastic reduction of the properties, even using a high concentration of SBRr waste. The morphologies obtained with the SEM method (Scanning Electronic Microscope) were quite different and typical of immiscible blends. The results show that it is possible to obtain a new material with good properties, valuing a discarded industrial waste and avoiding environment aggression.

Preparation of Poly(Lactic Acid)/Bentonite Clay Bio-Nanocomposite

Recent advances in biodegradable polymers have attracted a great interest not only in traditional areas such as biomedical and pharmaceutical industry, but also in packaging applications, articles and injected membranes. The aim of this work was to produce bio-nanocomposites poly (lactic acid) - PLA with bentonite clay. The bio-nanocomposites were produced by melt intercalation with incorporation of 1 to 3 wt% of organoclay. The degree of dispersion of clays in the polymer, and consequently the structure of bio-nanocomposites produced was evaluated by X-ray diffraction (XRD), and the thermal properties were studied by differential scanning calorimetry (DSC). XRD results indicated the formation of intercalated structures. It was observed the appearance of crystalline melting double peaks in bio-nanocomposites PLA.

Study of Nanocomposites of Polyamide 6.6/National Bentonite Clay

Polymers nanocomposites are a class of materials where inorganic substances with nanometrics dimensions are modified and used as dispersed loads in polymers matrices. In this work, polyamide 6.6 was chosen because of its excellent chemical, mechanical and thermal properties. The bentonite clay was treated with quaternary ammonium salt (Cetremide®) to make it organophilic and to improve the interaction with the polymer matrix. It was verified by the Torque Rheometry that the system with salt presented a bigger torque in relation to the torque of the system with untreated clay and pure polyamide 6.6. The nanocomposites presented an exfoliated and partially exfoliated structure, as evidenced by XRD. By DSC, it was observed that the treated clay increases the decomposition temperature of the nanocomposite.

Effect of Hydrolytic Degradation on Mechanical Properties of PCL

This work investigated the effect of hydrolytic degradation on mechanical properties in tension and impact strength of poly (Ɛ-caprolactone) (PCL). PCL specimens produced by injection processing were submersed in water and exposed at 40°C into a vacuum heater. The specimens were collected from the heater after periods of 15, 30 and 45 days, respectively, followed by mechanical tests. According to the data acquired for Elastic Modulus, specimens exposed for 15 and 45 days presented a decrease of 9.65% and 13.65%; for Yield Stress a decrease of 9.08% and 10.38% was observed at same period of time compared with unexposed specimens. Concerning the Elongation at Break tests unexposed PCL reached the maximum limit of machine without fracturing while exposed specimens had their elongation at break capability decreased. Unexpected results were observed for the specimens exposed for 30 days which presented an increase of 3.43%, 3.12% and 5.88% for Elastic Modulus, Yield Stress and Strength at Break. Impact Strength presented similar trend to that of mechanical properties in tension. It is suggested that these trends are connected with morphological changes which took place in the amorphous and crystalline phases of PCL during hydrolytic degradation.

Preparation of Biodegradable Polymer Nanocomposites and Vermiculite Clay by Melt Intercalation Technique

The consumption of plastic products over the years has been producing large numbers of waste material, which accumulate by landfill generating considerable environmental problems. Among biodegradable polymers, there is the PHB (poly-3-hydroxybutyrate), which has attracted more attention once it is obtained from renewable sources. This study aimed to prepare biodegradable nanocomposites by melt intercalation of PHB polymer in the natural vermiculite clay, in the ratios of 1, 3 and 6 wt%. The nanocomposites were obtained in an internal mixer coupled to a torque rheometer by Haake-Blucher, operating at 170°C, 50 rpm for 10 minutes. The material was triturated and then films were molded by compression under the conditions: 3 tons at 170°C for 3 minutes. The films were characterized by X-ray diffraction (XRD) and Infrared (FTIR). These analyzes were used to evaluate the intercalation and / or exfoliation of nanocomposites. In general, results indicated changes in structure as a function of clay content employed in the systems of PHB / vermiculite.

Modification of Brazilian Bentonite Clay for Use Nano-Biocomposites

Biopolymers are a growing research issue since they appear as a solution to the emerging environmental concerns that have risen in recent years. They represent an interesting alternative to synthetic polymers for a short-life range of applications. Recently, great attention has been paid to the association between biopolymers with nanosized llers, in particular, to those in which layered silicates are dispersed at a nanometric level in a biopolymer matrix. Surch materials called nanobiocomposites. In this work, Brazilian bentonite clay was organophilized with three organic intercalants by ion-exchange reactions for use in nanobiocomposites. The clay was characterized by X-ray Fluorescence (XRF), X-ray Diffraction (XRD), Fourier Transform infrared spectroscopy (FTIR) and Thermogravimetry (TG). The XRD results confirmed the increased spacing basal because the presence of intercalant molecules in the clay, too confirmed by FTIR. The organoclay showed greater weight loss than the clay without modification. The structure had produced nanobiocomposites exfoliated and/or partially exfoliated.