Diego Piazza

This study investigates scalable methodologies for incorporating graphene nanoplatelets (GNPs) into styrene‐butadiene rubber (SBR) latex, comparing powder form (GNP) and masterbatch (MB), with and without dodecyltrimethylammonium bromide (DTAB) surfactant. The formulations (0.5% w/w GNP or MB; DTAB in a 1:1 ratio) adhere to the standards outlined in ASTM D3185‐09. The curing process involves mechanical agitation, coagulation, drying, milling, and vulcanization at 160°C. The incorporation of DTAB into MB results in a 78% reduction in the optimum vulcanization time ( t ₉₀ ) compared to the control (CSBR) and an approximate 78% increase in the maximum torque ( M _H ). The hardness of CSBR/MB/DTAB increased by 5.5% compared to CSBR, and the permanent deformation decreased by 28%. The tensile strength of CSBR/MB increased by 74% in comparison with CSBR, while CSBR/GNP/DTAB demonstrated an increase of 50%. The thermal conductivity of CSBR/GNP exceeds that of CSBR by 15.2%. Subsequent to thermal aging, CSBR/GNP/DTAB demonstrates enhanced resistance: The data demonstrate a 54.5% increase at 7 days and a 45.4% increase at 14 days in comparison to CSBR. It can be concluded that the combination of masterbatch and DTAB surfactant optimizes GNP dispersion in SBR, making industrial processes without ultrasound viable.

Laminated polymer composites are widely used in ballistic barriers where polyethylene can be applied. The mechanical properties of polymers can be improved with the addition of nanofillers. Therefore, this work evaluates the effect of the combination of montmorillonite Cloisite 30B (OMt) and graphene (Gr) on the dynamics compression properties obtained from a split‐Hopkinson pressure bar (SHPB) test for nanostructured maleinized high‐density polyethylene (HDPE). The nanofillers are incorporated into the polymeric matrix in its molten state, and their dispersion is evaluated through x‐ray diffraction and transmission electron microscopy analyses. Thermal analysis, including differential scanning calorimetry and thermogravimetric analysis are performed. Additionally, the viscoelastic behavior of the materials is studied from the results of storage and loss modulus obtained by dynamic‐mechanical analysis. Under the SHPB test conditions, it is possible to evaluate the material stress–strain curve, identifying its yield point, compressive strength, and deformations to calculate the elastic stiffness and toughness of the material. The nanocomposite with 3% OMt and 0.75% Gr (wt.%) shows the highest average compressive strength and toughness values. Furthermore, this sample shows similar T_peak temperature, improved crystallinity index, storage, and loss modulus, with similar glass transition temperature compared to the HDPE sample.

Heterogeneous photocatalysis represents a solution for several environmental problems. However, achieving photocatalyst separation from reaction media on a large scale remains a challenge, one that might be overcome by the immobilization of photocatalysts into supports. To this end, composites of polyvinylidene fluoride and zinc oxide (ZnO) were prepared by three different techniques: solution mixing (SM) followed by Nonsolvent Induced Phase Separation; and melt blending at both low‐ and high‐shear rates (LS and HS) in a rheometer and mixing chamber, respectively, to compare the resultant morphology in photocatalysis. Photocatalytic efficiency was assessed by methylene blue (MB) discoloration in a batch reactor liquid phase and by resazurin (RZ) reduction. The changes promoted by nanoparticle inclusion, processing conditions and UV effect were demonstrated by FTIR‐ATR, XRD, DSC, and SEM. Results showed that ZnO incorporation was successful under all processing conditions, providing effective photocatalytic composites. However, samples prepared by SM had a twofold increase in discoloration efficiency and fourfold increase in surface photoactivity, when compared with LS or HS‐produced samples, explained by its higher porosity of 88% ± 1.3%. The covering of the photocatalyst surface was also evident on SEM analysis for melt blended samples, further contributing to reduction in their photocatalytic activity.

Despite the efforts of the scientific community, carrying out photocatalyst immobilization so that industrial application of photocatalysis becomes economically feasible is still a challenge to be overcome. In this work, polyvinylidene fluoride (PVDF)/ZnO composites were prepared by solution mixing based on solid knowledge of membrane technology and with the help of a powerful experimental design for systematic evaluation of the interaction among variables. A strategy for variable screening was used, followed by a complete evaluation at two levels, leading to predictive models. As a result, photocatalyst amount, pore agent concentration, and wet thickness were the most significant in the target molecule discoloration. With this, it was possible to obtain a 40 and 186% enhancement in photocatalytic efficiency compared to previous results and simple photolysis, respectively. Finally, the samples were characterized by FTIR‐ATR, XRD, and SEM and chemical, crystalline and morphological differences were observed both with nanoparticle and pore agent incorporation. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48417.

Polypropylene (PP) and polyethylene (PE) are two of the most widely used polymers in the world, and consequently the main polymer waste that contributes to the pollution of the oceans. Because they are considered inert to degradation, such waste becomes a threat to marine life. In this study, it was possible to collect data on the recyclability of PP and PE waste collected from the Great Pacific Garbage Patch. First, the degradation conditions suffered by these materials were evaluated. The Fourier transform infrared spectroscopy assays presented different levels of carbonyl in different layers below the surface of each material and scanning electron microscopy tests showed cracks and microorganisms. The mechanical and rheological properties were evaluated in order to evaluate the recyclability of samples exposed to the marine environment. From the study, it can be concluded that, despite the levels of degradation of the samples, it is possible to obtain satisfactory properties for mechanically recycled products. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48215.

The modification of a thermoplastic elastomer by cross-linking or plasticizing allows the manipulation of material properties for different applications. Cross-linking additives promote the increase of mechanical, thermal, and rheological properties, while the use of plasticizers has the opposite effect, giving the material soft properties. Such characteristics affect the development of polymeric foams directly, where the polymer matrix properties have large influence on the foaming capacity and morphology of the cells. This study investigated the use of cross-linking and plasticizer additives in ethylene-co-vinyl acetate copolymer, as well as its influence on the foaming capacity. The increasing content of cross-linking additive impacts on formation of preferentially closed cells, with high cell density and smaller size, while using plasticizers a higher occurrence of cell deformation and open cells was verified. The low formation of cells due to the decreasing of the polymer matrix thermal stability allows gases to escape during the processing and favors the cell coalescence effect. The foaming temperature is directly related to the polymer melt temperature, so, for the plasticizer-added samples, lower temperatures were required during the foaming than the samples with the cross-linking agent.

Three different ultrahigh‐molecular‐weight polyethylene (UHMWPE)–clay nanocomposites (Muscovite, Cloisite 30B and amphiphilic clay/carbon nanofibers) were investigated with the nanocomposite nanomorphology studied before and after dynamic mechanical compressive tests at high strain rates. Their material structure and thermal properties were investigated using techniques such as step‐scan differential scanning calorimetry, split Hopkinson pressure bar, synchrotron small angle X‐ray scattering (SAXS), and dynamic mechanical analysis. Results were associated with morphological changes observed after deformation. chemical vapor deposition (CVD)‐modified nanocomposite, due to the molecular bonding and the extra functional groups, is designed with crystalline structures with fewer defects and higher stability. The increase in particulate/polymer interactions observed for the CVD‐modified material decreased the elongation in the quasi‐static test. However, the dynamic mechanical behavior contradicted the quasi‐static behavior because at very high strain rates there was not sufficient time for the interlamellar and intralamellar defect facilitated plastic flow and the material transitioned through the glassy state. The SAXS results show that deformation strongly induced changes in the UHMWPE and UHMWPE–clay nanocomposite morphology. SAXS indicates that CVD‐modified samples became more compact and dense, thus corroborating the formation of additional secondary bonds between structures and/or the carbon nanofibers alignment. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2019,136, 47094.