Mechanochemical treatment in high-shear thermokinetic mixer as an alternative for tire recycling

This publication highlights the use of a high-speed thermokinetic mixer as an alternative to recycling ground tire rubber (GTR) using mechanochemical treatment. The GTR initially had a gelled fraction of 80% and presented a reduction of up to 50% of gel fraction in the most intensive condition (5145 rpm, n2 ). The processing condition at the lowest speed (2564 rpm, n1 ) resulted in greater selectivity in chain scission (K~1). However, in the most intense processing condition (10 min to n2 ), more significant degradation was observed via random scission, reduction in the glass transition temperature, Tg (11 ◦C), increase in the soluble polymeric fraction, and a more significant reduction in the density of bonds occurs. The artificial neural network could describe and correlate the thermal degradation profile with the processing conditions and the physicochemical characteristics of the GTR. The n2 velocity resulted in the formation of particles with a smoother and more continuous surface, which is related to the increase in the amount of soluble phase. The approach presented here represents an alternative to the mechanochemical treatment since it can reduce the crosslink density with selectivity and in short times (1–3 min)

Effect of dynamic crosslinking on phase morphology and mechanical properties of polyamide 6,12/ethylene vinyl acetate copolymer blends

The dynamic crosslinking of polyamide 6,12 and ethylene vinyl acetate (PA6,12/EVA) blends in the mixing chamber of a torque rheometer was investigated. EVA was selectively crosslinked within the PA6,12 phase through free radical reactions using dycumil peroxide. The degree of EVA crosslinking in the PA12,6/EVA materials was estimated based on the gel content (insoluble EVA fraction). The PA6,12/EVA phase morphology was investigated by scanning electron microscopy. The mechanical properties were investigated by determining the tensile strength and hardness. The half-life time ( ) for homolytic scission of the dcumil peroxide (DCP) was ~6s, and this time is longer than the dispersion time of the DCP in the blends. The addition of DCP resulted in increased torque values due to specific crosslinking in the EVA phase. For the pure EVA and its blends with PA6,12 the stabilized torque values increased proportionally with the amount of DCP in the system, due to a higher degree of crosslinking of the elastomeric phase. The gel content of the dynamically crosslinked blends increased with the amount of DCP incorporated until 4 phr. At 1 phr the gel content value was 2.6wt.%, while at 4 phr it was 17wt.%. For the polymer blend with 8 phr of DCP a lubricating effect contributed to reducing the gel content. The dynamically crosslinked blends, regardless of the amount of DCP added, showed a reduction in the mechanical properties, which is related to the morphological features of the system due to the low mechanical fragmentation during melt processing. http://dx.doi.org/10.18226/23185279.v3iss1p23The dynamic crosslinking of polyamide 6,12 and ethylene vinyl acetate (PA6,12/EVA) blends in the mixing chamber of a torque rheometer was investigated. EVA was selectively crosslinked within the PA6,12 phase through free radical reactions using dycumil peroxide. The degree of EVA crosslinking in the PA12,6/EVA materials was estimated based on the gel content (insoluble EVA fraction). The PA6,12/EVA phase morphology was investigated by scanning electron microscopy. The mechanical properties were investigated by determining the tensile strength and hardness. The half-life time (t1/2) for homolytic scission of the dcumil peroxide (DCP) was ~6s, and this time is longer than the dispersion time of the DCP in the blends. The addition of DCP resulted in increased torque values due to specific crosslinking in the EVA phase. For the pure EVA and its blends with PA6,12 the stabilized torque values increased proportionally with the amount of DCP in the system, due to a higher degree of crosslinking of the elastomeric phase. The gel content of the dynamically crosslinked blends increased with the amount of DCP incorporated until 4 phr. At 1 phr the gel content value was 2.6wt.%, while at 4 phr it was 17wt.%. For the polymer blend with 8 phr of DCP a lubricating effect contributed to reducing the gel content. The dynamically crosslinked blends, regardless of the amount of DCP added, showed a reduction in the mechanical properties, which is related to the morphological features of the system due to the low mechanical fragmentation during melt processing. http://dx.doi.org/10.18226/23185279.v3iss1p2

Tunable structure and properties of segmented thermoplastic polyurethanes as a function of flexible segment

Segmented thermoplastic polyurethanes (PUs) were synthetized using macrodiols with different functional groups (carbonate, ester, and /or ether) as a segment with a molar mass of 1000 and 2000 g/mol, and 4,4'-diphenylmethane diisocyanate (MDI) and 1,4-butanediol as a rigid segment. The polyurethanes obtained reveal a wide variation of microphase separation degree that is correlated with mechanical properties and retention of tensile properties under degradation by heat, oil, weather, and water. Different techniques such as differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), Fourier transform infrared (FTIR), and synchrotron small-angle X-ray scattering (SAXS) were used to determine rigid-flexible segments' phase behaviour. Retention of tensile properties determines the stability of the samples under different external factors. This work reveals that pure polycarbonate-based macrodiols induce the highest degree of phase miscibility, better tensile properties, hardness shore A, and retention of tensile properties under external agents

Castor oil-based polyurethane/S2 glass/aramid hybrid composites manufactured by vacuum infusion

This study evaluates the hybridization effect of S2-glass/aramid on polyurethane (PU) composites produced by vacuum infusion. Different laminates were produced with similar thickness (around 2.5 mm), using, as reinforcement, only aramid fabrics (five layers, named as K5 ) or only S2-glass fabrics (eight layers, named as G8 ). Furthermore, hybridization was obtained by manufacturing symmetrical hybrid inter-ply laminates, with four S2-glass layers and two of aramid, (G2K)S and (KG2 )S. The mechanical response of the laminates was evaluated in tensile, interlaminar shear strength, dynamical mechanical analysis and quasi-static indentation tests, and related to their morphological characteristics. The main results show that the pure glass composites presented less voids, but a higher density as well as higher tensile stiffness and strength. The aramid laminates showed a high capability for absorbing impact energy (ca. 30% higher than the pure glass laminates), and the hybrid laminates had intermediate properties. More importantly, this work shows the possibility of using a polyurethane matrix for vacuum infusion processing, effective even for aramid/S2-glass hybrid composites with thermoset polyurethane resin. This study is therefore promising for impact absorption in applications such as protective armor. The studied hybrid laminate may display a suitable set of properties and greater energy absorption capability and penetration resistance for impact applications

Inactivation of Pseudomonas aeruginosa in mineral water by DP1 bacteriophage immobilized on ethylene-vinyl acetate copolymer used as seal caps of plastic bottles

Pseudomonas aeruginosa has been found in bottled natural mineral water, even though its presence is not allowed in this product by different food regulations. This study aimed to investigate the inactivation of P. aeruginosa present in mineral water by vB_PaeM_CEB_DP1 (short name DP1) bacteriophage immobilized on ethylenevinyl acetate (EVA) copolymer used as seal caps of plastic bottles. EVA was chemically modified using microwaveassisted alcoholysis, improving polymerphage binding. After that, DP1 phage was attached to EVA and EVAOH copolymers and both surfaces were tested for plaque formation using P. aeruginosa. Then, both materials containing immobilized phages were used as seal caps of plastic bottles and its antimicrobial capacity was tested against P. aeruginosa contaminating mineral water. The EVAOH resulted in higher hydrogen bond density that contributed significantly to the phage immobilization on the polymer surface. The polymers containing immobilized phages were able to reduce 0.53 log of P. aeruginosa population present inside mineral water bottles after 14days.The authors thank CAPES for scholarships to Cesar H. Wanke and Junia Novello. CNPq—National Council for Scientific and Technological Development, Brazil for financial support (grant numbers 308241/2015-0 and 306086/2018-2). Sanna Sillankorva acknowledges funding from the European Union’s Horizon 2020 research and innovation programme (grant number 713640).info:eu-repo/semantics/publishedVersio

Modificação química de nanoestruturas híbridas (POSS) para aplicação como lubrificantes

Polyhedral oligomeric silsesquioxanes (POSS) are hybrid structures type RSiO15n, with n organic groups R. These molecules can be easily functionalized by simply changing the chemical constitution of the organic groups. In this work, chemical modification of POSS-NH2 was performed by amidation reaction with butyric acid at elevated temperature, 160°C. The formation of the amide group is evinced by the appearance of NH angular deformation band at 1540 cm-1 in the FTIR spectra. Approximately 40% of the amino groups reacted, according to titration results. The formation of the amide groups resulted in a shift of the glass transition temperature (Tg) from -36.9°C to -25.6°C for the modified-POSS sample. Both POSS-NH2 and modified-POSS samples exhibited similar thermal degradation pattern. Analysis of the pairs distribution function (PDF) has determined that the hybrid nanoparticles are separated by a periodic distance of approximately 1.32 nm. POSS-NH2 and modified-POSS exhibit newtonian behavior, which will range from 10-1 s-1 and 1000 s-1. The viscosity decreased with increasing temperature, a typical behavior of liquid lubricants. http://dx.doi.org/10.18226/23185279.v2iss1p19Poliedros oligoméricos silsesquioxanos (POSS) são estruturas híbridas tipo RSiO1,5n  com n grupos orgânicos R. Estas moléculas podem ser facilmente funcionalizadas, simplesmente alterando a constituição química dos grupos orgânicos. Nesse trabalho, a modificação química de POSS-NH2 foi feita por meio de reações de amidação com ácido butírico em elevada temperatura, 160°C. A formação do novo grupo amida é evidenciada pelo do surgimento da banda de deformação angular do NH em 1540 cm-1 nos espectros de FTIR. Aproximadamente 40% dos grupos aminos reagiram, conforme resultados de titulação. A formação dos grupos amidas resultou no deslocamento da temperatura de transição vítrea (Tg) de -36,9°C para -25,6°C para o POSS-modificado. Ambas as amostras, de POSS-NH2 e POSS-modificado, exibem padrão de degradação térmica semelhante. A análise da função de distribuição de pares (PDF) determinou que as nanopartículas híbridas são separadas por uma distância periódica de aproximadamente 1,32 nm. O POSS-NH2 e o POSS-modificado apresentam comportamento newtoniano, na faixa que vai de 10-1 s-1 até 1000 s-1. A viscosidade diminuiu com aumento da temperatura, um comportamento típico de lubrificantes líquidos. http://dx.doi.org/10.18226/23185279.v2iss1p19