Pseudostem of the Musa cavendishii banana plant was submitted to chemical pretreatments with acid (HSO 2%, 120 °C, 15 min) and with alkali (NaOH 3%, 120 °C, 15 min), saccharified by commercial enzymes Novozymes® (Cellic CTec2 and HTec2). The influences of the pretreatments on the degradation of the lignin, cellulose and hemicellulose, porosity of the surface, particle crystallinity, and yield in reducing sugars after saccharification (Y ), were established. Different concentrations of biomass (70 and 100 g/L in dry matter (dm)), with different physical differences (dry granulated, crushed wet bagasse, and whole pseudostem), were used. The broth with the highest Y among the different strategies tested was evaporated until the concentration of reducing sugars (RS) was to the order of 100 g/L and fermented, with and without prior detoxification with active carbon. Fermentation was carried out in Erlenmeyer flasks, at 30 °C, initial pH 5.0, and 120 rpm. In comparison to the biomass without chemical pretreatment and to the biomass pretreated with NaOH, the acid pretreatment of 70 g/L of dry granulated biomass enabled greater digestion of hemicellulose, lower index of cellulose crystallinity, and higher Y (45.8 ± 0.7%). The RS increase in fermentation broth to 100 g/L, with posterior detoxification, presented higher productivity ethanol (Q = 1.44 ± 0.02 g/L/h) with ethanol yield (Y ) of 0.41 ± 0.02 g/g. The value of Q was to the order of 75% higher than Q obtained with the same broth without prior detoxification.

Gasketed plate heat exchangers are characterized in a usual heat exchanger class. These systems employ elastomeric gaskets as the sealing element. Several conditions lead to oxidation and deterioration of these materials and their properties. In addition, the complex geometry of the gaskets and operation conditions may cause divergence in the expected aging behavior of the rubber. In light of this, this study aims to predict the service lifetime for nitrile butadiene rubber gaskets used in plate heat exchangers based on their geometry under thermo‐oxidative aging. These gaskets were evaluated by means of Shore A hardness, compression set (CS), and indentation modulus profile. Through aging‐sealing tests, an end‐of‐life criteria was determined concerning CS measurements and the service lifetime prediction was obtained by time–temperature superposition and WLF method. Diffusion‐limited oxidation effects were observed at high temperatures in postaging analysis and a non‐Arrhenius behavior was observed at 170°C. The value of 79% CS was obtained as end‐of‐life criteria from 60 to 140°C, ranged from 731 to 80 days, respectively, revealing an activation energy equivalent to 32.3 kJ mol−1. These results might support the maintenance planning control of gasketed plate heat exchangers.

Acrylonitrile‐butadiene rubber (NBR) and ethylene‐propylene‐diene monomer (EPDM) gaskets are used as seals in plates heat exchangers due to their elasticity and resilience. However, contact with fluids, oxygen, ozone, and heat lead to permanent deformation. This study investigates the degradation of gaskets submitted to similar service conditions: compressed in a groove for up to 360 h at 100 and 120°C. The analysis was carried through compression set (CS), compression stress relaxation, surface morphology, Shore A hardness, indentation modulus profile, crosslink density, and Fourier transform infrared region with attenuated total reflection analysis. For EPDM, in thermo‐oxidative aging there is a counterbalance between chain scission and crosslinking, which increases CS while hardness and crosslink density remain low. For NBR, diffusion‐limited oxidation causes heterogeneous oxidation, creating a crosslinking network near the surface. The values for CS, Shore A hardness, and crosslink density raised to 50%, 10%, and 75%, respectively. Furthermore, the side thermo‐oxidation was reduced due to the presence of the groove, which reduces oxygen access. Using FITR analysis, a thermo‐oxidative interaction mechanism was proposed for the EPDM and NBR gaskets. It was concluded that EPDM presented a more reliable behavior for the gasket and seal applications under the analyzed conditions.

This study investigates the effects of aging on the physical and mechanical properties of commercially available acrylonitrile-butadiene rubber (NBR) gaskets while maintaining their original geometry. Thermo-oxidative cycles with 10 and 70 mm in length specimens were conducted from 80 to 170 C up to 180 days. The samples were analyzed employing compression set (CS), hardness, indentation modulus, cross-link density, total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), and thermogravimetry. The results showed that longer specimens presented better resistance to thermo-oxidative aging. Indentation results indicated regular oxygen permeability into the entire samples up to 110 C, while at higher temperatures, limited diffusion oxidation (DLO) effects promoted non-uniform aging. Time-temperature superposition (TTS) and Arrhenius methods were applied to predict the specimens' lifetime using CS as a failure criterion. Activation energies for 10 and 70 mm samples were 68.74 and 43.63 kJ mol À1 , respectively. Thus, the 70 mm specimen's lifetime was greater than 10 mm. For temperatures below ≈38 C, the response to the thermo-oxidative aging is independent of specimen length. Therefore, in determining the lifetime of gaskets with complex geometry, longer specimens are recommended to provide more reliable results than those suggested by the standards.

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