Thermal Degradation Temperature Research Articles

Nucleating and reinforcing effects of nanobiochar on poly(3-hydroxybutyrate-co-3-hydroxhexanoate) bionanocomposites.

This study promotes the use of nanobiochar (NBC) as an environmentally friendly substitute to conventional fillers to improve various properties of biopolymers such as their mechanical strength, thermal stability and crystallization properties. TGA analysis showed a slight increase in onset thermal degradation temperature of the composites by up to 5 °C with the addition of 4 wt% NBC. Non-isothermal DSC analysis determined that the addition of NBC into PHBHHx increases the crystallization temperature and degree of crystallinity of PHBHHx while isothermal DSC analysis demonstrated higher crystallization rate in PHBHHx/NBC composited by up to 54%. PHBHHx incorporated with NBC also exhibited superior tensile strength and modulus versus neat PHBHHx. Increase in mechanical strength was further proven via DMA where PHBHHx/NBC composites maintained higher storage modulus at higher temperatures when compared to neat PHBHHx. PHBHHx/NBC also exhibited no cytotoxicity effect against HaCat cells. This study demonstrates the ability of biochar to act as both nucleating agents and reinforcing agents in biodegradable polymers such as PHBHHx, which could be suitable for packaging application.

Tacticity Characterization of Biosynthesized Polyhydroxyalkanoates Containing (S)- and (R)-3-Hydroxy-2-Methylpropionate Units.

Polyhydroxyalkanoates (PHAs), aliphatic polyesters synthesized by microorganisms, have gained considerable attention as biodegradable plastics. Recently, α-carbon-methylated PHAs have been shown to exhibit several interesting properties that differ from those of conventional PHAs, such as their crystallization behavior and material properties. This study investigated α-carbon methylated (S)- and (R)-3-hydroxy-2-methylpropionate (3H2MP) as new repeating units. 3H2MP units were homopolymerized or copolymerized with (R)-3-hydroxybutyrate (3HB) by manipulating the culture conditions of recombinant Escherichia coli LSBJ. Consequently, PHAs with 3H2MP units ranging from 5 to 100 mol % were synthesized by external addition of (R)- and (S)-enantiomers or the racemic form of 3H2MPNa. The (S)-3H2MP precursor supplemented into the culture medium was almost directly polymerized into PHA while maintaining its chirality. Therefore, a highly isotactic P(3H2MP) (R:S = 1:99) was synthesized, which displayed a melting temperature of 114-119 °C and a relatively high enthalpy of fusion (68 J/g). In contrast, in cultures supplemented with (R)-3H2MP, the precursor was racemized and polymerized into PHA, resulting in the synthesis of the amorphous polymer atactic P(3H2MP) (R:S = 40:60). However, racemization was not observed at a low concentration of the (R)-3H2MP precursor, thereby synthesizing P(3HB-co-8 mol % 3H2MP) with 100% (R)-3H2MP units. The thermogravimetric analysis revealed that the thermal degradation temperatures at 5% weight loss of P(3H2MP)s occurred at approximately 313 °C, independent of tacticity, which is substantially higher than that of P(3HB) (257 °C). This study demonstrates a new concept for controlling the physical properties of biosynthesized PHA by manipulating the polymers' tacticity using 3H2MP units.

Study on the improvement of complexation efficiency and anti-digestibility of phenolic acids based on electrospun starch fibers

Phenolic acids can be encapsulated by starch electrospun fibers, and the structural and functional properties of the electrospun fiber are affected by the chemical structure of phenolic acid. In this study, five phenolic acids (protocatechuic acid (PA), p-hydroxybenzoic acid (PHBA), p-coumaric acid (PCA), ferulic acid (FA), and caffeic acid (CA)) were chosen to prepare electrospun fibers with high amylose corn starch (HACS) at different voltages. Morphology and complexation efficiency results revealed that the electrospun fibers prepared at 21.0 kV were smooth and continuous with high encapsulation efficiency (EE) and loading efficiency (LE). The chemical structure of phenolic acid played an important role in the structure and properties of electrospun fibers by influencing the complexation of HACS with phenolic acids and the inhibitory effect of amylase. As a result, electrospun fibers containing HACS-CA inclusion complex had higher relative crystallinity (25.47 %), higher thermal degradation temperatures (356.17 °C), and the strongest resistance to digestion (starch digestive ratio = 22.98 %). It is evident that electrospun fibers containing HACS-phenolic acid inclusion complexes not only achieve high phenolic acid complexation efficiency, but also resist the effects of the gastric and small intestinal environment on phenolic acids, thereby improving the bioaccessibility of phenolic acids.

Aramid nanofiber‐reinforced poly(lactic acid) nanocomposites with enhanced thermal stability, melt‐crystallization rates, and mechanical toughness

AbstractThe main goal of this study is to investigate the impact of aramid nanofiber (ANF) on enhancing various properties of poly(lactic acid) (PLA), including thermal stability, crystallization rates, melt‐rheological behavior, and mechanical properties. To achieve this, ANF fillers were produced using a modified deprotonation process from commercial aramid fibers, and a masterbatch (PLA/ANF = 90/10 by wt%) was prepared through solution blending and drying. The masterbatch was then combined with neat PLA through melt‐blending to create a range of PLA nanocomposites containing 1–10 wt% ANF loadings. Microscopic and spectroscopic analyses confirmed the uniform dispersion and intermolecular interaction of ANFs within the PLA matrix, respectively. As a result, the nanocomposites exhibited a slight increase in glass transition temperature with higher ANF loading, while the cold‐crystallization temperature decreased due to ANFs acting as nucleating agents during PLA crystallization. Isothermal crystallization analysis confirmed accelerated melt‐crystallization rates in nanocomposites with greater ANF content. The introduction of ANFs enhanced the thermal degradation temperature of the PLA matrix and the 700°C residue of the nanocomposites, attributed to ANFs' barrier and flame retardant effects on PLA. Moreover, the nanocomposites with higher ANF loading demonstrated superior tensile strength, strain at break, toughness, and impact strength owing to the effective bonding interactions at the interfaces between the PLA matrix and the ANF fillers.Highlights ANF‐reinforced PLA nanocomposites are prepared by masterbatch melt‐compounding. Uniform dispersion of ANFs in PLA is attained via effective interfacial bonding. ANFs boost the melt‐crystallization of the PLA matrix. ANFs enhance the thermal stability of the PLA matrix. Tensile strength and toughness of PLA are improved with higher ANF content.

Dual−crosslinked polyionic liquid polymer electrolyte with optimal balance of ion conductivity and mechanical properties for solid−state lithium metal battery

Polyionic liquids (PILs) are considered promising candidates for next−generation solid polymer electrolytes (SPEs) because they combine the electrochemical stability of ionic liquids with the processability/flexibility of polymers. However, the practical application of PILs−based SPEs are limited by their unsatisfactory mechanical properties in parallel with their insufficient ionic conductivity. Here, a double crosslinked PIL-based SPE with an optimal balance of ionic conductivity and mechanical properties is constructed by ultraviolet (UV) initiated polymerization. Among, the ionic liquid 1−(4−vinylbenzyl)−3−butylimidazolium bis(trifluoromethanesulfonyl)imide ([VBBIM][TFSI]) as a monomer, poly(ethylene glycol) diacrylate (PEGDA) and polyhedral oligomeric sesquisiloxane (POSS) as a functional crosslinker. As expected, the synthesized PIL−based SPE (POSS-PIL-PEGDA−1, 1 wt% POSS) shows a high ionic conductivity of 1.8 × 10−4 S cm−1 (at 30 °C), a satisfactory tensile strength of 0.64 MPa, an ultrahigh thermal degradation temperature around 320 °C and a wide electrochemical stability window about 5.0 V versus Li/Li+. As a concept proof, the POSS-PIL-PEGDA−1 SPE can effectively inhibit lithium dendrites growth, and the assembled Li||LiFePO4 solid−state lithium metal battery achieves a high discharge capacity and a good cycling performance. This strategy is attractive for studying the trade−off between mechanical properties and ionic conductivity of crosslinked PIL−based SPEs.

Effect of high-pressure treatment on the rheological properties of Alyssum homolocarpum seed gum/grass pea protein isolate dispersions and comparison with heat-induced gels

The effects of high-pressure (HP) treatment at 400 MPa for 15 min on rheological properties of dispersions and gels of grass pea protein isolate (10% GPPI) containing different concentrations of Alyssum homolocarpum seed gum (0.2, 0.4 and 0.6% AHSG) were investigated. With the addition of AHSG, the amount of α-helix, β-sheet, and random coils in pre-treated GPPI decreased, whereas after HP treatment, α-helix and β-turn content increased. For AHSG-GPPI mixtures, it was found that HP treatment increased the intensity of X-ray diffraction peaks at 2θ = 11 and 26°, which had previously been found to decrease and become flatter with increasing gum concentration. The thermal degradation temperature (Td) and enthalpy (ΔH) increased after the addition of AHSG and following HP treatment. All mixed solutions had shear thinning behavior before and after HP treatment. When AHSG was added to GPPI, η0 and η∞ increased for both HP-treated and untreated samples, while after the treatment, the magnitude of η0 and η∞ slightly decreased. G′ values were higher than G″ values for all AHSG-GPPI dispersions, indicating a gel-like behavior for these mixtures. With increasing gum concentrations, G′ and G″ values of dispersions increased; however, these moduli decreased after exposure to HP treatment, though they were not statistically significant. The addition of AHSG significantly decreased the gelation temperature, increased the G′ value, and made the system more elastic during conventional heating and cooling ramps. When the HP treated samples were heated, the G′ value increasing trend was almost identical to that of the untreated samples, but during the cooling stage, the value of G′ for the HP treated samples were significantly higher.

Enhancing flame retardant and wrinkle-resistant performances of silk fabric with bio-based Maillard reaction products between glucose and poly(glutamic acid)

Bio-based materials have garnered considerable attention in the flame retardant field due to their inherent safety and environmental benefits. This study introduces a novel and eco-friendly flame retardant prepared through the Maillard reaction between glucose and poly(glutamic acid) for treating silk fabric. The study elucidates the synthesis of Maillard reaction products (MRPs) and verifies their deposition onto the silk fabric surface by observing changes in surface morphology, functional groups, and charged characteristics. The flammability tests demonstrate that MRPs treated silk fabrics had a high limiting oxygen index of over 27 % and a charred length of less than 12 cm, indicating effective flame retardancy. Moreover, the introduction of MRPs led to a significant decrease in smoke release when silk fabric underwent combustion. This observation can be attributed to the enhanced char formation and increased thermal degradation temperature of MRPs treated silk fabric. The electrostatic interaction between silk fiber and MRPs contributed to the fabric's resistance to repeated washing. Moreover, MRPs treated silk fabric retained their tensile properties and showed enhanced wrinkle-resistant performance. Generally, this research opens up a new path for the green preparation of halogen-free and phosphorus-free flame retardant protein fibers.

Preparation of ionic liquid@SiO2 nanocapsules for improving self-lubricating performance of PA6 composites

A novel high temperature resistance ionic liquid@SiO2 (IL@SiO2) nanocapsules were successfully prepared in order to meet the high temperature processing requirement. The average diameter and the loading capacity of as-obtained IL@SiO2 nanocapsules were about 420 nm and 44.7 wt% respectively. The IL@SiO2 nanocapsules showed excellent thermal stability with a 340 °C initial thermal degradation temperature. The frictional and wear properties of PA6 composites containing IL@SiO2 nanocapsules under different friction temperature were studied systemically. Self-lubricating PA6 composites with 3 wt% IL@SiO2 nanocapsules showed the optical tribological propertied. The corresponding friction coefficient of PA6 composites reduced by 38.9%, and the wear rate also showed a 60.7% decrease compared with pure PA6. Unlike most microcapsules, the addition of nanocapsuels did not cause an undesirable and obvious decrease in mechanical properties of PA6. Anti-wear and friction-reduction mechanism were depth analyzed, and results revealed that IL core and SiO2 wall in nanocapsules synergistically contribute to improve self-lubricating performance of PA6 composites.

Thermal, mechanical, thermo‐mechanical and morphological properties of graphene nanoplatelets reinforced green epoxy nanocomposites

AbstractThe efficient inclusion of GNPs (graphene nanoplatelets) as an effective nano‐fillers for green polymer matrices produced with 28% of carbon originating from biomass tends to significantly improve mechanical and thermal properties. In the present work, green epoxy nanocomposites with low loading of (0.1, 0.25, and 0.5) wt% of the GNPs were made using a solution blending technique using acetone as the solvent. In mechanical stirring, the ultrasonic bath was used to ensure the efficient dispersion of GNPs within green epoxy. The resulting nanocomposites were comprehensively characterized and compared to unfilled green epoxy. Different tools were used to appraise morphological, thermal, thermo‐mechanical, and mechanical behavior. The results confirmed through FE‐SEM showed an optimal dispersion of GNPs with nanocomposites. The thermal degradation temperature (Td) of GNPs curve with 0.25 wt% loading was shifted toward higher temperature (from 336°C to 342°C) due to low percentage of loading of GNPs which showed an enhance thermal stability of polymer matrix with 0.25 wt% loading. The mechanical results were also in lined with previously published literature, in the tensile test 6.45% and hardness 13.3% increment was achieved. Overall, the results underscored significant improvements in green nanocomposite performance with low wt% of GNPs.Highlights The study focuses on development and characterization of green epoxy nanocomposites, which utilize environmentally friendly materials as a matrix, highlighting the significance of sustainability. The study explores effects of low loading of GNPs in green epoxy nanocomposites. The results demonstrate significant improvements in mechanical and thermal properties with optimized presence of GNPs. This investigation provides insights into optimal amount of GNPs required to achieve improved properties. Research evaluates multifaceted analysis provides a holistic understanding of performance enhancements achieved through inclusion of GNPs.

Preparation and characterization of hemicellulose films reinforced with amino polyhedral oligomeric silsesquioxane for biodegradable packaging

Biomass is one of the powerful alternatives to petroleum-based packaging materials. Herein, carboxymethyl hemicellulose (CMH) based films (CPF) were prepared using a convenient strategy. The chains of CMH provided the necessary supporting matrix, and the aminopropyl polyhedral oligomeric silsesquioxane (POSS-NH2) regulated the thermal and barrier properties of the CPF. The secondary amide groups and hydrogen bond were appeared in chemical structure, and SEM-EDS results indicated the preferable dispersion and compatibility of POSS-NH2 in CPFs. The thermal degradation temperature (Tonset > 260 °C), the coefficient of linear thermal expansion and glass transition temperature (Tg > 130 °C) have been improved by introduction of POSS-NH2. The tensile strength of CPF showed a higher level of 39.43 MPa with the POSS-NH2 loading of 20 wt%, which was 18.8 % higher than that of CMH film. More importantly, water vapor barrier property of films almost improved by two times, and its value is reduced to 18.82 g m−2 h−1. The shelf life of blueberry was effectively extended by the CPF coating for one week compared with commercial PE film. Therefore, CPF films displayed effective thermal performances, water vapor barrier characteristic and biodegradability, which might be exploited in packaging material for food application.

Study on the thermal decay mechanism of basalt fiber reinforced resin based friction materials

PurposeResin-based friction materials are the most widely used key materials in industry for braking and transmission. However, the friction coefficient of resin-based friction materials significantly decreases at temperatures above 300°C, which reduces their friction performance.Design/methodology/approachThis study combines elevated-temperature mechanical experiments with friction and wear experiments to explain the thermal degradation resistance performance and temperature recovery performance of resin-based friction materials. It also investigates the influence of friction material strength and worn morphology on the friction coefficient of materials at elevated temperature.FindingsThe experimental results show that the increase in friction coefficient of friction materials below 300°C is mainly due to the increase in worn morphology characterization parameters, and the thermal degradation phenomenon above 300°C is mainly due to the decrease of shear strength of friction film. Basalt fiber can significantly improve the thermal degradation resistance of friction materials. The friction coefficient of basalt fiber-reinforced specimens after thermal degradation reaches 0.421–0.443, which is 19–25% higher than the original. The thermal decay rate is 9.03–11.0%, which is 7.9–9.87% lower than the original. Moreover, the friction coefficient has good cooling recovery performance.Originality/valueRevealed the thermal degradation mechanism of resin-based friction materials, verified that basalt fibers can improve the thermal degradation resistance of friction materials and provided reference for the development of new friction materials.

Extraction and Characterization of Natural Fiber from the Stem of Dombeya Buettneri Plant for Biodegradable Polymeric Composites Application

ABSTRACT The global drive for a circular economy emphasizing sustainability in composite manufacturing processes has been the driving force for current ongoing research studies in natural fibers as sustainable substitutes for non-biodegradable synthetic fibers. The present study was carried out to characterize Dombeya buettneri fiber (DBF) extracted manually from the bark of the plant stem. Determination of physical and mechanical properties, quantitative chemical analysis, Fourier Transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis and scanning electron microscopy were used to characterize the extracted fiber. Fiber constituents and XRD results showed higher cellulose content (58.45%), crystallinity index (62.32%) and percent crystalline (72.63%). The fiber had a crystallite size of 2.16 nm as determined using the Debye-Scherrer’s equation while FTIR analysis confirmed the presence of various functional groups of lignin, hemicellulose and cellulose on the fiber structure. The results revealed that DBF fiber had a thermal resistance that is up to 229.57°C with a maximum thermal degradation temperature of 356.27°C. Based on the results of this research that are comparable with other studies on cellulosic fiber, DBF fiber has a great potential as an alternative reinforcement for the development of polymer-based bio-composites.

Characterization of tannin extracted from Aningeria altissima bark and formulation of bioresins for the manufacture of Triumfetta cordifolia needle-punched nonwovens fiberboards: Novel green composite panels for sustainability

The new Aningeria altissima tannins extracted from ground bark were characterized by ATR-FT MIR and MALDI-ToF spectrometry. The tannin extracts were found to contain flavonoids and glucose, with a strong predominance of chalcone and gallocatechingallate monomers typical of condensed tannin proanthocyanidins. Two different formulations of resins bio-cured with hexamine and exudates from the Vachellia nilotica tree were analyzed (gel time, TMA and ATG) and used to manufacture biocomposite panels of carded-needled non-woven fibers of Triumfetta cordifolia (TC) natural fibers. The new biocomposites bonded with extracted Aningeria altissima tannin showed high water sensitivity, exceeding EN 622–5. The incorporation of TC fibers increased the thermal degradation temperature of biocomposites and improved their thermal stability. The mechanical properties of both biocomposites are high in the weft direction, which is favored by the preferential orientation of the fibers in this direction. In particular, the high flexural strength and flexural modulus are good enough to meet the specifications of current international standards for fiberboards used in dry conditions. The biocomposite with the optimum properties was obtained from fibers bonded with hexamine-cured tannin resin.

The potential of starch-chitosan blends with poloxamer for the preparation of microparticles by spray-drying

Using biopolymers as wall materials in spray drying poses challenges, particularly in attaining flowability and thermal stability among their physicochemical properties. This paper addresses these challenges by preparing microparticles using a blend of starch–chitosan and a poloxamer, commercially named Pluronic® F127. We aimed to elucidate the effects of varying poloxamer concentrations on the resulting particles through the spray drying technique. Blends with a poloxamer concentration of 3% (w/v) demonstrated a notably higher yield, especially when compared to those with 0% and 1% concentrations. Microparticles with 3% and 5% (w/v) poloxamer displayed a narrower particle size distribution, with the 3% blend showing a superior yield attributed to arrangements of blend components that improve flowability. X-ray diffraction analysis showcased the characteristic peaks of A-type starch form, with shifts suggesting enhanced interactions between components. Microparticles with increased poloxamer content showed elevated thermal degradation temperatures, with the 3% blend registering a significant rise, opening avenues for encapsulating heat-sensitive bioactive. This study primarily focuses on the preparation and basic characterization of microparticles. It underscores the potential of blends with optimal poloxamer concentrations in microencapsulation, emphasizing further research to harness their capabilities thoroughly.

Starch extraction from avocado by-product and its use for encapsulation of ginger essential oil by electrospinning

Starches from alternative sources, such as avocado seed, have potential for application in the encapsulation of essential oils. This study aimed to extract starch from avocado seeds and its use as wall material to encapsulate ginger essential oil (GEO), at different concentrations. The fibers were produced by electrospinning and evaluated by morphology, size, infrared spectra, thermogravimetric properties, contact angle, loading capacity, and antibacterial activity. The major compounds in GEO were α-zingiberene, β-sesquiphellandrene, α-farnesene, and α-curcumene. The starch-GEO fibers presented a higher diameter (∼553 nm) than those without GEO (345 nm). Encapsulation of GEO in starch fibers increased their thermal degradation temperatures from 165.8 °C (free GEO) to 257.6 °C (40 % GEO fibers). The starch-GEO fibers presented characteristic bands of their constituents by infrared spectra. Loading capacity ranged from 44 to 54 %. The fibers showed hydrophilic character, with a contact angle of <90°. Free GEO and the fibers with 50 % of GEO displayed antibacterial activity against Escherichia coli, proving the bioactivity of the starch-GEO fibers and its possible applicability for food packaging. Avocado seed starch showed to be a great wall material for GEO encapsulation.

Reprocessable and recyclable high-performance carbon fiber-reinforced composites enabled by catalyst-free covalent adaptable networks

Carbon fiber-reinforced composites (CFRCs) have been extensively applied in high-tech industry due to their superior mechanical properties. However, the permanent crosslinked networks of thermosetting matrices cause them difficult to reshape, repair and recycle. In this work, we devise a series catalyst-free covalent adaptable networks (CANs) by curing diglycidyl 4,5-epoxycyclohexane-1,2-dicarboxylate (DGEDC) with phthalic anhydride (PA) and glycerol. Benefiting from the rigidity of PA, the resulting DGEDC/PA/Glycerol (DPG) networks possess high mechanical and thermal properties, with glass transition temperature (Tg) of 140–165 °C, thermal degradation temperature (Td5%) of 289–322 °C, fracture strength of 65–78 MPa, and Young’s modulus of 3.2–3.9 GPa. More importantly, the multiple hydroxyl sites endow DPG networks with rapid transesterification reactions (the shortest relaxation time is only 205 s at 180 °C), which allows for material reprocessing, repairing, and degradation. In addition, taking DPG networks as matrix and carbon fibers (CFs) as reinforcement, the obtained DPG/CFs composite exhibits strong mechanical properties (tensile strength and modulus of 559 MPa and 8.5 GPa, bend strength and modulus of 420 MPa and 6.2 GPa) and good welding ability (shear strength of 19 MPa). Furthermore, the composite can be completely degraded in ethylene glycol at 190 °C, achieving efficient and non-destructive recycling of CFs. This research presents an alternative approach for the fabrication of reprocessable and recyclable high-performance CFRCs, which might have broad practical applications in aeronautic engineering and automobile equipment.

Additive Free Crosslinking of Poly-3-hydroxybutyrate via Electron Beam Irradiation at Elevated Temperatures.

When applying electron or gamma irradiation to poly-3-hydroxybutyrate (P3HB), main chain scissions are the dominant material reactions. Though propositions have been made that crosslinking in the amorphous phase of P3HB occurs under irradiation, a conclusive method to achieve controlled additive free irradiation crosslinking has not been shown and no mechanism has been derived to the best of our knowledge. By applying irradiation in a molten state at 195 °C and doses above 200 kGy, we were able to initiate crosslink reactions and achieved gel formation of up to 16%. The gel dose Dgel was determined to be 200 kGy and a range of the G values, the number of scissions and crosslinks for 100 eV energy deposition, is given. Rheology measurements, as well as size exclusion chromatography (SEC), showed indications for branching at doses from 100 to 250 kGy. Thermal analysis showed the development of a bimodal peak with a decrease in the peak melt temperature and an increase in peak width. In combination with an increase in the thermal degradation temperature for a dose of 200 kGy compared to 100 kGy, thermal analysis also showed phenomena attributed to branching and crosslinking.

Synthesis and Investigation of Thermal and Dynamic Mechanical Properties of Urethane-Containing Epoxy Resins

This study aims to improve the thermal and mechanical properties of epoxy-based materials. For this purpose, the structure of epoxy resins was changed by chemical modification and epoxy resin containing urethane was synthesized. The synthesized resin was blended with commercial epoxy resin at the ratios of 25%, 50%, 75% by weight and hardened by curing. The thermal and mechanical properties of urethane-containing epoxy materials prepared in different proportions were compared with those produced from commercial epoxy resin. The structural characterization of the prepared materials was investigated by Fourier Transform Infrared Spectroscopy (FTIR) analysis, their thermal behavior was investigated by Thermogravimetric Analysis (TGA), and their mechanical properties were investigated by Dynamic Mechanical Analysis (DMA). TGA and DMA analyses of the materials showed that the presence of urethane in the structure of epoxy resins significantly changed the mechanical and thermal properties. It was observed that the storage and loss modulus values of urethane-containing resins increased approximately 2.5 times compared to commercial epoxy resins, and a decrease of approximately 10% in thermal degradation temperatures was observed.

CELLULOSE NANOFIBER FROM YERBA MATE STICKS: SURVEY OF MORPHOLOGICAL, CHEMICAL AND THERMAL PROPERTIES

This study aims to evaluate different process conditions for obtaining cellulose nanofibers (CNFs) from yerba mate residues. This includes chemical (bleaching and/or TEMPO-oxidation), physical (steam explosion), and mechanical treatments (ultrafine grinding). All treatments demonstrated to be efficient in obtaining CNFs, as observed from a morphological analysis by transmission electronic microscopy (TEM). A reduction of hemicelluloses and an increase in cellulose content was observed from the Fourier-transform infrared spectroscopy (FTIR) results, after all the treatments. The yerba mate sample that underwent physical/chemical/mechanical treatments showed a higher thermal degradation temperature peak at 333 °C, with a degradation of 50% of the initial mass. The activation energy (Ea) increased from 33% to 64%, when the CNFs were obtained using the derivative Friedman method for all the samples, and this method presented a greater proximity to the experimental results. These results demonstrate that CNFs can be obtained from yerba mate residues, to valorize this lignocellulosic biomass.

Fabrication of organic based thermal resistance material using pyrolyzed cellulose nanofiber and carbon fiber for high performance thermal insulation

Herein, polymer-based thermal insulating composites are fabricated using pyrolyzed cellulose nanofiber (p-CNF) and carbon fiber (CF) in order to overcome the existing limitations of organic-based thermal resistance materials. The p-CNF is prepared by iodine treatment and calcination. The pyrolyzed CNF/CF composites are then fabricated via the freeze casting of two-dimensional (2D) CFs to obtain a low thermal conductivity of 0.058 W/mK, along with a high thermal stability, high tensile stress. Therefore, the p-CNF/CF composite provides an efficient thermal insulation performance via low thermal conductivity along with a high thermal degradation temperature, thereby demonstrating the potential for the development of thermal resistance materials.