Temperature Of Maximum Degradation Rate Research Articles

Fabrication of ultrafine Himalayan walnut oil Pickering emulsions by ultrasonic emulsification: Techno-functional properties of emulsions and microcapsules

In present scenario, much of the attention has been put on the production and utilization of Pickering emulsions deciphering enhanced stability and applicability over wide environmental conditions. In this context the present study was carried out to elaborate effect of different wall materials and pH systems on the physicochemical, structural and morphological properties of Himalayan walnut oil Pickering emulsions by ultrasonic emulsification. In this study, concentrated Pickering emulsion of Himalayan walnut oil (HWO) was prepared utilizing soy protein isolate (SPI), maltodextrin (MD) stabilized by pectin at varying concentrations and pH systems (4.0, 7.0). With increase in pectin and SPI concentration and lowering MD, stable emulsions were obtained as deciphered by an Emulsion stability index (ESI) of 100 for 7 days at ambient storage. HWO Pickering emulsions were analysed for particle size measurements (2.13–13.64 µm) and depicted negative zeta potential values (−3.70 to −18.58). Lyophilized HWO microcapsules depicted moderate encapsulation efficiency (44.69–57.63 %) whereas the hygroscopicity values of the microcapsule ranged from (0.21–12.10 %). Thermogravimetric analysis (TGA) of the samples depicted the temperature of maximum degradation rate up to 550 °C whereas XRD spectra depicted amorphous nature of oil microcapsules. FTIR spectra revealed a close association between the SPI-MD-Pectin matrix. SEM analysis revealed stable oil globules entrapped in protein-polysaccharide matrix with no visible cracks and fissures.

Biodegradable packing food films based on PBAT containing ZnO and MoO3

AbstractMolybdenum trioxide (MoO3) and zinc oxide (ZnO) were incorporated into the poly(butylene adipate‐co‐terephthalate) (PBAT) matrix using casting method to obtain packing films for food transportation with outstanding properties and no formation of microplastics. Consequently, these films were evaluated using Fourier transform infrared spectroscopy, time domain and carbon‐13 nuclear magnetic resonance, x‐ray diffraction, contact angle measurement, and thermogravimetric analysis. The light barrier properties of the films were analyzed using transmittance mode in UV–VIS–NIR regions and the contact angle of composite films exhibited greater hydrophilicity compared to the pure polymer films. Regardless of the concentration, the fillers did not significantly modify the degradation onset temperature and the temperature of maximum degradation rate. However, ZnO caused a new thermal degradation event (around 330°C) that was not observed in the other films, possibly due to the second crystallization process. Composite films filled with 0.3% ZnO, 0.3% and 0.5% MoO3 showed greater molecular homogeneity than the pure polymer matrix, with the PBAT/MoO3 films demonstrating even greater homogeneity than PBAT/ZnO films; this response presumably comes from the satisfactory intermolecular interaction or adequate dispersion and distribution of the particles. The addition of 0.5% MoO3 in the matrix influenced the PBAT film, resulting in amorphous materials with the highest molecular mobility and opacity. Besides, in view of antimicrobial tests, all nanocomposites showed potential bacteriostatic activity. So, it can be conveniently used for food transportation and may avoid microplastic formation, after been discarded.

Biobased Terpene Derivatives: Stiff and Biocompatible Compounds to Tune Biodegradability and Properties of Poly(butylene succinate).

Different copolymers incorporating terpene oxide units (e.g., limonene oxide) have been evaluated considering thermal properties, degradability, and biocompatibility. Thus, polycarbonates and polyesters derived from aromatic, monocyclic and bicyclic anhydrides have been considered. Furthermore, ring substitution with myrcene terpene has been evaluated. All polymers were amorphous when evaluated directly from synthesis. However, spherulites could be observed after the slow evaporation of diluted chloroform solutions of polylimonene carbonate, with all isopropene units possessing an R configuration. This feature was surprising considering the reported information that suggested only the racemic polymer was able to crystallize. All polymers were thermally stable and showed a dependence of the maximum degradation rate temperature (from 242 °C to 342 °C) with the type of terpene oxide. The graduation of glass transition temperatures (from 44 °C to 172 °C) was also observed, being higher than those corresponding to the unsubstituted polymers. The chain stiffness of the studied polymers hindered both hydrolytic and enzymatic degradation while a higher rate was detected when an oxidative medium was assayed (e.g., weight losses around 12% after 21 days of exposure). All samples were biocompatible according to the adhesion and proliferation tests performed with fibroblast cells. Hydrophobic and mechanically consistent films (i.e., contact angles between 90° and 110°) were obtained after the evaporation of chloroform from the solutions, having different ratios of the studied biobased polyterpenes and poly(butylene succinate) (PBS). The blend films were comparable in tensile modulus and tensile strength with the pure PBS (e.g., values of 330 MPa and 7 MPa were determined for samples incorporating 30 wt.% of poly(PA-LO), the copolyester derived from limonene oxide and phthalic anhydride. Blends were degradable, biocompatible and appropriate to produce oriented-pore and random-pore scaffolds via a thermally-induced phase separation (TIPS) method and using 1,4-dioxane as solvent. The best results were attained with the blend composed of 70 wt.% PBS and 30 wt.% poly(PA-LO). In summary, the studied biobased terpene derivatives showed promising properties to be used in a blended form for biomedical applications such as scaffolds for tissue engineering.

Bio-based and one-day compostable poly(diethylene 2,5-furanoate) for sustainable flexible food packaging: Effect of ether-oxygen atom insertion on the final properties

In the present work, the effect of ether oxygen atom introduction in a furan ring-containing polymer has been evaluated. Solvent-free polycondensation process permitted the preparation of high molecular weight poly(diethylene 2,5-furandicarboxylate) (PDEF), by reacting the dimethyl ester of 2,5-furandicarboxylic acid with diethylene glycol. After molecular and thermal characterization, PDEF mechanical response and gas barrier properties to O2 and CO2, measured at different temperatures and humidity, were studied and compared with those of poly(butylene 2,5-furandicarboxylate) (PBF) and poly(pentamethylene 2,5-furanoate) (PPeF) previously determined. Both PDEF and PPeF films were amorphous, differently from PBF one. Glass transition temperature of PDEF (24 °C) is between those of PBF (39 °C) and PPeF (13 °C). As concerns mechanical response, PDEF is more flexible (elastic modulus [E] = 673 MPa) than PBF (E = 1290 MPa) but stiffer than PPeF (E = 9 MPa). Moreover, PDEF is the most thermally stable (temperature of maximum degradation rate being 418 for PDEF, 407 for PBF and 414 °C for PPeF) and hydrophilic (water contact angle being 74° for PDEF, 90° for PBF and 93° for PPeF), with gas barrier performances very similar to those of PPeF (O2 and CO2 transmission rate being 0.0022 and 0.0018 for PDEF and, 0.0016 and 0.0014 cm3 cm/m2 d atm for PPeF). Lab scale composting experiments indicated that PDEF and PPeF were compostable, the former degrading faster, in just one day.The results obtained are explained on the basis of the high electronegativity of ether oxygen atom with respect to the carbon one, and the consequent increase of dipoles along the macromolecule.

Deposition of gum rosin microspheres on polypropylene microfibres used in face masks to enhance their hydrophobic behaviour

The present study aims to investigate the effects of gum rosin (GR) microspheres coating over the hydrophobicity of the outer layer of a polypropylene (PP) based surgical face mask. The gum rosin coating was deposited over the surface of the face mask outer layer by electrospraying technique. The deposition of GR microspheres was confirmed by field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectroscopy (FTIR) analysis. The thermal analysis determined a cooperative effect between the microspheres and the mask fibre to increase the maximum degradation rate temperature and the onset degradation temperature. To follow the effect of the GR microspheres coating over the hydrophobicity of the surgical face mask, FESEM and wettability analyses were conducted before and after 3, 6, and 9 h of wearing time. In the FESEM image, it was seen that the microsphere was homogeneously distributed over the nonwoven fibre and its presence increases the roughness of the fibres due to the bulge of microspheres. The wettability measurements suggest that the microspheres coating helps to keep the original hydrophobicity of the outer layer of the surgical face mask even after 6 h of wearing time. Indeed, after 9 h of wearing time, the water contact angle (WCA) of the GR coated face mask is higher than the WCA of the surgical face mask without the coating at 3 h of wearing time. Therefore, the gun rosin microspheres coating improved the hydrophobicity of the surgical face mask which may allow improved protection and/or extended lifetime of use.

Investigations of the improved performances of silicone rubber in the presence of black titanium

AbstractSilicone rubber (SR)/black titanium (BT) composites with high‐temperature resistance and thermal conduction were prepared via an efficient and convenient blending method. The thermal stability and conductivity of these materials, as well as their properties were systematically investigated to determine the effects of BT. As tensile testing showed, the elongation retention rate of SR‐10 described good antioxidation behavior with a value of 30% after aging at 250 °C for 360 h. Additionally, thermal stability was improved with the introduction of BT. The initial decomposition temperature and maximum degradation rate temperature increased by 200 and 23 °C, respectively, in air atmosphere. As is known, it is difficult for inorganic particles to be well dispersed in a polymeric matrix. However, as observed using scanning electron microscopy, BT displayed a good compatibility and dispersion in the SR matrix without any obvious agglomeration. Moreover, it was found that the addition of BT can further enhance the thermal conductivity of SR to 0.48 W m−1 K−1. © 2021 Society of Industrial Chemistry.

Performance of ethylene vinyl acetate waste (EVA-w) when incorporated into expanded EVA foam for footwear

Ethylene vinyl acetate copolymer blends (EVA-B), with vinyl acetate set at 19 % and 28 % by weight (wt%), were mixed with EVA waste (EVA-w), (a reticulated and micronized ethylene vinyl acetate copolymer) from injection branches and defective midsoles. The EVA-B/EVA-w composites were prepared with 15, 25, and 35 per hundred rubber (phr) EVA-w using a Banbury mixer to mix all components. Afterwards, the mixture was submitted to compression molding to obtain expanded EVA-B/EVA-w composite plates. A standard compound, provided by a Brazilian footwear industry (EVA-ref), was used as reference for thermal and mechanical property comparisons. During the thermal analysis, when increasing the EVA-w content, a delay in the deacetylation of the EVA-B composites in relation to the EVA-ref was observed. There was also an increase in the maximum degradation rate temperature and a reduction in loss of mass in the first decomposition event. In the second event, the maximum temperature did not vary in the composites with EVA-w added as compared to the EVA-ref. The residue content increased at 600 °C, indicating that EVA-w acts as a filler for EVA-B. The mechanical properties evaluated were hardness, tension at break, elongation at break, tear strength, compression set, and shrinkage. Addition of EVA-w to the composites (comparing 15 phr–35 phr) increased tear strength properties by 4 %, (EVA-w acts as a nucleation cell agent, increasing the EVA foam cell density). However, shrinkage increased by roughly 35 % above the specifications for footwear applications. Hardness increased by 5 %, tensile strength increased by 10 %, and elongation at break decreased by roughly 4 %. The compression set property increased by nearly 5 % with the EVA-w content (due to decreasing matrix elongation). Thus, EVA-w acts as a reinforcement filler for EVA-B. A statistical study based on composite performance indices for the mechanical properties, and a cost analysis was performed. Except for the average linear shrinkage (35 phr EVA-w composite), all other studied composites met the mechanical property specifications for sports shoe midsoles. The best combination for process performance and cost analysis was for the EVA-w composite at 25 phr.

Synthesis and Characterization of Biodegradable Polyester/Polyether WPU as the Environmental Protection Coating

Polyester diol PCL and PBA, polyether diol PTMG and polycarbonate diol PCDL were used as components of WPU soft segment, respectively. Polyether PTMG-WPU has the worst hydrolytic property and the highest thermal stability. The maximum degradation rate temperature Tmax is 407.8 °C, the water contact angle reaches 89.5 °. Traditional polyester PCL-WPU shows the strongest hydrolysis performance, the smallest water contact angle, only 71.7 °, the water absorption rate of 72 h at room temperature is as high as 26.7%. However, the thermal stability of PCL-WPU is lower, the soft segment Tg is −52.3 °C, and Tmax is only 333.7 °C, but the mechanical property of which is the best, the tensile strength is 58.3 MPa, and the elongation at break reaches 857.9%. The most important thing is that the structure of polyester PCL-WPU is more easily destroyed by lipase and water molecules. The acidic products produced after hydrolysis will further promote the degradation of polyester. Therefore, compared with other WPUs, PCL-WPU has the best biodegradability and the most obvious degradation effect under the same conditions. The degradation rate of PTMG-WPU after 30 days of degradation in 0.6% lipase PBS buffer solution and soil was only 4.2% and 2.3%, while the highest degradation rate of traditional polyester PCL-WPU reached 41.7% and 32.0%, respectively. In addition, polycarbonate PCDL-WPU has the highest hardness, reaching 95.5 HD. But its other performances are lower than PCL-WPU.

Impact of the film-forming dispersion pH on the properties of yeast biomass films.

Yeast biomass, mainly composed of proteins and polysaccharides (mannans and β-glucans), has been proposed to develop films. pH can affect the solubility of polysaccharides, the structure of the cell wall, and the interactions between proteins. Considering the potential impact of these effects, the pH of yeast film-forming dispersions was studied from 4 to 11. In tensile tests, samples increased their elongation by increasing pH, from 7 ± 2% (pH4) to 29 ± 5% (pH 11), but Young's modulus was not significantly modified. Regarding thermal degradation, the maximum degradation rate temperature was shifted 46 °C from pH4 to 11. Differences in water vapour permeability, colour, opacity, and roughness of films were also found. According to the results of differential protein solubility assay, hydrophobic interactions and hydrogen bonding were promoted at pH4, but disulfide bonds were benefited at pH 11, in addition to partial β-glucan dissolution and break-up of the alkali-sensitive linkage in molecules from the cell wall. The results lead to the conclusion that film-functional characteristics were greatly benefited at pH 11 in comparison with the regular pH of dispersion (pH6). These results could help in understanding and selecting the pH conditions to enhance the desired properties of yeast biomass films. © 2021 Society of Chemical Industry.

Flexible, Strong, Multifunctional Graphene Oxide/Silica-Based Composite Aerogels via a Double-Cross-Linked Network Approach.

Multifunctional silica-based aerogels are an emerging material due to their unique properties and wide applications. However, their large-scale production and application are limited due to the high cost and cumbersome preparation process. Herein, we prepare graphene oxide (GO)/silica-based composite aerogels via a simple in situ sol-gel reaction. GO nanosheets (GOs) are functionalized with polyethylenimine (PEI) and 3-glycidyloxypropyltrimethoxysilane (GPTMS) successively. After a cohydrolysis and condensation of trimethoxymethylsilane (MTMS) and dimethoxydimethylsilane (DMDMS) in the presence of GOs and a convenient ambient-pressure drying process, the composite aerogels are obtained. In addition to the normal cross-linking of MTMS and DMDMS, the GOs also behave as cross-linking points to significantly enhance the mechanical properties and thermal stability of the network of the composite aerogels. The pore structure of the aerogels is tailored by varying the GO loads as well as its surface modification. The Young's modulus of a composite aerogel with a GO load of 0.5 wt % is about 5 times that for a neat polysiloxane aerogel, and the maximum degradation rate temperature is increased to over 90 °C. Compared with pure polysiloxane aerogel, the thermal insulation and flame resistance are also improved by a small addition of GOs. Moreover, GO/silica-based composite aerogels show stable piezo-resistive behavior. With the excellent mechanical properties, thermal stability, and multifunctionality, GO/silica-based composite aerogels show promising applications under some harsh and extreme conditions.

Physicochemical composition of different parts of cassava (Manihot esculenta Crantz) plant

Cassava (Manihot esculenta Crantz) is one of the main sources of carbohydrate and it is a useful plant in Malaysia. Its root is used to produce various foods such as cassava chips, while the other parts are potentially to produce feeds and other useful products. However, details observation in the proximate composition of each part of the cassava plant is important in utilizing it as an animal feed, especially for the ruminants. Hence, this research was conducted to evaluate the proximate composition of each part in the cassava plant and characterized its functional groups using Fourier-transform infrared spectroscopy (FTIR) and the thermal properties using thermogravimetric analyzer (TGA). The results obtained showed that the portions of fresh cassava plants namely flesh, stem, peel, discarded tuber and the leaf were recorded at 50.06%, 31.01%, 10.63%, 6.92% and 1.49% (w/w), respectively. Proximate analysis showed that the leaf has potential as animal feed as it contains significant high in crude protein (28.02±0.10%), crude fat (5.63± 0.12%) and the gross energy value of 4824.3 g/cal. Even though the leaf has a higher cyanide content (0.02 mg/kg) than other parts, it is still in acceptable range as an ingredient in animal feed. For animal feed that focuses on high protein and gross energy, the leaf has potential in feed ingredients. Meanwhile, cassava flesh also has potential as an animal feed since it has low crude fiber (2.11±0.03%) but high in carbohydrate (92.66±1.88%) and gross energy content (4223.9 cal/g). FTIR spectra showed that there were different functional groups present in the samples. From the TGA data, it showed that the major components in samples were cellulose which started to decompose rapidly at maximum degradation rate temperature of 315-400°C, especially for flesh and discarded tuber. Different parts of cassava plants are expected to help the agriculture industry in producing alternative animal feed at the same time minimizing the impact of waste generated in the environment.

Water-Responsive and Mechanically Adaptive Natural Rubber Composites by in Situ Modification of Mineral Filler Structures.

A new biomimetic stimuli-responsive adaptive elastomeric material, whose mechanical properties are altered by a water treatment is reported in this paper. This material is a calcium sulphate (CaSO4) filled composite with an epoxidized natural rubber (ENR) matrix. By exploiting various phase transformation processes that arise when CaSO4 is hydrated, several different crystal structures of CaSO4· xH2O can be developed in the cross-linked ENR matrix. Significant improvements in the mechanical and thermal properties are then observed in the water-treated composites. When compared with the untreated sample, there is approximately 100% increase in the dynamic modulus. The thermal stability of the composites is also improved by increasing the maximum degradation rate temperature by about 20 °C. This change in behavior results from an in situ development of hydrated crystal structures of the nanosized CaSO4 particles in the ENR matrix, which has been verified using Raman spectroscopy, transmission electron microscopy, atomic force microscopy, and X-ray scattering. This work provides a promising and relatively simple pathway for the development of next generation of mechanically adaptive elastomeric materials by an eco-friendly route, which may eventually also be developed into an innovative biodegradable and biocompatible smart polymeric material.

Comparative study of encapsulated peppermint and green tea essential oils in chitosan nanoparticles: Encapsulation, thermal stability, in-vitro release, antioxidant and antibacterial activities

Essential oils (EOs) such as Peppermint oil (PO) and Green Tea oil (GTO) have extensively been reported for their nutritional and biomedical properties. To overcome the sensitivity of EOs to the environmental conditions, nano-encapsulation has emerged as a method to address this limitation. In this work, PO and GTO were encapsulated in chitosan nanoparticles (CS NPs) following emulsification/ionic gelation method. The nano-encapsulated PO (CS/PO NPs) and GTO (CS/GTO NPs) were fully characterized by various methods. Spherical NPs with an average size range of 20–60 nm were revealed by TEM for both systems. The loading capacity reached 22.2% and 23.1%, for PO and GTO, respectively, and the in-vitro release followed a Fickian behavior in different buffer systems. The TGA thermograms of both nano-encapsulated EOs showed an increase in the temperature of maximum degradation rate up to 350 °C. The nano-encapsulation maintained the stability of the total phenolic contents in both EOs, improved the antioxidant activity by ~2 and 2.4-fold for PO and GTO respectively. Surprisingly, the antibacterial activity of CS/GTO NPs was more potent than CS/PO NPs and especially against Staphylococcus aureus with ~9.4 folds improvement compared to pure GTO, and ~4.7 fold against Escherichia coli.

Thermal, Mechanical, and dielectric properties of Injection Molded Graphene Nanocomposites Based on ABS/PC and ABS/PP Blends

In this research, graphene nanocomposites of poly(acrylonitrile‐butadiene‐styrene)/polycarbonate (ABS/PC) and ABS/polypropylene (ABS/PP) blends were prepared by melt blending and their thermal and mechanical properties were studied. The incorporation of graphene into ABS/PC and ABS/PP blends caused a significant decrease of their melt flow index values. Although graphene led to reduction of onset degradation temperature (Tonset) and maximum degradation rate temperature (Tpeak) of ABS/PC blends, and mainly of pure PC, the obtained residue from thermogravimetric analysis showed an increase. The thermal degradation of PC phase, in PC‐rich blends, was completed at higher temperatures. In ABS/PP blends, the effect of graphene was an outstanding increase ofTonsetandTpeakin the case of pure PP, while increasing the residue at all proportions. Regarding the Young's modulus, in ABS/PC blends the result of the addition of graphene was dependent on the blend composition. In ABS/PP hybrids, the elastic modulus increased by the incorporation of graphene and this increase, reached anabout 43% in pure PP. The addition of graphene to pure ABS, pure PP and their blend 50/50 w/w resulted in an increasing trend of the dielectric constant (κ′), whereas the loss factor (tanδ) was similar in non‐reinforced and graphene‐reinforced samples, within the entire range of the examined frequencies. POLYM. COMPOS., 40:E1662–E1672, 2019. © 2018 Society of Plastics Engineers

Nanocomposites of Polyethylene Blends Using Organomica

SummaryThis study aims to incorporate LLDPE into HDPE in order to improve its processability, as well as to employ a nanoclay for maintaining the HDPE stiffness. Thermal, dynamic‐mechanical and rheological properties of polyethylene composites were investigated. Muscovite mica was treated with lithium nitrate for seven cycles, followed by exchange with quaternary ammonium salt to produce organomica. Initially, organomica was added to HDPE at 2% wt. using a tween‐screw mini‐extruder. The blend HDPE/LLDPE (1:1 by weight) was also evaluated at the same mica content, with and without the introduction of maleated polyethylene (PEMA) as compatibilizer in order to increase adhesion of polymers with the mineral clay. The samples were evaluated by thermogravimetry (TGA), while melting and crystallization temperatures, and the degree of crystallinity were measured by differential scanning calorimetry (DSC). Rheological properties were evaluated during blending using viscosity and torque curves as a function of processing time. The results showed that stability to thermal degradation of the polyethylene blend with mica increased with the addition of 2% wt. PEMA, where the temperature of maximum degradation rate overcame that of HDPE. The melting endotherm remained narrow in the mixture HDPE/LLDPE/mica, showing good miscibility of the polymer blend; and there was a slight decrease in the melting temperature. The reduction in viscosity during blending revealed improved processing conditions.

Development of Nanocomposites Reinforced with Carboxylated Poly(ether ether ketone) Grafted to Zinc Oxide with Superior Antibacterial Properties

Novel poly(ether ether ketone) (PEEK) based nanocomposites have been fabricated via melt-blending by addition of a carboxylated polymer derivative covalently grafted onto the surface of hydroxyl-terminated ZnO nanoparticles. Their morphology, thermal, mechanical, tribological, and antibacterial properties have been analyzed and compared with those of composites reinforced with pristine ZnO. The Fourier transform infrared (FT-IR) spectra corroborate the success of the grafting reaction, showing the appearance of signals related to ester linkages. Microscopic observations demonstrate that the polymer grafting improves the nanoparticle dispersion within the matrix. A progressive rise in thermal stability and flame retardant ability is found with increasing ZnO concentration, with an exceptional increment in the maximum degradation rate temperature of 70 °C at 5.0 wt % loading. The crystallization and melting temperature of PEEK decrease upon incorporation of the grafted nanofillers, attributed to the restrictions on polymer chain mobility and crystal growth imposed by the strong ZnO-matrix interactions. Nanocomposites with polymer-grafted nanoparticles exhibit higher stiffness, strength, ductility, toughness and glass transition temperature whilst lower coefficient of friction and wear rate than the neat polymer and composites with bare ZnO. Further, they show superior antibacterial activity against both the Gram-negative Escherichia coli and the Gram-positive Staphylococcus aureus bacteria. The antimicrobial effect increases upon raising nanoparticle content, and is stronger on E. coli. The approach used in this work is a simple, scalable, and efficient method to improve the performance of PEEK/ZnO nanocomposites for use in biomedical applications such as trauma, orthopedics, and spinal implants.

Influence of alkaline metal ions on flame retardancy and thermal degradation of cellulose fibers

Cellulose-Na and cellulose-K fibers are obtained by alkalization and etherification of viscose fiber. Flame retardancy and thermal degradation of cellulose-Na and cellulose-K fibers are investigated using limiting oxygen index (LOI), cone calorimetry (CONE), thermal gravimetry (TG), and differential TG (DTG). The LOI values of cellulose-Na and cellulose-K fibers are 33 and 30, compared with about 20 for viscose fiber. In CONE studies, cellulose-Na and cellulose-K fibers show much lower heat release rates, total heat release and effective heats of combustion than viscose fiber does. In addition, TG and DTG studies reveal that the second initial degradation temperature, the temperature of maximum degradation rate and the maximum degradation rate for cellulose-Na and cellulose-K fibers are much lower than those of viscose fiber. Cellulose-Na and cellulose-K fibers generate much more residue or carbonaceous char than viscose fiber does. Scanning electron microscopy studies of combustion residues after LOI testing indicate that cellulose-Na and cellulose-K fibers produce massive, thick residue crusts.

Analysis of Phyllostachys pubescens Bamboo Residues for Liquefaction: Chemical Components, Infrared Spectroscopy, and Thermogravimetry

Residues of Phyllostachys pubescens bamboo obtained from central Louisiana, USA, were comprehensively investigated for use in liquefaction. The results showed that bamboo branches had the highest Klason lignin and ash content, about 26% and 2.75%, respectively. The epidermis layer sample had relatively higher carbohydrate content, while the wax layer sample had the highest hot water and ethanol-toluene extractives and starch content. The results indicated that the bamboo processing residues showed potential for different chemical feedstocks. No significant differences were found in the infrared spectroscopy (FTIR) spectra of the different samples, indicating that the chemical functional groups were the same, despite variation in chemical components between samples. Klason lignin isolated from the residues showed a higher maximum degradation rate temperature (501 °C) and wider degradation temperature range (200 to 550 °C) than the carbohydrates.

Lipase-catalyzed synthesis of aliphatic polyesters via copolymerization of lactide with diesters and diols

Aliphatic lactate-bearing copolyesters were successfully synthesized via copolymerization of L-lactide (LLA) with diesters and diols using Candida antarctica lipase B (CALB) as the catalyst. The resultant copolymers had a Mw up to 38,000 Da with Mw/Mn between 1.5 and 2.0, and contained L-lactate units (up to 53 mol%), C6–C12 diester units, and C4–C6 alkylene units in the polymer chains. The lactate repeat units were present primarily as lactate–lactate diads in the polymers. The LLA-diester-diol copolymers were purified in good yield (70–85%) and all purified copolymers were optically active. Hydrolytic degradation study shows that LLA-diethyl adipate-1,6-hexanediol (LLA-DEA-HD) copolymers are degradable polymers as the molecular weight (Mw) of the copolymer with 53% lactate units decreased by ∼70% upon incubation in PBS solution under physiological conditions (37 °C, pH of 7.4) for 80 days. The LLA-diester-diol copolymers are thermally stable up to at least 300 °C with the temperature of maximum degradation rate ranging from 380 to 410 °C. The copolymers exhibit a wide range of physical properties (e.g., from white solid to wax and liquid) depending on their structure and composition. In particular, the LLA-DEA-HD and LLA-DEA-1,4-butanediol copolymers with ∼50 mol% lactate units are colorless, viscous liquids at ambient temperature. Biodegradable liquid polymers are potentially useful biomaterials for drug delivery to treat ocular ailments because of their good compatibility with sensitive soft tissues.

Effect of Sodium Ion on Flame Retardance and Thermal Degradation of Cellulose Fiber

Flame retardance and thermal degradation of CMC-Na fibers were investigated using limiting oxygen index (LOI), thermal gravimetry (TG), differential TG (DTG) and Scanning electron microscopy (SEM). The LOI values of different CMC-Na fibers are 23, 26, 28.5, 31 and 34, compared with about 20 for viscose fiber. TG and DTG studies indicate that the temperature of maximum degradation rate and the maximum degradation rate for CMC-Na fibers are much lower than those of viscose fiber. However, CMC-Na fibers generate much more residues or carbonaceous char than does viscose fiber. The increase of sodium ion content, the carbon residual also increases. SEM studies of combustion residues after LOI testing indicate that all CMC-Na fibers produce intumescent, hard and brittle residue crusts.