Maximum Weight Loss Temperature Research Articles

Preparation and properties analysis of CTBN/CeO2 co‐toughened epoxy resin composites

AbstractIn this paper, carboxyl‐terminated nitrile rubber (CTBN) and Nano cerium oxide (n‐CeO2) were used to toughen epoxy resin (EP), and the effects of toughening agents on the mechanical and thermal properties of EP were studied. Orthogonal experiments determined that the ideal toughener proportions are 20 wt% CTBN and 1 wt% n‐CeO2, under which the resin demonstrated superior mechanical characteristics. The combined application of CTBN and n‐CeO2 significantly enhanced the resin's mechanical properties, surpassing the effects of individual particle toughening. Compared with pure EP, the impact, flexural, and tensile strengths of the resin‐cured product synergistically toughened by CTBN and n‐CeO2 increased by 462%, 136%, and 110%, respectively, and the flexural and Young's moduli increased by 38% and 35%, respectively. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) were used to characterize the cured resin. The results indicate that incorporating CTBN and n‐CeO2 reduces the reaction activation energy, thereby accelerating the curing reaction and facilitating its progression. The addition of nanoparticles enhances the maximum weight loss temperature of the cured resin, thereby improving its thermal stability. CTBN and n‐CeO2 particles create a uniform phase separation structure within the resin, enhancing its toughness and strength. Furthermore, the impact fracture mode of the cured resin transitions from brittle to tough fracture, demonstrating a significant toughening effect. This provides an effective method for the toughening modification of EP.Highlights The synergistic use of CTBN and n‐CeO2 enhances the toughness of EP. The incorporation of nanoparticles improves the thermal stability of the cured resin. The addition of CTBN and n‐CeO2 accelerates the curing reaction rate. The inclusion of toughening agents transforms the fracture mode of the cured resin from brittle to tough fracture.

Imidazole ionic liquid effects on coal swelling behavior and pyrolysis characteristics: Experiment and molecular simulation

In view of low-rank coal conventional swelling solvent large pollution and the clean efficient utilization of coal, the effects of imidazole ionic liquid (IL) pretreatment with different anion groups as green solvent on coal thermal expansion and pyrolysis performance were investigated. IL interacts with coal molecules, destroying the hydrogen bonds, resulting coal expansion. Different anion groups have different modification effects, [Bmim]Cl has the best swelling effect, which is 17.37 % higher than raw coal, and the best modification time is 24 h. In addition, IL modification has a catalytic effect on coal pyrolysis, which can significantly reduce the maximum weight loss temperature and increase tar content. Coal solvent pretreatment provides a good theoretical basis for application of swelling and pyrolysis. The reduction of thermochemical reaction temperature not only reduces the content of heavy groups in pyrolysis products, but also provides new ideas for carbon emission reduction.

Carbon tube‐gypsum reinforced polypropylene: Impact resistance, thermal stability

AbstractThis study investigated the effect of multi‐walled carbon nanotubes (MWCNTs) and reclaimed gypsum of varying contents on the mechanical properties and thermal stability of polypropylene (PP) composite materials. The results indicated that the incorporation of reclaimed gypsum and MWCNTs powder into PP composites could enhance the tensile strength, impact strength, and bending modulus of PP to a certain extent. The above properties of AGY/MWCNTs/PP composites were increased by 14.6%, 131.8%, and 36.2%, respectively, with the impact properties being significantly affected. Univariate analysis of variance revealed that MWCNTs powder and recycled gypsum exerted a significant impact on the mechanical properties of polypropylene composites. Moreover, the initial weight loss temperature of AGY/MWCNTs/PP demonstrated a notable increase, from 318.71 to 398.48°C, while the maximum weight loss temperature exhibited a comparable rise, from 406.85 to 461.54°C.Highlights The impact performance and thermal stability of polypropylene composite materials have been demonstrably augmented. A synergistic effect between reclaimed gypsum and multi‐walled carbon nanotubes in the reinforcement of polypropylene composites was demonstrated. This provides a theoretical framework and practical guidance for the design and preparation of high‐performance and recyclable polymer composites.

Study on microstructure evolution and oxidation kinetics in Coal-Oil Symbiosis

Differences in the spontaneous combustion mechanism characteristics of Coal-Oil Symbiosis (COS) significantly affect coal mines' safety management and ecological environment maintenance. Accordingly, this study aims to investigate COS's macroscopic and microstructural characteristics with different oil mass percentage using simultaneous thermal analysis, low-temperature N2 adsorption, scanning electron microscopy (SEM), and in-situ Fourier transform infrared spectroscopy (FTIR). The results showed that with the increase of oil mass percentage, the COS displayed the weakening of oxygen absorption and the advance of some characteristic temperatures, and 11.5 °C advanced the maximum weight loss temperature on average. For the 25 % oil sample, the ignition temperature was 9.5 °C lower than that of the raw coal. Additionally, the apparent activation energy of the high oil mass percentage sample was significantly reduced in the pyrolysis and combustion stages, and when the oil mass percentage was 25 %, the activation energies of the two stages decreased by 89 % and 60.65 %, respectively. Compared to raw coal, COS exhibits fewer macropores and surface pores covered by oil, which limits oxygen adsorption. Moreover, COS with higher oil mass percentage had an increase in hydroxyl and aliphatic hydrocarbon groups, and the CH3 + CH2 content of COS increased by 69.2 % on average, providing more active groups, thereby promoting spontaneous combustion. This study provides an important reference and theoretical support for further understanding the structural evolution and oxidation kinetic behavior of COS, contributing to disaster prevention and ecological environmental protection in coal-oil coexistence mining areas.

Preparation of microencapsulated physicochemical composite retardant and study of the flame retardant mechanism

In order to solve the shortcomings of traditional inhibitors, which are easy to be interfered by the outside world during the inhibition process and the active ingredients are easy to be oxidized and invalidated, microencapsulated inhibitors were developed. In this study, we prepared microencapsulated inhibitors of varying wall-to-core ratios using a composite phase of polyethylene glycol 20,000 (PEG-20000) and octenyl amyl succinate (OSAS) as the wall material and a lauryl glucoside (APG-12) and butyl hydroxyanisole (BHA) phase as the core material. After thoroughly mixing the microcapsule inhibitor with coal samples, simultaneous thermal analyzer (TG/DSC) and a temperature-programmed system were used to evaluate the resisting qualities of the produced microencapsulated inhibitors. The results of the temperature programmed experiment showed that the overall CO release from the blocked coal samples was less than that of the original coal. According to thermogravimetric results, the most effective inhibition occurred when the wall/core ratio of the microcapsule inhibitor was 4:1. This also resulted in a reduction of the maximum coal weight loss rate from 1.34 to 0.96 %/min and an increase in the maximum coal weight loss temperature from 477.4 to 507.6 °C. The microencapsulated inhibitor melts in the wall at 57.4 °C, enabling temperature-sensitive intelligent control of core release. Following heating the raw and inhibited coal samples to 100 and 200 °C, respectively, Fourier infrared spectroscopy was conducted. At these temperatures, the amounts of ether bonds increased by 20.4 and 22.6 %, and the number of free hydroxyl groups decreased by 12.8 and 2.7 %, respectively, in the inhibited coal samples. Finally, molecular dynamics theory was applied to investigate the inhibitory mechanism. The prepared microcapsule retardant effectively inhibited the spontaneous combustion reaction of coal, suggesting this microcapsule inhibitor could be manufactured as a novel inhibitor for coal spontaneous combustion.

Lipase-catalyzed synthesis and characterization of medium-long-medium (MLM) type structured triacylglycerols from peony seed oil

Structured triacylglycerols (STAGs) with medium-chain fatty acids (FAs) at sn-1,3 positions and long-chain FAs at the sn-2 position are known as medium-long-medium (MLM) type STAGs. They can not only provide energy immediately and control weight effectively, but may also provide essential or beneficial FAs to meet the human needs. In this study, MLM type STAGs were synthesized from lipase-catalyzed acidolysis of peony seed oil (PSO) with octanoic acid (OcA) and decanoic acid (DA) as medium-chain FAs in solvent-free systems. Optimal reaction conditions were 1:8 (PSO to OcA/DA), 40 °C and 24 h. The OcA content and DA content at sn-1,3 of two STAGs were 81.1% and 82.5%. The total essential FA (α-linolenic acid and linoleic acid) contents at sn-2 reached 61.5% and 57.2%, and long-chain unsaturated FA contents reached 93.3% and 87.4%. Infrared absorptions of two STAGs were weaker than those of PSO at 723 cm−1 [-(CH2)n-rocking] and 3011 cm−1 [ = CH (cis) stretching]. The end melting temperature and maximum weight loss temperature of STAG rich in DA were higher than those of STAG rich in OcA. This study is conducive to the deep processing of PSO and provides a new and promising substrate for MLM type STAG synthesis.

Fine extraction of cellulose from corn straw and the application for eco-friendly packaging films enhanced with polyvinyl alcohol

Biomass materials substituting for petroleum-based polymers occupy an important position in achieving sustainable development. Cellulose, a typical biomass material, stands out as the primary choice for producing eco-friendly packaging materials. However, it is still a challenge to efficiently utilize cellulose from waste biomass materials in practice. Herein, cellulose-based films were prepared by pretreating waste corn straw, separating straw husk, straw pith and straw leaf, and extracting cellulose through alkali and sodium chlorite treatment to improve its mechanical properties using the cross-linked polyvinyl alcohol (PVA) method in this work. The prepared composite films were characterized by Fourier transform infrared spectrometer (FTIR), X-ray diffraction instrument (XRD), Scanning electron microscopy (SEM), Thermogravimetric (TG) and mechanical properties. The results indicated that corn straw husk exhibited the highest cellulose content of 31.67 wt%, and obtained husk cellulose had the highest crystallinity of 52.5 %. Compared to corn straw, the crystallinity of husk cellulose, pith cellulose and leaf cellulose increased by 19.5 %, 16.4 % and 44.1 %, respectively. Husk cellulose/PVA composite films were the most thermally stable, with a maximum weight loss temperature of 346.8 °C. In addition, the husk cellulose/PVA composite film had the best tensile strength of 37 MPa. Meanwhile, the composite films had good UV shielding, low water vapor transmission rate and biodegradability. Therefore, this work provides a fine utilization route of waste corn straw, and as-prepared cellulose based films have potential application in eco-friendly packaging materials.

Effect of polyphenylene sulfide sulfone sizing agent on interfacial, thermal, and mechanical properties of carbon fiber

AbstractPolyphenylene sulfide sulfone (PPSS) was synthesized by one‐step method and utilized as a sizing agent for carbon fibers. The effects of various monomer ratios, reaction time, and reaction temperature were investigated on the molecular weight of PPSS. The thermal analysis revealed that the product PPSS exhibited a glass transition temperature exceeding 215.5°C, indicating exceptional thermal stability. After PPSS sizing treatment, the grooves on the surface of carbon fibers were filled, resulting in a substantial enhancement of the microinterface properties. The surface energy was increased by 8.2%, while the maximum weight loss temperature was 27.8% higher than that of the commercial carbon fiber. The tensile strength of the carbon fiber after heat treatment reached 2196 MPa, representing a 45.9% increase over that of the commercial carbon fiber.

Enhancing osteoblast proliferation and bone regeneration by poly (amino acid)/selenium-doped hydroxyapatite

Among various biomaterials employed for bone repair, composites with good biocompatibility and osteogenic ability had received increasing attention from biomedical applications. In this study, we doped selenium (Se) into hydroxyapatite (Se-HA) by the precipitation method, and prepared different amounts of Se-HA-loaded poly (amino acid)/Se-HA (PAA/Se-HA) composites (0, 10 wt%, 20 wt%, 30 wt%) by in-situ melting polycondensation. The physical and chemical properties of PAA/Se-HA composites were characterized by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and their mechanical properties. XRD and FT-IR results showed that PAA/Se-HA composites contained characteristic peaks of PAA and Se-HA with amide linkage and HA structures. DSC and TGA results specified the PAA/Se-HA30 composite crystallization, melting, and maximum weight loss temperatures at 203.33 °C, 162.54 °C, and 468.92 °C, respectively, which implied good thermal stability. SEM results showed that Se-HA was uniformly dispersed in PAA. The mechanical properties of PAA/Se-HA30 composites included bending, compressive, and yield strengths at 83.07 ± 0.57, 106.56 ± 0.46, and 99.17 ± 1.11 MPa, respectively. The cellular responses of PAA/Se-HA composites in vitro were studied using bone marrow mesenchymal stem cells (BMSCs) by cell counting kit-8 assay, and results showed that PAA/Se-HA30 composites significantly promoted the proliferation of BMSCs at the concentration of 2 mg ml−1. The alkaline phosphatase activity (ALP) and alizarin red staining results showed that the introduction of Se-HA into PAA enhanced ALP activity and formation of calcium nodule. Western blotting and Real-time polymerase chain reaction results showed that the introduction of Se-HA into PAA could promoted the expression of osteogenic-related proteins and mRNA (integrin-binding sialoprotein, osteopontin, runt-related transcription factor 2 and Osterix) in BMSCs. A muscle defect at the back and a bone defect at the femoral condyle of New Zealand white rabbits were introduced for evaluating the enhancement of bone regeneration of PAA and PAA/Se-HA30 composites. The implantation of muscle tissue revealed good biocompatibility of PAA and PAA/Se-HA30 composites. The implantation of bone defect showed that PAA/Se-HA30 composites enhanced bone formation at the defect site (8 weeks), exhibiting good bone conductivity. Therefore, the PAA-based composite was a promising candidate material for bone tissue regeneration.

How the Crosslinker Amount Influences the Final Properties of Hydroxyethyl Methacrylate Cryogels.

The investigation of the mechanical, thermal, and adsorption properties of hydroxyethyl methacrylate (HEMA) cryogels as a function of a reactant ratio is herein reported to better address materials for specific applications. To this aim, cryogels have been synthesized using different monomer/crosslinker (N,N'-methylene-bisacrylamide-MBAA) ratios. The study of SEM images made it possible to identify the trend in the material's macroporosity. As would be expected, the average measured pore width decreased as the amount of MBAA increased while the number of pores grew. Swelling capacity ranges from 8.7 gW/ggel (grams of water per gram of gel) to 9.3 gW/ggel. These values are strictly connected with the pore's size and distribution, revealing that the water uptake for the most crosslinked sample is inferior to other samples. The equilibrium-adsorption capacity (Qe) towards the methylene violet (MV) was also assessed, revealing no remarkable differences after 24 h of a batch test. As expected, thermogravimetric analysis (TGA) also showed no significant changes in stability that ranged from a maximum weight loss temperature (T Max) of 420 °C to 425 °C, which increased as a function of crosslinker content. Conversely, compression strength measurements showed a notable difference of about 50% in modulus (Ec), moving from the higher to the lower HEMA/MBAA ratio. These new comparative results indicate how slight variations in the reactant's ratio can steadily improve the mechanical properties of the HEMA cryogel without affecting its adsorption efficiency. This can be helpful in the design of materials for water and energy purposes. Since swelling properties are needed in the case of biomedical applications, the HEMA/MBAA ratio should be tuned versus high values.

Effect of using biodegradable film constituting red grape anthocyanins as a novel packaging on the qualitative attributes of emergency food bars during storage.

This study presents a novel packaging film based on whey protein isolate/κ-carrageenan (WC) with red grape pomace anthocyanins (RGA) to investigate its impact on some qualitative attributes of emergency food bars (EFBs) for 6 months at 38°C. Increasing the RGA dose in WC films from 5% (WCA5) to 10% (WCA10) reduced hydrogen bonding between polymers and polymer homogeneity in the matrix according to FTIR and SEM. Tensile strength slightly declined in WCA5 from 7.47 ± 0.26 to 6.97 ± 0.12, while elongation increased from 27.74 ± 1.36 to 32.36 ± 1.25% compared to WC film. The maximum weight loss temperature (TM) increased by incorporating 5 wt% RGA from 182.95°C to 244.36°C, whereas TM declined to 187.19°C in WCA10 film. WVP and OTR slightly changed in WCA5 (from 7.83 ± 0.07 and 2.57 ± 0.18 to 8.41 ± 0.03 g H2O.m/m2.Pa.s × 10-9 and 1.79 ± 0.32 cm3 O2/m2.d.bar, respectively), but significantly impaired in WCA10 compared to WC film. WCA5 and WCA10 films had high AA%, 68.77%, and 79.21%, respectively. WCA10 film presented great antimetrical properties against Staphylococcus aureus with an inhibition zone of 6.00 mm. The light transmission of RGA-contained films in the UV spectrum was below 10%. The WCA5 film effectively restrained moisture loss and hardness increment until the end of the storage period, which were 14.33% and 28.76%, respectively, compared to day 0. Antioxidant films provided acceptable resistance against oxidation to EBF treatment. Sensory panels scored WCA5 and WCA10 higher in overall acceptance with 5.64 and 5.40 values, respectively, while complaining about the hardness of OPP treatment. The results of this investigation demonstrated that incorporating RGA, preferably 5 wt%, into WC-based film effectively improved the qualitative properties of EFB during the 6-month shelf life. This film might be a promising alternative for packaging light and oxygen-sensitive food products.

Grafting modification bamboo kraft lignin and its performance in rigid polyurethane foams

AbstractIn order to improve the efficiency of intumescent flame retardant (IFR), bamboo kraft lignin (BKL) was chemically functionalized by grafting melamine (MEL) and diethyl phosphite (DEP) and used for rigid polyurethane (RPU) foam. The BKL, MEL, and DEP in IFR system were used as char forming agent, gas, and acid source, respectively. The FTIR and XPS results indicated that the nitrogen (N) and phosphorus (P) containing BKL was successfully synthesized. The limiting oxygen index (LOI) value of N‐BKL and N/P‐BKL RPU foams were higher than BKL RPU foam, suggesting that N‐BKL and N/P‐BKL improved flame retardancy of the foams. The total heat release (THR), heat release rate (HRR), effective heat of combustion (EHC), and fire growth rate (FIGRA) values of N‐BKL and N/P‐BKL RPU foams were much lower than that of BKL RPU foam. The flame retardancy index value of N/P‐BKL RPU foams was higher comparing to N‐BKL RPU foam. These results indicated that the synergistic interaction between N containing compound of MEL and P containing compound of DEP led to the improvement flame retardant properties. Comparing to BKL RPU foam, the N/P‐BKL RPU foam increased 74°C of maximum weight loss temperature and decreased 18.1 wt% of mass loss, indicating enhanced thermal stability. The morphology of char after cone calorimeter testing showed the N/P‐BKL RPU foam presented more continuous and compact char residues, which could reduce heat and mass transfer, protecting underlying materials from further combustion in a fire, thus resulting in good flame retardancy and thermal stability properties. This work suggests a promising route to enhancing the flame‐retardant performance of RPU foam using nontoxic and more environmentally friendly grafted bamboo lignin.

Ball milling‐assisted exfoliation and deposition to prepare few‐layer graphene/PVC nanocomposites with enhanced thermal stability

AbstractIt is still a great challenge to prepare high‐performance graphene/polymer nanocomposites by fully utilizing the large surface area, high tensile strength, and high thermal stability. Herein, a simple but efficient approach based on ball milling was developed to in situ exfoliate graphite into single‐layer graphene and simultaneously deposit them onto polyvinyl chloride (PVC) surface. Graphene/PVC nanocomposites were prepared via the plasticized molding and followed by hot pressing. Resulting from incorporation of highly exfoliated and evenly distributed graphene nanosheets, the obtained graphene/PVC nanocomposites displayed a significantly enhanced thermal stability. In contrast with neat PVC, the temperature of maximum weight loss (Tmax), glass transition temperature (Tg), and residual content of composite with 2.0 wt% graphene were increased by 10, 13°C, and 4.4%, respectively. Based on the deep analysis on heat releasing behavior and structure of residue, we proposed the related enhancing mechanism. Large‐area and highly exfoliated graphene sheets effectively inhibited the heat/mass transfer in composite system and prevented the degradation of PVC, as well as promoted the compact residue formation from polymer itself at high temperatures. In short, this work provided an environmentally friendly strategy to prepare high‐performance graphene/polymer nanocomposites with using low additive amount of single‐layer graphene.Highlights A simple graphite exfoliation method based on ball milling was proposed. Strong shearing and compact force induce graphene exfoliation and deposition. Graphene/PVC nanocomposites with enhanced thermal stability was prepared.

Epoxy resin with both ultraviolet shielding and enhanced thermal mechanical properties: Study on synergistic modification of Ce–Zr–Si oxide nanoparticles and basalt fibers

AbstractComposites with good thermomechanical and UV‐shielding properties are essential in fiber‐reinforced composites. This paper focuses on composites' ultraviolet (UV) shielding efficiency with added Ce‐Zr‐Si oxide nanoparticles/epoxy resin. The Ce‐Zr oxide nanoparticles were first functionalized with a silicon coupling agent and ethyl silicate to improve their dispersion and surface activity. In this work, we prepared epoxy nanocomposites with the addition of Ce‐Zr ‐Si oxides(1,3,5,7 wt%) and found that the materials had good enhancement of the UV shielding properties of the epoxy resin matrix. Meanwhile, it was used in basalt fiber (BF)/epoxy composites prepared by the hot‐pressing method, and surface treatment of basalt fibers was carried out. The results showed that the modified fiber composites could effectively enhance the thermomechanical properties of epoxy resin composites. It is noteworthy that the tensile strength and flexural strength of the hybrid composites reached their peak when 5 wt% Ce‐Zr‐Si was added, increasing by 13.8% and 33.67% respectively. The modified (BF)/epoxy composites exhibited improved thermal stability compared to pure epoxy resin, with the maximum weight loss temperature of BF‐1/EP reaching 349°C. The T(UVA) decreased to 2.41%, while the T(UVB) decreased to 0.053%, and almost all the ultraviolet irradiation was blocked. These results show that our prepared composites have good thermomechanical and UV shielding properties.Highlights Ce‐Zr oxide nanoparticles were functionalized with a silicon coupling agent. Ce‐Zr‐Si oxide was added to enhance the ultraviolet shielding efficiency. Modified BFs were composited to improve thermomechanical properties.

Enhancing thermal and mechanical properties of pyridine-based polyester with isosorbide for high gas barrier applications

Driven by sustainable development and low-carbon policies, many high-performance bio-based polyesters are produced. Our previous work uncovered the high barrier but low thermal and mechanical properties of a renewable 2,6-pyridinedicarboxylic-based polyester. In this article, the copolymerization with isosorbide as a second diol is considered to ameliorate these properties. The chemical structures of copolyesters and the successful introduction of isosorbide were confirmed by FT-IR and 1H NMR. The 1H NMR spectra also allowed the calculation of isosorbide ratio in polymers. GPC revealed a decrease in molar masses with the increase of isosorbide ratio. Contact angle and water/gas permeation measurements disclosed an increase in hydrophilicity and water/gas permeability with the introduction of isosorbide. TGA and DSC analyses demonstrated an enhancement in thermal stability: 8 mol% of isosorbide to the total diol ratio increased the 5 % weight loss temperature (T5%) by 9 °C, the maximum weight loss temperature (Tmax) by 8 °C and the glass transition temperature (Tg) by 6 °C. DSC investigation showed that the incorporation of isosorbide significantly influenced the crystallization properties, particularly from the melt, by decreasing the crystallinity. XRD patterns indicated the presence of similar crystallization units in these polyesters. Tensile test revealed that incorporating 8 mol% of isosorbide greatly improved the mechanical properties by doubling Young’s modulus and tripling the strength at break. Such enhancement in thermal and mechanical properties is important for high gas barrier food packaging applications of these polyesters.

Preparation and performance of silicone-modified 3D printing photosensitive materials

Abstract Herein, the performance of silicone-modified 3D printing photosensitive resin was examined. Bisphenol-A epoxy acrylate (EA) was used as the substrate and isophorone diisocyanate, hydroxy-silicone oil, and hydroxyethyl acrylate were used as the raw materials. A silicone intermediate was synthesized to modify the substrate to prepare the 3D printing photosensitive material. The as-synthesized materials were characterized using Fourier transform infrared spectroscopy and scanning electron microscopy. The tensile fracture morphology was also analyzed. The effects of the addition of silicone intermediates on the mechanical properties, thermal stability, and shrinkage of the prepared 3D printing photosensitive resins were investigated. The results showed that an organosilicone group was successfully introduced into the side chain of EA. When the ratio of n(silicone):n(EA) is 0.3:1, the material has a high impact strength of 19.4 kJ·m−2, which is 32.8% higher than that of the pure resin; in addition, the elongation at break is 8.65% (compared to 6.56% of the pure resin). The maximum thermal weight loss temperature is 430.33°C, which is 6°C higher than that of the pure resin.

Efficient preparation of polyethylene glycol (PEG)-modified lignin from steam exploded hardwood biomass

The structures and characteristics of lignin derivatives prepared from steam exploded beech under alkali delignification and acid catalyzed polyethylene glycol (PEG) solvolysis were studied in detail. An efficient method for directly isolating PEG-modified lignin from wood was proposed to improve its thermal stability. The effects of steam explosion (SE) parameters and delignification process on lignin structure were studied by high performance anion exchange chromatograph, fourier transform infrared spectroscopy (FTIR), heteronuclear single quantum coherence (HSQC) NMR spectroscopies, ultraviolet and visible spectrophotometry, size exclusion chromatography (SEC) and thermogravimetric analysis (TGA). The results showed that SE pretreatment can greatly promote the yield of PEG-modified lignin. The PEG-modified lignin, isolated from steam exploded wood at 210 °C for 2.5 min, was ∼14% yield. The PEG moiety was located at the alpha carbon position of the β-O-4 linkage. The PEG-modified lignin exhibited improved thermal properties with a maximum weight loss temperature (Tdmax) greater than 380 ℃, and a degradation starting temperature (Tdst) in the range of 258–277 °C, met the temperature for polymer processing and contribute to improve the added value of lignin.

Effects of L‐ and D‐ form oligo(lactic acid)s grafted cellulose reinforcement on the thermal properties of poly(L‐lactic acid) composites

AbstractL‐ and D‐ form oligo(lactic acid)s (OLLA and ODLA) grafted α‐cellulose (OLLA‐g‐cellulose and ODLA‐g‐cellulose) were prepared by the graft polycondensation reaction in C6H5CH3 medium at 130°C and 380 mm of mercury pressure. Para‐toluene sulphonic acid (5 wt% of oligo(lactic acid)) was used as a catalyst whereas potassium persulfate (0.01 wt% of oligo(lactic acid)) was used as a co‐catalyst in the graft polycondensation reaction. OLLA and ODLA with a degree of polymerization (DP) 6–7 used in polycondensation reaction were also prepared by ring‐opening polymerization of L‐ and D‐lactides at 140°C for 10 h with stannous octoate (C16H30O4Sn) as a motivator, L, and D monomer of lactic acids as co‐motivators. FTIR analysis proved the bonding of OLLA and ODLA onto the α‐cellulose surface. The thermal properties of poly(L‐lactic) acid (PLLA) composites were explored by thermal analysis (TG, DTA, and DTG). Degradation, melting, and maximum weight loss temperature of the composites were increased with the increase of grafted cellulose up to 10% and then decreased. TG and DTA results showed that the incorporation of grafted α‐cellulose (grafted cellulose) can improve the thermal properties of PLLA composites.Highlights Synthesis of oligo(lactic acid)s from L‐ and D‐lactides by ring‐opening polymerization reactions. α‐cellulose extraction and graft modification with oligo(lactic acid)s. Preparation of grafted α‐cellulose composite with PLLA matrix. Evaluation of thermal properties of the grafted α‐cellulose‐reinforced composites.

INVESTIGATING THE EFFECT OF MICROWAVE IRRADIATION TIME, POLYETHYLENE GLYCOL CONCENTRATION AND pH ON THE PROPERTIES OF Mg-BASED BACTERIAL CELLULOSE NANOBIOCOMPOSITE

Mg-based bacterial cellulose nanobiocomposites (Mg-BCN) were produced assisted by microwave irradiation. In this study, the effects of the concentration of starter molecules, solution pH, and microwave irradiation time (MIT) on the properties of Mg-BCN were investigated. Tensile strength, structural properties, morphology and thermal stability of the nanocomposites were evaluated. According to the obtained results, an increase in the concentration ratio of starter molecules, pH, and MIT increased the formation of MgO, in comparison with Mg(OH)2. The nanocomposites synthesized with the 1:2 and 2:1 concentration ratio of magnesium acetate to polyethylene glycol, at pH 11 and with 3 minutes of MIT, had the largest tensile strength and crystallinity. Meanwhile, the opposite results were obtained with 1:1 and 1:0 ratios, at the mentioned pH and time. According to FESEM analysis, at pH = 9, the nucleation rate decreased and smaller particles were formed. Moreover, the results showed decreased possibility of agglomeration in the presence of polyethylene glycol (PEG). TGA results indicated that the thermal stability of all Mg-based nanocomposites is higher than that of pure cellulose. In addition, the maximum weight loss temperature in all treatments involving PEG was higher than in the case of the samples treated without PEG.

Study on the Re-ignition Characteristics of High-Temperature Oxidization & Water Immersion Long-Flame Coal at Different Heating Rates

ABSTRACT The water immersion residual coal tend to happen spontaneous combustion accidents after mining the coal seam. For exploring the oxidative re-ignition properties of high-temperature oxidized water-impregnated long-flame coal, the thermal evolution law toward each pre-oxidized coal soaked in water under varying heating rates (Rh) (5, 10, 15°C/min) has been analyzed by thermogravimetric differential scanning calorimetry (TG-DSC). The findings are as follows: the DTG at the critical temperature (T1) and maximum weight loss temperature (T5) increases, the activation energy (E) decreases, and the heat output increases (maximum 6391J/g) with the rising Rh. The violent oxidated reaction process of coal samples has been delayed as the Rh was 10°C/min. The water-immersed coal sample (I200) contains more free water on the surface, and the maximum (0.45 mW/mg) and total (178.8 J/g) heat absorption of are higher. Oxidation at 200°C and soaking in water (O200I200) reduced the ignition point temperature (minimum 399°C) and E (minimum 18.5 kJ/mol), and increased the total heat release (maximum 323 J/g) making it easier to oxidize and re-ignite. Under the same Rh, the oxidation and combustion traits of each pre-oxidized water-immersed coal (PWIC) remained unchanged. Reducing the Rh can effectively prevent spontaneous combustion of high-temperature oxidized water-soaked coal in shallow-buried and short-distance coal seams in northwest of China.