Short-chain Components Research Articles

Primitive Chain Network Simulations for Double Peaks in Shear Stress under Fast Flows of Bidisperse Entangled Polymers.

A few experiments have reported that the time development of shear stress under fast-startup shear deformations exhibits double peaks before reaching a steady state for bimodal blends of entangled linear polymers under specific conditions. To understand this phenomenon, multi-chain slip-link simulations, based on the primitive chain network model, were conducted on the literature data of a bimodal polystyrene solution. Owing to reasonable agreement between their data and our simulation results, the stress was decomposed into contributions from long- and short-chain components and decoupled into segment number, stretch, and orientation. The analysis revealed that the first and second peaks correspond to the short-chain orientation and the long-chain stretch, respectively. The results also implied that the peak positions are not affected by the mixing of short and long chains, although the intensity of the second peak depends on mixing conditions in a complicated manner.

Mechanically Robust Hemostatic Hydrogel Membranes with Programmable Strain-Adaptive Microdomain Entanglement for Wound Treatment in Dynamic Tissues.

Supramolecular hydrogels emerge as a promising paradigm for sutureless wound management. However, their translation is still challenged by the insufficient mechanical robustness in the context of complex wounds in dynamic tissues. Herein, we report a tissue-adhesive supramolecular hydrogel membrane based on biocompatible precursors for dressing wounds in highly dynamic tissues, featuring robust mechanical resilience through programmable strain-adaptive entanglement among microdomains. Specifically, the hydrogels are synthesized by incorporating a long-chain polyurethane segment into a Schiff base-ligated short-chain oxidized cellulose/quaternized chitosan network via acylhydrazone bonding, which readily establishes interpenetrating entangled microdomains in dynamic cross-linked hydrogel matrices to enhance their tear and fatigue resistance against extreme mechanical stresses. After being placed onto dynamic tissues, the hydrogel dressing could efficiently absorb blood to achieve rapid hemostasis. Moreover, metal ions released from ruptured erythrocytes could be scavenged by the Schiff base linkers to form additional ionic bonds, which would trigger the cross-linking of the short-chain components and establish abundant crystalline microdomains, eventually leading to the in situ stiffening of the hydrogels to endure heavy mechanical loads. Benefiting from its hemostatic capacity and strain adaptable mechanical performance, this hydrogel wound dressing shows promise for the clinical management of various traumatic wounds.

Synthesis of new extractant P113 for cerium(IV) extraction and higher separation over thorium from bastnaesite

Cyanex923 (a mixture of four trialkyl (hexyl and octyl) phosphine oxides) has been extensively employed in the recovery of cerium (Ce(IV)) and fluorine (F), as well as the separation over thorium (Th(IV)) from bastnaesite. However, rigorous production conditions and involvement of highly toxic raw materials (PH3) have been critical problems to be solved during the synthesis of Cyanex923. Meanwhile, its extraction performance remains to be improved. Therefore, we attempted to adjust the feed ratio to increase the proportion of short carbon chain components, successfully synthesized a novel extractant (P113, a mixture of four trialkyl (hexyl and octyl) phosphine oxides) with contents of each component different from Cyanex923 using an environmentally benign method. The comparison with Cyanex923 revealed obvious improvement of P113 in terms of extraction efficiency, selectivity and saturation capacity. The extraction efficiency and saturation capacity of Ce(IV) were increased by 10% and 10 g L-1, respectively. Separation factor of Ce(IV)/Th(IV) was increased from 16 to 27 at 2 mol L-1 H2SO4. Furthermore, P113 presented excellent regenerability. The superiority of P113 was theoretically explored using the density functional theory (DFT) and polarizable continuum model (PCM), and the results indicated that THPO (trihexyl phosphine oxide) had lower extraction phase transfer energy than TOPO (trioctyl phosphine oxide) from aqueous phase to organic phase. The comprehensive evaluation of P113 demonstrated the feasibility employed in the recovery of Ce(IV)-F and the separation of Th(IV) from bastnaesite, which advanced industrial application of the novel extractant, and held significant value for the utilization of resources and environmental protection.

Molecular simulation of the structural formation of mono- and bidisperse polyethylene upon cooling from the melts

Monte Carlo (MC) simulation of the coarse-grained polyethylene (PE) model on the high coordination lattice was employed to investigate the structural formation of mono- and bidisperse PE chains upon stepwise cooling from the melts. The evolution of the ordered structure was analyzed in terms of the fraction of trans state, the length of trans sequence, the orientation correlation function at bond and molecular scale, the intermolecular pair correlation function, and the anisotropic change of chain dimension. Simulation data suggest that the rate of structure formation and the degree of crystallinity were decreased for the bidisperse PE mixture. In general, polymers in the mixture form a less-ordered structure, exhibit slower crystallization rates and have lower melting temperatures. For the monodisperse systems, the shorter chains exhibit an increase of the local bond properties including a fraction of trans conformation, intra- and intermolecular order parameters, but show a decrease in molecular properties such as chain orientation and chain packing. For mixed molecular weight systems, short-chain components are perturbed by the long chains resulting in a lower fraction of trans conformation, less dense structures, and a significant decrease in the degree of the bond orientation. Both short and long polymers can co-crystallize initiated at the same simulation time and finally reach the same magnitude of the chain order parameter.

Effect of repeated heating of coconut, sunflower, and palm oils on their fatty acid profiles, biodiesel properties and performance, combustion, and emission, characteristics of a diesel engine fueled with their biodiesel blends

• WCO biodiesel properties and fatty acid profile depend on the source and heating cycles. • Repeated heating caused reduced unsaturated and increased short-chain compounds. • Repeated heating resulted in increased density, viscosity, and calorific value. • Repeated heating decreased BTE, smoke opacity, and increased HC and NO x . • Coconut-based biodiesels showed better engine performance and emission comparatively. Using cooking oil multiple times is a common practice to reduce the food preparation cost, which causes many health issues, also simply throwing it away will cause environmental pollution. Hence, converting waste cooking oil into biodiesel is a solution to waste management with energy production. This study analyzed the effect of the number of heating cycles of coconut, sunflower, and palm oils on the fatty acid configuration and properties of biodiesel produced from them. A reduction in unsaturated compounds, increase in short-chain components, increase of 0.266%, 0.365%, and 0.347% in density, increase of 5.06%, 12.29%, and 8.83% in kinematic viscosity, increase of 0.266%, 0.365%, and 0.347% in calorific value are observed with five repeated heating of coconut, sunflower, and palm oils, respectively. Performance, combustion, and emission analysis of a diesel engine fueled with B20 blends of biodiesels showed a decrease of 0.27 %, 0.28 %, and 0.52 % in brake thermal efficiency, an increase of 2.44 J/deg, 3.43 J/deg, and 2.74 J/deg in peak heat release rate, an increase of 7 ppm, 65 ppm, and 60 ppm in NO x emission, and decrease of 4.5 %, 2.8 %, and 1 % in smoke opacity with five repeated heating of coconut, sunflower, and palm oils, respectively. Even though the brake thermal efficiency and emissions (except NO x ) were found decreased for all biodiesel blends compared to diesel, coconut-based biodiesels were found to be the best alternative among all the biodiesels with reduced HC, NO x , and smoke as compared to diesel.

Exploring the source, migration and environmental risk of perfluoroalkyl acids and novel alternatives in groundwater beneath fluorochemical industries along the Yangtze River, China

The widely used legacy perfluoroalkyl acids (PFAAs) with serious environmental hazards are gradually restricted and being replaced by novel alternatives. Here, for an efficient control of emerging environmental risks in groundwater, we systematically studied the source apportionment, spatial attenuation, composition change and risk zoning of 12 PFAAs and five novel alternatives within a region of ~200 km2 around a mega fluorochemical industrial park (FIP) along the Yangtze River, and in-depth explored potential association between groundwater and soil pollution as well as influencing factors on contaminant migration and risk distribution in the aquifer. Short-chain PFAAs and novel alternatives together accounted for over 70% in groundwater, revealing their prevalence in replacing legacy perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). Novel alternatives for PFOA were mainly hexafluoropropylene oxide dimer acid (GenX) and hexafluoropropylene oxide trimer acid (HFPO-TA), while those for PFOS were 6:2 chlorinated polyfluorinated ether sulfonic acid (6:2 Cl-PFESA) and 6:2 fluorotelomer sulfonic acid (6:2 FTS). PFAAs (maximum total: 1339 ng/L) and novel alternatives (maximum total: 208 ng/L) in groundwater were mostly derived from the FIP, and exhibited an exponentially decreasing trend with increasing distance. Compared with those in groundwater, more diverse sources of PFAAs and novel alternatives in surface soil were identified. The transport of these chemicals may be retarded by clayed surface soils with high organic matter contents. High aquifer permeability could generally promote the dilution and migration of PFAAs and novel alternatives in groundwater, as well as reduce the differences in their spatial distribution. Shorter-chain components with smaller molecules and higher hydrophilicity exhibited greater migration capacities in the aquifer. In addition, different levels of health risk from PFOS and PFOA were zoned based on drinking groundwater, and high risks tended to be distributed in areas with relatively poor aquifer water yield due to higher pollutant accumulation.

How the oil recovery in deep oil reservoirs is affected by injected gas types: A molecular dynamics simulation study

Through molecular dynamic simulation, an investigation was conducted into the behavioral mechanism of gas injection for the development of deep oil reservoirs, with the response to environment taken as the critical influencing factor in EOR. In this study, medium-shallow reservoir was used for comparative analysis, while two types of reservoir were examined in bulk phase and on mineral surface. It was found that in deep reservoirs, the type of gas made little difference to the oil dissolution in bulk phase. In contrast, there was an evident sequence, CO2 ≈ C3H8 > CH4 ≈ N2, observed during the process of oil detachment from mineral surface. In addition, the reservoir environment mainly affects the dissolution of long-chain components, because short-chain components will quickly reach a fully dissolved state. Our study highlights the effect of gas types on oil displacement on a molecular level, which may help to promote the development of deep oil reservoirs.

Disentangling and Lamellar Thickening of Linear Polymers during Crystallization: Simulation of Bimodal and Unimodal Molecular Weight Distribution Systems.

We have performed coarse-grained molecular dynamics simulations to study the isothermal crystallization of bimodal and unimodal molecular weight distribution (MWD) polymers with equivalent average molecular weight (Mw). By using primitive path analysis, we can monitor the entanglement evolution during the process of crystallization. We have discovered a quantitative correlation between the degree of disentanglement and crystallinity, indicating that chain disentanglement permits the process of crystallization. In addition, the crystalline stem length also displays a linear relation with the degree of disentanglement at different temperatures. Based on the observation in our simulations, we can build a scenario of the whole process of chain disentangling and lamellar thickening on the basis of chain sliding diffusion. Furthermore, we have enough evidence to infer that the temperature dependence of crystalline stem length is basically a result of temperature dependence of chain sliding diffusion. Our observations are also in agreement with Hikosaka's sliding diffusion theory. Compared to the unimodal system, the disentanglement degree of the bimodal system is more delayed than its crystallinity due to the slower chain sliding of the long-chain component; the bimodal system reaches a larger crystalline stem length at all temperatures due to the promotion of higher chain sliding mobility of the short-chain component.

Monte Carlo simulation of molecular and structural properties of mono- and bi-dispersed poly(ethylene oxide) nanofibers

Molecular and structural properties of poly(ethylene oxide), PEO, nanofibers with different diameters and molecular weights were investigated using Monte Carlo simulation of coarse-grained models on high coordination lattice. PEO nanofibers made up of mono- and bi-dispersed chains of CH3-(OCH2CH2)x-OCH3 where x = 13 to 53, with diameter ranged from 7.4 to 16.4 times the radius of gyration of PEO chains, were analyzed. For mono-disperse chains, as a result of increasing molecular weight, the bulk density increases and the molecular size at the surface is decreased more than the nanofibers composed of shorter chain length. There is higher degree of parallel orientation of the chains and bonds at the surface and a broader region over which this bond orientation pertains. For nanofibers with mixed molecular weight, shorter chains tend to segregate at the surface and the density of short chain component is higher in this region. Compared to mono-disperse nanofibers, the properties of longer chains do not significantly change, whereas the orientation of chains and bonds for low molecular weight polymers become more anisotropic orientation in the presence of longer chains.

Enhanced thermal conductivity of multilayered sheets of polyethylene and boron nitride via promoting molecular diffusion between layers

In this work, we alternatively compressed a high density polyethylene/low molecular weight polyethylene (LMWPE)/hexagonal boron nitride (h-BN) composite layer and a low density polyethylene layer together to fabricate thermally conductive bulk products. Compared to our previous work (without the LMWPE component), introducing the short chain component, i.e., LMWPE, into the composite layers further enhanced the h-BN content to 18.3 vol. %, and, thus, more thermally conductive paths could be formed after annealing, resulting in higher thermal conduction performance. Also, the annealed multilayered cuboid in this work exhibited a high thermal conductivity of 1.96 (W/m K), 43% higher than that of our previous study (1.37 W/m K). In contrast with that of the samples with randomly distributed h-BN at the same loading, an approximately 145% enhancement was achieved. The results demonstrate that our method to fabricate the multilayered cuboids has a great opportunity for application in the thermal management field of electric devices.

Characteristics of perfluoroalkyl acids in atmospheric PM10 from the coastal cities of the Bohai and Yellow Seas, Northern China

The concentration distributions, compositional profiles and seasonal variations of 17 perfluoroalkyl acids (PFAAs) in PM10 (particles with aerodynamic diameters < 10 μm) were determined in seven coastal cities of the Bohai and Yellow Seas. The detection rates of perfluorooctanoic acid (PFOA) and short-chain components (perfluoroalkyl carboxylic acids (PFCAs) with ≤7 carbon atoms and perfluoroalkane sulfonic acids (PFSAs) with ≤5 carbon atoms) were much higher than those of other long-chain PFAA species. The annual average concentration of total PFAAs in PM10 ranged from 23.6 pg/m3 to 94.5 pg/m3 for the sampling cities. The monthly mean concentrations of PFAAs in PM10 in some sampling cities reached a peak value in winter, while no significant seasonal differences presented in other cities. High concentrations of PFAAs in the northern cities generally occurred during the local heating period (from November to March). Generally, the dominant components of PFAAs were PFOA and perfluorobutyric acid (PFBA). Some significantly positive correlations (p < 0.01) between the 10 dominant components were revealed in the sampling cities, which implied similar sources and fate behaviors. Based on the simulated 72-hr backward trajectory tracking of air masses, the clustering results demonstrated the sampling cities were affected mainly by the atmospheric transport in sequence from the northwest, the southwest and the open seas, and many transport trajectories of air masses passed by the local fluorine chemical manufacturers in Liaoning, Shandong, Jiangsu, and Hubei Provinces. The estimated average daily intake (ADI) corresponding to the residents in different age groups indicated insignificant contributions to PFOA and perfluorooctane sulfonate (PFOS) exposures by inhalation of PM10 compared to ingestion by daily diet, while the higher ADI of PFOA than the reported levels for adults should be a concern. The calculated hazard ratios (HR) exhibited low noncancer risks by inhalation exposure to PFOA and PFOS in PM10.

Effects of Amphipathic Polypeptides on Membrane Organization Inferred from Studies Using Bicellar Lipid Mixtures

SP-B63-78, a lung surfactant protein fragment, and magainin 2, an antimicrobial peptide, are amphipathic peptides with the same overall charge but different biological functions. Deuterium nuclear magnetic resonance has been used to compare the interactions of these peptides with dispersions of 1,2-dimyristoyl- sn-glycero-3-phophocholine (DMPC)/1,2-dihexanoyl- sn-glycero-3-phophocholine (DHPC) (4:1) and DMPC/1,2-dimyristoyl- sn-glycero-3-phopho-(1'-rac-glycerol) (DMPG)/DHPC (3:1:1), two mixtures of long-chain and short-chain lipids that display bicellar behavior. This study exploited the sensitivity of a bicellar system structural organization to factors that modify partitioning of their lipid components between different environments. In small bicelle particles formed at low temperatures, short-chain components preferentially occupy curved rim environments around bilayer disks of the long-chain components. Changes in chain order and lipid mixing, on heating, can drive transitions to more extended assemblies including a magnetically orientable phase at intermediate temperature. In this work, neither peptide had a substantial effect on the behavior of the zwitterionic DMPC/DHPC mixture. For bicellar mixtures containing the anionic lipid DMPG, the peptide SP-B63-78 lowered the temperature at which magnetically orientable particles coalesced into more extended lamellar structures. SP-B63-78 did not promote partitioning of the zwitterionic and anionic long-chain lipid components into different environments. Magainin 2, on the other hand, was found to promote separation of the anionic lipid, DMPG, and the zwitterionic lipid, DMPC, into different environments for temperatures above 34 °C. The contrast between the effects of these two peptides on the lipid mixtures studied appears to be consistent with their functional roles in biological systems.

Characteristics and compound-specific carbon isotope compositions of sedimentary lipids in high arsenic aquifers in the Hetao basin, Inner Mongolia

Organic matter, as an electron donor, plays a vital role in As mobilization mediated by microorganisms during reductive dissolution of Fe/Mn oxides in shallow aquifers. However, the specific types and sources of organic matter involved in biogeochemical processes accelerating As mobilization are still controversial. Both sediment and groundwater samples were collected at different depths from aquifers of the Hetao Basin, a typical inland basin hosting high As groundwater. Sedimentary lipids and their compound-specific carbon isotope ratios were analyzed to evaluate characteristics and sources of organic matter. Results show that sedimentary As were well correlated with Fe and Mn oxides, suggesting that As exist as Fe/Mn oxide bound forms. Groundwater As far exceeded the drinking water guide value of 10 μg/L. Moreover, As concentrations in shallow groundwater were relatively higher. Lipids in clay were mainly originated from terrestrial higher plants, while that in fine sand samples were derived from terrestrial higher plants, microorganism and petroleum. Shallow fine sand samples were also characterized by evident in-situ biodegradation. Compound-specific carbon isotope compositions of sedimentary lipids showed that short-chain n-alkanes and n-alkanoic acids had more positive δ13C values compared to long-chain compounds, especially in shallow fine sand samples. δ13CTOC were also low in shallow fine sand samples. These results jointly indicate that these lipids in shallow fine sand samples acted as carbon source for indigenous microorganism and the short-chain components were particularly more vulnerable to biodegradation, which may contribute to high As concentrations in shallow groundwater. The new findings provide the first evidence that short chain length n-alkyl compounds afforded a source of potential electron donors for microbially mediated As mobilization process in the shallow aquifers.

Tree swallow chicks construct long-chain omega-3 fatty acids from building blocks

Imagine cramming an entire life's growth into a single month; that is exactly the challenge faced by some newly hatched chicks. ‘Tree swallows nearly double in mass every other day when they are between 5 and 10 days old’, says Cornelia Twining from Cornell University, USA. And this rapid mass gain places an immense burden on the parents, which must provide their offspring with nutritious food to satisfy their voracious appetites. Twining adds that highly unsaturated omega-3 fatty acids (long-chain omega-3 fatty acids), such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), are vital for the youngster's health and growth. However, only a few birds, such as chickens, are capable of producing these key fatty acids from shorter components; other species must obtain them through their diet, and aquatic insects, such as mayflies and midges, which dine on long-chain omega-3-rich algae, are the best source. As tree swallows benefit from a mix of terrestrial and aquatic insects in their diet, Twining and co-authors Tom Brenna, David Winkler, Peter Lawrence and Alex Flecker wondered whether the youngsters may be able to generate the essential long-chain omega-3 fatty acids from shorter components (alpha-linolenic acid – ALA) or whether they depend solely on the aquatic insects in their diet for their supply of long-chain omega-3 fatty acids.‘Tree swallows were a great species to work with … because they are very tolerant of researchers studying them during their breeding season’, says Twining, who recalls that the parents were content to keep feeding their young even when the researchers slipped the youngsters additional meals of olive oil laced with a labelled version of the ALA component, in order to trace whether the chicks were able to convert it into the longer chain fatty acids. ‘Getting them to gulp down from a syringe takes a little practice, but is not a problem, so long as they are gaping for food’, says Twining, although the youngsters’ table manners were less than impeccable. ‘Chicks are pretty messy eaters’, she recalls, which made it difficult to be sure exactly how much of the special olive oil the chicks had consumed.Forty-eight hours later, Twining extracted fatty acids from the chicks and analysed them with Lawrence and Brenna. Impressively, the chicks could convert the short-chain component into the essential long-chain omega-3 fatty acids, but could they satisfy all of their long-chain omega-3 demands from the short-chain components in their diet alone?Twining needed to know how much ALA various insects could provide the chicks, so she trapped insects ranging from aquatic mayflies and dragonflies to terrestrial beetles, flies, moths and butterflies to find out how much of the short fatty acid they contained. However, after she measured the amount of ALA in the insects’ bodies with Lawrence and Brenna, it was clear that the chicks were not able to produce sufficient long-chain omega-3 fatty acids from the short-chain fatty acid components supplied by their diet.‘We suggest that omega-3 HUFA [long-chain omega-3 fatty acids] are likely to be “ecologically essential” nutrients for tree swallow chicks’, says Twining, who is now keen to find out whether other wild species are capable of producing the essential long-chain omega-3 fatty acids from components in their diet. ‘I hope to understand what their physiological nutritional needs are and how likely they are to suffer nutritional mismatches if they cannot get what they need in their diet’, she says.

Sources of organic matter in the surface sediments from Lake Sihailongwan Maar and Lake Zhanjiang Maar (Lake Huguangyan Maar) in China

Maar lakes are closed lakes that have a well-documented history of changes in organic matter (OM) production. The surface sediments from 2 typical maar lakes in China were analyzed for total organic carbon (TOC), total nitrogen (TN), δ13Corg, δ15Ntotal, aliphatic hydrocarbons (AHs), fatty acids (FAs) and alkanols. The FAs and alkanols were fractionated into two sub-fractions (free and bound) to investigate their sources. A higher TOC content was observed in the surface sediment from Lake Sihailongwan Maar than that from Lake Zhanjiang Maar. The molecular compositions of the n-alkanes, n-alkanols and FAs extracted from the surface sediments reveal different responses to environmental changes. The fatty acid distributions are dominated by short-chain components from algal and bacterial origins. However, the n-alkane and free n-alkanol distributions in the surface sediment from Lake Sihailongwan Maar are dominated by long-chain terrestrial source inputs, indicating that the secondary components of the post-depositional microbial activity are important for the FAs in the sediment from Lake Sihailongwan Maar. The aquatic FAs derived from algae and anaerobic bacteria are major components of sedimentary OM in all of the studied samples.

A comparison of the distribution and sources of organic matter in surface sediments collected from northwestern and southwestern plateau lakes in China

&lt;p&gt;Surface lacustrine sediments from six plateau lakes in China were analysed for total organic carbon (TOC), total nitrogen, δ&lt;sup&gt;13&lt;/sup&gt;C&lt;sub&gt;org&lt;/sub&gt;, δ&lt;sup&gt;15&lt;/sup&gt;N&lt;sub&gt;total&lt;/sub&gt;, aliphatic hydrocarbons, fatty acids (FAs), and alkanols. The FAs and alkanols were fractionated into free and bound subfractions to facilitate investigation of their sources. Higher average TOC levels were observed in sediments from southwestern plateau lakes than in those from northwestern plateau lakes. The sediments from the southwestern plateau lakes may have been contaminated with petroleum hydrocarbons from anthropogenic activities. The molecular compositions of n-alkanes, n-alkanols, and FAs extracted from the lacustrine sediments showed different responses to environmental changes. Most of the n-alkanol and FA distributions were dominated by short-chain components originating from algae and bacteria. However, the presence of long-chain n-alkanes indicate the presence of predominantly terrestrial organic matter (OM) in the sediment samples from the northwestern plateau lakes in China, suggesting that secondary components derived from post-depositional microbial activity were key contributors to the n-alkanols and FAs. Aquatic FAs derived from algae and anaerobic bacteria were a major component of the sedimentary OM and accounted for 65.1-90.2% of the total lipid concentrations.&lt;/p&gt;

Development of cardanol-bonded cellulose thermoplastics: high productivity achieved in two-step heterogeneous process

We developed a heterogeneous process with low energy consumption to synthesize novel high-strength and heat-resistant cellulose-based bioplastics: cellulose esters bonded with a short chain component (acetic acid) and a long one (3-pentadecylphenoxy acetic acid; PAA), which is a derivative of cardanol, extracted from cashew nut shells. Although we recently showed that PAA-bonded cellulose acetates (cardanol-bonded cellulose resins) exhibit highly practical properties for durable products, they were synthesized in a homogeneous process, which requires large quantities of poor solvents to isolate the resins. In the developed two-step heterogeneous process, the cardanol-bonded cellulose resins are produced without poor solvents. In the first step, cellulose is esterified with limited amounts of the long and short chain components using a selected reaction solvent and catalyst. The resultant intermediate products are adequately swollen in the solvent then efficiently recovered by filtration. In the second step, the short chain component is additionally bonded to attain good thermoplasticity of the final products, which are readily recovered only by distilling a solvent and the remaining short chain component. The solvent usage was reduced by approximately 90 % compared with a homogeneous process, which leads to a large reduction in energy. The produced cardanol-bonded cellulose resins exhibited higher thermoplasticity, elastic modulus, water resistivity, and close heat resistivity compared to that of a homogeneous process. Furthermore, the mechanical and thermal characteristics of the resins were greatly improved by adding a specific polyester, polybutylene succinate adipate, and glass fiber, reaching high-level target properties for durable products.

The effect of dynamic tube dilation on chain stretch in nonlinear polymer melt rheology

The pressures exerted by a polymer chain on the walls of an anisotropic confinement are anisotropic (Doi and Edwards [10]). At deformation rates larger than the inverse Rouse time of the polymer chain, chains are stretched and their confining tubes become increasingly anisotropic. In a tube model with variable tube diameter, this leads to an interchain tube pressure term in the lateral direction of the tube (Marrucci and Ianniruberto [15]), which limits chain stretch. Here we assume that chain stretch is balanced by two restoring tensions with weights of 1/3 in the longitudinal direction of the tube, due to a linear entropic spring force, and 2/3 in the lateral direction, due to a nonlinear interchain tube pressure, both of which are characterized by the Rouse stretch relaxation time τ R . This approach is in quantitative agreement with the time-dependent and steady-state elongational viscosity of two monodisperse polystyrene melts with molar masses of 390,000 and 200,000 kg/mol as investigated by Bach et al. [2] and Hassager [12]. In bidisperse polymer blends, the interchain pressure is reduced in accordance with dynamic dilation of the tube. Implementation of the dilation effect into the evolution equation of the stretch leads to a quantitative description of the elongational behavior of bidisperse polystyrene blends consisting of a long and a short chain component as investigated by Nielsen et al. [22]. Due to the effect of chain ends, dynamic tube dilation is also of importance for monodisperse polymer melts with low molar masses having few entanglements, as demonstrated for two polystyrene melts with molar masses of M w = 102,800 and 51,700 g/mol. If dynamic tube dilation is taken into account, quantitative agreement between highly nonlinear viscoelastic experiments and predictions can be obtained based exclusively on the linear-viscoelastic characterization of polymer melts.

Molecular simulation of adsorption and separation of mixtures of short linear alkanes in pillared layered materials at ambient temperature

Grand canonical Monte Carlo and configurational-bias Monte Carlo techniques are carried out to simulate the adsorption of ternary and quaternary mixtures of short linear alkanes, involving methane, ethane, propane, and n-butane, in pillared layered materials at ambient temperature, T = 300 K . In the simulation, a pillared layered pore is modeled by a uniform distribution of pillars between two layered walls built by making two separate talc lamellas parallel each other with a given size of interlayer distance. The interaction between fluid molecules and two layered walls is measured by storing potentials calculated in advance at a series of grid points. The interaction between fluid molecules and pillars is also calculated by a site-to-site method. The potential model proposed in this work is proved to be effective because of the simulation result being good agreement with the experimental data for the adsorption of nitrogen at 77 K. Then, the adsorption isotherms of mixtures of short linear alkanes in pillared layered pores with three different porosities ψ = 0.98 , 0.93 and 0.85, and three pore widths H = 1.02 , 1.70 and 2.38 nm at 300 K are obtained by taking advantage of the model. The simulation results tell us that the longer chain component is preferentially adsorbed at low pressures, and its adsorption increases and then decreases as the pressure increases while the shorter chain component is still adsorbed at high pressures. Moreover, the sorption selectivity of pillared layered materials for the longest chain component in alkane mixtures increases as the mole fraction of methane in the gas phase increases. The selectivity of pillared layered materials for the longest chain component in alkane mixtures also increases as the pore width decreases and the porosity increases.

Adsorption and Separation of Ternary and Quaternary Mixtures of Short Linear Alkanes in Zeolites by Molecular Simulation

The adsorption equilibria of ternary and quaternary mixtures of short linear alkanes, involving methane, ethane, propane, and n-butane, were simulated by using the configurational-bias Monte Carlo technique in grand canonical ensemble in MFI zeolite. The simulation results are in good agreement with the experimental data. The adsorption isotherms in MFI zeolite show that the longer chain component is preferentially adsorbed at low pressures. Its adsorption increases and then decreases as the pressure increases. But the shorter chain component is adsorbed at higher pressures and its adsorption increases as the pressure increases. The selectivity of ISV and MFI is much higher than that of MOR. The selectivity increases rapidly as the mole fraction of methane in the gas phase increases, but the change of selectivity of MOR is not obvious in an methane−ethane−propane mixture. The adsorbed amount in mixtures is in the order of ISV > MFI > MOR.