Increase In Molecular Weight Research Articles

Study on preparation and controlled release in vitro of bergenin-amino polylactic acid polymer

The efficacy of traditional tablets, drop pills and soft capsules of bergenin is far lower than expected. Therefore, bergenin was modified in this paper to connect with amino polylactic acid, a kind of biodegradable material, for chemical immobilization. The bergenin-amino PLA thus obtained was controllable with small molecular weight and excellent thermal stability. Its release in vitro could be extended with the increase in molecular weight. According to tests of biological compatibility and anti-tumor in vitro, bergenin-amino PLA at a proportion of 1 to 100 was characterized by better biological compatibility and lower cytotoxicity than control group at a concentration of 0.4 μ g/m L. The chemical immobilization of bergenin not only provides patients with an excellent way of drug administration but lays a good foundation for sustained drug release.

Structural Changes of Oak Wood Main Components Caused by Thermal Modification.

Thermal modification of wood causes chemical changes that significantly affect the physical, mechanical and biological properties of wood; thus, it is essential to investigate these changes for better utilization of products. Fourier transform infrared spectroscopy and size exclusion chromatography were used for evaluation of chemical changes at thermal treatment of oak wood. Thermal modification was applied according to Thermowood process at the temperatures of 160, 180 and 210 °C, respectively. The results showed that hemicelluloses are less thermally stable than cellulose. Chains of polysaccharides split to shorter ones leading to a decrease of the degree of polymerization and an increase of polydispersity. At the highest temperature of the treatment (210 °C), also crosslinking reactions take place. At lower temperatures degradation reactions of lignin predominate, higher temperatures cause mainly condensation reactions and a molecular weight increase. Chemical changes in main components of thermally modified wood mainly affect its mechanical properties, which should be considered into account especially when designing various timber constructions.

Dual catalytic performance of arene‐ruthenium amine complexes for norbornene ring‐opening metathesis and methyl methacrylate atom‐transfer radical polymerizations

Arene ruthenium(II) complexes bearing the cyclic amines RuCl2(η6‐p‐cymene)(pyrrolidine)] (1), [RuCl2(η6‐p‐cymene)(piperidine)] (2), and [RuCl2(η6‐p‐cymene)(peridroazepine)] (3) were successfully synthesized. Complexes 1–3 were fully characterized by means of Fourier transform infrared, UV–visible, and NMR spectroscopy, elemental analysis, cyclic voltammetry, computational methods, and one of the complexes was further studied by single crystal X‐ray crystallography. These compounds were evaluated as catalytic precursors for ring‐opening metathesis polymerization (ROMP) of norbornene (NBE) and atom‐transfer radical polymerization (ATRP) of methyl methacrylate (MMA). NBE polymerization via ROMP was evaluated using complexes 1–3 as precatalysts in the presence of ethyl diazoacetate (EDA) under different [NBE]/[EDA]/[Ru] ratios, temperatures (25 and 50°C), and reaction times (5–60 min). The highest yields of polyNBE were obtained with [NBE]/[EDA]/[Ru] = 5000/28/1 for 60 min at 50°C. MMA polymerization via ATRP was conducted using 1–3 as catalysts in the presence of ethyl‐α‐bromoisobutyrate (EBiB) as initiator. The catalytic tests were evaluated as a function of the reaction time using the initial molar ratio of [MMA]/[EBiB]/[Ru] = 1000/2/1 at 95°C. The increase in molecular weight as function of time indicates that complexes 1–3 were able to mediate the MMA polymerization with an acceptable rate and some level of control. Differences in the rate of polymerization were observed in the order 3 > 2 > 1 for the ROMP and ATRP.

Multi-attribute PAT for UF/DF of Proteins-Monitoring Concentration, particle sizes, and Buffer Exchange.

Ultrafiltration/diafiltration (UF/DF) plays an important role in the manufacturing of biopharmaceuticals. Monitoring critical process parameters and quality attributes by process analytical technology (PAT) during those steps can facilitate process development and assure consistent quality in production processes. In this study, a lab-scale cross-flow filtration (CFF) device was equipped with a variable pathlength (VP) ultraviolet and visible (UV/Vis) spectrometer, a light scattering photometer, and a liquid density sensor (microLDS). Based on the measured signals, the protein concentration, buffer exchange, apparent molecular weight, and hydrodynamic radius were monitored. The setup was tested in three case studies. First, lysozyme was used in an UF/DF run to show the comparability of on-line and off-line measurements. The corresponding correlation coefficients exceeded 0.97. Next, urea-induced changes in protein size of glucose oxidase (GOx) were monitored during two DF steps. Here, correlation coefficients were ≥ 0.92 for static light scattering (SLS) and dynamic light scattering (DLS). The correlation coefficient for the protein concentration was 0.82, possibly due to time-dependent protein precipitation. Finally, a case study was conducted with a monoclonal antibody (mAb) to show the full potential of this setup. Again, off-line and on-line measurements were in good agreement with all correlation coefficients exceeding 0.92. The protein concentration could be monitored in-line in a large range from 3 to 120 g L- 1. A buffer-dependent increase in apparent molecular weight of the mAb was observed during DF, providing interesting supplemental information for process development and stability assessment. In summary, the developed setup provides a powerful testing system for evaluating different UF/DF processes and may be a good starting point to develop process control strategies. Graphical Abstract Piping and instrumentation diagram of the experimental setup and data generated by the different sensors. A VP UV/Vis spectrometer (FlowVPE, yellow) measures the protein concentration. From the data of the light scattering photometer (Zetasizer, green) in the on-line measurement loop, the apparant molecular weight and z-average are calculated. The density sensor (microLDS) measures density and viscosity of the fluid in the on-line loop.

Kinetic study on the synergistic effect between molecular weight and phosphorus content of flame retardant copolyesters in solid‐state polymerization

Abstract2‐Carboxyethyl(phenyl phosphinic) acid has been proved to modify flame retardant properties of poly(ethylene terephthalate) (PET) through copolymerization; however, there is no industrial technological breakthroughs in polyester industrial yarns which requires high strength and modulus, because it is related to the coordinated control of molecular weight and flame retardancy. In this work, the influence of solid‐state polymerization reaction kinetics and parameters on flame retardancy retention have been investigated, based on the prepared precursors optimized at 6,000 ppm phosphorus content and 0.64 dL/g intrinsic viscosity (I.V). Results showed that the copolyester polydispersity index increase was significant compared to PET with molecular weight increase. The I.V of optimized precursor could be increased to 1.31 dL/g at 220°C in 20 hr, but at higher phosphorus content loses up to 7%. Flame retardant component deteriorates with increasing reaction rate and temperature as a result of severe side reactions. Optimized precursor at the optimum temperature (210°C) reacted for 20 hr, copolyester with the phosphorus content of 5,910 ppm and the I.V of 1.12 dL/g (( was about 3.5 × 104 g/mol) was prepared. The coordination between high molecular weight and flame retardant performance was realized.

Functionalization-Induced Self-Assembly of Polystyrene/Kaolinite in Situ Nanocomposites into Giant Vesicles.

We report a facile functionalization strategy for fabrication of giant, inorganic-polymer hybrid vesicles by controlled aminosilyl/vinylsilyl functionalization (AS/VS) of the aluminol layer in kaolinite (Kaol) by intercalation and subsequent polymerization of styrene with the in situ polystyrene clay nanocomposite (PCN), followed by self-assembly in solvents. The synergistic effect of the AS/VS ratio on functionalization-assisted intercalation of Kaol was established in 1:3AS/VS-Kaol by the greater extent of formation of higher interlayer spacing corresponding to 1.12 nm compared to 1:1AS/VS-Kaol. As the AS/VS ratio was increased, the PCN synthesized showed an increase in molecular weight attributed to higher vinyl functionalization of Kaol. The PCN, 1:3AS/VS-Kaol/PS, showed self-assembly in tetrahydrofuran at 2.5 mg mL-1 into giant vesicles of 2-6 μm diameter with a wall thickness of 300-400 nm. This result is attributed to the functionalization-induced molecular mass-directed bilayer assembly of the delaminated, Janus-type, modified Kaol in a polar aprotic solvent by end-to-end hydrogen bonding involving terminal -OH groups along the wall and -NH2 groups laterally and further stabilized by the π-π interactions of the phenyl moiety along the periphery. Rhodamine-loaded vesicles showed a controlled release in buffer solutions of pH 7.0 and 9.0, attributed to the amino group-assisted pore formation. In a buffer solution of pH 4.0, rapid release of the dye was observed because of the collapse of the vesicle directed by protonation of the amino group. This study forms the first report on a novel method for the synthesis of rigid vesicles by functionalization-induced self-assembly of Kaol-based in situ PCN for possible applications in the cost-effective controlled delivery of drugs or cosmetics for topical applications.

Relaxation and physicomechanical characteristics of polyethylenes with different molecular weights

Objectives. Determination of the influence of molecular weight on the modulus of elasticity, yield, strength, and retardation processes in polyethylene. Methods. We used vane samples (thickness: 4 mm; length: 100 mm; width.: 10 mm) made by injection molding at p = 60 MPa, T = 210 °C, τ = 15 s from the following polyethylenes: HDPE 27773 (Stavrolen, Lukoil, Russia); BorSafe HE3490-IM (Borealis, Austria; black); CRP 100 Hostalen (Basell Polyolefins, Netherlands; black); Stavrolen PE4PP-25B (Stavrolen, Lukoil, Russia; black). The samples were in accordance with the defined standards for the AL 7000 LA-5 tensile testing machine. The study of relaxation characteristics was carried out in two modes: relaxation and retardation. Results. We obtained stress-strain diagrams at various temperatures under isothermal conditions (T = const) and determined the influence of polyethylene molecular weights on the modulus of elasticity, yield, and strength of polyethylenes. We have shown that under isothermal conditions, when the stress equals the yield strength, the removal of the external action results in a two-stage response. The first stage is the stress relaxation. The second stage characterizes the elastic features of the studied materials under the external action e = const. Conclusions. We have established that temperature increase affects the physicomechanical characteristics of polyethylenes differently, depending on their molecular weights. The experiments have shown that when the stress exceeds the yield strength, at constant deformation, there is a complex response of the polyethylenes to external action. This response is characterized by two stress stages throughout the course of time. The first stage is characterized by asymptotic decrease in stress down to a constant value; the second stage is characterized by constant stress throughout the course of time. We have determined relaxation times for the relaxation stage (stage I) and calculated activation energy. We have also established that the activation energy depends on molecular weights of the polyethylenes. It has been shown that an increase in polyethylene molecular weight leads to a decrease in relaxation time and activation energy.

Unraveling the Effect of PEG Chain Length on the Physical Properties and Toxicant Removal Capacities of Cross-Linked Network Synthesized by Thiol-Norbornene Photoclick Chemistry.

With the aim to develop chemical adsorbents that are inherently nontoxic to living beings and the environment, a gel system based on thiol–norbornene photoclick chemistry was developed. Norbornene was strategically functionalized with different poly(ethylene glycol) (PEG) chains to produce PEG-functionalized macromonomers. The influence of incorporating PEG in the cross-linked network was evaluated on the basis of its physical properties and dye-removing efficiency from aqueous solutions. The excellent swelling ability of the gels in organic solvents was found to improve with the PEG chain length. The rheological measurements of the as-synthesized materials also exhibited the presence of elasticity in the network, and a decrease in storage and loss moduli was observed with an increase in PEG molecular weight. The materials possess excellent thermal stability, which enhanced with an increase in PEG chain length, as revealed from thermogravimetric analysis (TGA). Differential scanning calorimetry (DSC) studies revealed the tendency of higher-molecular-weight PEG to form a crystalline phase in the network. Kinetic studies of dye removal from aqueous solutions by the as-prepared cross-linked networks indicate that the dye removal proceeds via pseudo-second-order kinetics. The study of adsorption isotherm of the removal process indicates that the adsorption follows the Langmuir isotherm model. In this present work, we have thoroughly evaluated the influence of PEG chain length on several physical properties and toxic cationic dye removal efficiencies of thiol–norbornene photo-cross-linked networks.

Study on the surface activity and aggregation behavior of a polyether surfactant for acidification

Four kinds of biological phenolamine resin block ethers (BPPC) surfactants with different molecular weights were synthesized from biological phenol, formaldehyde and polyvinyl polyamines. The structure of BPPC was characterized by Ft-ir and H NMR. The surface properties of BPPC polyether surfactant and the change curve of surface tension with concentration in aqueous solution at different temperature were studied by surface tension method. The results showed that the critical micelle concentration (cmc) of BPPC and the γcmc increased with the increase of EO content. With the increase of molecular weight, number of branched chains and length of branched chains, cmc and γcmc decreased. The thermodynamic calculation results show that BPPC shows enthalpy/entropy compensation during micellization in aqueous solution. The compensation temperature T was all (300±2) K, and with the increase of molecular weight, number of branched chains and length of branched chains, the stability of BPPC formed in aqueous solution was enhanced.

Synthesis and application of urethane-containing azo disperse dyes on polyamide fabrics

A series of new azo disperse dyes containing the urethane group were synthesized through the reaction between the hydroxyl group in coupling component of disperse dyes and p-toluene isocyanate. The structures of the new dyes were fully confirmed by 1H NMR, 13C NMR, FT-IR, MS and Elemental analysis. Their characteristics for the visible-light absorption and color fastness on polyamide fibers were respectively measured and compared with those of the original dye. It was found that the new dyes exhibited hypsochromic effect, and had the nearly unchanged absorption half band and higher molar extinction coefficients, the fastness properties has been greatly improved, especially for the washing and sublimation fastness. The new dyes 2d and 2e containing double urethane groups possessed excellent fastness properties on polyamide fabrics. These two dyes for all the fastness tested, including water fastness, sublimation fastness, rubbing fastness and light fastness, had reached 4–5 and 5 rates. It was very clear that the introduction of urethane group and the increase of molecular weight can effectively improve the fastness of disperse dyes for the polyamide fibers.

Toward the viscosity reducing of cement paste: Optimization of the molecular weight of polycarboxylate superplasticizers

The influence of polycarboxylate superplasticizers (PCEs) on rheology was investigated for viscosity reducing of cement pastes. Five types of PCEs of varied molecular weight were employed. For pastes with same w/c and consistent spread value, yield stress was almost the same, while residual viscosity decreased with the increase of molecular weight of PCE. It was suggested that it was probably the “bridging effect” causing more adsorption amount required to achieve similar yield stress for PCE of larger molecular weight. The large adsorption layer thickness was beneficial for improving packing density, which enlarged the average particle separating distance, and finally resulted in a significant decrease in residual viscosity of cement pastes. Considering that packing density improvement was pronounced for viscosity reducing of cement paste, development of PCE with high surface coverage of the long side chain should be the necessary and sufficient condition for the lowering of apparent viscosity of cement paste.

Technology and Physico-chemical Properties of Gelatin from Atlantic Cod Skin

In this work, the technology of fish gelatin from the skin of Atlantic cod from the Barents Sea was developed. The influence of enzyme type, extraction time, and pH of extraction on properties of fish gelatin was studied. The usage of proteolytic enzymes increases the yield of gelatin in comparison with acidic treatment, but the molecular weight of gelatin and viscosity of its solution decrease. The results observed related to the cleavage of peptide bonds of collagen during the enzymolysis process. The increase the time of extraction leads to an increase in molecular weight and quality of gelatin obtained. It was shown that gelatin obtained can be successfully used in the production of functional food products based on fish raw materials. The results obtained are of great importance for the fish-processing industry. They allow transforming existing technologies into non-waste processes and thereby enhance the effectiveness of enterprises and create better environmental conditions.

Early transition, relaminarization and drag reduction in the flow of polymer solutions through microtubes

Experiments are performed to investigate the onset of early transition and drag reduction in the flow of polymer (polyacrylamide and polyethylene oxide) solutions through rigid microtubes of diameters in the range 0.49–2.84 mm. We measure friction factor variation with Reynolds number for varying polymer concentrations and tube diameters, and the Reynolds number, , at which the experimental data deviate from the laminar value represents the onset of transition. Crucially, owing to the high shear rates encountered in our experiments, we show that it is important to account for shear thinning of the fluid in the theoretical estimation of the friction factor in the laminar regime. We accomplish this using a Carreau model, and show that the use of laminar friction factor calculated without shear thinning leads to an erroneous overestimation of . The obtained from friction factor data in the present study is in good agreement with that inferred using micro particle image velocimetry analysis in Chandra et al. (J. Fluid Mech., vol. 844, 2018, pp. 1052–1083). For smaller concentrations of the added polymer, there is a marginal delay in the onset of turbulence, but as the concentration is increased further, the transition Reynolds number decreases much below , the usual value at which transition occurs in Newtonian pipe flows. Thus, the present study further corroborates the phenomenon of early transition leading to an ‘elasto-inertial’ turbulent state in the flow of polymer solutions. For concentrations such that there is a delay in transition, if is maintained above the for Newtonian fluids, the flow is transitional or turbulent in the absence of polymers. At such a fixed , if the concentration of the polymer is increased gradually, the friction factor decreases and the flow relaminarizes. With further increase in polymer concentration, the flow undergoes a transition due to elasto-inertial instability. The effect of addition of small amounts of polymer on turbulent drag reduction in the flow of water through microtubes is also investigated. Increase in polymer concentration, molecular weight and decrease in tube diameter causes an increase in drag reduction. The friction factor data for different polymer concentrations, molecular weights, tube diameters and , when plotted with , show a reasonable collapse, where is the Weissenberg number defined as the product of the longest relaxation time of the polymer solution and the average shear rate in the tube and is the ratio of solvent to total solution viscosity. Interestingly, the onset of the maximum drag reduction asymptote, for experiments using varying tube diameters and polymer concentrations, appears to occur at .

The crystallization behavior of poly(l-lactide)/poly(d-lactide) blends: effect of stirring time during solution mixing

Blending of poly(l-lactide) and poly(d-lactide) (PLLA, PDLA) results in the formation of poly(lactide) stereocomplex crystallites (SC). For the preparation method, numerous reports employed solution mixing and stirring to receive a product with uniform performance. However, the effect of stirring time during solution mixing on the subsequent crystallization behavior did not clear yet, and which is important for solution crystallization, casting and spinning. In this paper, linear PLLA and PDLA with various molecular weights were synthesized. The PLLA and PDLA solutions were mixed together and stirred for different times before casting. Results revealed that the structures of PLA SC and homochiral crystallites (HC) did not vary with change in the stirring time. More amount of content of SC with uniform structure and less amount of content of HC were produced in the specimens stirred for longer time. When the specimens crystallized either from the melt or from the melt-quenching, less amount of content of crystallites (total crystallinity of SC and HC) was produced and the melting temperature of SC and HC depressed in the specimens that were stirred for longer time. With the increase in molecular weights, the effect of stirring time on the crystallization behaviors declined. This investigation provides a route to tailor the crystallization behavior of PLLA/PDLA specimens.

One-Step Photocontrolled Polymerization-Induced Self-Assembly (Photo-PISA) by Using In Situ Bromine-Iodine Transformation Reversible-Deactivation Radical Polymerization.

Polymerization-induced self-assembly (PISA) has become an effective strategy to synthesize high solid content polymeric nanoparticles with various morphologies in situ. In this work, one-step PISA was achieved by in situ photocontrolled bromine-iodine transformation reversible-deactivation radical polymerization (hereinafter referred to as Photo-BIT-RDRP). The water-soluble macroinitiator precursor α-bromophenylacetate polyethylene glycol monomethyl ether ester (mPEG1k-BPA) was synthesized in advance, and then the polymer nanomicelles (mPEG1k-b-PBnMA and mPEG1k-b-PHPMA, where BnMA means benzyl methacrylate and HPMA is hydroxypropyl methacrylate) were successfully formed from a PISA process of hydrophobic monomer of BnMA or HPMA under irradiation with blue LED light at room temperature. In addition, the typical living features of the photocontrolled PISA process were confirmed by the linear increase of molecular weights of the resultant amphiphilic block copolymers with monomer conversions and narrow molecular weight distributions (Mw/Mn < 1.20). Importantly, the photocontrolled PISA process is realized by only one-step method by using in situ photo-BIT-RDRP, which avoids the use of transition metal catalysts in the traditional ATRP system, and simplifies the synthesis steps of nanomicelles. This strategy provides a promising pathway to solve the problem of active chain end (C-I) functionality loss in two-step polymerization of BIT-RDRP.

Chemical and Spectroscopic Characteristics of Anthrosol (Amazonian Dark Earth) and Surrounding Soil from the Brazilian Amazon Forest: Evaluation of Mineral and Organic Matter Content by Depth

The chemical and spectroscopic characteristics of soil organic matter (SOM) isolated from Amazonian dark earth (ADE) and surrounding soil (SR) were evaluated according to the soil depth. The results showed opposite trends for the soils. While ADE featured SOM with a greater aromatic condensation degree and greater hydrophobicity in the top layer, the SR showed more aliphatic and polar SOM. The SOM arrangement from ADE was less hydrophobic, aromatic, and more polar in depth. In contrast, the SOM from SR showed an increase in molecular weight and hydrophobicity. Besides the aromatic protection in the SOM from ADE, there was organo-mineral protection through binding to soil minerals. This suggested that the SOM from ADE was protected by its hydrophobicity and interaction with minerals compared with that from the SR, thereby showing that the combination of both characteristics is important to create new technologies for soil carbon storage.

High impact polytriazole resins for advanced composites

ABSTRACT Three azido-terminated poly(ethylene glycol) macromonomers (ATPEGs) were synthesized from poly(ethylene glycol)s (PEGs) and characterized. The extended polytriazole (EPTA) resins were prepared from the macromonomers, azide and alkyne monomers. Toughening effect of PEGs on polytriazole resins was analyzed by means of mechanical, thermal and electronic microscope characterization. The results show that molecular weight and content of ATPEGs have great influence on the thermal and mechanical properties of cured EPTA resins. The impact strength of cured EPTA resins increases with the increase of the amount and molecular weight of ATPEGs. The flexural strength and heat resistance of cured EPTA resins decrease with the increase of addition amount and molecular weight of ATPEGs. High impact EPTA resins were obtained.

Structural proteins of plasmolemma of the jejunum absorbing enterocytes of cattle fetus in early fetal period

The data on the concentration of structural proteins of plasmolemma of the absorption enterocytes of the cattle fetus in the early fetal period are presented. Changes in the protein composition of the apical and basolateral membranes of enterocytes are manifested, characterized not only by changes in their ratio within different cell domains, but also by the dynamic redistribution of the number of different fractions of polypeptides between the poles of these cells. Analysis of the results of electrophoresis of apical membranes of the cattle fetus enterocytes in the early fetal period indicates a decrease in the content of low molecular weight protein fractions and an increase in high molecular weight. In the apical membranes of enterocytes of two-month-old cattle fetus, 25 protein fractions with a molecular weight of 9.6 to 205 kDa were detected. In the basolateral membranes revealed 23 protein fractions with a molecular weight of 9.6 to 120 kDa. High molecular weight fractions of polypeptides with molecular weights of 250 kDa and 300 kDa appear from the age of three months of embryos of calves. In the basolateral membranes of enterocytes, there is a slight decrease in the content of low molecular weight protein fractions, and from the four months of age of cattle fetus, high molecular weight fractions of polypeptides with molecular weights of 22.5 kDa and 155 kDa appear, which are absent in basolateral membranes of enterocytes. Two-month-old fetus lack proteins with a molecular weight of 19 kDa, 24 kDa, and 66 kDa in the apical part, whereas proteins with a mass of 22.5 kDa, 155 kDa, 170–185 kDa, and 205 kDa are absent on the basolateral membrane. In the apical membrane of enterocytes significantly more proteins with a low molecular weight of 9.6-14.2 kDa (1.56 times; P ≤ 0.001), whereas in the basolateral membrane a significantly higher concentration of proteins with a molecular weight of 15.5 kDa (2.06 times; P ≤ 0.001) and 17 kDa (3.62 times; P ≤ 0.001).

Structural proteins of plasmolemma of the jejunum absorbing enterocytes of cattle fetus in early fetal period

The data on the concentration of structural proteins of plasmolemma of the absorption enterocytes of the cattle fetus in the early fetal period are presented. Changes in the protein composition of the apical and basolateral membranes of enterocytes are manifested, characterized not only by changes in their ratio within different cell domains, but also by the dynamic redistribution of the number of different fractions of polypeptides between the poles of these cells. Analysis of the results of electrophoresis of apical membranes of the cattle fetus enterocytes in the early fetal period indicates a decrease in the content of low molecular weight protein fractions and an increase in high molecular weight. In the apical membranes of enterocytes of two-month-old cattle fetus, 25 protein fractions with a molecular weight of 9.6 to 205 kDa were detected. In the basolateral membranes revealed 23 protein fractions with a molecular weight of 9.6 to 120 kDa. High molecular weight fractions of polypeptides with molecular weights of 250 kDa and 300 kDa appear from the age of three months of embryos of calves. In the basolateral membranes of enterocytes, there is a slight decrease in the content of low molecular weight protein fractions, and from the four months of age of cattle fetus, high molecular weight fractions of polypeptides with molecular weights of 22.5 kDa and 155 kDa appear, which are absent in basolateral membranes of enterocytes. Two-month-old fetus lack proteins with a molecular weight of 19 kDa, 24 kDa, and 66 kDa in the apical part, whereas proteins with a mass of 22.5 kDa, 155 kDa, 170–185 kDa, and 205 kDa are absent on the basolateral membrane. In the apical membrane of enterocytes significantly more proteins with a low molecular weight of 9.6-14.2 kDa (1.56 times; P ≤ 0.001), whereas in the basolateral membrane a significantly higher concentration of proteins with a molecular weight of 15.5 kDa (2.06 times; P ≤ 0.001) and 17 kDa (3.62 times; P ≤ 0.001).

Reactive extrusion mechanism, mechanical and tribological behavior of fiber reinforced polyamide 66 with added carbodiimide

In this study, the reactive extrusion mechanism of fiber-reinforced polyamide 66 materials with added carbodiimide was clarified, and the mechanical and tribological properties of the materials were evaluated. Increasing the molecular weight of resin is one of the methods that has been proposed to improve the wear resistance and toughness of fiber-reinforced materials. This study proposes a reactive extrusion method using poly-carbodiimide compounds. The effects of the feeding position of the poly-carbodiimide compounds in the twin screw extruder, type of carbodiimide compounds, and proportion of carbodiimide compounds on the extrusion reaction and static mechanical properties were elucidated. The toughness of the glass fiber-reinforced polyamide 66 was improved by the increase in molecular weight of the polyamide 66 related to the addition of the carbodiimide compounds. The wear resistance properties were significantly improved by the addition of carbodiimide compounds for both glass fiber-reinforced polyamide 66 and aramid fiber-reinforced polyamide 66 materials. In addition, a synergistic improvement in the toughness was also observed with the addition of both carbodiimide compounds and a maleic anhydride modified olefin polymer to the glass fiber-reinforced polyamide 66 material. The results of this study will be beneficial for improving the mechanical and tribological properties of extruded resins.