PS Content Research Articles

Hard wood‐composites made of rice straw and recycled polystyrene foam wastes

ABSTRACTThe submitted work discussed the possibility of using two of the most problematic wastes to formulate an added‐value hard wood‐composite (HWC). The lignocellulosic rice straws (RS) fibers (as reinforced filler) and recycled expanded polystyrene foam (PS) wastes (as dispersed polymer matrix), were used to formulated the hard wood product applying the hot press technique. The air dried RS was added to the molten PS at increasing ratios (30–70% mass:mass), and the reached HWC sheet was subjected to tensile strength, water absorption and acoustic resistance characterizations. Based on the experimental data, it was found that increasing the RS contents accompanied with a diminish in the tensile strength value by about 50% at 70% RS compare to that at 30% RS. To improve the adhesion between the hydrophilic filler RS and the hydrophobic PS matrix, maleated PS graft (PS‐g‐MA) was prepared and added at the expanse of the PS content, to formulate an additional wood‐composite (HWCg) aiming to have better mechanical and dimensional stability features. Results obtained indicated that increasing the coupling agent content, keeping the RS added constant, enhance the tensile strength feature in addition, reduced the water absorption for the final products by more than 45%. The data obtained suggested that, it can create added‐value hard wood composites entirely from the two nominated problematic wastes. In addition to the value gained by the environment, the reached hard wood products record acceptable mechanical characterization, dimensional stability and sound resistance properties that qualified it to replace the natural wood in many daily applications. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44770.

Evolution of shell formation process in PP/PMMA/PS ternary blends: correlation between the melt rheology and phase morphology

Correlation between the melt rheology and phase morphology of PP/PMMA/PS ternary blends during the shell formation process were studied in detail. In this PP-matrix ternary system, theoretical predictions in agreement with the direct SEM observations demonstrated the core-shell morphology with PMMA and PS phases as core and shell phases, respectively. Morphological observations revealed that the complete shell formation takes place at about 12 and 9 wt% of PS minor phase in ternary blends composed of low and high viscosity PMMAs, respectively. In terms of rheological properties, this was corresponding to the maximum value on the storage modulus versus PS content (shell thickness) curves. Encapsulation of high viscosity PMMA core particles at lower PS contents was related to the bigger particles and low interfacial area in this system compared to the system with low viscosity PMMA core particles. At high PS contents, single and multi-core structures were observed for composite droplets of ternary blends containing low and high viscosity PMMAs, respectively. The single core morphology of low viscosity PMMA particles was related to the coalescence of core particles after the coalescence of the corresponding shells, while high viscosity PMMA cores are less likely to coalescence, leading to creation of multi-core morphology in latter system.

Performance evaluation and microbial community of a sequencing batch biofilm reactor (SBBR) treating mariculture wastewater at different chlortetracycline concentrations

The effects of chlortetracycline (CTC) on the performance, microbial activity, extracellular polymeric substances (EPS) and microbial community of a sequencing batch biofilm reactor (SBBR) were investigated in treating mariculture wastewater. Low CTC concentration (less than 6 mg/L) had no obvious effect on the SBBR performance, whereas high CTC concentration could inhibit the chemical oxygen demand (COD) and nitrogen removal of the SBBR. The microbial activity of the biofilm in the SBBR decreased with the increase of CTC concentration from 0 to 35 mg/L. The protein (PN) contents were always higher than the PS contents in both loosely bound EPS (LB-EPS) and tightly bound EPS (TB-EPS) at different CTC concentrations. The chemical compositions of LB-EPS and TB-EPS had obvious variations with the increase of CTC concentration from 0 to 35 mg/L. The high-throughput sequencing revealed the effects of CTC on the microbial communities of the biofilm at phylum, class and genus level. The relative abundances of some genera displayed a decreasing tendency with the increase of CTC concentration from 0 to 35 mg/L, such as Nitrospira, Paracoccus, Hyphomicrobium, Azospirillum. However, the relative abundances of the genera Flavobacterium, Aequorivita, Buchnera, Azonexus and Thioalbus increased with the increase of CTC concentration.

Controlling the fluorescence behavior of 1-pyrenesulfonate by cointercalation with a surfactant in a layered double hydroxide.

Zn-Al layered double hydroxides (LDHs) containing solely 1-pyrenesulfonate (PS) or 1-heptanesulfonate (HS) anions, or a mixture of the two with HS/PS molar ratios ranging between ca. 7.5 and 82, were prepared by the direct synthesis method and characterized by powder X-ray diffraction, thermal and elemental analyses, scanning electron microscopy, and FT-IR, FT-Raman, and (13)C{(1)H} CP MAS NMR spectroscopies. Well-ordered intercalates were obtained with basal spacings of 18.8 Å for the LDH intercalated by PS and 19.2-19.4 Å for the other materials containing HS. The photophysics of the solids, as well as the PS probe dissolved in water and common organic solvents (aiming to compare the behavior of the "isolated" molecule with that in the solid), were investigated by steady-state and time-resolved fluorescence techniques. The fluorescence spectra of the solid samples display two bands with maxima at 376 and 495 nm. Depending on the HS/PS ratios, the band intensity ratio (obtained at 375 and 520 nm) changes, reflecting different contributions from monomer and dimer species. The decays collected at 375 nm are biexponentials with a major component (∼97% of the total fluorescence) of 105 ns for the highest HS/PS ratio, which further loses importance with an increase in the PS content. When the decays are collected at 480 and 520 nm, the fits are triexponentials with a major component varying from 108 to 124 ns, attributed to an excimer. Steady-state and time-resolved measurements with PS in solution (ethanol, methanol, DMF, DMSO, and water) were also measured, and a comparison of the vibronic I1/I3 ratio and lifetimes in water (65 ns) with those in the LDHs indicates that the PS probe in the cointercalated LDHs is surrounded by the HS surfactant.

Molecular weight effect of partially sulfonated PS-b-PDMS diblock copolymers as proton exchange membrane for direct methanol fuel cell

Partially sulfonated polystyrene-b-poly(dimethylsiloxane) (sPS-b-PDMS) block copolymer membranes were prepared using three different polymers with various molecular weights and block ratios. Eleven different products were obtained with controlled degree of sulfonation (DS) of PS block ranging from 22% to 48%, and they were cast into proton exchange membranes (PEMs). Each PEM was rigorously characterized to see the effect of molecular weight and PS content to PEM for direct methanol fuel cells (DMFC). The first set of sPS-b-PDMS with the highest molecular weight and 50% PS block ratio generally showed high mechanical strength and selectivity (proton conductivity/ methanol permeability), and the second set with medium molecular weight and 60% PS ratio showed high proton conductivity. The last PEM with the lowest molecular weight and 80% PS ratio exhibited a poor tensile strength which is not suitable for PEM application. When the membrane/electrode assemblies (MEAs) were fabricated using the sPS-b-PDMS PEMs with moderately high DS (~40%), one from the second set (moderate molecular weight, 60% PS content) showed the best power performance (90 mW/cm2 at 70 °C) in active mode DMFC operation, which was found to be 20% higher than that of Nafion 115 MEA.

Cylinder Orientation and Shear Alignment in Thin Films of Polystyrene–Poly(n-hexyl methacrylate) Diblock Copolymers

Thin films of cylinder-forming polystyrene–poly(n-hexyl methacrylate) diblock copolymers, PS–PHMA, are attractive as nanolithographic templates, an application which demands good control over the thin-film structure—yet the quality of order achieved to date in PS–PHMA films has fallen short of this ideal. In the present work, a series of PS–PHMA diblocks of varying composition, all forming PS cylinders, are synthesized and their morphology studied as a function of film thickness in both nonsheared and shear-aligned films. In nonsheared films, the cylinder axis orientation relative to the surface switches from parallel to perpendicular as a function of film thickness; this oscillation is damped out as the fraction of the cylinder-forming block (PS) increases, away from the sphere–cylinder phase boundary. In aligned films, thicknesses which possess the highest coverage of parallel cylinders prior to shear show the highest quality of alignment postshear, as measured by the in-plane orientational order parameter of the cylinder axis. In well-aligned samples of optimal thickness, the quality of alignment is limited by isolated dislocations, whose density is highest at high PS contents, and by undulations in the cylinders’ trajectories, whose impact is most severe at low PS contents; consequently, polymers whose compositions lie in the middle of the cylinder-forming region exhibit the highest quality of alignment.

Some Studies on Poly (vinyl chloride)/Layered Silicate Nanocomposites: Electrical, Antibacterial and Oxygen Barrier Properties

The influence of 1.31PS organoclay content relative to PGV grade on the properties of PVC compounds was analyzed. Dielectric properties (i.e. permittivity ' & dielectric loss  ) of the PVC nanocomposites were investigated in the frequency range 10 2 - 10 5 Hz at room temperature  25 o C. In addition to the dielectric properties the experimental data of conductivity term  were also detected. The initial results show that nanoparticles of 1.31PS clay can improve electrical insulation properties of PVC by lowering (at 2.5 phr) and  (at 4 phr). The nano 1.31PS shows a significant influence on the electrical resistivity of PVC by enhancing it up to 1.4 x 10 -11 ohm.cm. Biodegradation percentage (BD%) and optical density (OD) of tested samples have been screened in testes against both Gram-positive bacteria such as Micrococcus luteus RM1 and Gram-negative bacteria such as Pseudomonas aeruginosa HR1.The particle size and morphology of PVC/1.31PS was found to play a significant role in indicating the antimicrobial efficiency. The results indicate a remarkable and significant resistance of PVC/1.31PS (2.5phr) to both kinds of microorganism, as compared with PVC containing 1.31PS (10phr). The oxygen permeability was measured at 23 o C and 50% relative humidity. With increasing 1.31PS content up to 6 phr the oxygen permeability of the PVC matrix is reduced based on the tortuous path formation.

Analysis of the Rheological Behavior and Stability of Inconel 718 Powder Injection Molding (PIM) Feedstock

In PIM process, the molding stage is a critical step for the fabrication of sound parts without cracks and distortions. So, this step requires specific rheological behavior. Rheological analysis can be made to quantify the stability of the PIM feedstock during molding process. In this study, an experimental rheological study has been performed to evaluate the influence of palm stearin on the rheological behavior and stability of Inconel 718 powder injection molding (PIM) feedstock. The effects of shear rate and temperature were investigated via capillary rheometer method. The viscosity and shear rate of the feedstock were measured at various range of temperature and shear rate across the L/D = 1 capillary rheometer. The results show that the formulation binder system PSPE 7030 is the best feedstock to be injection molded because it has moderate value of flow sensitivity index, lower value for flow activation energy and higher value for mold ability index. Besides that, the increasing of PS content in the binder system has found reduce viscosity and value of flow activation energy and increase value of mold ability index of feedstock.

Effect of pH on the effectiveness of whey protein/glycerol edible films containing potassium sorbate to control non-O157 shiga toxin-producing Escherichia coli in ready-to-eat foods

Potassium sorbate (PS) (0.5%, 1.0% and 1.5% w/w) was included into whey protein concentrate (WPC)/glycerol (Gly) edible films at pH 5.2 and 6.0. The films inhibited or retarded the growth of Shiga toxin-producing Escherichia coli (STEC) pathogens in both diffusion and barrier tests. Bacterial growth inhibition was dependent on PS content at both pH values. PS release was not affected by pH. Scanning electron microscopy (SEM) was used to analyze the microstructure of the films and gain a better understanding of their optical parameters. Acidic control films (pH 5.2) prepared without PS were the least transparent. SEM micrographs confirmed the greater structural heterogeneity of these films, coinciding with opacity. The incorporation of PS into WPC/Gly films improved transparency and produced a smoother surface than acidic control ones. The utilization of active packaging based on whey proteins and organic acids to control and prevent the dissemination of STEC pathogens may be an effective, safe, ecological and relatively inexpensive alternative to be used in the food packaging industry.

Investigation of Sodium Benzoate and Potassium Sorbate Content and Evaluation of Microbiological Parameters of Fresh Kashar Cheeses

Food safety is important issue for consumers and recently the usage of food ingredients especially food preservatives are limited by regulations. However, some manufacturers use food preservatives instead of improving their hygienic production. Therefore, the levels of sodium benzoate and potassium sorbate of 147 vacuum packaged Kashar (fresh) cheese samples produced in Black Sea Region, Turkey were investigated and some microbiological properties were determined. Research results demonstrated that the production of vacuumed Kashar cheese in Black Sea Region was not standardized for all production periods depending on the microbiological properties. Coliform and E. coli counts detected in the cheese samples showed that necessary hygienic conditions were not provided for Kashar cheese production. Staphylococcus aureus was not determined in the cheese samples. The sodium benzoate and potassium sorbate were analyzed by HPLC-DAD. Potassium sorbate levels (69.39 mg/kg) of Kashar cheese samples were determined to be lower than the maximum permitted concentration of Turkish Food Codex. Although the utilization of sodium benzoate is prohibited by the Codex, the average level of sodium benzoate of cheese samples was detected to be 68.63 mg/kg. Sodium benzoate can be naturally occurred in fresh cheese at concentrations of up to 50 mg/kg.

Lactadherin C2 Domain Exhibits Ptd-L-Ser Specificity and Anticoagulant Properties Distinct From Homologous Factor VIII C2 Domain and Full-Length Lactadherin

AbstractAbstract 1105 Background:Lactadherin (aka mfg-e8) is a milk-fat globule membrane protein with a domain structure of EGF1-EGF2-C1-C2, where the lectin-like C1 and C2 domains are homologous to the membrane binding domains of factor VIII and factor V. Like factor VIII and factor V, lactadherin exhibits calcium-independent membrane binding that is selective for phosphatidyl-L-serine (Ptd-L-Ser). Lactadherin also binds preferentially to convex membranes, competes efficiently for binding sites of factor VIII and factor V, and can function as an anticoagulant via competition for these binding sites. On stressed endothelial cells lactadherin binds to filopodia and the cell margins, identifying sites that have exposed Ptd-L-Ser and support assembly of the prothrombinase complex.The crystallographic structure of the lactadherin C2 domain (Lact-C2) and structure-function studies have shown that membrane binding is mediated by a longer β-hairpin turn, with different residues than fVIII-C2 and fV-C2. Further, we have shown that Lact-C2 maintains specificity for phosphatidylserine, in contrast to fVIII-C2, and that fluorescent fusion proteins containing Lact-C2 can be used as intracellular phosphatidylserine probes (Yeung et al. Science 2008;319:210). However, the extent to which Lact-C2 retains the membrane binding and anticoagulant properties of full-length lactadherin, has not been studied. Methods:Lact-C2 was produced in E. coliand purified by metal ion chromatography followed by gel filtration. Competition experiments were performed by flow cytometry using phospholipid bilayers supported by glass microspheres to determine Lact-C2's ability to block binding sites of FITC-labeled lactadherin, or fluorescein-labeled factor VIII and factor V. Lact-C2 was also labeled with FITC to measure its binding to sonicated or 100 nm diameter, extruded vesicles with varying PS content in order to assess Ptd-L-Ser selectivity and membrane curvature sensitivity. Two-step amidolytic factor Xase and prothrombinase assays were used to assess the ability of Lact-C2 to block activity. Fluorescence microscopy experiments were used to compare the binding of Alexa 647-labeled Lact-C2 vs. FITC-labeled lactadherin on staurosphorine-treated HeLa cells. Results:Lact-C2 showed stereospecific binding to Ptd-L-Ser vs. Ptd-D-Ser in vesicles of 4% and 10% PS. Lact-C2 was sensitive to vesicle curvature, detecting as little as 1% Ptd-L-Ser on sonicated vesicles but requiring 4% Ptd-L-Ser on extruded vesicles. Lact-C2 competed for 89% of lactadherin binding sites and 84% of factor VIII binding sites. Inhibition of factor Xase activity plateaued at 89% reduction vs. >99% reduction for lactadherin. Lact-C2 also competed for 61% of factor V binding sites corresponding to an 82% reduction in prothrombinase activity. We are currently comparing the distribution of binding sites for Lact-C2 vs. lactadherin on stressed HeLa cells, with preliminary data showing distinct, but overlapping, binding site distribution. Discussion:Lact-C2 exhibits stereospecific Ptd-L-Ser binding and convex curvature preference similar to full-length lactadherin. Lact-C2 contrasts with fVIII-C2 in Ptd-L-Ser specificity and capacity to compete with factor VIII and inhibit factor Xase activity and prothrombinase activity.These results provide a framework for interpreting experiments in which Lact-C2 is used as an anticoagulant or as a calcium-independent probe for exposed membrane Ptd-L-Ser. Lact-C2 is able to bind to only a subset of lactadherin binding sites, highlighting the importance of the lactadherin C1 domain for high affinity binding and underscoring the largely unappreciated complexity of phospholipid membrane binding sites. Disclosures:Shi:Brigham and Women’s Hospital: Use of Lactadherin to detect phosphataidylserine, Use of Lactadherin to detect phosphataidylserine Patents & Royalties.

SUI-family genes encode phosphatidylserine synthases and regulate stem development in rice

In vascular plants, the regulation of stem cell niche determines development of aerial shoot which consists of stems and lateral organs. Intercalary meristem (IM) controls internode elongation in rice and other grasses, however little attention has been paid to the underlying mechanism of stem cell maintenance. Here, we investigated the stem development in rice and showed that the Shortened Uppermost Internode 1 (SUI1) family of genes are pivotal for development of rice stems. We demonstrated that SUI-family genes regulate the development of IM for internode elongation and also the cell expansion of the panicle stem rachis in rice. The SUI-family genes encoded base-exchange types of phosphatidylserine synthases (PSSs), which possessed enzymatic activity in a yeast complementary assay. Overexpression of SUI1 and SUI2 caused outgrowths of internodes during vegetative development, and we showed that expression patterns of Oryza Sativa Homeobox 15 (OSH15) and Histone4 were impaired. Furthermore, genome-wide gene expression analysis revealed that overexpression and RNA knockdown of SUI-family genes affected downstream gene expression related to phospholipid metabolic pathways. Moreover, using Ultra-performance liquid chromatography-quadrupole time of flight-mass spectrometry, we analyzed PS contents in different genetic backgrounds of rice and showed that the quantity of very long chain fatty acids PS is affected by transgene of SUI-family genes. Our study reveals a new mechanism conveyed by the SUI1 pathway and provides evidence to link lipid metabolism with plant stem cell maintenance.

Reuse of waste sludge from papermaking process in cement composites

AbstractPapermaking sludge (PS), a waste residue from the pulp and paper processing, has brought great pressure on the environment because of large quantities that are produced in paper mills. This work was carried out to explore the possibility of making PS/cement composite products using solid waste of PS. Boards measuring 350 × 270 × 12 mm3 were manufactured using PS contents of 40, 50, and 60 wt%, adhesive dosages of 0, 10, and 15 wt%, and 0 and 5 wt% of calcium chloride as an accelerator. At least three replications were fabricated for each treatment, and some mechanical and physical properties of the boards were evaluated. Test results showed that the bending and internal strengths of the specimens decreased with an increase in the PS content, and the maximum values were obtained at PS loading of 40 wt%. The negative influence of PS content on the mechanical properties can be explained by the reduced bonding ability because of weaker PS compared with cement. Screw withdrawal values were up to 22.7 kPa. Water absorption and thickness swelling of cement mortar considerably increased with increased content of PS, with a corresponding reduction of bulk density. In general, all properties of the boards were improved when the adhesive and calcium chloride contents were increased. The results showed that an increase in board density improved the mechanical and physical properties. Finally, results showed that PS has good potential for recycling and utilization in developing value‐added building components. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers

Spectroscopic Studies on the Interaction of Mefloquine with Phosphatidylcholine- Phosphatidylserine Bilayer Vesicle and Bovine Serum Albumin

To assess the interaction of mefloquine (MQ) with biomembranes and serum albumin, the partitioning of MQ into phosphatidylcholine-phosphatidylserine small unilamellar vesicles (PC-PS SUV) and its binding with bovine serum albumin (BSA) were examined using various spectroscopic methods. The partition coefficients (Kps) of MQ, determined by the second-derivative spectrophotometric method, increased in accordance with the PS content in PC-PS SUV: the Kp values for PC-PS SUV with PS contents of 10 mol% were about 2.5 times that for PC SUV. The zeta potential values of PC-PS SUV fell from -10 mV at a PS content of 0 mol% to -42 mV at PS contents of 10 mol%, and were found to depend to some extent on the Kp values. Meanwhile, the binding constant (logK) and the number of binding sites (n) for the binding of MQ to BSA were determined using a fluorescence quenching method. These values were significantly reduced by the presence of Cl– ions, from 5.55 to 4.66 for logK and from 1.30 to 1.11 for n. To examine the binding site of MQ on BSA, a 19F nuclear magnetic resonance (NMR) spectroscopic study was performed using typical competing ligands bound to BSA. The results revealed that whereas most of the MQ binds nonspecifically to BSA, MQ also partially binds to Site II. Finally, these results showed that the major interactions between MQ and PC-PS SUV or BSA were essentially different; the partitioning of MQ into PC-PS SUV was electrostatic and the binding of MQ to BSA was hydrophobic. Keywords: Binding constant, Bovine serum albumin, Fluorescence quenching, 19F nuclear magnetic resonance, Liposome, Mefloquine, Partition coefficient, Phosphatidylcholine, Phosphatidylserine, Second-derivative spectrophotometry, Zeta potential

Stick–Slip Phenomenon in Measurements of Dynamic Contact Angles and Surface Viscoelasticity of Poly(styrene-b-isoprene-b-styrene) Triblock Copolymers

In this paper, a series of poly(styrene-b-isoprene-b-styrene) triblock copolymers (SIS), with different chemical components, was synthesized by anionic polymerization. The relationships between surface structures of these block copolymers and their stick-slip phenomena were investigated. There is a transition from stick-slip to a closely smooth motion for the SIS films with increasing PS content; the patterns almost vanish and the three-phase line appears to move overall smoothly on the film surface. The results show that the observed stick-slip pattern is strongly dependent on surface viscoelasticity. The jumping angle Δθ, which is defined as θ(1) - θ(2) (when a higher limit to θ(1) is obtained, the triple line "jumps" from θ(1) to θ(2) with increases in drop volume), was employed to scale the stick-slip behavior on various SIS film surfaces. Scanning force microscopy/atomic force microscopy (AFM) and sum frequency generation methods were used to investigate the surface structures of the films and the contributions of various possible factors to the observed stick-slip behavior. It was found that there is a linear relationship between jumping angle Δθ and the slope of the approach curve obtained from AFM force measurement. This means that the stick-slip behavior may be attributed mainly to surface viscoelasticity for SIS block copolymers. The measurement of jumping angle Δθ may be a valuable method for studying surface structure relaxation of polymer films.

Investigation on particular morphology of immiscible polyamide 12/polystyrene blends

AbstractIn this article, a particular phase morphology of immiscible polyamide 12/polystyrene (PA12/PS) blends prepared via in situ anionic ring‐opening polymerization of Laurolactam (LL) in the presence of PS was investigated. SEM and FTIR were used to analyze the morphology of the blends. The results showed that PS is dispersed as small droplets in the continuous matrix of PA12 when PS content is less than 5 wt %. When the PS content is higher than 10 wt %, two particular phase morphologies appeared. First, dispersed PS‐rich particles with the spherical inclusions of PA12 can be found when PS content is between 10 wt % and 15 wt %. Then, the phase inversion (the phase morphology of the PA12/PS blends changes from the PS dispersed/PA12 matrix to PA12 dispersed/PS matrix system) occurred when PS content is higher than 20 wt %, which is completely different from traditional polymer blends prepared by melt blending. The possible reason for the particular morphology development was illuminated through phase inversion mechanism. Furthermore, the stability of the phase morphologies of the PA12/PS blends was also investigated. SEM showed that the particular morphology is instability, and it will be changed upon annealing at 230°C for 30 min. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

A novel method for the synthesis of polyamide 6 magnetic microspheres

Polyamide 6 (PA6) magnetic microspheres were firstly prepared via successively in situ polymerization using phase inversion technology of polymer pairs polyamide 6/polystyrene (PA6/PS) at extremely low PS content. The properties of PA6 magnetic microspheres, such as morphologies, diameter size distribution, magnetic properties, thermal stability, and the functional groups of the magnetic microspheres, were investigated by different techniques (i.e. SEM, TEM, DLS, VSM, FTIR, and DSC). The results indicated that the diameter distribution of PA6 magnetic microspheres was narrow, and the mean diameter size was about 7.7 μm. The saturation magnetization of magnetic microspheres reached 12.50 emu/g. Furthermore, the magnetic microspheres had abundant functional groups and better thermal stability.

Preparation of microcellular polypropylene/polystyrene blend foams with tunable cell structure

AbstractBy using supercritical carbon dioxide (sc‐CO2) as the physical foaming agent, microcellular foaming was carried out in a batch process from a wide range of immiscible polypropylene/polystyrene (PP/PS) blends with 10–70 wt% PS. The blends were prepared via melt processing in a twin‐screw extruder. The cell structure, cell size, and cell density of foamed PP/PS blends were investigated and explained by combining the blend phase morphology and morphological parameters with the foaming principle. It was demonstrated that all PP/PS blends exhibit much dramatically improved foamability than the PP, and significantly decreased cell size and obviously increased cell density than the PS. Moreover, the cell structure can be tunable via changing the blend composition. Foamed PP/PS blends with up to 30 wt% PS exhibit a closed‐cell structure. Among them, foamed PP/PS 90:10 and 80:20 blends have very small mean cell diameter (0.4 and 0.7 µm) and high cell density (8.3 × 1011 and 6.4 × 1011 cells/cm3). Both of blends exhibit nonuniform cell structure, in which most of small cells spread as “a string of beads.” Foamed PP/PS 70:30 blend shows the most uniform cell structure. Increase in the PS content to 50 wt% and especially 70 wt% transforms it to an irregular open‐cell structure. The cell structure of foamed PP/PS blends is strongly related to the blend phase morphology and the solubility of CO2 in PP more than that in PS, which makes the PP serve as a CO2 reservoir. Copyright © 2009 John Wiley & Sons, Ltd.

Micelles of PAAm-b-PEO-b-PAAm Triblock Copolymers and Their Binding with Prednisolon

The IntraPC forming asymmetric PAAm-b-PEO-b-PAAm triblock copolymers (TBCs) composed of poly(ethylene oxide) (M v = 6 · 103 and 1.4 · 104) and polyacrylamide of a variable chain length form “hairy-type” micelles in water and “flower-like” micelles at the addition of EtOH > 40 vol %. The specific micellization is developed in TBC aqueous/ethanol solutions (EtOH content < 30 vol %) at the PS introduction. It is caused by the binding of PS with TBC micelles due to hydrogen bonds and hydrophobic interactions. The amorphous structure of TBCs and polymorphic crystalline structures of PS are found. The products of the interaction of TBC and PS contain highly ordered crystalline structures of the drug. But it is possible to avoid the drug crystallization at low PS contents.

Morphology-properties relationship on nanocomposite films based on poly(styrene-block-diene-block-styrene) copolymers and silver nanoparticles

A comparative study on the self-assembled nanostructured morphology and the rheological and mechanical prop- erties of four different triblock copolymers, based on poly(styrene-block-butadiene-block-styrene) and poly(styrene-block- isoprene-block-styrene) matrices, and of their respective nanocomposites with 1 wt% silver nanoparticles, is reported in this work. In order to obtain well-dispersed nanoparticles in the block copolymer matrix, dodecanethiol was used as surfac- tant, showing good affinity with both nanoparticles and the polystyrene phase of the matrices as predicted by the solubility parameters calculated based on Hoftyzer and Van Krevelen theory. The block copolymer with the highest PS content shows the highest tensile modulus and tensile strength, but also the smallest elongation at break. When silver nanoparticles treated with surfactant were added to the block copolymer matrices, each system studied shows higher mechanical properties due to the good dispersion and the good interface of Ag nanoparticles in the matrices. Furthermore, it has been shown that semi- empirical models such as Guth and Gold equation and Halpin-Tsai model can be used to predict the tensile modulus of the analyzed nanocomposites.