Termination in Semi-Dilute and Concentrated Polymer Solutions

2009 ◽  
Vol 62 (8) ◽  
pp. 857 ◽  
Author(s):  
Geoffrey Johnston-Hall ◽  
Michael J. Monteiro
Keyword(s):  
Chain Length ◽  
Power Law ◽  
Polymer Solutions ◽  
Polymer Concentration ◽  
Star Polymer ◽  
Polymer Systems ◽  
Theoretical Predictions ◽  
The Matrix ◽  
Concentrated Solution ◽  
Blob Model

The aim of the present work was to develop a deeper understanding into termination processes in the semi-dilute and concentrated regimes. The study was carried out to examine the effect of termination between linear polystyrene radical chains in linear, four-arm star, and six-arm star polymer systems using the reversible addition–fragmentation chain transfer chain length-dependent termination method. In particular, the power-law dependencies of both chain length and polymer concentration were evaluated in the semi-dilute and concentrated regimes. We found that theoretical predictions based on the blob model were in good agreement with the experimentally observed evolution of the rate coefficient for biomolecular termination, kti,i(x), in the semi-dilute solution regime. In addition, solvent quality was found to decrease with increasing chain length, increasing polymer concentration and as a function of the matrix topology (i.e. for star polymer solutions). In the concentrated solution regime, the role of chain entanglements became evident by determining the conversion-dependent power-law exponent, βgel (where kt ≈ x–βgel), which increased in the order: linear < four-arm star < six-arm star polymer systems. Above the critical chain length ic, termination was found to be primarily conversion-dependent, implying entanglements dominated termination between linear polymeric radicals. Although this may suggest that reptation plays an important role, our data are in disagreement with this theory, suggesting that the polymer matrix cannot be regarded as static or immobile on the diffusion time scales for bimolecular termination.

Influence of Formulation Variables and Processing Techniques on Drug Release from Carbopol-971 based Matrix Tablets of Cinnarizine and Nimodipine.

2010 ◽  
Vol 2 (1) ◽  
Author(s):  
Singh K. ◽  
Pandit K. ◽  
Mishra N.
Keyword(s):  
Drug Release ◽  
Release Rate ◽  
Polymer Concentration ◽  
Matrix Tablets ◽  
Wet Granulation ◽  
Weight Variation ◽  
Diffusion Controlled ◽  
The Matrix ◽  
Processing Techniques ◽  
Formulation Variables

The matrix tablets of cinnarizine and nimodipine were prepared with varying ratio of Carbopol- 971P and co-excipients of varying hydrophilicity (i.e. dicalcium phosphate and spray dried lactose) by direct compression and wet granulation using alcoholic mucilage. The prepared tablets were evaluated for weight variation, hardness and friability. The influence of concentration of the matrix forming material and co-excipients on the release rate of the drug was studied. The release rate of Cinnarizine (more soluble drug) from tablets followed diffusion controlled mechanism whereas for nimodipine (less soluble drug), the drug release followed case-II or super case- II transport mechanism based on Korsmeyer- Peppas equation. The results indicated that the drug release from matrix tablets was increases with increase in hydrophilicity of drug and co-excipients. The release of drug also increased with thermal treatment and decreasing polymer concentration.

scholarly journals A mechanism for fire retardancy realized by a combination of biofillers and ammonium polyphosphate in various polymer systems

Cellulose ◽  
2021 ◽  
Author(s):  
Koki Matsumoto ◽  
Tatsuya Tanaka ◽  
Masahiro Sasada ◽  
Noriyuki Sano ◽  
Kenta Masuyama
Keyword(s):  
Polymer Matrix ◽  
Synergetic Effect ◽  
Polymer System ◽  
Ammonium Polyphosphate ◽  
Fire Retardancy ◽  
Polymer Systems ◽  
Thermal Decomposition Behavior ◽  
Burning Behavior ◽  
The Matrix ◽  
Decomposition Behavior

AbstractThis study focused on realizing fire retardancy for polymer composites by using a cellulosic biofiller and ammonium polyphosphate (APP). The motivation of this study was based on revealing the mechanism of the synergetic effect of a cellulosic biofiller and APP and determining the parameters required for achieving a V-0 rating in UL94 standard regardless of the kind of polymer system used. As for the polymer matrix, polypropylene and polylactic acid were used. The flammability, burning behavior and thermal decomposition behavior of the composites were investigated through a burning test according to the UL-94 standard, cone calorimetric test and thermogravimetric analysis. As a result, the incorporation of a high amount of cellulose enabled a V-0 rating to be achieved with only a small amount of APP despite the variation of the optimum cellulose loading between the matrix polymers. Through analysis, the results indicated that APP decreased the dehydration temperature of cellulose. Furthermore, APP promoted the generation of enough water as a nonflammable gas and formed enough char until the degradation of the polymer matrix was complete. The conditions required to achieve the V-0 rating were suggested against composites incorporating APP and biofillers. Furthermore, the suggested conditions were validated by using polyoxymethylene as a highly flammable polymer.

Macro- to Atomic-Scale Tailoring of Si3N4 Ceramics to Enhance Properties

2005 ◽  
Vol 287 ◽  
pp. 233-241 ◽  
Author(s):  
Paul F. Becher ◽  
Gayle S. Painter ◽  
Naoya Shibata ◽  
Hua Tay Lin ◽  
Mattison K. Ferber
Keyword(s):  
Electronic Device ◽  
Atomic Level ◽  
Atomic Scale ◽  
Fracture Properties ◽  
Beta Particles ◽  
Preferential Segregation ◽  
Nitride Ceramics ◽  
Theoretical Predictions ◽  
The Matrix

Silicon nitride ceramics are finding uses in numerous engineering applications because of their tendency to form whisker-like microstructures that can overcome the inherent brittle nature of ceramics. Studies now establish the underlying microscopic and atomic-scale principles for engineering a tough, strong ceramic. The theoretical predictions are confirmed by macroscopic observations and atomic level characterization of preferential segregation at the interfaces between the grains and the continuous nanometer thick amorphous intergranular film (IGF). Two interrelated factors must be controlled for this to occur including the generation of the elongated reinforcing grains during sintering and debonding of the interfaces between the reinforcing grains and the matrix. The reinforcing grains can be controlled by (1) seeding with beta particles and (2) the chemistry of the additives, which also can influence the interfacial debonding conditions. In addition to modifying the morphology of the reinforcing grains, it now appears that the combination of preferential segregation and strong bonding of the additives (e.g., the rare earths, RE) to the prism planes can also result in sufficiently weakens the bond of the interface with the IGF to promote debonding. Thus atomic-scale engineering may allow us to gain further enhancements in fracture properties. This new knowledge will enable true atomic-level engineering to be joined with microscale tailoring to develop the advanced ceramics that will be required for more efficient engines, new electronic device architectures and composites.

Heat capacities and volumes in aqueous polymer and polymer–surfactant solutions

1987 ◽  
Vol 65 (5) ◽  
pp. 990-995 ◽  
Author(s):  
Gérald Perron ◽  
Josée Francoeur ◽  
Jacques E. Desnoyers ◽  
Jan C. T. Kwak
Keyword(s):  
Thermodynamic Properties ◽  
Chain Length ◽  
Polymer Concentration ◽  
Heat Capacities ◽  
Aqueous Mixtures ◽  
Alkyltrimethylammonium Bromides ◽  
Aqueous Polymer ◽  
Surfactant Interactions ◽  
Polymer Surfactant ◽  
Polymer Interaction

The apparent molar volumes and heat capacities of aqueous mixtures of neutral polymers and ionic surfactants were measured at 25 °C. The polymers chosen were poly(vinylpyrrolidone) (PVP) and poly(ethyleneoxide) (PEO) and the surfactants were the C8, C10, and C12 homologs of sodium alkylsulfates and the C10, C12, and C16 homologs of alkyltrimethylammonium bromides. The polymer–surfactant interactions depend on the nature of both components and on the chain length of the surfactant. The thermodynamic properties of the cationic surfactants are essentially the same in the absence and presence of polymer indicating little surfactant–polymer interaction. On the other hand, the thermodynamic properties of anionic surfactants are shifted, upon the addition of polymers, in the direction of enhanced hydrophobic association. The effect increases with the surfactant chain length and with the polymer concentration. The effect is larger with PVP than with PEO.

Rheological Properties of Concentrated 1-Allyl-3-Methylimidazolium Chloride Cellulose Solutions

2011 ◽  
Vol 199-200 ◽  
pp. 3-6
Author(s):  
Fei Lu ◽  
Jun Song ◽  
Bo Wen Cheng ◽  
Hong Jun Zang ◽  
Yi Liang
Keyword(s):  
Power Law ◽  
Loss Modulus ◽  
Polymer Concentration ◽  
Normal Stress Difference ◽  
Stress Difference ◽  
Rheological Measurement ◽  
First Normal Stress Difference ◽  
Power Law Index ◽  
Cellulose Concentration ◽  
Newtonian Behavior

The viscosity behaviors and elastic properties of concentrated cellulose 1-allyl-3-methy -limidazolium Chloride solutions were investigated in the concentration from 10 wt% to 25 wt%. Rheological measurement showed that the solution was pesudoplastic fluid. The non-Newtonian behavior was improved and shear-thinning tendency became more pronounced with increasing polymer concentration. The power law index ranged from 0.19 to 0.30. The effects of cellulose concentration to the storage modulus G′ and the loss modulus G″ were analyzed. First normal stress difference (N1) increased with increasing concentration.

DENSITY, CONCENTRATION AND ORIENTATION FLUCTUATIONS IN DENSE POLYMER SYSTEMS AND POLYMER SOLUTIONS AS STUDIED BY DYNAMIC LIGHT SCATTERING AND COMPLEMENTARY TECHNIQUES

1991 ◽  
Author(s):  
Γιώργος Φλούδας
Keyword(s):  
Light Scattering ◽  
Dynamic Light Scattering ◽  
Polymer Solutions ◽  
Coupling Scheme ◽  
Polymer Systems ◽  
Density Concentration ◽  
Complementary Techniques

Η ΣΚΕΔΑΣΗ ΤΟΥ ΦΩΤΟΣ ΠΡΟΕΡΧΕΤΑΙ ΑΠΟ ΤΗΝ ΟΠΤΙΚΗ ΑΝΟΜΟΙΟΓΕΝΕΙΑ ΤΩΝ ΥΛΙΚΩΝ. Η ΑΝΟΜΟΙΟΓΕΝΕΙΑ ΠΡΟΚΥΠΤΕΙ ΑΠΟ ΤΙΣ ΔΙΑΚΥΜΑΝΣΕΙΣ ΤΗΣ ΟΠΤΙΚΗΣ ΔΙΗΛΕΚΤΡΙΚΗΣ ΣΤΑΘΕΡΑΣ ΣΑΝ ΑΠΟΤΕΛΕΣΜΑ ΤΩΝ ΔΙΑΚΥΜΑΝΣΕΩΝ ΤΗΣ ΠΥΚΝΟΤΗΤΑΣ, ΣΥΓΚΕΝΤΡΩΣΗΣ ΚΑΙ ΟΠΤΙΚΗΣ ΑΝΙΣΟΤΡΟΠΙΑΣ. ΕΔΩ ΧΡΗΣΙΜΟΠΟΙΟΥΜΕ ΤΗΝ ΤΕΧΝΙΚΗ ΤΗΣ ΦΑΣΜΑΤΟΣΚΟΠΙΑΣ ΣΥΣΧΕΤΙΣΗΣ ΓΙΑ ΝΑ ΜΕΛΕΤΗΣΟΥΜΕ ΤΗΝ ΔΥΝΑΜΙΚΗ ΤΩΝ ΔΙΑΚΥΜΑΝΣΕΩΝ ΤΗΣ ΠΥΚΝΟΤΗΤΑΣ ΣΤΟ ΣΥΣΤΗΜΑ PCHMA/DOPΣΕ ΘΕΡΜΟΚΡΑΣΙΕΣ ΠΑΝΩ ΚΑΙ ΚΑΤΩ ΑΠΟ ΤΟ ΣΗΜΕΙΟ ΥΑΛΟΥ (TG). ΤΟ ΑΠΟΤΕΛΕΣΜΑ ΤΟΥ ΠΡΟΣΘΕΤΟΥ (DOP) ΣΤΟΝ ΚΥΡΙΟ ΚΑΙ ΔΕΥΤΕΡΕΥΟΝΤΑ ΜΗΧΑΝΙΣΜΟ ΑΠΟΚΑΤΑΣΤΑΣΗΣ ΤΟΥ PHCMA ΕΞΗΓΟΥΝΤΑΙ ΑΠΟ ΠΡΟΣΦΑΤΕΣ ΘΕΩΡΙΕΣ. ΠΡΟΣΘΕΤΕΣ, ΔΥΝΑΜΙΚΕΣ ΜΗΧΑΝΙΚΕΣ ΚΑΙ ΔΙΗΛΕΚΤΡΙΚΕΣ ΜΕΤΡΗΣΕΙΣ - ΣΤΟ ΙΔΙΟ ΣΥΣΤΗΜΑ - ΣΥΓΚΡΙΝΟΝΤΑΙ ΜΕ ΤΙΣ ΜΕΤΡΗΣΕΙΣ ΑΠΟ ΤΗ ΣΚΕΔΑΣΗ. ΟΙ ΔΙΑΚΥΜΑΝΣΕΙΣ ΤΗΣ ΣΥΓΚΕΝΤΡΩΣΗΣ ΜΕΛΕΤΗΘΗΚΑΝ - ΓΙΑ ΠΡΩΤΗ ΦΟΡΑ - ΠΑΝΩ ΑΠΟ ΤΟ ΣΗΜΕΙΟ ΥΑΛΟΥ ΚΑΙ ΤΟ "COUPLING SCHEME" ΕΧΕΙ ΧΡΗΣΙΜΟΠΟΙΗΘΕΙ ΚΑΙ ΕΞΗΓΕΙ ΤΙΣ ΔΙΑΦΟΡΕΤΙΚΕΣ ΕΞΑΡΤΗΣΕΙΣ ΑΠΟ ΤΗ ΘΕΡΜΟΚΡΑΣΙΑ. ΠΡΟΣΘΕΤΑ, Ο ΠΡΟΣΑΝΑΤΟΛΙΣΜΟΣ ΜΙΚΡΩΝ ΜΟΡΙΩΝ ΜΕΣΑ ΣΕ ΠΟΛΥΜΕΡΗ ΜΕΛΕΤΗΘΗΚΕ ΚΑΙ ΒΡΕΘΗΚΕ ΙΣΧΥΡΗ ΑΛΛΑΓΗ ΤΩΝ ΙΔΙΟΤΗΤΩΝ ΤΟΥ ΜΙΚΡΟΥ ΜΟΡΙΟΥ (ΔΙΑΛΥΤΗ) ΑΠΟ ΤΗΝ ΠΑΡΟΥΣΙΑ ΤΟΥ ΠΟΛΥΜΕΡΟΥΣ.

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