Effect Of Polymeric Additives Research Articles

New insights into the nucleation of portlandite and the effects of polymeric additives

The crystallization of calcium hydroxide (Ca(OH)2, CH, portlandite) is a key process during the early stages of cement hydration. In the present work, we have revisited the formation of this mineral through nucleation and growth from supersaturated aqueous solutions, in the light of the currently emerging picture of multistage “non-classical” crystallization. To that end, we developed a titration-based assay, in which stock solutions of both relevant ions are added simultaneously into a reservoir, where supersaturation increases slowly at constant stoichiometry until nucleation occurs. This procedure allows both pre- and early post-nucleation phenomena to be analyzed quantitatively. Complementarily, the early stages of portlandite mineralization were probed by various advanced characterization techniques, including cryo-transmission electron microscopy (cryo-TEM), in-situ small-angle X-ray scattering (SAXS), pair distribution function (PDF) analysis of high-energy X-ray scattering (HEXS) data, and analytical ultracentrifugation (AUC). The experimental data show that the formation of calcium hydroxide starts with the association of ions into complexes and clusters, which subsequently coalesce to form amorphous nanoparticles – much like what has been observed in the case of calcium carbonate and other prominent minerals. Subsequently, these particles aggregate and build networks, which eventually transform into hexagonal Ca(OH)2 crystals. The presence of a soluble polycarboxylate – as a known inhibitor of portlandite crystallization – does not change the main characteristics of this multistep nucleation pathway, but it proved capable of significantly extending the lifetime of the amorphous intermediate phase and thus delaying the transition to the final crystalline phase. Our observations confirm the notion that “non-classical” crystallization is a much more common phenomenon than initially believed – and that, for minerals forming in aqueous environments, it may actually be the rule rather than the exception.

Strontium-loaded magnesium phosphate bone cements and effect of polymeric additives

Magnesium phosphate-based cements (MPCs) are nowadays regarded as promising materials in the field of bone repair. The inclusion of Sr ions in the formulations may represent a valuable strategy to improve their bone regeneration performances, but the effect that such ion exerts on the physico-chemical properties of the material have not been investigated so far. In this work we describe the development of Sr-MPCs obtained including Sr ions in different forms, i.e., using Sr-substituted tri-magnesium phosphate precursor powder or including in the formulation Sr-based salts (SrCl2 and SrHPO4). The materials were characterized both in the form of pastes and hardened cements, finding that according to the type of Sr precursor used we can tune the setting time, the amount of binding phases in the cements, their morphology and thermal behavior. The dissolution behavior and the release kinetics of Mg2+ and Sr2+ can as well be modulated, and in particular the use of SrCl2 in the formulation leads to a higher dissolution and a faster release of a significant amount of both Mg2+ and Sr2+, compared to the other samples. Given the unsatisfying performances obtained during the injectability and anti-washout tests, we also included two polymeric additives, namely poly(N-isopropylacrylamide) and mucin, in the Sr-MPCs formulations. The results demonstrate that it is possible to obtain Sr-MPCs with promising properties for applications as bone cements, that can be tuned according to the form under which Sr is included in the formulation. In addition, mucin markedly improves the cohesion and injectability of the Sr-MPC pastes, providing a simple but effective strategy to develop materials of interest in the orthopedic field.

A review of additives in abrasive water jet machining and their performance

Abrasive Water Jet Machining (AWJM) is an advanced machining process that has a variety of applications, including machining of hard-to-machine materials, drilling, milling, coating removal, polishing, etc. They are attractive because of their versatility, absence of heat-affected zones, low thermal-distortions, low cutting-forces, and environment-friendly nature. However, use of plain-water in AWJM poses some problems due to lack of jet coherence, poor suspension characteristics, and unsatisfactory performances in submerged-cutting and cutting of hollow surfaces. Countering these problems appropriately can lead to better cutting performances in terms of material removal rate, depth of cut, kerf-width, and kerf-taper. It can be achieved with addition of some additives in abrasive water-jet. These additives are mostly polymers of high molecular mass, which increases viscosity, suspension capability, and stability of jet, while reducing drag. In addition to AWJM, the effect of polymeric-additives in other water-based jets like Abrasive-Slurry-Jet (ASJ), High-pressure ASJ, etc. are also discussed. Therefore, this study aims to identify and list of different additives that are used in AWJM and other water-jet-based machining-processes over a past few decades, and to provide a run-through on their performances. It can provide the significant information to researchers working in fields related to waterjets.

Probing the effects of polymers on the early stages of calcium carbonate formation by stoichiometric co-titration.

Potentiometric titrations are a powerful tool to study the early stages of the precipitation of minerals such as calcium carbonate and were used among others for the discovery and characterisation of key precursors like prenucleation clusters. Here we present a modified procedure for conducting such titration experiments, in which the reactants (i.e. calcium and (bi)carbonate ions) are added simultaneously in stoichiometric amounts, while both the amount of free calcium and the optical transmission of the solution are monitored online. Complementarily, the species occurring at distinct stages of the crystallisation process were studied using cryogenic transmission electron microscopy. This novel routine was applied to investigate CaCO3 nucleation in the absence and presence of polymeric additives with different chemical functionalities. The obtained results provide new insights into the critical steps underlying nucleation and subsequent ripening, such as the role of liquid mineral-rich phases and their transformation into solid particles. The studied polymers proved to interfere at multiple stages along the complex mineralisation pathway of calcium carbonate, with both the degree and mode of interaction depending on the chosen polymer chemistry. In this way, the methodology developed in this work allows the mechanisms of antiscalants - or crystallisation modifiers in general - to be elucidated at an advanced level of detail.

Effect of Polymeric Additives on Ignition, Combustion and Flame Characteristics and Soot Deposits of Crude Oil Droplets

ABSTRACT Many oil fires have resulted from the crude oil train derailments in recent years. Given the importance of crude oil shipping by rail to the energy security of the US, it is important to consider various methods that will decrease the likelihood of crude oil catching fire in case of a crude oil derailment. Present study examines the effect of polybutadiene polymer on the combustion properties and soot deposits of Bakken crude. Treating crude oil as multicomponent liquid fuels and polybutadiene as an additive, droplet combustion experiments were conducted with sub-millimeter sized spherical droplets suspended on very fine support fibers. Polybutadiene polymer additive of two different chain lengths has been investigated. Results show that both polymer chain length and origin of crude oil have a significant effect on various combustion properties like combustion rate, ignition delay, and total combustion time. Polymeric additives also change the soot deposit structure and particle size compared to the base fuel. Present research is envisioned to aid in understanding combustion behavior of crude oil as isolated droplets, as well as to generate interest in investigating more polymeric additives for liquid fuels.

Effect of Polymeric Additives on Thermal and Electrical Conductivity of Nanofluids

Effect of Polymeric Additives on Thermal and Electrical Conductivity of Nanofluids

Effect of Polymeric Additives, Adjuvants, Surfactants on Survival, Stability and Plant Growth Promoting Ability of Liquid Bioinoculants

Effect of Polymeric Additives, Adjuvants, Surfactants on Survival, Stability and Plant Growth Promoting Ability of Liquid Bioinoculants The present study was conducted to evaluate the effect of polymeric additives, adjuvant and surfactants for their ability to support growth, shelf-life stability and bio-efficacy of liquid bioinoculants (Bacillus megaterium var. phosphaticum, Azospirilum brasilense and Azotobacter chrococcum). Liquid inoculants formulated with 2% polyvinylpyrollidone (PVP 30 K), 0.1% carboxy methylcellulose (CMC-high density) and 0.025% Polysorbate 20 promoted long-term survival of Bacillus megaterium var. phosphaticum, Azospirillum and Azotobacter with 5.6 x 107, 1.9x108 and 3.5x107 cfu ml-1, respectively after 480 days of formulation when stored at 30oC.

Effects of Polymeric Additives on the Crystallization and Release Behavior of Amorphous Ibuprofen

Some polymeric additives were studied to understand their effects on the amorphous phase of ibuprofen (IBU), used as a poorly water soluble pharmaceutical model compound. The amorphous IBU in bulk, as well as in nanopores (diameter ~24 nm) of anodic aluminum oxide, was examined with the addition of poly(acrylic acid), poly(N-vinyl pyrrolidone), or poly(4-vinylphenol). Results of bulk crystallization showed that they were effective in limiting the crystal growth, while the nucleation of the crystalline phase in contact with water was nearly instantaneous in all cases. Poly(N-vinyl pyrrolidone), the most effective additive, was in specific interaction with IBU, as revealed by IR spectroscopy. The addition of the polymers was combined with the nanoscopic confinement to further stabilize the amorphous phase. Still, the IBU with addition of polymeric additives showed sustained release behavior. The current study suggested that the inhibition of the crystal nucleation was probably the most important factor to stabilize the amorphous phase and fully harness its high solubility.

Effect of polymeric additives on the formation and properties of polyaniline films on polyester fabrics

Electrically conductive films based on polyaniline (PANI) and polyethylene glycol (PEG) molecules of different chain length were synthesized on polyester textiles (PET) through in situ polymerization. Fabric supports were placed in the monomer bath in the presence of polymeric additive firstly and then immersed into the oxidant solution to initiate the reaction. Influence of the PEG segment length on monomer adsorption process toward fabrics was investigated by comparing the adsorption thermodynamic parameters. The polymeric layers’ morphologies have been evaluated using the field emission scanning electron microscope, and the film formation mechanism has been investigated. Compositions of the films synthesized in the absence and presence of PEG were characterized by attenuated total reflection Fourier transform infrared. The electrical resistance measurement results indicated that the electrical conductivity of PET/PANI–PEG composite fabrics decreases slowly as the PEG segments length increased, and the thermal stability was improved slightly according to thermogravimetric analysis values.

Using polymeric additives to enhance molecular gelation: impact of poly(acrylic acid) on pyridine-based gelators

The effect of polymeric additives on molecular gelation was explored using poly(acrylic acid) and pyridine-based gelators. A significant reduction in the critical gel concentration (cgc) and an increase in gel strength were observed when the polymer was present during gel formation. Detailed studies revealed that the polymer is adsorbing onto the growing fibers, reducing the growth rates, and leading to thinner fibers. These and other morphological changes lead to improved gel properties by increasing the number of fiber–fiber entanglements. Several other polymers were briefly examined and these studies revealed that polymer structure is important. The polymer containing a complementary functional group relative to the gelator (e.g., H-bond donor/acceptor) provided the lowest cgc.

Effects of some polymeric additives on the cocrystallization of caffeine

Effects of polymeric additives on the model cocrystallization were examined. The model cocrystal was made from caffeine and oxalic acid, and poly(ethylene glycol) (PEG), poly( l-lactide) (PLLA), poly(ε-caprolactone) (PCL), and poly(acrylic acid) (PAA) were the additives. The cocrystals were formed as millimeter-sized crystals without additives, and they became microcrystals with PLLA and PCL, and nanocrystals with PAA. XRD and IR revealed that the cocrystal structure was unchanged despite the strong effects of the additives on the crystal morphology, although some decrease in crystallinity was observed with PAA as confirmed by DSC. The DSC study also showed that the cocrystal melted and recrystallized to form α-caffeine upon heating. The present study verified that the polymeric additives can be utilized to modulate the size and morphology of the cocrystals without interfering the intermolecular interactions essential to the integrity of the cocrystal structures.

The effect of polymeric additives on the solubilisation of a poorly-soluble drug in micellar solutions of Pluronic F127

The solubilisation of griseofulvin in 1 wt% aqueous micellar solutions of Pluronic F127 at 37 °C has been modified by adding polyethylene glycol PEG 35000 or poly(vinylpyrrolidone) PVP K30. The solubilisation capacity expressed in terms of unit weight of F127 is increased by the addition of 0.5 wt% PEG 35000 to a value approaching double that of a 2.5 wt% solution of F127 alone, but there is no advantage in adding 0.5 wt% PVP K30.

The Effect of Polymeric Additives on TSV Filling by Copper Electroplating

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Thickener performance traced by multisample analytical centrifugation

Polymeric thickeners are important ingredients to adjust flow properties and stability of formulations. The effect of polymeric additives on dispersion properties is rather complex (viscosity of the continuous phase, adsorption and depletion effects, interaction with other ingredients). Therefore optimum formulation requires extensive experimental investigations. A new multisample approach is presented using analytical centrifugation (STEP-Technology), which allows for an accelerated characterisation of separation stability. The potential of multisample analytical centrifugation for formulation design was demonstrated investigating the effect of particle (calcium carbonate, silica) and polymer (polyacryl amide) concentration on dispersion properties of different stabilised suspensions. The quality of dispersion – flocculated or stable dispersion – can be judged based on shape and evolution of the transmission profiles or by comparison of the speed of separation. Accordingly the optimum concentration for stabilisation of lime dispersions by an anionic surfactant was identified. Stability of the surfactant stabilised lime dispersions can be markedly enhanced by low concentrations of polymeric thickener. Effect of addition of non-adsorbing thickener with high molecular mass very sensibly depends on concentration (integral effect of depletion and increasing viscosity). For the quartz dispersion investigated stabilisation at low polymer concentration by viscosity effect, followed by destabilisation at intermediate concentration due to depletion flocculation and stabilisation at higher concentration by viscosity, eventually by depletion stabilisation was experienced. In summary analytical centrifugation can be successfully used for screening purposes in dispersion product development. Different samples can be directly compared in short time.

Electric Birefringence of Electrolytes near Charged Surfaces, II: Effect of Polymeric Additives

Electric birefringence of electrolytes containing linear polyacrylamide and polyethylene oxide near a negatively charged silica glass surface is studied using evanescent wave laser polarimetry. We find that addition of polymers to electrolytes near charged surfaces leads to substantially larger levels of electric birefringence than the already anomalously large electric birefringence observed in pure electrolytes near charged surfaces. The polymer contribution to the birefringence increases with surface charge, ionic strength of the electrolyte, and electric field, but is only a weak function of polymer molecular weight and polymer concentration. Unusually high levels of polymer orientation are observed for moderate electric fields (10-30 V/cm). These observations are discussed in terms of large local shear gradients experienced by polymer chains subject to electro-osmotic flow in the electric double layer near charged surfaces.

Effect of Polymeric Additives on Calcium Carbonate Crystallization as Monitored by Nephelometry

The effect of polymaleimide polymers on calcium carbonate crystallization was studied using nephelometry. Induction time and percent growth inhibition were determined for polymeric additives from the nephelometric data. The polymaleimide synthesized by KOH-initiated polymerization exhibited the greatest growth inhibition and longest nucleation time among the polymers investigated. Raman spectroscopy was used to determine the calcium carbonate polymorph formed in the presence of these polymeric additives.

Effect of polymeric additives on the structure and permeability of poly(vinyl alcohol) asymmetric membranes : Chuang, W.-Y., Young, T.-H., Chiu, W.-Y., Lin, C.-Y., National Taiwan University, Taipei, Taiwan in polymer, vol 41, issue 15, 2000

Effect of polymeric additives on the structure and permeability of poly(vinyl alcohol) asymmetric membranes : Chuang, W.-Y., Young, T.-H., Chiu, W.-Y., Lin, C.-Y., National Taiwan University, Taipei, Taiwan in polymer, vol 41, issue 15, 2000

Effect of polymeric additives on properties of glass–bisphenol A dicyanate laminate composites

The polycyanurate network matrix derived from the thermal, dibutyl tin dilaurate catalyzed polymerization of bisphenol A dicyanate was modified in their glass–laminate composites with different linear polymeric additives bearing pendant phenol, cyanate, and epoxy functions. The mechanical properties and fracture energy for delamination of the glass–laminate composites were estimated as functions of the backbone structure and concentration of the various additives. The effect of altering the nature or concentration of the functional group for a given backbone structure of the additive was examined in some cases. Except for the epoxy functional acrylic polymer, all other systems adversely affected the fracture energy for delamination of the composites due to either plasticization or embrittlement of the matrix. With the exception of the styrene-hydroxyphenyl maleimide (SPM) copolymer, the other modifiers impaired the mechanical properties and adversely affected the thermomechanical profile of the composites. In the cases of the phenol functional acrylic polymer and its cyanate derivative, plasticization of the matrix by the partly phase-separated additive, which eased the fiber debonding, appears to be responsible for the impairment of the mechanical properties. The high glass transition temperature SPM copolymer enhanced the resin–reinforcement interaction through dipolar interactions induced by the hydroxyl groups, which resulted in amelioration of the mechanical properties. However, its possible coreaction and formation of a brittle, homogeneous phase with the polycyanurate was conducive for poor damage tolerance. The SEM analysis of the fractured composites showed that in the elastomers fiber debonding is the major cause for delamination. Although the presence of SPM led to a stronger interphase, failure occurred either in the brittle matrix or through fiber breakage. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 75–88, 2000

Effect of polymeric additives on properties of glass-bisphenol A dicyanate laminate composites

The polycyanurate network matrix derived from the thermal, dibutyl tin dilaurate catalyzed polymerization of bisphenol A dicyanate was modified in their glass–laminate composites with different linear polymeric additives bearing pendant phenol, cyanate, and epoxy functions. The mechanical properties and fracture energy for delamination of the glass–laminate composites were estimated as functions of the backbone structure and concentration of the various additives. The effect of altering the nature or concentration of the functional group for a given backbone structure of the additive was examined in some cases. Except for the epoxy functional acrylic polymer, all other systems adversely affected the fracture energy for delamination of the composites due to either plasticization or embrittlement of the matrix. With the exception of the styrene-hydroxyphenyl maleimide (SPM) copolymer, the other modifiers impaired the mechanical properties and adversely affected the thermomechanical profile of the composites. In the cases of the phenol functional acrylic polymer and its cyanate derivative, plasticization of the matrix by the partly phase-separated additive, which eased the fiber debonding, appears to be responsible for the impairment of the mechanical properties. The high glass transition temperature SPM copolymer enhanced the resin–reinforcement interaction through dipolar interactions induced by the hydroxyl groups, which resulted in amelioration of the mechanical properties. However, its possible coreaction and formation of a brittle, homogeneous phase with the polycyanurate was conducive for poor damage tolerance. The SEM analysis of the fractured composites showed that in the elastomers fiber debonding is the major cause for delamination. Although the presence of SPM led to a stronger interphase, failure occurred either in the brittle matrix or through fiber breakage. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 75–88, 2000

The effect of polymeric additives on the structure and permeability of poly(vinyl alcohol) asymmetric membranes

The manufacture and dextran-rejection properties of asymmetric poly(vinyl alcohol) (PVA) membranes have been described in this study. Membranes were prepared from a casting solution of PVA, water as solvent, and water-soluble polymeric additive by immersing them in Na 2SO 4/KOH/H 2O as coagulant medium. Experiments showed that the dextran and poly(vinyl pyrrolidone) (PVP) additives exerted a different influence on the structure and permeability of membranes. Especially, the structure of skin layer strongly depended on the polymeric additives in the casting solution. The addition of dextran additives in the system could induce pores in the top layer. Conversely, the PVP additives effectively blocked the interstitial cavities within the top layer to generate a more compact structure. A mechanism describing that the affinity between additive and casting solution as well as between additive and coagulant medium was proposed to investigate the effect of dextran and PVP additives in the formation of PVA membranes. The results presented here offer a better understanding of relationships between the membrane formation mechanism and the skin structure when designing an asymmetric membrane by the addition of polymeric additives in the casting solution.