Effect Of Polymer Content Research Articles

Formation of inhalable rifampicin-poly(L-lactide) microparticles by supercritical anti-solvent process.

Formation of inhalable microparticles containing rifampicin and poly(L-lactide) (L-PLA) by using supercritical anti-solvent process (SAS) was investigated. The solutions of drug and polymer in methylene chloride were sprayed into supercritical carbon dioxide. The effect of polymer content and operating conditions, temperature, pressure, carbon dioxide molar fraction, and concentration of solution, on product characteristics were studied. The prepared microparticles were characterized with respect to their morphology, particle size and size distribution, drug content, drug loading efficiency, and drug release characteristic. Discrete, spherical microparticles were obtained at high polymer:drug ratios of 7:3, 8:2, and 9:1. The shape of L-PLA microparticles became more irregular and agglomerated with decreasing polymer content. Microparticles with polymer content higher than 60% exhibited volumetric mean diameter less than 5 microm, but percent drug loading efficiency was relatively low. Drug-loaded microparticles containing 70% and 80% L-PLA showed a sustainable drug release property without initial burst release. Operating temperature level influenced on mean size and size distribution of microparticles. The operating pressure and carbon dioxide molar fraction in the range investigated were unlikely to have an effect on microparticle formation. An increasing concentration of feed solution provided larger size microparticles. Rifampicin-loaded L-PLA microparticles could be produced by SAS in a size range suitable for dry powder inhaler formulation.

Investigation on PVDF-HFP microporous membranes prepared by TIPS process and their application as polymer electrolytes for lithium ion batteries

Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) microporous membranes were prepared via thermally induced phase separation (TIPS) process. Then they were immersed in a liquid electrolyte to form polymer electrolytes. The effects of polymer content in casting solution on the morphology, crystallinity, and porosity of the membranes were studied by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and a mercury porosimeter, respectively. Ionic conductivity, lithium-ion transference number, and electrochemical stability window of corresponding polymer electrolytes were characterized by AC impedance spectroscopy, DC polarization/AC impedance combination method, and linear sweep voltammetry, respectively. The results showed that spherulites and “net-shaped” structure coexisted for the membranes. Polymer content had no effect on crystal structure of the membranes. The maximum transference number was 0.55. The temperature dependence of ionic conductivity followed the Vogel–Tammann–Fulcher (VTF) relation. The maximum ionic conductivity was 2.93 × 10−3 Scm−1 at 20 °C. Electrochemical stability window was stable up to 4.7 V (vs. Li+/Li).

Novel amino acid modified zinc polycarboxylates for improved dental cements

The objective of this study was to develop a novel amino acid modified zinc/calcium polycarboxylate cement system, formulate the cements, and evaluate their mechanical strengths. Acrylate and methacrylate derivatives of four amino acids were synthesized and characterized using FT-IR and 1HNMR spectroscopy. The derivatives were formulated with polymer having pendent methacrylate group, water, and synthesized novel filler. Compressive (CS) as well as flexural strengths (FS) and viscosities of the resin liquids were used as tools to evaluate the formulations and formed cements. The specimens for CS and FS tests were conditioned in distilled water at 37 degrees C for 24 h and 7 d, respectively, prior to testing. The measured CS and FS of the cements was in the decreasing order of methacryloyl beta-alanine > acryloyl glutamic acid = acryloyl beta-alanine > methacryloyl glutamic acid > 2-hydroxyethyl methacrylate. Methacryloyl beta-alanine was selected for further formulations due to its relatively low solution viscosity and high CS as well as FS. Effects of polymer content, P/L ratio, tartaric acid and initiator concentration were significant. During aging, the cement showed a constant increase in CS for up to 1 month and then kept constant for up to 3 months. This study developed a novel amino acid modified zinc/calcium polycarboxylate cement system. This system was 85% higher in CS, 98% higher in DTS and 183% higher in FS, compared to Durelon.

Fixed-bed biosorption of Cu2+by polyacrylonitrile-immobilized dead cells of Saccharomyces cerevisiae

Dead cells of Saccharomyces cerevisiae 54 were immobilized by entrappment in polyacrylonitrile. The beads obtained were used to adsorb copper in an up-flow fixed-bed column. The effect of polymer content and cell loading were studied to optimize the porosity and the efficiency in copper removal of the biosorbent beads in a batch system. The optimal concentration of the polyacrylonitrile was assumed to be 12%(w/v) and a concentration of 0.5 g cell dry weight in 1 g polymer was most effective in adsorption of Cu2+. The adsorption capacity of this biosorbent was 27 mg Cu2+/g dry biomass at 200 mg/l initial concentration of copper ions. Adsorption of Cu2+ in a batch system was studied using different initial concentrations of the solute. The optimal conditions in the up-flow column of the following parameters were determined: flow rate, bed height, and initial concentration of Cu2+ of the solutions. Results of fixed-bed biosorption showed that breakthrough and saturation time appeared to increase with the bed height, but decrease with the flow rate and the initial concentration. The linearized form of the Thomas equation was used to describe dynamic adsorption of metal ions. As a result, the adsorption capacity of the batch system and the column system was compared. Desorption of copper ions was achieved by washing the column biomass with 0.1 M HCl at an eluent flow rate of 1 ml/min. The reusability of the immobilized biomass was tested in five consecutive adsorption-desorption cycles. The regenerated beads retained over 45% of their original adsorption capacity after five A/D cycles.

An amino acid-modified and non-HEMA containing glass-ionomer cement

It is known that unreacted 2-hydroxyethyl methacrylate (HEMA) in current resin modified glass ionomer cements (RMGICs) shows potential cytotoxicity to pulp and surrounding tissues. Elimination of HEMA could make RMGICs more attractive for dental applications. In this research, novel six acrylate and methacrylate derivatives of amino acids were synthesized, characterized and used for replace HEMA in RMGICs. The experimental RMGICs were formulated with vinyl-containing polymer, amino acid derivative, water, and commercial Fuji II LC glass. Among all the derivatives, methacryloyl beta-alanine (MBA) was selected for further formulations due to its relatively low solution viscosity and high CS. Effects of polymer content and powder/liquid, P/ L, ratio were significant. The formulation with liquid composition of 50/25/25 (polymer/MBA/water) and P/ L ratio of 2.7/1 was found the optimal. It appears that this novel non-HEMA-containing RMGIC system based on amino acid derivatives will be a better dental restorative because it demonstrated improved mechanical strengths and may eliminate potential cytotoxicity in current RMGICs caused by leached HEMA. The optimal MBA-modified GIC were 20% higher in CS, 70% higher in DTS and 93% higher in FS, compared to Fuji II LC.

Effect of polymer content and molecular weight on the morphology and heat- and moisture-induced transformations of spray-dried composite particles of amorphous lactose and poly(vinylpyrrolidone).

The aim was to investigate the influence of polymer content and molecular weight on the morphology and heat- and moisture-induced transformations, as indicators of stability, of spray-dried composite particles of amorphous lactose and poly(vinylpyrrolidone) (PVP). Amorphous lactose and composite particles of amorphous lactose with different contents and molecular weights of PVP were prepared by spray drying. The nanostructure of the particles was analyzed by x-ray powder diffractometry, the morphology by light microscopy and SEM, the glass transition temperatures (Tg), crystallization temperatures (Tc), heats of crystallization and melting temperatures by differential scanning calorimetry, and moisture-induced crystallizations gravimetrically and by microcalorimetry. All the types of particles prepared were amorphous. The Tg was unchanged or only marginally increased as a result of the inclusion of PVP. However, crystallization temperature, time to moisture-induced crystallization, and particle morphology were affected by both content and molecular weight of PVP. Increased content and molecular weight of PVP may have the potential to increase the physical stability of amorphous lactose. However, Tg seems not to be a relevant indicator for the stability of this type of amorphous composite materials.

Selection of spinneret for modacrylic fibre Part II Effect of polymer content

Selection of spinneret for modacrylic fibre Part II Effect of polymer content

Compressive Behavior of Glass‐Fiber Reinforced Polymer Concrete

The effect of polymer content and glassfiber content on the compressive behavior of polyester polymer concrete is investigated at room temperature. The polymer content varies between 10% and 18% of...