Polyisobutylene Concentration Research Articles

Enhanced the swelling resistance of polyamide membranes with reinforced concrete structure

Preparation of novel swelling resistance membrane by interpenetrating an immiscible flexible polyisobutylene (PIB) polymer into a rigid polyamide (PA) network by interfacial polymerization. Due to the force interlocking of flexible PIB, polyamide network has high strength and excellent resistance to methanol. The PA layer was characterized by mechanical strength, attenuated total reflection fourier transforms infrared spectroscopy (ATR-FTIR), small angle X-ray scattering (SAXS), contact angle, field emission scanning electron microscope (FE-SEM) and atomic force microscope (AFM). RO membrane performances were evaluated based on small molecule alcohol (methanol and ethanol) solution of Safranin O. The results show that the flexible PIB interpenetrates well in the rigid polyamide network and improves mechanical strength and swelling resistance. With an increasing concentration of PIB from 0% to 0.30% in the organic phase during the fabrication, the mechanical strength of the PA layer becomes 2.8 times that of the original, and the rejection of Safranin O increased from 95.43% to 99.43%, and the permeability coefficient (Bs) decreased from 5.22 to 0.47.

Novel high boron removal polyamide reverse osmosis membranes

Novel high boron removal thin film composite (TFC) membranes with semi-interpenetrating networks were fabricated by interfacial polymerization (IP) with m-phenylenediamine (MPD) and 1,3,5-benzenetricarbonyl trichloride (TMC). The polyisobutylene (PIB) was added to the organic phase prior to IP. The membranes were characterized by attenuated total reflectance Fourier transform infrared spectrometry (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM) and the zeta potential and contact angle analysis. The results of this study demonstrate that the novel TFC membrane exhibited superior separation performance at a relatively low concentration of PIB (0.30%, m/v). As the concentration of the interpenetrating PIB in the membrane increased, the membrane morphology changed distinctly. Furthermore, the permeability coefficient of boron decreased from 20.84 to 3.26, and the rejection of boron increased from 81.36% to 93.12%.

Shapes of dispersed phase in confined PIB/PDMS blends with different compositions during shear flow

The morphology of immiscible fluid mixtures under confined environment usually displays different scenarios compared with those presented in bulk systems. In this work, the influence of confinement and component ratio on the droplet morphology of immiscible polyisobutylene (PIB)/polydimethylsiloxane (PDMS) blends in confined steady shear flow was investigated. While increasing the degree of confinement, the morphology of dispersed phase experienced a transition from the bulk behavior toward the confined behavior. Increasing the concentration of PIB phases in confined blends resulted in more coarsened structure under low shear rate and generated pearl necklace or string-like structures under a higher shear rate. The maximum aspect ratio of PIB droplets increased while increasing PIB concentration. The width and the aspect ratio of PIB droplets obtained experimentally were compared to the predictions of a single droplet MM model for bulk flow and an M model considering confinement. The experimental droplet width agreed well with the predictions of these two models only in the small droplet zone, large deviations appeared for the degree of confinement up to 0.36 and higher, whereas constant droplet width was found. The M model decreased the deviation between the experimental aspect ratio and the prediction of MM model in the high Ca zone. Good agreement between the prediction of M model and experiment results was found when the orientation angles of the droplets were corrected by using the M model.

The Effect of Vinyl Acetate Content and Polyisobutylene Concentration on the Properties of Metallocene Polyethylene-Ethyl Vinyl Acetate Coextruded Film for Stretch and Cling Film Applications

A range of EVA-mLLDPE-EVA coextruded films, with polyisobutylene (PIB) masterbatch content of 0-20% and vinyl acetate (VA) comonomer content of 6, 12, and 18%, is manufactured. The films are aged at 45 C for up to 28 days to enable tack (cling) development. The results show that film tack strength improves significantly with aging. Increased VA concentration in the surface layer also shows significant improvement in film tack strength. The film tensile strength, elongation, and tear properties in both machine direction (MD) and transverse direction (TD) are not significantly affected by increase in PIB concentration. Increased VA content shows slight improvement in MD mechanical performance of the films, although TD properties are relatively unaffected.

The Characteristics of Polyethylene Film for Stretch and Cling Film Applications

AbstractPart I. A range of polyethylene films were prepared from metallocene linear low density polyethylene (m‐LLDPE), linear low density polyethylene (LLDPE) and ultra low density polyethylene (ULDPE) resins, containing 0 and 8% polyisobutylene (PIB). FTIR, DSC and mechanical analysis techniques were used to investigate the effect of co‐monomer type, density and melt flow index (MFI) on the mechanical performance, orientation and crystallinity of these films. The study established that co‐monomer type and MFI were the greatest factors influencing mechanical performance and crystallinity. Crystallinity was found to be the most influential factor governing PIB migration in these films and this in turn was related to polymer type, density and MFI, High MFI, octene co‐monomer films exhibited the highest orientation, tear resistance and tack strength and would therefore be suitable for stretch film applications. Ultra low‐density polymers gave relatively low tack strength and poor overall mechanical performance.Part II. A range of ethyl vinyl acetate (EVA)/m‐LLDPE/EVA co‐extruded films was manufactured, with vinyl acetate (VA) co‐monomer content of 6, 12 and 18% and PIB content from 0–20%. The films were aged at 45d̀C for up to 28 days, to enable tack (cling) development. The results show that film tack strength improved significantly with ageing. Increased VA concentration in the surface layer also showed significant improvement in film tack strength. The film tensile strength, elongation and tear properties in both machine direction (MD) and transverse direction (TD) were not significantly affected by increase in PIB concentration. However, increased VA content showed slight improvement in MD mechanical performance of the films, TD properties were relatively unaffected. Films with 12 to 18% VA in the surface layers produced high surface tack film and the mechanical performance of these films were comparable to mono‐layer polyethylenes. These films are suitable for stretch wrap applications and have reduced the overall concentrations of tack additives, though high VA films were more difficult to process.

The Manufacture and Performance of Polyethylene‐Polyisobutylene Films for Cling Applications

AbstractA range of Linear Low Density Polyethylene (LLDPE) films with polyisobutylene (PIB) content from 2%‐8% was manufactured using a Killion blown film extrusion system and a cast film extrusion system. The films were aged at 25°, 35° and 45° for up 28 days, to enable tack (cling) development. The tack, in both blown and cast films, improved significantly with ageing, at increased storage temperatures and at higher film blow up ratios. FTIR/ATR analysis was used to investigate the surface migration of PIB in the cast films. The results confirmed those determined by mechanical tack (cling) analysis. DSC analysis showed only a slight decrease in film crystallinity with increasing PIB concentration. The film tensile modulus, elongation and tear properties in both MD and TD were not significantly affected by increase in PIB concentration.A second series of films with 8% PIB content was manufactured from a range of LLDPE'S. FTIR/ATR, DSC and mechanical tack analysis were used to investigate the relationship between polymer properties and migration rates. The study established that crystallinity was the most influential factor governing PIB migration and this could be related to polymer density. Co‐monomer type was found not to be a factor influencing migration of PIB.

The Effect of Extrusion Processing Conditions and Polyisobutylene Concentration on the Properties of Polyethylene for Stretch and Cling Film Applications

A range of LLDPE films with polyisobutylene (PIB) content from 2-8% was manufactured using a Killion blown film extrusion system and a cast film extrusion system. The films were aged at 25, 35 and 45 C for up to 28 days, to enable tack (cling) development. The results show that tack, in both blown and cast films, improved significantly with ageing at increased storage temperatures and at higher film blow up ratios. DSC analysis showed only a slight decrease in film crystallinity with increasing PIB concentration. The film tensile modulus, elongation and tear properties in both MD and TD were not significantly affected by an increase in PIB concentration.

Rod-Climbing characterization of kaolinite suspended polyisobutylene solutions

The rod-climbing constants of kaolinite-suspended polyisobutylene (PIB) solutions are investigated from rod-climbing experiments. For a low deformation rate, this particle suspended polymer solution can be regarded as a second-order fluid, and the rod-climbing constant for such fluids is correlated with the rheological properties of the particle-suspended polymer solutions. The rod-climbing constants for kaolinite suspended PIB solutions were found to decrease with temperature and increase with PIB concentration, molecular weight of PIB, solvent viscosity, and particle concentration. The rheological properties were measured using rotational rheometer, and the shear viscosity and the first normal stress difference of the kaolinite suspended PIB solution show the Boger-fluid characteristics.

Effect of microcapsule size and polyisobutylene concentration on the release of theophylline from ethylcellulose microcapsules.

Ethylcellulose microcapsules containing theophylline were prepared by the phase-separation coacervation process induced by non-solvent addition in the presence of variable amounts of polyisobutylene. No statistical difference was evident between the different sized microcapsules with respect to their drug content, wall thickness and in-vitro drug dissolution profiles. Poly-isobutylene was, however, found to influence the release profiles of drug to a great extent. An increase in polyisoburylene concentration retarded the release of theophylline from the microcapsules due to the formation of smaller and spheroidal coacervate droplets in larger volumes, which resulted in the formation of more evenly coated microcapsules. Although the release of theophylline from the microcapsules was found to fit both the first order and diffusion controlled release processes, differential rate treatment indicated that the overall release, in fact, was governed by diffusion controlled process.

Rheological characterization of the time and strain dependence for polyisobutylene solutions

The rheological response of polyisobutylene (PIB) solutions in Decalin and a related standard fluid S1 has been characterized in dynamic oscillatory flow, step strain, step-shear rate and steady shear using a Rheometrics RDSII rheometer. The time dependence represented as a discrete spectrum of relaxation times and the strain dependence characterized as an exponential damping function have been presented as a function of PIB concentration. The relaxation spectrum was calculated from the dynamic storage modulus and loss modulus. The damping function was determined from the non-linear relaxation modulus in a step-strain experiment. The Wagner integral viscoelastic model incorporated with the relaxation and the damping function has been used to predict the stress growth and the steady-shear behaviour, which were compared with the experimental data. A novel extensional rheotester was also used in this study to measure the stretching response of polymer solutions. The data gave a near single relaxation time for each solution, and this single relaxation time obtained from uniaxial extension was correlated to the relaxation spectrum obtained in simple shear.

Influence of polyisobutylene on microencapsulation of metronidazole

Metronidazole was microencapsulated with ethylcellulose by a phase separation method to develop a sustained release dosage form. Polyisobutylene (PIB) was used as a protective colloïd to control the particule size and the drug release of the microcapsules. The influence of PIB on microcapsules charateristics depends on the core-wall ratio, the molecular weight of PIB and the concentration of PIB.

Polyacrylate resin (Eudragit retard) microcapsules as a controlled release drug delivery system-improved non-solvent addition phase separation process.

Eudragit retard microcapsules were prepared using an improved non-solvent addition phase separation process with tetrahydrofuran as the solvent. The evolution of microcapsule wall formation was studied by direct methodology. Eudragit coacervation was effected by progressive uptake of tetrahydrofuran by the non-solvent cyclohexane in the presence of a protective colloid, polyisobutylene (PIB). The core materials had a higher affinity for the acrylic that the PIB phase, thus ensuring encapsulation. Microcapsule batch reproducibility depended mainly on the variation in particle size distribution of the recrystallized core material. All batches gave apparent first-order release profiles, confirmed by regression procedures. The release rate was decreased by raising the wall/core ratio, holding constant concentration of either the wall polymer or the core material. Increase in the non-solvent addition rate elevated the release rate, probably due to structural changes in the microcapsule wall. The velocity fell, however, with decrease in particle size of the core material, contrary to expectations. PIB concentration increase elevated the release rate by enhancing wall porosity, shown by scanning electron microscopy.

Drug Release Properties of the Microcapsules of Adriamycin Hydrochloride with Ethylcellulose Prepared by a Phase Separation Technique

AbstractAdriamycin hydrochloride was microencapsulated with ethylcellulose by a phase separation method to develop a prolonged release dosage form. Polyisobutylene (PIB) was used as a coacervation-inducing agent to control the particle size and drug release rate of the resultant microcapsules. With increasing the concentration of PIB (1 to 3 %) the average diameter of the microcapsules decreased, due to the fact that the microcapsules were discreted to a single microcapsule. At low concentration of PIB, the resultant microcapsules were agglomerated, which resulted in increasing the size. The microcapsules prepared with PIB 2 % prolonged desirably the drug release from the microcapsules. A little size effects of the microcapsules on the drug release rate was found for the microcapsules with PIB 2 % and 3 %.

Coacervation of ethyl cellulose: The role of polyisobutylene and the effect of its concentration

The influence of polyisobutylene (PIB) on the phase separation of ethyl cellulose (EC) from cyclohexane by temperature reduction was studied by measurement of the phase coacervation volume (PCV) and particle size and by SEM examination of the coacervate obtained. PIB concentration effects on phase properties were delineated by means of a phase diagram. In the absence of PIB or at low concentrations, EC aggregates were formed whereas higher concentrations yielded stabilized droplets. Microanalysis indicated that PIB was not coprecipitated and hence functions as a stabilizer by adsorption. Increased PIB concentration raised the PCV and decreased the particle size in nonlinear dependence. The PCV change resulted from Stokes law sedimentation kinetic effects. MW increase of PIB at constant solution viscosity increased the PCV and decreased the particle size, indicative of increased stabilization. There was a negative linear dependence of diameter on medium viscosity. It was concluded that increase of viscosity and protective colloid concentration modulated the rates of the EC separation, growth, and aggregation processes and led to stabilization of droplets at an earlier stage of growth and suppression of regular surface nucleation and crystallization of the polymer.