Poly Vinyl Methyl Research Articles

Application of hydrophilic macromolecules on thin film composite polyamide membranes for performance restoration

Polymeric “rejection enhancing agents” (REAs) were shown to form rather durable coatings, on flat sheet polyamide membranes, thereby sealing defects for improved salt rejection performance. Dilute solutions of three REAs, i.e. Polyvinyl methyl ether (PVME), polyvinyl pyrrolidone (PVP) and polyvinyl alcohol (PVA), followed by tannic acid, were tested on two types of low-pressure reverse osmosis membranes. PVA and PVP have a significant advantage over PVME, as they do not exhibit cloud point limitations at elevated feed-water temperatures. Treatment in dead-end mode of an unused membrane (A), with REAs concentrations 5 ppm to 30 ppm, led to significant rejection improvement and guided subsequent experiments. Emphasis was placed on performance restoration of a used degraded membrane (B2). In dead-end and cross-flow tests with this membrane, there was significant rejection improvement, with a modest concurrent flux reduction; best results were obtained with REAs applied at concentration 10 ppm and pressure 1034 kPa (150 psi), over a 30 min period. Additionally, when the initial salt rejection of a membrane sample was low (possibly due to active layer degradation) the treatment resulted in the greatest rejection improvement. Successful online treatment with REAs in a cross-flow experimental system, without interrupting normal operation, suggests that the process is attractive for practical applications.

Electrochemical behavior of different shelled microcapsule composite copper coatings

Copper/liquid microcapsule composite coatings with polyvinyl alcohol (PVA), gelatin or methyl cellulose (MC) as shell materials were prepared by electrodeposition. The influence of shell materials on the corrosion resistance of the composite coatings in 0.1 M H2SO4 was investigated by means of electrochemical techniques, scanning electron microscopy (SEM), and energy dispersion spectrometry (EDS). The results show that the participation of microcapsules can enhance the corrosion resistance of the composite coatings compared with the traditional copper layer. Based on the analysis of electrochemical test results, the release ways of microcapsules were deduced. Gelatin and MC as the shell materials of microcapsules are easy to release quickly in the composite coating. On the contrary, the releasing speed of PVA microcapsules is relatively slow due to their characteristics.

Preparation, Physical-Chemical Characterization, and Cytocompatibility of Polymeric Calcium Phosphate Cements

Aim. Physicochemical mechanical and in vitro biological properties of novel formulations of polymeric calcium phosphate cements (CPCs) were investigated. Methods. Monocalcium phosphate, calcium oxide, and synthetic hydroxyapatite were combined with either modified polyacrylic acid, light activated polyalkenoic acid, or polymethyl vinyl ether maleic acid to obtain Types I, II, and III CPCs. Setting time, compressive and diametral strength of CPCs was compared with zinc polycarboxylate cement (control). Specimens were characterized using X-ray diffraction, scanning electron microscopy, and infrared spectroscopy. In vitro cytotoxicity of CPCs and control was assessed. Results. X-ray diffraction analysis showed hydroxyapatite, monetite, and brushite. Acid-base reaction was confirmed by the appearance of stretching peaks in IR spectra of set cements. SEM revealed rod-like crystals and platy crystals. Setting time of cements was 5–12 min. Type III showed significantly higher strength values compared to control. Type III yielded high biocompatibility. Conclusions. Type III CPCs show promise for dental applications.

Effectiveness of Three Different Toothpaste Formulations in Reduction of Plaque and Gingivitis: A Comparative Clinical Study

ABSTRACT The role of dental plaque in gingivitis and periodontitis is well established. It is commonly observed that daily brushing often fails to achieve and maintain optimum gingival health. In order to improve the efficacy of the self-performed mechanical tooth cleaning procedure, antimicrobial substances like chlorhexidine, metallic ions, fluorides and various phenolic compounds have been evaluated, as such adjuvants in clinical trials that have been added to dentifrice used during tooth brushing. Triclosan (2, 4, 4' trichloro-2'hydroxyphenylether) is a nonionic antibacterial agent with broad spectrum activity against both gram-positive and gram-negative organisms. Recently, triclosan was introduced in toothpaste and mouth rinses for control of plaque and gingivitis. However, maximum antiplaque activity is shown when triclosan is used in combination with agents like copolymer polyvinyl methyl ether maleic acid (PVM/MA). The PVM/MA copolymer retains the triclosan on the soft and hard surfaces of the oral cavity for several hours. This study aims in proving efficacy of triclosan copolymer toothpaste over the triclosan alone and non-triclosan toothpaste in reduction of plaque and gingivitis.

Effects of dentin tubule occlusion by dentifrice containing a PVM/MA bioadhesive copolymer in a silica base

Objective To study the effectiveness of a dentifrice containing polymethyl vinyl ether-maleic acid (PVM/MA) copolymer in a silica base in occluding dentin tubules for treatment of dentin sensitivity. Methods Thirty-two human dentin discs were divided into two groups and brushed in the morning for 30 s each to study the dentifrices with and without PVM/MA copolymer. Dentin tubule occlusion and dentin permeability were evaluated with a focus variation three dimensional vertical scanning microscope (IFM) and electrochemical impedance spectroscopy (EIS). After second brushing for 30 s in the afternoon the dentin discs were immersed in saliva for 16 h and then subjected to erosion using orange juice for 10 min. The effects of saliva and orange juice on tubule occlusion used in the study of dentifrices were further evaluated with IFM. Results On average 97.7% of the dentin tubules were occluded after brushing in the PVM/MA group, as compared to 13.3% in the control group ( p < 0.0001). EIS showed that the impedance of the dentin disc increased after treatment with PVM/MA but not in the control group ( p < 0.05). After 16 h of storage in saliva and 10 min of erosion by orange juice, 86% of the dentin tubules remained occluded in the PVM/MA treated dentifrice. The sizes of the tubule openings were increased after orange juice erosion in the control group but not in the PVM/MA group. Conclusion Dentifrice containing PVM/MA copolymer in a silica base effectively occluded dentin tubules. The intra-tubular plugs were resistant to saliva and orange juice challenges.

SHELL MATERIAL'S PERFORMANCE OF THE MICROCAPSULE FOR ELECTROLYTIC CO-DEPOSITION

The shell material of microcapsules has an important effect on the electrolytic co-deposition behavior, the release of core material and the surface performance of composite coating. This paper discussed the tensile property and the stability of three shell materials including polyvinyl alcohol (PVA), gelatin and methyl cellulose (MC). It is found that these three shell materials have good mechanical strength and flexibility which are favorable to electrolytic co-deposition and stability of microcapsules in composite coating and that MC has well permeability and porosity which has a positive effect on the release of the core material in composite coating. Moreover, the study of the thermal properties and water vapor permeability of the three shell materials showed that their permeability improved with increase of temperature and humidity. In addition, the composite copper coating containing microcapsules with PVA, gelatin or MC as shell material was prepared respectively.

Cytotoxicity, calcium release, and pH changes generated by novel calcium phosphate cement formulations

Few published studies describe the biological properties of calcium phosphate cements (CPCs) for dental applications. We measured several biologically relevant properties of 3 CPCs over an extended (8 wk) interval. Monocalcium phosphate, calcium oxide, and synthetic hydroxyapatite were combined with either modified polyacrylic acid, light-activated modified polyalkenoic acid, or 35% w/w polymethyl vinyl ether maleic acid to obtain Types I, II, and III CPCs, respectively. Set cements were placed in direct contact with L929 fibroblasts for up to 8 weeks. Media Ca(+2) and pH were determined by atomic absorption spectroscopy and pH electrode respectively. Cell mitochondrial function was measured by MTT assay. Type I cements suppressed mitochondrial activity > 90% (vs. Teflon controls), but significantly (p < 0.05) improved to control levels over 8 weeks. Type II cements suppressed mitochondrial activity > 90% at all times. Type III cements elevated mitochondrial activity significantly after 7 wks. The pH profiles approached neutrality by 24 h, and all cements released calcium into the storage medium at all periods (24 h - 8 wk). We concluded that several types of cements had long-term biological profiles that show promise for dental applications.

Reverse Osmosis Membrane Treatment Improves Salt-Rejection Performance

This study systematically investigated applying rejection-enhancing agents (REAs) that can plug or seal defects on flat-sheet polyamide (PA) membrane surfaces to improve salt rejection with minimum flux reduction. Polyvinyl methyl ether (PVME) and tannic acid (TA) were used as REAs on low-pressure reverse osmosis (LPRO) membranes. Treatment of an unused LPRO membrane (membrane A) with REAs in the range of 10–30 ppm PVME followed by 10–30 ppm TA significantly improved membrane salt-rejection performance with a concomitant flux reduction less than 20 percent. However, similar treatment of another new membrane (membrane B1), which exhibited good initial salt-rejection performance, did not produce any further improvements. A used membrane B2 was also treated with PVME and TA and showed significant salt-rejection improvement with modest flux reduction. In addition, when the initial salt rejection of a sample from this membrane was relatively small, possibly due to severe degradation, the coating application resulted in significant salt-rejection improvement. Successful testing with injecting REAs online, without interrupting pilot plant operation, suggests that the process is attractive for practical applications. Recommendations are provided for implementing the process in RO desalination plants.

Polymeric-Calcium Phosphate Cement Composites-Material Properties:In VitroandIn VivoInvestigations

New polymeric calcium phosphate cement composites (CPCs) were developed. Cement powder consisting of 60 wt% tetracalcium phosphate, 30 wt% dicalcium phosphate dihydrate, and 10 wt% tricalcium phosphate was combined with either 35% w/w poly methyl vinyl ether maleic acid or polyacrylic acid to obtain CPC-1 and CPC-2. The setting time and compressive and diametral tensile strength of the CPCs were evaluated and compared with that of a commercial hydroxyapatite cement. In vitro cytotoxicity and in vivo biocompatibility of the two CPCs and hydroxyapatite cement were assessed. The setting time of the cements was 5–15 min. CPC-1 and CPC-2 showed significantly higher compressive and diametral strength values compared to hydroxyapatite cement. CPC-1 and CPC-2 were equivalent to Teflon controls after 1 week. CPC-1, CPC-2, and hydroxyapatite cement elicited a moderate to intense inflammatory reaction at 7 days which decreased over time. CPC-1 and CPC-2 show promise for orthopedic applications.

Comparative study of biocompatibility of newly developed calcium phosphate‐based root canal sealers on fibroblasts derived from primary human gingiva and a mouse L929 cell line

To determine biocompatibility of three calcium phosphate cement (CPC) sealers, and to compare the cytotoxic response of human gingival fibroblasts (HGF) and one mouse fibroblast cell line (L929) to these materials. Monocalcium phosphate, calcium oxide and synthetic hydroxyapatite were combined with one of three aqueous solutions: modified polyacrylic acid, glass-ionomer liquid or 35% w/w polymethyl vinyl ether maleic acid to obtain Types I, IIa and III CPCs, respectively. Commercial Ca(OH)(2) sealer was used as a control. The materials were packed into Teflon molds (5.5 x 3 mm), and cellular function was assessed using MTT assay. The specimens were placed immediately in contact with cells, then evaluated at (24 h, 1 week, 2 week, 3 week, 4 week, 5 week). All materials showed significant cytotoxicity for both L929 and HGF cells at 24 h except for Type III. Type I was severely toxic initially, but improved significantly (P < 0.05) over the 5 week evaluation. Types II and Ca(OH)(2) were both cytotoxic over the 5 weeks. Type III CPC was equivalent to Teflon the entire time. The results showed the same rank of cytotoxicity in both cultures. The cytotoxic response decreased in the order of Type II > Ca(OH)(2) > Type I > Type III overtime. L929 cells were generally more sensitive than HGF cells to the calcium hydroxide-based sealer (Acroseal). Types I and III have acceptable biologic properties for endodontic applications.

Surfactant effects in the mechanical activation of ultrafine alumina powders made by pneumocirculation grinding

Studies have been made on the effects of mechanochemical activation with the addition of surfactants on the characteristics of the pneumocirculation grinding product from alumina powder and the properties of the corundum ceramic based on it. Processing the powder in an aqueous solution of polyvinyl alcohol and methyl cellulose with concentration up to 1% has a marked effect on the detailed crystal structure of the particles and improves the technological properties of the powder. Activation produces defects at the particle surfaces, which tend to intensify the consolidation of the powder up to high sintering temperatures.

Phase Structure of PVC/MBS Blends by Small Angle X-ray Scattering

The phase structure of blends consisting of polyvinyl chloride (PVC) and methyl methacrylate—butadiene—styrene graft copolymer (MBS) are examined by small-angle-X-ray scattering (SAXS). The interface layer thickness (σ), correlation distance (ac), and interface layer specific surface area (Ssp) are calculated using Debye—Bueche's statistical theory. The results show that the grafted sequence of styrene or methyl methacrylate to butadiene—styrene copolymer have significant influence on the values of σ, ac, and Ssp. The σ-value of PVC/MBS in which styrene is first grafted in MBS is about 5 nm larger than that of methyl methacrylate (MMA) that is first grafted in MBS.

Fabrication of Porous Alumina Ceramics from a Technique for Making a Cake

We fabricated porous alumina ceramics from a technique for making a cake. Polyvinyl alcohol (PVA), methyl cellulose (MC), and granulated sugar (SUGAR) were used as additives to give the alumina slurry the foaming property and the foam stability. The alumina slurry with PVA, MC, and SUGAR became creamy by mixing for 2.5 min by an electric mixer at 940 rpm. The creamy alumina slurry was able to be extruded by a forcing bag and smoothed by a blade. The creamy alumina slurry dried at 45°C, and then was sintered at 1600°C to a density of about 20%. The pore sizes in the sintered porous alumina ceramics were 0.2 mm or less. The flexural strength of sintered porous alumina ceramics with 78% porosity was 12 MPa.

X‐ray photoelectron and carbon Kα emission measurements and calculations of O‐, CO‐, N‐, and S‐containing substances

AbstractX‐ray fluorescence measurements for O‐containing [polyethylene oxide, polyvinyl alcohol, polyvinyl methyl ether], CO‐containing [polyvinyl methyl ketone, polyethylene terephthalate], N‐containing [poly‐4‐vinylpyridine (P4VP), polyaniline oligomer (PAO)], and S‐containing [polyphenylene sulfide] substances are presented. Carbon Kα X‐ray emission spectra (XES) and X‐ray photoelectron spectra (XPS) are compared with our DFT calculations performed with the Amsterdam density functional (ADF) program. The combined analysis of valence XPS and carbon Kα XES allows us to determine the individual contributions from pσ‐ and pπ‐bonding molecular orbitals of the polymers. The ΔSCF calculations yield the accurate C1s core‐electron binding energies (CEBEs) for all carbon sites of the organic compound. We calculate all CEBEs of the model molecules using the ΔEKS approach. Our simulated C1s photoelectron and C Kα emission spectra are in good agreement with our measurements. We also obtain WD (work function and the other energies) values for the polymers and PAO from the difference between calculated (gas‐phase) and measured (solid) CEBE values. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 162–172, 2007

Thermally-Activated Non-Reversible Response of Polystyrene/ Polyvinyl Methyl Ether (PS/PVME) Sandwich Sample Under Small-Amplitude Oscillatory Shear Flow

Small amplitude oscillatory shear modulus was measured for a sandwich type assembly made of polystyrene (PS) and polyvinyl methyl ether (PVME) as a function of time at constant temperature and as a function of temperature at constant frequency. Diffusion coefficient in the miscible region was obtained from the time sweep experiments. The obtained mutual diffusion coefficient was found to be in agreement with the value determined using attenuated total reflection-infrared spectroscopy measurements. A peculiar non-reversible behavior was observed when the sandwich sample was heated and cooled between 40 and 160°C. Such a behavior was associated with the difference in kinetics between phase segregation and phase homogenization of the PS/PVME blend.

The effect of a polyhexamethylene biguanide mouthrinse compared with a triclosan rinse and a chlorhexidine rinse on bacterial counts and 4‐day plaque re‐growth

For various clinical applications, polyhexamethylene biguanide hydrochloride (PHMB) has been used for many years as an antiseptic in medicine. Recently, a 0.04% and a 0.12% PHMB mouthwash were shown to inhibit plaque re-growth and to reduce oral bacterial counts. In this study, a 0.2% PHMB mouthrinse (A) was compared with a positive control 0.12% aqueous chlorhexidine solution (B), a commercially available 0.3% triclosan/2.0% polyvinyl methyl ether maleic acid copolymer mouthrinse (Colgate Total Plax) (C), and a negative control placebo rinse (10% ethanol, flavour) (D). The controlled clinical study was a double blind, randomized, four replicate cross - over design. Plaque re-growth was assessed with the Turesky et al. (1970) modification of the Quigley & Hein (1962) plaque index. The antibacterial effect was assessed by taking bacterial counts on the tooth surface (smears from the buccal surface of 16/26) and mucosa (smears from the buccal mucosa in opposite of area 16/26) after the professional prophylaxis and after the first rinse with the preparations on day 1 and prior to the clinical examination on day 5. Sixteen volunteers participated and, on day 1 of each study period were rendered plaque-free, ceased toothcleaning, and rinsed twice daily with the allocated mouthrinse. On day 5, plaque was scored and smears were collected according to the protocol. A 10-day wash-out period was carried out between each rinse evaluation. Data were analysed using ancova with Bonferroni HSD adjustment for multiple comparisons (colony forming units per sample) with a significance level alpha=0.05. The 0.2% PHMB mouthrinse (A) was significantly better at inhibiting plaque than the placebo (D), but significant less effective than the 0.12% aqueous chlorhexidine solution (B). There is no significant difference between A and the 0.3% triclosan/2.0% copolymer mouthrinse (C). Bacterial count reductions (tooth surface and mucosa) with PHMB (A) were significantly greater compared with the placebo (D) and triclosan (C), but significantly lower compared with chlorhexidine (B) (tooth surface) and equally effective compared with chlorhexidine (B) (mucosa). Consistent with previous studies, a PHMB mouthrinse was shown to inhibit plaque re-growth and to reduce oral bacterial counts, indicating that PHMB could be an alternative to established mouthrinses in preventive applications.

O10 The technology behind Colgate® TotalTM toothpaste

In the early 1990s, a break‐through toothpaste, known as Colgate® Total™, was launched with documented long‐lasting activity against plaque, gingivitis, calculus, tooth decay and bad breath. The technology behind this toothpaste is the combination of triclosan, a polyvinyl methyl ether maleic acid (PVM/MA) copolymer and sodium fluoride (TCF). The function of the copolymer is to ensure optimal oral retention and prolonged release of the antibacterial triclosan. Effective levels of triclosan have been measured in the oral cavity 12 h after brushing the teeth. This allows prolonged control of oral bacteria that can lead to the formation of dental plaque and gingivitis and bad breath. Similarly, the retention of triclosan to oral surfaces during 2 years regular use of the product has led to a significant reduction in incremental coronal caries compared to an ADA‐approved anti‐cavity fluoride toothpaste. Furthermore, significantly less calcium phosphate has been shown to be present in dental plaque after brushing the teeth with the triclosan/copolymer toothpaste, and this has resulted in the reduced formation of tartar. A new variant of the triclosan/copolymer/fluoride toothpaste, having the numerous therapeutic and aesthetic benefits of the original formula, has been made available to consumers. The new dentifrice, which contains an impactful breath freshening flavor, has been documented to be significantly better (P &lt; 0.05) than a control toothpaste in providing sustained control of bad breath over 12 h. After 12 h, breath odor was reduced from 51% compared to the control. The long term retention and subsequent release of triclosan by the copolymer in the TCF formula provide consumers protection against plaque, gingivitis, tartar, caries and bad breath.

Alkyl (C10, C12, C14 and C16) triphenyl phosphonium bromide influenced cloud points of nonionic surfactants (Triton X 100, Brij 56 and Brij 97) and the polymer (Polyvinyl methyl ether)

The clouding points (CP) of the nonionic surfactants p-tert-octyl phenyl polyoxyethylene ether (Triton X 100), Brij-56 and Brij-97, and the water soluble polymer polyvinylmethylether (PVME) have been measured in the presence of the ionic surfactants alkyl (C10, C12, C14 and C16) triphenyl phosphonium bromides (ATPBs). The threshold additive concentrations required for efficient CP enhancement of the systems that were studied have been determined. Considering CP as the threshold state of phase separation, the energetics of the process at different additive concentrations has been evaluated. The spontaneity of free energy of the clouding process (ΔG c 0 ) at the transition concentrations followed the order PVME > TX 100 ≈ Bj 56 > Bj 97. The clouding process has been found to be energetically endothermic with fairly large enthalpy and entropy changes that nicely compensate each other. The compensation temperature has been evaluated and compared with different types of the clouding agents.

Properties of Some Chitosan-containing Blends and Films Therefrom

Mixed solutions of chitosan and polymers with different chain rigidities (polyvinyl alcohol and methyl cellulose) in 2% acetic acid, at various component ratios, were studied viscometrically. The compatibility of the components in solutions and in the solid phase was assessed, and the mechanical characteristics of films prepared from these blends were determined.

Effect of shear flow on the phase‐separation behavior in a blend of polystyrene and polyvinyl methyl ether

AbstractThe phase behavior and phase‐separation dynamics of polystyrene/polyvinyl methyl ether (PS/PVME) blend with a critical composition of 70 vol % PVME were examined with a light scattering technique under a shear‐rate range of 0.1–40 s−1. If the shear rates were less than 8 s−1 and the starting temperatures of the measurement were 343 and 383 K, respectively, two cloud points were observed, whereas after the shear rate was higher than 8 s−1, only one cloud point existed, 20 K higher than that of the static state of the blend. Investigation of the phase‐separation dynamics at 443 K suggested that in the vorticity direction the phase‐separation behavior at the early stage and the later stage can be explained by Cahn–Hilliard linearized theory and the exponent growth law, respectively. Phase separation occurs after a shearing time, which was called a delay time τd. The delayed time τd, the apparent diffusion coefficient, and the exponent term of the blend show strong dependence on shear rates. A theoretical prediction of the phase behavior of PS/PVME under a shear flow field by introducing an elastic energy term into Flory's equation‐of‐state theory was made, and the prediction was consistent with the experimental results. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 661–669, 2003