Monomer Flow Rate Research Articles

Synthesis and characterization of stretchable isoprene-acrylic acid copolymer thin films

Copolymer thin films of isoprene with acrylic acid were synthesized using PECVD. In that way, the stretchable functionality of polyisoprene (PI) was combined with the hydrophilic functionality of poly(acrylic acid) (PAA) to obtain stretchable thin films with adjustable wettabilities. Deposition rates were found to change between 9 and 5.5 nm/min depending on the monomer flowrates. The analysis of water contact angle (WCA) values indicated that films having more AA units in their structures were more wettable. The stretchability of the films was assessed on laboratory gloves through stretch-release test and on PET sheet through bend-release test. No significant changes in the WCA values with no observable cracks and failures after successive tests were indication of stretchability of the copolymer films.

Chemical constitution of coatings deposited remotely by activation of hexamethyldisiloxane in positive column plasma of glow discharge in argon flow

The present work deals with the chemical constitution of coatings deposited by plasma activation of hexamethyldisiloxane in positive column plasma of a low-pressure DC glow discharge in an argon flow (mass flow rate 230 mg/min). X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR) are used to analyze deposit chemistry. The substance is complex and consists of many constitutional units forming branched and cross-linked irregular macromolecules. Chemical constitution depends on both discharge current (10–60 mA) and monomer flow rate (1–10 mg/min). Using the specific energy (SE) and Arrhenius-like approach, the threshold energy for the plasma polymerization of HMDSO has been estimated to be 12 ± 1 eV. Two regimes of the plasma chemical system have been identified. At SE near the threshold energy (from 5 to 40 eV/molecule), polymethylsiloxane-like coatings are deposited and variation of SE practically does not lead to changes in chemical constitution, but significantly affects the mass yield of deposit. At specific energies much higher than threshold energy, polymethylhydroxysiloxane-like coatings are formed; the coating structure is strongly SE-dependent, while the mass yield of the deposit does not change.

Degradable Plasma-Polymerized Poly(Ethylene Glycol)-Like Coating as a Matrix for Food-Packaging Applications.

Currently, there is considerable interest in seeking an environmentally friendly technique that is neither thermally nor organic solvent-dependent for producing advanced polymer films for food-packaging applications. Among different approaches, plasma polymerization is a promising method that can deposit biodegradable coatings on top of polymer films. In this study, an atmospheric-pressure aerosol-assisted plasma deposition method was employed to develop a poly(ethylene glycol) (PEG)-like coating, which can act as a potential matrix for antimicrobial agents, by envisioning controlled-release food-packaging applications. Different plasma operating parameters, including the input power, monomer flow rate, and gap between the edge of the plasma head and substrate, were optimized to produce a PEG-like coating with a desirable water stability level and that can be biodegradable. The findings revealed that increased distance between the plasma head and substrate intensified gas-phase nucleation and diluted the active plasma species, which in turn led to the formation of a non-conformal rough coating. Conversely, at short plasma-substrate distances, smooth conformal coatings were obtained. Furthermore, at low input powers (<250 W), the chemical structure of the precursor was mostly preserved with a high retention of C-O functional groups due to limited monomer fragmentation. At the same time, these coatings exhibit low stability in water, which could be attributed to their low cross-linking degree. Increasing the power to 350 W resulted in the loss of the PEG-like chemical structure, which is due to the enhanced monomer fragmentation at high power. Nevertheless, owing to the enhanced cross-linking degree, these coatings were more stable in water. Finally, it could be concluded that a moderate input power (250-300 W) should be applied to obtain an acceptable tradeoff between the coating stability and PEG resemblance.

The investigation of deposited organic carbon‐silicon films using cyclonic atmospheric pressure plasma polymerization

AbstractBackgroundThe upgrading of atmospheric‐pressure plasma polymerization process, the detailed investigation of atmospheric‐pressure plasma polymerization deposited organic carbon‐silicon film features is essential to obtain the further understandings into the optimizing coating techniques.AimThis investigation demonstrates plasma cyclone deposited film features with adjusting argon gas flow rate and HMDSN monomer flow rate.MethodThis study utilized the plasma cyclone system to polymerize a carbon‐silicon film. In this study, Optical Emission Spectroscopy (OES) was employed as a diagnostic tool to indirectly inspect the chemical composition of the atmospheric‐pressure plasma polymerization's glow discharge by detecting the photo‐emitting species. The Contact Angle Goniometer, ATR‐FTIR, AFM, and XPS were used to measure the surface properties of the films deposited by plasma cyclone.ResultsThe static contact angle results show that most of the deposited films obtain the divergent contact angle values with adjusting argon gas flow rate and HMDSN monomer flow rate. ATR‐FTIR results show that argon gas flow rate and HMDSN monomer flow rate dominate the porosity of plasma cyclone deposited film surface. XPS and AFM analyses also detect the comparable trend of physicochemical characteristics of organic carbon‐silicon film with adjusting argon gas flow rate and HMDSN monomer flow rate. In summary, the organic carbon‐silicon films can be successfully polymerized by plasma cyclone.ConclusionsThe results refer that the organic carbon‐silicon film deposition on vanadium redox flow battery separator surface improved the electrolyte uptake of the cyclonic‐plasma‐coated separators was larger than that of a commercial separator.

Branched nozzle oblique angle flow for initiated chemical vapor deposition

Monomer precursor flow was introduced at an oblique angle to the substrate at two locations during the initiated chemical vapor deposition (iCVD) process using a branched nozzle inlet extension. The polymerization of methacrylic acid was systematically studied as a function of the nozzle length and the monomer flow rate. Our experimental data showed the evolution of two distinct symmetrical thickness profiles as the flow rate and nozzle length increased. The maximum thickness moved downstream along the axes of both nozzles as the flow rate and nozzle length increased. Computational models were used to study the effects of the nozzle length and the monomer flow rate on the velocity profile within the reactor. Increasing the monomer flow rate and the nozzle length resulted in increases in the velocity profile ranges and the movement of the location of the maximum velocity and local minimum velocity associated with the stagnation point. These velocity data provided insight for explaining the trends found in the experimental results. The data demonstrate the ability to use a branched nozzle inlet extension to control the location of polymer deposition during the iCVD process.

Low-density polyethylene simulated production in high pressure tubular reactor

The importance of the LDPE polymerization process has spawned a slew of LDPE tubular reactor modelling and simulation projects. Through adjusting input parameters, the sensitivity study of input parameters in an industrial low density polyethylene tube reactor was addressed in this paper. This work's innovation was highlighted with the incorporation of the LDPE melt flow index in the reactor output. The highest temperature peak and monomer conversion were obtained when initiator concentration were increased by 1.06 factor, whereas the highest melt flow index was obtained when the inlet temperature was increased by 1.07 factor. The monomer flow rate, initiator flow rate, and solvent flow rate all had a substantial impact on the LDPE process performance in a tubular reactor.

Sensitivity study of input parameters in the industrial low density polyethylene tubular reactor

Low-density polyethylene (LDPE) is one of the most widely used polymers in the world, and is produced in either tubular or autoclave reactors. As the LDPE industry turn into more competitive and its profit margins become tighter, manufacturers have to develop solutions to debottleneck the reactor output while abiding to the stringent product specification. As such, optimization offer the best option for reactor debottlenecking approach. However, since the LDPE polymerization in a tubular rector is an intrinsic nonlinear process, certain parameters need to be studied before it can be assigned as optimized variables in the optimization study. If these parameters are not properly identified, the optimization study might result in extra complicated sets of unresolvable solutions. Therefore, a model sensitivity study needs to be carried out to identify the most significant parameters that affect the performance of LDPE process in tubular reactor. An LDPE tubular reactor model was developed and validated with industrial data prior to the sensitivity study. Coefficient of determination (R2) equivalent to 0.991 and 0.989 were obtained for the reactor temperature and the monomer conversion profiles, respectively. The comparison of the product properties at the reactor end also showed a satisfactory agreement where a low percentage of error in the range of 0 to 0.39% was obtained. Based on the sensitivity studies, monomer flow rate, initiator flow rate and solvent flow rate were identified to give significant effect to the performance of LDPE process in tubular reactor. Improvement in product quality measurement and kinetic rate constant parameters were highlighted as the novelty of the present study.

Pulsed plasma surface modified omeprazole microparticles for delayed release application

In the present work, pulsed radio frequency (RF) plasma (PRFP) was used to functionalize omeprazole (OME) microparticles using precursor monomers methacrylic acid (MAA) and methyl methacrylate (MMA). This method had two significant factors involved – 1) ratio of monomer flow rate and 2) graded deposition by systematically varying the duty cycle of pulsed plasma. The MAA flow was set to 100 cc/min and MMA to 200 cc/min to rationalize the ratio (1:2) of monomers. Systematic variation in duty cycle (keeping ON time constant and increasing OFF time of the pulse) ensured graded deposition and functionalization of OME. The plasma functionalized OME microparticles were evaluated in-vitro via dissolution studies in pH 1.2 buffer showed a cumulative release of 3.6–9.1% within 120 min compared to complete release under 60 min in pH 6.8. Raman analysis exhibited the absence of peaks from 1800 to 1000 cm−1 and XPS studies showed an increase in oxygen-containing moieties on plasma functionalized OME surface. Thermal, NMR and HR-MS analysis confirmed successful deposition without alteration in original OME molecular structure. The decreased contact angle of post plasma treated OME resulted from hydrophilization of the OME surface. XRD data of plasma treated OME showed an improved degree of crystallinity with an increase in average crystallite size. Post plasma treated OME microparticles size through DLS corroborated well with SEM. Thus, the use of graded PRFP functionalization has proved it's potent to deliver a new, safe, and cheaper alternative to contemporary drug surface modification methods.

Atmospheric Pressure Plasma Polymerized 2-Ethyl-2-oxazoline Based Thin Films for Biomedical Purposes.

Polyoxazoline thin coatings were deposited on glass substrates using atmospheric pressure plasma polymerization from 2-ethyl-2-oxazoline vapours. The plasma polymerization was performed in dielectric barrier discharge burning in nitrogen at atmospheric pressure. The thin films stable in aqueous environments were obtained at the deposition with increased substrate temperature, which was changed from 20 C to 150 C. The thin film deposited samples were highly active against both S. aureus and E. coli strains in general. The chemical composition of polyoxazoline films was studied by FTIR and XPS, the mechanical properties of films were studied by depth sensing indentation technique and by scratch tests. The film surface properties were studied by AFM and by surface energy measurement. After tuning the deposition parameters (i.e., monomer flow rate and substrate temperature), stable films, which resist bacterial biofilm formation and have cell-repellent properties, were achieved. Such antibiofouling polyoxazoline thin films can have many potential biomedical applications.

Oblique angle initiated chemical vapor deposition for patterning film growth

Initiated chemical vapor deposition (iCVD) can be used to deposit thin polymer films on a variety of substrates. In this work, the monomer precursor was introduced at an oblique angle to the substrate using an inlet extension, and the pattern of the resulting polymer film was studied as a function of deposition time, substrate temperature, monomer flow rate, reactor pressure, and vapor flow angle. The polymerizations of n-butyl acrylate, methacrylic acid, and 2-hydroxyethyl methacrylate were examined to determine the generality of the trends across several monomers. It was found that the monomer flow rate significantly affected the pattern of the deposited polymer by shifting the location of the thickest point in the films. Increasing the deposition time, decreasing the substrate temperature, and increasing the reactor pressure all increased the polymer deposition rate consistent with conventional iCVD; however, the pattern of the deposited polymer did not vary with these parameters. Computational analysis was used to determine how the inlet extension affects the pressure and velocity profiles within the reactor. The data demonstrate that the introduction of a monomer precursor at an oblique angle can be used to pattern polymer films during iCVD.

Atmospheric Pressure Microwave Plasma Jet for Organic Thin Film Deposition.

In this work, the potential of a microwave (MW)-induced atmospheric pressure plasma jet (APPJ) in film deposition of styrene and methyl methacrylate (MMA) precursors is investigated. Plasma properties during the deposition and resultant coating characteristics are studied. Optical emission spectroscopy (OES) results indicate a higher degree of monomer dissociation in the APPJ with increasing power and a carrier gas flow rate of up to 250 standard cubic centimeters per minute (sccm). Computational fluid dynamic (CFD) simulations demonstrate non-uniform monomer distribution near the substrate and the dependency of the deposition area on the monomer-containing gas flow rate. A non-homogeneous surface morphology and topography of the deposited coatings is also observed using atomic force microscopy (AFM) and SEM. Coating chemical analysis and wettability are studied by XPS and water contact angle (WCA), respectively. A lower monomer flow rate was found to result in a higher C–O/C–C ratio and a higher wettability of the deposited coatings.

A Model to Study the Effect of Monomer Flow Rate on Methyl Methacrylate Emulsion Polymerization in a Seeded Semi-Batch Reactor

A Model to Study the Effect of Monomer Flow Rate on Methyl Methacrylate Emulsion Polymerization in a Seeded Semi-Batch Reactor

Dynamic optimization of an emulsion copolymerization process for product quality using a deterministic kinetic model with embedded Monte Carlo simulations

We present the dynamic optimization of an emulsion copolymerization process described by a deterministic kinetic ordinary differential equation model including a stochastic Monte Carlo submodel, describing the growth of polymer chains within particles. For the considered semi-batch operation, the time dependent input trajectories for monomer and initiator flow rates are optimized along with the isothermal reactor temperature. We use the surrogate-model-based optimizer MATSuMoTo for the optimization to avoid the need to compute derivatives of the stochastic model. Radial basis functions with linear polynomial tails are selected as surrogate functions which are updated during optimization by the newly evaluated points. A relevant application problem formulation together with results for two case studies are presented. Qualitatively similar input trajectories are obtained for different optimization runs due to the stochastic process and the limited number of iterations. All solutions reduce the batch time significantly.

Development of phosphor containing functional coatings via cold atmospheric pressure plasma jet - Study of various operating parameters

Abstract In this study, we deposited phosphorous containing functional coatings on the surface of polypropylene (PP) substrate by cold atmospheric plasma assisted polymerization using low temperature plasma jet. Triisopropyl phosphate (TIP) was used as precursor while the coating process was carried out as a function of deposition potential and monomer flow rate. The influence of various plasma polymerization operating parameters on the surface properties of functional coatings are examined by means of atomic force microscopy (AFM), Scanning electron microscopy (SEM) and X-ray photo electron spectroscopy (XPS). The reactive species involved during the in-situ polymerization were studied by optical emission spectroscopy (OES). The variation in hydrophilic properties of the surface coated film was investigated by measuring contact angle. Furthermore, the stability of post-plasma polymerized films was evaluated by measuring contact angle values 15 days after storing in various ambient conditions (air and distilled water). The characterization results clearly exhibited that phosphorus containing functional films could be successfully deposited on the surface of PP films and the retention of the functional groups could be tuned within the framework of the operating parameters.

Online Shape Modification of Molecular Weight Distribution Based on the Principle of Active Disturbance Rejection Controller

Molecular weight distribution (MWD), an important microcosmic quality index of high polymer, is online unmeasurable, which makes its closed-loop control extremely difficult. To solve this problem, an online shape modification strategy for polymer MWD is proposed based on the active disturbance rejection controller (ADRC). The temporal-spatial property of MWD is estimated in real time by a three-layers forward network based on orthogonal polynomials basis function, and the shape modification of distribution function is transformed into the tracking control of moment statistics in the state-space description. Taking full advantage of the online measured lower-order moments, dual ADRCs are constructed with two manipulated variables (the flow rate of monomer and initiator) to achieve the high precision tracking of lower-order moments and distribution functions, simultaneously. Furthermore, the stability condition of the closed loop system is proved which can guide the parameter tuning of ADRCs. The proposed control strategy is implemented on the polymerization reaction in the laboratory scale continuous stirred tank reactor (CSTR). The feasibility and robustness are verified in the simulation.

Kinetic Selection of Template Polymer with Complex Sequences.

The emergence and maintenance of polymers with complex sequences pose a major question in the study of the origin of life. To answer this, we study a model polymerization reaction, where polymers are synthesized by stepwise ligation from two types of monomers, catalyzed by a long polymer as a template. Direct stochastic simulation and dynamical systems analysis reveal that the most dominant polymer sequence in a population successively changes, depending on the flow rate of monomers to the system, with more complex sequences selected at a lower flow rate. We discuss the relevance of this kinetic sequence selection through nonequilibrium flow to the origin of complex polymers.

Plasma Modification and Synthesis of Membrane Materials-A Mechanistic Review.

Although commercial membranes are well established materials for water desalination and wastewater treatment, modification on commercial membranes is still necessary to deliver high-performance with enhanced flux and/or selectivity and fouling resistance. A modification method with plasma techniques has been extensively applied for high-performance membrane production. The paper presents a mechanistic review on the impact of plasma gas and polymerization, at either low pressure or atmospheric pressure on the material properties and performance of the modified membranes. At first, plasma conditions at low-pressure such as plasma power, gas or monomer flow rate, reactor pressure, and treatment duration which affect the chemical structure, surface hydrophilicity, morphology, as well as performance of the membranes have been discussed. The underlying mechanisms of plasma gas and polymerization have been highlighted. Thereafter, the recent research in plasma techniques toward membrane modification at atmospheric environment has been critically evaluated. The research focuses of future plasma-related membrane modification, and fabrication studies have been predicted to closely relate with the implementation of the atmospheric-pressure processes at the large-scale.

Influence of operating parameters on development of polyethylene oxide-like coatings on the surfaces of polypropylene films by atmospheric pressure cold plasma jet-assisted polymerization to enhance their antifouling properties

In this study, we investigated the deposition of a polyethylene oxide (PEO)-like coating on the surfaces of polypropylene (PP) films via atmospheric pressure cold plasma jet-assisted polymerization using ethylene glycol dimethyl ether as a precursor. The PEO-like coatings were deposited using different operating parameters (deposition potential and monomer flow rates) and we determined their effects on the film properties, such as the topography, surface chemistry, and surface free energy, based on atomic force microscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and contact angle measurements. The interfacial tension between various biological liquids and the PEO-like film surfaces were studied in detail. The antifouling properties of the PEO-like films were examined in vitro, including protein adsorption and platelet adhesion. The results showed that the retention of the PEO-like character and the formation of new functional groups were highly dependent on the operating parameters. Significant changes in the film topography and wettability were obtained by further regulating the plasma operating parameters. All of the PEO-like films had good antifouling properties according to the in vitro analysis results.

A stability study of plasma polymerized acrylic acid films

A medium pressure parallel-plate DBD set-up was used for the deposition of carboxylic acid-rich films using acrylic acid as precursor. A variety of discharge powers (21–33W) and monomer flow rates (0.25–0.5g/h) were applied to develop a range of coatings from highly unstable to completely stable in aqueous solutions. FT-IR and XPS were used to identify which coatings were stable under dynamic incubation conditions and what influence plasma operating parameters had on functional group preservation. White light interferometry was also used to calculate deposition rates (66–126nm/min) and to determine the deposition regime (monomer deficient). Human foreskin fibroblasts were seeded onto the complete range of investigated samples and the effects of coating (in)stability on cell adhesion, viability and morphology were systematically studied. Results showed that the 27 W-0.25g/h treatment conditions resulted in the most stable coatings. Although a concentration of only 0.7% of carboxylic acid groups was found under these experimental conditions, the positive effects of a highly acid-rich surface were still maintained as cell-material interactions were significantly enhanced.

Automatic Synthesis of Multimodal Polymers

An automatic molecular weight controller is used in semi‐batch reactions to produce final polymers that contain distinct subpopulations with different molecular weight distributions (MWD). While blending polymers with different MWD is frequently used to make multimodal polymer products, a method is introduced here allowing the multimodal product to be made in successive, automatically controlled stages in the same reactor. The method is demonstrated using free radical polymerization of acrylamide to produce widely separated multimodal MWD. Automatic Continuous Online Monitoring of Polymerization reactions with a Control Interface (ACOMP/CI) was used. Weight average molecular weight (Mw) in the ACOMP/CI was continuously measured with multi‐angle light scattering and ultra‐violet absorption. The controller used two principles: both polymerization rate and instantaneous molecular weight are proportional to monomer concentration. By controlling monomer flow rate into the reactor, the controller produced a targeted amount of polymer with a desired first Mw and then automatically introduced chain transfer agent (CTA) into the reactor to produce a second population of polymers with much lower Mw. Subsequently, reactions were performed to produce trimodal populations. This approach is kindred to multi‐stage synthesis of polymers where distinctly different processes are carried out in succeeding stages to produce polymers with highly specific properties. image