The miscibility and phase behavior of polyethylene with poly(dimethylsiloxane) in near-critical pentane

Miscibility and phase behavior of solutions of polyethylene (PE) and poly(dimethylsiloxane) (PDMS) mixtures in near-critical n-pentane have been investigated in a special variable-volume view-cell equipped with a computerized data acquisition system. This is a study on dissolving mutually incompatible polymers in a common solvent at high pressures. The fluid-fluid and fluid-solid demixing pressures of the solutions were determined for different polymer concentrations (5% PE, 5% PE+1% PDMS, 5% PE+2% PDMS and 5% PE+5% PDMS). In the PE+n-pentane solutions, the system shows LCST (lower critical solution temperature) type behavior and the fluid-fluid demixing pressures increase with increasing temperature. The PE+PDMS+n-pentane systems, however, show UCST (upper critical solution temperature) type behavior and the fluid-fluid demixing pressures decrease with increasing temperature. Even with small addition of PDMS to PE, the demixing pressures show dramatic increases compared to the demixing pressures of PE alone. At high PDMS concentrations (5% PDMS), complete miscibility could not be achieved at pressures up to 70 MPa. The fluid-solid boundary that is associated with the melting or crystallization of PE was also studied as a function of cooling and heating rates. It is shown that these temperatures tend to approach the same value in the limit of very low heating and cooling rates.     

Adhesion promotion of thick fire-retardant melamine polymer dip-coatings at polyolefin surfaces by using plasma polymers

Melamine and melamine resins are widely used as fire retardants for polymer materials used in pharmaceutical, plastic, textile, rubber, and construction industry. Melamine-based flame retardants act by blowing off intumescent layers, char formation, and emission of quenching ammonia gas and diluent molecular nitrogen. Special advantages are: low cost, low smoke density and toxicity, low corrosive activity, safe handling, and environmental friendliness. Methylated poly(melamine-co-formaldehyde) (mPMF) was used as thick (≥40?μm) fire-retardant coating for plasma pretreated polymers. A combined low-pressure plasma pretreatment consisting of oxygen plasma exposure followed by deposition of thin poly(allylamine) (ppAAm) and poly(allyl alcohol) (ppAAl) plasma polymers as adhesion promoters have improved the adhesion of thick mPMF coatings strongly. Chemical structure and composition of deposited polymer films were characterized by infrared-attenuated total reflectance and X-ray photoelectron spectroscopy (XPS). After peeling, the peeled layer surfaces were also investigated for identification of the locus of failure and their topography using optical microscopy and XPS. Often the adhesion promotion was so efficient that the peeling of coating was not possible. Thermal properties of plasma polymers and dip-coating films were analyzed by thermogravimetric analysis. Significant improvement of fire-retardant properties of coated polymers was confirmed by flame tests.     

Cured melamine systems as thick fire-retardant layers deposited by combination of plasma technology and dip-coating

Melamine and melamine resins are widely used as fire-retardants for polymer building materials. Cured melamine systems are used in heat-sensitive items, such as furniture and window frames and sills. In this work, differently cured methylated poly(melamine-co-formaldehyde) (cmPMF) resins were used as fire-retardant coverage for poly(styrene) (PS) and poly(ethylene) (PE) building materials. Such polymer layers should have several tenths of micrometers thickness to produce sufficient fire retardancy. These thick layers were produced by dip-coating. To promote sufficient adhesion of such thick coating to the polyolefin substrates, also in the case of high temperatures occurring at fire exposure, the polymer substrates were firstly coated with a few hundred nanometer thick adhesion-promoting plasma polymer layer. Such thin plasma polymer layers were deposited by low-pressure plasma polymerization of allyl alcohol (ppAAl). It was assumed that the hydroxyl groups of ppAAl interact with the melamine resin; therefore, ppAAl was well suited as adhesion promoter for thick melamine resin coatings. Chemical structure and composition of polymer films were investigated using infrared-attenuated total reflectance and X-ray photoelectron spectroscopy (XPS). Peel strengths of coatings were measured. After peeling, the peeled polymer surfaces were also investigated using optical microscopy and XPS the layers for identification of the locus of peel front propagation. Thermal properties were analyzed using TGA (thermo-gravimetric analyses). Finally, the fire-retardant properties of such thick coated polymers were evaluated by exposure to flames.     

Adhesion properties of poly(methylmethacrylate-co-n-butylmethacrylate) copolymers in stent coatings

This work explores the adhesion properties of polymer solutions and thin coatings obtained by different-composition poly(methylmethacrylate-co-n-butylmethacrylate) copolymers. Surface wettability, work of adhesion, and work of spreading are calculated for solutions. Increasing amounts of n-butylmethacrylate lead to higher values of work of adhesion, measured over two stent-like flat surfaces (AISI 316L and pyrolytic carbon). The same moiety induces the solution viscosity increase and the decrease of the work of spreading and allows obtaining more homogeneous coatings. Adhesion of thin coatings is tested in dry (cross-cut test) and wet (immersion) conditions. Adhesion tests of coatings obtained by solvent casting reflect thermodynamic parameters evaluated for solutions. Coatings show better strength in cross-cut tests and a prolonged adhesion in wet conditions by raising the n-butylmethacrylate fraction. The same trends are confirmed in commercial devices. In conclusion, the study of thermodynamic solution/substrate interactions can explain coating properties. The proposed approach is worthwhile to improve deposition procedures based on polymer solutions. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47814.     

Nanocomposites based on vermiculite clay and ternary blend of poly(L‐lactic acid), poly(methyl methacrylate), and poly(ethylene oxide)

Vermiculite (VMT) as clay was introduced into a ternary polymer blend composed of poly(L ‐lactic acid) (PLLA), poly(methyl methacrylate) (PMMA), and poly(ethylene oxide) (PEO), whose ternary miscibility was proven within low certain contents of PMMA and PEO in PLLA. VMT was incorporated to the ternary polymer blend as matrix after proper organic modification on the clay. The organically modified vermiculite (OVMT) shows good interaction and acceptable dispersion in the ternary polymer matrix without altering the crystal structures of PLLA/PEO constituents. The effect of OVMT addition was then analyzed in isothermal crystallization by using the Avrami kinetic analysis, and the addition of OVMT is evident in altering nucleation process of the polymer blend as well as the crystal perfection. The activation energy is much lowered by the addition of OVMT, as evident from the analysis; the overall crystallization kinetic rates are increased with the incorporation of OVMT. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Properties of polystyrene/poly(dimethyl siloxane) blends partially compatibilized with star polymers containing a γ-cyclodextrin core and polystyrene arms

A star polymer with a γ-CD core and PS arms (CD-star) is used to partially compatibilize blends of the immiscible polymers polystyrene (PS) and poly(dimethylsiloxane) (PDMS). The mechanism of compatibilization is threading of the CD core by PDMS and subsequent solubilization in the PS matrix facilitated by the star arms. Films cast from clear solutions in chloroform exhibit large wispy PDMS domains, indicating that some dethreading of CD-star and agglomeration of PDMS takes place during the slow process of solvent evaporation. However, DSC and DMA data show that partial compatibilization takes place, as evidenced by a shift in the PS and PDMS T_gs toward each other. The shift in PS T_g is greater when CD-star is present compared to samples without CD-star. PDMS also tends to leach out of the solution-cast films during solvent evaporation and post-processing of the films. The amount of retained PDMS is significantly increased when CD-star is present. The DMA data also show that PDMS has a lower molecular mobility when CD-star is present.     

Reactive blending of poly (dimethylsiloxane) with nylon 6 and poly (styrene):Effect of reactivity on morphology

Reactive compatibilization was used to control and stabilize 20–30wt% poly(dimethylsioxane) (PDMS) dispersions in nylon 6 (PA) and poly(styrene) (PS), respectively. The effect of the type of reation (amine (NH₂)/anhydride (An), NH₂/ epoxy(E) and carboxylic acid (COOH)/E) on the morphology was studied with electron microscopy. PS and PDMS have mutual solvents thus it was possible to use gel permeation chromatography (GPC) to determine the concentration of block copolymer in PS/PDMS blends. Reactive blending of PA6 with difunctional PDMS‐(AN)₂ did not decrease the PDMS particle size compared to the non‐reactive blend (～10μm). Particle size decreaeased significantly to about 0.5 μm when PA6 was blended with a PDMS containing about 4 random An groups along the chain. For the PS/PDMS blends, GPC revealed that the NH₂/An reaction formed about 3% block copolymer and produced stable PDMS particles ～ 0.4 μm. No reaction was detected for the PS‐NH₂/PDMS‐E blend and the morphology was coarse and unstable. Also, PS‐NH₂/PDMS‐An reactivity was lower compared to other systems such as PS/ poly (isoprene) and PS/poly(methaacrylte) using the same reaction. This was attributed to the relatively thinner PS/PDMS interface dueto the high PS/PDMs immiscibility.     

A preparation of polyethylene coatings by pulse laser-assisted electron beam deposition

Polyethylene (PE) coatings were prepared by a method of pulse laser-assisted electron beam deposition, using low-density polyethylene as evaporated target, silicon wafer and polytetrafluoroethylene (PTFE) sublayer as substrates. The as-deposited PE coatings were characterized by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and atomic force microscope. Significant crystallinity increase and root mean square (RMS) roughness decrease of PE coatings were observed in the presence of PTFE sublayer. Laser-assisted deposition increased the crystallinity and mean particle diameter of PE coatings and remarkably, the obtained PE coatings had a relative uniform particle size. These results suggested that pulse laser and PTFE sublayer might contribute to the synthesis of polymer coatings with suitable crystallinity and uniform surface structure.     

聚芴醚酮超疏水喷涂纸及其性能

以聚二甲基硅氧烷(PDMS)和纳米SiO2掺杂聚芴醚酮(PFEK),采用溶液喷涂法在纸张表面构筑了耐用的超疏水涂层.考察了PDMS和SiO2用量(以PFEK和N-甲基吡咯烷酮的质量为基准,下同)对纸张水接触角的影响.结果表明,当PDMS和SiO2用量均为2％时,纸张表面的水接触角达到最大值170?,滚动角最小值为1?,...     

Fabrication of core–shell hybrid nanoparticles by mineralization on poly(ε-caprolactone)-b-poly(methacrylic acid) copolymer micelles

Polymer micelles containing calcium phosphate (CaP) minerals on the shell domain were developed by nanotemplate-driven mineralization. The polymer micelle nanotemplate was prepared by self-assembly of a poly(ε-caprolactone)-b-poly(methacrylic acid) (PCL-b-PMAA) copolymer. PMAA formed the anionic outer shell, and PCL constructed the hydrophobic inner core. Subsequent addition of calcium and phosphate ions to micellar solutions induced CaP mineral deposition within the PMAA shell domain. Transmission electron microscopy (TEM) showed the well-defined nanostructure consisting of the CaP nanoshell and the PCL inner core. Energy-dispersive X-ray spectroscopy (EDS) confirmed CaP deposition on polymer micelles. Dynamic light scattering (DLS) study showed CaP mineralization greatly enhanced the micellar stability.     

Thermal imidization of poly(amic acid) precursors on surface-modified poly(tetrafluoroethylene) films via graft copolymerization with glycidyl methacrylate

A novel method for preparing composites of polyimides (PI) laminated to poly(tetrafluoroethylene) (PTFE) films is reported. PI/PTFE composites were developed through thermal imidization of poly(amic acid) (PAA) precursors on surface-modified PTFE films. Surface modification of PTFE films was carried out via Ar plasma pretreatment of the films, followed by UV-induced graft copolymerization with glycidyl methacrylate (GMA). The surface composition and topography of the graft copolymerized PTFE films and the delaminated PI and PTFE surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), respectively. The adhesion strengths of the PI (imidized PAA) on the GMA graft copolymerized PTFE films were evaluated as a function of various thermal imidization schedules. The adhesion reliability of the PI/PTFE composites was tested by a series of hydrothermal cycles. The development of strong Tpeel adhesion strengths of about 8 N/cm with excellent reliability for the PI/PTFE composites was attributable to the synergistic effect of coupling the curing of the epoxide functional groups of the grafted GMA chains with the imidization process of the PAA and the fact that the GMA chains were covalently tethered onto the PTFE surface. The PI/PTFE composites delaminated via cohesive failure inside the PTFE substrates. The delaminated PI film with a covalently adhered 'rough' PTFE surface layer exhibited a water contact angle as high as 140°.     

Investigation of the interaction of CO2 with poly (L‐lactide), poly(DL‐lactide) and poly(ε‐caprolactone) using FTIR spectroscopy

Fourier transform infrared (FTIR) spectroscopy was used to reveal intermolecular interactions between carbon dioxide (CO₂) and the carbonyl groups of poly(L ‐lactide) (PLLA), poly(D,L ‐lactide) (PDLLA), and poly(ε‐caprolactone) (PCL). After exposing polymer films to high pressure CO₂, the wave number of the absorption maxima of the polymer carbonyl groups shifted to higher values. Also, due to the interaction between CO₂ and the carbonyl groups of the polymers, a new broad peak in the bending mode region of CO₂ appeared. To distinguish between polymer‐associated and nonassociated CO₂, and to quantify these contributions, the bending mode peaks were deconvoluted. From these contributions, it was found that in the case of PCL more CO₂ is interacting with the polymer carbonyl groups than in the case of PDLLA and PLLA. Under our experimental conditions, 40°C and pressures up to 8 MPa, a significant depression of the PCL melting temperature was observed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

A comparative study on protective properties of electrosynthesized poly(pyrrole)/poly(N-methylpyrrole), poly(pyrrole)/poly(N-phenylpyrrole), poly(pyrrole)/poly(N-methoxyphenylpyrrole) composite coatings

In this study, three sets of different bilayered composite coatings of pyrrole and N-substituted pyrroles were synthesized by a layer-by-layer approach on copper surface and corrosion performances of the synthesized materials were compared. Electrodepositions of poly(N-methylpyrrole), poly(N-phenylpyrrole), and poly(N-methoxyphenylpyrrole) were performed in nonaqueous medium on a poly(pryrrole)-coated copper surface using cyclic voltammetry. The morphologies of the resulting bilayered composite coatings of poly(pyrrole)/poly(N-methylpyrrole), poly(pyrrole)/poly(N-phenylpyrrole), and poly(pyrrole)/poly(N-methoxyphenylpyrrole) were investigated by scanning electron microscopy. Stabilities of a doping-dedoping process of the composites were determined from the cyclic voltammetric study of the bilayer-coated electrodes in a monomer-free solution. Corrosion performances of the bilayer composite-coated and uncoated copper electrodes were investigated in 0.1 M H₂SO₄ solution using open circuit potential–time (E _ocp–t) curves, anodic polarization, and electrochemical impedance spectroscopy. All the investigated bilayered coatings gave significant enhancement in the corrosion resistance of copper, compared to the single poly(pyrrole) coating. Stability and corrosion tests revealed that the composite material poly(pyrrole)/poly(N-methoxyphenylpyrrole) exhibited higher electrochemical stability and corrosion resistant behavior than the other bilayered composite coatings.     

Characterization of the mechanical and thermal properties and morphological behavior of biodegradable poly(L‐lactide)/poly(ε‐caprolactone) and poly(L‐lactide)/poly(butylene succinate‐co‐L‐lactate) polymeric blends

Two series of biodegradable polymer blends were prepared from combinations of poly(L ‐lactide) (PLLA) with poly(?‐caprolactone) (PCL) and poly(butylene succinate‐co‐L ‐lactate) (PBSL) in proportions of 100/0, 90/10, 80/20, and 70/30 (based on the weight percentage). Their mechanical properties were investigated and related to their morphologies. The thermal properties, Fourier transform infrared spectroscopy, and melt flow index analysis of the binary blends and virgin polymers were then evaluated. The addition of PCL and PBSL to PLLA reduced the tensile strength and Young's modulus, whereas the elongation at break and melt flow index increased. The stress–strain curve showed that the blending of PLLA with ductile PCL and PBSL improved the toughness and increased the thermal stability of the blended polymers. A morphological analysis of the PLLA and the PLLA blends revealed that all the PLLA/PCL and PLLA/PBSL blends were immiscible with the PCL and PBSL phases finely dispersed in the PLLA‐rich phase. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Coating of carbon fibers with adhesion-promoting thin poly(acrylic acid) and poly(hydroxyethylmethacrylate) layers using electrospray ionization

Thin coatings of poly(acrylic acid) (PAA) and poly(hydroxyethylmethacrylate) (PHEMA) were deposited onto carbon fibers by means of the electrospray ionization (ESI) technique in ambient air. These high-molecular weight polymer layers were used as adhesion promoters in carbon fiber–epoxy resin composites. Within the ESI process, the carbon fibers were completely enwrapped with polymer in the upper 10 plies of a carbon fiber roving. As identified with scanning electron microscopy also shadowed fibers in a bundle as well as backsides of fiber rovings were pinhole-free coated with polymers (‘electrophoretic effect’). Under the conditions used, the layers have a granular structure. Residual solvent was absent in the deposit. PAA and PHEMA films did not show any changes in composition and structure in comparison with the original polymers as analyzed by X-ray photo-electron spectroscopy and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Single-fiber pullout tests of coated fibers embedded in epoxy resin showed significantly increased interfacial shear strength. It is assumed that chemical bonds between carbon fiber poly(acrylic acid) and epoxy resin contribute significantly to the improved interactions.     

Mechanical properties of poly(ε‐caprolactone) and poly(lactic acid) blends

The aim of this work was to better understand the performance of binary blends of biodegradable aliphatic polyesters to overcome some limitations of the pure polymers (e.g., brittleness, low stiffness, and low toughness). Binary blends of poly(ε‐caprolactone) (PCL) and poly(lactic acid) (PLA) were prepared by melt blending (in a twin‐screw extruder) followed by injection molding. The compositions ranged from pure biodegradable polymers to 25 wt % increments. Morphological characterization was performed with scanning electron microscopy and differential scanning calorimetry. The initial modulus, stress and strain at yield, strain at break, and impact toughness of the biodegradable polymer blends were investigated. The properties were described by models assuming different interfacial behaviors (e.g., good adhesion and no adhesion between the dissimilar materials). The results indicated that PCL behaved as a polymeric plasticizer to PLA and improved the flexibility and ductility of the blends, giving the blends higher impact toughness. The strain at break was effectively improved by the addition of PCL to PLA, and this was followed by a decrease in the stress at break. The two biodegradable polymers were proved to be immiscible but nevertheless showed some degree of adhesion between the two phases. This was also quantified by the mechanical property prediction models, which, in conjunction with material property characterization, allowed unambiguous detection of the interfacial behavior of the polymer blends. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Inorganic particle coating with poly(dimethylsiloxane)

Stable, thick poly(dimethylsiloxane) (PDMS) coatings are formed on iron(III) and aluminum oxide and calcium carbonate particles by impregnating the particles with dimethylsilicone oil and heating at 250–280°C. These coatings are strongly resistant to solvent extraction and to exposure in a water-saturated atmosphere. Coated particles are strongly hydrophobic, as evidenced by their greater stability in apolar solvents. Silicone coating formation on oxide particles is interpreted as a result of two reactions: siloxane chain opening at higher temperatures, followed by the reaction of active chain end-groups with hydroxo groups at the metal oxide or carbonate surfaces and silicone cross-linking by methylene or siloxane bridges. The procedures described in this paper differ from usual silanization or siliconization procedures because it uses stable PDMS and yields thicker coatings. © 1996 John Wiley & Sons, Inc.     

Morphology of polystyrene/poly(dimethyl siloxane) blends compatibilized with star polymers containing a γ-cyclodextrin core and polystyrene arms

A star polymer with a γ-CD core and PS arms is used to compatibilize blends of the immiscible polymers PS and PDMS. The mechanism of compatibilization is threading of the CD core by PDMS and subsequent solubilization in the PS matrix facilitated by the star arms. Spun-cast films of this blend are examined with optical microscopy, scanning electron microscopy and atomic force microscopy. Blends without CD-star exhibit large-scale phase separation, whereas those containing CD-star exhibit very homogeneous morphologies in the optical microscope and nanometer-sized phase domains in the AFM. The effect of PDMS molecular weight on the blend morphology is insignificant. The morphology of the compatibilized films does not change significantly after annealing at 125 °C for 3 days, indicating that the CD-star polymer effectively stabilizes these blends at temperatures where both polymers are mobile and could otherwise undergo large-scale phase separation. The degree of compatibilization in these blends is correlated with the molar ratio of PDMS repeat units to CD-star molecules.     

Surface structures and adhesion enhancement of poly(tetrafluoroethylene) films after modification by graft copolymerization with glycidyl methacrylate

Surface modifications of Ar plasma-pretreated poly(tetrafluoroethylene) (PTFE) film were carried out via near-UV light-induced graft copolymerization with glycidyl methacrylate (GMA). The structure and chemical composition of the copolymer surface and interface were studied by angle-resolved X-ray photoelectron spectroscopy (XPS). For PTFE substrate with a substantial amount of grafting, the grafted GMA polymer penetrates or becomes partially submerged beneath a thin surface layer of dense substrate chains to form a stratified surface microstructure. The concentration of the surface-grafted GMA polymer increases with the plasma pretreatment time, the near-UV light illumination time, and the monomer concentration. The GMA graft copolymerized PTFE surfaces adhere strongly to one another when brought into direct contact and cured (i) in the presence of a diamine alone or (ii) in the presence of an epoxy adhesive (epoxy resin plus diamine curing agent). In the presence of diamine alone, failure occurs in the interfacial region. For epoxy adhesive-promoted adhesion, the failure mode is cohesive, i.e. it takes place in the bulk of one of the delaminated PTFE films. The lap shear strengths in both cases increase with the amount of surface-grafted epoxide polymer. The development of the adhesion strength depends on the concentration of the surface graft, the microstructure of the graft copolymerized PTFE surface, the interfacial reactions, and the nature of the bonding agent.     

Adhesion of Vacuum Deposited Optical Coatings on PMMA and Polycarbonate

Abstract

The deposition of interference coatings with optical functions (e.g., anti-reflective coatings, beam splitters and filters) on plastic substrates is becoming ever more important. A well-known deposition method for such coatings on polymers is plasma ion-assisted vacuum evaporation (plasma ion-assisted deposition or plasma IAD). However, the industrial production of well-adhering dielectric coatings on unlacquered polymer surfaces has not yet been developed to a satisfactory level. PMMA is known to be extremely difficult to coat with optical layers because of its inadequate adhesion characteristics. Polycarbonate is considered to be less problematic, but in many cases unexpected adhesion failures arise. This paper presents a study of the reasons for the poor adhesion to PMMA of oxide coatings deposited by plasma IAD. We show that in such a coating process it is only the exposure of the substrate to particles and short-wavelength radiation that determines its adhesion to the deposited layer. For polycarbonate, we found a dependence of the adhesion strength of the coating on its porosity. Considering these results, modified plasma IAD processes have been developed that enable the deposition of well-adhering optical coatings on these polymers.