Novel method for fabrication of PP/HDPE/PP trilayer microporous membrane with a highly orientated structure

In this work, a highly orientated polopropelene/high-density polyethylene/polopropelene (PP/HDPE/PP) trilayer cast film was obtained from viscous encapsulation of HDPE and PP which involved of controlling the molecular factors and processing conditions. Consequently, a stable stratified flow was obtained as a result of phase-segregation through a single screw extruder under a high draw ratio (DR). Microporous HDPE, PP monolayer films as well as PP/HDPE/PP trilayer film have been successfully fabricated after a proper cold and hot stretching. The influence of DR and annealing process on crystalline structure and orientation of monolayer and trilayer membrane was investigated by differential scanning calorimetry, two-dimensional wide-angle X-ray diffraction and Fourier transform infrared. Both crystallinity and crystalline orientation increased with DR and annealing process. Additionally, the crystallinity in PP/HDPE/PP was lower than it in monolayer films but the orientation of PP/HDPE/PP was higher compared to monolayer films. The lamellae structure of HDPE, PP, and PP/HDPE/PP cast films prepared at different DR values and the influence of annealing process was also studied. The lamellae parameters, the long period (L_p ), the thickness of crystalline region (L_c ) and the thickness of amorphous region (L_a ) were obtained via 2D-small angle X-ray scattering. The long period (L_p ) of PP was 35% smaller than HDPE implying tight stacking in PP. The scanning electron microscopy micrographs of the membrane surface morphology and cross-section obtained from the cold and hot stretching of 30% and 150%, respectively. The results showed that the pore size of HDPE was greater than PP. Besides, the pore number and regularity of PP/HDPE/PP at DR = 90, which had a porosity of 0.48, was the best among all samples. The cross-section of PP/HDPE/PP trilayer membrane was found to be a multilayer structure. However, the majority of HDPE phase was in the middle of film while PP phase was absolutely at the edge of the film. The current work may open an entirely novel and simple way to fabricate PP/HDPE/PP trilayer microporous films. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47249.     

Effect of additives on the composition dependent glass transition variation in PS/PP blends

The effect of additives on glass transition behavior in melt processed blends of polystyrene (PS) and polypropylene (PP) was studied. Blends of additive‐free polystyrene and additive‐free polypropylene revealed the known effect of the PS T_g increase in blend compositions where PP surrounds PS. Glass transition behavior in these blends was compared to blends prepared from additive‐free PP and commercial grade PS, which contained lubricant additives. The thermal transitions of PS and PP were measured using modulated DSC. Although the behavior of low PS concentration blends was similar in both systems, the characteristics of the high PS blends differed substantially. These differences and the contrast in the PP T_g behaviors were attributed to the migration of additives from the PS phase across the immiscible interface into the PP phase. Similar T_g variations were observed in blends of commercial grade PS and commercial grade PP. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Surface analysis of aminated polypropylene films as an adhesion promoter to polycarbonate film

The surface composition of aminated polypropylene films (PP‐g‐NH₂) and their adhesion to polycarbonate (PC) film were evaluated. The detection of amine groups on PP‐g‐NH₂ surfaces was obtained by X‐ray photoelectron spectroscopy (XPS). Contact angle measurements showed a decreased in the polarity on PP‐g‐NH₂ surface The adhesion between laminated films of PP‐g‐NH₂ and PC was evaluated by T‐peel test and optical microscopy. PC deposited on the PP‐g‐NH₂ surfaces was confirmed by FTIR‐ATR and SEM analysis of delaminated films, which is an indicative of an interaction between reactive sites of each polymer. The adhesion performance between PC and PP was improved by using amine modified polypropylene (PP‐g‐NH₂). © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

How the infrared radiation affects the film formation process from latexes?

In this study, the effect of the infrared radiative heating (IRH) was investigated on the film formation from composites of polystyrene (PS) latex particles and poly vinyl alcohol (PVA). The films were prepared as a pure PS and a mixture of PS and PVA particles at equal compositions at room temperature and they were annealed at elevated temperatures above the glass transition temperature (T_g) of PS for 10 min by using IRH technique. Identical experiments were performed by using standard convectional heating technique in oven as comparison. It was shown that the activation energy for the film formation from PS latex particles decreased considerably in IRH annealing technique. Photon transmission (PT) and steady state fluorescence (SSF) techniques were used to monitor the film formation process at each sintering step. Minimum film formation temperature, T_o, and healing temperature, T_h, were determined by the data obtained from the SSF and the PT measurements for each heating processes. The film formation was modeled as a void closure and as an interdiffusion stage below and above T_h, respectively. Scanning electron microscopy (SEM) was used to examine the variation in morphological structure of annealed composite films. It was observed that IRH heating causes more homogenous and more flat film surface than films annealed in the oven. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43289.     

Piezoelectric Properties of Ink‐Jet–Printed Lead Zirconate Titanate Thick Films Confirmed by Piezoresponse Force Microscopy

An ink consisting of Pb(Zr_0.53Ti_0.47)O₃ (PZT) particles with a median size of 170 nm and a narrow size distribution, in a dispersion of water and glycerol, and with a low viscosity and surface tension, was used for the fabrication of thick films by piezoelectric ink‐jet printing. This study reports the printing conditions, the subsequent thermal treatment of the as‐deposited layers, and the properties of the sintered PZT thick film. The film, sintered at 1100°C, had a locally dense microstructure and consisted of grains that are a few 100 nm across, as revealed by scanning electron microscopy. A local piezoelectric response of 15 pm/V was measured in the ink‐jet–printed PZT thick film by piezoresponse force microscopy.     

Processing characteristics,structure development,and properties of uni and biaxially stretched poly(ethylene 2,6 naphthalate) (PEN) films

Poly(ethylene 2,6, naphthalene dicarboxilate), PEN, is very similar to poly(ethylene terephthalate), PET, in its chemical structure and was, therefore, expected to exhibit similar processing characteristics. We, however, observed a few problems during stretching of PEN, the most important of which was necking behavior at 145°C, which is between T_g (117°C) and T^cc (195°C). This is usually observed in PET only when it is stretched close to or below T_g. At temperatures between T_g and T_cc (cold crystallization temperature) PET stretches rather uniformly. The temperature window for film stretching appears to be rather wide, but our results indicate that this is not the case. Films stretched to high stretch ratios become uniform due to propagation and final disappearance of necks as a result of stress hardening. Our attempts at stretching these films at higher temperatures indicated that necking is eliminated, but so is stress induced crystallization, which causes stress hardening (unless high stretching rates are employed). The presence of stress hardening is essential for obtaining high quality, uniform films of these polymers. In addition, at high temperatures thermally activated crystallization which starts dominating the structure development, detrimentally affects the general appearance of the films. In brief, the PEN films we investigated have a narrower processing window than was anticipated based on their thermal behavior alone. At elevated temperatures the films are sensitive to the rate of stretching even more than typical PET processed at comparable conditions. The uniformity of the films depends on the stretch ratio, stretching mode, ratio(s) and rates and temperature. WAXS studies on the films indicate that the macromolecules packed into the low temperature crystal modification. In addition, WAXS pole figure studies suggest that naphthalene planes preferentially orient parallel to the film surface during biaxial stretching. The biaxially stretched films were observed to exhibit a bimodal chain orientation as evidenced by pole figure analysis of the (010) planes.     

Improved thin film stability of differently formulated,printed, and crosslinked polymer layers against successive solvent printing

Interface control remains a top challenge of solution-processed organic light emitting diodes (OLED) stacks since the device performance heavily relies on it. Film stability of an inkjet deposited and crosslinked layer against subsequent exposure to a suitable inkjet printed solvent has been investigated. Impact of processing solvent (solvent used to prepare the polymer layer) on solution-cast thin film properties has already been shown for polymer films. To our knowledge, this study is the first one analyzing thin films stability against solvent exposure using technology relevant materials processed via inkjet printing (IJP). The outcome of this research showed that the stability of the crosslinked films is affected by the solvent used for ink formulation. These findings are of great interest for multilayered semiconductors devices, such as OLEDs, field-effect transistors and dye-sensitized solar cells. Differential scanning calorimetry (DSC) was used to quantify the efficiency of the polymer crosslinking reaction in pure powder and in thin films, as processed from different solvents. Crosslinking efficiency measured by DSC correlated well with the deformation induced by the solvent and observed on layer surfaces. The interaction in solution between polymer and solvent has also been evaluated to explain its impact on thin film stability against successive solvent printing. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48895.     

Polymer/carbon nanotube composite film formation: A fluorescence study

In this study, the effect of multi‐walled Carbon nanotube (MWNT) on film formation behavior of Polystrene (PS) latex film was investigated by using steady state fluorescence technique. Films were prepared by mixing of pyrene (P)‐labeled PS latex with different amounts of MWNTs varying in the range between 0 and 20 wt%. After drying, MWNT containing films were separately annealed above glass transition temperature (T_g) of PS ranging from 100 to 270°C for 10 min. In order to monitor film formation behavior of PS/MWNT composites, Scattered light (I_s) and fluorescence intensities (I_P) from P were measured after each annealing step to monitor the stages of film formation. At 0–20 wt% range of MWNT content films, minimum film formation (T_o), void closure (T_v), and healing, (T_h) temperatures were determined. Void closure and interdiffusion stages were modeled and related activation energies were determined. It was observed that while void closure activation energies increased, backbone activation energies decreased as the percent of MWNT is increased in the composite films. POLYM. COMPOS., 35:817–826, 2014. © 2013 Society of Plastics Engineers     

Optimized processing conditions for the preparation of dynamically vulcanized EPDM/PP thermoplastic elastomers containing PP resins of various melt indexes

We have investigated the mechanical and morphological properties of un‐vulcanized and dynamically vulcanized ethylene propylene diene terpolymer/polypropylene (EPDM/PP) thermoplastic elastomers prepared under various processing conditions and possessing various compositions. After melt‐blending EPDM and PP resins twice in a twin‐screw extruder, the values of tensile strength (σ_f) of the un‐vulcanized EPDM/PP samples were at most equal to that of the pure EPDM specimen, but were much lower than those of the pure PP specimens. The elongations at break (ε_f) of the un‐vulcanized EPDM/PP samples were, however, dramatically higher than those of their respective virgin PP resins, and they improved significantly upon increasing the shear viscosity (η_s) of the PP resins. The tensile properties of the dynamically vulcanized EPDM/PP samples were significantly better than those of the corresponding un‐vulcanized EPDM/PP specimens. Similar to the behavior of the un‐vulcanized EPDM/PP specimens, the tensile properties of the dynamically vulcanized EPDM/PP specimens were optimized when prepared at a screw rate of 115 rpm. Morphological analysis revealed that the un‐vulcanized and dynamically vulcanized EPDM/PP specimens both featured many EPDM domains finely dispersed in continuous PP matrices. Such domains were present on the surfaces of the dynamically vulcanized EPDM/PP specimens; the relative sizes of the vulcanized EPDM domains were minimized when the vulcanized EPDM/PP specimens were prepared at the optimal screw rate (115 rpm). In fact, under these conditions, the average sizes of the vulcanized EPDM domains decreased upon increasing the values of η_s of the PP resins used to prepare the vulcanized EPDM/PP specimens. To understand these interesting tensile and morphological properties of the un‐vulcanized and dynamically vulcanized EPDM/PP specimens, we measured the rheological properties of the base polymers and performed energy‐dispersive x‐ray (EDX) analyzes of the compositions of the un‐vulcanized and dynamically vulcanized EPDM/PP specimens. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Thermal Expansion of Thin Diblock Copolymer Films

The thermal expansion of thin films of symmetric diblock copolymers of polystyrene (PS) and poly(methyl methácrylate) (PMMA) was investigated by X-ray reflectivity. The confinement of the copolymer to the substrate, coupled with the multilayering of the copolymer where PS and PMMA layers are oriented parallel to the substrate, gives rise to unusual thermal expansion characteristics. The total thickness of the film increases as 3α_L, where α_L is the linear thermal expansion coefficient of the copolymer. Unlike homopolymer films, the thermal expansion of an ordered block copolymer film results in an excessive stretching of the copolymer chains at the interface between the PS and PMMA layers. This excess stretching is a result of the confinement of the junction points of the copolymer chains to the interfaces and the suppression of the lateral expansion of the copolymer. When the stretching of the chains becomes too high, relaxation occurs by transporting copolymer chains to the surface. This is evidenced by a reduction in the period of the multilayer. After the copolymer chains have relaxed, the change in the multilayer period with temperature closely follows α_L.     

Hydrophilic modification of polypropylene microporous membranes by grafting TiO2 nanoparticles with acrylic acid groups on the surface

Hydrophilic microporous membranes were prepared based on polypropylene (PP) cast films blended with a commercial acrylic acid grafted polypropylene (PP-g-AA) via melt extrusion followed by grafting titanium dioxide (TiO₂) nanoparticles on its surface, annealing and stretching. ATR-FTIR, XPS and EDS analyses showed that the hydrophilic segments of an amphiphilic modifier (PP-g-AA) acted as surface functional groups on the film surface. The results indicated that the presence of the modifier was very important for grafting TiO₂ nanoparticles on the film surface. Compared to PP and PP/PP-g-AA blend films, the water contact angle decreased by a factor of 2.5 after grafting TiO₂ on the surface of the films, meanwhile the water vapor permeability of the microporous membranes prepared from those films increased by a factor of 1.5. All these results indicated that the hydrophilicity of the modified PP membranes was improved.     

Film formation of nano‐sized hard latex (PS) in soft polymer matrix (PBA): An excimer study

This work reports steady state fluorescence (SSF) technique for studying film formation from pyrene (P)‐labeled nano‐sized polystyrene (PS) and poly(n‐butyl acrylate) (PBA) hard/soft latex blends. Blend films were prepared from mixtures of PS and PBA in dispersion. Eight different blend films were prepared in various hard/soft latex compositions at room temperature and annealed at elevated temperatures above glass transition temperature (T_g) of polystyerene. Monomer (I_P) and excimer (I_E) intensities from P was measured after each annealing step to monitor the stages of film formation. The evolution of transparency of latex films was monitored using photon transmission intensity, I_tr. Film morphologies were examined by atomic force microscopy (AFM). The results showed that as the amount of hard component (PS) in the blend is decreased, a significant change occurred in both I_E/I_P and I_tr curves at a certain critical weight fraction (50 wt%) of PS hard latex. Two distinct film formation stages, which are named as void closure and interdiffusion were seen in (I_E/I_P) data above this fraction. However, below 50 wt% PS no film formation was observed. AFM pictures also confirmed these findings. Void closure and interdiffusion stages for (50–100) wt% range of PS were modeled and related activation energies were determined. There was no observable change in activation energies confirming that film formation behavior is not affected by varying the blend composition in this range. POLYM. COMPOS., 31:1611–1619, 2010. © 2009 Society of Plastics Engineers     

The effect of clay particles on film formation from polystyrene latex

Film formation from surfactant‐free polystyrene (PS) latex was performed in the presence of 5% Na‐montmorillonite (NaMMT). The composite films were prepared from pyrene (P)‐labeled PS particles at room temperature and annealed at elevated temperatures above the glass‐transition (T_g) temperature of polystyrene. Scattered light (I_s) and fluorescence intensity (I_P) from P were measured after each annealing step to monitor the stages of composite film formation. Minimum film formation temperature, T₀, and healing temperatures, T_h, were determined. Void closure and interdiffusion stages were modeled and related activation energies were measured. From these results, it was found that the presence of NaMMT in the PS latex film only affects the minimum film formation, but does not affect the void closure and backbone motion activities. POLYM. COMPOS., 27:299–308, 2006. © 2006 Society of Plastics Engineers     

Characterization and application of polypropylene films modified with stimuli‐sensitive copolymers with an Ar‐plasma postpolymerization technique

Surface‐modified polypropylene (PP) films with thermally and photochemically sensitive copolymers consisting of N‐(2‐hydroxypropyl)methacrylamide (HPMA) and 4‐(4‐methoxyphenylazo)phenyl methacrylate (MPAP), poly(HPMA‐co‐MPAP)‐g‐PP (abbreviated g‐PP) film, were prepared by graft copolymerization with an Ar‐plasma postpolymerization technique. The surfaces of the g‐PP films were characterized by means of X‐ray photoelectron spectroscopy; the percentage grafting of poly(HPMA‐co‐MPAP) with a number‐average molecular weight of 3.28 × 10⁴ was 7.12%, and the molar ratio of HPMA–MPAH in the copolymer was 0.75:0.25. The stimuli‐sensitive adsorption of albumin and polystyrene microspheres on the g‐PP film was also measured. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 143–148, 2003     

Ionic liquids as performance additives for water‐based printing inks

For the first time, the use of ionic liquids as additives for printing inks in order to improve the wettability of the printing base by the ink is presented. The aim of this work was to study the influence of ionic liquids on the selected properties of water‐based printing ink and the prints. The contact angles of the printing inks on the printing base were measured. Modified flexographic inks were laboratory printed on polypropylene plastic film. The impact of small amounts of various ionic liquids on printing ink colour was examined in terms of the optical density of the full‐tone area, the colour parameters (L*, a*, b*, CIE), the total colour difference, and the gloss of the dried ink film. The influence of ionic liquids on the ink contact angle, the optical density, and the L*a*b* coordinates is discussed. In general, the investigated ionic liquids improve the wettability of water‐based flexographic printing ink, with an acceptable total colour difference. The optical density is increased for printing inks containing ionic liquids in comparison with the original flexographic printing ink, Process.     

Film formation from polystyrene–poly(butyl acrylate‐co‐methyl methacrylate) latex blends

We have employed steady sate fluorescence (SSF) and UV‐visible (UVV) techniques to determine the film formation behavior of latex blends. Blend films were prepared from mixtures of a high‐T_g pyrene (P) labeled polystyrene (PS) latex and a low‐T_g copolymer of poly(butyl acrylate‐co‐methyl methacrylate) (BuA/MMA4). Eleven different blend films were prepared in various hard/soft latex compositions at room temperature and annealed at elevated temperatures above glass‐transition (T_g) temperature of polystyerene for 10 min. Fluorescence intensity (I_P) from P was measured after each annealing step to monitor the stages of film formation. The evolution of transparency of latex films was monitored using photon transmission intensity, I_tr. Film morphologies were examined by atomic force microscopy (AFM). A significant change occurs in both I_P and I_tr intensities at a certain critical weight fraction of hard latex (R_c = 0.3). Above R_c, two distinct film formation stages, which are named as void closure and interdiffusion processes, were seen in fluorescence data. Transparency of the films was decreased with decreasing PS content, indicating that a phase separation process occurs between PS and BuA/MMA4 phases by thermal treatment, which results in turbid films. However, below R_c, no change was observed in I_P and I_tr upon annealing, whereas transparency increased overall with increasing BuA/MMA4 ratio. We explained this result as the phase separation process between PS and BuA/MMA4 blends. These results were also confirmed by AFM pictures. Film formation stages above R_c were modeled and related activation energies were calculated. POLYM. COMPOS., 27:431–442, 2006. © 2006 Society of Plastics Engineers     

Hydrophilic–oleophobic behaviour in thin films from fluoromodified nanoclays and polystyrene

New nanocomposite thin films were prepared by spin coating technique from polystyrene (PS) and montmorillonite (MMT) modified with perfluoropolyether cationic ammonium salts (FOMMT). The coating thickness was tuned by changing the solution concentration, and it was measured by the scratching method with atomic force microscopy (AFM). Demodulation AFM images of the higher thickness (>100 nm) PS/FOMMT nanocomposite coating do not show any phase difference suggesting the formation of a homogeneous structure, while the corresponding demodulation image of the lower thickness (ca. 60 nm) PS/FOMMT nanocomposite film revealed the presence of two different phases, which may be attributed to fluoromodified clays and polystyrene. Surface characterization was made through contact angle (CA) measurements and it showed unexpectedly low surface tension dispersive component γ _s ^d (around 12 mN/m) and a very high polar components γ _s ^d (50 mN/m) in the case of the lower thickness PS/FOMMT nanocomposite coating.     

Effect of flow history on poly(vinylidine fluoride) crystalline phase transformation

This study was devoted to the effect of extensional flow during film extrusion on the formation of the β‐crystalline phase and on the piezoelectric properties of the extruded poly(vinylidine fluoride) (PVDF) films after cold drawing. The PVDF films were extruded at different draw ratios with two different dies, a conventional slit die and a two‐channel die, of which the latter was capable of applying high extensional flow to the PVDF melt. The PVDF films prepared with the two‐channel die were drawn at different temperatures, strain rates, and strains. The optimum stretching conditions for the achievement of the maximum β‐phase content were determined as follows: temperature = 90°C, strain = 500%, and strain rate = 0.083 s^?1. The samples prepared from the dies were then drawn under optimum stretching conditions, and their β‐phase content and piezoelectric strain coefficient (d₃₃) values were compared at equal draw ratios. Measured by the Fourier transform infrared technique, a maximum of 82% β‐phase content was obtained for the samples prepared with the two‐channel die, which was 7% higher than that of the samples prepared by the slit die. The d₃₃ value of the two‐channel die was 35 pC/N, which was also 5 pC/N higher than that of the samples prepared with the slit die. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Oxygen diffusion into polystyrene–bentonite films

A simple fluorescence technique is proposed for the measurement of the diffusion coefficient of oxygen into polystyrene–clay composite films. The composite films were prepared from the mixture of surfactant-free pyrene (P)-labeled polystyrene latexes (PS) and modified bentonite (MNaLB) at various compositions at room temperature. These films were annealed at 200 °C above the glass transition (T_g) temperature of polystyrene for 10 min. Oxygen diffusion into the films was monitored with steady state fluorescence (SSF) measurements. Measurements were performed at room temperature for different film compositions (0, 5, 10, 20, 30, 50 and 60 mass% modified bentonite) films to evaluate the effect of MNaLB content on oxygen diffusion. The diffusion coefficient, D of oxygen was determined by the fluorescence quenching method by assuming Fickian transport and increased from 7.4 × 10^− 10 to 26.9 × 10^− 10 cm² s^− 1 with increasing MNaLB content. This increase in D value was explained by formation of microvoids in the film. These voids are large enough to contribute to the penetration of oxygen molecules through the films. The montmorillonite content did not affect the quenching rate constant, k_q and mutual diffusion coefficient, D_m values.     

Synthetic paper from plastic waste: Influence of a surface treatment with corona discharge

Polymers generally have a chemically inert surface, are nonporous, and have low surface energy, which is characterized by their relatively weak adhesion to other materials. Numerous methods have been developed to modify polymer surfaces chemically. This study was an investigation of how the surface energy of synthetic paper (composite film) could be altered after treatment by corona discharge and of the stability of the surface energy of a film produced from postconsumer polypropylene (PP). A PP/filler (70/30 w/w) composite film was processed in a single‐screw extruder with a flat‐film dye. In this study, the film stretching rate and electric charge potential of the film surface treatment were the process parameters analyzed. The results showed that the conditions of the surface treatment by corona discharge and the presence of a filler (calcium carbonate) influenced some surface properties: the contact angle, surface energy, and ink adhesion. The surface energy of the composite film increased from 38.7 × 10^?3 N/m² without treatment to 52.3 × 10^?3 N/m² with treatment. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009