Breathable polymeric materials based on high-density polyethylene prepared by environmental crazing

This work addresses the preparation of breathable materials based on high-density polyethylene (HDPE) and characterization of their performance. The sustainable HDPE mesoporous materials were prepared by the tensile drawing of the HDPE films in the presence of physically active liquids (PALEs) via the mechanism of environmental intercrystallite crazing (EIC). The prepared mesoporous materials were characterized by the different physicochemical methods such as differential scanning calorimetry (DSC), atomic force microscopy (AFM), low-temperature nitrogen adsorption (LTNA), and so forth. Water vapor transmission rate (WVTR) of the breathable materials can be tailored by varying the tensile strain upon the EIC and is found to be equal to 597–1345 g m⁻² day⁻¹. The breathable HDPE-based materials are characterized by good mechanical and insulating properties as well as by high water entry pressure (~43–47 bar). Hence, the deformation of HDPE films via the EIC mechanism provides an efficient route for the preparation of mesoporous breathable materials based on the low-cost commercial polymers, which can be used as waterproof, protective, subroof, gas storage, and packaging materials. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48567.     

Environmental stress cracking and crazing in polymers in terms of irreversible thermodynamics

The processes in environmental stress cracking and crazing in polymers are analysed in terms of the irreversible thermodynamics. The thermodynamic potential of the system composed of the polymer matrix at a flaw tip region and its environmental liquid is constructed as a function of the concentration of the liquid migrated in the matrix and the dilative stress due to stress concentration. A state of the system is represented by a point in the thermodynamic potential diagram. The paths of the state shifts leading to failure in the diagram are governed by the shapes of the thermodynamic potential curves, the liquid concentrations giving the potentials a minimum, the critical concentration and the breakdown concentrations here introduced. Various kinetic data of environmental stress cracking in low density polyethylenes can be understood by the unified picture. The predictions of the theory are also consistent with the reported kinetic nature of crazing.     

Flexible nanoscale co-continuous structures prepared by controlled crazing of ethylene-octene elastomers and in-situ polymerization of conductive networks

An approach based on controlled crazing and post-polymerization was used to incorporate a nanoscaled conductive co-continuous network into commercial ENGAGE™ Polyolefin Elastomers (POEs). Three POE films of differing crystallinity and phase morphology were stretched in a reactive mixture of acrylic polymerization precursors that possessed an affinity for the olefinic materials and acted as a surface-active agent for craze promotion. As a result, a rigid acrylic hydrogel phase was grown in the void space associated with crazing, which prevented the formed channels from collapsing after mechanical stresses were removed. The hydrogel phase offered ion conductivity properties to the POE. Simply replacing the acrylic monomer with an aniline emulsion for polymerization did not lead to the same outcome in terms of a continuous network; the materials became insulative after the removal of mechanical stresses due to fragmentation of the polyaniline channels from the unrestrained elastic relaxation of the POE. This problem was overcome by solution-casting POE with polycaprolactone (PCL) into films and, subsequently, partially dissolving and leaching PCL from the blend while a sample was stretched in an aniline emulsion medium containing formic acid. The residual PCL left in the crazes reinforced the polyaniline to prevent fragmentation, allowing the formation of a highly electron-conductive secondary phase.     

Variation of periodic crazing based on polymer blends of an ultra‐high and a low molecular weight poly(methyl methacrylate)

Periodic crazes are caused in a polymer film by the unique mechanical method using bending. Generation of a craze depends on entanglements of the molecular chains of a polymer. Therefore, control of composite morphology of periodic crazes was attempted by varying the entanglements of molecular chains. An effective entanglement network became sparse by polymer blends of an ultra‐high molecular weight polymethylmethacrylate (PMMA) and a low molecular weight PMMA. Consequently, the composite morphology of periodic crazes caused in the blend film varied. In other words, the periodic craze can be used for the evaluation of the effective entanglements. In addition, it was figured out that PMMA of which the number‐average molecular weight (M_n) is less than twice of the effective entanglement molecular weight (M_e^*) works as a plasticizer in the blend film. And also, it was revealed that the mechanical properties of the blend film decreased dramatically at M_n ≒ 6M_e^*. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44332.     

The effect of high pressure processing on the morphology of polyethylene films tested by differential scanning calorimetry and X‐ray diffraction and its influence on the permeability of the polymer

This study investigated the influence of high‐pressure processing on the morphology and permeability of low‐density polyethylene (LDPE) films used for food packaging. This was done by monitoring the crystallinity, melting temperature (T_m), and oxygen transmission rate (OTR) of the materials before and after the pressure treatments. A first set of pouches made from the LDPE films were filled with 95% ethanol then pressured at 200, 400, 600, and 800 MPa for 5 and 10 min at 25 and 75°C. The crystallinity and T_m of the films were measured using differential scanning calorimetry (DSC). X‐ray diffraction (XRD) was also used to determine the crystallinity. A second set of LDPE pouches were similarly made but a half of them were filled with 95% ethanol and the other half filled with distilled water. These second set of pouches were pressured at 200, 600, and 800 MPa then their OTR tested. Results of the DSC experiments showed that the T_m increased with increasing pressure intensity but the crystallinity changes were not detectible. The XRD method on the other hand, showed significant (P < 0.05) crystallinity increases with increasing pressure treatments. The gas permeability analyses showed decreasing OTR's with increasing high‐pressure intensity treatments. The OTR in the pouches filled with the 95% ethanol was slightly lower than that of the pouches filled with water. These findings allowed us to better anticipate the behavior of LDPE films used to package high‐pressure processed foods. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis,film morphology,and performance on cotton substrates of dodecyl/piperazine functional polysiloxane

A novel polysiloxane bearing dodecyl and epoxy side groups (DESO) was synthesized as an intermediate through hydrosilylation of polymethylhydrosiloxane with allyl glycidyl ether and 1‐dodecene. Then, dodecyl/piperazine functional polysiloxane (DPSO) was prepared through the reaction of N‐aminoethylpiperazine with DESO. The chemical structure of DPSO was characterized with FTIR and ¹H‐NMR spectroscopy and its application performance on cotton fabrics was studied. DPSO with dodecyl side groups gifted the treated fabrics with good wettability and whiteness compared with piperazine functional polysiloxane, while with a slightly reduced softness as well as thickening handle. Film morphology, orientation, and performance on cotton substrates of DPSO were investigated by scanning electron microscope, atomic force microscopy, X‐ray photoelectron microscope, and so on. Affected by the dodecyl side groups, DPSO formed relatively hydrophilic, macroscopically smooth but actually uneven films with many dodecyl side chain pillars on the treated substrate surfaces. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40186.     

Poly(caprolactone) thin film preparation,morphology, and surface texture

The properties and surface uniformity of poly‐ (caprolactone) (PCL) thin films were measured. Thin films were prepared using a spin‐coating technique. Film thickness and roughness were correlated with variation in solution concentration, spinning speed and spinning time. Differential scanning calorimetry (DSC) was used to investigate the crystallization and melting processes. The enthalpy of melting variation correlated with the film thickness, while melting temperature was independent of film thickness. In addition, surface roughness was found to be a function of PCL thickness. Film thickness and roughness showed a progressive decrease when spinning speed was increased, while spinning time provided no significant influence on film thickness. PCL thickness and roughness significantly increased when PCL solution concentration increased. Hot stage optical microscopy showed that larger spherulitic crystals were present in thin films, and the smaller crystals present in thicker films had a coarser texture consistent with increased surface roughness. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1287–1294, 2007     

Formation of thermally induced craze and prevention by using infrared radiation annealing method

It is important to study the residual stress distribution and craze formation of transparent overmolded polymeric parts, because the overmolding can cause stress concentration near the interface region and the craze can be generated by the concentrated stress. Thermally induced crazing of an electric appliances product overmolded by using a transparent polymer is discussed in this study. Craze criterion was determined to be 20 MPa at the temperature higher than 60°C by using mechanical characteristic analysis of the polymeric material. Crazes were observed in the product annealed at over 60°C due to thermal residual stresses generated by the temperature difference between the surface and inside of the part upon surface heating. However, they were not observed in the product annealed by infrared radiation (IR) at over 60°C due to simultaneous heating throughout the thickness of the product. The numerical residual stress results were in good agreement with the experimental results, indicating that overmolding process, thermoviscoelastic stress development of the polymeric part, and IR annealing process were considered properly in the three-dimensional numerical analysis. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Influence of the thin‐film thickness and crystallization temperature on the spherulitic structure of polymer thin films

The spherulitic structure and morphology of poly(3‐hydroxybutyrate) (PHB) thin films crystallized from the melt were observed with a polarizing optical microscope. Depending on the thickness of the PHB thin film and crystallization temperature, banded and nonbanded spherulites could form. Reducing the thin‐film thickness and crystallization temperature was favorable for the formation of the banded structure. The morphology transition from banded spherulites to nonbanded spherulites was related to the ratio of the crystallization rate to the diffusion rate. The formation mechanism of the banded structure was examined with the discontinuity growth theory. A depletion zone was considered to appear periodically at the crystal growth front because of the slow diffusion rate, and this may have resulted in the banded spherulites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

In situ polyaniline film formation using ferric chloride as an oxidant

In situ polyaniline (PANI) films were grown from an aqueous hydrochloric acid solution on glass substrates via the chemical oxidation of aniline using hydrated ferric chloride, FeCl₃.6H₂O (FC). The effect of initial molar ratios of FC/aniline on the yield of PANI films was monitored using the quartz crystal microbalance technique. The morphology of the resultant polymer film and powder was examined using scanning electron microscopy. It was found that the film possesses a porous character; however, the polymer powder consists of small particles with interconnected nanofibers. The polymer powder formed in the bulk was characterized using the energy dispersive analysis of X-ray, the X-ray diffraction, and the thermal gravimetric analysis. A comparison between the PANI produced from FC and ammonium peroxydisulfate was considered and discussed. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Modeling and control of film porosity in thin film deposition

Systematic methodologies are developed for modeling and control of film porosity in thin film deposition. The deposition process is modeled via kinetic Monte Carlo (kMC) simulation on a triangular lattice. The microscopic events involve atom adsorption and migration and allow for vacancies and overhangs to develop. Appropriate definitions of film site occupancy ratio (SOR), i.e., fraction of film sites occupied by particles over total number of film sites, and its fluctuations are introduced to describe film porosity. Deterministic and stochastic ordinary differential equation (ODE) models are also derived to describe the time evolution of film SOR and its fluctuation. The coefficients of the ODE models are estimated on the basis of data obtained from the kMC simulator of the deposition process using least-square methods and their dependence on substrate temperature is determined. The developed ODE models are used as the basis for the design of model predictive control (MPC) algorithms that include penalty on the film SOR and its variance to regulate the expected value of film SOR at a desired level and reduce run-to-run fluctuations. Simulation results demonstrate the applicability and effectiveness of the proposed film porosity modeling and control methods in the context of the deposition process under consideration.     

Effects of the film thickness on the morphology,structure, and crystal orientation behavior of poly(chloro‐p‐xylylene) films

Poly(chloro‐p‐xylylene) (PPXC) films with a thickness range encompassing more than three orders of magnitude (from 10² nm to 10² μm) were prepared on Si substrates by the chemical vapor deposition method under the same conditions. The effect of the film thickness (d) on the morphology, crystal structure, and crystal orientation behavior of the PPXC films was studied. The average roughness of the root mean square (rms) of the films increased with increasing d according to a power law (rms ≈ d^β, where β is an exponent that depends on the film growth process over time and β = 0.240±0.005, as probed by atomic force microscopy), and the monomer diffusion and relaxation of polymer were suggested as the primary factors governing this morphological evolution. The X‐ray diffraction results indicate that both the crystallinity and crystal size of PPXC increased with increasing d due to the surface confinement effect between the film and the substrate, which retarded the crystallization process. The X‐ray pole figures suggested that the (020) fiber textures with the b axis parallel to the Si substrate normal existed in the PPXC films; these fiber textures, mainly composed of edge‐on crystal lamellae, were thermodynamically favored. The Herman's orientation factor of the fiber textures increased gradually as d grew; this indicated that stronger (020) fiber textures with higher concentrations of edge‐on lamellae existed in the thicker PPXC films. This thickness dependence of the crystal orientation behavior was interpreted to be caused by the strong adhesion between the polymer chains and the substrate. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41394.     

Effect of TiO2 on morphology and mechanical properties of PVDF/PMMA blend films prepared by melt casting process

Effect of titanium dioxide (TiO₂) on morphology and mechanical properties of poly(vinylidene fluoride) (PVDF)/poly(methyl methacrylate) (PMMA) blend films prepared at different TiO₂ contents by a melt casting process was studied. The results showed that tensile moduli in both the machine direction (MD) and the transverse direction (TD) increased with increasing TiO₂ content, and calculated tensile moduli based on the Halpin–Tsai and the Kerner model were consistent with experimental ones in both the MD and TD of films containing 10 wt % TiO₂. However, experimental tensile moduli exhibited smaller values compared with calculated ones, as the TiO₂ content increased to 30 wt %_, and it was assumed that this is due to the decrease of crystallinity of PVDF. Morphological observations indicated that TiO₂ particles did not affect crystal structures of PVDF and the morphology of PVDF/PMMA amorphous phase, but hindered the crystallization of PVDF. The MD and TD elongation at break exhibited >200 and <20%, respectively. The SEM micrographs revealed that spherulites could deform along the MD when the tensile force was applied along the direction. By contrast, spherulites could not deform along the TD and fractured at very small elongation, owing to the anisotropic morphology of spherulites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40454.     

Characterization and properties of LDPE film with gallic‐acid‐based oxygen scavenging system useful as a functional packaging material

We prepared and characterized active, oxygen‐scavenging, low density polyethylene (LDPE) films from a non‐metallic‐based oxygen scavenging system (OSS) containing 1, 3, 5, 10, and 20% of gallic acid (GA) and potassium chloride (PC). We compared the surface morphology and mechanical, permeability, and optical properties of the oxygen‐scavenging LDPE film with those of pure LDPE film. The surface morphology, gas barrier, and thermal properties indicate that the OSS was well incorporated into the LDPE film structure. The surface roughness of the film increased with the amount of oxygen scavenging material. The oxygen and water vapor permeability of the developed film also increased with the amount of oxygen scavenging material, though its elongation decreased. The oxygen scavenging capability of the prepared film was analyzed at different temperatures. The initial oxygen content (%) in the vial headspace, 20.90%, decreased to 16.6% at 4 °C, 14.6% at 23 °C, and 12.7% at 50 °C after 7 days of storage with the film containing 20% OSS. The film impregnated with 20% organic oxygen scavenging material showed an effective oxygen scavenging capacity of 0.709 mL/cm² at 23 °C. Relative humidity triggered the oxygen scavenging reaction. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44138.     

Hydrophobic cotton fabric coated by a thin nanoparticulate plasma film

The audio frequency (AC) plasma of some kind of fluorocarbon chemical was applied to deposit a nanoparticulate hydrophobic film onto a cotton fabric surface. The measurement of the video contact angle showed that the superhydrophobicity of the cotton fabric was obtained with a treatment of only 30 s. The softness, water retention, moisture regain, color retention, abrasion, friction, and permeability were thoroughly investigated by a standard method that compared the fabric with a commercial Scotchgard‐protector‐sprayed cotton fabric. The results showed that the textile performances of the plasma‐coated fabric were superior to those of Scotchgard‐sprayed samples, except for the moisture regain, which was almost the same. A post‐treatment at a high temperature was conducive to increasing the hydrophobicity and the recovery of the water repellency of the plasma‐coated fabric after it was washed. Atomic force microscopy images and time‐of‐flight secondary‐ion mass spectra of plasma thin films on silicon wafers indicated that some physical and chemical changes took place during the post‐treatment process. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1473–1481, 2003     

Influences of molecular weight and particle morphology on film processing properties of polyvinyl fluoride

To select a suitable kind of resin for preparing films, the melting point (T_m), thermal decomposition temperature (T_d), and stretch property of polyvinyl fluoride (PVF) as a function of the viscosity–average molecular weight (M_η) were investigated. The results showed that T_d and maximal stretch ratio of extrusion‐cast PVF films gradually increase with the increase of M_η. T_m also increases when M_η is below 400,000, but keeps invariable when M_η is beyond 400,000. Six different kinds of PVF resin samples in this article were classified into three types, according to their particle morphologies: (1) loose‐structured PVF (PVF‐A and G); (2) tight‐structured PVF (PVF‐F); and (3) intermediate‐structured PVF (PVF‐B, E, and H). The effects of the morphology on the solvent absorbability of PVF were studied. The results indicated that the loose‐structured PVF has better absorption capacity to solvent than does tight‐structured PVF. The processing temperature can be considerably reduced when N,N‐dimethylformamide (DMF) as a plasticizer was mixed with PVF, and the diminished magnitude depends on the absorption capacity of PVF to DMF. The evaporation of DMF is influenced by both molecular weight and particle morphology of PVF, and the final residue of DMF in the PVF/DMF mixture is dependent on the molecular weight of PVF. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1780–1786, 2006     

Effect of temperature and film thickness on structural and mechanical properties of c-axis oriented Zn0.95Mg0.05O thin films

Zn_0.95Mg_0.05O solutions were synthesized by the sol-gel technique using Zn and Mg-based alkoxide. The structure, microstructure, and mechanical properties of the c-axis oriented Zn_0.95Mg_0.05O thin films were investigated as a function of film thickness and temperature. Zn_0.95Mg_0.05O thin films were grown on a glass substrate using the sol-gel dip-coating method. Then, the thin films were annealed at various temperature values (500–600 °C for 30 min) under air. X-ray diffraction of the Zn_0.95Mg_0.05O thin films results indicated that all samples had a ZnO wurtzite structure and (002) orientation. The photoluminescence (PL) measurements revealed the near-band emission (NBE), the Zn_i related emission, and the excess oxygen interstitials and their complexes with zinc vacancies. The surface morphologies and microstructure of all samples were characterized by using Scanning Electron Microscope (SEM). It was observed that surface morphologies of Zn_0.95Mg_0.05O thin film were dense, uniform, crack free and without pinhole. Effects of film thickness and temperature on stress in Zn_0.95Mg_0.05O thin films were analyzed theoretically to see whether there was any crack inside of the thin films and substrate or not. It was found that the stress component values of thin films were compressive; however, for glass substrate they were tension.     

Pattern formation by dewetting of polymer thin film

Strategies for the utilization of dewetting of polymer thin film to fabricate ordered patterns are reviewed. After a brief introduction to the polymer thin film dewetting theory, simulation results of pattern formation induced by physically and chemically patterned substrates, and physical confinement are then summarized. Experimental results including the mechanisms behind and the conditions for good quality of pattern formation based on the dewetting of polymer thin film induced by physical, chemical heterogeneous substrates, topographic structure on film surface, physical confinement and the movement of three-phase line are then discussed. A short introduction to the application of fabricated patterns is also discussed.     

Suppressing the non-switching contribution in BiFeO3-Bi4Ti3O12 based thin film composites to produce room-temperature multiferroic behavior

Exploiting the exceptional multiferroic characteristics of BiFeO₃-based systems depends largely on controlling the high leakage currents that often constrain the ferroelectric response of this material. This limiting circumstance is even more restrictive in the film geometry, where the high area/volume ratio can add complications related to the uncontrolled loss of a particularly volatile element such as bismuth. In this work we address the suppression of such non-switching contribution by preparing BFO-BiT thin film composites and using a low-temperature processing protocol in a fully aqueous medium. With an adequate and systematic doping of both oxides, the produced composites show both magnetic and ferroelectric response at room temperature, in a process that is also related to the fine matching between the two crystal lattices involved. The results obtained further indicate the possibility of applying a simple, sustainable protocol with high scalability prospects to fabricate exploitable multiferroic systems, i.e. with no need for large energy inputs nor sophisticated equipment.     

复配对有机硅整理剂成膜形态与应用性能的影响

采用原子力显微镜(AFM)和接触角滴定技术,研究了N-β-氨乙基-γ-氨丙基聚二甲基硅氧烷(ASO)和侧链聚醚/环氧基聚硅氧烷(CGF)溶剂共混组装膜(ASO/CGF)和乳液共混组装膜(AS/CGF)的微观表面形貌、亲疏水性能和其在纯棉织物上的应用性能。结果表明,ASO/CGF膜和AS/CGF膜均存在明显的相分离,其膜的分散相由CGF中聚醚链段吸水团聚堆积而成,连续相为聚二甲基硅氧烷链段(PDMS)。因受到乳胶粒子的限制,AS/CGF膜的相分离特征较ASO/CGF膜明显减小,膜的粗糙度也随之减小,亲水性增加。整理剂的组装膜性能数据可在一定程度反映整理剂的应用性能,对实际应用具有指导和借鉴意义。