LLDPE‐based mono‐ and multilayer blown films: Effect of processing parameters on properties

In this study we investigated the effect of processing parameters on the end‐use properties of mono‐ and five‐layer coextruded polyethylene (PE) blown films using three different linear low‐density PE (LLDPE) resins. The three investigated LLDPEs were a conventional Ziegler‐Natta gas phase ethylene‐butene copolymer, and two solution ethylene‐octene resins produced with Ziegler‐Natta and single‐site catalysts. The octene copolymers were produced using NOVA Chemicals Advanced SCLAIRTECH? process and catalyst technologies. It was found that within the investigated range of processing conditions, tear strength increased in the direction perpendicular to the highest orientation, impact and puncture strength increased with the overall orientation, and the effect of orientation due to shear stresses in the die was negligible because of rapid macromolecular relaxation before crystallization. Finally, it was also shown that due to changes in the size of the crystallites, haze increased with die gap and frost line height (FLH), and decreased as take‐up speed (TUS) increased. POLYM. ENG. SCI., 45:1214–1221, 2005. © 2005 Society of Plastics Engineers     

Triple‐shape‐memory polymer films created by forced‐assembly multilayer coextrusion

Triple‐shape‐memory polymers are capable of memorizing two temporary shapes and sequentially recovering from the first temporary shape to the second temporary shape and eventually to the permanent shape upon exposure to a stimulus. In this study, unique three‐component, multilayered films with an ATBTA configuration [where A is polyurethane (PU), B is ethylene vinyl acetate (EVA), and T is poly(vinyl acetate) (PVAc)] were produced as a triple‐shape‐memory material via a forced‐assembly multilayer film coextrusion process from PU, EVA, and PVAc. The two well‐separated thermal transitions of the PU–EVA–PVAc film, the melting temperature of EVA and the glass‐transition temperature of PVAc, allow for the fixing of the two temporary shapes. The cyclic thermomechanical testing results confirm that the 257‐layered PU–EVA–PVAc films possessed outstanding triple‐shape‐memory performance in terms of the shape fixity and shape‐recovery ratios. This approach allowed greater design flexibility and simultaneous adjustment of the mechanical and shape‐memory properties. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44405.     

Recycled milk pouch and virgin LDPE‐LLDPE‐based jute fiber composites

The present investigation deals with the thermo‐mechanical recycling of post consumer milk pouches (LDPE‐LLDPE blend) and its use as jute fiber composite materials for engineering applications. The mechanical, thermal, morphological, and dynamic‐mechanical properties of recycled milk pouch‐based jute fiber composites with different fiber contents were evaluated and compared with those of the virgin LDPE‐LLDPE/jute fiber composites. Effect of artificial weathering on mechanical properties of different formulated composites was determined. The recycled polymer‐based jute fiber composites showed inferior mechanical properties as well as poor thermal stability compared to those observed for virgin polymer/jute fiber composites. However, the jute‐composites made with (50:50) recycled milk pouch‐virgin LDPE‐LLDPE blend as polymer matrix indicated significantly superior properties in comparison to the recycled milk pouch/jute composites. Overall mechanical performances of the recycled and virgin polymeric composites were correlated by scanning electron microscopy (SEM). The dynamic mechanical analysis showed that storage modulus values were lower for recycled LDPE‐LLDPE/jute composites compared to virgin LDPE‐LLDPE/jute composites throughout the entire temperature range, but an increase in the storage modulus was observed for recycled‐virgin LDPE‐LLDPE/jute composites. POLYM. COMPOS. 28:78–88, 2007. © 2007 Society of Plastics Engineers     

Oxygen enrichment from air through multilayer thin low‐density polyethylene films

Several multilayer thin low‐density polyethylene (LDPE) films were fabricated by blown thin film having a thickness of 7 μm and an area of 130 cm². They were characterized for their oxygen‐enrichment performance from air by a constant pressure–variable volume method in a round permeate cell with an effective area of 73.9 cm². The relationship between oxygen‐enrichment properties, including oxygen‐enriched air (OEA) flux, oxygen concentration, permeability coefficients of OEA, oxygen, nitrogen, as well as separation factor through the multilayer LDPE films, and operating parameters, including transfilm pressure difference, retentate/permeate flux ratio, temperature, as well as layer number, are all discussed in detail. It is found that all of the preceding oxygen‐enrichment parameters increase continuously with an increase of transfilm pressure difference from 0.1 to 0.65 MPa, especially for the trilayer and tetralayer LDPE films. The oxygen concentration and separation factor appear to rapidly increase within the retentate/permeate flux ratio below 200, and then become unchangeable beyond that, whereas the OEA flux and the permeability coefficients of OEA, oxygen, and nitrogen seem to remain nearly constant within the whole retentate/permeate flux ratio investigated, especially for the monolayer and bilayer LDPE films. The selectivity becomes inferior, whereas the permeability becomes superior, as the operating temperature increases from 23 to 31°C. The highest oxygen concentration was found to be 44.8% for monolayer LDPE film in a single step with air containing oxygen of 20.9% as a feed gas and operating pressure of 0.5 MPa at a retentate/permeate flux ratio of 340 and 23°C. The results demonstrate a possibility to prepare an oxygen‐enriching membrane directly from air, based on the easily obtained thin LDPE films. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 3013–3021, 2002; DOI 10.1002/app.2331     

Morphology and properties of layered silicate‐polyethylene nanocomposite blown films

Film grade ethylene vinyl acetate (EVA), low density polyethylene (LDPE), and high density polyethylene (HDPE) were melt compounded with an organically modified montmorillonite, then blown into films. The morphology studies showed that all three types of film involve intercalated clay particles. The dependence of intercalation extent on the matrix as well as on the molecular weight of compatibilizers is discussed. The tensile testing data showed that the clay enhancing effects apply mainly to the modulus, instead of to the strength. The EVA‐based nanocomposite films exhibit the most significantly improved modulus while the HDPE‐based films have the least. Lower molecular weight compatibilizers could promote the clay enhancing effects while higher molecular weight compatibilizers could increase the matrix properties. Steady shear viscosities of an intercalated and an exfoliated system were also investigated. Comparing our data with that from the literature lead us to conclude that: 1) the zero‐shear viscosity of a nanocomposite is mainly determined by clay loading instead of by clay intercalation/exfoliation structures and the matrix viscosity; and 2) the clay orientation during a shear flow is highly dependent on the matrix flow behavior and to a lesser extent on the clay structural state. POLYM. ENG. SCI., 45:469–477, 2005. © 2005 Society of Plastics Engineers     

Gas transport and thermal characterization of mono‐ and di‐polyethylene films used for food packaging

The permeability of carbon dioxide, oxygen, nitrogen, and air through commercial monolayer and multilayer films, based on polyethylene (PE), biaxially oriented polypropylene (BOPP), and polyamide (PA), used for food packaging is reported. The influence of temperature (from 10 to 60°C) on permeability and DSC characteristics changes was also analyzed. Literature data for gas permeability of the mentioned monofilms are quite variable due to differences in additives, thermal history, and crystallinity. In this work, the highest gas permeability is obtained for PE film at the higher temperature (50–60°C). Laminates exhibit different gas permeation behavior from that of monofilms. Generally, gas solubility coefficient increases at higher temperature (with an exception of PA/PE and BOPPcoex.met/PE), being higher for monofilms in comparison with laminates, while diffusion coefficients are lower for monofilms in comparison with laminates. The temperature dependence of the permeability, diffusivity, and solubility of gases shows two different regions in PE, BOPPcoex/PE (10–40°C and 40–60°C), PA/PE, and BOPPcoex.met (10–30°C and 40–60°C) films. Correlation between activation energies for permeation and diffusion as well as heat of sorption and 17 gas properties is performed. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1590–1599, 2006     

Structure of blown films of polyethylene/polybutene‐1 blends

The structure of blown films of blends of low‐density polyethylene (PE‐LD) and isotactic polybutene‐1 (iPB‐1) with different content of iPB‐1 was investigated using wide‐ and small‐angle X‐ray scattering (WAXS and SAXS), transmission electron microscopy (TEM), and polarizing optical microscopy (POM). TEM proves formation of a matrix–particle phase structure due to immiscibility of the blend components. Within the iPB‐1 particles, needle‐like crystals with c‐axis orientation were observed. The PE‐LD matrix showed two populations of crystals. WAXS data indicate that the majority of crystals were oriented with the c‐axis perpendicular to machine direction (MD), while SAXS data prove additional presence of stacks of lamellae, oriented parallel to MD. Quantitative birefringence measurements showed that the majority of molecule segments were oriented in the direction of the circumference of the film, confirming the WAXS data. The crystal orientation has direct impact on mechanical properties, which was demonstrated by measurement of the anisotropy of the modulus of elasticity. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Fabrication of polysulfone asymmetric hollow‐fiber membranes by coextrusion through a triple‐orifice spinneret

Polysulfone (PSf) asymmetric hollow‐fiber membranes, which have a dense outer layer but a loose inner layer, were tentatively fabricated by coextrusion through a triple‐orifice spinneret and a dry/wet‐phase inversion process. Two simple polymer dopes were tailored, respectively, for the dense outer layer and the porous inner layer according to the principles of the phase‐inversion process. By adjusting the ratio of the inner/outer extrusion rate, the hollow‐fiber membranes with various thicknesses of outer layers were achieved. The morphology of the hollow‐fiber membranes was exhibited and the processing conditions and the water permeability of the membrane were investigated. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 259–266, 2004     

2‐Hydroxypropylmethacrylate based mono‐ and bifunctional gel beads prepared by suspension polymerization

Spherical and swellable gel beads in the size range 35–200 µm were prepared by suspension polymerization of 2‐hydroxypropylmethacrylate (HPMA). In the proposed method, a mixture of cyclohexanol and octanol was used as a diluent phase dispersed in an aqueous medium including poly(vinyl pyrrolidone) (PVP) as the stabilizer. The polymerization was initiated within the organic phase including the monomer and the crosslinker (ethylene glycol dimethacrylate) by an oil soluble initiator benzoyl peroxide. Spherical and swellable gel beads carrying both hydroxyl and carboxyl functional groups were also prepared by suspension copolymerization of HPMA and a water soluble comonomer (methacrylic acid). For this purpose, the suspension polymerization method proposed for HPMA was modified by using poly(vinyl alcohol) as a stabilizer instead of PVP. The effect of initiator concentration, polymerization temperature, monomer/diluent ratio, crosslinker concentration, stirring rate on yield, average size, size distribution, and carboxyl content of the HPMA based gel beads, were investigated. The swelling characteristics of the gel beads were defined. © 2000 Society of Chemical Industry     

Photoimaging technique on printing Al plate via self‐assembly multilayer films based on diazoresin

A photoimaging technique on a printing aluminum plate (anodized oxidation Al plate) via self‐assembly multilayer thin film from nitro‐containing diazoresin (NDR) as cationic polyelectrolyte and various anionic polyelectrolytes has been developed. It was confirmed that, under UV‐irradiation, the linkage nature of the films changes from ionic to covalent and the solubility of the films converts dramatically, that is, the exposed area of the film becomes insoluble in H₂O–DMF–LiCl (2 : 4 : 1 wt %) ternary solvent, but mainly the unexposed area will be dissolved. After developing in ternary solvent, an image that accepts ink easily appears on the printing Al plate. To resolve the ink‐stain problem, originating from a trace remainder of the NDR on the unexposed area of the Al plate, a surface modification technique by polyphosphoric acid, which reacts with NDR to form a hydrophilic surface, was developed. The thickness, homogeneity, and surface morphology of the multilayer film (on mica) determined by atomic force microscopy and UV‐vis spectra were also reported. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1983–1987, 2001     

Thermal and mechanical behavior of flexible polyurethane‐molded plastic films and water‐blown foams with epoxidized soybean oil

Water‐blown flexible polyurethane foams and molded plastic films were made by replacing 0 to 50% of Voranol® 4701 in the B‐side of foam and plastic film formulation by epoxidized soybean oil (ESBO). Physical properties of foams including density, 50% compression force deflection (CFD), 50% constant deflection compression (CDC), and resilience were determined. A dynamic mechanical spectrometer (DMS) and a differential scanning calorimeter (DSC) were used to characterize the hard segment (HS) and soft segment (SS) ratio and thermal properties of plastic. Various functional groups in both flexible polyurethane foam and plastic film were characterized using Fourier transform‐infrared spectroscopy with attenuated total reflectance (FTIR‐ATR). When increasing the ESBO content, both density and 50% CFD of water‐blown polyurethane foams decreased first, then increased. On the other hand, the 50% CDC and resilience of foams showed a sharp increase and decrease, respectively. When increasing the ESBO content, the peak of tan δ in DMS analysis and Δc_p in DSC analysis of plastic films both decreased indicating the hard segment increased and the soft segment decreased in plastic film, respectively. The FTIR‐ATR results also show the hydrogen‐bonded urethane group increased in plastic films with increasing ESBO content. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Polypropylene/polypropylene‐grafted acrylic acid blends for multilayer films: Preparation and characterization

Polypropylene (PP) was functionalized with acrylic acid (AA) and styrene (st) as a comonomer by means of a radical‐initiated melt‐grafting reaction. FTIR, ESCA, and ¹H‐NMR spectroscopies were used to characterize the formation of polypropylene grafted with acrylic acid (PP‐g‐AA) and polypropylene grafted with acrylic acid and styrene (PP‐g‐AAst). The content of AA grafted onto PP was determined by using volumetric titration. Blends of PP with 0–100 wt % of PP‐g‐AA were prepared by melt mixing. The effect of the modified polymer content on the surfaces of cast films was characterized through FTIR–ATR and ESCA analysis as well as contact‐angle, wetting‐tension, and ink‐adhesion measurements. The influence of the content of AA on the melting and crystallization temperature of PP was investigated by DSC. The contact angles of water on cast‐film surfaces of PP/PP‐g‐AA blends decreases with increasing modified polymer content and decreasing PP‐g‐AA molecular weight. A notorious improvement on wetting tension was observed with increasing modified polymer content and decreasing PP‐g‐AA molecular weight. From FTIR–ATR and ESCA spectra of the blends, a calculation was made of the carbonyl index on the films' surfaces. It was found that the higher the carbonyl index, the lower the contact‐angle value for the polypropylene blends. An increase in crystallization temperature of PP was observed when AA monomers were grafted into PP and with increasing PP‐g‐AA content in the blend, probably caused by a nucleation effect of AA monomers that would improve the crystallization capability of PP. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1497–1505, 2001     

Physical properties of water‐blown rigid polyurethane foams from vegetable oil‐based polyols

Fifty vegetable oil‐based polyols were characterized in terms of their hydroxyl number and their potential of replacing up to 50% of the petroleum‐based polyol in waterborne rigid polyurethane foam applications was evaluated. Polyurethane foams were prepared by reacting isocyanates with polyols containing 50% of vegetable oil‐based polyols and 50% of petroleum‐based polyol and their thermal conductivity, density, and compressive strength were determined. The vegetable oil‐based polyols included epoxidized soybean oil reacted with acetol, commercial soybean oil polyols (soyoils), polyols derived from epoxidized soybean oil and diglycerides, etc. Most of the foams made with polyols containing 50% of vegetable oil‐based polyols were inferior to foams made from 100% petroleum‐based polyol. However, foams made with polyols containing 50% hydroxy soybean oil, epoxidized soybean oil reacted with acetol, and oxidized epoxidized diglyceride of soybean oil not only had superior thermal conductivity, but also better density and compressive strength properties than had foams made from 100% petroleum polyol. Although the epoxidized soybean oil did not have any hydroxyl functional group to react with isocyanate, when used in 50 : 50 blend with the petroleum‐based polyol the resulting polyurethane foams had density versus compressive properties similar to polyurethane foams made from 100% petroleum‐based polyol. The density and compressive strength of foams were affected by the hydroxyl number of polyols, but the thermal conductivity of foams was not. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Interfacial polymerization of polyaniline and its layer‐by‐layer assembly into polyelectrolytes multilayer thin‐films

The layer‐by‐layer (LbL) self assembly deposition technique was used to prepare multilayer thin films of anionic polyaniline‐blend‐poly(sodium 4‐styrenesulfonate) (PANI‐PSS) and cationic poly(diallydimethylammonium chloride) (PDADMAC). Anionic polyaniline was prepared by the interfacial polymerization of aniline monomer in the presence of PSS which acted as template to provide water solubility. The PSS to PANI concentration ratios used in the synthesis step was found to have a major effect on the final PANI‐PSS synthesis, its self assembly and the electrical properties of the prepared films. The optical and electrical properties of the films were measured by ultraviolet‐visible spectroscopy (UV‐Vis) and a 4‐point probe setup, respectively while the thickness of the films was measured by atomic force microscopy (AFM). Results showed that the optimum condition for the film growth and optimal conductivity were obtained with different synthesis conditions. These results suggest that the PSS concentration used for interfacial synthesis of PANI must be finely tuned depending on the type of application aimed by the user. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Development of water‐blown bio‐based thermoplastic polyurethane foams using bio‐derived chain extender

Water‐blown bio‐based thermoplastic polyurethane (TPU) formulations were developed to fulfill the requirements of the reactive rotational molding/foaming process. They were prepared using synthetic and bio‐based chain extenders. Foams were prepared by stirring polyether polyol (macrodiol), chain extender (diol), surfactant (silicone oil), chemical blowing agent (distilled water), catalyst, and diisocyanate. The concentration of chain extender, blowing agent, and surfactant were varied and their effects on foaming kinetics, physical, mechanical, and morphological properties of foams were investigated. Density, compressive strength, and modulus of foams decrease with increasing blowing agent concentration and increase with increasing chain extender concentration, but are not significantly affected by changes in surfactant concentration. The foam glass‐transition temperatures increase with increasing blowing agent and chain extender concentrations. The foam cell size slightly increases with increasing blowing agent content and decreases upon surfactant addition (without any dependence on concentration), whereas chain extender concentration has no effect on cell size. Bio‐based 1,3‐propanediol can be used successfully for the preparation TPU foams without sacrificing any properties. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Self‐assembled multilayer films based on diazoresins studied by atomic force microscopy/friction force microscopy

The layer‐by‐layer self‐assembled NDR‐PSS (nitro‐containing diazoresin‐polysodium p‐styrenesulfonate) films were fabricated. The crosslinking structure formed from the conversion of ionic bond to covalent bond after UV irradiation, confirmed by small angle X‐ray diffraction. The roughness and microtribological properties of NDR‐PSS films were investigated by atomic force microscopy/friction force microscopy. The ordered multilayer films after photoreaction are better in microtribological performance than that of the monolayer film. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 631–638, 2000     

Extruded cylindrical strands: Mechanical properties correlated with the formation of biodegradable films through blown extrusion

The objective of this study was to determine the mechanical and viscoelastic properties of extruded cylindrical strands from biodegradable polymer blends and to verify the correlation of the blend properties with their capacity to form films in the blown extrusion process. The production of biodegradable films would only occur if the extruded strands showed adequate characteristics. The strands were produced by extrusion with blends containing starch, glycerol, and fatty acids (caproic, lauric, and stearic). These blends were compared with a standard formulation containing poly(butylene adipate‐co‐terephthalate) (PBAT), a biodegradable polymer. From the mechanical tension tests, the extruded strands containing fatty acids differed significantly from the standard one, it was not clear the possibility to establish a comparison between the mechanical properties of the extruded strands and the formation of films. The rheological tests indicated that the polymer blends presented the desired viscoelastic characteristics for the film formation by blown extrusion. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers     

Liquid degassing using mono‐dispersed and poly‐dispersed micron droplets

Liquid degassing using mono‐dispersed and poly‐dispersed micron droplets (148.6 and 264.8 µm) falling in an inert gas was studied experimentally and analytically in a laboratory setting. The system using poly‐dispersed droplets revealed an upper degassing limit of 93% when the inert gas to liquid flow ratio was above 15 and a fog‐type nozzle was used. Linear correlations of the Sherwood number to the Peclet number were derived for both systems of medium Reynolds numbers (10–100). The correlation for the mono‐dispersed droplets agreed well with the steady state mass transfer correlations that are available in literature, especially at small Peclet number situations. © 2012 Canadian Society for Chemical Engineering     

Oxygen transfer in co‐extruded multilayer active films for food packaging

Oxygen scavenger applications in flexible food packaging are still limited due to the difficulty to ensure scavenging activity during storage and throughout the product shelf life. To avoid fast inactivation of the scavenger, multilayer active structures can be realized by inserting the active layer between two or more inert layers. In this work, an unsteady‐state 1D reaction‐diffusion mass transfer model was developed for predicting and optimizing the barrier‐to‐oxygen performance and the physical configurations of the co‐extruded multilayer active films. The film configuration was a three‐layers structure composed of polyethylene terephthalate (PET) as external inert layers, and PET with a polymeric oxygen scavenger as the core reactive layer. Scavenging activity of the multilayer film increased with the reactive layer thickness. Oxygen absorption reaction at short times decreased proportionally with the thickness of the external layers. The most appropriate combinations of inert‐to‐active film thickness were studied and analyzed. © 2017 American Institute of Chemical Engineers AIChE J, 2017