Multi-layer films

Metallocene-catalysed very low density polyethylene (m-VLDPE) has become available with densities of as low as 0.903. This is of use for sealing layers of multi-layer films since sealing can commence at lower temperatures than with conventional materials such as LLDPE and EVA (see Section 11.6) with the polymer seal exhibiting both cold strength and hot tack strength. 

Due to their well defined geometrical sizes, globular shapes, and uniform multiple surface functional groups, dendrimers are promising candidates for the construction of mono- or multi-layer films. 

Arachidic acid monolayers were prepared from a benzene solution on the water subphase of pH5.8(pure water) and 12.6(adjusted by addition of NaOH) at Tsp of 303 K below Tm(=328 K) of the monolayer [31]. The ionic dissociation state of hydrophilic group was estimated on the basis of the stretching vibrations of carbonyl and carboxylate groups by Fourier transform-infrared attenuated total reflection, FT-IR ATR measurements. 70 arachidic acid monolayers were transferred on germanium ATR prism, resulting in the formation of the multi-layered film. Transfer on the prism was carried out at surface pressures of 25 or 28 mN-nr1. Infrared absorption measurements revealed that almost carboxylic groups of arachidic acid molecules did not dissociate on the water subphase of pH5.8, whereas all carboxylic groups dissociated as carboxylate ions on the water subphase of pH 12.6. 

Fig. 20.1. MAC Mode AFM three-dimensional images in air of (A) clean HOPG electrode (B) thin-film dsDNA-biosensor surface, prepared onto HOPG by 3 min free adsorption from 60 pg/mL dsDNA in pH 4.5 0.1 M acetate buffer (C) multi-layer film dsDNA biosensor, prepared onto HOPG by evaporation of three consecutive drops each containing 5pL of 50 pg/mL dsDNA in pH 4.5 0.1 M acetate buffer (D) thick-film dsDNA biosensor, prepared onto HOPG by evaporation from 37.5mg/mL dsDNA in pH 4.5 0.1M acetate buffer. With permission from Refs. [28,29].

In the case of multi-layered films commonly used as packaging material, we can calculate the permeation coefficient PC for the composite membrane using... 

Pressure flow of two immiscible fluids with different viscosities that flow as separate layers between parallel plates are often encountered inside dies during co-extrusion when producing multi-layer films. Such a system is schematically depicted in Fig. 6.16, which presents two layers of thickness h/2 and viscosities m and //,2, respectively. 

Multi-layer films can be produced, composed of different polymers. For each polymer a separate extruder is applied the extruders discharge into an accumulator, in which the separate streams are guided to their own position in the film. A laminated film can thus be made, in which one of the layers provides the strength, another one acts as a gas barrier, other layers promote adhesion and weldability, etc. This laminating process is applied with flat film extrusion as well as with film blowing. 

Nonlinear polymers in which second harmonic active molecules are incorporated into a polymer matrix offer interesting possibilities for waveguide SHG by virtue of their fabrication technology. The multi-layer films needed for waveguiding can be fabricated by simple spinning techniques already in use for decades in the electronics industry, and systematic calibration of the process al-... 

This is becoming known by the above name but the name used in the seminal papers of Curme et al. and Spayd et al. of Eastman Kodak Company is multi layer film elements for clinical analysis 44-45). It is a technique which unites two aspects of clinical analysis. One is the procedure for carrying out quantitative tests on fibre strips. These strips may be dipped into a sample of urine and instantly reveal the concentration of up to 8 basic components it is an elegant variation of indicator paper. The other aspect is the increasing use being made of biological methods, particularly enzyme methods for clinical analysis. 

As shown in Fig. 10, this experimental arrangement reveals significant differences in the NSOM fluorescence images following excitation of the donor dye in the multi-layer film and monitoring either the donor dye fluorescence or the fluorescence from the tip-bound acceptor dye. Fluorescence from the donor dye (left) reveals domains in the multi-layer film that contain the donor dye but is... 

Fig. 10. (Top) Schematic of the experimental arrangement for carrying out NSOM/ FRET measurements. An acceptor dye of a FRET pair is attached to the NSOM probe while the sample contains the donor dye in the bottom and top layers of a multi-layer film. The left fluorescence image shows the donor fluorescence and the right the fluorescence from the tip-bound acceptor dye. Reproduced with permission from Ref. [26]. Copyright 1999 The Biophysical Society.

Products composed of more than one type of plastic, either monocomponent, such as multi-layer films or laminates, or multi-components, such as plastic bottles and caps. 

E278 Nakamura, H., Kosaka, A. and Kidani, Y. (1986). Measurement of delta-bilirubin in serum with multi-layered films. Anal. Sci. 2, 203-204. 

FIGURE 11.1 Electron diffraction patterns of the linear chain carbon films (a-c), the distribution of electron diffraction intensity, its atomic arrangement (g), the Langmuir-Blodgett multi-layered film diffraction patterns (d,e). 

Blends of polyamide copolymers with butyl acrylate copolymers (Durethan C, with PA being a copolymer of e-caprolactam and other monomers) can be blown into films. The recommended processing conditions are screws having L/D = 25-33 and compression ratio = 3.5-4.0, barrel feed zone at T = 225-260°C and melt temperature of T = 250-280°C. For multi-layer films, adhesion between layers can be achieved either by addition of an adhesion promoter to either of the two materials or (preferably) by co-extrusion with an adhesive layer. 

Two examples of the use of localised thermal analysis are provided in order to illustrate the generic applications of this approach. Figure 8 shows localised thermomechanical analysis of the surface of the multi-layer film in Figure 4. Measurements were made at points within this image describing the bulk polymer, the central gas-barrier layer and the thin tie-layer between this and the bulk film. The melting transition temperatures are consistent with high density polyethylene, poly(ethylene-co-vinyl alcohol) and medium density polyethylene for the bulk, gas barrier and tie layers, respectively [101],... 

Figure I 1.3 Variation of gas pressure through a single polymer film, and a multi-layer film, in which the three polymers have different permeabilities, for steady-state gas flow.

Biaxial orientation is often used to improve the in-plane tensile strength and toughness of polymer films. The crystallinity of PET increases on stretching (Fig. 8.16), so the permeability decreases. For multi-layer films made by coextrusion or coating, the total permeability Ptot is related to the layer value... 

Electrodes and cell components must be thin to minimise the internal resistance of the batteries the total cell can be less than 0.2 mm thick. Figure 12.11 shows the construction of a multi-layer film, rechargeable lithium polymer battery, using a solid polymer electrolyte. A thin lithium metal foil acts as an anode. The electrolyte is polyethylene oxide containing a lithium salt, and the cathode is a composite of the electrolyte and a... 

F. Estrany, R. Ohver, E. Armelin, H.I. Iribaren, F. Liesa, and C. Aleman, Electroactive properties and electrochemical stability of poly(3,4-ethylenediox3dhiophene) and poly(n-methylpyrrole) multi-layered films generated by anodic oxidation. Port. Electrochim. Acta, 25, 55-65 (2007). 

Ogi, T., H. Ohkita, S. Ito, and M. Yamamoto (2002). Preparation of porphyrin mono-and multi-layer films based on the polymer Langmuir-Blodgett method. Thin Solid Films 415, 228-235. 

Pre-consumer, industrial scrap represents a possible exception to the product quality issue. As one example, the edge trim from multi-layer film cannot be reworked using existing technology. Approximately 25% of the purchased raw materials used for multi-layer films are now burned or buried. This scrap represents a known and controllable feedstock for the selective dissolution process. The component polymers can be recovered in pristine form. Many have values upwards of US 4.00 per kg. 

Two newly synthesized polyelectrolytes functionalized polymers with branehed side ehains bearing electron donor-acceptor type azobenzene ehromophores were used as polyanions to build up multi-layer films through an eleetrostatie sequential adsorption process... 

As cited in Guilbert and Gontard, 2005 [3], agro-polymers that have been proposed to formulate edible films or coatings are numerous (Cuq et at, 1995 Guilbert and Cuq, 1998). Plant polysaccharides such as cellulose and derivatives are used in various forms (simple or composite materials, single-layer or multi-layer films). The formulation of bioplastic or edible films implies the use of at least one component able to form a matrix having sufficient cohesion and continuity. They are polymers, which under preparation conditions, have the property to form crystalline or amorphous continuous structures [3]. 

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