Tie-layer

Various processing conditions can require the tie resin to fall into a particular melt index (MI) classification. MI is inversely related to molecular weight (MW) (see Chapter 1) a high-MW adhesive will have a low MI. Most adhesive are available in a range of Mis to meet different requirements. 

The melt stability or flow is easily influenced by regrind. It is important that the regrind be compatible with the adhesive. 

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Skin layer Tie layer Barrier layer Tie layer... 

Hypalon CP 826. This is a chloriaated, maleic anhydride modified polypropylene having a chlorine content of about 25% and maleic anhydride content of about 0.8%, developed to promote adhesion of inks and coatiags to polypropyleae or bleads containing polypropyleae. It has a solutioa viscosity of 125 mPas(= cP) at 20% soHds ia xyleae and can be used ia dilute solutioas as a wash primer or a tie layer betweea materials that are difficult to adhere. CP 827 is a higher molecular-weight analogue with a solution viscosity of 280 mPas(= cP) at 20% soHds ia 80/20 xylene/methyl isobutyl ketoae. 

The coating is applied to protect the steel from corrosion due to the acid or alkaline condition of the soil surrounding the pipe in service. Usually, the process requires three layers. First, an epoxy powder is applied to achieve adhesion to the pretreated metal and therefore resistance to cathodic disbondment. Second, a tie layer of polyolefin copolymer is applied and third a thick layer of polyethylene is cascaded, which in effect protects the epoxy from physical damage. 

What is the role of a tie layer in processes which create multilayer films ... 

Figures 21(a) and 21(b) show the SEM micrographs of the freeze-fractured cross-section of the film used in the construction of the bag. There are two distinct layers and possibly a third very much thinner tie layer. The outside layer is a layer of nominal thickness 13 pm. The inside layer is much thicker and is approximately 70 pm thick. At the interface between the outer and inner layers the apparent very thin tie layer is about 1 pm thick. This is too thin to be identified by FUR microscopy on a cross-section of the sample, since the technique is diffraction-limited, which means that layers of about 10 pm thickness or greater can only be readily identified [1]. The tie layer thickness is also probably too thin for fingerprinting by Raman microspectroscopy on a cross-section the lateral spatial resolution of Raman microspectroscopy is about 1-2 pm.

From the analyses carried out, the conclusion is that the dispensing bag is comprised of three layers an inner polyethylene-based layer, an outer polyamide layer, and what appears to be a third, very thin, tie layer. The polyethylene in the inner layer has approximately 14 branches per 1,000 carbons and is... 

Figure 65 SEM images (a) and (b) cross-sections of the good package white backing film, (c) and (d) cross-sections of the bad package white backing film. (A) Outer clear polyester layer, (B) tie layer, (C) middle opaque polyethylene layer, and (D) EVA heat seal layer.

The ATR-FTIR spectrum of the middle opaque polyethylene layer of the "bad" sample is shown in Figure 70. This spectrum was acquired from the fracture surface where the outer polyester film and tie layer delaminated from the polyethylene layer. The highest-scoring library match in Figure 70 indicates that the middle layer is a polyethylene with a low branch content, most likely a HDPE or a LLDPE, although a much more detailed spectral analysis would be required to confirm this. 

Multi-layer sheets for use in the mannfacture of food packaging containers were produced by the coextrusion of PP foam in combination with PE, an EVOH barrier layer and tie layers. Results are presented of studies of the mechanical and morphological properties, density and cell stmctnre of foam layers based on different types of PP. 8 refs. 

Multilayer sheets containing poly(chlorotrifluoroethylene) and COC for blister packaging applications have been described (63). In the production of the multilayered film, the fluoropolymer layer is joined with the thermoplastic polymer layer and an adhesive tie layer. 

The adhesive tie layer can be made up from 82% ethylene-based octene plastomer, 15% styrene modified terpene resin and 3% of a styrene/isoprene/styrene styrenic block copolymer. 

Thermoplastic multilayer laminate composed from an outer layer of resorcinol arylate poly(ester)s, a middle layer comprising a polycarbonate), e.g., LEXAN 131, and an inner-tie layer made from ASA or ABS have been described (37). Resorcinol arylate poly(es-ter)s may be understood as an isophthalic terephthalic resorcinol bisphenol A copolymer. 

Adhesives and Sealants. Dominated by copolymers, adhesives and sealants remain somewhat of a specialty market. These polymers usually contain high copolymer content and low viscosity, and often require blending with oilier compounds prior to final application. Their uses are numerous, e.g., as seals for bottled drinks, as tie layers between incompatible polymers, or as automotive adhesives... 

THV Fluoroplastic can be readily bonded to itself and to many plastics and elastomers and unlike other fluoroplastics does not require surface treatment, such as chemical etching or corona treatment. However, in some cases tie layers are required to achieve a good bonding to other materials.92... 

PVDF can be coextruded and laminated, but the process has its technical challenges in matching the coefficients of thermal expansion, melt viscosities, and layer adhesion. Special tie-layers, often from blends of polymers compatible with PVDF, are used to achieve bonding.26-27... 

Coextrusion produces multilayer laminates in a single process step. Two or more extruders feed different molten polymers into a multi-manifold die which layers them directly, or into a modular feedblock which layers them before feeding them into the die. This is used primarily in the packaging field, to sandwich an impermeable barrier layer between two commodity outer-film layers, and often includes adhesive tie layers to bond the barrier layer to the outer layers. 

When no bonding layers occur in a plastic laminated composite structure, a plastic tie-layer is used that provides bonding. Choosing the proper adhesive layer is by no means a simple task since evaluation includes processability, bonding capabilities, and performance in the final product. There are many different types with different capabilities, with EVOHs being one of the important ones. 

Nodax C4/C6 is said to be a natural fit for injection moulding and extrusion of sheet or film. The polymer has mechanical properties similar to a polyolefin and surface properties much like PET, including high receptivity to printing inks and dyes. Adhesion to LDPE and PP is good enough to avoid tie layers in multi-layer structures. Nodax s oxygen barrier property approaches that of EVOH. 

Title Photochemical Crosslinkers for Polymer Coatings and Substrate Tie-Layer... 

Flexible packaging laminates Chemically reactive systems water-based hot-melts tie-layers Indirect... 

Tie-layers are used as binding layers in some multilayer materials that are produced without any lamination adhesives. Tie-layers are formed by applying a co-extrudable resin, which is usually a polymer modified with active functional groups to make it adhere to the other substrates. 

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