Biaxially oriented sheets

Gray and McCrum735 used the Hashin-Shtrikman theory to explain the origin of the y relaxation in PE and PTFE, Maeda et al.745 have given exact analyses of several two phase models for semi-crystalline polymers and Buckley755 represented a biaxially oriented sheet of linear polyethylene by a two phase composite model. 

Dow s patented scrapless forming process is identified as the SFP process. An extruder produce a biaxially oriented sheet (Chapter 5). In turn the sheet is slit and cut into square blanks. These blanks are heated and pressed into circular disc with a lip. Immediately or latter after reheating, the disc is thermoformed into a shape such as a cup. 

Ptriysar . ovacor] Crystal or impact polystyrates used in iig. foam, inj. blow molding, extrusion, dinnerware, biaxially oriented sheet profiles, house-wares, cosmetic and medical incdding, consumer dectronics, molded ]dtg., toys, and as blending resin. 

Table 3.8. Tensile Properties of Biaxially Oriented Sheeting ...

Figure 3.3 A composite of biaxially oriented sheeting with perforated steel plates.Biaxially oriented sheeting. (2) Perforated stainless-steel plate.

Orthotropic n. Having three mutually perpendicular planes of elastic symmetry, as in composites having fibers miming in two perpendicular directions, or biaxially oriented sheet. If the fibers or orientation are unidirectional, the material is still orthotropic but also isotropic in the two directions perpendicular to the fibers or oriented polymer chains. Complete textile glossary. Celanese Corporation, New York. Brandrup J, Immergut EH (eds) (1989) Polymer handbook, 3rd edn. Wiley-Interscience, New York. 

Transverse direction n. (1) In extruding sheet or film, the direction of the width, crosswise to the direction of extrusion. (2) In a uniaxially oriented plastic, either direction perpendicular to the direction of orientation (stretching). In a biaxially oriented sheet, the direction perpendicular to both axes (the plane) of orientation. (3) In a fiber-reinforced laminate the thickness direction or, in a laminate with unidirectional reinforcement, either of the two directions perpendicular to the fiber lengths. 

FIG. 10 Dependencies of breakdown voltage of IPP foil on temperature. White extruded sheet gray biaxially oriented sheet. (Adapted from Ref 42.)... 

Shatter-Resistant, Rigid, Reinforced, Translucent Corrugated Sheet, Polyester, Acrylic or Combination Polystyrene, Biaxially Oriented Sheet and Film... 

If the sheet has been subjected to biaxial orientation during extrusion (see Section 14.2), heating above the deformation temperature will cause the sheet to shrink. A tight package can be made by wrapping an article in a biaxially oriented sheet followed by a brief heat treatment. Such shrink packaging with polypropylene film is widely used for everything from lettuce and meats to books and video tapes. 

Available as both film and sheet unless otherwise noted. All materials are available in PDA grades except for CTA, PVP, and PL EX = extrusion CL = calendering REG = regeneration CAST = casting BO = biaxial orientation. 

The basic methods for forming film or sheeting materials may be classified as follows melt extmsion, calendering, solution casting, and chemical regeneration. Of special note is the use of biaxial orientation as part of the critical manufacturing steps for many film and sheet products. 

Melt Extrusion. By far the most important method for producing film and sheeting materials reties on one or another of the various melt extmsion techniques (5). The main variations of melt extmsion are the slot (or flat) die-cast film process, the blown films process, and the flat die sheeting-stack process. These may be combined with one or more steps such as coextmsion wherein multilayer film or sheet is formed, biaxial orientation, and in-line coating (6). 

Biaxial orientation effects are of importance in the manufacture of films and sheet. Biaxially stretched poly(ethylene terephthalate) (e.g. Melinex),... 

In addition to orientation in one direction (mono-axial orientation), biaxial orientation is possible. This is achieved when sheet is stretched in two directions resulting in layering of the molecules. This can increase the impact strength, tensile strength and solvent cracking resistance of polymers and with crystalline plastics the polymer clarity may also be improved. 

Plastic films represent the largest worldwide market for plastics with practically all extruded (6). They are used to meet different performance requirements particularly for its major packaging market. Worldwide just for biaxial oriented (Chapter 8) polypropylene consumption is about 5 /2 billion lb. Their use includes tape, food, tobacco, and confectionery. Thermoforming film (and extruded sheets) is a major processing technique producing all kinds of products. 

The biaxially oriented PET sheets have been extensively studied with regard to their mechanical anisotropy and all nine independent elastic constants have been determined by a variety of experimental techniques 38,39). The complete set of compliances for a one-way drawn sheet of draw ratio 5 1 is shown in Table 7. It is interesting to note that these compliances clearly reflect the two major structural features, the high chain axis orientation and the preferential orientation of the benzene rings... 

Similarly, oriented crystallisation can be induced by stretching sheets or films of polymers in two directions simultaneously. The resulting materials have biaxially oriented polymer crystals. Typical examples of such materials are biaxially stretched poly(ethylene terephthalate), poly(vinylidene chloride), and poly (propylene). Since the oriented crystals do not interfere with light waves, such films combine good strength with high clarity, which makes them attractive in a number of applications. 

Patel et al. [70] in a recent publication have explored the adhesive action of the mbber-siUca hybrid nanocomposites on different substrates. The rubber-silica hybrid nanocomposites are synthesized through in situ silica formation from TEOS in strong acidic pH within acryhc copolymer (EA-BA) and terpolymer (EA-BA-AA) matrices. The transparent nanocomposites have been apphed in between the aluminum (Al), wood (W), and biaxially oriented polypropylene (PP) sheets separately and have been tested for peel strength, lap shear strength, and static holding power of the adhesive joints. 

The most common examples of uniaxially oriented materials include fibers, films, and sheets hot-stretched in one direction and composites containing fibers all aligned in one direction. Some injection-molded objects are also primarily uniaxially oriented, but most injection-molded objects have a complex anisotropy that varies from point to point and is a combination of uniaxial and biaxial orientation. 

ISO/TS 15874-7 2003 Plastics piping systems for hot and cold water installations -Polypropylene (PP) - Part 7 Guidance for the assessment of conformity ISO 17555 2003 Plastics - Film and sheeting - Biaxially oriented polypropylene (PP) films (available in English only)... 

ISO 1874-2 1995 Plastics - Polyamide (PA) moulding and extrusion materials - Part 2 Preparation of test specimens and determination of properties ISO 15987 2003 Plastics - Film and sheeting - Biaxially oriented polyamide (nylon) films. 

Espoo, Technical Research of Finland, 1998, pp.l03. 10 ins. 15/4/99. VTT Publn. 361 NEW TECHNOLOGY TO MANUFACTURE POLYPROPYLENE FOAM SHEET AND BIAXIALLY ORIENTED FOAM FILM Raukola J 1... 

Chicago, II., 29th Aug-2nd Sept.l993,p.403-6. 6A MULTILAYER EXTRUSION DIE GEOMETRY FOR THERMOFORMED POLYPROPYLENE FOAM SHEETS AND BIAXIALLY ORIENTED FOAM FILMS Raukola J Savolainen A Tampere,University of Technology (TAPPI)... 

The state of the art is a combination of linear low-density polyethylene (PE-LLD) with hmestone for diaper back sheets. By biaxial orientation, the balance of mechanical permeability requirements can be obtained. Because of its PE-like characteristics Ecoflex is a good choice for a biodegradable back sheet. Ecoflex provides a good regulatory basis for these applications because of the positive results of the primary skin irritation test according to OECD 404, as well as the guinea pig test according to OECD 406. 

With mixed aramid fibre/particulate flake compositions in polycarbonate, however, the previously mentioned processing operations significantly reduced the levels of fibre and flake orientation relative to corresponding observations with single particle compounds [167]. For example, in sheet extrusion and injection moulding, the flakes oriented perpendicular to the fibres losing their biaxial orientation parallel to the surrounding machine surfaces. 

Packaging applications are the most extensive. Meat, poultry, and egg containers arc thermoformed from extruded foamed polystyrene sheet. The fast-food market also accounts for a substantial amount of polystyrene for takeout containers where the insulation value of a foamed container is an advantage. Containers, tubs, and trays formed from extruded impact polystyrene sheets are used for packaging a large variety of food. Biaxially oriented polystyrene film is thermoformed into blister packs, meat trays, container lids, and cookie, candy, pastiy, and other food packages where clarity is required. 

Figure 14.22 plots the oxygen permeability of PET nonoriented sheets and biaxially oriented bottles as a function of the degree of crystallinity. Indeed, the effect of crystallinity is larger than that of biaxial orientation. But in practical terms, nonoriented sheets crystallize much more slowly than the biaxially oriented bottle walls, because deformation-induced orientation proceeds at higher rates at any temperature between Tg and Tm. That is, the schematically represented crystallization rate curve in Fig. 14.21 extends vertically upwards. 

Fig. 14.22 Oxygen permeability of nonoriented PET sheets and biaxially oriented PET bottles as a function of crystallinity. [M. Salame, paper presented at the Bev-Pak 1992 Conference, Atlanta, GA March 23-25 (1992).]...

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