Polyethylene ribbon

In all cases filaments (ribbons) of crystalline polyethylene have been observed similar to the pol)mierization with soluble catalysts in high concentration (117). The perfection of these crystals must be dependent as before on polymerization rate, polymerization site density, solvent power, molecular weights, and in the case of heterogenous catalysis also on the presence of a support surface. The best perfection was obtained by the room temperature polymerization of polyethylene on glass sup-... 

Prior to crosslinking, softer grades of elastomer compounds flow slowly, so these cannot be produced in a form that is unconstrained. A common intermediate form of such compounds is long, continuous ribbons that are dusted with a release agent and coiled. Sheets or other forms can also be hot-pressed, dusted, and shipped with release packaging that helps to separate the layers for subsequent processing. In still other cases, the elastomer compound is wrapped into polyethylene... 

Polyethylene terephthalate, also known as PETE or simply 1, is a form of polyester often used to make bottles and jars to contain food. When collected, it is ground up into flakes and formed into pellets. The most common use for recycled PETE is the manufacture of polyester carpets. But it may also be spun into a cotton-candy-like form that can be used as a fiber filling for pillows or sleeping bags. It may also be rolled into thin sheets or ribbons and used as tapes for VCRs or tape decks. Reuse to produce bottles and jars is also common. 

The adhesive transfer of organic plastics has some special features of it own. Makinson and Tabor [24] observed that polytetrafluoroethylene sliding on glass left transferred material on the counter surface in the form of lumps, ribbons, sheets or very thin films, depending on the rubbing conditions. Pooley and Tabor [25], who studied the transfer process more intensively, also reported the behavior of other polymers such as fluorocarbon copolymers, polyethylene, polypropylene, polystyrene, polymethylmethacrylate and polyvinyl chloride. Descriptions of transfer in relation to wear were reported for PTFE by Tanaka tt ai. [20] and for polyethylene by Miller a.1. [21]... 

The ribbon was placed between two split billet halves of the same polyethylene, and the assembly coextruded through conical brass dies which had an included entrance angle of 20 and nominal extrusion draw ratios, EDR, of 12, 25, and 30. No lubricant was used. The EDR calculated from the displacement of the line mark was in good agreement with the nominal EDR defined as the ratio of entrance to exit cross-sectional area of a die. The extruded films were used only for the evaluation of the effect of deformation components on the resultant morphology and properties. The semiperipheral coextrudates obtained simultaneously from the extruded assembly were used for the x-ray study of the deformation mechanism for extrusion drawing. 

The plastics mass fed to the calender may be simply a heat-softened material, as in the case of, say, polyethylene, or a rough sheet, as in the case of PVC. The polymer PVC is blended with stabilizers, plasticizers, etc., in ribbon blenders, gelated at 120°C-160°C for about 5-10 min in a Banbury mixer, and the gelated lumps are made into a rough sheet on a two-roll mill before being fed to the calender. 

Polypropylene film fiber is becoming of great commercial interest in many applications such as carpeting and woven sacks. It consists of an extruded film that is slit along the machine direction into narrow, fiber-like ribbons. These ribbons are then woven to make strong fabrics, nets, and sacks. Low-density polyethylene (LDPE) is sometimes blended with PP in slit film applications in order to reduce fibrillation and improve processability. 

In the case of crystalline polymers such as high density polyethylene (FiDPE), the effect of orientation on the morphology has been extensively studied [32,48]. The isotropic sample consists of crystalline lamellae (thickness 100-400 A) embedded in an amorphous matrix. Each lamella is composed of a mosaic of crystalline blocks of lateral dimension 100-200 A with boundaries defined by dislocations. The lamellae are randomly oriented and generally arrange themselves end to end in ribbon-like structures which grow out from nucleating centers to form... 

Fig. 11.14 TEM micrograph of polyethylene thin film with a particle of CaCOa (seen as a continuous black region in the left-hand side). Crystalline lamellae seen as black ribbons when oriented edge on against interface (From Chacko et al. (1982) reproduced with permission of Wiley)...

Fig. 1.1 An early transvenous ventricular pacing lead Elema 588 (Elema-Schonander, Solna, Sweden, later Siemens Elema, and now St Jude Medical). Left Central Terylene core, at least three stainless steel ribbon conductors and polyethylene insulation. Right The electrode was very large and there were no fixation devices. The lead was over 100 cm long to allow tunneling from the subclavicular region to the abdomen, where a connector was attached and the pulse generator buried. (Permission for use St Jude.)...

Combinatorial libraries were employed to optimize microphase domain size and shape of polyethylene glycol (PEG) - poly(caprolactone) (PCL) polyurethanes, and their blends with PCL. Polyurethanes are used as biomaterials in a variety of applications, and the ability to tune microdomain size to enhance cell attachment is a desirable objective. These materials incorporate biocompatible PCL microdomains, to which cells can adhere, into a relatively non-adhesive PEG-PCL matrix. A region of chain extender composition and curing temperature, with controllable spherical-, wormlike-, and ribbon-shaped microdomains, was located through a series of increasingly focused libraries. Osteoblast-like cells (MC3T3-E1) cultured directly on selected libraries showed attachment density correlated with the distance to and size of nearby PCL microdomains. 

Figure 7 shows that the micro-injection molded polyethylene parts exhibit typical skin-core morphology similar to that observed for conventional injection molding parts. While the interface between the skin layer and the transitional shear zone is apparent, the interface between the transitional shear zone and the spherulitic core is hard to locate. The skin layer probably has shish-kebab structural characteristics. The Kebabs , which are crystalline lamellae, fill the crystalhzed space. Fibrous crystals, or the Shishs , are ahgned parallel to the injection direction. They penetrate those lamellae. The fibrillar structure follows the direction of the flow, as shown in Figure 7. The transitional shear zone may be thought of as crystalline ribbons that branch and fill crystallized space with some loss of orientation. Crystallization occurring at the sites of both the skin layer and the transitional shear zone is significantly influenced by shear or elongational stress history. On the other hand, the influence of shear on the crystalhzation occurring in the spherulitic core is negligible. The crystalline structure...

---