Flexible profiles

The most widely plasticized polymer is polyvinyl chloride (PVC) due to its excellent plasticizer compatibility characteristics. Only by incorporation of a plasticizer a degree of flexibility is achieved, which makes PVC suitable for applications such as cable insulation or sheathing, calendered sheets, floor covering, flexible profile or synthetic leather. However, plasticizers have also been used and remain in use with other polymer types. 

Chem. Descrip. Coated modified lead sulfophthalate complex Uses Heat stabilizer for PVC wire and cable (60-105 C), wire coatings, flexible profiles, film sheeting, plastisols Features Economical... 

Geon 102EP 1.12 73 0.35 rigid flexible profile extrusion... 

Plasticizers are typically organic hquids which can be added to PVC to obtain a product with flexibihty. If PVC is processed with thermal stabilizers (necessary for all PVC apphcations) but without plasticizer, a rigid product is obtained, the material being termed unplasticized PVC or PVC-U (this includes the well known application of window profiles). The successful addition of a plasticizer will result in the formation of a product with a degree of flexibihty, such as a cable insulation or sheathing, a floorcovering or flexible profile. The clear differentiation... 

PHR in the case of plastisols. In dry blending, a flexible profile formulation for extrusion, it is imperative that the plasticizer added to the PVC resin gets fully absorbed, yielding a dry compound. A semidry powder blend can cause processing as well as conveying problems. The plasticizer absorption efficiency is related to the rate of heating of the resin-plasticizer mix, the type of resin, the particle size and distribution, the surface-volume ratio, and the type of plasticizer. Additives such as filler and impact modifiers also have an effect on plasticizer absorption. 

The twist form is also called the flexible form, because without angle strain a left-handed twist (c) can be converted into a right-handed one (d), by way of a third form ca. 7 kJ mol higher in energy (and actually not strictly an intermediate, since it occupies a maximum on the energy profile) which is the boat form (e). 

The storage facilities at the end of the profile production line depend on the type of product (see Fig. 4.19). If it is rigid then the cooled extrudate may be cut to size on a guillotine for stacking. If the extrudate is flexible then it can be stored on drums. 

FIG. 12 Segment density profile as function of the distance from the wall Z for flexible (empty symbols) and semi-rigid (full symbols) living polymer chains at T = 0.4 [28]. The fractional occupancy of lattice sites by polymer segments is shown for the layers in the left half of the box. Dashed lines are guides for the eyes. 

Flexible couplings Most flexible couplings use an elastomer or spring-steel device to provide power transmission from the driver to the driven unit. Both coupling types create unique mechanical forces that directly affect the dynamics and vibration profile of the machine-train. 

The most obvious force with flexible couplings is end-play or movement in the axial plane. Both the elastomer and spring-steel devices have memory which forces the axial position of both the drive and driven shafts to a neutral position. Because of their flexibility, these devices cause the shaft to move constantly in the axial plane. This is exhibited as harmonics of shaft speed. In most cases, the resultant profile is a signature that contains the fundamental (lx) frequency and second (2x) and third (3x) harmonics. 

Because of the length of these shafts and the flexible couplings or joints used to transmit torsional power, jackshafts tend to flex during normal operation. Flexing results in a unique vibration profile that defines its operating mode shape. 

Mounting configuration and operating envelope Industrial standards, such as the rathbone severity chart, assume that the machine is rigidly mounted on a suitable concrete foundation. Machines mounted on deck-plate or on flexible foundations have higher normal vibration profiles and cannot be evaluated using these standards. 

Flexible polyethylene separators have facilitated a novel cell construction the separator material, supplied in roll form, is wound so that it meanders around electrodes of alternating polarity (Fig. 23), requiring ribs in the cross-machine direction such profiles are available commercially [60],... 

Fig. 4-2 a) Load-testing profile of flexible and rigid underground pipes. 

Polybutadienes, polycaprolactones, polycarbonates, and amine-terminated polyethers (ATPEs) are shown in Scheme 4.4 as examples of other commercially available polyols. They are all specialty materials, used in situations where specific property profiles are required. For example, ATPEs are utilized in spray-applied elastomers where fast-reacting, high-molecular-weight polyamines give quick gel times and rapid viscosity buildup. Polycarbonates are used for implantation devices because polyuredtanes based on them perform best in this very demanding environment. Polycaprolactones and polybutadienes may be chosen for applications which require exceptional light stability, hydrolysis resistance, and/or low-temperature flexibility. 

The lower symmetry of nanorods (in comparison to nanoshells) allows additional flexibility in terms of the tunability of their optical extinction properties. Not only can the properties be tuned by control of aspect ratio (Figure 7.4a) but there is also an effect of particle volume (Figure 7.4b), end cap profile (Figure 7.4c), convexity of waist (Figure 7.4d), convexity of ends (Figure 7.4e) and loss of rotational symmetry (Figure 7.4f). 

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