NIPS system

Since quite a bit of difference exists between raw materials, the recipe, and the equipment, the processing procedure and conditions vary a lot. Also, the processing procedures of commercial products are usually not available to the public. Thus, much work needs to be done to find the best procedure and condition for each individual system. In general, a good procedure is a combination of optimal processing time, temperature, and rotating speed of the screw (in the case of extruder use) or the roll nip (in the case of calender use). 

Kumar et al. have studied the miUing behavior of brominated isobutylene-co-p-methyl styrene (BIMS) and its blends with EPDM [40]. Using the theoretical model of Tokita, they have tried to optimize the rmU parameters. They measured the critical nip-gap at which a front-to-back roll transition takes place. They concluded that addition of different fillers reduced the critical nip-gap for BIMS as compared to the gum polymer. The critical nip-gap is lower for systems containing... 

This basic operation utilises a two-bowl calender in horizontal or vertical configuration. The feed material, either in strip or pig form, is fed into one side of the nip and is squeezed by the bowls, thereby emerging as a sheet which is pulled from the bowl by some manual or mechanical means or supported by a liner cloth. Because of their versatility, three-bowl calenders are now more widely used for sheeting as well as other basic calendering operations. Thickness control is accomplished by use of the adjustable nips and may be further refined by automatic control systems using thickness sensors. It should be noted here that the force required in the nip to flatten the feed material causes deflection of the bowls, however slight. If some corrective steps are not taken, the product thickness will vary across the sheet, resulting in excessive variations of the product and possibly excessive use of expensive materials. In order to overcome these problems, three basic techniques are used to achieve uniform product thickness ... 

Systems , Ibid, p 538-52 [Use of the "Method of Characteristics in the code NIP (Normal Initiation Program) is described and compared with the "Mesh Methods . Method of Characteristics was described by Courant Friedrichs (Ref 6) and Glennie (Ref 8). 

At the end of the forming system, the paper web is transferred from the wire to a press felt, a fine-textured, usually synthetic fabric. At this point, the web contains about 4 or 5 parts water to 1 part solids. The wet paper web and one or more press felts pass through two or more press-roll nips, where water is squeezed out. Pressing also compacts the paper mat. This increases the potential interfiber contact areas where bonds will be formed. 

A successive report from the same group [50] discussed the influence of molecular recognition on the substrate binding, and therefore catalytic activity, in the peroxidase system previously developed. The authors reached the conclusion that the haemin played a role not only in the catalytic cycle but it was also essential in the molecular recognition of the substrate, by cooperating with the other co-monomers, 4-vinyl-pyridine and acrylamide. Moreover, imprinting efficiency was demonstrated by showing that the catalytic activity of the MIP was enhanced 7.6 times with respect to the NIP. 

Figure 6.26 Schematic diagram of a two roll calendering system in the nip region.

A 15 cm diameter, 2 m wide calendering system is used to produce a PVC sheet with a Newtonian viscosity of 10,000 Pa-s. The roll speed, U is 6 m/s and the distance between the nips is 5 mm. 

Consequently, there are 3(N + NIP) velocity unknowns and 3N traction unknowns. This makes eqn. (10.95) a system of 3(N+NIP) equations with 3(N+NIP) + 3Nunknowns. Each boundary nodal point has either traction or velocity specified for each direction as a boundary condition, thus the system in eqn. (10.95) can ultimately be arranged into a solvable system of linear algebraic equations as... 

It should be noted that the adaptation of the NIPS or TIPS method to the fabrication of hollow-fiber membranes is straightforward for most systems (cf. Figure 2.4). Characterization of UF membranes is typically done via sieving... 

Fig. 6.22 The nip region of the two-roll geometry, with radii R. A rectangular coordinate system is placed at the midplane in the gap between the rolls connecting the two roll centers.

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