Calendering formulation

S-PVC calendering formulation. [Data from ParaloidBTA-780S mbs impact modifier for PVC packaging applications. DOW 874-01721-0810.]... 

Example of effective stabilization of calendering formulation. [Data from... 

In the case of unplasticised polymer the main concern is with control of gelation and ensuring processability and adequate stabilisation. The formulation selected thus depends almost as much on the actual processing equipment used as on the end-product. Formula 8 gives a typical rigid opaque formulation suitable for pipes and Formula 9 a transparent calendering compound. 

Sulfonated EPDMs are formulated to form a number of rubbery products including adhesives for footwear, garden hoses, and in the formation of calendered sheets. Perfluori-nated ionomers marketed as Nation (DuPont) are used for membrane applications including chemical-processing separations, spent-acid regeneration, electrochemical fuel cells, ion-selective separations, electrodialysis, and in the production of chlorine. It is also employed as a solid -state catalyst in chemical synthesis and processing. lonomers are also used in blends with other polymers. 

Tile is manufactured in several ways. In each method, a continuous sheet is formed gauge refinement and planishing are carried out in subsequent calendering steps. Stresses that could lead to poor dimensional stability are avoided. The efforts to prevent stresses are governed by formulation, stock and roll temperatures, conveyor speeds, etc. After the final calendering, a resin—polymer—wax finish is applied to the surface of the sheet which is then buffed before it moves to the punch press. Frame scrap and tile rejected because of defects are returned to the mixers and recycled. 

Starch grafts are a new class of products for use on the size press.212,213 They have high water retention and form flexible films. They are offered as a liquid, ready-to-use binder on conventional and metered size presses and on calender water boxes. Starch grafts are used in pigmented formulations for the production of film-coated offset, recycled offset, textbook and LWC (lightweight coated) grades, and as precoat for double-coated, sheet-fed offset grades. 

Results such as these suggest strongly that there is indeed an optimum way of running a calender for each formulation, working backwards from the mean line, speeds and gap settings can be calculated and appropriate temperature settings estimated. When this has been done the conditions predicted have been found practical, although admittedly the results were no better than could be... 

The 121 sample films were formulated into a replicate series. Those utilizing emulsion polymerized PVC were cast from plastisol onto glass plates and fused in a circulating hot air oven. Those incorporating suspension polymerized PVC were fluxed via a Banbury and two-roll compounding mill and finished on an inverted L 8-inch X 16-inch four-roll calender. Plastisol films were of nominal 8-mil thickness calendered film was 4 mils. 

The rigid film calendering process (details in Section 5.2.6) requires particular lubricant formulations and these have also been reviewed (132). 

Zine is a crucial element in the formulation of many heat stabilisers used in PVC, however exeessive use ean have a negative impact on the degradation of the PVC (30). This is because zinc pyrithione typieally eontains 20% zinc. Some PVC formulations, particularly those calendered or extruded under higher sheer, are zinc sensitive as they reaet with hydrogen chloride and form zinc chloride, whieh catalyses further degradation of the PVC. The outeome is yellowing and poor PVC stability (Figure 32). 

Therm-Chek. [Ferto/Bedford] Light and heat stabilizers fix PVC, dastisols, organosols, rigid formulations, calendered, mold and extruded plasticized ccxnpositions. 

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