Plastisol rotational molding

High-volume dipped parts such as tool handles and dish racks use automated lines as with powder coating. Plastisol dip coats are also used to decorate plastisol rotational moldings, notably in the production of multicolored traffic cones. 

PVC Plastisols 1940 M-H VG G G G Slush and rotationally molded, foamed, extruded Used in coating machines to cover paper, cloth and metal... 

Why is the feedstock for rotational molding processes either a finely divided powder or plastisol ... 

Plastisols allow the use of inexpensive manufacturing techniques, such as slush and rotational molding, casting, dipping, etc. They are employed for tile manufacture of a large variety of parts, e.g., toys, floor mats, handles and many others. 

One of the larger uses is for wire and cable insulation. The flame resistance makes this the material of choice for residential wiring, extension cords, and so on. Inexpensive garden hose represents another large-volume use. Sports balls can be produced by rotational molding of plastisols. The low fabrication cost allows such products to dominate the lower-price-range market.76-77... 

Rotational molding of vinyl plastisols is similar to the rotational molding of powder or liquid plastics (Chapter 13). Plastisol is placed in the mold and heated while the mold is being rotated. Molded products can include tanks, volleyballs, basketballs, doll heads and bodies, and various automobile parts. 

Important processing methods extrusion, plastisol coating, thermoforming, calendering, blow molding, rotational molding, injection molding... 

Aromatic and aliphatic hydrocarbons are used as extenders, particularly in the manufacture of PVC plastisols that must maintain as stable a viscosity as possible for relatively long periods of time (dip and rotational molding). The petroleum industry offers imprecisely defined products with an aliphatic-aromatic structure for use as extenders. They are added to plastisols in small amounts as viscosity regulators. Dibenzyl toluene also serves the same purpose. A disadvantage of this type of extenders is the risk of exudation if excessive quantities are used. 

Once the fluorescent colorant passes quality control testing, it is then distributed to compounders to be made into color concentrate. Once in solid masterbatch or liquid concentrate form, the fluorescents are used in a wide variety of applications, including injection molding, rotational molding, blow molding, extrusion, and vacuum forming. These fluorescent colorants are used primarily in polyolefins, in vinyl plastisols, and somewhat less in styrenics, acrylics, and ABS. 

Chem. Descrip. Vinyl chloride homopolymer Uses PVC for slush and rotational moldings, dip coatings and moldings, plastisols... 

Uses Vise, reducer for unfilled PVC plastisols for artificial leather, carpetbacking, casting, coil coating, conveyor belts, dipping, flooring, rotational molding, inks, tarps, wallpapers Features Low emission... 

Figure 10.25. Hydrocysts and bad distributions in a PVC plastisol processed by rotational molding.

The rates of gelation and fusion processes of PVC plastisols are more critical in the operations involving simultaneous heating and flow of plastisol, such as present in rotational molding. It is because inappropriate plastisol viscosity (dilatant or too viscous plastisol) and a fast gelation process may alter required distributions of material, formation of bubbles and hydrocysts ° (see for example Figure 10.25). 

In the early days of rotational molding only vinyl plastisols were used. The first polyethylene for rotomolding was produced in the 1960s. Today polyethylene is the principal material for the industry. The distribution of resin use in rotational molding is indicated below (6). 

Moiding. This is used for producing hollow articles such as halls, dolls, and toys. The process requires a plastisol with low viscosity at low shear rate that has a short gelation time and is easy to deaerate. In rotational molding the plastisol is poured into a cold mold that rotates aroimd two perpendicular axes whilst entering an oven where it is heated with air to 200-250°C. After gelation and fusion, the mold is cooled in a waterbath. 

---