Additives and masterbatches: types, functions, and applications

In the process of manufacturing, plastics contain small amounts of other foreign materials, such as emulsifiers and catalysts. In order to convert them into granules and masses of molding, and during the process of ready-made and formulation, plastics tend to receive small amounts of additives, which facilitate its transformation either modify its properties box.

1. Conductive additives

To make the surface conductive and shielding are can be metallized by surface: vaporization in vacuum, projection of metals by galvanic coating (chrome finish) or low melting point.

• Types: special smoke black, carbon fibres, fibres or metal shavings.
• Functions: reduction in the specific resistance of the plastic depending on its nature and percentage. The smoke black drivers reduce the resistance cross until it between 102 and 5 •cm. With metallic additives it can lower resistance to < 1 •cm
• Applications: electrical components.

2 Ignifugantes

To be able to estimate the risk of fire, it is important to know the behavior of plastics from the previous phase until the appearance of the flame (flammability, combustibility behavior flame). With the addition of ignifugantes this natural behavior of plastics can be focused to a greater or lesser extent.

• Types: aluminum hydroxide, brominated, chlorinated and phosphorus products.
• Functions: reduction of the combustibility of plastics. Involved in the combustion process during phases of warming, decomposition, inflammation and spread by flame of plastics.
• Applications: for thermoplastics, usually mixed with them.

3 Dyes and pigments

Both dyes and pigments involved in a percentage between 0.5 and 2%. The properties of plastics can be altered by the addition of additives of color, e.g. mechanical strength, especially if the pigments are not distributed evenly. You can see these uniformities in the optical microscope. But, if the dyes or pigments are added in low percentages, normally, the general properties box is not altered.

Pigments, which can be organic or inorganic, are insoluble in plastic and give it color and opacity. Dyes are soluble in the plastic and are important in the staining of parts or semi-finished products of transparent plastics (PMMA, PS, PC).

Addition of products from color systems:

• In general, color products are already incorporated into the ready to process grain.
• They can mix in powdery form with the natural grain of the plastic (undyed) and homogenize the mixture through the extruder.
• You can add a masterbatch (concentrated color in the form of granules) to natural (undyed) plastic granulate and mix them to processing them in extruder (little dust formation).

4 Plasticizers and flexibilizing

Plasticizers are usually products of low molecular weight, visco-doughy consistency, that are introduced within the molecules of the polymer material (eg: to manufacture PVC-P, plasticized, is used between 20% and 50% of plasticizer) at the time of "gel", producing an increase in flexibility and impact resistance improved.

It is important to know that during use, the plasticizers can vaporize or migrate, irrevocably reducing the flexibility they provide.

In polyamides: absorption of water molecules to produce an effect similar to the plasticizing, i.e. polyamide properties depend on its water content.

5. Mineral fillers and reinforcing fibers

Loads are particles of small size, short fibers or tiny spheres of organic materials (pulp, sawdust) or inorganic (ground stone, Crete, talc, glass esferillas).

Types

• Graphite, MoS2 or PTFE: to improve the sliding thermoplastic.

Reinforcement fibers, are long fibers or woven fibres, cut shaped rug, (non-woven) fleece or rovings (continuous fiber).

When selecting a fiber reinforcement, should take into account:

• Density (g/cm²)
• Tensile strength (MPa)
• Module E (modulus of elasticity, GPa)
• Elongation at break (%).

Use

Note

According to the percentage rate of charge and the system of transformation may be that the distribution of these materials in parts not homogeneous (anisotropy).

6 Hinchantes

With the aim of frothing a plastic (thermoplastic, thermoset or elastomer), add blowing solids, vaporizing them by action of the heat provided. In theory, any plastic could froth, but they are few, in practice, which are used in form foamed (cell structure).

Foams are those materials that have cells (open, closed, or both) on all its mass and which have a density lower than the substance that acts as a structure (DIN 7726).

Procedures of foaming (examples):

• Styropor procedure: manufacturing of expanded polystyrene (EPS)
• Injection of thermoplastic foam WST (Inyeccion-espumacion thermoplastics)
• Inyeccion-espumacion by reacccion RSG.

• Homogeneous rigid foams based on EPS, PF, UF and PUR: for thermal insulation, to give rigidity to hollow structures (PUR).
• Integral rigid foams (reaction RSG) (density 0, 5-1, 1 g/cm³): for constructive purposes (furniture, appliances, radio, television, etc.)
• Soft PVC foam (density 70 - 100 kg/m³): to fill, quilting, insulation of pipes, buoys, life jackets, cold protection suits.
• Soft PE foam (density 30 - 100 kg/m³): as padded packaging of fragile items.