Calcium Carbonate in Plastic Applications
Calcium carbonate (also called whiting) is the most widely used mineral due to it’s wide availability, ease of processing to specific particle sizes and it’s compatibility with a wide range of polymer types. One limitation is that it reacts with acids so should not be used in acidic formulations or environments.
PVC window profiles
PVC Window profiles require good physical and visual properties. Fine particle size calcium carbonate such as Polcarb SB, Polcarb SV offer the best physical properties when impact strength and tensile strength are considered. If extra whiteness is required Carbital SV, based on high brightness marble feed, should be considered. Careful control of particle size is used to produce these materials as larger particles have been found to significantly reduce the important physical properties. Stearate coating assists in the compounding phase of production, as well as acting as a lubricant during extrusion, which helps maintain good output and surface finish, another important property for window profiles.
For general purpose PVC extrusions, including pipe for rainwater applications and cable ducting, the physical properties required are not as demanding as those for window profiles, and often the colour required is not white. Polcarb 60S, Polcarb 40SV and Polcarb 50SV can all be used as economical yet effective fillers. As with the finer grades, their particle size and stearate coating level is carefully controlled.
PVC cables use calcium carbonate at loadings of around 70 phr. The choice of calcium carbonate will depend on the specification of the cable. Higher quality cables benefit from the better mechanical properties (tensile strength and elongation) and electrical properties (volume resistivity) offered by finer coated grades such as Polcarb 50SV and Polcarb 40SV. Cables with lower specification can use uncoated whiting such as Micronic S.
Polypropylene is often filled to increase rigidity, a requirement that becomes very important at higher temperatures. Our research has shown that fine grades such as Polcarb 60S can improve toughness and increase rigidity more than coated marble grades which typically have a wider particle size distribution. The absence of coarser particles also minimises the effect on gloss, important to give a good appearance. Increased polymer prices favour the increased use of calcium carbonate as a functional filler.
Where the finished product is to be painted or chrome plated, the acid – carbonate reaction can be used to advantage. Items made from compounds containing calcium carbonate are acid etched, which dissolves any particles near the surface, creating a slightly roughened surface which improves the adhesion of paint. Polcarb SB is an ideal grade for this application due to it’s fine particle size.
Sheet and Bulk moulding compounds (SMC and BMC) are used to produce a wide range of items, from small items like coffee machine housings to large ones such as lorry panels. Both can be very complex in the moulded shapes that are formed, making it essential that the compound has the correct viscosity profile so that moulds are completely filled. Carbital and DRB grades are ideal for this application.
Imerys calcium carbonate for plastics
To see the complete listing of Imerys calcium carbonate products and the range of plastics applications they can be used in, look at Calcium Carbonate (CaCO3) Portfolio for Plastics in the Product Related Literature below.
Our range of Polcarb and Carbital products is available across Europe from our expanding range of assets. Contact us for more advice on the most suitable grade for you.
Product Related Literature
Carbital 110S in Polypropylene [352KB]