Environmental Engineering Reference
In-Depth Information
plasticizers and brominated flame retardants. What is not sustainable is to
keep using additives that are evidently hazardous (and those with unknown
ecological impacts) simply because they have superior performance and
are economically the best choice. Alternative additives that not only match
or exceed the performance of conventional ones but do not pose a threat
to the biosphere including its human occupants, need to be developed as
replacements for the ones in question.
The complexity of designing a formulation with several additives is
illustrated by the following recipes. Additives have to be mixed intimately,
usually in a compounding extruder, and pelletized prior to processing.
Ingredient
Amount
(phr)
Function
A rigid PVC extrusion
compound
PVC resin
100
Base plastic
Methyl tin stabilizer
1.25
Thermal stabilizer
Calcium stearate
1.0
Lubricant (modifies viscosity)
Paraffin wax
0.15
Lubricant
Acrylic modifier
4.5
Increases impact resistance
Rutile titania
8
Opacifier (light stabilizer)
Ground CaCO
3
10
Inert filler
Polypropylene molding
compound
PP resin
100
Base plastic
Impact modifier
18.4
Increases impact resistance
Carbon black masterbatch 3.06
Carbon black (30%)
reinforcing filler
Talc
30.6
Reinforcing filler
Calcium stearate
0.15
Lubricant
Stabilizer
0.07
Stabilizer
Ground CaCO
3
10
Inert filler
