Plastics fillers, lowered density

Hollow glass microspheres can be added to POs as a way of stiffening the resin system while also reducing its density substantially. Microspheres that are used as plastics fillers have typically only about 0.6g/cm density, much lower than standard fillers (with densities of 2.7-2.9). The low density hdps make... 

The flotation test is a rough method to identify plastics since results are dependent on the physical form of the material. Foams contain cells filled with air, so their densities will be lower than a solid block of identical dimensions of the same type of plastic. Water-sensitive or absorbent fillers such as paper... 

Cost The cost of simple extender fillers may be lower than polymers on a weight basis, but their higher density, more difficult processability, and decrease in strength properties may eliminate any overall economy. Fillers shonld be chosen primarily for their beneficial effects on technical properties if they also decrease cosL this is simply an added benefit. Reinforcing fibers increase the cost of commodity plastics, bnt they may actually reduce the cost of some high-end engineering thermoplastics. 

A relatively inert substance added to plastics to improve their physical, mechanical, thermal, electrical, or other properties or to lower cost or density. A compound or substance added to a polymer during the initial synthesis process or in subsequent processing to decrease the volume of resin needed to produce a given product. Fillers are generally much lower in cost than the resins they are used in, thus reducing resin cost per part. Fillers or extenders are generally not used with engineering resins. 

Perlite p9r- llt [F, fr. perle pearl] (1833) n. A siliceous lava which, when heated to 720-1090° C, expands to 10-20 times its original volume, forming tiny, hollow, spherical bubbles. Perlite is much used as an ingredient of lightweight concrete and as a density-lowering filler for plastics. 

Copolymer type and melt flow rate also influenee the creep behaviour. Copolymer grades of PP have substantially lower ereep modulus than the homopolymer grades. PP has a similar modulus to high density PE, but its resistance to creep is much better and, at a equivalent time under similar load, the creep modulus of PP is more than that of high density PE. However, the ereep resistance of amorphous plastics is much better than the semi-crystalline plastics such as PP and PE. Creep resistance of PP could be further improved by addition of fillers or reinforcements. The creep behaviour of moulded artefacts is affected by the residual stress or orientation effect in the moulded article. 

Cork n The outer bark of Quercus suber, a species of oak native to Mediterranean countries, having density in the range 0.22-0.26 g/cm. Cork is used as a core material (see Core (1)) in sandwich stmctures and, in ground form, as a density-lowering filler in thermoplastic and thermosetting compounds for special applications such as flooring, ablative plastics, insulating compositions, and shoe inner soles. 

---