Why they're important
Additives, fillers, and reinforcements are used to change and improve the physical and mechanical properties of plastics. In general, reinforcing fibers increase the mechanical properties of polymer composites while particular fillers of various types increase the modulus.
Additive / Filler /|
|Common materials||Effects on polymer properties|
|Reinforcing fibers||Baron, carbon, fibrous minerals, glass, Kevlar||
Increases tensile strength.|
Increases flexural modulus.
Increases heat-deflection temperature (HDT).
Resists shrinkage and warpage.
|Conductive fillers||Aluminum powders, carbon fiber, graphite||
Improves electrical and thermal conductivity.|
|Coupling agents||Silanes, titanates||
Improves interface bonding between polymer matrix and the fibers.|
|Flame retardants||Chlorine, bromine, phosphorous, metallic salts||
Reduces the occurrence and spread of combustion.|
|Extender fillers||Calcium carbonate, silica, clay||
Reduces material cost.|
|Plasticizers||Monomeric liquids, low-molecular-weight materials||
Improves melt flow properties.|
|Colorants (pigments and dyes)||Metal oxides, chromates, carbon blacks||
Protects from thermal and UV degradation (with carbon blacks).
|Blowing agents||Gas, azo compounds, hydrazine derivatives||
Generates a cellular form to obtain a low-density material.|
Modifying polymer properties
Coupling agents are added to improve the bonding of the plastic matrix and the reinforcing fibers. Different fillers are used to lower the cost of materials. Other additives include flame retardants to reduce the likelihood of combustion, lubricants to reduce the viscosity of the molten plastic, plasticizers to increase the flexibility of the materials, and colorants to provide colorfastness.
High-aspect fillers: fibers
Fibers impact strength
Fibers affect shrinkage
Importance of predicting fiber orientation