Elastomer Reinforcement Using CelTiX™
Diatomaceous Earth (DE) is a natural silica source formed from the sedimentation of single cell aquatic organisms called diatoms. DE can form in marine or fresh water environments and exhibit properties that are related to their unique shape and structure. These properties will vary according to the diatom species found in each deposit, each with differing chemistries, shape factors and pore structures.
CelTiX™ is a fine, natural freshwater diatomaceous earth product, with excellent reinforcing ability in most types of elastomer. Due to its unique physical form and inert chemical nature, it is an effective reinforcing filler in a wide variety of applications. CelTiX™ is especially effective when used in conjunction with organosilanes, even at low surface treatment levels.
Imerys Filtration DE, including CelTiX™, can be used in a variety of elastomer applications. The combination of high surface area and open pore structure makes CelTiX™ a very good reinforcing agent. CelTiX™ is most beneficial in compounds that require high hardness and low compression and tension set properties. It is also of value in compounds with high amounts of added oil. CelTiX™ can be used in most common elastomers such as EPDM, SBR, NR, TPE and others.
CelTiX™ combines the properties found in other common white fillers used in rubber. It gives excellent tensile, tear and abrasion properties combined with a very low compression set.
The particle size of CelTiX™ is relatively large for a reinforcing elastomer filler, however, it is the mechanical interaction of the pore structure with the elastomer that provides the reinforcing effect, rather than a fine particle size. CelTiX™ provides changes to hysteresis and low elongation not seen with conventional fillers.
Formulating with CelTiX™
Unlike many additives, CelTiX™ does not adversely affect peroxide cures. The porous structure of the filler particle limits its breakdown during compounding, resulting in limited generation of more reactive surface area which reduces interactions with peroxides and other additives. CelTiX™ also has less interaction with most sulphur cures versus commonly used fillers. Changes in the cure profile can occur if there is an interaction between the DE and certain accelerators used in sulphur cures. This can be overcome by the addition of additives, such as glycols, that are commonly used with other fillers.
CelTiX™ and other DE products should be added at a low viscosity point in the mixing, at a stage without liquid additives, to get the best performance.
Processing with CelTiX™
CelTiX™ is a valuable additive in elastomerics. The unique structure of our products reduces friction at the extrusion die, so even at low levels of addition (e.g. 0.25phr) there will be a reduction of surface problems such as “shark skin”, along with improved extrusion speed and finish, maximizing your cost savings during processing.
Table 1. Typical properties of CelTiX™, used to reinforce elastomers*
|Blue Light Reflectance (%)||83.7|
|% +325 mesh||1|
|Oil Absorption (%)||220|
|Surface Area (m2/g)||31.8|
Reinforcement in a SBS system using CelTiX as a partial or full replacement of precipitated silica*
While CelTiX™, as a diatomaceous earth product, is a natural silica, it has a very different surface chemistry than that of synthetic silicas, because of the much lower surface density of the hydroxyl groups. This difference results in less torque required during mixing and the ability to reach higher loading levels, which reduces overall formulation costs. For compounds in which high elongation is not necessary, CelTiX is a functional filler that provides good reinforcement properties.
|25phr CelTiX & 25phr SS||14.5||62||568%||476%||13%||220%|
|50phr CelTiX & 25phr SS||20.0||68||545%||1383%||40%||192%|
SBS Block CoPolymer Base
SS = Commercial Reinforcing Precipitated Silica
Results normalize to the unfilled system
*The physical properties of the products represent typical values obtained in accordance with Imerys Filtration test methods and are subject to manufacturing variations. They are provided here as a general reference only, are subject to change without notice, and should not be relied on for any particular application.
For further information please contact us.