Silicone masterbatches are pigment concentrates specifically designed to colour silicone products without altering the physicochemical properties of the base silicone. These concentrates are homogeneously integrated into the base silicone, ensuring colour uniformity in applications where visual consistency is a critical quality parameter.
Composition and Technical Characteristics
A masterbatch is composed of organic or inorganic pigments and/or dyes dispersed in a polymeric base compatible with the silicone, optimising the integration of the colour into the material during processing. The choice of base silicone is critical, as it must meet specific chemical and physical compatibility requirements to avoid interference with the rheological profile and final properties of the silicone elastomer.
Advantages of Silicone Masterbatches:
-
- Colour stability: Formulated with specially selected pigments, masterbatches ensure long-term colour stability. This stability includes resistance to thermal ageing, ultraviolet (UV) exposure and migration, critical factors in demanding applications such as automotive, aeronautics, electronics, medical, food, etc.
- Total Compatibility with the Silicone Matrix: The specific formulation of these masterbatches ensures optimal compatibility with the silicone polymer, maintaining the elasticity, tensile strength and curing properties of the base material. Unlike powder pigments, the masterbatches do not interfere with the crosslinking kinetics and viscosity of the system, allowing for more efficient mixing and minimising defects during processing.
- Improved Pigment Dispersion: Pigments are pre-dispersed in the masterbatch matrix, eliminating problems of agglomeration and colour segregation during processing. This results in uniform colour distribution, even in high viscosity silicone systems.
- Formulation Flexibility: Masterbatches can be designed to meet additional requirements. Optional functional properties include flame resistance (to comply with standards such as UL 94), antibacterial properties, and resistance to discolouration from UV radiation or chemical exposure. These additional features broaden the range of applications for masterbatches in industrial sectors, with high quality standards.
Silicone Integration Process
The masterbatch is easily incorporated during the pre-mixing stage of the silicone polymer prior to the curing process. For example, by addition at the extrusion stage or in a high shear mixer: cylinder, closed mixer, bambori, continuous mixer, etc.
The recommended dosage varies according to the degree of pigment concentration and the desired level of opacity or intensity, but is generally between 0.5% and 5% by weight. It also depends on the amount and type of inorganic fillers added to the mixture.
During processing, it is essential to ensure a suitable mixing temperature to facilitate the dispersion of the masterbatch and, depending on the type of vulcanising agent to be used, not to pre-cure the elastomer.
Industrial Applications for Silicone Masterbatches
Silicone masterbatches are widely used in sectors where colour customisation and stability of mechanical properties are essential requirements:
· Automotive industry: In sealing and gasketing components, where high thermal stability and weather resistance are required. Masterbatches designed for this industry ensure colour uniformity and fade resistance under extreme heat and exposure to oils and fuels.
· Medical sector: In medical devices and products, such as catheters, parts and components for various devices and machinery. The masterbatches must comply with the regulations of
biocompatibility (ISO 10993) and sterility, as well as colour stability during sterilisation cycles.
· Electronics industry: Used for component encapsulation and circuit protection, where colour is used for visual coding and differentiation of components, cables and cable sheathing. Dielectric strength properties can be added to prevent interference from electric fields.
· For the food industry: for the manufacture of kitchen utensils, baking moulds, etc. where the silicone must withstand high temperatures without modifying the colour and comply with European and FDA regulations..
Technical Considerations in Masterbatch Selection
The choice of a masterbatch for silicones must be based on a technical analysis of the polymer matrix, the pigments used and the requirements of the final application. Factors to consider include:
1. Compatibility with the Base Silicone: Ensure that the masterbatch carrier matrix does not alter the structure of the silicone polymer, affecting the viscosity, cure time or elasticity of the material.
2. Ease of dispersion: it is necessary to take into account the type of pigment, its physical and chemical roperties, the base on which it is dispersed, the concentration of Pigment. It is very important that, when adding the masterbatch to the silicone bases, it is dispersed quickly without forming lumps until a homogeneous mixture is formed.
3. Additional Properties Required: Determine if additional properties such as UV resistance, flame retardancy or food contact certification are required, tailoring the masterbatch selection to the applicable regulations.
At Coniex, s.a. we manufacture masterbatches for silicones that represent an advanced technical solution for the chromatic modification of silicone products, allowing the integration of colour in a reproducible way and without compromising the physical properties of the elastomer. Thanks to their ability to offer additional properties and maintain colour stability under demanding conditions, they are a key tool in the formulation of advanced solutions for the general industry.
If you are interested or need to implement masterbatches in your silicone production processes, we invite you to contact us to offer you customised solutions adapted to your specific requirements.