Custom Colored Polymers
Colored polymer components provide functionality and aesthetics in medical applications. Colors are used to differentiate product type, size, or model. Certain colors may even convey meaning, such as reds or yellows for warning notification.
Common Coloring Techniques
Colored polymer components can be produced from masterbatch concentrates (blended into natural polymer prior to molding or extruding) or pre-colored polymers via melt blending/compounding. Selection of one coloring method over the other may vary based on economics, secondary operations and end application. Foster Corporation has processing capabilities to manufacture both masterbatch and pre-colored polymers. Our experienced team of material scientists and process engineers are available to select the most appropriate coloring technique for your requirements.
Pre-Colored Compounds vs. Masterbatches
Masterbatches or color concentrates provide an economical solution for long manufacturing runs of high volume parts. Sufficient setup time is required to ensure the concentrate is properly blended prior to and during the melt processing phase to achieve the desired color consistency from part-to-part. This investment may be offset by the economies gained from using a high proportion of unmodified polymer at a reduced price.
The use of masterbatches however, can present several challenges. Metering un-dried masterbatches into hygroscopic resin may impart additional water causing undesirable part appearance, processing and performance issues. Also, masterbatches require additional handling that is inconsistent with the natural polymer to which it is added; subsequently resulting in potential production variability. Concentrate pellets are also denser than the natural polymer pellets and tend to sift downward in the hopper, often leading to variable loading levels and color drifts throughout a production run. Although use of color metering weigh feeders can minimize variation, it also requires additional equipment and production controls. This in turn, reduces the potential cost savings for short production runs.
Value of Pre-colored Polymers in Medical Applications
The primary reasons our pre-colored polymers are chosen over masterbatch/resin mixtures include:
High Pigment Loadings – High pigment loadings may be required to achieve particular colors, or to off-set the natural color of some polymers. In such cases, the let-down ratios of masterbatches may be impractical or uneconomical compared to pre-colored polymers.
Short Production Runs – Short production runs have less opportunity to recoup investments in setup time required for masterbatches. Pre-color polymers frequently save setup time, increase part acceptance rates and ultimately save money.
Small Material Volume – For parts that require a couple hundred pounds annually, pre-colored polymers are cost effective since most masterbatches are produced in quantities suitable for blending into much larger volumes.
Thin Wall Parts – Thin walls parts require higher pigmentation to achieve opacity. Poorly dispersed pigments in thin walls are a common cause of part rejection. Pre-colored polymers, especially those produced using twin screw compounding, provide substantially greater dispersion of pigments over masterbatches, which improves consistency.
Small Production Machines – Small molding or extrusion machines with their screw diameters, shallow flight profiles and screw lengths are less reliable when it comes to dispersing masterbatch concentrates. Pre-colored polymers do not rely on the part processing equipment for pigment dispersion and color control.
Regulatory & Quality - Pre-colored formulations may offer medical product manufacturers a more controlled process required for regulatory filing, process validation and supply chain management.
Pre-color compounds and masterbaches can be manufactured using FDA Food Grade Pigments listed under FDA 21 CFR part 173-178 or using FDA Medical Device Pigments listed under FDA 21 CFR Parts 73 and 74. For medical applications, For medical applications, the selection of one pigment classification over the other may affect the FDA approval process.