While colored plastics are used in a multitude of industries and for various applications, few people know, much less consider, how manufacturers achieve different hues. The process of creating resin color is a complex science that the plastics industry has worked to continually improve since its inception.
In this blog post, we will evaluate the plastic coloring process and consider some of the many challenges and facets of creating high-quality colored resins for plastic injection molding. For most companies looking to develop plastic products or parts, colors are an essential consideration.
The Color Matching Process
During the color matching process, a Pantone number, chip, or plaque is first used to determine the desired hue. Acquiring information about the product’s application helps manufacturers determine the precise formulation of the color concentrate.
Of course, creating a color concentrate isn’t as simple as mixing up the right colors. When matching a polymer, a slew of factors must be considered, such as viscosity and melt processing temperatures. By utilizing formulation guidelines, in alignment with the color match request form, a facility can determine what carrier resins, pigment systems, stabilizers, and other additives are suitable for a specific product/part. Understanding these particular variables is vital when designing a color concentrate.
There are many other considerations to keep in mind during the color matching process. For example, a polymer’s gloss, appearance, and filler content can directly impact the impression of color; a color in nylon will appear drastically different than the same tone in acrylic. Environmental and chemical conditions, as well as FDA suitability, must also be contemplated during the color match preparation process.
Because every polymer is subject to individual considerations and challenges, each resin coloring process must match the application-specific needs of the requested product.
Ultimately, attention to detail goes a long way in producing a colored plastic that fits the customer’s needs. A misstep at any point could result in an inferior end product.
Actual Methods For Coloring Plastics
There are many different methods for resin coloring. To choose the appropriate approach, attention to detail and careful consideration of the client’s needs is essential. Let’s go over some of the more common methods for coloring plastics.
Processors who lack experience handling custom color matches typically rely on pre-colored resins for their ease of use and fast-matching performance rates. Because pre-coloring pigments are entirely polymerized into a resin package, and used by molders as presented, they can also boost confidence in lot-to-lot consistency.
A masterbatch consists of concentrated pigments dispersed into the polymer carrier resin. In the molding process, the masterbatch is placed in a natural resin and fed into the press at a predetermined ratio which creates the desired color. The same masterbatch may be used to color various resins, depending on the selected polymer carrier. While this process may seem complicated, it is a common among molders, allowing for maximum compatibility and processing simplicity. Masterbatches also offer an economical way to color plastics and can be used in lower-volume production.
Cube Blends (AKA Salt and Paper Mixes)
A cube blend is a color system in which a masterbatch is dry-blended with a ready-to-use natural polymer. An approach commonly used by molders who lack metering equipment at the press, cube blends carefully control mixing, and therefore mitigate the color variation risks associated with self-blending.
Application-Specific Considerations for Coloring Plastic
The applications of coloring plastic are not limited to enhancing a product’s aesthetic features. Far from it. Let’s dive into some specific applications for coloring plastics.
Items That Will Come Into Contact With Food
Products that come into contact with food, such as storage containers, cutlery, and dishes, must be designed in alignment with stringent FCS (food contact substances) regulations. These regulations are meant to protect end-users. Polyethylene Terephthalate (PET) resins are widely used in manufacturing “food contact” plastics such as soda bottles and salad dressing containers. Because PET is a stable resin, it resists corrosion, repels microorganisms, and doesn’t degrade when in contact with food or beverages.
Other food-safe plastic resins, including polypropylene, polycarbonate, and HDPE offer various durability, nonvolatile, and storage benefits that produce non-hazardous solutions for food packaging manufacturers. If the resin coloring pigments contaminate foods, serious safety risks can arise.
Toys and Items Meant For Children
When manufacturing plastic toy parts and products, one must also consider similar regulatory hurdles to food-contact plastics. Because many toy parts and products incorporate colored plastics into their design and construction, it is vital for manufacturers to facilitate the safety standards and appropriate testing processes when addressing potential hazards to consumers and children.
Medical Specific Applications
Many medical applications have very strict hygiene requirements. Some applications will be inserted into or else come into contact with sensitive areas of the body, such as the mouth or blood vessels.
Matching the colors of different car components can be a complicated process. Manufacturers must ensure that when color-matching a plastic handle with a metal door, for example, they utilize precise hues that appear visually the same regardless of lighting conditions, material differences, and environmental conditions.
Window Components and Other Plastics Exposed to the Environment
Many plastics are used outdoors. Sunlight, rain, and other factors can cause colors to fade. Further, coloring must be resistant to heat. Poorly done plastic coloring will fade, and often components must then be replaced.
Conclusion: Plastic Coloring is Both Art & Science
A multitude of considerations spans the entirety of the plastic-coloring process. Regarding colored-plastic design, manufacturing methods, and application-specific regulations, the expectations of consumers, clients, and end-users must be closely attended to. Perfecting your coloring processes can ultimately mitigate product errors, boost the efficiency of large production batches, minimize waste, and reduce manufacturing costs.
Because coloring plastics requires a skilled hand, sharp eye, and the latest coloring techniques, contact New-Berlin Plastics for more information on color-delivery processes and manufacturing services.