Color Measurement in Recycled Plastic Compounding Process

The increasing concern about plastic pollution has highlighted the urgent need for effective waste management strategies. A vital component of this strategy is plastic recycling, which involves a meticulous process of collection, sorting, cleaning, and ultimately transforming discarded plastics into new, usable products. This is achieved through plastic compounding, in which recycled plastics are blended with various additives, fillers, and reinforcing materials to achieve specific characteristics such as improved strength, flexibility, flame resistance, and color.

As compounding involves the addition of various additives and colorants, color measurement plays a crucial role in the recycled plastic compounding process. This step ensures that recycled plastic compounds meet customers’ specific color requirements, maintain consistency across batches, and satisfy the aesthetic and functional requirements of various applications.

Objective Color Measurement with a Spectrophotometer

Spectrophotometers play a critical role in a wide range of industries, including the chemical and plastics industries. These color measurement instruments provide objective color data for quality control processes, ensuring that color standards and customer expectations are consistently met. In addition, they support research and development efforts by providing precise data for formulating new products and materials.

A spectrophotometer operates by measuring the reflectance or transmittance of light across different wavelengths. The resulting data are then converted into color-space values, such as those defined by the CIE L*a*b* color space. The CIE L*a*b* color space is a three-dimensional representation of color that provides a standardized framework for communicating color information. It consists of three coordinates:

• L*, representing the lightness of the color
• a*, describing the position on the green-red axis
• b*, indicating the position on the blue-yellow axis

These coordinates provide numerical values for each color parameter, facilitating the establishment of color tolerances for evaluating acceptable color differences.

Spectrophotometers can operate in various measurement modes, including reflectance and transmittance, and selecting the appropriate mode is essential for obtaining accurate and meaningful data based on the nature of the sample.

In reflectance mode, the spectrophotometer measures the amount of light reflected from the sample’s surface, making it suitable for opaque or solid plastic samples. In transmittance mode, the instrument measures the amount of light passing through a sample, providing insight into its color characteristics. This mode is typically used for transparent or translucent plastic samples, as well as liquid samples.

Konica Minolta Color Measurement Solutions for Recycled Plastic Compounds

Konica Minolta offers a range of color measurement solutions specifically designed for the plastics industry, including recycled plastic compounding applications. Among these solutions, the CM-36dG Spectrophotometer offers the flexibility of both reflectance and transmittance color measurements, making it suitable for a wide range of recycled plastic compounding applications.

CM-36dG Spectrophotometer reflectance (left) and transmittance (right) color measurement of plastics.

With repeatability of ΔE*ab < 0.02 and inter-instrument agreement of ΔE*ab < 0.12, the CM-36dG Spectrophotometer provides manufacturers with the confidence and control needed to produce recycled plastic compounds with minimal color variability while ensuring consistent color quality across production runs, even across multiple production sites.

The CM-36dG Spectrophotometer offers multiple measurement-aperture options and supports a wide range of accessories to help streamline the measurement process. In addition to delivering precise and consistent color measurements, this versatile instrument features an integrated 60° gloss sensor, enabling the simultaneous measurement of both color and gloss.

Furthermore, the CM-36dG offers an optional Wavelength Analysis & Adjustment (WAA) function, which helps correct wavelength shifts during calibration, ensuring long-term measurement accuracy and reliability.

Wavelength Analysis & Adjustment (WAA) function.

When used in conjunction with SpectraMagic NX or SpectraMagic NX2 color management software, the functionality of the CM-36dG is further enhanced. These software solutions provide trend analysis and customized reporting capabilities, including the creation of custom color formulations to meet specific requirements.

Watch the CM-36dG product video to learn more about its full range of capabilities.

Looking for the right color measurement solution for your plastic applications? Contact us today for a complimentary consultation.