Plastics can be categorized in several ways, depending on the criteria used. The most common methods include:

1 - By chemical structure and application:

• Styrene-based Plastics – e.g., PS, ABS

• Olefin-based Plastics – e.g., PE, PP

• Engineering Plastics – e.g., PA, PC, POM

2 - By commodity plastic types (general-use plastics):

• PET, HDPE, PVC, LDPE, PP, PS, and Other (e.g., PC, acrylic)

3 - By thermal behavior:

• Thermoplastics can be melted and reshaped multiple times (e.g., PE, PP, ABS)

• Thermosetting plastics harden permanently and cannot be remelted (e.g., Bakelite, Epoxy)

If based on their chemical structure and usage, plastics are commonly categorized into three main groups:

• Styrene Plastics – known for rigidity and dimensional stability such as AS, ABS, SAN, GPPS, HIPS

• Olefin Plastics – lightweight with excellent chemical resistance such as PP. LDPE, HDPE

• Engineering Plastics – high-performance materials for demanding applications such as PA, PC, PBT, PMMA, POM, TPE

If based on characteristics, typical applications, and recyclability, there are 7 main categories of plastic, each represented by a number and abbreviation typically shown at the bottom of plastic items as Resin identification code (RIC)

• 1 - PET: widely used for beverage bottles, food packaging, and textiles

• 2 - HDPE: commonly found in milk containers, detergent bottles, and some shopping bags

• 3 - PVC: used in piping, vinyl siding, and flexible packaging

• 4 - LDPE: appears in plastic wraps, grocery bags, and squeezable bottles

• 5 - PP: used for yogurt cups, caps, and food storage containers

• 6 - PS: found in foam packaging, disposable utensils, and takeout boxes

• 7 - Other Plastics include materials like polycarbonate (PC) and acrylic, typically used in electronics, medical tools, and specialty products

Masterbatch is a concentrated mixture of pigments or additives encapsulated in carrier resin, designed for easy use and precise, consistent coloring in plastic processing

Compound refers to ready-to-use plastic, pellets pre-blended with additives, pigments, or fillers, tailored for specific functions such as conductivity, flame retardancy, or biodegradability with the color of customer choice

Pigment is a colorant , normally in powder form, used to add color to plastics, requiring dispersion into the base polymer during processing

Plastic coloring (or plastic colorants) refers to the materials and processes used to add color to plastics. This can be done in several ways, depending on the application and customer requirements:

• Pigments – Fine solid particles that provide strong, stable colors

• Masterbatch – Concentrated mixtures of pigments and additives, supplied in pellet form, which are mixed with natural plastic resin during processing

• Compounds – Ready-to-use colored plastic pellets, where pigments and additives are already mixed into the resin

Colorants are important not only for aesthetics but also for branding, product differentiation, and compliance with industry standards (e.g., food contact safety, weather resistance, heat stability)

At Sekai, we specialize in plastic coloring. We can:

• Develop custom colors to match your exact requirements

• Ensure consistent quality with every production lot

• Offer technical support on dosage, processing, and performance

UL (Underwriters Laboratories) is a global safety certification company that tests and certifies products to ensure they meet strict safety, performance, and compliance standards. UL certification is widely recognized in industries such as electronics, automotive, construction, and plastics

For plastics, UL testing often includes:

• Flammability ratings (UL 94)

• Electrical properties

• Thermal performance

• Safety compliance for end-use applications

At Sekai, we have materials that are UL-certified. Customers can inquire with us for the list of UL-certified grades available to match their requirements