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Plastics Profile

ABS Resins Give Manufacturers Versatility

By Gary O’Neill

Acrylonitrile butadiene styrene (ABS) resins are among the most versatile polymers in the styrenics family. ABS resins offer cost-effective processing and increased end-use performance for applications in a variety of market segments, including automotive, small and large appliances, information technology equipment, consumer electronics, building and construction, medical and office furniture. ABS is also often combined with other resins to produce blends and alloys, which feature an equally broad range of properties and benefits.

Advantages of ABS Resins

The primary features and benefits of ABS resins are derived from the three building blocks used in their development: acrylonitrile, butadiene and styrene. Heat stability and chemical resistance are derived from acrylonitrile, while butadiene provides toughness and impact resistance. Styrene imparts rigidity and processability to ABS resins. By adjusting the relative molecular weights of these three building blocks, ABS resins can be produced with a wide range of properties.

While ABS resins are well known for their toughness and durability, they are becoming increasingly recognized for their processability and cost-efficiency. The unique balance of properties associated with ABS resins make them ideal candidates for almost any application in which practical toughness, high modulus, dimensional stability and good aesthetics are important considerations.

Forming Techniques

Although ABS resins are most commonly associated with injection molding, they can also be blow molded or extruded into sheet for thermoforming applications. Processing the resins is dependent, to a great degree, on the grade of ABS resin being used and on the end-use requirements of the application. Two processes are used to produce ABS resins — mass and emulsion.

The process differences and resulting product characteristics between mass ABS and emulsion ABS products are very distinct. The mass process Dow Plastics uses for its MAGNUM ABS resins, for example, produces a very pure product with minimal impurities resulting in a very “white” resin. Because mass is a continuous process, there is excellent lot-to-lot consistency. In comparison, the emulsion process produces products that have high levels of impurities and are more “yellow” in color. The emulsion products are manufactured via a batch process, rather than continuous and are less consistent from batch-to-batch.

Lowering Total Costs

Two general trends impacting the use of ABS resins involve value engineering and the use of self-coloring, both of which enable molders and manufacturers to improve the productivity and cost-efficiency of their processes. Value engineering can involve moving “up” (i.e., from polypropylene or high-impact polystyrene to ABS) or “down” (from polycarbonate or PC/ABS resin to an ABS resin) the resin ladder.

The automotive market offers a good example of how value engineering to ABS resins can help improve not only the productivity and cost-efficiency of the manufacturing process, but the performance of the part as well. While some OEMs have value engineered “down” to polypropylene in recent years, ABS is becoming increasingly recognized for its superior adhesion properties and dimensional stability over wide temperature ranges. Also, the automotive industry uses PC/ABS blends to help manufacturers lower total system cost, reduce weight and improve durability in applications such as instrument panels, garnish trim, consoles and door panels.

In today’s aggressive marketplace, manufacturers and molders must continually lower costs, improve productivity and increase their competitiveness. Increasingly, molders and manufacturers are recognizing the advantages of using “natural-plus” ABS resins in conjunction with self-coloring. Self-coloring services for natural-colored engineering thermoplastics, such as the PROMATCH Service from Dow Plastics, enable manufacturers and molders to implement self-coloring processes, providing a less expensive, faster and more efficient coloring option. Converting to a self-coloring process gives companies the flexibility to produce colored parts for a wide array of products such as mobile phones, vacuum cleaners and electrical switches that have ever-changing styles and colors.

Self-coloring can provide a significant return on investment through reduced inventory, shorter lead times, reduced storage costs, outstanding color consistency and improved cost efficiency. For instance, with self-coloring, companies only need to stock one resin — natural-colored engineering thermoplastics. A small amount of colorant, calibrated to the exact pigment requirement is added to the resin. “Safety stock” or pre-colored resin inventories can be reduced or even eliminated, as only the natural resins and colorant need to be stored, lowering total costs for companies.

The future of ABS resins is likely to include the continuing development of higher-flow materials that provide reduced viscosities without sacrificing the toughness, heat resistance or chemical resistance typically displayed by an ABS resin. Other materials intended to meet the needs of more demanding applications are also likely to be introduced.

Gary O’Neill is the North American product market manager for Dow Plastics. For more information, contact Dow Plastics at (800) 441-4369 or visit www.dowengineeringplastics.com.

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