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ROTATIONAL MOLDING VERSUS INJECTION MOLDING IN AUTOMATED COLLECTION In the 1970's, automated refuse collection was invented and further developed in the United States. Early studies revealed that the containers to be used in this application had specific molding and material requirements to withstand the rigors of this method of service. Due to the clamping force and impact associated with collection by a hydraulic lifting arm, the polyethylene materials required great impact resistance and elasticity. In short, flexible yet stiff, without being brittle. Also, these containers had to be abrasion and impact resistant. Although injection molding was available at the time, rotational molding was selected because of its capacity to produce large, stress free uniform products made from specialized materials. Collection methods in Europe have centered primarily around relatively slow semi automated systems using heavy injection molded carts. These carts have lower physical demands on them and accordingly, different material requirements. Injection molded carts are produced under extreme pressure with a great degree of internal stress molded into the product. They tend to be heavier, more rigid, and thicker than roto molded containers to compensate for the lower physical characteristics of the materials used in this process. Injection molding is a very precise process and is excellent for use in producing products for use in a non stressed environment. However, the primary concern with injection molding for use in automated collection is that the lower physical characteristics of the materials (elongation, impact resistance, and environmental stress crack resistance) over time will prove themselves to be significantly less effective than the materials used in rotational molding for the same containers. Although paid laboratory tests show that these containers can be resilient in a controlled environment, there is simply not enough practical field testing to prove that they are equivalent in field service over time to prove they are viable or equivalent to rotational molding. Furthermore, as univers arms capable of collecting small containers become more prevalent, the clamping pressures with these will inflict additional damage on the injection products due to their lack of flexibility. The oldest significant automated system using injection molding was not installed until the early 1990's. Rotationally molded products have been in automated collection since the 1970's. rot- inj.ruc