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Bimodal high density polyethylene, HDPE

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We will try to imagine how bimodal molecular weight distribution rise. We will focus on two main properties: processing and mechanical . We start from normal (unimodal) molecular weight distribution (please, start to analyze the graph). Macromolecules with short chains , are easiest to process, polymer has lower viscosity , long chains are responsible for mechanical properties the grow. Considering, what left (middle), can be replaced. The idea was simple, eliminating average properties, we receive polymer with key properties. Return to the most important, processing and final product properties , considering molecular weight distribution . Short fractions or single monomers are gaseous substance, waxes, their impact is questionable (easy degradation, responsible for bad odor) and appear for unimodal distribution , changing the distribution we eliminate them. Long fractions generally affect mechanical properties , e.g. stiffness , it is possible to reduce wall thickness (sho...
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Safety precautions for extrusion blow molding

Safety is everyone's responsibility in the workplace. Safety is most often related to good maintenance practice and good housekeeping. Safety needs to be an attitude that is always present in your daily activities. Employees should not be hesitant to voice safety concerns in the workplace. Management is just as committed to safety as the operators on the floor; the primary difference is that the operators are usually the closest to unsafe conditions; keep management advised of unsafe conditions. The following list includes items which should be maintained to assure a safe working environment: 1. Floor and machine should be kept free of oil. 2. Floor and machine should be kept free of pellets. 3. Never reach over or under machine guards. 4. Never climb between the tie bars when hydraulic pumps are running. 5. Never disconnect or by-pass safety switches on guards. 6. In order to prevent mechanical hazards such as limbs being drawn into or trapped in the machinery, operators shoul...
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Head tooling – extrusion blow molding

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Mandrel and die dimensions are estimated based on container dimensional data, container symmetry, blow-up ratio, targeted container weight, neck finish requirements and the type of material (degree of parison swell) that will be used to produce the container. An initial blow-up ratio must be calculated using the container design dimensions and the required parison diameter. The required parison diameter will depend on the relative size of the container, the container design (handle or no handle) and the container neck finish requirements. Initial blow-up ratios may be calculated using the following equation. Blow up ratio = Bd / Nd where: Bd = Bottle diameter, in Nd = Minimum neck diameter, in The blow-up ratio is compared with the maximum recommended blow-up ratio of the selected material. Blow up ratios of 2 or 3 to 1 are considered normal when molding commodity resins such as polyethylene. A blow-up ratio as high as 4:1 is a practical upper limit. The blow up ratio for large contai...
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