Extruded construction products

Rigid PVC extruded construction products take many forms. Typical are house siding, window profiles, storm doors, pipe, fencing, and various accessory items... 

Power density has increased significantly since the early days of extruder construction. A typical factor, and an important one for scaling up laboratory machines to production machines, is the ratio of screw shaft torque to centerline distance to the power of three. In the 1960s, a value of T/a3=5 Nm/cm3 was typical today values in excess of 13 Nm/cm3 are achieved. 

Worldwide, polyvinyl chloride (PVC) is one of the most extruded polymers by volume. While environmental and health concerns has created lost market share in certain applications, PVC has made large gains in other areas, such as the replacement of wood and aluminum profiles in building construction products. Blown film extrusion is also used in the manufacture of products from PVC. Though PVC has limited thermal stability, it has good melt strength, which lends itself nicely to blown film extrusion. 

Paraloid KM 377 is for extruded vinyl products for the construction industry, with improved impact and weather resistance and good gloss-holding properties. 

Conveyor systems are applied in a number of areas in the rubber industry. The types used can range from simple canvas belt conveyors used for haul-off from conventional extruders, to systems used for transport and cooling of profile products, both in and emerging from continuous vulcanisation units. The latter types have to be resistant to the temperatures used in such systems and are variously constructed from glass fibre-reinforced polytetrafluoroethylene or a silicone rubber covered belt. 

Extruders are normally classified by their method of construction, i.e. twin screw or single screw and the operating conditions, i.e. cold extrusion or extrusion cooking. Cold extrusion is used to make liquorice and pasta among other products and so is outside the scope of this work. Extrusion cooking, which is defined as heating the product above 100 °C, has many uses. 

The principal use of LDPE and LLDPE in building products is as a film water barrier under below-grade floors as a wall vapor barrier, though PVC is typically preferred and as temporary enclosure film during construction. The film is made either by extruding a thin-walled tube, which may be slit or wound up direcdy, or by extmsion through a slot die and cast direcdy on to a cold roll, cooled, then wound up. The former method is more widely used. A much smaller use for low density polyethylene is in piping. 

Another PVC siding is an extruded product of an internally ribbed, dual-wall profile. A conventional screw extruder, with a vacuum sizer cooled with water and air, forms a product about 20 cm wide with 160 mm walls and 80 mm ribs on 25 cm centers. The total thickness is about 0.64 cm. The ribs provide rigidity and strength and the dual-wall construction adds thermal insulation. No backing or core is used. 

In its simplest form an extruder consists of a body with a rotating axis equipped with blades, the so-called worm which extrudes the clay through a die, an opening with a special shape and construction which varies according to product requirements. During this extrusion the pressure on the clay is gradually increased to a maximum value. Near the die the pressure drops to zero when the clay is extruded. 

Wire and Cable. PVC has been used in wire and cable applications since Wodd War II, when the U.S. Navy demanded lower combustibility materials in construction. These products are manufactured by cross-head extrusion, usually from pellet compounds on single-screw extruders. Some line speeds are 1524 m (5000 ft) per minute (60 mph). The compounds are optimized for the requirements, including low temperature flexibility, high use temperature, especially low combustibility, weatherability, and high resistance to cutthrough. 

Louis Hegedus Coming from the specialty chemicals applications, I would like to further emphasize what Sheldon Isakoff said. Take polyethylene, which our company uses extensively for a variety of applications. What do we do with it We fill it, modify it, functionalize it, formulate it, compound it, extrude it, laminate it, and end up with such vastly different products as battery separators, membranes, construction materials, insulation materials, battery electrodes, and microfilters. It is amazing what you can do with any given polymer. Much research emphasis today is on the properties of bulk polymers themselves. There is a whole science associated with com-... 

Soy, and Other Legume Proteins Two quite different product types have been constructed by extrusion, high-density flaked structures for meat analogues, and lower density and crispy products for high-protein snacks. The latter uses conditions similar to that of starch-based cereal extrusion to obtain low bulk density in the expanded product the former uses a higher water content in the extruder barrel and lower exit temperatures to obtain a dense material with open pores or even flaked structmes. For these two types of processes, molecular changes in the extruder barrel are not dissimilar. Post-die structuring of the extrudates determines final product properties. 

Aluminum. The majority of aluminum containers are of monobloc (one-piece) construction, impact extruded from a slug of lubricated aluminum alloy. These containers are widely used for many products and are available in a vast array of heights and diameters. Because these containers lend themselves to additional shaping, many unusual shapes can be found in the marketplace. They may also be coated after the extrusion process. 

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