External Structure Materials & Durability

The types of materials used to construct the external structure and internal parts of a vacuum cleaner play a major role in the length of its life span as well as the extent of its maintenance expenses. Typically, vacuum cleaners are made of a combination of metals and various synthetic plastics. With the development of the Plastics Industry, many parts which were once metal are now made of much lighter and often stronger plastics. While reducing the production costs considerably, this change over has also made vacuum cleaners much lighter and easier to use. The key to durability is often in the excellence of design as well as the types of plastics used for various parts.

	A Bit of History

Prior to the early 1960's, canister vacuum cleaners were primarily constructed of stamped steel cases with cast aluminum attachments and trim pieces. Uprights had cast aluminum bases with steel, aluminum or bakelite motor hoods. This made for very durable but heavy vacuum cleaners. Gradually, we saw many trim pieces and motor hoods start to be molded from various plastics. The rubber used earlier to make furniture guards, handle grips and cords was replaced with a soft, flexible synthetic plastic called vinyl (polyvinyl chloride).

I can well remember the very first upright base which was not cast aluminum. It was a pure white lightweight base on a General Electric upright introduced in the early 1960's. We obtained one of these bases to show customers just how tough this new Lexan base developed General Electric really was. We jumped on it, hammered on it, put it through all kinds of abuse, and it still didn't break. This new Lexan polycarbonate resin discovered by Dan Fox at General Electric in 1953 and later used to make this new base started a new trend in the vacuum cleaner industry. Eureka vacuums started using Lexan for their upright bases around 1975 and continues to do so even today. Hoover and most other companies switched to using a similar high impact plastic base shortly after that.

Around 1966 Eureka developed a new canister series with a case made of high impact plastics instead of steel. It was quite revolutionary in design and construction with a shape like a flying saucer, having a hose that wrapped around the middle. A number of these were sold but the idea just didn't seem to fly. After that series they went back to exclusively using steel for canister cases for many years. Then around 1985 Eureka came out with their award winning plastic Mighty Mite compact canister series and their full sized Express series, both of which had all plastic cases. After overcoming a few glitches, like wheels breaking and falling off while still on the assembly line, these new series did well and lead to their current designs and construction. Hoover and most other companies switched to plastics for their case construction around the same time.

	Today's Uses of Structural Materials

Most upright and canister cases are now constructed primarily of ABS plastics (acrylonitrile-butadiene-styrene) with steel, polycarbonates and other high impact plastics used where additional strength is needed. ABS plastic works well for the large case designs where an economical, lightweight and tough material is needed. It is basically polystyrene except that a small amount of styrene-butadiene rubber for better high impact resistance and acrylonitrile for hardening are added to the styrene before it is polymerized. This allows it to flex under impact while still being rigid enough to keep the required shape.

Parts made with Lexan and other polycarbonates are extremely tough with the ability to maintain their physical shapes even under great stresses over a wide range of temperatures. This along with their ability to flex slightly with impact makes them ideal for the main base on uprights as well as the suction fan in dirty-air upright designs. Eureka uses Lexan in the bases and fans of their Heavy Duty Sanitaire and Commercial Sanitaire uprights. By using Lexan and Steel extensively in their construction, Sanitaire uprights are very durable even with hard commercial use.

A few vacuum cleaners, like the Kirby and TriStar still have metal main cases. Kirby uses cast aluminum for the housings on their metal uprights. The Tristar has a cast manganese-aluminum alloy case which is extremely tough. Kirby and TriStar are sold exclusively by in-home demonstrations. Some central vacuum systems use a combination of steel and ABS plastics while others are all steel or aluminum.

	Various Plastics used in External Structures

There are a number of synthetic resins used in constructing vacuum cleaners. They are created primarily from petroleum derivatives through a process called polymerization. It is a process in which small molecules called monomers are linked to form giant long-chain molecules called polymers. This is done by combining chemical compounds, often with the application of pressure and heat, to cause a chemical reaction which links the individual monomers together to form long-chain molecules. These are entangled with each other and considerable force is needed to disentangle them. These polymer resins are commonly called plastics since they can be molded and shaped. In thermoplastic resins, when heated, the chains move apart enough to permit them to slide over one another. This allows thermoplastics to be melted, then molded or otherwise shaped into usable items. Thermosetting resins, like epoxy and bakelite, can not be melted over and over again for recycling like the thermoplastic resins are. The following is a list of the more common plastics used for vacuum cleaner external structures:

Lexan

In 1953, while working for General Electric, Dan Fox discovered Lexan polycarbonate resin. Lexan is GE's registered trademark for this particular polycarbonate resin. For more information, see General Electric's articles on GE Plastics.

Polycarbonate

An extremely tough and strong synthetic plastic with the ability to maintain its shape and size even under great stresses over a wide range of temperatures. It is an ideal engineering plastic since it can be injection molded, blow molded, or extruded. Due to its excellent properties, it is often used for creating upright bases, cord hooks and other parts which must withstand high stress. Created by a polymerization process, it contains long chains of linear polyesters of carbonic acid and dihydric phenols like bisphenol A.

ABS Plastics

Acrylonitrile-butadiene-styrene plastics are used extensively in the molding of vacuum cleaner cases and trim parts. It is an economical plastic which is lightweight but strong and resists stains and chemicals. ABS plastic is an enhancement to polystyrene plastic made by adding a small amount of styrene-butadiene rubber for better high impact resistance and acrylonitrile for hardening to the styrene before it is polymerized. This allows it to flex under impact while still being rigid enough to keep the required shape.

Polystyrene

Polystyrene is an ideal injection molding plastic which is hard, extremely transparent and a good insulator although it will soften in boiling water, is brittle and burns readily. It was first marketed by the Dow Chemical Company in 1937. Polystyrene is enhanced with additives during the polymerization process to make ABS Plastic which overcomes many of its weaknesses, making it very suitable for vacuum cleaner cases. Polystyrene is produced by using liquid benzene and the gas ethylene to make liquid styrene. This styrene is then polymerized by adding some chemicals, heating it and putting it under pressure. High impact polystyrene can be made by adding a small amount of styrene-butadiene rubber to the styrene before it is polymerized. Thin polystyrene films are often used to make fresh food containers due to their high gas permeability and good water-vapor transmission.

Vinyl

Polyvinyl chloride, typically called vinyl or PVC, is a very versatile thermoplastic material. It is strong, easily colored and resists abrasion. It can be made rigid for making piping like used for water systems, drainage systems and central vacuum systems or very flexible for making electrical cord jackets, water or vacuum hoses and protective furniture guards. The softness and flexibility is created by mixing special chemicals called plasticizers with the polymer during the molding process. Pigments are added in a similar manner. The polymer itself is typically made from ethylene and chlorine. In its rigid form, it has one of the highest combinations of stiffness and impact strength.

Nylon

Nylon is one of the toughest, strongest and most elastic substances. It is ideal for use between rotating wheels and their axles or rotating axles and the main housings to reduce wear. Due to its ability to resist abrasion, it is often used to make gears for floor polishers and conditioners, power driven uprights, etc. Yet another use is in manufacturing synthetic bristles for vacuum cleaner attachments. The discovery of nylon in 1935 by Wallace H. Carothers, while working at the E. I. du Pont de Nemours & Company (now Du Pont), is considered one of the most important chemical discoveries in history. Nylon is produced by combining hexamethylenediamine and adipic acid and then polymerizing the solution by heating it under pressure.

Bakelite

Bakelite is the first completely synthetic plastics resin which was invented in 1909 by Leo H. Bakeland, a New York chemist, while attempting to make a better type of varnish. It is an important thermosetting resin made from phenol and formaldehyde which can be injection molded to make parts which are resistant to heat, chemicals and moisture. It is also an excellent electrical insulator, making it ideal for switch and motor housing. Early upright vacuum cleaner motor housings and some motor hoods were made from Bakelite. Today, most upright vacuum cleaner motor housings are made of various thermoplastics which are more economical to produce.

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