Is there any bench top inspection I can do on the turbo? Any turbo tips while the turbo is off the car?
Catalysts[ edit ] Polyurethane catalysts can be classified into two broad categories, basic and acidic amine.
Tertiary amine catalysts function by enhancing the nucleophilicity of the diol component. Alkyl tin carboxylates, oxides and mercaptides oxides function as mild Lewis acids in accelerating the formation of polyurethane.
A typical Lewis acidic catalyst is dibutyltin dilaurate. The process is highly sensitive to the nature of the catalyst and is also known to be autocatalytic.
A variety of specialized catalysts have been developed. They take the form of polydimethylsiloxane-polyoxyalkylene block copolymers, silicone oils, nonylphenol ethoxylates, and other organic compounds.
In foams, they are used to emulsify the liquid components, regulate cell size, and stabilize the cell structure to prevent collapse and sub-surface voids. Production[ edit ] Polyurethanes are produced by mixing two or more liquid streams. The polyol stream contains catalysts, surfactants, blowing agents and so on.
The two components are referred to as a polyurethane system, or simply a system. The isocyanate is commonly referred to in North America as the 'A-side' or just the 'iso'.
The blend of polyols and other additives is commonly referred to as the 'B-side' or as the 'poly'. In Europe the meanings for 'A-side' and 'B-side' are reversed.
Polyurethane can be made in a variety of densities and hardnesses by varying the isocyanate, polyol or additives. Health and safety[ edit ] Fully reacted polyurethane polymer is chemically inert. It is not regulated by OSHA for carcinogenicity. Top, untreated polyurethane foam burns vigorously.
Bottom, with fire-retardant treatment.
Polyurethane polymer is a combustible solid and can be ignited if exposed to an open flame. Green Science Policy Institute states: Consumers who wish to reduce household exposure to flame retardants can look for a TB tag on furniture, and verify with retailers that products do not contain flame retardants.
Isocyanates are known skin and respiratory sensitizers. Additionally, amines, glycols, and phosphate present in spray polyurethane foams present risks.
Manufacturing[ edit ] The methods of manufacturing polyurethane finished goods range from small, hand pour piece-part operations to large, high-volume bunstock and boardstock production lines. Regardless of the end-product, the manufacturing principle is the same: Dispensing equipment[ edit ] Although the capital outlay can be high, it is desirable to use a meter-mix or dispense unit for even low-volume production operations that require a steady output of finished parts.
Dispense equipment consists of material holding day tanks, metering pumps, a mix head, and a control unit. Often, a conditioning or heater-chiller unit is added to control material temperature in order to improve mix efficiency, cure rate, and to reduce process variability.
Choice of dispense equipment components depends on shot size, throughput, material characteristics such as viscosity and filler content, and process control.
Material day tanks may be single to hundreds of gallons in size, and may be supplied directly from drums, IBCs intermediate bulk containers, such as totesor bulk storage tanks. They may incorporate level sensors, conditioning jackets, and mixers.
Pumps can be sized to meter in single grams per second up to hundreds of pounds per minute. They can be rotary, gear, or piston pumps, or can be specially hardened lance pumps to meter liquids containing highly abrasive fillers such as chopped or hammer milled glass fibres and wollastonite.
A high pressure polyurethane dispense unit, showing control panel, high pressure pump, integral day tanks, and hydraulic drive unit. A high pressure mix head, showing simple controls.
A high pressure mix head, showing material supply and hydraulic actuator lines. Mix heads can be simple static mix tubes, rotary element mixers, low-pressure dynamic mixers, or high-pressure hydraulically actuated direct impingement mixers.
Add-ons to dispense equipment include nucleation or gas injection units, and third or fourth stream capability for adding pigments or metering in supplemental additive packages. A low pressure mix head with calibration chamber installed, showing material supply and air actuator lines.
Low pressure mix head components, including mix chambers, conical mixers, and mounting plates. Tooling[ edit ] Distinct from pour-in-place, bun and boardstock, and coating applications, the production of piece parts requires tooling to contain and form the reacting liquid.RTV-1 silicone rubbers are one-part, ready-to-use RTV systems.
They consist of polydimethylsiloxane, curing agent, fillers and additives. After application, they are crosslinked by contact with atmospheric moisture releasing byproducts in the process.
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