Speed of application

As discussed earlier in this chapter, PSA performance is very much dependent on temperature, speed of application or removal, and surface contamination. 

Modem furniture polishes are designed for a wide variety of surfaces, eg, plastics, metals, and synthetic and natural resin coatings. Furniture polishes impart shine and provide protection from abrasion, marring, and spills. The formulations clean well in many cases. In common with most other polishes, furniture polishes are characterized by ease and speed of application and of buffing, and by either the absence of objectionable odors or the addition of pleasing ones. 

The use of durometers on a stand is supported in 7619-1, reflecting the practice of using them as an alternative to IRHD. In fact, type AM is specified as always being so used, which completely negates it being a portable instrument. When used on a stand, there are requirements for a timer, the load on the foot and speed of application. Also, the instruments can use any suitable transducer to measure indentation and be connected to a computer in the same way as for dead load testers. 

The hydrodynamic problem in coating flows is to define the steady solution giving the relation between the film-forming geometry, the liquid properties, the speed of application of the film, and a desired coating thickness. The analysis is complicated by several factors, one of which is that such flows are essentially two-dimensional. More importantly, they are free surface—type flows, which are basically nonlinear in that the region occupied by the liquid is not known initially but is defined by the solution. Moreover, such free surface flows must be analyzed to determine if they are stable. 

Application of the paints and varnishes, methods of application of the paint or varnish, e.g. speed of application of the paint. 

Method Speed of application Metal dilution Integrity of the weld Ease of automation... 

Fig. 27 shows an automatic spraying machine where two guns move automatically back and forth on top of a conveyor. This is a frequent installation for flat and large panels sandwich panels, wood and decorative panels, laminating. The speed of application may reach 10 to 20 m /min. 

Early types of coatings included silicone oils and rubbers, polyamideimide, cellulose lacquers and blocked urethanes. Hot melts have also been proposed n -1 . It proved to be difficult to overcome problems in handling, stability, durability and speed of application (drawing speeds of up to 10 m s are required). 

Sandblasting is primarily a surface treatment that allows removal of small quantities of concrete from the surface but is more applicable to removal of stains or surface deposits. Compared to most methods, sandblasting offers little control — even with vacuum collection devices — due to the high speed of application and the unpredictable size grading and deflection pattern. Sandblasting can result in significant redeposition of PCB on other surfaces through sand or in air. 

Scabbling refers to the use of rows of small, high pressure impact pistons to break up and remove concrete. This technique, frequently used in the nuclear industry for decontamination, is applied in a similar fashion to grinding. Vacuum collection devices are often included as attachments but are relatively ineffective due to the high speed of application and the unpredictable size grading and deflection pattern involved in scabbling. 

Hand operated glue guns. These allow a thin film to be applied with speed and accuracy. The adhesive is supplied under pressure by the use of a hose and by adjusting the air pressure the speed of application can be matched to the desired flow. 

Uses Gloss aid, spreading agent in vinyl and rubber treatment gloss aid in wash and wax formulations soKener in textile applies, for variety of fabrics lubricant and antistat for wide variety of syn. and nat. fabrics Features Rec. where speed of applic. is important min. yellowing Properties Liq. insol. in water low vise. 100% act. 

The factors which affect the deposition of the adhesives may be summarised as viscosity of the adhesive pumpability of the adhesive pressure in the delivery systems nozzle diameter surface conditions of the panel speed of application. 

Action can be taken to regularise the factors that can affect deposition, with the exception of speed of application which in a manual situation is controlled solely by the operator too high a speed gives less material and conversely too low a speed gives too much. 

The only way to control the rate/speed of application is to automate the process most of the world s automotive manufacturers using adhesives in both structural and semi-structural roles have turned to some form of automation and so control the rate of application and the location of the deposited material. 

Although the speed of application was variable when carried out manually, the operator had the ability to adjust to change. The operator is fully adaptive and can therefore adjust the work rate to compensate for change. Automated systems do not currently have that ability and operate to a set of pre-programmed conditions, hence the need to ensure that everything else is fully controlled to very close limits. 

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