Quality control tests temperature

The samples need to be brought to controlled test conditions before the test is carried out. If they were used as a quality control test, the product in many cases would be at the customer before the test was completed. A typical example is that tests such as the tensile tests require a week to settle down before the test is carried out after the 18-hour cure cycle. In many cases an approximate value is obtained by testing as soon as the sample has reached room temperature after it has had its full cure. 

Formaldehdye generation and recovery studies 3.) Air exchange measurement techniques 4.) Preconditioning of test boards 5.) Temperature effect on chamber formaldehyde concentrations 6.) Relationship of popular quality control test methods to the large chamber 7.) Loading, air exchange rate, and wood product combination effects on chamber formaldehyde concentrations 8.) Chamber Round Robin studies between Georgia-Pacific s chamber and other outside lab chambers 9.) Chamber concentrations and its relationship to actual field measurements. 

All quality control tests and specimen conditioning are conducted under carefully controlled environmental conditions, i.e. temperature = 24 H3.5 C, 50h 5% relative humidity and a background formaldehyde level of less than 0.1 ppm. Ourselves as well as others have found that temperature effects on the quality control test values follow the same pattern observed in the large scale chamber (30). In short, the Berge temperature correction can be applied to the quality control test methods. 

Most measurements of set on rubbers are made not to obtain data to relate to a practical application but as a quality control test to indicate the state of cure. The test conditions are then arbitrary and usually involve straining at an elevated temperature. Short-term tests do not necessarily correlate well with long-term performance [6]. 

Gel time is the time required for a liquid material to form a gel under specified conditions of temperature as measured by a specific test. The gelation is generally caused by cross-linking of the polymer Thus gel time is a measure of the reactivity of polymer systans. It is often used as a quality control test to determine consistency from resin to resin and from catalyzed batch to catalyzed batch. 

If the greatest possible degree of attention must be directed toward completeness in the trace range, decomposition in a closed system is preferred. Ensuring essentially complete decomposition requires the application of high temperature over a period of at least two hours. If sample preparation mu.st be accomplished more rapidly (as in the case of food analysis, environmental studies, or quality control) tests should be conducted on the feasibility of a microwave-assisted process or direct analysis (see Section 6.2.8.2). 

It is always good design practice to minimize the amount of molded-in stress. However, most designs retain some level of this kind of stress. If this must be limited to ensure proper part functioning, a quality control test with limits should be specified, such as a part s heat-distortion temperature or impact, flexural, or tensile ratings. 

Current industrial practice in the rubber industry is for these instruments to measure a property, usually stiffness, changing progressively with time at a set temperature. The temperature may be set so as to equate to typical cure conditions, or may be of an arbitrary nature if used for quality-control testing. The sample of unvulcanised rubber used will have a hot stiffness or viscosity before any crosslinking occurs. This will increase from a minimum value to a... 

The ability of the material to flow is measured by filling a mold with the plastics material under a specified condition of applied temperature and pressure with a controlled charge mass. The flow tests are used as a quality control test and as an acceptance criterion for incoming raw materials. 

The so-called flow temperature cannot be considered to be either the processing temperature or the maximum service temperature. It is obtained using the highly arbitrary Rossi-Peakes flow test (BS 1524) and is the temperature at which the compound is forced down a capillary of fixed dimensions by a fixed load at a specified rate. It is thus of use only for comparison and for quality control purposes. Since the rates of shear and temperatures used in processing are vastly different from those used in this test, extreme caution should be taken when assessing the result of flow temperature tests. 

To ensure quality control material suppliers and developers routinely measure such complex properties as molecular weight and its distribution, crystallinity and crystalline lattice geometry, and detailed fracture characteristics (Chapter 6). They use complex, specialized tests such as gel permeation chromatography (2, 3), wide- and narrow-angle X-ray diffraction, scanning electron microscopy, and high-temperature pressurized solvent reaction tests to develop new polymers and plastics applications. 

Off-the-shelf catalogue sales of micro reactors have just started [15]. With an increasing number of commercial products, quality control will become more important. Brandner et al. describe quality control for micro heat exchangers/reactors at the Forschungszentrum Karlsruhe [23]. All manufacturing steps are accompanied by quality control and documentation. Leak rates (down to 10 mbar 1 s for He) and overpressure resistance (up to 1000 bar at ambient temperature) are measured. Under standardized conditions, the mean hydraulic diameter is determined. Dynamic tests supplement this quality control. 

For details of the test methods used to measure physical properties reference is made to Handbook of Plastics Test Methods or the more recent Handbook of Polymer Testing [2, 3]. Standard tests have their limitations most were intended for quality control rather than prediction of service performance and produce arbitrary rather than fundamental measures of the properties. They do have the advantages of making data compatible with others and often have known reproducibility. In many standard methods the user is encouraged to opt for standard or preferred conditions which may not have relevance to the service conditions of the product. It is then sensible to base the testing on standard methods but to use more relevant conditions of, for example, time, temperature or stress. 

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