Spiral flow tests

With TS molding compounds, the flow can be defined as a measure of melt viscosity, gelation rate, and subsequent polymerization, or cure (Chapters 1, 6, and 7). Flow occurs within a dynamic chemical reaction initiated by the application of the above three factors, with the rate of reaction accelerating in proportion to the inerease in heat (Fig. 7-5). A valid rule of 

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A widely used test for mouldability evaluation is the spiral flow test (Fig. 24.4). In this test the mould has the form of a spiral the polymer melt flows into this mould under pressure and freezes in the spiral, the length of the polymer spiral being the test result. Mould geometry, temperature and pressure are standardised. 

FIG. 24.4 The spiral flow test. The inlet cone is in the middle of the spiral. 

Weir et al. (1963) have shown that for a series of polypropylenes there is a significant relation between asrv and the spiral length (in the spiral flow test). 

MSF melt spiral flow (test) NAAEE North America Association for Envi-... 

S.Z. Gebrehiwot, Manufacturing and rheological analysis of spiral flow test piece. Degree Thesis, ARCADA, 2014... 

Fig. 10-9. Spiral flow test mold and plastic molded spiral test specimen, using an injection molding machine.

Spiral-flow test n. A method of evaluating the molding flow of a resin to injection or transfer molding in which the melt is injected into a spiral runner of constant trapezoidal cross-section with numbered and subdivided centimeter (or inches) marked along the runner. The mold is filled from a sprue at the center of the spiral and pressure is maintained until flow stops, the number just aft of the molded-spiral tip giving the flow distance. The spiral-flow test has been widely used since it was introduced in the early 1950s but has been standardized in USA only for thermosetting resins, in ASTM D 3123. 

Spiral flow (test and mold). There are two types of spiral flow molds— one for the very soft flow encapsulation compound generally associated with the encapsulation grades of the epoxy family of compounds and a spiral flow mold, which is used when testing the high-pressure phenolic, DAP, melamine, urea, epoxy, and thermoset polyester com-poimds. 

Figure 2.27 Spiral flow test and mold (Emmi).

Fig. 5.15. Typical cull and spiral from a spiral flow test.

Testing of lubricants is based on the determination of the flow behavior of plastic melts (capillary viscosi-metry, spiral flow test, demolding force, by plasto-graph, extrusiometer, melt strength, roll-mill tests, etc.) or by finished part testing (gloss and smoothness, slip measurements, determination of static friction, etc.). 

The flow properties of a material can also be investigated using a spiral flow test. The melt is injected into a spiral mould cavity. The melt will freeze at a certain distance along the spiral charmel (spiral flow length) depending on the flow properties and cross-sectional thickness of the spiral. The raw material manufacturer usually gives these values as material specifications. 

Receiving Inspection. Many types of tests have been devised for testing raw materials. Depending upon the severity of the need for inspection, the types of tests selected may vary from being basic and simple to sophisticated and complex. Some of the most common basic tests are the melt index test, specific gravity, bulk density, spiral flow test, and viscosity tests. Gel permeation chromatography, infrared analysis, thermal analysis, and rheometry are some of the more elaborate raw material quality control tests. These tests are discussed in detail in Chapter 7. Some processors also choose to mold test bars from a small sample of raw material and conduct physical tests such as tensile, impact, and flexural tests and then evaluate the results to see if they meet the preestablished specifications. 

Spiral flow test A method for determining the flow properties of a plastic material based on the distance it will flow under controlled conditions of pressure and temperature along the path of a spiral cavity using a controlled charge mass. 

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