Melt flow rheological testing

Melt index (melt flow rate) test rheological tests... 

Rheology is a complex subject, and in the formulated colorant industry two simplified approaches have served well in the majority of cases. These are the single-point method, melt flow, and the molding simulation test, spiral flow. 

Rheological data provides information about how a melted material will perform (flow) under processing conditions. Perhaps the most important rheological test used by plastics processors is the melt index test. Though rheologists scoff at this notion, it is nevertheless vitally important because virtually every manufacturer that employs an extruder, injection molder, or blow molder uses the test method or the data it yields. 

In addition to thickness reduction, the rheological process obviously is characterized by the size of the squeeze-out of the seam, which is produced during melt flow. Type and form of the squeeze-out at the same time influence the notch effect in the welded area and thus the time-to-failure in the long-term tensile test. Measurements of form and area of the squeeze-out were also used for the description of the quahty of dual hot wedge seams, see (Bielefeldt et al. 1991 Corbet and Peters 1996). This quantity alone, however, cannot completely and unambiguously characterise the welding process. 

When rheology is applied to polymer blends and polymer composites, standard practice is to form the blend or composite in a separate step by, for example, using a twin-screw extruder or batch mixer. Melt flow properties of resulting materials are obtained by placing solidified specimens in a rheometer test cell of a laboratory rheometer instrument, melting the... 

Firstly the material viscosity was examined to evaluate the antidromic influences of the solid fibers on the one hand and the low-viscous metal melt on the other hand. The rheologic tests were performed on an on-line rheometer for the injection molding machine with a slit capillary of 1 mm height and 20 mm width. Three pressure sensors are located along the flow path each 50 mm apart. 

Lee et al. [2007] studied the rheological behavior of poly(ethylene-co-vinyl acetate) (EVAc 40 wt% VAc) and its CPNC with < 10 wt% C30B the tests were conducted under steady-state and small oscillatory shear flow. The samples were prepared by melt compounding at 110 C for 25 min, which resulted in a high degree of dispersion. The flow behavior was quite regular, well described by the Carreau-Yasuda equation [Carreau, 1968,1972 Yasuda, 1979] ... 

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