melt fracture

melt fracture

[′melt ‚frak·chər]
(mechanics)
Melt flow instability through a die during plastics molding, leading to helicular, rippled surface irregularities on the finished product.
References in periodicals archive ?
The purpose of these screening extrusion experiments was to briefly assess the effect of MW and MWD on the melt fracture characteristics of these CRPP materials.
During the production process, our light stabilizer helps to lower the tendency to melt fracture, making it suitable for highly demanding processing conditions involving high shear rates, pointed out Hermann Althoff, Senior Vice President, Performance Chemicals Asia Pacific.
Total says high extrusion speeds can be reached at low extrusion temperatures and without any melt fracture, while keeping an excellent surface finish.
High extrusion speeds can be reached at low extrusion temperatures and without any melt fracture while keeping an excellent surface finish, the company says.
The compound of CoBR with natural rubber was used as a reference for a BR grade which possesses good processability, as can be seen in figure 4a; while the standard NdBR (Buna CB24) compound produces smooth Garvey profiles at low extrusion rates; they turn rough at 90 rpm and finally exhibit melt fracture at 120 rpm (figure 4b).
The phenomena he considers include the transformation of the characteristic viscoelastic spectrum with molecular-weight change and/or dilution; the molecular-weight dependence of the zero-shear viscosity and of the steady-state compliance, and their respective transition points; the relation between viscoelasticity and diffusion; the damping function; and the slip-stick melt fracture phenomenon.
Chemist Koopmans and physicist, mathematician Jaap den Doelder (both with a giant chemical company), and Jaap Molenaar (applied mathematics, Wangingen U., the Netherlands) address the problem that when polymer is extruded at a fast enough rate to make a satisfactory profit, it is often distorted, a phenomenon called melt fracture. Their topics include pictures of polymer melt fracture through optical microscopes and scanning electron microscopes, polymer characteristics, polymer rheology, polymer processing, melt fracture experiments, variables, understanding melt fracture, modeling it, and preventing it.
blown-film; - profile extrusion; - melt fracture of polyolefines; - injection moulding of composites; - new simulation methods.
In this process, a polymer melt is extruded through a capillary and is subsequently stretched with a hot airstream until flow instabilities or melt fracture cause it to break up into particles.
Finally, Aspira One does not melt fracture at high extrusion rates, giving it high clarity on all EBM platforms.
This form of melt fracture is visually observable as a frosty white matte surface haze, and is undesirable for transparent bottle applications.