Melt-extrusion

When melt blending process or extrusion processes are applied, the optical brighteners should have a stability up to temperatures as high as 310-330 C (20). In poly(ester)s, such as poly(ethylene tere-phthalate) (PET) the tendency of formation of acetaldehyde can be reduced by blending with a low molecular weight poly (amide) (PA). 

This is desirably for the application of PET as drinking bottles. However, the addition of PA causes yellowing of the products. Therefore, optical brighteners are added to compensate for this drawback (20). 

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Melt Extrusion. By far the most important method for producing film and sheeting materials reties on one or another of the various melt extmsion techniques (5). The main variations of melt extmsion are the slot (or flat) die-cast film process, the blown films process, and the flat die sheeting-stack process. These may be combined with one or more steps such as coextmsion wherein multilayer film or sheet is formed, biaxial orientation, and in-line coating (6). 

Teflon FEP—Fluorocarbon Resin—Techniques for Processing bj Melt Extrusion, 2nd ed., information bulletin X-82, E. I. du Pont de Nemours Co., Inc., Wilmington, Del., 1960. 

Recently, Tsakala et al. (90) formulated pyrimethamine systems based on several lactide/glycolide polymers. These studies were conducted with both microspheres (solvent evaporation process) and implants (melt extrusion process). In vitro studies indicated that pyrimethamine-loaded implants exhibited apparent zero-order release kinetics in aqueous buffer whereas the microspheres showed an initial high burst and considerably more rapid drug release. In vivo studies in berghi infected mice confirmed that the microspheres did not have adequate duration of release for practical application. However, the implants offer promise for future clinical work as more than 3 months protection was observed in animals. 

Malinconico M, Immirzi B, Massenti S, La Mantia FP, Mormile P, Petti L (2002) Blends of poly-vinylalcohol and functionalized polycaprolactone. A study on the melt extrusion and post-cure of films suitable for protected cultivation. J Mat Sci 37 4973 1978 Mallek SB, Prather TS, Stapleton JJ (2007) Interaction effects of Allium spp. residues, concentrations and soil temperature on seed germination of four weedy plant species. Appl Soil Ecol 37 233-239. doi 10.1016/j.apsoil.2007.07.003... 

The thermal requirements for pigments which are targeted for PETP melt extrusion are particularly severe. However, it is important to consider the individual conditions at the various stages of polymer coloration. Pigments, for instance, which are added during the so-called condensation process in a glycol dispersion prior to transesterification or condensation in the autoclave, are exposed to temperatures between 240 and 290°C for 5 to 6 hours [43]. These harsh conditions are only tolerated by very few polycyclic pigments, primarily by representatives of the quinacridone, copper phthalocyanine, naphthalenetetracarboxylic acid, and pery-lene tetracarboxylic acid series. 

P.D. Coates, S.E. Barnes, M.G. Sibley, E.C. Brown, H.G.M. Edwards and I.J. Scowen, In-process vibrational spectroscopy and ultrasound measurements in polymer melt extrusion. Polymer, 44, 5937-5949 (2003). 

HME hot melt extrusion ETCO long-term cost of ownership... 

Heat stabilizers are added to materials to impart protection against heat-induced decomposition. Such stabilizers are needed to protect a material when it is subjected to a thermal-intense process (such as melt extrusion) or when the material is employed under conditions where increased heat stability is needed. 

Liu H, Pan L, Lin Q, Xu N, Lu L, Pang S, Fu S (2010) Preparation and characterization of poly (propylene carbonate)/polystyrene composite films by melt-extrusion method, e-polymers 2010 38, http //www.e-polymers.org/joumal/papers/qlin 270310.pdf. Accessed 01 April 2011... 

In the past, electron beam radiation was applied to produce PSA exclusively however, recent improvements in UV curing technology (precise UV dose control, suitable photoinitiators) permit UV to be used to produce pressure-sensitive adhesives. PSA formulations can vary in consistency from low-viscosity liquids up to solids melting at 80°C (176°F). Therefore, applications may vary from screen printing to roll coating to melt extrusion. Coat weights for most PSA materials vary from 1 to 10 g/m. ... 

Peroxides decompose to form free radicals, which in turn attack the polymer chain to form crosslinking sites, which then react to form crosslinks. Irradiation of PE also results in a crosslinked product by substantially the same mechanism except that the free radicals are generated by decomposition of the polymer itself. By either method, however, a product is obtained which is intractable and can not be further fabricated by techniques normally used in the fabrication of PE, such as melt extrusion or injection molding. 

Schreiber.H. P., Rudin, A., Bagley.E.B. Separation of elastic and viscous effects in polymer melt extrusion. J. Appl. Polymer Sci. 9,887-892 (1965). 

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