Melt Extrusion Stability

Since most stabilizers react in more than one way and combinations of additives are required to prepare stabilized polypropylene fiber, these materials are better discussed in accord with the function they perform for polypropylene rather than the mechanism by which they function. When making fibers, stabilizers are added to polypropylene to (1) provide melt extrusion stability (2) provide long-term thermal stability at normal use temperatures and (3) provide stability to exposure to UV light (sunlight). The degree to which these stabilizers effectively accomplish their objectives without introducing other objectionable effects, such as yellowing, determines the value of the resultant fiber product. 

Number of extruder passes at 270°C melt flow index  

There are numerous formulations of antioxidants and processing stabilizers in the literature. Table 3.11 [116-118] and Table 3.12 present a few examples of historical and current 

Hindered phenolic compounds containing a r-butyl phenol moiety 

Peroxide-free hindered hydroxylamine ester Phenol-free compounds 

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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. 

Extrusion Stability (20). Processing stabilities were also determined by six succesive extrusions of the resins through a 1-inch extruder and measuring the change in melt flow (ASTM D 1238-65T, Condition L) after each extrusion. The data shown in Figure 7 indicate that Resins C, E, and I are least stable and G, A, and D are the most stable. 

Kissi NE and Piau J-M, "Stability Phenomena During Polymer Melt Extrusion" in Piau J-M and Agassant J-F (Eds), "Rheology for Polymer Melt Processing", Rheology Series, Vol. 5, Elsevier, Amsterdam, 1996, pp 389-420. Langelaan HC and Gotsis AD, J Rheol 40 (1996) 107. 

Standard test methods to analyze the thermal stability of polymers cover multiple extrusions and accelerated heataging. Multiple extrusions evaluate the melt-processing stability of a polymer or polymer formulation and determine... 

Proddurituri, S. Urman, K.L. Otaigbe, J.U. Rekpa, M.A. Stabilization of hot-melt extrusion formulations containing solid solutions using polymer blends. AAPS PharmSciTech 2007, 8 (2), El-ElO. 

Easily processed by melt extrusion No API plasticization required Ma-e hydrophobic than vinylpyrrolidone Processed around 130°C Newest excipient for melt extruded dispersions Easily process by melt extrusion Low Tg can limit stability Not of compendial status Stable up to >180°C Not easily extruded without plasticizer Degradation onset is 155°C Ionic polymer soluble above pH 5.5 Easily extruded without plastidzer Process temperatures >140°C Ionic polymer soluble above pH 5.5 depending on grade... 

Crowley, M.M. Zhang, F. Koleng, J.J. McGinity, J.W. Stability of polyethylene oxide in matrix tablets prepared by hot-melt extrusion. Biomaterials 2002, 25(21), 4241 248. 

Ghalanbor, Z. Korber, M. Bodmeier, R. Improved lysozyme stability and release properties of poly(lactide-co-glycolide) implants prepared by hot-melt extrusion. Pharm. Res. 2010, 27(2), 371-379. 

Melt-processing stabilization of AOs. Unstabilized HOPE shows large changes in melt-flow index with each extrusion pass. However, phenolic/phosphite AO blends without and with a lactone AO component (Ciba Irganox B 215 and HP 2215) reportedly keep the melt flow more consistent after repeated extmsion passes. 

Degradation of poly(ethylene terephthalate)/clay nanocomposites during melt extrusion Effect of clay catalysis and chain extension. Polymer Degradation and Stability. Vol.94, pp.113-123. 

Recently, Liu et al. [34] prepared banana fibre (BaF)-filled composites based on high-density polyethylene (HDPE)/polyaminde-6 (PA 6) blends via a two-step extrusion method. Maleic anhydride grafted styrene/ethylene-butylene/styrene triblock polymer (SEBS-g-MA) and maleic anhydride grafted polyethylene (PE-g-MA) were used to enhance impact performance and interfacial bonding between BaF and the resins. Mechanical, crystaUization/melting, thermal stability, water absorption and... 

For the case of extrusion ABS, when there is any change of throughput in the continuous process, such as sheet extrusion, profile extrusion, etc., inferior conditions such as surface inferiority or thickness deviation can be created. Therefore, the extrusion stability (less deviation of melt flow depending on temperature, less additives) is regarded as the major important characteristic, as shown in Table 6.7. 

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