LLDPE melt, additives

A link between the relatively good processability of low density polyethylene (LDPE) and the excellent toughness of linear low density polyethylene (LLDPE) has been a key subject for many researchers. Fluoropolymer-based additives provide this link. Today, the use of fluoropolymer processing additives has expanded greatly, from an early way of minimizing melt defects, to improving the throughput rates and properties of LLDPE. These additives now provide benefits in a host of polyolefin extrusion applications. 

Hoang, E.M., Liauw, C.M., AUen, N.S., Fontan, E., and Lafuente, P, Effect of Metal Stearate Antacid on the Melt StahiUzation Performance of Phenolic/Phosphite Antioxidants in Metallocene LLDPE. Part 1 Melt Processing Stahility /. Vinyl Addit. Technol., 10, 3, 137 (2004)... 

High density (HDPE), 52 Irregularities, 52 Linear low density (LLDPE), 52 Low density (LDPE), 52 Molecular weight, 52 Melt flow index, 53 Melting temperature, 51 Moisture absorption, 51 Polymeric forms, 52 Resistance to chemicals, 52 Resistance to oxidation, 52 Shrinkage, 54 Unsaturations, 54 a-transition, 51 P-transition, 51 y-transition, 51 Polyisocyanate, 79 Polylactic acid, 79, 91 Polymer alloys, 48 Polymer processing additives, 646 Polymer rheology, 619 Polymeric forms, 52 Polyphase PlOO, 451 polypropylene (PP), 2, 11 Polypropylene homopolymer, 70... 

Polyolefin blends always show a raised swell of the extrudate jet in comparison with homopolymers (83). This was shown earlier (88) for LDPE/LLDPE blends. Some researchers reported (89,90) a significant influence of the molecular structure on properties of the polymer melts the polymers whose chains contain starlike branches show increased sensitivity toward shear stresses applied onto their melts. The presence of comblike segments increases the melt strength. For example, the addition to LLDPE up to 10 wt% of a comblike polymer (copolymer of a polyethylene macromonomer, k. 8000gmol , and ethylene and hexene) allows raising the strength of polymer melt almost by one decimal order (86). The MFl of the blend varies less substantially. The melt strength of LLDPE blends can be... 

Exxon LL5202.09 LLDPE, a barefoot 12 melt index, 0.924 density polyethylene was used as the carrier resin for preparation of all concentrate formulations. Exxon LL1001.09 LLDPE, a barefoot 1.0 melt index, 0.918 density film resin was selected as the matrix material for the preparation of all letdown compounds. Additive-lree resins were used throughout this trial to minimize potential interactions with additive packages and to simplify the analysis task. 

LLDPE has become a key PO for blown film, but not without some difficulties in establishing methods for maintaining bubble stability and gauge consistency. Typically, LDPE is blended with the LLDPE to inaease melt strength and bubble stability, but this can reduce tensile tear, and dart-impact strengths. Alternatively, process developers have turned their attention to a melt-strength additive (MSA) developed by DuPont Canada in the 1980s particularly for when bubble stability is a problem. 

Anderson et al. [16] had performed melt blending on PLA/LLDPE in an effort to toughen PLA. The results indicated that, for the amorphous PLA, the toughening effect was achieved only when a polylactic acid-b-polyethylene (PLA-PE) block compolymer was used as a compatibilizer. They have reported that impact strength of 80/20 wt% PLA/LLDPE blend reach 35 15 kJm compare to the homopolymer (12 4 kJm ). They also showed that addition of 5 wt% of... 

When studying UHMWPE blended with low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE), it was found, using analysis of the log-additive rule, Cole-Cole plots, Han curves, and Van Gurp s plot, that the LDPE/UHMWPE blends were miscible in the melt [8]. However, the thermal properties and morphology of the blends were not consistent with the rheological properties. The latter showed liquid-solid phase separation as a result of the different rates of crystallization of LDPE and UHMWPE. However, the rheological properties and electron microscopy images of LLDPE/UHMWPE blends showed... 

In blends, fluoropolymers are used in small quantities to enhance throughput, reduce the frictional properties, and increase the wear resistance. Blends comprising 0.3-50 wt% of a low molecular weight PTFE (T , < 350 °C) with engineering resin showed improved antifriction properties (Asai et al. 1991). LLDPE generally exhibits sharkskin melt fracture, but the use of fluoropolymer additives, such as the copolymer of vinyUdene fluoride and hexafluoropropylene, can help to eliminate the extrusion instability (Hatzikiriakos and Migler 2005). 

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