LDPE-LLDPE blends

Rate [7-18] and temperature [ 16-26] effects on the EWF parameters have been investigated by many authors on several different polymeric materials, like PET [7,18,22,24], PBT [12,21,2.5] PBT/PC blend [8], PEN [11, 26], amorphous copolyester [9], iPP [10,23], sPP [15], UHMWPE 113], LDPE, LLDPE and LDPE/LLDPE blends [19], ABS [13], POM [14] uPVC [16], and PC [17. 20]. The results are not indicating a clear and general trend showing that rate and temperature effects on the fracture parameters strictly depend on the material under investigation. 

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... 

Industrial sacks, FFS application LDPE-LLDPE blends... 

Metallocene linear low density polyethylene (mLLDPE) 0.916-0.925 Stretch films, industrial sacks, shopping bags, form/fill/seal applications, frozen food packaging Butene coppolymer C4 LLDPE, LDPE-LLDPE blends, EVA, ULDPE, ionomer layers... 

High performance, high clarity LLDPE 0.909-0.912 Liner stretch film, lamination, highly transparent food packaging Higher a-alkene octene C8 LLDPE, LDPE-LLDPE blends... 

Figure 6.11 Yield stress vs. composition for LDPE-LLDPE blends. (Specimens did not reach yield in the flow direction)...

PE PET PE-g-maleate PE = LDPE/LLDPE blend maleate = diatkyl maleate transesterification catalyst added to improve grafting 131... 

Toronto, 27th April-2nd May 1997, p.2310-4. 012 QUANTITATIVE ANALYSIS OF LDPE/LLDPE BLEND USING DSC AND FTIR METHODS... 

Polyethylene, as LDPE, LLDPE or a mixture or blend involving combinations of LDPE, MDPE, HDPE, EVA, etc., finds a wide usage in bags, sacks, sachets, overwraps, shrink wraps, stretch wraps, etc. Most deep freeze packs, for example, use LDPE or an LDPE mixture which is produced from a reel on a form fill seal type machine. However, as many of these packs are up to 100% printed, even ink of 2-5 Pm could be considered as a separate layer which modifies some of the physical and chemical properties. As all polyolefins need a surface (oxidative) treatment to ensure a good print key, this or any other surface treatment process may further modify the film properties. 

It should be mentioned that several homopolymers (of which polyethylene is probably the best known sample) also exhibit a complex melting behavior. Branched polyethylene s (LDPE, LLDPE and VLDPE) show multiple melting endotherms, due to the presence of fractions with different branching content [Schouterden et al, 1985 Defoor et al, 1993]. This was clearly illustrated by Defoor et al. who fractionated LLDPE with respect to the short-chain branching content and blended the fractions with the highest and the lowest branching content. It was shown that they both crystallized and melted separately. Both fractions determined the sphemlitic morphology in a co-operative way. 

The granular starch has been compounded with several synthetic polymers, viz. LDPE, LLDPE, PE-blends, PP, PS, etc. Dried granules were compounded in a TSE into a master batch, that the customer dilutes to 5-10% for film blowing or to 20 wt% for injection- and blow-molding. Owing to starch sensitivity to temperature, processing should not exceed 230°C [Griffin, 1977, 1983]. 

Figure 3.9 Tensile stress-strain curves for LLDPE, LDPE, and LDPE-EP blends.

These PE polymers offer a broad spectrum of structures, properties, and applications. However, the blending of different types of PEs (HDPE, LDPE, LLDPE, and UHMWPE) has attracted growing interest because of the potential for obtaining low cost materials with improved mechanical properties and better processabilities, as compared to those of the pure constituents (1-34). Nowadays, 70% of PEs in the market are blends (24). The processability and properties of PE blends are dependent on the melt miscibility. Moreover, the properties are also dependent on the morphological structure of the blend, which is basically a combination of the crystallization behavior and melt miscibility. Therefore, the miscibility and crystallization behavior of PE blends have been prevalent research topics over the last two decades. 

In Reference 107, the effect of grafting of a polar group (MAH) onto LDPE chains and the chemical modification of clay particles with 2,6-diaminocaproic acid (L-lysine monohydrochloride) to produce nanocomposites with a matrix composed of a ternary blend of PEs (LDPE, LLDPE, and HDPE) was studied in detail. X-ray diffraction was used to determine the exfoliation degree of the clay. Morphological features were revealed by scanning electron microscopy and thermal analysis disclosed the thermal stability of the samples. Comparative analyses of the mechanical (under tension) and rheological properties of the nanocomposites were carried out as well. 

Figure 4.12 DSC of LDPE, LLDPE, and a blend of LDPE and LLDPE...

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. 

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... 

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