Characteristics of Polyolefin Blends

Chapter 2 Miscibility and Characteristics of Polyolefin Blends 35 Table 2.3 Surface Tension (y) of Polymers at Different Temperature in dyncm. ... 

The FR characteristics of PCP and Anorin-38 were improved substantially by introducing bromine. When five bronine atoms were introduced by controlled bromi-nation, the resin (the product obtained was still fluid in nature and could be crosslinked by hexamine to get hard partially brominated PCP-PBPCP) showed excellent FR characteristics exhibiting self-extinguishing property and UL 94 V-0 grade when blended with polyethylene, NR, etc. There was excellent compatibility with polyolefins as well as with other polymers such as cellulose, polyurethane, etc. Table 13 shows the FR properties of NR-PBPCP. 

Blends of polyolefins (e.g., HPDE/LDPE, LDPE/ ethylene copolymers, PP/EPDM, PP/HDPE/EPDM, HDPE/butyl rubber) have been commercial since the late 1960 s and early 1970 s. Specific film formulations were commonly based on polyolefin blends to achieve the proper balance of processing, environmental stress crack resistance, modulus, toughness, cling, transparency, filler acceptance, printability, tear resistance, shrinkage characteristics, and permeability. Ethylene-propylene mbber (EPR, EPDM) was commonly incorporated into polypropylene as an impact modifier at moderate levels and as a flexibilizer at high levels. One of... 

It is our purpose here to summarize the characteristics of blends of polyolefins. We consider both blends of polyolefins with other polyolefins and with nonpolyolefins including polyamides and polystyrenes. In the case of interpolyolefin blends, our primary concern is with miscibility. In the case of blends of polyolefins with nonpolyolefins, the blends are all inuniscible and our concern is with phase morphology. We also consider three component blend systems where the third component is a surfactant or compatibilizing agent, which collects at the interface. 

It is quite important to comprehend that the miscibility and/or compatibility in polyolefin blends dominate their material characteristics and basic properties. The lack of polarity, however, often leads to the phase-separated state in most polyolefin blends in spite of the similar chemical structure. For example, it is well known that... 

The distinct fracture lines characteristic of brittle resins was observed on the fracture surface of control (59). In the blend, the bulk of the sample exhibited features similar to those observed for the control and no dispersed particles were found in the bulk of the sample as the polyolefin phase migrated to the top of the sample. The fracture surface of (20 and 30 phr) AC 5120-RVP blends was different from that of unmodified AC 5120 blends with epoxy resin. Although some of the polyethylene migrated to the surface, dispersed polyethylene was seen on the fracmre surfaces (Fig. 21.10). 

Solubility tests permit at least a tentative identification of the components also in polymer blends. Blends of ABS and polycarbonate are soluble in most polar solvents. Solubility in tetrahydrofuran and methyl ethyl ketone demonstrates the absence of polyolefins in such blends and the presence of aromatic polyesters or of polyamides can also be excluded. On the other hand, generally they may contain such highly soluble polymers as polystyrene, PVC, ABS, or polymethacrylates. However, blends that contain polybutylene terephthalate or polyethylene terephthalate do not dissolve in the usual solvents, but require m-cresol, which can he a clear indication that aromatic polyesters are present. Polyolefins dissolve at high temperatures, at least 110 °C, in toluene and p-xylene, and this behavior is characteristic of blends that contain polyethylene or polypropylene. 

Prepared filaments and fibres are applied not only in the floor coverings as the most important utilization for PP, but also medical, hygienic, apparel, automotive and/or agricultural sectors became crucial, for applications such as disposable diapers, sports underwear and equipment, artificial grass, geo textiles, ropes, car seats, oil wipes, wet and dry filters or membranes. Physical and chemical properties of polyolefins fibres are developed for many applications, in order to increase comfort characteristics, tensile strength, and/or other utility properties they are often blended, co-processed or combined with other materials such as polar acrylics, wool, bonding agents, hydrophilic fillers, or stabilizers. 

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