VLDPE ULDPE

Some late-transition metal catalysts, such as the Ni-diimine catalyst shown in Figure 2.14(d), have an intriguing property called chain walking when polymerizing ethylene, the active center can move away from the chain end and walk on the polymer backbone, leading to the formation of SCBs in the absence of a-olefin comonomers. By varying the polymerization temperature and monomer pressure, it is possible to make polymers with densities varying from those of FfDPE to LLDPE, VLDPE, ULDPE, and, in fact, to that of a complete amorphous, ethylene-propylene like elastomer [26,27],... 

Figure 18,2 d) illustrates the general structure of very low density polyethylene, which we also call ultra low density polyethylene. In common with linear low density polyethylene, these resins are copolymers of ethylene and 1-alkenes. The comonomer level ranges from approximately 8 to 14 mole %. We normally refer to these polymers as VLDPE or ULDPE. The molecules of very low density polyethylene contain a distribution of lengths and branch placements. 

PS PSF PSU PTFE PU PUR PVA PVAL PVB PVC PVCA PVDA PVDC PVDF PVF PVOH SAN SB SBC SBR SMA SMC TA TDI TEFE TPA UF ULDPE UP UR VLDPE ZNC Polystyrene Polysulfone (also PSU) Polysulfone (also PSF) Polytetrafluoroethylene Polyurethane Polyurethane Poly(vinyl acetate) Poly(vinyl alcohol) poly(vinyl butyrate) Poly(vinyl chloride) Poly(vinyl chloride-acetate) Poly(vinylidene acetate) Poly(vinylidene chloride) Poly(vinylidene fluoride) Poly(vinyl fluoride) Poly(vinyl alcohol) Styrene-acrylonitrile copolymer Styrene-butadiene copolymer Styrene block copolymer Styrene butadiene rubber Styrene-maleic anhydride (also SMC) Styrene-maleic anhydride (also SMA) Terephthalic acid (also TPA) Toluene diisocyanate Ethylene-tetrafluoroethylene copolymer Terephthalic acid (also TA) Urea formaldehyde Ultralow-density polyethylene Unsaturated polyester resin Urethane Very low-density polyethylene Ziegler-Natta catalyst... 

Very Low Density (VLDPE) and Ultra Low Density (ULDPE) Polyethylenes. These are made by copolymerization with increasing amounts of comonomers, especially 1 -octene, reducing regularity/crystallinity (density 0.91- 0.86) down toward ethylene/propylene rubber. These are soft and flexible enough to compete with plasticized polyvinyl chloride and thermoplastic elastomers in some applications. 

Linear low-density PE (LLDPE) has a density similar to LDPE, but the linearity of HDPE. Branches of LLDPE are comparatively short. None of WPC manufacturers has reported that they make composite deck boards based on LLDPE, as well as on VLDPE (very low-density PE) and ULDPE (nltra low-density PE). The two latter polyethylenes have extremely high flexibility, which wonld make them inappropriate for composite deck boards or railing systems. 

Polyethylenes with larger amounts of comonomer and consequently density below the normal LLDPE range are called very low density polyethylene, VLDPE, or ultra low density polyethylene, ULDPE. While these can be produced using Ziegler-Natta catalysts, often they are made using metallocene catalysts, as described next. 

General Description Ultra low density polyethyl-enes (ULDPEs) and very low density polyethylenes (VLDPEs) are essentially synonymous designations for linear polyethylenes with densities down to 0.880 g/cu in. ULDPEs are finding applications as impact modifiers for other polyolefins. Dow Chemicals Attane ULDPE is an Ethylene/Octene copoly-... 

Synonyms Polyethylene, linear low-density, high a-olefin content ULDPE VLDPE... 

VLDPE or ULDPE, very-low or ultra-low-density polyethylene... 

Two distinct regions can be easily identified in Figure 2.3 a sharp high-crystallinity peak (low a-olefin fraction) and a broad low-crystallinity peak (high a-olefin fraction). These two regions are associated with at least two types of active sites, one with a much lower reactivity ratio toward incorporation of a-olefin than the other. As the relative fractions of polymer under these two modes is varied, we go from HDPE - with a unimodal, high-crystallinity peak and sometimes a small, lower crystalHnity tail - to LLDPE, VLDPE and ULDPE resins, having a very pronounced lower crystallinity peak, which may, sometimes, show additional peaks. 

Linear low-density polyethylene (LLDPE) is a variation of HDPE. It is synthesized similarly, but LLDPE has a much higher content of comonomer, such as hexene or octene. Incorporation of comonomer in the chain yields short chain branches of a specified length (Fig. 1.5). By controlling the amount of branch points through comonomer content, degree of crystallinity - hence density - can be controlled. Variants of LLDPE are known as very low-density polyethylene (VLDPE) and ultra low-density polyethylene (ULDPE). LLDPE density is generally in the range of 0.88 to 0.93 g/cm. ... 

PA-6/VLDPE-g-MA TSE/SEM/optical microscopy/mechanical properties/DSC/DMTA/comparison to commercial (PA-6/ULDPE) blend/also used VLDPE-g-DEM Lazzeri et al. 1999 (see also Gadekar et al. 1998)... 

VLDPE, and ultralow-density polyethylene, ULDPE, as copolymers of C2 with a-olefin (C4 g) having high SCBD, p = 0.860-0.915 g mL and 7)n = 60-90 °C. UCC used the 2nd-generation Z-N... 

These linear elastomers are produced by coordination polymerization using a Phillips or Z-N catalyst at low P and T. Here belongs Mxsten XLDPE from Eastman Chem. and Attane ULDPE from Dow. The first metallocene-catalyzed VLDPE was a hexene copolymer with p = 0.912 g mL made in the UNIPOL gas-phase process with Z-N catalyst and introduced by ExxonMobil as Exceed metallocene VLDPE. The resin has outstanding sealing properties (hot tack and seal strength) compared with ZN-VLDPE. The solution polymerization in a hydrocarbon usually is carried out in a continuously stirred tank reactor (CSTR), at r = 160-300 °C and P = 2.5-10 MPa with the residence time of 1-5 min [Dow in 1992 and UCC in... 

Metallocene plastomers are plastomers made using metallocene single-site catalysts. Other polyolefins exist in this composition range made with conventional catalysts Dow ATTANE (10), Union Carbide FLEXOMER (11), and Mitsui TAFMER products (12). These are generally called very-low-density poly-ethylenes (VLDPEs) and ultra-low-density polyethylenes (ULDPEs), and are not discussed in this chapter. 

ULDPE and VLDPE resins find application in low temperature applications, such as ice bags, where lower density offers greater toughness. They are also used as sealing layers, replacing low density copolymers such as vinyl acetate, and as blend components to improve toughness. 

Metallocene polyethylene (mPE) plastomers 0.900-0.915 Coextrusion, heat seal layers Ethylene-vinyl acetate (EVA) resins with 9% vinyl acetate, ultra low density polyethylene (ULDPE), very low density polyethylene (VLDPE)... 

PE is classified into three groups low density PE (LDPE), high density PE (HDPE), and linear low density PE (LLDPE). The main difference between these PEs is their stiffness as shown in Fig. 9. Recently, very low density PE (VLDPE) and ultra low density PE (ULDPE) have joined the LLDPE family. So the PE family seems to cover a wide stiffness range from HDPE to elastomer. Here, we describe PE in general, and LLDPE and elastomer in further detail. 

In the case of Ziegler-Natta catalysts (MSC), the studies to control molecular structure such as Mw, MWD, and composition distribution (CD) have been extensively carried out because this molecular control was necessary to develop VLDPE and ULDPE. To produce the narrow CD LLDPE, a great deal of effort went into research to improve the traditional Ziegler-Natta catalyst (MSC), but this technology still has its limit. 

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