Ethylene/1-butene copolymers HDPE

After 1958, many other new applications were found to take advantage of the properties offered by HDPE made with chromium-containing catalysts. In 1958, ethylene-butene copolymers were introduced [18] and other polymer grades were also soon developed. 

V aisman et al. [52] reported the effect of bromination of the surface of commercial UHMWPE fibres in order to polarise the surface of the fibres. This bromination process was shown to result in an increase in the degree of order of the transcrystalline zone when these fibres were combined with HDPE to produce a self-reinforced polymer model composite. While these pubUcations report the use of different types of PE to create self-reinforced polymer composites, UHMWPE fibres have also been combined with ethylene-based copolymers. Kazanci et al. [53, 54] reported the creation of commercial UHMWPE fibre-reinforced ethylene-butene copolymers. Filament wormd structiues were produced, with fibre volume fractions of 65%, with the suggestirm of a potential application for these materials in unspecified medical devices. 

LLDPE ethylene butene-1 copolymer, 18 branches/1,000 C Valid as well for slowly as rapidly (quenched) cooled blends DHDPE deuterated HDPE... 

LLFPE, LDPE, HDPE—linear low density, low density, and (respectively) high density poly(ethylene) PP—poly(propylene) PB-1—poly-(butene-1) PIB—poly(isobutylene) P4MP—poly(4-methylpentene-l) EP—ethylene-propylene copolymers EVA—ethylene-vinylacetate copolymers. 

A pressure transducer in combination with the size exclusion chromatography-FTIR technique was used to characterise semi-crystalline materials such as HDPE and random PP copolymers. The comonomer content (butene for HDPE and ethylene for PP) decreased with increasing molar mass. For two HDPE samples produced by the dual reactor process, this decrease occurred stepwise with a constant comonomer amount on either side of the step. For all the HDPE samples, the amount of end unsaturations decreased with molar mass. The concentration of side and trans unsaturations was too low to be determined. 8 refs. 

In order to improve the physical properties of HDPE and LDPE, copolymers of ethylene and small amounts of other monomers such as higher olefins, ethyl acrylate, maleic anhydride, vinyl acetate, or acryUc acid are added to the polyethylene. Eor example, linear low density polyethylene (LLDPE), although linear, has a significant number of branches introduced by using comonomers such as 1-butene or 1-octene. The linearity provides strength, whereas branching provides toughness. 

Ziegler-Natta catalysts were also designed to synthesize polyethylene (HDPE) and copolymers of ethylene with longer chain a-olefins (n-butene,... 

LLDPE can be produced with less than 300 psi and at about 100°C. It is actually a copolymer of ethylene with about 8% 10% of an alpha-olefin such as 1-butene, 1-pentene, 1-hexene, or 1-octene. Through control of the nature and amount of alpha-olefin, we are able to produce materials with densities and properties between those of LDPE and HDPE. LLDPE does not contain the long branches found in LDPE. 

It was noted also that satisfactory compatibilization could be achieved by local miscibility (given by solubility parameters) rather than direct matching of the chemical and macro-molecular composition. This may require the copolymer to have several components, such as poly(styrene-co-ethylene)-b-poly(butene-co-styrene) (SEES), which has been found useful in compatibilization of HDPE and PET (Bonner and Hope, 1993). 

LLDPEs are usually referred to as comonomers and copolymers, where mixtures of higher olefins, butene, hexene, octene, etc. are used. Mixtures of LDPE, MDPE, HDPE, and ethylene vinyl acetate, etc. are fighting the introduction of LLDPE. LLDPE can be produced in grades which have good clarity. 

HOPE, LDPE, and LLDPE are the three main types of commercial polyethylenes with a combined global consumption of >80 Mt/year. HDPE is a strictly linear homopolymer while LDPE is a long-branched homopolymer because of the different methods of polymerization. LLDPE, on the other hand, is a linear ethylene copolymer with small amounts of a-olefin comonomers such as butene, hexene, or octene. Traditionally, polyethylenes are classified according to the densities. The density of polyethylene decreases as the branching and/or comonomer content increases. The crystallinity and the properties associated with crystallinity, such as stiffness, strength, and chemical resistance, progressively decrease from HDPE to LDPE/LLDPE to POE grades. 

Polyethylene (PE) is the most widely used plastic throughout the world, and high density PE (HDPE) is the most widely used type of PE. HDPE has generally been taken to mean the product of ethylene polymerization having density greater than about 0.935 (or 0.94). It includes ethylene homopolymers and also copolymers of ethylene and alpha-olefins such as 1-butene, 1-hexene, 1-octene, or 4-methyl-1-pentene. Other types of PE include low density PE (LDPE), made through a free-radical process, and linear low density PE (LLDPE). 

LDPE Copolymers. A variety of comonomers can be added to the polymerization of ethylene to make copolymers. The free-radical polymerization mechanism of LDPE production allows for the copolymerization of polar comonomers. At this time, the incorporation of polar comonomers is unique to LDPE. The transition metals used to catalyze HDPE and LLDPE production are generally poisoned by polar comonomers and therefore, only copolymers containing alpha-olefins like 1-butene, 1-hexene, and 1-octene can be made. Because the polar copolymers can be made only by the LDPE process, they command a premium in the market. The most common comonomers (and their corresponding copol5uners) are vinyl acetate (EVA), methyl acrylate (EMA), ethyl acrylate (EEA), and acrylic acid... 

The first plant operated in the solution mode for the first four years of operation at a production rate of approximately 9,000 lbs PE/hr. During the first two years of operation, the plant produced only ethylene homopolymers with a Melt Index value of less than one. As outlined by Hogan [22] in 1958, ethylene/1-butene HDPE copolymers were introduced in order to increase the characteristics of the product mix available. Soon after the... 

Figure 12 shows the results for the modeling of the solubility of the copolymer poly(ethylene-co-l-butene) in propane. The pure-component parameters for poly (ethylene) (HOPE), poly(l-butene), and propane as well as the binary parameters for HDPE/propane and poly(l-butene)/propane were used as determined for the homopolymer systems. 

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