Polyolefin random copolymers

To support this hypothesis, the OBC sample can be fractionated by the TREF experiment. TREF fractionation of the OBC, followed by evaluation of the octene content by 13C NMR, reveals the data shown in Fig. 21. For a polymer blend, each molecule dissolves and elutes according to its comonomer content. The results invariably fall on the line in Fig. 21 labeled random copolymer line. The triangles reveal the comonomer content of the TREF fractions from an OBC. At any given temperature, the polymer eluting has much more comonomer than would be expected for a random distribution. The only explanation is that the comonomer is blocked, as expected from the chain shuttling mechanism. The extent of deviation can even be quantified, and a new method was recently invented to determine the block index for a given polyolefin [46],... 

After five decades of catalyst research there is slowly emerging a family of discrete late transition metal catalysts that are capable of generating high molecular weight, linear, random copolymers of ethylene and polar comonomers such as acrylates. Further advances in the efficiency of these catalysts will likely give rise to new families of commercial polyolefins with a wealth of new performance properties imparted by the polar groups attached to the polymer backbone. 

Single crystals with a Tm of 423 K have been produced from low-density polyethylene (ldpe). Isotactic PP crystals have a Tm of 444 K and syndiotactic PP has a Tm of 411 K, whereas atactic PP is amorphous and has a Ts of 255 K. Isotactic polyolefins with pendant groups, such as polyhexene, have high Tm values. Random copolymers of ethylene and propylene are amorphous, but block copolymers of these monomers are crystalline. 

Random ethylene copolymers with small amounts (4-10 wt-%) of 7-olefins, e.g. 1-butene, 1-hexene, 1-octene and 4-methyl- 1-pentene, are referred to as linear low-density polyethylene, which is a commercially relevant class of polyolefins. Such copolymers are prepared by essentially the same catalysts used for the synthesis of high-density polyethylene [241]. Small amounts of a-olefin units incorporated in an ethylene copolymer have the effect of producing side chains at points where the 7-olefin is inserted into the linear polyethylene backbone. Thus, the copolymerisation produces short alkyl branches, which disrupt the crystallinity of high-density polyethylene and lower the density of the polymer so that it simulates many of the properties of low-density polyethylene manufactured by high-pressure radical polymerisation of ethylene [448] (Figure 2.3). 

Ethylene-styrene pseudo-random copolymers (known as ethylene-styrene interpolymers) [14] have also been used to improve the compatibility between sPS and polyolefins, mainly polyethylene (entry 12). 

For Oleflex TPO (PP and PE with a-olefin random copolymer), reactive processing (cross-linking) is used to get a finely dispersed morphology of copolymer dispersed in the polyolefin matrix. Recommended processing conditions are similar to those for neat PP or PE. For calendering, the melt temperature should be in the range 165-175°C. 

A number of polyolefin blends are routinely calendered. TPO s consisting of blends of PP or PE with a-olefin random copolymer Oleflex ) are suitable. The copolymer is finely dispersed as a rubbery phase in the polyolefin matrix. The blend is processed at conditions similar to polyolefins. For calendering, typical melt temperature is 165-175°C. 

The blends of EPDM terpolymers and isotactic PP with curing agents, such as peroxide, phenol resins, and sulfur, are termed as thermoplastic vulcanized elastomer (TPV) since the rubber domains are vulcanized. Polyolefin copolymers, such as random copolymer of propylene with ethylene, copolymers of other olefins, elastomeric PP, and elastomeric PE, are developed with recent advances of... 

Practically, some of the above polyolefin copolymers have already been used to blend with PP in applications such as car bumpers and impact elastomeric goods. Although ethylene-propylene random copolymer has been the main component for such... 

The above polyolefin copolymers have also been used to prepare conventional composites and nanocomposites. However, similar to the case of polymer blends, not too many studies have been reported thus far. Recently, Kelarakis et al. (49) have mixed 10 wt% of surface-modified carbon nanofiber (MCNF) with propylene-ethylene random copolymer (propylene 84.3%). The MCNF acted as a nucleating agent for crystallization of the a-form of PP in the matrix. During deformation at room temperature, strain-induced crystallization took place, while the transformation from the 7-phase to a-phase also occurred for both unfilled and 10 wt% MCNF-filled samples. The tensile strength of the filled material was consistently higher than that of pure copolymer. These results are illustrated in Fig. 8.27. 

The living nature of the nickel-catalyzed a-olefin polymerizations coupled with the propensity for chain straightening of longer a-olefins can be utilized to prepare block copolymers with well-defined architectures. For example, the synthesis of a-olefin A—B—A block copolymers where the semicrystalline A blocks are made up of poly(l-octadecene) and the B block is composed of a more highly branched, amorphous, random copolymer of propylene and 1-octadecene enabled the preparation of thermoplastic elastomeric polyolefins. ... 

General Description Polybutene-1 (PB-1) is a polyolefin, or unsaturated polymer, that is expressed as C H2n- Basell Polyolefins series polybutene-1 resins are high-molecular-weight polyolefins manufactured from butene-1 monomer. Available as a homopolymer or a random copolymer.t Polybutene is a polymer of butylene and is also called polybutylene. 

Polypropylene, a homopolymer polyolefin engineering plastic provides excellent chemical resistance, purity and it is the lightest of all commercial plastics. PP offers innovative solutions to many challenges that face the automotive industry today. Its low density compared to traditional materials significantly contributes to fuel economy and reduced material costs. Its excellent noise, vibration, and harshness (NVH) properties contribute to enhanced passenger comfort. Thus, PP has become the most important thermoplastic material in automobile industry. PP homopolymers, random copolymers, and impact copolymers are used in products such as automotive parts and battery cases, carpeting, electrical insulation, and fabrics. 

The motivation behind the molecular design of Nodax class PHA copolymers closely follows that of the well-known industrial polyolefin linear low density polyethylene (LLDPE). LLDPE is a random copolymer of ethylene with a small amount of a-olefin units, such as 1-butene or 1-hexene, which will result in the formation of the polymer chain structure with mcl alkyl side group branches. In a similar manner, one can envision the possibility of creating a polymer structure of LLDPE with a PHA backbone having short alkyl side chains, as depicted in Fig. 2. 

In summary, the need for effective compatibilizers for the preparation of polyolefinZ layered silicate nanocomposites has led to the synthesis of various model fimctional polymers. Molecules with functional ammonium or hydroxyl groups as well as block or random copolymers among others have been tested for their ability to compatibilize the components. Phase-separated, intercalated, exfoliated, or even mixed structures have been observed depending on the kind, the molecular characteristics, and the degree of fimction-alization, as well as the concentration of the additive. In some cases, enhanced dispersion in comparison to the widely used maleated polyolefins has been reported. Nevertheless, despite the number and the quality of fhe reported studies, it is not clear yet which is the best compatibilizer for such sysfems. 

Polyolefin blends comprised 25-95 wt% of a crystalline random copolymer, EPRl (of propylene with ethylene and/or an alpha-olefin), and 5-75 wt% of a mixture consisting of PE and EPR2. The density of EPRl was about equal that of the mixture. The blends had good transparency and impact resistance even at low temperatures and were used to manufacture food containers, medical, packaging films, etc. 

Semicrystalline polyolefin blends were prepared by mixing two different random copolymers of propene with 4-lOC alpha-olefin at a ratio from 1 3-1 1. The first copolymer contained 1-10 wt% of C4 io alpha-olefin (1-butene, 1-pentene, 1-hexene, 1-octene, and 4-methyl-1-pentene), whereas the second 15 0 wt% of the same comonomer. The mixing was carried out in reactors, polymerizing the monomers in the presence of stereospecific catalysts supports on active magnesium dihalides, in at least two sequential stages. The resulting R-TPOs showed limited... 

Association Phenomena.—This section includes polymer-polymer and polymer-small molecule associations. In general, the first type leads to severe spectral broadening resulting in the loss of intensity from conventionally recorded high-resolution spectra. Thus in aqueous solutions of block copolymers of ethylene oxide with styrene and butadiene, no signals from the polyolefin are seen due to the formation of polyolefin-cored micelles. Intermolecular association has also been observed in styrene-ethylene dimethacrylate random copolymers in CCI4, and the... 

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