Copolymers polyolefin

As discussed earlier, ethylene propylene rubber (EPR or EPM) has been blended with PP and PE to improve the impact strength and to render the materials softer. Recently, metallocene catalysts or postmetallocene catalysts provide new pathways to generate elastic copolymers that can replace EPR. These pathways possess cheaper manufacturing cost and generate new materials with better compatibility to PP or PE. Such new materials included ethylene-propylene random copolymers with dominant ethylene component (33-34) or propylene-dominant component (35 1), propylene-ethylene block copolymer (42), ethylene-octene copolymer (43), poly(propylene-co-ethylene) (44), ethylene-hexene copolymer (45), ethylene-butene copolymer (46), low isotactic PP (47), and stereoblock PP (48). These materials are generally compatible with PP or PE, thus can be used to tailor the toughness (or the softness) of 

The results from the in situ X-ray study of propylene-based ethylene-propylene copolymer during tensile deformation (36) are described as follows, because the deduced molecular mechanism appears to be universal in all elastomeric polyolefin copolymers. The stress-strain curves and selected WAXD patterns during extension up to strain 5.0 and subsequent retraction back to strain 1.7 (i.e., at zero stress) in the first deformation cycle are shown in Fig. 8.22. 

The total crystal fraction, oriented crystal fraction (/oc). and unoriented crystal fraction (/uc) during extension and retraction have been analyzed. Results can be described as follows. At strain zero, the total crystal fraction was the same as the unoriented crystal fraction, which was about 14%, and both values decreased with strain. This indicates that a fraction of the original crystals was destroyed at the initial deformation stages. (This phenomenon was also reported in ethylene-based ethylene-propylene copolymer (34).) At strain 0.7, the total crystal fraction decreased about 4% (from 14% to 10%) at strains above 0.7, both total crystal fraction and oriented crystal fraction increased with strain, indicating the occurrence of strain-induced crystallization, whereas the unoriented crystal fraction decreased continuously with strain. The increase of the total crystal fraction was slower than that of the oriented crystal fraction, suggesting that some unoriented crystals were reoriented by 

To investigate the change of lamellar structure in TPE during deformation, in situ SAXS experiments were also carried out. During the extension and retraction processes in the first cycle, the stress-strain relationship and selected SAXS patterns are shown in Fig. 8.23. 

The relationship between the long period L of the dominant lamellar population and the applied strain during extension and retraction in the first cycle is shown in Fig. 8.24. 

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The coating is applied to protect the steel from corrosion due to the acid or alkaline condition of the soil surrounding the pipe in service. Usually, the process requires three layers. First, an epoxy powder is applied to achieve adhesion to the pretreated metal and therefore resistance to cathodic disbondment. Second, a tie layer of polyolefin copolymer is applied and third a thick layer of polyethylene is cascaded, which in effect protects the epoxy from physical damage. 

Polyolefin copolymers Although there is a wide variety of these available, the only one currently commercially available as a compounded powder is saponified EVA. This is reported to have good weatherability and will not suffer from ESC. One major advantage this coating has is that it can be applied by the fluidised bed process at low temperatures and this offers the possibility of coating temperature-sensitive metals such as galvanised steel. 

Property Polyethylene Polyolefin copolymer Polyolefin PPA 65 alloys P.V.C. Nylon P.V.D.F. 

Tobolosky suggestion of crystalline and amorphous polyolefin copolymers Commercial PU elastic fiber, DuPont Commercial PU TPEs lonomeric TPE, DuPont (Surlyn)... 

SEC-FTIR yields the average polymer structure as a function of molecular mass, but no information on the distribution of the chemical composition within a certain size fraction. SEC-FTIR is mainly used to provide information on MW, MWD, CCD, and functional groups for different applications and different materials, including polyolefins and polyolefin copolymers [703-705]. Quantitative methods have been developed [704]. Torabi et al. [705] have described a procedure for quantitative evaporative FUR detection for the evaluation of polymer composition across the SEC chromatogram, involving a post-SEC treatment, internal calibration and PLS prediction applied to the second derivative of the absorbance spectrum. 

Equation 1 illustrates a synthetic scheme which we have used in the preparation of polyolefin graft copolymers. Borane group containing polyolefin copolymers (I) were obtained by direct copolymerization [9,10] of a-olefin/borane containing a-olefin and a... 

After PVC, polyolefin copolymers, predominantly polyethylene copolymers, are the next most widely used material for FR applications in wire and cable. Polyethylenes have very good dielectric strength, volume resistivity, mechanical strength, low temperature flexibility, and water resistance. In contrast to PVC, polyolefins are not inherently FR and thus are more highly formulated, requiring the addition of FRs to meet market requirements for flame retardancy. For this reason, and because of the steady global trend toward halogen-free materials for wire and cable applications, more space will be devoted to this section on FR polyolefins compared with the above discussion of PVC. 

EVAs (polyolefin copolymer) have exceptional barrier properties, good clarity and gloss, stress-crack resistance, low temperature toughness/ retains flexibility, adhesion, resistance to UV radiation, etc. They have low resistance to heat and solvents as well as exceptional weathering resistance. 

None 200-220 PP, PS, HDPE, EVA, ABS, SMA, polyolefin copolymers, blends, cross-linked polymers... 

In the past decade, our group at Penn State has been focusing on a functionalization approach by the combination of metallocene catalysts and reactive comonomers. The chemistry takes the advantage of metallocene catalyst with a tunable single active site to prepare polyolefin copolymers with narrow molecular weight and composition distributions, high catalyst activities, and predictable tacticities and copolymer compositions. 

Chung, T.C. Synthesis of functional polyolefin copolymers with graft and block structures. Prog. Polym. Sci. 2002, 27, 39. 

Polyolefin copolymers started with LLDPE and ethylene-propylene rubber (EPR). Today, there are polyolefin copolymers of ethylene with butene-1, hexene-1, octene, cyclopentene, and norbornene and copolymers of propylene with butene-1, pentene-1, and octene-1 in addition to ethylene. There are copolymers of butene-1 with pentene-1, 3-methylbutene-l, 4-methylpentene-1, and octene in addition to its copolymers with ethylene and propylene. There are copolymers of 4-methylpentene-1 with pentene-1 and hexene-1 in addition to its copolymers with butene-1 and propylene. The function of the comonomers is to reduce crystallinity, as compared to the homopolymers, resulting in copolymers that are highly elastomeric with very low... 

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... 

Isotactic PP and ICP can be physically blended with EPR to adjust the modulus and the impact resistance. Recently, new types of polyolefin copolymers have been developed to replace EPR with higher compatibility with PP using metallocene catalysts. These polyolefin copolymers will be discussed in Section 8.4. Nitta et al. (7) compared the PP/EPR blends with different EPR in terms of My, MWD, and crystallinity. The different compatibility of EPR with PP creates different morphologies, which are shown in Fig. 8.5. 

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. 

CLASS Chemical copolymers polyolefin copolymer ter-pol5mier elastomer... 

This new family of polyolefin copolymers hcis a significantly different chain microstructure than conventional LLDPE.The single site characteristics of metallocenes, with the catalyst site being identical, are known to produce materials having the most probable molecular weight distribution /M 2.0), with essentially a random comonomer distribution and narrow composition distribution. The comonomers most frequently used commercially are butene, hexene, and octene. Copolymerization of ethylene with 4-methyl-l-penetene (4-MP-l) and cyclic and bicylic groups has been also reported in the literature. Several terpolymers are also commercially available.Exxon Chemical Company manufactures ethylene-butene copolymers, ethylene-hexene copolymers, and terpolymers of butene and hexene comonomers. Exxon markets these mLLDPEs under the trademark name of... 

Polyketones Polynitriles Polyolefin copolymers Poly(alpha-olefins)... 

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