Polypropylene-butene plastic

Butene is used in the plastics industry to make both homopolymers and copolymers. Polybutylene (1-polybutene), polymerized from 1-butene, is a plastic with high tensile strength and other mechanical properties that makes it a tough, strong plastic. High-density polyethylenes and linear low-density polyethylenes are produced through co-polymerization by incorporating butene as a comonomer with ethene. Similarly, butene is used with propene to produce different types of polypropylenes. 

The polyolefins are those polymers based only on carbon and hydrogen, originating from monomers containing a double bond in the 1-position, sometimes called a-olefins. Principally, these include polyethylene, polypropylene, copolymers of polyethylene containing various comonomers such as 1-butene, 1-hexene, and 1-octene, ethylene-propylene monomer (EPM), and ethylene-propylene-diene-monomer (EPDM). All of these are plastics except EPM and EPDM, which are elastomers. 

Figure 5.259 shows the flat initial segments of the creep curve of polyethylenes of varying density and/or various degrees of crystallization. Although the curves slopes differ little from each other, they are less steep for lower densities. Similar behavior is found in all semi-crystalline plastics in which structural differences in the macromolecules in the form of branching cause relatively small differences in density, i.e., crystallinity, such as in polypropylene. Similar differences in polyethylene density are the result of integration of comonomers, such as propene-1, butene-1, hexene-1, or other a-olefins into the molecule chain [811]. 

From here on out, I will use the terms polyolefin or TPO to mean a thermoplastic polyolefin that is a blend (mechanical or so-called reactive types) of a plastic phase, primarily polypropylene, and an amorphous or elastomeric phase, consisting of truly ethylene-propylene copolymers or copolymers of ethylene with other a-olefins, such as butene or hexene. Considerations that must be addressed from both a commercial or practical point of view, as well as a theoretical or scientific point of view follow. 

In the 1980s, the fluidized bed process was modified to produce a copolymer similar in density to polyethylene produced by the older, high-pressure process. Copolymerization of ethylene with 1-butene or other normal alpha olefins introduces short pendant chains that decrease crystallinity. In the plastics business, the terms high-density, or linear, polyethylene and LDPE (or branched polyethylene) are now supplemented by linear LDPE (LLDPE). While all the properties of the high-pressure polymer are not achieved by the newer material, the economics of the low-pressure, solvent-free process are such that LLDPE competes successfully in many of the markets once dominated by branched LDPE. The fluidized bed itself is only one of several gas-phase polyolefin processes. Stirred beds, arranged either horizontally or vertically, do not depend on gas velocity and are less sensitive to uniformity of gas flow. The stirred beds have been used primarily for polypropylene [19]. However, the fluidized bed has also been adapted for production of polypropylene and propylene copolymers. 

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