Polybutene-1 isotactic

It is well known, for instance, the case of isotactic polybutene (i-PB), in which the three known crystalline forms (referred to as I, II, and III) contain helices with a number of constitutional repeating units per turn in the range 3-4 (3/1, 11/3, 4/1 helices, respectively) all corresponding to regular sequences of nearly trans and nearly gauche dihedral angles [3,21]. 

Table 1. 13C solid-state chemical shifts1 of some resonances observed in the NMR spectra of different forms of isotactic polybutene [116]... 

The main use of 1-butene is as a comonomer for linear low-density polyethylene (LLDPE), for which there is a fast growing demand it is used to a lesser extent for the production of isotactic polybutene. 

Isotactic polybutene crystallizes into three different forms. When it cools from the melt, it initially crystallizes into a metastable crystalline one. After several days, however, it transforms into a different form. Noticeable changes in melting point, density, flexural modulus, yield, and hardness accompany this transformation. The third crystalline form is due to crystallization from solution. The polymer exhibits good impact and tear resistance. It is also resistant to environmental stresscracking. 

Ternary blends contained 87-96 wt% LLDPE (with either butene-1, hexene-1, or octene-1), 1-10 wt% isotactic polybutene, 1-10 wt% PS, and 0.01-10 wt% color and anti-blocking agents. The blends exhibited improved process efficiency in terms of extruder amps/ rpm ratio, while the terpolymer substantially retained the inherent strength of the LLDPE. The compositions were used for blown films and for the manufacture of waste bags ... 

Finally, a few comments about the uniqueness of polymer crystal structures and phase space localization are warranted. Almost all crystallizable polymers exhibit polymorphism, the ability to form different crystal structures as a result of changes in thermodynamic conditions (e.g., temperature or pressure) or process history (e.g., crystallization conditions) [12]. Two or more polymorphs of a given polymer result when their crystal structures are nearly iso-energetic, such that small changes in thermodynamic conditions or kinetic factors cause one or another, or both, to form. Polymorphism may arise as a result of competitive conformations of the chain, as in the case of syndiotactic polystyrene, or as a result of competitive packing modes of molecules with similar conformations, as in the case of isotactic polypropylene. In some instances, the conformational change may be quite subtle isotactic polybutene, for example, exhibits... 

SEBS was used to compatibilize PP with either PS or HIPS. The blends showed good impact and flexural strength [34]. Addition of SEBS was found to be expensive but useful in many recycling processes. Other compatibilizers for commingled polymeric scrap containing PS and PO and other resins, are CSR, SBR, (SB)n block copolymers, polybutylene-1, a copolymer of butylene-1 and ethylene, isotactic polybutene [3], etc. 

Fig. 16-12. Storage and loss moduli in extension at 100 Hz, plotted with logarithmic scale against temperature for isotactic polystyrene (PS), isotactic polypropylene (PP), and isotactic polybutene-1 (PB-1), crystallized from the melt. Degrees of crystsdlinity estimated as 43%, 65%, and 45% respectively. (Takayanagi. )...

The difi actograms of nascent copolymer samples clearly show that dififaction reflections shift to smaller diffraction angles. For statistical propylene-1-butene copol5miers, this effect was repeatedly observed for various catalytic systems.This outcome may be explained by the fact that, even after replacement of a certain amount of propylene units with 1-butene units, copol5mier macromolecules continue formation of the crystalline component of a-PP but have other imit-cell parameters. In fact, in the case of isotactic PP, a macromolecule occurs in the conformation of the 3/1 helix with a cross-sectional area of 0.34 nm and an identity period of 0.65 mn for all polymorphic structures. Although isotactic polybutene exhibits the conformational type of polymorphism, it has polymorphic stmcture, in which macromolecules assiune the conformation of the 3/1 helix with a cross-sectional area of 0.44 mn and an identity period of 0.65... 

Various combinations of compounds to from the dfective catalyst systems for butene-2 polymerization to polybutene-1 have been disclosed in a patent by Chauvin and Lefebvre (21). According to this patent, the addition of Lewis bases such as triethylamine, pyridine and tetramethyl-ammonium iodide to S ler-Natta catalysts increases the yield of ethyl ether insoluble isotactic polybutene-1. 

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