Copolymers units

Property ASTM test Acetal homopolymer Acetal copolymer Unit... 

I. Pastorova, T. Weeding, J.J. Boon, 3 Phenylpropanylcinnamate, a copolymer unit in siegbur gite fossil resin a proposed marker for the Hamamelidaceae, Organic Geochemistry, 29, 1381 1393 (1998). 

C. Xia and R.C. Advincula, Decreased aggregation phenomena in polyfluorenes by introducing carbazole copolymer units, Macromolecules, 34 5854-5859, 2001. 

The copolymer compositions were studied by elemental microanalyses and H-NMR, revealing that the content of the copolymer units is in aU cases very similar to that of their corresponding feed. The PU(DiT-HDl) homopolymer exhibited a high crystallinity, but the introduction of the arabinitol-based diols led to a reduction in the crystallinity of the copolymers. In their TGA curves, the copolymers exhibited a mixed trend of the related homopolymers, and all of them were thermally stable, with degradation temperatures above 220°C. The degradation... 

Previous investigations (4, 5,6,7,8) have shown that block copolymers exhibit unusual melt rheological properties such as a very high viscosity, elasticity, and non-Newtonian behavior even at very low shear rates which are all attributed to the multiphase structure resulting from the incompatibility between the two copolymer units in the melt state. 

Copolymer units interact via hydrogen bonds both with the other macromolecules and with the comonomer units of their own chain (for example, the PMAA-VP/ AA system21. ... 

Copolymer units in the same chain may interact with themselves as in a polyampholyte and the interchain interactions may occur via hydrogen bonds. Such complexes are formed in polyvinylpyrrolidone - methacrylic acid and vinylpiperidole copolymer systems72. ... 

Mechanical studies have also been performed on another non-LCP system -copolyesters of PET and PEN, where both copolymer units having flexible chain segments and lack a liquid-crystalline behaviour (Santa Cruz et al, 1992). The whole range of PET/PEN copolymers can therefore be prepared in the amorphous state. 

Heat capacities of polymer are complicated by physical and chemical structural changes, namely by changes in crystallinity, crystal structure, morphology, tacticity, molecular weight and copolymer unit content. Furthermore the picture can be complicated by changes in mechanical, thermal and possibly electrical history of the polymer. 

Gas-phase polymerization in a fluidized bed reactor (heterophasic impact and specialty copolymer) as a further option. The gas phase copolymer unit can be added at a later stage without affecting the initial plant configuration or involving significant implementation costs (Figure 17.4). 

Extensive work with condensation polymers and copolymers fully confirms the importance of structural regularity on crystallization tendency, and consequently on associated properties. Thus, copolymers containing regular alteration of each copolymer unit, either ABABAB type or block type, show a distinct tendency to crystallize, and corresponding copolymers with random distributions of the two are intrinsically amorphous, less rigid, lower melting, and more soluble. 

This concept is, in essence, the result of neighboring units of a copolymer having a lower affinity for these units than the units of another polymer or copolymer. Miscibility can occur if the interaction energy (interaction parameter) is more positive for the copolymer units than the interactions between these units and the admixed polymer. Cases can easily exist where all the... 

General formula represents the number of each element in homopolymer units and in copolymer units, separated by a hyphen. The sequence of elements is conventional — alphabetical, but starting with C and H . 

Greater success was achieved by DuPont who copolymerized, the sodium salt of 5-sulfoisophthalic acid into PET to render the polymer dyeable with cationic (basic) dyes. Basic dyeable PET was successfully launched as Dacron 64 in the form of a low-pill staple product [64]. The presence of the sulfonate groups in the polymer chain also acts as an ionic dipolar cross-link and increases the melt viscosity of the polymer quite markedly. Thus, it is possible to melt-spin polymer with IV 0.56 under normal conditions, giving a low-pill fiber variant. The fiber also has a greater affinity for disperse dyes due to the disruption of the PET structure. Continuing this theme, there are deep dye variant PET fibers, often used in PET carpet yarns, which are copolymers of PET with chain-disrupting copolymer units like polyethylene adipate. They have less crystallinity and a lower Tg. therefore, they may be dyed at the boil without the use of pressure equipment or carrier at the cost of some loss of fiber physical properties. 

Johnson, L.K., Killian, C.M. and Brookhart, M. (1995) New Pd(II)-based and Ni(II)-based catalysts for polymerization of ethylene and alpha-olefins. Journal of the American Chemical Society 117,6414-6415. Wunderlich, B. and Poland, D. (1963) Thermodynamics of crystalline linear high polymers. 2. Influence of copolymer units on thermodynamic properties of polyethylene. Journal of Polymer Science Part a-General Papers 1, 357. 

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