Polymeric containing

The propagation centers of the catalysts of olefin polymerization contain the active transition metal-carbon olefin polymerization may be divided into two vast classes according to the method of formation of the propagation center two-component and one-component.1... 

Figure 2. Factors influencing taste/odor of carbonated beverages in polymeric containers...

Table II. Criteria Affecting Taste/Odor of Soft Drinks and Malt Beverages in Polymeric Containers...

Nearly all of the polymers produced by step-growth polymerization contain heteroatoms and/or aromatic rings in the backbone. One exception is polymers produced from acyclic diene metathesis (ADMET) polymerization.22 Hydrocarbon polymers with carbon-carbon double bonds are readily produced using ADMET polymerization techniques. Polyesters, polycarbonates, polyamides, and polyurethanes can be produced from aliphatic monomers with appropriate functional groups (Fig. 1.1). In these aliphatic polymers, the concentration of the linking groups (ester, carbonate, amide, or urethane) in the backbone greatly influences the physical properties. 

The mechanism of the polymerization contains ionic intermediate steps. The free H+ goes to a carbenium ion and, as shown in route B, rearranges to form tetrapropylene. It is highly likely that this actual tetrapropylene exists only in very small concentrations. The product variety is explained by the rearrangement of the carbenium ion to dodecene isomers according to route C. In addition, short-chain olefins formed by fragmentation (route D). Polymerization proceeds at almost 100% to mono olefins. Aromatics, paraffins, and diolefins exist only in trace amounts. The propylene tetramer is best characterized by its distillation range. 

Heterochain polymers produced by ring-opening polymerization contain the hetero-atoms in the main chain as well as in the monomer and the polymer chain competes with the monomer for the reaction with the propagating species. This competition leads to polymer transfer and back-biting reactions during the polymerization. Heterochain polymers are also susceptible to depolymerization by the ionic active species which are easily formed during processing. 

The DB obtainable in SCVP is DB=0.465 for r=kjk =l and reaches its maximum, DB=0.5, for r=2.6 [70,78]. This value is identical to that obtained in AB2 polycondensation when both B functions have the same reactivity [70,78]. Thus, hyperbranched polymers prepared by bulk polycondensation or polymerization contain at least 50% linear units, making this approach less efficient than the synthesis of dendrimers. 

Blow molding is widely used to make polymeric containers of all sorts. In many markets blow molded plastic products have largely displaced such traditional materials as glass, ceramics, or metal. The inherent advantages of polymeric containers include their light weight, clarity, toughness, and versatility. —... 

Aeropak process—simultaneous blow-molding and inner-surface fluorination of polymeric containers—is the most well-known example of an in-situ treatment process. 

For some time now, it has been proposed that the structural variations observed in DHP s are caused by the mode of polymerization, with bulk polymerization containing more condensed units than end-wise polymerization (32,33). However, in these experiments, DHP s prepared under the same conditions gave different D.S. values depending upon the pH at which the reaction took place. This result suggests that the molecular structure of lignin in the cell wall can also be controlled by factors other than the mode of polymerization. 

The products of most anionic and cationic polymerizations contain as much as 10-20% cyclic oligomers, mostly tetramer to hexamer. 

Formula AIH3 MW 30.005 Structure polymeric, containing residual ether ... 

Jenke DR, Chess EK, Zietlow D, Rabinow BE. Model for estimating the accumulation of solutes leaching from polymeric containers into parenteral solutions. Int J Pharm 1992 78 115. 

A series of complexes of the type ML(SCN) (C104)2-, (M - Zn, Cd, or Hg x = 1 or 2) has been prepared where L is en and its tetramethyl derivative, diethylenetriamine and its pentamethyl derivative, triethylenetetramine and its hexamethyl derivative, and bis(ethylenediamine). The complexes are either monomeric with four-, five- or six-coordinate metal, or polymeric containing bridging thiocyanate the perchlorate is always ionic. The thiocyanate is generally bonded through nitrogen to zinc and cadmium (and through sulfur to mercury).181... 

The structure of Cd2(pn)2(NCS)4 is polymeric, containing bridging NCS groups. Two crystallographically distinct Cd atoms are again present one is octahedrally coordinated by five N atoms (two from propylenediamine and three from SCN) and one S atom, the other by three N and three S atoms.1068... 

The surface of the sample container may interact with the analyte. The surfaces can provide catalysts (e.g., metals) for reactions or just sites for irreversible adsorption. For example, metals can adsorb irreversibly on glass surfaces, so plastic containers are chosen for holding water samples to be analyzed for their metal content. These samples are also acidified with HNO3 to help keep the metal ions in solution. Organic molecules may also interact with polymeric container materials. Plasticizers such as phthalate esters can diffuse from the plastic into the sample, and the plastic can serve as a sorbent (or a membrane) for the organic molecules. Consequently, glass containers are suitable for organic analytes. Bottle caps should have Teflon liners to preclude contamination from the plastic caps. 

The reaction between adipic acid and hexamethylene diamine produces hexamethylenediammonium adipate, commonly called nylon salt (Fig. 1) Forming the salt assures the correctly balanced proportions. It is also necessary that the material to be polymerized contain very few impurities if high-quality fibers are to be made by a variety of routes (Fig. 2). 

Fig. 6 Typical metallocene catalysts for olefin polymerization containing a C2-symmetric ligand (left) and a Cs-symmetric ligand (right)...

In using a similar approach, Thiine et al. [29] applied static SIMS to show that Cr/SiC>2 model catalysts which are active for ethylene polymerization contain only monochromates. Secondary ions with more than one Cr ion in the cluster, such as Cr2C>4 and Cr203, disappeared from the spectra after the catalysts had been calcined only CrSiOx ions remained. Aubriet et al. [30] studied the anchoring of chromium acetyl acetonate, Cr(acac)3 to a planar SiO2/Si(100) model support with static SIMS. Chromium polymerization catalysts are discussed further in Chapter 9. 

The second type of monomer for step-growth polymerization contains two different functional groups. Examples in this category include hydroxy acids such as lactic acid (or hydroxy esters [Equations 1-3]), and amino acids. A third type includes cyclic monomers such as lactones, lactams, and cyclic ethers. Cyclic monomers polymerize by ring-opening polymerization. Some, as we said, proceed by step-growth and some by chain-growth mechanisms. 

To make such materials, what might happen if we simply mixed two (or more) monomers in a polymerization reactor Many pairs of monomers participate in copolymerizations in a straightforward way. In other cases, however one monomer prefers to polymerize with itself rather than with the other monomer. In these cases the reaction mixture at the end of the polymerization contains polymer samples with widely different compositions rather than the expected random copolymer. Some chains are much richer in one monomer... 

From a chemical standpoint there is little evidence at present to prefer PF6 over SbFe or vice-versa. Both gegenions seem considerably more stable than BF4 or SbCl6". The BF4 polymerization contains considerable termination, and the SbCl6" polymerization contains considerable transfer and some termination. It is interesting to note that both results can be explained in terms of a similar reaction with gegenion. 

The most widely used initiator systems for acetaldehyde polymerization contain aluminum alkyls and zinc alkyls modified with water, alcohols, and amines (14,15, 24, 25, 37, 39, 42, 44, 47). 

Sc and Lu derivatives are isomorphous and polymeric containing [r/5-(C5H5)2Ln(p,-r] -CsHs)]. In the case of SmCp3, two crystallographically independent molecules bonded to each other by non-valence interactions has been observed [25]. 

The alkenes most reactive to cationic polymerization contain electron-donating functional groups that can stabilize the carbocation intermediate. The reactivity order of substituents in cationic polymerization is similar to the reactivity order of substituted benzenes in electrophilic aromatic substitution reactions. 

The mechanism of ADMET polymerization (Scheme 5) contains intermediates similar to those found in ROMP chemistry in that both polymerizations contain, inclusively, various metallacyclobutane/carbene species." Although ROMP propagates exclusively via trisubstituted metallacycles, whereas ADMET requires disubstituted metallacycles, the major difference is that ADMET step chemistry is an equilibrium process driven by condensation and ROMP chain chemistry propagates irreversibly owing to the high reactivity of the carbene with strained cycloalkenes. Therefore ROMP is much faster than ADMET simply because competing equihbria, absent during ROMP, decrease the net productive rate in ADMET chemistry. 

Anionic polymerization not only allows the production of low residual PS (i.e. typically PS produced using continuous anionic polymerization contains <20 ppm residual styrene) but also anionically produced PS is more thermally... 

PS produced by anionic polymerization contains fewer weak links than PS prepared using free radical chemistry [44] ... 

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