Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Poly methylene

CHR) , formed, e g. from the reaction of diazomethane and alcohols or hydroxylamine derivatives in the presence of boron compounds or with metal compounds. Poly-methylene is formally the same as polyethene and the properties of the various polymers depend upon the degree of polymerization and the stereochemistry. [Pg.320]

Commonly used isocyanates are toluene dhsocyanate, methylene diphenyl isocyanate, and polymeric isocyanates. Polyols used are macroglycols based on either polyester or polyether. The former [poly(ethylene phthalate) or poly(ethylene 1,6-hexanedioate)] have hydroxyl groups that are free to react with the isocyanate. Most flexible foam is made from 80/20 toluene dhsocyanate (which refers to the ratio of 2,4-toluene dhsocyanate to 2,6-toluene dhsocyanate). High-resilience foam contains about 80% 80/20 toluene dhsocyanate and 20% poly(methylene diphenyl isocyanate), while semi-flexible foam is almost always 100% poly(methylene diphenyl isocyanate). Much of the latter reacts by trimerization to form isocyanurate rings. [Pg.1022]

Acetal Resins. Acetal resins (qv) are poly (methylene oxide) or polyformaldehyde homopolymers and formaldehyde [50-00-0] copolymeri2ed with ahphatic oxides such as ethylene oxide (42). The homopolymer resin polyoxymethylene [9002-81-7] (POM) is produced by the anionic catalytic polymeri2ation of formaldehyde. For thermal stabiUty, the resin is endcapped with an acyl or alkyl function. [Pg.265]

PMPPIC = poly(methylene) poly(phenyl) isocyanate PVC = poly(vinyl chloride) p = density Tf = fiber radius... [Pg.835]

Here m is the mode order (m — 1,3,5. .., usually 1 for polyethylenes), c the velocity of light, p the density of the vibrating sequence (density of pure crystal) and E the Young s modulus in the chain direction. The LAM band has been observed in many polymers and has been widely used in structural studies of polyethylenes [94—99,266], as well as other semi-crystalline polymers, such as poly (ethylene oxide) [267], poly(methylene oxide) [268,269] and isotactic poly(propylene) [270,271], The distribution of crystalline thickness can be obtained from the width of the LAM mode, corrected by temperature and frequency factors [272,273] as ... [Pg.284]

A theoretical investigation of the use of NMR lineshape second moments in determining elastomer chain configurations has been undertaken. Monte Carlo chains have been generated by computer using a modified rotational isomeric state (RIS) theory in which parameters have been included which simulate bulk uniaxial deformation. The behavior of the model for a hypothetical poly(methylene) system and for a real poly(p-fluorostyrene) system has been examined. Excluded volume effects are described. Initial experimental approaches are discussed. [Pg.279]

For poly(methylene), an exclusion distance (hard sphere diameter) of 2.00 A was used to prevent overlap of methylene residues. The calculation reproduced the accepted theoretical and experimental characteristic ratios (mean square unperturbed end-to-end distance relative to that for a freely jointed gaussian chain with the same number of segments) of 5.9. This wps for zero angular bias and a trans/gauche energy separation of 2.09 kJ mol". ... [Pg.284]

A preferable system is poly(p-fluorostyrene) doped into poly(styrene). Since rotations about the 1,4 phenyl axis do not alter the position of the fluorine, the F spin may be regarded as being at the end of a long "bond" to the backbone carbon. In standard RIS theory, this polymer would be treated with dyad statistical weights to automatically take into account conformations of the vinyl monomer unit which are excluded on steric grounds. We have found it more convenient to retain the monad statistical weight structure employed for the poly(methylene) calculations. The calculations reproduce the experimental unperturbed dimensions quite well when a reasonable set of hard sphere exclusion distances is employed. [Pg.286]

Recent investigations have indicated that the aliphatic carbon fraction, rather than aromatic fraction, was strongly correlated to HOC sorption. For instance, the sorption of phenanthrene was related to nonpolar aliphatic carbon fraction, excluding poly(methylene), but was very strongly correlated with the content of the amorphous nonpolar aliphatic domains including amorphous poly(methylene) (Mao et al. 2002). In other words, the rubbeiy, relatively low-density, and amorphous nonpolar aliphatic carbon domains are excellent for phenanthrene partitioning (Figs. 3 and 4). [Pg.130]

Nonpolar aliphatics excluding poly(methylene), sample weight %... [Pg.130]

Fig. 3. Correlation of the modified Freundlich coefficient K oc with the weight fraction of (a) nonpolar aliphatic carbon, excluding poly(methylene) and (b) amorphous nonpolar aliphatic carbon in domains, including amorphous poly(methylene). Adapted from Mao et al. (2002). Fig. 3. Correlation of the modified Freundlich coefficient K oc with the weight fraction of (a) nonpolar aliphatic carbon, excluding poly(methylene) and (b) amorphous nonpolar aliphatic carbon in domains, including amorphous poly(methylene). Adapted from Mao et al. (2002).
Hu W, Mao J, Xing B, Schmidt-Rohr K (2000) Poly(methylene) crystallites in humic substances detected by nuclear magnetic resonance. Environ Sci Technol 34 530-534... [Pg.140]

Mao J, Flundal L, Thompson M, Schmidt-Rohr K (2002) Correlation of poly(methylene)-rich amorphous aliphatic domains in humic substances with sorption of a nonpolar organic contaminant, phenanthrene. Environ Sci Technol 36 929-936... [Pg.141]

HV Alginate 2% Spermine/1% Poly-methylene-co-guanidine T Smooth, Mosaic Membrane (Polymer Incompatibility ) 7/7... [Pg.63]

Structural characterization of crystalline phases of poly(methylene-l,3-cyclopentane) samples of different microstructures have also been reported (a) Ruiz de Ballesteros, O. Venditto, V. Auriemma, F. Guerra, G. Resconi, L. Waymouth, R. M. Mogstad, A. L. Macromolecules 1995, 28, 2383. (b) Ruiz de Ballesteros, O. Cavallo, L. Auriemma, F. Guerra, G. Macromolecules 1995, 28, 7355. [Pg.65]

PMPPIC Poly(methylene) poly(phenylene) isocyanate... [Pg.261]

Recent advances in the development of well-defined homogeneous metallocene-type catalysts have facilitated mechanistic studies of the processes involved in initiation, propagation, and chain transfer reactions occurring in olefins coordi-native polyaddition. As a result, end-functional polyolefin chains have been made available [103].For instance, Waymouth et al.have reported about the formation of hydroxy-terminated poly(methylene-l,3-cyclopentane) (PMCP-OH) via selective chain transfer to the aluminum atoms of methylaluminoxane (MAO) in the cyclopolymerization of 1,5-hexadiene catalyzed by di(pentameth-ylcyclopentadienyl) zirconium dichloride (Scheme 37). Subsequent equimolar reaction of the hydroxyl extremity with AlEt3 afforded an aluminum alkoxide macroinitiator for the coordinative ROP of sCL and consecutively a novel po-ly(MCP-b-CL) block copolymer [104]. The diblock structure of the copolymer... [Pg.44]


See other pages where Poly methylene is mentioned: [Pg.789]    [Pg.145]    [Pg.205]    [Pg.947]    [Pg.162]    [Pg.826]    [Pg.835]    [Pg.328]    [Pg.618]    [Pg.285]    [Pg.291]    [Pg.86]    [Pg.89]    [Pg.130]    [Pg.52]    [Pg.144]    [Pg.144]    [Pg.106]    [Pg.42]    [Pg.85]    [Pg.260]    [Pg.271]    [Pg.278]   
See also in sourсe #XX -- [ Pg.176 , Pg.180 , Pg.182 , Pg.317 ]




SEARCH



Methylene carbon poly

Methylene diisocyanate poly

Poly iodides 662 -methylenes

Poly methylene , degradation

Poly methylene compounds

Poly methylene diamines

Poly methylene ditellurium)

Poly methylene tellurium)

Poly oxy methylene

Poly(aryl methylenes)

Poly(methylene) Chains

Poly[methylene-l,3-

© 2024 chempedia.info