摘要:

The purpose of this study was to elucidate the mechanism whereby a protective animal colloid acts to prevent agglomeration of solvated nitrocellulose spheres during the manufacture of small arms propellant. To accomplish this, glycine and several glycine-containing peptides were incorporated into cast films of nitrocellulose and studied by means of infrared spectroscopy and X-ray photoelectron spectroscopy. Also, each of the amino acids and peptides were studied by means of infrared spectroscopy in water solution with suspended di-n-butyl phthalate present. The resulting interactions are described.

ISSN:0022-233X    

DOI:10.1080/00222338008056735

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Thermal stability of samples of polychloral prepared with different initiators and treated with various endcapping agents was studied using differential thermogravimetric analysis (DTG). Four temperature regions at which maxima of DTG curves occur were identified. On the basis of the known mechanism of initiation and the possible mechanism of termination, the structures of both initial and terminal endgroups of individual polychloral samples were elucidated which enabled the identification of the specific temperature region of thermal degradation of polychloral molecules having a specific type of endgroup. These results were confirmed by studies of the DTG curves of chloral-isocyanate copolymers containing stable terminal fragments with a high content of urethane linkages.

ISSN:0022-233X    

DOI:10.1080/00222338008056736

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Polybenzoxazoles of relatively low molecular weight have been prepared from hexa-n-propylorthoisophthalate in DMSO at 100°C. Unlike the preparation of polybenzimidazoles via the same route which gave high molecular weight linear polybenzimidazoles, condensation of dihydroxy-diaminobiphenyl with bisorthoesters gave only polymers of low molecular weight. It has not been established but it is most likely that the formation of only low molecular weight polymers was caused by the low basicity of the aromatic amino groups. Benzimidazoles of low molecular weight had also been observed when aromatic tetramines of low basicity were used for the condensation with bisorthoesters.

ISSN:0022-233X    

DOI:10.1080/00222338008056737

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Thermal properties of precipitated samples and films of poly-γ-benzyl-L-glutamate (PBG) and poly-L-glutamic acid (PGA) have been studied using TGA, DSC, and pyrolysis. The PBG film was identified as that described by McKinnon and Tobolsky as “form C” (“film A” of Uematsu et al.) using IR, dielectric relaxation, and DSC data. The PGA film is α-helical (IR) and was further characterized by dielectric relaxation measurements. With the exception of water loss at ∼110° from PGA, TGA and DSC measurements reveal only incomplete endotherms corresponding to decomposition. Volatile decomposition products were trapped and identified using combined GC/IR and GC/MS techniques. Identified products were as follows: from PGB–CO2, NH3, H2O, toluene, benzaldehyde, benzyl alcohol, and benzoic acid; from PGA–CO2, NH3, CH3OH, acetone, and H2O. Only minor differences were noted in GC traces of the total volatile decomposition products in air or in nitrogen streams. No evidence for retained solvent in cast films was obtained.

ISSN:0022-233X    

DOI:10.1080/00222338008056738

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The theoretically expected network chain-length distribution for networks where the cross-link points are randomly distributed in the bulk of the material would contain a significant fraction of network chains which are much shorter than the average chain length. The contribution of these very short chains to the stress born by a network is an important consideration in chemical stress relaxation studies. It is proposed that by use of a gamma distribution function as a “functional” network chain-length distribution, the effect of such short network chains might be taken into account in deriving stress-time expressions for chemical stress relaxation studies. While this procedure yields a simple expression for the fractional residual stress at a given extent of scission, the error involved in neglecting the effect of the chain-length distribution appears to be small.

ISSN:0022-233X    

DOI:10.1080/00222338008056739

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

It has been found that ethylene-acrylic acid copolymers can be prepared by extruder cracking of ethylene-isopropyl acrylate copolymers. The cracking of the ester to the acid goes very smoothly to give 90-100% conversion; however, the melt index behavior of the product is quite complex. The melt index of the starting ester copolymer was 2.0, but the melt index of the thermally cracked product immediately after extrusion was only 0.1. On standing, the melt index of the product slowly increased to 30.0. This complex melt index behavior is related to anhydride formation and chain scission reaction in the extruder. The anhydride linkages give a pseudocross-linked structure and lead to an initial low melt index value. On standing, the anhydride groups are hydrolyzed with water from the atmosphere to give an uncross-linked acid copolymer. After the acid is formed, the main chain polymer scissions that have occurred during extrusion become evident and the high melt index value is observed.

ISSN:0022-233X    

DOI:10.1080/00222338008056740

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

2-Mercaptobenzothiazolyl methacrylate (MBTM) was synthesized by the reaction of 2-mercaptobenzothiazole and methacrylyl chloride in tetrahydrofuran at -18°C. MBTM was found to polymerize in the presence of 2,2′-azobisisobutyronitrile (AIBN), n-BuLi, and UV light. From the kinetic studies of radical polymerization of MBTM with AIBN in benzene at 60°C, the overall activation energy was determined to be 18.9 kcal/mole, and the rate of polymerization (R) was expressed as Rp= k[AIBN]0.5[MBTM], where k is the overall polymerization rate constant. From these results this polymerization was confirmed to proceed via an ordinary radical mechanism. This monomer (M2) was also copolymerized radically with styrene (M1) at 60°C, and the resulting copolymerization parameters were determined as r1= 0.042, r2= 0.20, Q2= 4.09, and e2= 1.39. The thermal stability and the photodegradation behavior of the polymers were examined, and they were compared with those of the related polymers.

ISSN:0022-233X    

DOI:10.1080/00222338008056741

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Polymerization of acrylonitrile initiated by triazole-copper(II) complexes was studied in dimethylsulfoxide solution. It was found that the polymerization proceeds by a free radical mechanism; however, the complexes can hardly homopolymerize methyl methacrylate and styrene. Ability of the complexes to initiate polymerization seems to depend on the substituents of triazole, the sort of solvents, and the counterions of copper(n) salts. From the data of visible spectroscopy and the spin trapping, the initiation mechanism was discussed in terms of reduction of copper(II) followed by forming active species.

ISSN:0022-233X    

DOI:10.1080/00222338008056742

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

For the AIBN-initia ted copolymerization System acryionitriie/methyl methacrylate/dimethylformamide, the dependence of the composition of the monomer mixture on the rate constant of initiation and that of the initiator decomposition has been inves-tigated at 313, 323, and 333° K. It was established that the rate constant of initiator decomposition is independent of, while that of the initiation is dependent on, the composition of the monomer mixture. The efficiency of initiation has been calculated and its value was found to be somewhat altered not only by the composition of the monomer mixture but also decreased siightiy with an increase of temperature.

ISSN:0022-233X    

DOI:10.1080/00222338008056743

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Methyl methacrylate (MMA), acrylic acid (AAc), and vinyl acetate (VAc) were graft copolymerized onto Himachali wool in an aqueous medium by using vanadium oxyacetyl acetonate as initiator. Graft copolymerization was studied at 45, 55, 65, and 75°C for various reaction periods. The percentage of grafting was determined as functions of concentration of monomers, concentration of initiator, time, and temperature. The maximum percentage of grafting with each monomer occurred at 55°. Several grafting experiments were carried out in the presence of various additives which include HNO3, DMSO, and pyridine. Nitric acid was found to promote grafting of MMA. All these additives had adverse effects on grafting of VAc and AAc. MMA, VAc, and AAc were found to differ in reactivity toward grafting and followed the order MMA > AAc > VAc.

ISSN:0022-233X    

DOI:10.1080/00222338008056744

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor