摘要:

AbstractIn this investigation, repeated chemical stress relaxation measurements were carried out to observe the relaxation behavior at large deformation. It was found that the repeated chemical stress relaxation curves were affected by both measurement temperature and the extension ratio of rubber. It was suggested on the basis of the results that temperature and mechanical stimulus have a similar effect on the stress relaxation curves. Thus we propose the following Arrhenius type equation for high extension ratios:\documentclass{article}\pagestyle{empty}\begin{document}$$ {f \mathord{\left/ {\vphantom {f {f\left( {\rm O} \right)}}} \right. \kern-\nulldelimiterspace} {f\left( {\rm O} \right)}} = A\exp \left( {te^{{{ - E_{\rm f} } \mathord{\left/ {\vphantom {{ - E_{\rm f} } \alpha }} \right. \kern-\nulldelimiterspace} \alpha }} } \right) $$\end{document}where α is the extension ratio andA, Bare constants determined experimentally. On the other hand, from this equation and the usual Arrhenius equation, a universal equation for the extension ratio and the temperature was derived as follows:\documentclass{article}\pagestyle{empty}\begin{document}$$ \ln \left[ {{{\left( {{{\ln f\left( {\rm O} \right)} \mathord{\left/ {\vphantom {{\ln f\left( {\rm O} \right)} f}} \right. \kern-\nulldelimiterspace} f}} \right)} \mathord{\left/ {\vphantom {{\left( {{{\ln f\left( {\rm O} \right)} \mathord{\left/ {\vphantom {{\ln f\left( {\rm O} \right)} f}} \right. \kern-\nulldelimiterspace} f}} \right)} t}} \right. \kern-\nulldelimiterspace} t}} \right] - {E \mathord{\left/ {\vphantom {E {R\left[ {\left( {{1 \mathord{\left/ {\vphantom {1 {T_0 }}} \right. \kern-\nulldelimiterspace} {T_0 }}} \right) - \left( {{1 \mathord{\left/ {\vphantom {1 T}} \right. \kern-\nulldelimiterspace} T}} \right)} \right]}}} \right. \kern-\nulldelimiterspace} {R\left[ {\left( {{1 \mathord{\left/ {\vphantom {1 {T_0 }}} \right. \kern-\nulldelimiterspace} {T_0 }}} \right) - \left( {{1 \mathord{\left/ {\vphantom {1 T}} \right. \kern-\nulldelimiterspace} T}} \right)} \right]}} = \ln A - {{E_{\rm f} } \mathord{\left/ {\vphantom {{E_{\rm f} } \alpha }} \right. \kern-\nulldelimiterspace} \alpha } $$\end{document}where,T0is voluntary temperature. The curves obtained by this equation were quite consistent with those obtained experimentally at different temperatures and extensions at large deformation

ISSN:0449-296X    

DOI:10.1002/pol.1972.170101001

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractTitanocene dichloride sensitized photopolymerization of vinyl ethers and styrene but did not polymerize methyl methacrylate and vinyl acetate. In the case of 2‐chloroethyl vinyl ether, polymerization started rapidly some time after the color of the liquid had changed from orange to green. Polymerization was also achieved by heating the monomer at 60°C after stopping the irradiation at the end of the induction period. On the basis of the reactivity of the monomers and the effect of additives, polymerization is considered to proceed cationically. In case of the polymerization of styrene, conversion increased linearly with time. Thek p2/ktvalue of 6.3 × 10−5l./mole‐sec obtained for the polymerization of styrene agrees well with the value reported for radical polymerization. The agreement of the value and ineffective inhibition of polymerization in the presence of pyridine indicates the polymerization follows a radical mechanism. Copolymerization of styrene (M1) and 2‐chloroethyl vinyl ether (M2) proceeded radically, and the reactivity ratios werer1= 2.5

ISSN:0449-296X    

DOI:10.1002/pol.1972.170101002

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractEquipment has been designed and assembled in such a way that direct microscopic observation of polymer particle formation in suspension polymerization of vinyl chloride and vinyl acetate is possible. The apparent mode of transformation from monomer droplets into polymer particles has thus been studied under two sets of conditions: (1) with agitation and (2) without agitation. In both cases, as the initial vinyl acetate/vinyl chloride ratio was raised, the apparent change in the shape and transparency of particles occurring during the course of polymerization became less evident. In vinyl chloride homopolymerization and vinyl acetate–vinyl chloride copolymerization with relatively high vinyl chloride concentrations, the polymer particles burst during the course of polymerization. Some factors which affect the change in the size of particles are also discusse

ISSN:0449-296X    

DOI:10.1002/pol.1972.170101003

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractThe branching reaction in the radical polymerization of vinyl acetate was studied kinetically. Branching occurs by polymer transfer as well as terminal double‐bond copolymerization. The chain‐transfer constants to the main chain (Cp,2) and to the acetoxy methyl group (Cp,1) on the polymer were calculated on the basis of the experimental data described in the preceding paper givingCp,2= 3.03 × 10−4,Cp,1= 1.27 × 10−4at 60°C, andCp,2= 2.48 × 10−4,Cp,1= 0.52 × 10−4at 0°C. Chain transfer to monomer is important with respect to the formation of the terminal double bond. The total values of transfer constants to the α‐ or β‐position in the vinyl group and the acetoxymethyl group in vinyl acetate was determined to be 2.15 × 10−4at 60°C. The transfer constant to the acetyl group in the monomer (Cm,1) was also evaluated to be 2.26 × 10−4at 60°C from the quantitative determination of the carboxyl terminals in PVA. These facts suggest that the chain‐transfer constant to the α‐ or β‐position in the monomer (Cm,2) is nearly equal to zero within experimental error. Copolymerization reactivity parameters of the terminal double bond were also estimated. In conclusion, it has become clear that the formation of nonhydrolyzable branching by the terminal double‐bond reaction can be almost neglected, and hence that the long branching in PVA is formed only by the polymer transfer mechanism. On the other hand, a large number of hydrolyzable branches in PVAc are prepared by the terminal double‐bo

ISSN:0449-296X    

DOI:10.1002/pol.1972.170101004

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractIn order to clarify the grafting behavior of vinyl trimethylacetate (VTMAc) onto poly‐(vinyl acetate) (PVAc), the polymerization of a radioactive VTMAc in the presence of a crosslinked PVAc gel was studied in accordance with the experimental technique described in the previous papers. It was found that, at 60°C, the grafting onto the main chain of PVAc takes place about 2.8 times as readily as that onto the acetyl side group on PV

ISSN:0449-296X    

DOI:10.1002/pol.1972.170101005

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractThe reaction of carbon disulfide with one or two equivalents of alkali metal (potassium‐ or sodium) was carried out, and the deep red reaction mixture obtained only in diethylene glycol dimethyl ether. The polymerization of vinyl monomers with this reaction mixture was studied. The reaction mixtures of mono‐ and dialkali metal with carbon disulfide induced the polymerization ofN‐phenylmaleimide, methyl vinyl ketone, and acrylonitrile but did not induce the polymerization of methyl methacrylate and styrene. In the polymerization of acrylonitrile with this reaction mixture of carbon disulfide with monoalkali metal, the polymerization rate was found to be proportional to the initiator concentration and to the square of the monomer concentration. The activation energy was −1.1 kcal/mole. Similar results were obtained in the case of carbon disulfide with dialkali metal. The polymer yield increased with increasing solvating power of solvents, i.e., diethylene glycol dimethyl ether, dimethyl sulfoxide, hexamethylphosphoramide, dimethylformamide, tetrahydrofuran. In the copolymerization of AN with MMA, the copolymer obtained consisted almost of A

ISSN:0449-296X    

DOI:10.1002/pol.1972.170101006

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractOrganolithium compounds and other Group IA organometallics cleave high molecular weight poly(alkylene oxides) very rapidly at room temperature in dilute benzene solution. This reaction also works on a dimeric polyepoxide such as bis(2‐n‐butoxyethyl)ether and much less readily on a monomeric one as 1,2‐dimethoxyethane. On the other hand, a simple aliphatic monoether such as di‐n‐butyl ether is not cleaved under conditions several orders of magnitude more drastic than were effective on the polyethers. The mechanism for this facile polyether cleavage is proposed as a β‐elimination in which the organolithium is greatly activated by chelation with the main‐chain oxygen atoms of the polyether. This cleavage method has been used broadly on high molecular weight polyethers to obtain quantitative yields of hydroxyl‐ended, amorphous, and crystalline polyethers (Mn= 500–10,000), many of which cannot be made by direct polymerization. Aliphatic polysulfides and anN‐substituted aliphatic polyamine cleave by this same method to, respectively, mercapto‐ended and secondary amine‐ended polymers. The mechanism aspects of the

ISSN:0449-296X    

DOI:10.1002/pol.1972.170101007

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractEpichlorohydrin polymers cleave much more readily with organolithium compounds than do other poly(alkylene oxides). In dilute toluene solution (1–2%) at −78°C, the cleavage of polyepichlorohydrin occurs as rapidly as BuLi is added. The end‐groups formed are about equimolar amounts of hydroxyl and carbonyl with small amounts of acetylene ends. This same cleavage reaction but without acetylene ends can be obtained with NaOH or NaOCH3in dimethyl sulfoxide at 65°C. The carbonyl groups can be reduced with LiAlH4in tetrahydrofuran to give hydroxyl‐ended polymers. A mechanism is presented for this unusual cleavage

ISSN:0449-296X    

DOI:10.1002/pol.1972.170101008

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractThe theoretical kinetics of reversible polymerization of a live polymer solution is studied. The initiation, transfer, and termination reactions are assumed to be negligible. An analytic solution in a closed form is obtained which gives the transient monomer concentration after perturbation of the polymer system. The disturbance is assumed to impose a linear change of the depropagation rate constant with respect to time. It is more realistic physically than the assumption of a sudden change of rate constants. Also discussed in the paper is the application of the solution to cases which have a nonlinear change of the rate constant.

ISSN:0449-296X    

DOI:10.1002/pol.1972.170101009

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractThe syntheses of four new monomers and two new polyaromatic pyrazines are described. The monomers; bis‐p,p′‐(octanoyl)diphenyl ether (Ia), bis‐p,p′‐(hexadecanoyl)diphenyl ether (Ib), bis‐p,p′‐(α‐bromooctanoyl)diphenyl ether (IIa), and bis‐p,p′‐(α‐bromohexadecanoyl)diphenyl ether (IIb), were produced by Friedel‐Crafts acylation of diphenyl ether with the corresponding acyl chloride and subsequent α‐bromination. Prepolymers were synthesized by the condensation of (IIa) and (IIb) with ammonia inN,N‐dimethylformamide (DMF), and polymers were prepared by subsequent melt condensation of the prepolymer to produce poly[2,5‐(oxydiphenylene)‐3,6‐(dihexyl)pyrazine] (IIIa), and poly[2,5‐(oxydiphenylene)‐3,6‐(ditetradecyl)pyrazine](IIIb). Polymer IIIa was thermally (stable at>400°C while polymer IIIb was a tacky substance). The inherent viscosity of IIIa produced by 12 hr of melt condensation was 0.30 dl/g in formic acid. Additional heating in excess of 24 hr gave a slightly soluble polymer. The inherent viscosity of IIIb produced by 40 hr

ISSN:0449-296X    

DOI:10.1002/pol.1972.170101010

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY