摘要:

AbstractFurther kinetic studies on an anionic condensation polymerisation system have been carried out. It has been found that the model compound approach is valid for this system, particularly when dienes are used as monomers. The technique is useful, not only as an analytical tool but also as a means of preparing novel hydrocarbons and diols. The effect on the resulting copolymers of reducing the proportion of dihalide linking agent to monomer is discussed.

ISSN:0007-1641    

DOI:10.1002/pi.4980030301

出版商:John Wiley&Sons, Ltd    

年代:1971

数据来源: WILEY

摘要:

AbstractThe use of isocyanates in conjunction with polyesters and polyethers to produce polyurethanes is reviewed. The manufacturing conditions and hazards involved in the production of flexible and rigid foams are discussed. Surface coating applications and the production of elastomers are also reviewed.

ISSN:0007-1641    

DOI:10.1002/pi.4980030302

出版商:John Wiley&Sons, Ltd    

年代:1971

数据来源: WILEY

摘要:

AbstractThe organolithium‐initiated ring‐opening polymerisation of cyclic sulphides in polar, aprotic solvents was investigated. It was found that at −78°C thiiranes are attacked at the sulphur atom by the carbanion of the organolithium. This reaction is followed by elimination of an olefin and formation of a lithium alkylthiolate. The polymerisation reaction then involves bimolecular nucleophilic displacement at a carbon atom of the monomer by the propagating thiolate. Similarly, the initiation of the thietanes takes place through reaction of the carbanion at the sulphur atom. This is followed by ring‐opening and the formation of a new carbanion rather than the thiolate‐lithium species.The homopolymerisation of thiiranes and thietanes is essentially free of termination and chain‐transfer reactions. Thus, it is possible to prepare polythioethers of well‐defined molecular characteristics. In addition, block polymers of poly‐α‐methylstyrene‐poly(propylene sulphide)‐poly‐α‐methylstyrene were synthesised using phosgene to couple the active lithium thiolate chain ends. Molecular weight measurements and gel permeation chromatograms indicate that block polymers were prepared possessing predictable molecular weights and narrow molecular weight distributions. Several other block polymers involving cyclic sul

ISSN:0007-1641    

DOI:10.1002/pi.4980030303

出版商:John Wiley&Sons, Ltd    

年代:1971

数据来源: WILEY

摘要:

AbstractStudies of the polymerisation of butadiene in the presence of carbon tetrabromide in bulk and emulsion systems have shown that in both systems telomers are the first products of reaction. These consist of between 4–10 butadiene units with terminal allylic bromine and tribromomethyl groups. However, the fact that the telomers function as chain transfer agents through the terminal tribromomethyl group to produce diallylic bromine terminated low molecular weight polymers is unique to the emulsion system. Telomers prepared in bulk and emulsion have been isolated, characterised and the kinetics of their formation studied. Kinetic analysis has indicated that at low molecular weights an increase in polymerisation rate with increasing carbon tetrabromide concentration is predicted, but it is postulated that the telomer itself can initiate polymerisation. Telomers formed in either bulk or emulsion have been studied as chain transfer agents in the polymerisation of butadiene in emulsion at 60°C. Polymerisation rate decreases with increasing amount of chain transfer and it is postulated that degradative chain transfer plays a role in the polymerisation. A simplified kinetic scheme for retarded polymerisation has been developed to analyse the results. It is postulated that radical termination is by cross termination of growing polymer radicals with telomer radica

ISSN:0007-1641    

DOI:10.1002/pi.4980030304

出版商:John Wiley&Sons, Ltd    

年代:1971

数据来源: WILEY

摘要:

AbstractThe catalysis of the reaction between carboxylic acids and epoxides was examined in general and with special reference to the cure of carboxy‐terminated polybutadienes. It was established that the most active catalysts were the chromium chelates of salicylic acid or substituted salicylic acids. 3,5‐Diiso‐propylsalicylato chelates were studied in detail because of their solubility advantages. Reaction mechanisms are proposed which are in agreement with the kinetic data. A variety of applications were established for the new chelate catalyst. They include: synthesis of hydroxyalkyl carboxylic acids; efficient low‐temperature cure of liquid rubbers with possible regulation of chain extension and crosslinking; and use of the catalytic system for room‐temperature‐cured, midly acid adhesives of high strength and rubber‐modified

ISSN:0007-1641    

DOI:10.1002/pi.4980030305

出版商:John Wiley&Sons, Ltd    

年代:1971

数据来源: WILEY

摘要:

AbstractButadiene has been found to homopolymerise and copolymerise with other reactive vinyl monomers to yield unique liquid polymers which are terminated with reactive allylic hydroxyl groups. Through the use of an isocyanate cure reaction they offer a route to liquid castable general purpose elastomers, capable of reinforcement with various fillers and extension with a wide variety of low cost process oils.

ISSN:0007-1641    

DOI:10.1002/pi.4980030306

出版商:John Wiley&Sons, Ltd    

年代:1971

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980030307

出版商:John Wiley&Sons, Ltd    

年代:1971

数据来源: WILEY

摘要:

AbstractA simple method for determining sol‐gel transition temperatures in mechanically weak thermoreversible gels has been developed. Only 0–3 ml of gel is required and gels with a rigidity modulus as low as 100 dyne cm−2can be

ISSN:0007-1641    

DOI:10.1002/pi.4980030308

出版商:John Wiley&Sons, Ltd    

年代:1971

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980030309

出版商:John Wiley&Sons, Ltd    

年代:1971

数据来源: WILEY