Heterophase block copolymers

Kotaka, T., and Watanabe, H., Rheological and morphological properties of heterophase block copolymer solutions, in Current Topics in Polymer Science, Vol. II, Ottenbrite, R. M. Utracki, L. A., and Inoue, S.,Eds., Hanser-Verlag, Munich, 1987. 

Bigg, D. M. Thermal Conductivity of Heterophase Polymer Compositions.Vol. 119, pp. 1-30. Binder, K. Phase Transitions in Polymer Blends and Block Copolymer Melts Some Recent Developments. Vol. 112, pp. 115-134. 

In the case of inverse systems, hydrophilic monomers such as hydroxyethyl acrylate, acrylamide, and acrylic acid were miniemulsified in non-polar media, e.g., cyclohexane or hexadecane [45,46]. Rather small and narrow distributed latexes in a size range between 50 nmsynthesized with nonionic amphiphilic block copolymers. Depending on the system, the surfactant loads can be as low as 1.5 wt% per monomer, which is very low for an inverse heterophase polymerization reaction and clearly underlines the advantages of the miniemulsion technique. 

The authors are indebted to the Shell Development Co. for supplying the tri-block copolymers, TR-41-1647, TR-41-1648 and TR-41-1649. H. Kawai and M. Shen also wish to thank the Japan Society for Promotion of Science, the Dreyfus Foundation, and the Office of Naval Research for support which has enabled them to cooperate in their research projects on heterophase systems, including this chapter. Finally, thanks are owed to the Editor of Rubber Chemistry Technology for permission to reproduce Figures 2 and 6-11 from the original paper (29). 

Dq Self-diffusion constant of unmodified homopolymer D, Pre-exponential factor for craze growth by interface convolution Dj Pre-exponential factor for craze growth rate by heterophase cavitation E Young s modulus of block copolymer composite... 

Craze flow stress of PS with sorbed diluent at the solubility limit Cavitation strength of heterophase domain in block copolymer 6 Ratio of des( nding to the ascending slopes of the traction displacement law locally accompanying craze matter production, as defined in Ref. 

Block copolymers with polypeptide segments were occasionally used to stabilise oil-in-water emulsions or as emulsifiers in heterophase polymerisation processes. 

An attempt has been made (56) to understand the role of the structural factor when MAH was grafted to heterophase PP. The latter was a mixture of highly crystalline homopolypropylene, which made the matrix and copolymers dispersed in the PP matrix similar to rubber particles. During fractionation of the heterophase PP, three fractions were separated PP ( 50 wt%), EPR with irregular distribution of ethylene units ( 43 wt%), and ethylene-propylene block copolymer (EPM) ( 2 wt%). Peroxide initiators were DTBP (di-tert-butyl peroxide), S =... 

ICP = blends of isotactic propylene homopolymer with ethylene-propylene rubber. These materials are commonly called "impact copolymers," "heterophasic copolymers," or, incorrectly, "block copolymers." These are typically prepared during the polymerization process using a series of reactors. L = low rubber (less than about 15% rubber by weight typically witli an ethylene content of less than about 10%). H = high rubber content blends (greater than about 15% rubber by weight typically with an ethylene content of at least 7%). 

Impact copolymers (heterophasic copolymers), also known as block copolymers, are made in a two reactor system where the homopolymer matrix is made in the first reactor and then transferred to the second reactor where ethylene and propylene are polymerized to create ethylene propylene rubber (EPR) in the form of microscopic nodules dispersed in the homopolymer matrix phase. These nodules impart impact resistance both at ambient and cold temperatures to the compound. This type has intermediate stiffness and tensile strength and is quite cloudy. In general, the more ethylene monomer added, the greater the impact resistance with correspondingly lower stiffness and tensile strength. 

Keywords 2,2 -azobisisobutyronitrile block copolymers heterophase polymerization microwave heating particle nucleation... 

Aqueous heterophase polymerization is not only an industrially important radical polymerization technique but also scientifically challenging as well as offering unique possibilities for basic scientific studies. All advantages as well as all kinetic peculiarities of heterophase polymerizations are grounded on the heterogeneous nature of the reaction system creating at least two, extremely different reaction loci. The potential ability to produce amphiphilic block copolymers via a simple radical polymerization mechanism under such circumstances was recognized already 1952.[y... 

Guan, Z. and DeSimone, J. M. (1994) Fluorocarbon-Based Heterophase Polymeric Materials. 1. Block Copolymer Surfactants for Carbon Dioxide Applications, Macromolecules 27, 5527-5532. 

Fig. 2. Family tree of polymer dispersions. The time axis in this graph denotes the time when the different kinds of pol3mier dispersions came to awareness of mankind starting with natural latex and ending with recent developments in polymeric colloidal complexes. Some important historic milestones are the following the biosynthesis of natural rubber in plants takes place on earth since millions of years, the first heterophase polymerization was mentioned in a patent filed in 1912 (21), the first process description to make an artificial latex was published in 1923 (40), and the first block copolymer dispersion made by heterophase polymerization was described in 1952 (41).

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