Toughness modifiers

Toughness, modifier, polyethylene terephthalate, core-shell, essential work of fracture... 

Per Perez, R. M., Sandler, J. K. W., Altstadt, V., Hoffmann, T., Pospiech, D., Ciesielski, M., Doring, M., Braun, U., Balabanovich, A. 1., Schartel, B. Novel phosphorus-modified polysul-fone as a combined flame retardant and toughness modifier for epoxy resins. Polymer 48 (2007) 778-790. 

Impact Modifiers. Notched impact strength and ductility can be improved with the incorporation of impact modifiers, which can also lower the brittle-ductile transition temperature and give much improved low temperature toughness. Impact modifiers are rubbers (often olefin copolymers) that are either modified or contain functional groups to make them more compatible with the nylon matrix. Dispersion of the rubber into small (micrometer size) particles is important in order to obtain effective toughening (19). Impact modifiers can be combined with other additives, such as glass fiber and minerals, in order to obtain a particular balance of stiffness and toughness. Modified acrylics, silicones, and polyurethanes have also been proposed as impact modifiers. 

PMMA with impact modifier particles to enhance fracture toughness, modifier particles up to some microns large with low interfacial strength ... 

Toughness modified EP resin with amine curing agent 720-860 100-110 120-130 2,800 9.0-12.0... 

Introducing phosphorus-containing groups into the structure of polysulfone (either into backbone or main chain) the new modified polymers display high thermal stability with inherent flame retardant quality and could also be used as high temperature matrix resins and toughness modifiers in curable high performance epoxy resins. 

Summing up the above results the author would claim that microparticles are far more efficient toughness modifiers than nanoparticles. The nanoeffects reported in numerous works should be linked with changes of the crosslink density in the interphase. The related changes are likely caused by the selective absorption of a given component of the resin by the nanoparticles. Note that this happens also when the nanoparticles are available in masterbatch form. Unfortunately, the related aspects e.g., cure kinetics, morphology development) have not yet been addressed by systematic studies. Nevertheless, platy fillers, present in both micro- and nanoscale at the same time, may be better toughener than spherical or fibrous nanofillers. Func-... 

Y. C. Gu et al.[2] used the POE as the toughness modifier and clay as the stiffness enhancer to study their effects on the toughness of PP. Results showed that blends of clay and POE could increase the toughness of PP. R. H. McGirk and M. M. Hughes[3] have used POE to improve the toughness of clarified PP which is weak on impact performance. 

Miscellaneous chemicals are used to modify the final properties of rigid polyurethane foams. Eor example, halogenated materials are used for flammabihty reduction, diols may be added for toughness or flexibiUty, and terephthalate-based polyester polyols may be used for decreased flammabiUty and smoke generation. Measurements of flammabihty and smoke characteristics are made with laboratory tests and do not necessarily reflect the effects of foams in actual fire situations. 

Nickel—Iron. A large amount of nickel is used in alloy and stainless steels and in cast irons. Nickel is added to ferritic alloy steels to increase the hardenabihty and to modify ferrite and cementite properties and morphologies, and thus to improve the strength, toughness, and ductihty of the steel. In austenitic stainless steels, the nickel content is 7—35 wt %. Its primary roles are to stabilize the ductile austenite stmcture and to provide, in conjunction with chromium, good corrosion resistance. Nickel is added to cast irons to improve strength and toughness. 

Polypropylene polymers are typically modified with ethylene to obtain desirable properties for specific applications. Specifically, ethylene—propylene mbbers are introduced as a discrete phase in heterophasic copolymers to improve toughness and low temperature impact resistance (see Elastomers, ETHYLENE-PROPYLENE rubber). This is done by sequential polymerisation of homopolymer polypropylene and ethylene—propylene mbber in a multistage reactor process or by the extmsion compounding of ethylene—propylene mbber with a homopolymer. Addition of high density polyethylene, by polymerisation or compounding, is sometimes used to reduce stress whitening. In all cases, a superior balance of properties is obtained when the sise of the discrete mbber phase is approximately one micrometer. Examples of these polymers and their properties are shown in Table 2. Mineral fillers, such as talc or calcium carbonate, can be added to polypropylene to increase stiffness and high temperature properties, as shown in Table 3. 

Nylon. Nylons comprise a large family of polyamides with a variety of chemical compositions (234,286,287). They have excellent mechanical properties, as well as abrasion and chemical resistance. However, because of the need for improved performance, many commercial nylon resins are modified by additives so as to improve toughness, heat fabrication, stabiUty, flame retardancy, and other properties. 

Styrene-based plastics are used somewhat in blow mol ding but not as much as linear polyethylene and PVC. HIPS and ABS are used in specialty botdes, containers, and furniture parts. ABS is also used as one of the impact modifiers for PVC. Clear, tough bottles with good barrier properties are blow-molded from these formulations. 

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