Poly fracture toughness

Recently siloxane-imide copolymers have received specific attention due to various unique properties displayed by these materials which include fracture toughness, enhanced adhesion, improved dielectric properties, increased solubility, and excellent atomic oxygen resistance 1S3). The first report on the synthesis of poly(siloxane-imides) appeared in 1966, where PMDA (pyromellitic dianhydride) was reacted with an amine-terminated siloxane dimer and subsequently imidized 166>. Two years later, Greber 167) reported the synthesis of a series of poly(siloxane-imide) and poly(siloxane-ester-imide) copolymers using different siloxane backbones. However no physical characterization data were reported. 

Hill, R. G., Wilson, A. D. Warrens, C. P. (1989). The influence of poly(acrylic acid) molecular weight on the fracture toughness of glass-ionomer cements. Journal of Materials Science, 24, 363-71. 

Hing P. and Groves G.W. (1972). The strength and fracture toughness of poly-crystalline magnesium oxide containing metallic particles and fibers. J. Mater. Sci. 7, 427-434. 

Karger-Kocsis J. and Friedrich K. (1987). Microstructural details and the effect of testing conditions on the fracture toughness of injection molded poly(phenylene sulphide). J. Mater. Sci. 22, 947-961. 

Research Focus Enhancing the fracture toughness of poly(L-lactide-co-glycolide) by introducing phase separation using y-caprolactone. 

Two terpolymers of poly(L-lactide-co-glycolide) were prepared in this application that had enhanced fracture toughness by incorporating -y-caprolactone by ring-opening polymerization using either stannous octoate or stannous trifluoromethane sulfonate as the catalyst. The products synthesized by this method were ... 

Within the past several years, improvements in the toughening of high-temperature epoxies and other reactive thermosets, such as cyanate esters and bismaleimides, have been accomplished through the incorporation of engineering thermoplastics. Additions of poly(arylene ether ketone) or PEK and poly(aryl ether sulfone) or PES have been found to improve fracture toughness. Direct addition of these thermoplastics generally improves fracture toughness but results in decreased tensile properties and reduced chemical resistance. 

Jia etal. 1999 (23) MWCNT CVD Untreated tubes Treated tubes In situ polymerization Improved In situ polymerization CNT Loading levels 1 to 10 wt% Tensile Strength, fracture toughness and hardness increased with CNT loading from 0 to 7 wt% using treated tubes and improved method Tensile Strength Untreated tubes Treated tubes In situ poly. Improved In situ poly. Wt% MPa Wt% MPa 0 54.9 3 66.8 1 21.2 5,7 71.7 3 20.3 10 47.2 FTIR and SEM studies revealed CNT participation in PMMA polymerization and presence of a strong interface between CNTs and PMMA ... 

Interestingly, the ductile-brittle transition observed for the MIM system provided an opportunity to assess the material fracture toughness, which was not possible using classical fracture mechanics tests due to the intrinsic brittleness of the MIM system. The measurement of the critical crack length, Lc, in the contact plane at the onset of brittle propagation allows estimation of a fracture toughness K C = a x+JnLc in the order of 0.85 MPa m1/2, i.e. much less than that of a poly(methylmethacrylate) homopolymer (1.20 MPa m1/2). 

Fracture toughness, essential work of fracture, plane stress, viscoelasticity, thin films, poly(ethylene-terephthalate). 

Fig. 47. Fracture toughness gc (A) at high copolymer coverage (saturation values), and fraction of deuterium on the PS side of the interface after fracture ( ) at low copolymer coverage, as a function of copolymer composition/, a Poly(styrene-d8-co-4-hydroxystyrene) b poly(styrene-d8-co-4-vinyl-AT-ethylbenzamide) and c poly(styrene-d8-co-4-vinylbenza-mide). Data from [77]...

A similar study was undertaken by Beck Tan et al. on the adhesion between poly(styrene-r-sulfonated styrene) and poly(2-vinylpyridine). In this case, however, the variable was the mole fraction of sulfonated styrene in the random copolymer [95]. The results of the maximum fracture toughness Qc vs. mole fraction of functional groups are plotted in Fig. 51. The reinforcement shows a very sharp maximum with degree of functionalization consistent with the multiple stitching giving rise to short loops poorly entangled with the homopolymer however, in this case as well, the bulk properties of PS are modified by the presence of the styrenesulfonic acid and this could contribute to the decrease in Qc at high levels of functionalization. 

Fig. 51. Fracture toughness of interfaces between poly(2-vinylpyridine) and poly(styrene) containing a small amount of sulfonated PS. Qc is plotted as a function of the mole fraction of PS which is functionalized. Data from [95]...

As can be seen in Fig. 10 [29], the fracture toughness in poly crystalline tetragonal zirconia (TZP) and partially-stabilized zirconia (PSZ) appears to reach a maximum. This indicates a transition from flaw-size control of strength to transformation-limited strength. Ranges of fracture toughness values for zirconia composites are given by Richerson [38]. 

Section 19.S.1.2), and reported increases in toughness comparable to those achieved with CTBN. A further, but inconclusive, study compared pre-formed poly(n-butyl aciylate)-based particles made by emulsion and by suspension polymerization [97]. Dispersion polymerization in an epoxy resin has been used to give directly dispersions of acrylic rubber particles in the epoxy for subsequent use in toughening epoxy resins [98]. Core-shell toughening particles comprising 70 wt% of CFOSslinked polybutadiene cores, with a grafted functionalized shell have been claimed [99] to improve the fracture toughness of a methylene dianiline cured epoxy resin by a factor of 10. 

The literature published on fracture mechanics testing of FRPs in the last 40 years comprises a large database on delamination resistance or fracture toughness of different types of FRPs. An early review [51] compiled the data available at that time. Selected data from quasi-static mode I and mode II tests on FRPs were compared by O Brien [52], and quasi-static mode I test data from carbon—fibre epoxy and poly-ether-ether-ketone (PEEK) by Brunner [53]. Mechanical properties of FRP composites are compiled in the Composite Materials Handbook version F (2002) [9—11], but this does not comprise fracture mechanics data. Hence, there is no comprehensive and up-to-date database on the available data or literature. 

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