Fractography of polymers

The fractography of polymers has been based on metallurgical experiences. (References 1 and 2 and the reported review therein are documents for these roots.) Especially the anals cal way of how to observe, describe, measure, and interpret a fracture surface could be adapted for and applied to polymers (3-13). However, it is necessary to take into accoimt the more complex deformation behavior of polymers. 

K.Fridrich and J.Karger-Kocsis, Fractography of Unfilled and Short Fibre Filled Semicrystalline Thermoplastics, in Fractography of Polymers and Composites, (Ed.A.C.Roulin-Moloney), Elsevier Applied Science Publishers, Barking, U.K., 1989, 437. 

Roulin-Moloney A C 1989 Fractography and failure mechanisms of polymers and composites (London Elsevier)... 

Denison, P., Jones, F.R., Brown, A., Humphrey. P. and Paul, A.J. (1988b). Scanning SIMS fractography of CFRP. In Interfaces in Polymer. Ceramic and Metal Matrix Composites (H. Ishida ed.), Elsevier. New York, pp. 239-248. 

Friedrich, K. and Karger-Kocsis, J. (1989). Unfilled and short fiber reinforced semi-crystalline thermoplastics. In Fractography and Failure Mechanisms of Polymers and Composites, (A.C. Roulin-Moloney ed.), Elsevier Appl. Science, London, pp. 437-494. 

Fagan, A. F., Bell, J. M., and Briggs, G. A. D. (1989). Acoustic microscopy of polymers and polymer composites. In Fractography and failure mechanisms of polymers and composites (ed. A. C. Roulin-Moloney), pp. 213-30. Elsevier Applied Science, London. [204]... 

A novel, relatively simple method for analytical pyrolysis of polymers is pyrolysis-fractography (Py-F) [18]. In this method, the pyrolysate generated when a polymer is instantaneously pyrolyzed at 600° C is introduced together with the carrier gas into a short length deactivated stainless steel capillary tube. This tube is placed in the oven of a gas chromatograph. The oven temperature is linearly raised, so that the pyrolysate is fractionated based on the distillation temperature, and a fractogram is obtained using a mass spectrometer or a flame ionization detector. 

This article is concerned principally with the utilization of polymers as items of trace evidence. The small size of samples usually available makes their examination nonroutine. Methods such as tensile testing, fractography, and burning are rarely conducted on a microscale in forensic investigations. A significant part of the forensic examination of polymeric snbstances is concerned with factors other than those derived from the polsrmer itself. Criminalistics is distinguished from the other sciences by its imique attempt to individualize as opposed to most natural sciences, where the emphasis is on generalization and the establishment of laws that can be imiversally applied. 

An example for the use of fractography for evaluating the phase morphology of polymer blends is shown in Figure 17. The specimen, a PP with 30-wt% of a metallocene polymerized polyethylene (mPE), was fi actured at —30°C. Afterwards the mPE-phase was dissolved in xylene, so that the resulting holes visualize the distribution of mPE in the PP matrix. The micrograph shows a... 

A. C. Roulin-Moloney, Fractography and Failure Mechanisms of Polymers and Composites, Elsevier Science Publishers, London, 1989. 

Pomies F, Carlsson LA, Gillespie JW Jr (1995) Marine environmental effects on polymer matrix composites. In Martin RH (ed) Composite materials fatigue and fracture, vol 5, ASTM STP 1230. American Society for Testing and Materials, Philadelphia, pp 28-303 Price JN (1989) Stress corrosion cracking in glass reinforced composites. In Roulin-Moloney AC (ed) Fractography and failure mechanisms of polymers and composites. Elsevier Applied Science, New York, pp 495-531... 

Extensive discussions of polymer fractography, including crazing, are found in basic texts (e.g., by Kausch [488,489] and Liebowitz [490]). In this section, discussion will focus on the techniques required to prepare fractured or deformed specimens for microscope observation. It is quite obvious that the preparation methods all involve damage processes. 

Wu [234] reviewed the basic principles of optical and electron microscopes and their applications to characterization and investigation of polymer toughening mechanisms. Multiphase polymers are prepared for SEM by methods such as fractography, etching, and extraction and for OM and TEM by thin sectioning methods. The dispersed phase in a... 

Goolsby R, Chatterjee A. Notch sensitivity and fractography of polyolefins. Polym Eng Sci 1983 23(3) 117-24. 

An extensive discussion of polymer fractography can be found in other studies (Kausch 1978, 1983 Plummer 2007). There are three different sources for fractured specimens (1) deformation of the sample and fracture after testing in standard mechanical testing devices, such as tension, compression, or bending tests, impact test, etc. (2) in situ deformation and fracture of microsamples by special miniature testing devices during observation in the microscope ... 

Fractography. Fracture surfaces provide information about microstructure and the mechanism of failure. Generally, however, the commercial, 2-phase acrylic polymers used for dental applications form surfaces which are too un-... 

Table 4.4 includes functional groups and polymers and their respective etchants. Chemical etching, such as with solvents and acids, and ion and plasma etching are conducted in order to reveal selectively structures in polymers that may not be observed directly. In all these methods, interpretation of the structures formed can be more difficult than specimen preparation. Accordingly, the etching methods are best used to complement other methods, such as microtomy, fractography and staining. Controls are essential to any experiment of this type, but, with care, the structures of semicrystalline polymers and polymer blends may be observed. 

SE images of a matched pair of tensile failed PET fibers are shown in Fig. 4.30. A classical slow fracture zone, or mirror, is seen adjacent to the locus of failure. A typical ridged or hackle morphology is exhibited as the crack propagates and accelerates away from the failure locus. In this study, an inorganic residue from the polymer process was shown to be the cause of failure [295]. The value of such a fractography is that... 

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