Examination of Polymer Surfaces and Defects

The book covers not only instrumentation for the determination of metals, non metals, functional groups, polymer structural analysis and end-groups in the main types of polymers now in use commercially, but also the analysis of minor non-polymeric components of the polymer formulation, whether they be deliberately added, such as processing additives, or whether they occur adventitiously, such as residual volatiles and monomers and water. Fingerprinting techniques for the rapid identification of polymers and methods for the examination of polymer surfaces and polymer defects are also discussed. 

FT-IR microscopy has been applied to the examination of polymer films, polymer laminates, and polymeric printing inks or coatings on metal cans. It has been used to identify defects, imperfections, and inclusions in films and laminates. Inclusions not on the surface can be revealed for analysis by cutting across sections with a microtome. Polarised FT-IR microscopy studies have been performed, using a grid wire polariser, on... 

Fracture mechanics considerations, summarized for polymers by Kausch [40,41], permit determination of the effect of defects on the fracture stress, or tensile strength, of bulk polymers and polymer fibers. It is important that such detailed study be performed on the original or primary fracture surfaces, which are the only surfaces which relate to the tensile stress. This is generally done by examining both failure surfaces to ensure that they are a matched pair. An example of matched, primary fracture surfaces was shown earlier (Fig. 4.29). In that case, a definite defect site was observed in the brittle fracture surface. Such assessment provides the structure-property information needed to modify the process and produce fibers with higher strengths. 

Case studies are used to demonstrate failures in polymer products. Aspects of defect analysis considered include the occurrence of recrystallisation, surface contamination, frozen-in strain, mixing efficiency, and formulation problems. Case histories examined include those involving pipes and fittings, storage tanks, and medical products. 383 refs. 

Giniewicz [17] has studied the effects of mixing procedure on filler distribution for the manufacture of 0-3 composites. The filler was added to the polymer phase and mixed by hand with a laboratory spatula until it appeared to be well mixed. When the composites were formed, a careful examination showed several defects, most of which were introduced during the initial mixing and dispersion stages of the compounding process. The key problems were inadequate distribution of the polymer, poor adhesion between component surfaces and air entrapment. 

In this study, the effects of polymer part characteristics such as surface defects and contamination on SDT are examined for polycarbonate (PC), a laser-transparent amorphous polymer. The measured SDT can be used as a reference when selecting the laser power and speed in LTW process development for PC. Some suggestions on how to maximize a polymer s SDT are also provided. 

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