Part Three Mechanical Properties

Denning s three papers in the late 1960s (a.2-a.4) reviewed the development of closed-cell polyolefin foams, and their mechanical properties. Some of his predictions on materials development turned out to be true. In Part I he explains that non-crosslinked polyethylene (PE) foams have inferior creep properties to crosslinked foams this appeared to be the tensile creep of the melt, rather than compressive creep of the... 

After an overview over the experimental techniques and results from the literature (Sect. 7.2) and some words about technical aspects and our experience concerning problems with some materials (Sect. 7.3), the experiments of the authors can be outlined as follows first, measurements of ohmic and capacitive currents in the contact mode are described (Sect. 7.4), followed by a description of some surface charge measurements in the non-contact mode (Sect. 7.5). The chapter closes with some experiments to probe electro-mechanical properties by the use of piezo response microscopy (Sect. 7.6) with its own brief literature overview. All three experimental parts are opened by a short introduction to the SFM techniques implemented in our lab. 

The mechanical properties of polymers are controlled by the elastic parameters the three moduli and the Poisson ratio these four parameters are theoretically interrelated. If two of them are known, the other two can be calculated. The moduli are also related to the different sound velocities. Since the latter are again correlated with additive molar functions (the molar elastic wave velocity functions, to be treated in Chap. 14), the elastic part of the mechanical properties can be estimated or predicted by means of the additive group contribution technique. 

Part VI Polymer properties as an integral concept. Chapter 24, on processing properties, is extended slightly. Chapter 25, on mechanical product properties, remained almost unchanged. The three subchapters of Chapter 26, on environmental product properties, are extended quite greatly. Chapter 27 on examples of end use properties remained unchanged. 

Sequential EBM is a special multi-material technique used for the production of special designed products. The different plastics are chosen typically to contribute complementary mechanical properties and are present in distinct sequential zones in the finished part. Normally two materials are used but three or more are also used. Separate external ram accumulators for each material serve the die head. These are operated sequentially, typically in A-B-A sequence, to produce a parison with three distinct material zones in axial succession. The parison is subsequently BM by normal techniques. 

In block copolymers [8, ], long segments of different homopolymers are covalently bonded to each other. A large part of synthesized compounds are di-block copolymers, which consist only of two blocks, one of monomers A and one of monomers B. Tri- and multi-block assemblies of two types of homopolymer segments can be prepared. Systems with three types of blocks are also of interest, since in ternary systems the mechanical properties and the material functionality may be tuned separately. 

Three-Dimensional Representation. Whatever the configuration of the specimen, an infinite number of tensile curves can be obtained by changing either temperature or tensile extension rate. Figure 2, for one-part chemically curved silicone, and Figure 3, for two-part polysulfide model specimens, show a few examples that are obtained by varying the test conditions. The question arises, which of the tensile curves defines the mechanical properties of a sealant unambiguously ... 

Man-made composites fall into three broad classes, depending on whether the main part of the composite, the matrix, is a polymer, a metal or a ceramic. Often, but not always, the composite combines materials from two classes, as in glass-fibre-reinforced plastics. However, the most widely used composite material, concrete, is a ceramic -ceramic composite. The most important classes of artificial composite are described below. The mechanical properties of composites are discussed in Section 10.4. Biological composites are very varied and will not be considered here. 

---