Mechanical properties of SPS

The crystallization rate of SPS is much faster than that of IPS [10] however, a fast cooling below Tg does not allow SPS to fully crystallize, resulting in halfway crystallization. When SPS is injection molded, the degree of crystallinity and the morphology of SPS is greatly affected by the mold temperature [11], When neat SPS is molded at a high mold temperature, a well-developed lamellar structure is observed in the specimen and Xc is as high as about 50% across the whole cross section of the molded specimen, from the surface to 

As M becomes higher, the flexural strength increases for all mold temperatures (Fig. 13.8). Furthermore, the flexural strength gradually decreases with an increase of the mold temperature, which suggests that an increase of the crystallinity makes SPS more brittle. 

GPPS general purpose polystyrene PBT poly(butylene terephthalate) PA6 polyamide 6 PA66  

In Table 13.3, the mechanical properties of plastics are listed. SPS has a high melting point almost comparable to those of other plastics. An outstanding feature of SPS is that SPS has the lowest specific gravity and dielectric constant. The disadvantage of SPS is its brittleness the impact resistance is low compared to those of other engineering plastics. 

SPS shows a lower impact strength than APS. The study of the failure and deformation behavior of SPS revealed that the breakage of SPS occurs with a slow and controlled crack growth at a much lower energy level than APS. During the deformation, many craze bands appear in the AI, while no visual evidence of crazing was observed in SPS before the break [12], The critical stress intensity factor, A ic, and the fracture energy, Gu, of SPS are smaller than those of APS. These results show that SPS is more brittle compared with APS. 

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As we consider the mechanical properties of SPs, it is often useful to consider them in the context of entanglements, which are intermolecular interactions that transfer mechanical forces from one molecule to the next. In this chapter we use the term entanglement in a very general way, so that it includes topological entanglements (one polymer chain is physically wrapped around another), chemical entanglements (attractive intermolecular interactions between polymer chains), and surface adsorption (attractive intermolecular interactions between polymer chains and a particle surface, e.g., from a filler). The important, fundamental characteristic is that it is an interaction that allows a mechanical stress on one molecule to be distributed or transferred to another molecule with which it is entangled. 

The mechanical properties of SPs described in Sections 3.2-3.4 are, in general, suc-cessfiiUy interpreted, often quantitatively, in terms of thermal rate and equilibrium constants, but it is reasonable to expect that the underlying molecular behavior should be perturbed by the application of a mechanical stress. On the whole, the mechanical properties of supramolecular interactions are not well known, and their study constitutes a relatively new but burgeoning research area related to the field of SPs. 

SPS has heat resistance and chemical resistance in addition to the inherent characteristics of conventional polystyrene. Of significant interest, moreover, is that SPS is cost-competitive because it is synthesized from styrene monomer, a well established and widely available raw material. Although SPS has a brittle nature like APS and is not suitable for use alone for structural material, reinforcement with glass fiber or impact modification by elastomers improves the mechanical properties of SPS. 

Some typical physical and mechanical properties of sPS are reported below some reported values, e.g. the melting temperature [3], can vary slightly for... 

Abis et al. [32] also obtained evidence on compression molded blends of sPS/ SEBS of the occurrence of a phase compatibility between the components arising from the solubility of the polystyrene end-block of SEBS with the amorphous phase of sPS. In fact, although immiscible, a very fine dispersion and adhesion of the rubber particles is observed on SEM. However, contrary to the previous case, no improvement in the mechanical properties of sPS measured by tensile tests is observed, probably owing to the poorer performances of thermo-compressed samples than injection molded samples [38,39]. 

Using melt viscosity measurements, Lundberg et al. (107) showed that one could selectively plasticize either the ion-rich phase or the nonpolar hydrocarbon phase of SPS lonomers by varying the chemistry of the diluent used. Fitzgerald et al. (108) studied the effects of dioctyl phthalate (DOP) and glycerol on the dynamic mechanical properties of SPS lonomers. The addition of DOP lowered... 

The mechanical properties of SPS also depend on the molecular weight as well as on the crystallinity. Figure 13.7 shows the crystallinity of injection-molded SPS specimens for various average molecular weights, M . SPS was melted at 290 °C and was injection molded into test pieces at various mold temperatures. The Xc of the specimens became higher as the mold temperature was increased and leveled off at about 50%. On the other hand, a higher Xc was obtained for SPS with lower molecular weight at a fixed-mold temperature. 

The mechanical properties of SPS are affected by the ambient temperature. Figure 13.10 shows the flexural strength and the flexural modulus of... 

THE PERFORMANCE CAPABILITIES OF SPS 323 TABLE 15.1 Mechanical Properties of SPS and Other Glass-tilled Thermoplastics... 

Figure 20.8 Mechanical properties of SPS nanocomposites prepared by direct melt intercalation method (a) tensile strength, (b) tensile modulus, and (c) flexural modulus. Reprinted with permission from Reference 15. Copyright Wiley-VCH Verlag GmbH Co. KGaA.

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