Morphology, HIPS

Fig. 13.3 Stress-strain curves of homo-PS and three toughened blends containing particles having KRO-1 diblock morphology, HIPS particles, and particles with concentric-spherical-shell (CSS) morphology having the highest elastic compliance (from Argon et al. (1987) courtesy of Pergamon Press).

Rubber-Modified Copolymers. Acrylonitrile—butadiene—styrene polymers have become important commercial products since the mid-1950s. The development and properties of ABS polymers have been discussed in detail (76) (see Acrylonitrile polymers). ABS polymers, like HIPS, are two-phase systems in which the elastomer component is dispersed in the rigid SAN copolymer matrix. The electron photomicrographs in Figure 6 show the difference in morphology of mass vs emulsion ABS polymers. The differences in stmcture of the dispersed phases are primarily a result of differences in production processes, types of mbber used, and variation in mbber concentrations. 

The importance of the morphological aspects of the HIPS on their Izod impact strength and gloss has been... 

Figure 4 Correlation between morphology, impact strength, and gloss of HIPS.

Finally, for HIPS, control of the rubber morphology in its broadest sense requires control of the reactor environment as well as the chemistry of the grafting reaction. Poorly agitated regions, for instance, can lead to visual and physical defects in the product. 

Under the conditions of Example 5-23 the rubber phase of the end product shows an interesting micro-morphology. It consists of particles of 1-3 microns diameter into which polystyrene spheres with much lower diameters are dispersed. These included polystyrene spheres act as hard fillers and raise the elastic modulus of polybutadiene. As a consequence, HIPS with this micro-morphology has a higher impact resistance without loosing too much in stiffness and hardness. This special morphology can be visualized with transmission electron microscopy. A relevant TEM-picture obtained from a thin cut after straining with osmium tetroxide is shown in Sect. 2.3.4.14. 

HIPS resin with both a high gloss and a high impact strength have been produced using a special in situ polymerization process. A bimodal distribution of the elastomer particles and particular size range and morphology type is maintained (8). 

Materials. The materials used in the present study include both commercial and experimental grades of HIPS. A large number of materials covering a wide range of.rubbery phase morphologies were Investigated. 

Quantitative Image Analysis. A software package compatible with a HP personal computer (Model 9836) has been developed to assess the morphology of rubber particles in HIPS. The package is capable of analyzing the following information ... 

The preferred average particle size 1n HIPS was believed to be 0.8 ijm (J.). However, our current data indicate that a number average particle diameter of 1.05 urn and 0.5 -urn appear to be a preferred size for HIPS and rubber-toughened polypropylene (PP), respectively. The morphology of the rubbery phase in a toughened PP appears to be less complex, as evidenced in Figure 2 where the dark, also osmium-stained, phase is the styrene-butadiene rubber (SBR) particles. No PP occlusions were found in this material since it is a physical blend of SBR and PP. 

The sensitivity of the NDI technique has been fairly well demonstrated in several other samples as well. The image analysis data of 15 HIPS samples covering a wide variety of morphologies are summarized in Table 1. 

From this point on, the production steps for GPPS and HIPS are the same. The feed mixture is preheated (3) and continuously fed to the prepolymerizer (4) where the rubber morphology is established. 

Microgramms of HIPS morphology revealed without working out with the solvent vapour euid by means of above described method are given in figure 1,a,b. 

Side by aide with good visial qualitative observation of HIPS morphology obtained by means of above described method we applied the method used in me-teillography (14) and adapted for polymer material for optical microscopy (15) for getting distribution characteristics of rubber phase in the material and quantitative value of microstructure elements in electron microscope pictvires. 

It was foiind that for quantitative characteristics of HIPS morphology it is sufficient to make calculation according to 4 micrographs from the square of the surface 20x30, obtained from diffe-... 

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