Hard segments physical blending

Model hard segments of MDI-DPG at a 0.9/1.0 mole ratio gave a Tg of 85°C which was used in the physical blending study, while at a 1.0/1.0 mole ratio gave a Tg of 110°C. No melting endotherms were observed so these hard segments are described as glassy-amorphous.. ... 

Figure 1. DSC results of physical blending of hard and soft segments. Key If, MDl-DPG/MDl-Poly G (55-56 J O, 0, and A, MDl-DPG/MDl-Poly G...

PEBAs are plasticizer-free TPEs. The soft segment is the polyether and the hard segment is the polyamide (nylon). They are easy to process by injection molding and profile or film extrusion. Often they can be easily melt-blended with other polymers, and many compounders will provide custom products by doing this. Their chemistry allows them to achieve a wide range of physical and mechanical properties by varying the monomeric block types and ratios. 

Typical dynamic mechanical properties of the blends are given for 2TPU4 (Figure 24) where the tan 8 peak decreases and the rubbery state modulus increases smoothly with increasing amount of TPU. The former confirms the miscibility and the latter implies that hard segment domains do play the role of physical crosslinks or reinforcing filler in the rubbery state. With the rise in hard segment content, the increase in the rubbery state modulus was more pronounced. Similar results were also obtained for TPUs from PCL 2000. 

The base polymer used for the stody was PEBA. It is a thermoplastic elastomer of hardness value 72 on Shore D. It consists of two domains -hard segment due to the presence of polyamide, and soft segment due to polyether. Changing the proportion of two domains it is possible to various hardness grades of PEBA. Its excellent cherrrical, mechanical, and physical properties and biocompatibility makes it one of the most widely used materials for biomedical devices. PEBA can be easily melt blended with many polymers. 

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