Thermosetting semi-interpenetrating networks

B) Thermoset-thermoplastic blends and semi-interpenetrating networks (Semi-IPN)... 

PI (thermoplastic/ thermoset and semi-interpenetrating networks) 6.0 - 60.0 92Jan... 

The idea behind semi-interpenetrating networks (semi-lPN s) is to combine the processabiity of thermoplastics with the high temperature performance of crosslinked thermosetting materials. Such mixtures should possess the desirable features of both types of materials. The majority of semi-IPN s contain continuous phases and the components are immiscible at the molecular level. 

Hybrid versions of silicone-thermoplastic semi-IPNs have been developed (19). A hybrid interpenetrating network is one in which the cross-linked network is formed by the reaction of two polymers with structurally distinct backbones. Hydride-functionalized siloxanes can be reacted with organic polymers with pendant unsaturated groups such as polybutadienes (5) in the presence of platinum catalysts. Compared with the polysiloxane semi-IPNs discussed earlier, the hydride IPNs tend to maintain mechanical and morphologically derived properties, whereas properties associated with siloxanes are diminished. The probable importance of this technology is in cost-effective ways to induce thermoset characteristics in thermoplastic elastomers. 

Polysulfones have been made from acetylene-terminated sulfone monomers (Fig. 3.51), and cured graphite-fiber laminates have shown Tg = 300°C and good mechanical properties at 170°C before and after heat and humid aging. Semi-interpenetrating polymer networks with linear thermoplastic polysulfones showed promise of combining the heat deflection temperature and solvent-resistance of the thermoset polymer with the impact resistance of the thermoplastic. 

Polymer, interpenetrating network IPN is a branch of blend technology it combines two plastics into a stable interpenetrating network. There are all types of blends, such as synergistic types, to meet all types of performance requirements. In true IPN s, each polymer is cross-linked to itself, but not to the other, and two polymer networks interpenetrate each other these become thermoset (TS) plastics. In semi-IPN, only one polymer is cross-linked the other is linear and by itself would be a thermoplastic (TP) these lend themselves to TP processing techniques. The rigidity of IPN structures increases mechanical and other properties such as chemical... 

Semi-IPNs were prepared by the sol-gel technique through in situ polymerization of BMI in thermoplastic polyetherimide (PEI) as well as in polysulfone (PSF) (Kurdi and Kumar 2006). Structure and properties of semi-IPN membranes could be varied by controlling the thermoset BMI microdomain size interpenetrating within a thermoplastic polymer network. The size of this microdomain depended on the polymerization time of BMI and on the degree of thermoset/thermoplastic phase separation. These semi-IPN membranes showed an improved Tg but a decrease in their thermal stability and could be used for Oj-emiched-air applications where high selectivity is not required. At ambient temperature, it was possible to increase the permeance of semi-IPN membranes. 

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