Glass transition temperature consolidant

The model PBZT/ABPBI molecular composite system is limited since the rod and the matrix do not possess glass transition temperatures for subsequent post form consolidation. In an effort to improve the processability for molecular composites, thermoplastics were used as the host matrix. Processing from acidic solvents requires the thermoplastic host to be soluble and stable in meth-anesulfonic add. Thermoplastic matrices were investigated including both amorphous and semicrystalline nylons [71,72], polyphenylquinoxaline (PPQ) [73] and polyetheretherketone (PEEK) [74], Table 5 shows the mechanical properties obtained for various processed PBZT thermoplastic molecular composite systems. As an example, the PBZT/Nylon systems showed 50-300% improvement over uniaxially aligned chopped fiber composite of comparable compositions. However, the thermally-induced phase separation during consol-... 

More recently [79], a carboxy-terminated PBZT ([r ] = 4.8 dL/g) was reacted with m-phenoxybenzoic acid via a Friedel Craft procedure in a meth-anesulfonic acid/P2Os mixture. This provided an ABA block copolymer in which the outer blocks (A) are composed of flexible coil polyetherketone (PEK) and a center block (B) which contains the rigid-rod PBZT. Thermomechanical analysis showed that 20 PBZT/80 PEK and 10 PBZT/90 PEK compositions exhibited glass transition temperatures of 157 °C and 135°C respectively. Consolidation studies have not been investigated to date. 

Retained solvents may act as plasticizers (i.e., unless the solvent evaporates completely, the deposited resin may not have the same properties as the original solid in its pure state). Retained solvent lowers the glass-transition temperature. If the Tg of the mixture is at or below room temperature, rubbery behavior will result, and consolidant effectiveness will be reduced. Acryloid B72 seemed to retain solvent in films cast from acetone and toluene solutions and then air-dried (12). Further study showed that Acryloid B72 may retain measurable amounts of solvent even after 30 days at room temperature (16, 17). Results are shown in Table II. 

The glass transition temperature (Tg) of a polymer is important in choosing a consolidant, adhesive or coating, and is an accurate indication of the softness of... 

Most consolidation is irreversible, so only materials of proven stability should be used. The minimum amount of consolidant necessary should be incorporated in an object. It is wise to assume that an object weak enough to warraut consolidation is too weak to withstand attempts to remove the consolidant. Objects consolidated with products whose glass transition temperature is below ambient temperature are unlikely to be self-supporting. 

Blocking Blocking is the unwanted adhesion of two surfaces. Blocking can occur in books whose pages have been reinforced using a consolidant with too low a glass transition temperature. 

The sol-gel process is a versatile solution process for making ceramic and glass materials involving the transition of a system from a colloidal suspension (sol) into a solid phase (gel) ". The resulting porous gel can be chemically purified and consolidated at high temperatures. In the classical sol-gel process, the precursor (e.g. a metal enolate or a metal aUcoxide) is exposed to a series of hydrolysis and polymerization reactions to form... 

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