Semiaromatic polyamides

Figure 4.65 shows two examples of half-lives, which are not representative of all semiaromatic polyamides. 

Shrinkage, coefficient of thermal expansion and creep are rather low, the more so as semiaromatic polyamides are very often reinforced. The absorption and swelling by exposure to moisture are slow and low (see Figure 4.66). 

Chemical resistance is generally slightly better than for polyamides 6 and 66, but semiaromatic polyamides are attacked by organic and mineral acids, oxidizing agents, concentrated bases, phenols, formaldehyde. 

The introduction of nanoceramics in thermoplastics or thermosets seems to be a promising route to improving mechanical moduli, particularly of elastic matrices. The macroscopic properties are governed by the nature of polymer-nanoparticle interactions. In this chapter, specific attention will be paid to nanocomposites of polyamide (PA) with HAp. Considering their attractive viscoelastic properties, semiaromatic polyamides (e.g., PA-llTlO) have been chosen as the matrix [Choe et al., 1999]. Recently, several publications have been devoted to one-dimensional nanostructures with high-aspect-ratio particles. Promising data have been obtained for the polymer/nanowire-nanotube nanocomposites. 

Polyamide 9T (PA9T) is a semiaromatic polyamide commercialized under the name of Genestar by Kuraray Co [6]. PA9T uses a long, flexible aliphatic diamine consisting of nine methylene groups in a sequence as part of the polyamide backbone. This melt processible polyamide exhibits a Tg of 125°C and of 300°C. The structure of PA9T appears in Fig. 1.6. 

FIGURE 1.9 (a) Fully aromatic polyamide based on TMC and MPD. (b) Semiaromatic polyamide based on TMC and PIP. (Data from A.G. Fane et al., Membrane technology for water Microfiltration, ultrafiltration, nanofiltration, and reverse osmosis. In P. Wilderer, ed.. Treatise on Water Science, Academic Press, Oxford, 2011, pp. 301-335.)... 

FIGURE 1.10 (a) Basic mechanism for the preparation of TFC membranes by IP. (b) Reaction between piperazine (PIP) and trimesoyl chloride (TMC) for preparing semiaromatic polyamide layer. (Data from H. Strathmami et aL, Basic Aspects in Polymeric Membrane Preparation, In E. Driob and L. Giomo, eds.. Comprehensive Membrane Science and Engineering, vol. 1 Basic Aspects of Membrane Science and Engineering. Elsevier, Amsterdam, the Netherlands, 2010, pp. 91-112.)... 

A number of high melting poiat semiaromatic nylons, iatroduced ia the 1990s, have lower moisture absorption and iacreased stiffness and strength. Apart from nylon-6 /6,T (copolymer of 6 and 6,T), the exact stmcture of these is usually proprietary and they are identified by trade names. Examples iaclude Zytel HTN (Du Pont) Amodel, referred to as polyphthalamide or PPA (Amoco) and Aden (Mitsui Petrochemical). Properties for polyphthalamide are given ia Table 2. A polyphthalamide has been defined by ASTM as "a polyamide ia which the residues of terephthaUc acid or isophthahc acid or a combination of the two comprise at least 60 molar percent of the dicarboxyhc acid portion of the repeating stmctural units ia the polymer chain" (18). 

Table 2.1 Principal commercial representatives of linear, semiaromatic, and aromatic polyamides.

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