Poly-m-xylylene adipamide

A rare example of a crystallisable aromatic polyamide used as a plastics material is poly-m-xylylene adipamide. 

As with the aliphatic polyamides, the heat deflection temperature (under 1.82 MPa load) of about 96°C is similar to the figure for the Tg. As a result there is little demand for unfilled polymer, and commercial polymers are normally filled. The inclusion of 30-50% glass fibre brings the heat deflection temperature under load into the range 217-231°C, which is very close to the crystalline melting point. This is in accord with the common observation that with many crystalline polymers the deflection temperature (1.82 MPa load) of unfilled material is close to the Tg and that of glass-filled material is close to the T.  

Commercial grades of polymer may contain, in addition to glass fibre, fire retardants, impact modifiers and particulate reinforcing fillers. Carbon fibre may be used as an alternative to glass fibre. 

In the absence of fire retardants the material has a limiting oxygen index of 27.5 and may bum slowly. Only some grades will achieve a UL 94 V-1 rating. The Underwriters Laboratories continuous use temperature index is also somewhat low and similar to the polyarylates with ratings of 135-140°C (electrical) and 105°C (mechanical with impact). Initial marketing has emphasised comparisons with the aliphatic nylons for the reasons given in the previous 

Because of their rigidity they are being looked at particularly as replacements for metals such as die-cast zinc alloys. Early uses to become established include portable stereo cassette recorders. Other applications include mowing machine components, electrical plugs, sockets, TV tuner blocks, pulleys, shafts and gears. 

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Typical values of rate coefficients reported [92] for polyamidation in m-cresol include 7.7 x 10 g mmole" sec" for the preparation of poly-(m-xylylene adipamide) and 4.2 (p-xylylene sebacamide) (Table 6). 

Poly(a,a,a, a -tetrafluoro-p-xylylene) Poly(m-xylylene adipamide)... 

Poly(m-phenylene isophthalamide) 660 to 700 Poly(m-xylylene adipamide) 518... 

B. De Roover, Etude des Melauges Constiues de Poly(m-xylylene Adipamide) et de Polypropylene Eonctionnalise Parlankydride maleique, PhD Thesis, Universite Catholique de Louvain, 1994. 

A crystalline, partially aromatic polyamide, poly-m-xylylene-adipamide, (also known as MXD-6) with repeat units of... 

A modified melt blending method has been developed for preparing exfoliated nanocomposites of poly(m-xylylene adipamide) with sodium montmoril-lonite [100]. There, an aqueous solution of sodium montmorillonite was blended with the polymer in a twin-screw extruder. This kind of mixing ensures that the silica nanoparticles are exfoliated in the polymer matrix through fixing the nanoparticles within the polymer matrix just as they are in water. Oxygen permeation data show enhanced the barrier properties of the nanocomposites. 

Wang Y, Jabarin SA. Novel preparation method for enhancing nanoparticle dispersion and barrier properties of poly(ethylene terephthalate) and poly (m-xylylene adipamide). J Appl Polym Sci2013 129(3) 1455-65. 

An example of a crystallizable aromatic polyamide is poly-m-xylylene adipamide. It has a Tg near 85 to 100°C and a of 235 to 240°C. To obtain high heat deflection temperature, the filled grades are normally sold. Applications include gears, electrical plugs, and mowing machine components. 

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