Polyphthalamide (PPA) is a semi-aromatic, high-performance plastic that is characterised by exceptional heat resistance. PPA plastic is often the best economical and technical choice for components in the automotive and electronics industry with high demands.
PPA plastics are thermoplastics belonging to the semi-crystalline aromatic polyamides and are usually used in a glass or mineral reinforced or filled form to increase stiffness for high temperature applications. Polyphthalamide is characterised by high heat resistance, good dimensional stability and low warpage, as well as minimal moisture absorption. PPA plastic is not only very stiff and tensile but also has a significantly higher notched impact strength than comparable plastics. PPA plastic is often used instead of metal or more expensive thermoplastics.
PPA plastics are semi-crystalline aromatic polyamides and belong to the class of thermoplastics. Polyphthalamides are semi-aromatic polyamides with amide groups, which are alternately bonded to aliphatic groups and to benzenedicarboxylic acid groups. The properties of PPA plastics differ from those of aliphatic polyamides and aromatic polyamides (aramides).
The production of polyphthalamide requires terephthalic acid or isophthalic acid or a combination of both and at least one aliphatic diamine, such as hexamethylenediamine. PPA plastics are only partially aromatic, as the aromatic acid content accounts for 55 mole percent or more of the repeating units in the polymer chain.
The aromatic part of the polymer backbone has a significant influence on the properties of the material by increasing the melting point, stiffness, heat resistance and chemical resistance, but reducing moisture absorption.
In addition to excellent heat resistance, polyphthalamide is characterised by good dimensional stability with low warpage. Tensile strength, stiffness and notched impact strength are high, moisture absorption is at 0.1 to a maximum of 0.3 % and thus lower than with other polyamides. As a result, PPA plastics exhibit minimal deformation due to water absorption.
The glass transition temperature of PPA plastics rises with the proportion of terephthalic acid. If more than 55 % of the acidic content of a PPA plastic consists of isophthalic acid, the copolymer behaves amorphously. Amorphous PPA plastics are suitable for warpage and transparency.
The crystallinity of the material contributes to chemical resistance and excellent mechanical properties in the temperature range between the glass transition temperature and the melting point.
Compared to conventional polyamides, polyphthalamides have a higher chemical resistance. PPA plastics are also resistant to various aggressive chemicals, such as brake fluid, synthetic engine oil, biodiesel fuel, transmission fluid, glycols, de-icing salt, sulphuric acid, zinc chloride, calcium chloride and transformer oil.
Polyphthalamides have excellent corrosion resistance and adhere directly to a number of elastomers such as plastic-rubber composites without the need for a bonding agent.
Untreated PPA compounds are not flame-retardant and are attacked by strong oxidising agents as well as mineral acids, formic acid and acetic acid.
The majority of non-fibrous PPA plastics are sold as granules and are processed by injection moulding. Polyphthalamide can be welded, screwed, glued, riveted, snap-fitted and soldered. Mechanical processing is done by sawing, planing, milling, drilling or turning. The surfaces of PPA plastics can be painted without any problems.