The invention relates to a semi-crystalline semi-aromatic polyamide comprising A-A-B-B units derived from (a) dicarboxylic acids consisting of a mixture of aromatic dicarboxylic acid and aliphatic dicarboxylic acid and (b) diamines consisting of a mixture of long chain aliphatic diamine and short chain aliphatic diamine, wherein (a-i) the aromatic dicarboxylic acid consists for at least 80 mole % of terephthalic acid, and (a-ii) the aliphatic dicarboxylic acid constitutes at least 5 mole % of the dicarboxylic acids, (b-i) the short chain aliphatic diamine constitutes at least 10 mole % of the diamines, and (c) the aromatic dicarboxylic acid and the long chain aliphatic diamine constitute 60-90 mole % of the total molar amount of dicarboxylic acids and diamines.
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