From the days when plastics were exciting:
The terms Permalite, Permaloid, and Permalon, may have referred to polyester, casein and nylon respectively on early Leda cards, or they may have just been marketing.
Embassy’s Satinsheen and Boilproof were used interchangeably in 1959, even for the same buttons, and were used for all plastic types.
By the 1970-80s, they just said ‘Buttons’, plain and simple! Plastic wasn’t glamourous anymore.