Abs and HIPS separation

patents
www.google.com/patents/US5653867

Another technique that may be used for separating HIPS and ABS involves contacting the mixture with a surface that is heated to a temperature high enough for HIPS to stick to the hot surface but not hot enough for ABS to become sticky. Continuous cleaning of the hot surface is necessary to prevent sticking of the ABS to spots on the hot surface that have residual sticky HIPS.

https://www.youtube.com/watch?v=PnjaRg-sqKA This is a TiTech Optical Sorter. Basically, the machine uses a conveyor belt to drive shredded plastic pieces under an optical sensor which then uses an air-jet to pick or "shoot" out the desired plastic type. The optical sorter is able to process and separate a wide variety of plastic scraps including ABS, ABS/PC, HIPS, PS, PET, PETG, PVC, PP, etc...

Optical sorting
http://www.sherbrooke-oem.com/optical-sorter he operating principle of NIR optical sorting units (Optical Sorter) is quite simple: materials on a conveyor belt travel at high speed under a powerful light source. Part of the light's wavelengths is absorbed by the materials while the other is reflected and captured by lenses. These lenses transmit the signal to a spectrometer and/or camera, which associates each reading with a specific curve since each material has its own signature. Different types of materials, such as plastics (PET, HDPE, PVC, PP, PS, and others) and fibres can be detected. Different sorts of fibres can also be recognized, as with pressed wood and melamine.

Froth flotation
http://infohouse.p2ric.org/ref/08/07501.pdf Separate ABS from HIPS patent 5653867