Binder extraction

Question 1

What happens in an oxidizing environment?

Answer 1

~ organics (binder, plasticizer) burn out

~ this exothermic process can easily become self-feeding

~ volume of evolved gas is several hundred times greater than the condensed organic phase: heating of a green part must be extremely slow to prevent bloating

~ thermolysis can take ~1week

Question 2

How can thermolyis time be shortened?

Answer 2

~ by recognizing the temperatures at which organic gases rapidly form

~ heat slowly only at those temperatures (PID!!!)

Question 3

What happens in an intert, reducing or mild vacuum environment?

Answer 3

~ organics endothermically volatize away (still need slow heating, ex: 0.1C/min)

~ for some polymeric additives (ex: phenolic resin) residual carbon wi;; be left behind, coating the particles

Question 4

What happens when using constant-pumping vacuum?

Answer 4

~ heating can be feedback controlled based on pressure: with commerical temp control modules, heating can be put on “hold” when pressure (lack of volume) exceeds a specified value –> extraction is too rapid

~ also useful when other particle surface coatings are volatilized (ex: H2O)