CAR Material Selection & Properties 3

Question 1

What is the significance of a material's Curie temperature in appliance recycling metal sorting?

Accepted Answer

Above this temperature, ferromagnetic metals lose their magnetic properties

Answer

Understanding the Curie temperature is important because magnetic separation efficiency changes if materials are heated during processing.

Question 2

Which refrigerant oil type requires separate collection because it is miscible with HFC refrigerants?

Accepted Answer

Polyolester (POE) oil

Answer

POE oil is used with HFC refrigerants like R-134a and must be properly drained and managed due to its hygroscopic nature and environmental concerns.

Question 3

Acrylonitrile butadiene styrene (ABS) plastic in appliance housings is best identified by which characteristic?

Accepted Answer

It sinks in water and has resin code #7 or #9

Answer

ABS has a density greater than water (~1.05 g/cm³) and is typically coded #7 (other) or #9 on the resin identification system.

Question 4

Lead solder used in older appliance circuit boards is hazardous primarily due to its:

Accepted Answer

Toxicity and classification as a RCRA hazardous waste

Answer

Lead is classified as a hazardous substance under RCRA, and circuit boards with lead solder must be managed accordingly to prevent soil and groundwater contamination.

Question 5

What property makes aluminum an energy-efficient choice for heat exchanger fins in air conditioners?

Accepted Answer

High thermal conductivity combined with low density

Answer

Aluminum's high thermal conductivity (~205 W/m·K) and low density make it ideal for fins that must efficiently transfer heat while minimizing weight.

(CAR) Certified Appliance Recycler Practice Test

(CAR) Certified Appliance Recycler Practice Test

CAR Material Selection & Properties 3