Unit 4 Flashcards
Piezoelectricity meaning
The ability to release an electric charge when deformed. When an electric current is passed through a piezoelectric material its volume will increase or it will vibrate.
Magneto-rheostatic & Electro-rheostatic meaning
Electro-rheostatic (ER) and magneto-rheostatic (MR) materials are fluids that can undergo dramatic changes in their viscosity.
viscosity meaning
the state of being thick, sticky, and semi-fluid in consistency, due to internal friction
what are MR fluids used for?
use in car shock absorbers, damping washing machine vibration, prosthetic limbs, exercise equipment and surface polishing of machine parts.
what are ER fluids used for?
use in clutches and valves, as well as engine mounts designed to reduce noise and vibration in vehicles.
Thermoelectricity meaning
Thermoelectricity is, at its simplest, electricity produced directly from heat. It involves the joining of two dissimilar conductors that, when heated, produce a direct current.
What is thermoelectricity used for?
used in remote areas and space probes to power radio transmitters and receivers.
Photochromicity meaning
Photochromicity refers to a material that can described as having a reversible change of colour when exposed to light.
How does photochromicity work?
A chemical either on the surface of the lens or embedded within the glass reacts to ultraviolet light, which causes it to change form and therefore its light absorption spectra.
Example of photochromicity?
One of the most popular applications is for colour-changing sunglass lenses, which can darken as the sun brightens.
Shape memory Alloys meaning
have a pseudo-elastic property that allows them body to return to its original shape after deforming. Their shape changing property can be stimulated by either a change in temperature or the application of an electrical current. When the load is released, the body returns to its original shape.
What are SMAs used for?
- The frames of some eyeglasses use SMAs to create a flexible frame
- Medical devices such as Nitinol stents use SMAs to repair damaged blood vessels. to allow a thin device to be inserted into a vein. As the device heats up because of the body heat, it changes shape and keeps the blood vessel open.
modern plastics are derived from?
-derived from non-renewable petroleum resource, such as crude oil, coal or natural gas.
All plastics are a type of ___?
polymer
What determines the physical and mechanical properties of plastic?
the different types of bonds.
Which plastics are made from biomass?
PLA and Bioplastic
what is biomass?
plant or animal material used as fuel to produce electricity or heat.
plastic production’s impact on our environment?
The social, environmental, and economic impacts of plastic production and disposal are of increasing concern for our global community.
Which plastic can be reheated and molded?
Thermoplastics
Characteristics of thermoplastics
low production cost
easily injected into a mold
low stiffness, making them ideal for uses requiring flexibility
can be reshaped after heating
Types of thermoplastics?
- PP (Polypropylene)
- PE (Polyethylene)
- HIPS (High Impact Polystyrene)
- ABS
- PVC (Polyvinyl Chloride)
Properties and applications of polypropylene?
Polymer resin
Low cost
Stiff
Production Process: Injection molding
Application:bottles such as cleaning materials
Properties and applications of Polyethylene?
- Available in a variety of density levels (low, medium, high)
- Density determines properties:
LDPE: low cost, translucent
HDPE: Flexible, transparent to opaque, low temperature toughness, waterproof, Very common
Applications: plastic bags, water bottles
Properties and applications of High Impact Polystyrene?
Easy to machine and shape
Low cost
impact resistant
Applications: Lunch trays