Quiz 9

Intermediate between elastic and viscous

What type of behavior: materials resist shear flow and shear strain over time as stress is applied

What type of behavior: dashpot model

What type of behavior: material strain when stretched and return quickly to original state when stress removed

What type of behavior: spring model

What type of material is liquid-y

What type of material is viscous behavior (flow)

What type of material is LOTS OF plastic deformation

What type of material follows dashpot model

What type of material is liquids

What type of material is dispersions/emulsions

What type of material is gels/soft solids

What type of material is polymer solutions (dilute, concentrated, melt)

What type of material is solid-y

What type of material has elastic behavior

What type of material has LITTLE plastic deformation

What type of material follows spring model

What type of material are classical engineering materials: crystalline solids, metals, alloys, ceramics

For what materials does deformation requires movement of atomic planes

What type of material are hard plastics

What type of material are stiff biomaterials

What type of material are elastomers

What type of material are polymer composites

What type of material are fibers

What type of material are crosslinked polymer networks

What type of materials have a modulus on the order of 100Gpa

What type of materials have a modulus on the order of eV/(10^-10)^3

What type of materials have a modulus on the order of 4 to 400Pa

What type of materials have a modulus on the order of k_BT/(10^-7to 10^-8)^3

why do classical materials have a large modulus E

study of flow of materials in response to applied force, especially for soft materials

Critical in characterization for processing and formulation

used in place of tensile testing for soft materials as deform easily compared to stiff materials

What test is for materials that reasonably follow the spring model

What test is for materials that follow the dashpot model or viscoelastic model

What test assumes instantaneous response to loading

What test assumes time-dependent response to loading

Which test requires a minimum value of the elastic modulus E to be accurate that some softer materials do not meet

Which test is possible (but may not be the best option) for stiffer materials,—hard plastics, stiff biomaterials, etc.

Which test requires clamps

Why are the clamps for the tensile test bad for gels

Why are the clamps for the tensile test bad for liquids

soft material is placed into a plate or cup and a shear force is applied by spinning or twisting an object thru the soft material to generate a shear stress τ, then shear strain γ is measured over time and shear rate γ ̇ is calculated

shear stress and strain are same at all points

shear stress and strain are different at different points in the material

Shear rheometry setup for large volumes

shear rheometry setup that is very sensitive

shear rheometry steup that is for materials with lower viscosity (thinner)

What are the 2 shear rheometry setups that have homogeneous strain fields

What is the shear rheometry setups that have inhomogeneous strain fields

Why use cone-plate setup vs parallel plate setup

For what volumes are parallel plates and cone-plate used for

How sensitive (low/high) are parallel plates and cone-plate

Are parallel plates and cone-plate for (high/low) viscosity materials

sliding of fluid layer due to applied shear force, measured by γ and γ ̇

In shear flow diagrams how is the top layer moving

In shear flow diagrams how is the bottom layer moving

force/area

Units of shear stress

displacement/distance

Units of shear strain

What is another word for shear strain

derivative of shear strain

velocity/distance

(dx/dt)/h

shear stress/shear rate

τ∝γ ̇ where η is constant of proportionality, τ=ηγ ̇

follows the Newtonian law, η=constant

What type of fluids have Newtonian behavior always

What type of fluids have viscosity that changes with shear rate/stress

Water is what type of fluid

Ketchup is what type fluid

Type of fluid that has Newtonian behavior above critical stress

Stress above which Bingham plastic flow

What is the critical stress typically

What sort of behavior (elastic/viscous) does a Bingham plastic have below the critical stress

What sort of behavior (elastic/viscous) does a Bingham plastic have above the critical stress

Type of fluid that acts as pseudoplastic above critical stress

What is another term for a pseudoplastic

Why are shear thinning fluids called that

As shear rate or shear stress increases, viscosity does what for a shear thinning fluid

As shear rate or shear stress increases, does a shear thinning fluid act more viscous or elastic

In a psuedoplastic (shear thinning): for a given shear rate, shear stress is (higher/lower) than a comparable Newtonian fluid

In a psuedoplastic (shear thinning): for a given shear stress, shear rate is (higher/lower) than a comparable Newtonian fluid

Are polymer solutions pseudoplastics or dilatency

Why do polymer solutions demonstrate shear thinning behavior

Why do suspensions demonstrate shear thinning behavior

Why do emulsions demonstrate shear thinning behavior

What is another term for a dilatency

Why are shear thickening fluids called that

As shear rate or shear stress increases, viscosity does what for a shear thickening fluid

As shear rate or shear stress increases, does a shear thickening fluid act more viscous or elastic

In a dilatency (shear thickening): for a given shear rate, shear stress is (higher/lower) than a comparable Newtonian fluid

In a dilatency (shear thickening): for a given shear stress, shear rate is (higher/lower) than a comparable Newtonian fluid

Are dense polymer suspensions pseudoplastics or dilatency

Is cornstarch pseudoplastic or dilatency

Is quicksand pseudoplastic or dilatency

Why does dilatency occur

ratio of relaxation time of material to amount of time required to reach a reference strain

characterizes fluidity of materials unders specific flow conditions

De for elastic behavior

De for viscous behavior

De for "interesting" behavior

Is tau material or tau observer a function of temperature

How to change tau material

How to change tau observer

Silly putty sit out for long enough, it conforms to its container. What is the Deborah number for this behavior

Silly putty sit out for long enough, it conforms to its container. What is kind of behavior is this

If you shoot silly putty with a gun, it shatters. What is the Deborah number for this behavior

If you shoot silly putty with a gun, it shatters. What is this kind of behavior

What type of behavior corresponds to De=infinity

What type of behavior corresponds to De=0

individual molecules respond to what by adopting a non-equilibrium distribution of conformations

What sort of behavior is this: After deformation, left to themselves, the molecules will relax back to an isotropic equilibrium distribution of conformations

What sort of behavior is this: After deformation, as molecules relax, motion of molecules through surrounding solution dissipates stored elastic energy

What sort of behavior is this: material relaxes but does not do not go all the way back to its original state

Measures RELATIVE viscosity, compare how fast different samples flows

Can you determine the viscous/elastic contribution from viscometry

What is viscometry useful for

Is viscosity simple/hard to run

Is viscometry highly/poorly reproducible

Can you use different flow conditions in viscometry

Should you use the same setup every time for viscometry

fill up cup and pour it out, a machine figures out viscosity stuff

like cup method but it compares speeds as you vary temperature and stuff

reads viscosity throughout reaction to control addition of solvent for process control

continuous rotation, stress τ is constant, velocity gradient γ ̇ slowly increases, see change in viscosity η

In strin rate sweep, how does stress change

In strain rate sweep, how does velocity gradient change

In strain rate sweep, how does viscosity change

In strain rate sweep, how does viscosity change in 0 shear viscosity regime

What occurs at low shear rate in strain rate sweep

What sort of behavior occurs in the 0 shear viscosity regime

What occurs at high shear rate in strain rate sweep

In strain rate sweep, how does viscosity change as shear rate increases in shear thinning regime

What is the best rheometry setup for strain rate sweep

continuous rotation, stress τ slowly increases, velocity gradient γ ̇ is constant, see change in viscosity η

In stress ramp: how does stress change

In stress ramp: how does velocity gradient change

In stress ramp, how does viscosity change (shear thinning)

When does maximum viscosity occur in stress ramp

How to idenfity yield stress via stress ramp

creep?

device that performs extrusion

What device is made from a hopper and screw

most common and widely used unit operation in polymer processing

In extrusion, what is placed in the hopper

What 2 things happens to the melt as the screw conveyer pushes the polymer melt forward in an extruder?

What 2 things happen in terms of heating to the melt as it is compressed and pressurized in a extruder?

What is melt forced thru at end of extrusion

What is the property of extruded materials that results from continuous of the flow thru the shaping die

When thermoplatics are extruded, what is needed in terms of cooling

Why must thermoplastics be cooled below Tm or Tg

How is cooling thermoplastics below Tm or Tg acheived

Most common size basis for screw extruders

Standard size range for Db

Are smaller sizes than 1.5 to 8in of Db available for labs

What is Qe

What is the units of extruder capacity

what is Db

What is the units of Db

What is Qe in terms of Db

What is the second most often specified sizing basis for screw extruders

What are the 2 most common L/D for thermoplastics

Do rubbers use 20:1 and 24:1 for L/D or lower L/D values

Which has a longer barrel, 20:1 or 24:1

What is the first value in 24:1

What is the second value in 20:1

What yields a more homogeneous extrudate

What are 2 possible results of too high L/D

Why does too high L/D lead to polymer degradation and loss of additive effectiveness

what L/D should be used for polymers that melt easily

Is 20:1 or 24:1 L/D more expensive

1 revolution of the part that sticks out of the screw

distance from the base of the screw to the outiside end of the flight

distance from 1 flight to another

what are the 3 zones of a typical screw extruder

What do zones differ in

what do zones not differ in

ratio of channel depth in feed to channel depth in metering section

What is the first 3 consideration for screw designs listed

What are 3 forms in which polymer can be fed in

what is the second 3 consideration for screw designs listed

What defines a vented extruder

What is the purpose of a venting port in terms of pressure

What is the purpose of venting ports in terms of air

Why do you not want air bubbles

How many screws does a ram extruder have

How many screws does a single screw exruder have

How many screws does a twin screw extruder have

Type of extruder where you just push material thru shaping die

What is a ram extruder used for

For what types of materials is a single screw extruder used for

WHat is the standard type of extruder

What is the use of a twin screw extruder

A rotational rheometer applies a small amplitude oscillatory shear test

oscillating torque is applied and angular displacement is measured to calculate strain

angular displacement is applied and torque needed to effect displacement is measured to calculate shear stress

what is applied in the controlled stress experiment

what is applied in the controlled strain experiment

what is measured in the controlled stress experiment

what is measured in the controlled strain experiment

What is the purpose of measuring angular displacement in the controlled stress experiment

What is the purpose of measuring oscillating torque in the controlled strain experiment

can determine the viscous and elastic components that contribute to G* via phase angle δ

angle between max stess peak and max strain peak

distance between the peaks (phase difference) of the shear stress curve and shear strain curve

If G' is in the horizontal direction and G'' is in the verticla direction, what is the angle between the horizontal and G*

What is said about a material with phase angle of 0 degrees

What is said about a material with phase angle of 90 degrees

What is said about a material with phase angle between 0 and 90 degrees

elastic contribution to G*

Viscous contribution to G*

G' name

G'' name

storage modulus symbol

Loss modulus symbol

G'>G''

G'<G''

Relationship between G' and G'' for viscoelastic solid

Relationship between G' and G'' for viscoelastic liquid

at fixed frequency ω of oscillation, shear strain γ is increased, G' and G'' are measured

Region in G' and G'' strain sweep at low strain γ

Region in G' and G'' strain sweep where G' and G'' are independent of strain, constant

Strain value in G' and G'' strain sweep, above this strain material will switch from viscoelastic solid to liquid or vice versa

The stronger the gel, the (higher/lower) the G'

The (stronger/weaker) the gel, the lower the G'

tool to determine material properties over a long period of time by shifting data

Allows you to predict behavior lie 20 years down the line without actually doing a 20-year long aging study

Do curves of modulus as function of time change shape as temperature changes

How do curves of modulus as function of time change as temperature changes

a curve of modulus as function of time at a given temperature used as a reference to predict curves at various temperatures by applying a shift operation

When changing from some temperature T_1 to T_2, it is equivalent to multiplying the time scale by constant factor a_T

When changing from some temperature T_1 to T_2, it is equivalent to shifting left by constant factor a_T

converting powders, pellets, and sheets into useful products

6 types of polymer processing

The 3 general steps in polymer processing

Example of 2 things that can occur in pre-shaping steps

What happens in shaping step

Example of 1 thing that can occur in shape stabilization step

broadly used to adjust the surface properties of materials

Can coating be made from polymer melts

Can coatings be made from polymer solutions

What are 2 solifidiciation methods used for polymer based coatings

What are 2 different attachement mechanisms for polymer based coatings

Coatings can be used to achieve the following 5 surface properties

all the different things you mix together the get the coating

What are some components of a coating formulation

What are 2 examples properties that a coating can be made to have via adiditives for improved products

What are 3 examples of properties that a coating can be made to have via additives to aid in processing

Does mixing order make a differnce in coating formulation

Can you easily predict properties based on coating formulation

Why is is hard to predict properties based on coating formulation

What is used to get wanted properties based on coating formulation

What are the negative consequences of ridges on surface of a coating

way to apply a coating to a flexible film

Is a procedure where the roll of film proceeds thru lots of processes thru continuous pass with rolls

Steps: Unwind, cleaning, coating, oven, web flip, uv cure, inspection, lamination, rewind

The 5 Most Common Coating Types

Coating Type: liquid coating material is put in die that lays coating onto surface moved via roller

Does slot die apply homogeneous/inhomogenous layers

How is slot die pre-metered

Is slot die to touch free

Does solvent evaporate in slot die

Why does solvent not evaporate in slot die

Full area nonstop coating, stripe, and stop-start coating are all possible

Coating type: metal rod with a bunch of wire wound around it

The 2 more expensive coating types

The 3 less expensive coating types

In meyer rod, what is coat weight dependent on

Does Meyer rod apply homogeneous/inhomogenous layers

What is a result of the inhomogenous layers of Meyer rod

Is meyer rod tolerant/strict to non-precision engineering of other components of coating machine

How to change coat weight on meyer rod

What are the wires in Meyer rod for

Coating type: dip thing to be coated it into a solution bath and when you pull the thing out, excess liquid coating material fall off

In dip coating, what determines coat weight

How can you meter dip coating

What sort of objects is dip coating used for

What is a restiction of types of objects that dip coating can be used for

Is dip coating a closed system

How is dip coating an open system

What is a negative consequence of bath of solution being open in dip coating

Is dip coating good for plyers

Is dip coating good for fabrics

Coating Type: coating liquid is pooled on film and a blade just meters off the extra coating

In blade coating, what determines coating thickness

is blade cheap compared to slot die and gravure

Is blade as preceise a gravure

What other type of coating technique is gravure most similar to conceptually

Coating type: has a roll has a pattern of slots that liquid gets trapped in and gets transferred to a film by pushing the roll up against an impression roll that presses the film between the 2 rolls

How is gravure similar to meyer rod

Which coating type can be used for complex graphics

which coating type is very expensive relatively

Which coating type can print faster than an inkjet printer

In gravure, what determines the coat weight

In gravure, what determines how easily the ink releases

In gravure, as cell vulume increases, what happens to coat weight

Gravure application configuration: 2 rolls, rotating opposite directions to each other, transfer at gap between

Does direct gravure result in stable coating amount and accuracy