For Midterms Flashcards by Sherl Nicole M. TABANAO

one of the simplest and most common methods in forming plastic parts

thermoforming

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thermoforming starts with a ___ or _____

sheet, film

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T or F. the sheet in thermoforming is heated until it melts

False, only until it softens

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T or F. in thermoforming, it is possible that the mold is the one brought down to the sheet instead of the other way around to form desired product

true

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T or F. thermoformed molds are very economical

true

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T or F. for prototype molds, plastic materials are the only ones used and not wood or epoxy are not used

False, wood and epoxy are also used

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For mass production, ____ or ___/___ may be used

Aluminum, beryllium/copper

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2 main types of molds

Male, positive, core | Female, negative, cavity

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Material distribution and thickness is affected by the type of _____ and the ____ of the part, especially the _____

Type of thermoforming, the geometry of the part, especially the surface area

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T or F. Thermoformed parts are also prone to Undercuts

False, cannot have undercuts

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The most common packaging application of thermoforming are ____ and ____

Clamshell and blister packaging

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Clamshell and blisters are made from ____, and sometimes ___ and ____

PVC, PET and HIPS

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T or F. thermoforming can also be used to produce tubs

true

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T or F. thermoform is capable of producing snap-on lids with precision

false

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T or F. thermoforming cannot make hollow objects with narrow necks.

true

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Method the makes use of vacuum pressure to suck in the film or sheet to the mold

Vacuum thermoforming

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Method that makes use of air pressure to blow the soft melt or film towards the mold

Pressure thermoforming

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Method that makes use of both pressure to blow the mold up to stretch, the vacuum to suck in the film to the mold

Billow thermoforming

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What thermoforming method uses the product as the mold?

Skin packaging

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3 microwavable materials for packaging

PP, PS, CPET

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_____ refers to the material that can be used for two common types of oven

CPET

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2 common types of oven

Microwavable and conventional oven

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T or F. CPET has better water and oxygen barrier than other plastics in the category

True

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T or F. CPET has poor grease and oil resistance and greatly affects the food tast

False, Good grease and oil resistance and minimally affects food taste

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T or F. CPET is costly

True

T or F. PP can be used for conventional ovens but not microwave

False, microwavable but not conventional

T or F. low density blends of PS can be used for microwave

True

___ refers to a forming method that does not require extruder

Roto-molding

___ refers to a forming method that can make hollow parts with no opening

Roto-molding

___ refers to a forming method that also does not use extruder and capable of making closures without gate mark.

Compression molding

___ refers to a forming method where a bottle is EBMed but filled before it is sealed with heated plastic

Blow-fill-seal

Used for single-use bottle and pharmaceuticals

Blow-fill-seal

3 common expanded plastics

EPS, EPE, PU

Expanding a plastic requires _____ introduced into the plastic mass

Fine bubbles

Expanding a plastic requires the use of additives called _____

Blowing agents

____ can be used to make fine bubbles

Nucleating agents

Smaller bubbles make denser “____” foams that will not absorb liquid

Closed-cell

Larger bubbles make an “____” foams which readily absorbs liquids

Open-cell

One method of making____ is by extruding it like a blown film except now it is an expanded foam due to blowing agent.

EPS film

2nd method of making EPS film is by pre-expanding a mass of PS beads, place them into a mold and heat to a point it becomes ______

thermoelastic

PU is made by _______ of isocyanate and glycol

condensation polymerization

Spraying isocyanate and glycol directly into a mold allows ____ to become a foam-in-place

T or F. EPS, PU are good insulating materials but not EPE

False, including EPE

is the simplest thermoforming method

Rotary or reciprocating matched die molding

process for making tubs

injection molding

process for making bottles

blow molding

process for making trays, tubs, blister shells

thermoforming

there are two considerations in designing a bottle

1. product nature 2. extraction (how the consumer uses or extracts the product)

bottle design for syrups and sauces

large diameter, smooth walls, no shoulders

It produces a partial internal vacuum which can cause the bottle to panel inward

Hot filling

are deeply countersunk rectangular forms around the bottle's circumference

Expansion panels

Highest hoop strength. Most needed for carbonated products.

Round bottles

T or F. The more flexible the top to bottom axis, the less prone to damage by vibration.

False. the more prone to damage by vibration

This should be generous

Radii and curves

This should be avoided in bottle design

Sharp corners

are usually heavy and need strong top-to-bottom compression.

Large jugs for liquids

The best way to increase strength

a centered opening with gently sloping walls

Most water containers are what style?

F-style, thus the compression is concentrated on one side only

In machinery, bottles with a low center of gravity are

easier to handle

If the bottle is tall,

tipping occurs

Narrow, oval bottles can cause

Shingling, designing small flats at the bottle ends can prevent this.

Bottle labels that are fastest to apply.

Round cross sections

This may be compatible with high labeling speed

Square bottles

Can conform to any complex curve shapes, but paper cannot

Heat shrink labels

Cannot be applied properly if the shoulder is conical

Shoulder label

Can reduce label abrasion

Bottle design

If you want to perfectly align a label,

a wedge shape in the bottom can be incorporated. The machine will detect the wedge and orient the bottle

Plastic: PETG

Typical Bottle Applications: EBM, high-clarity bottle

Plastic: PET

Typical Bottle Applications: IBM, high-clarity bottle

OPET

ISBM, carbonated beverages

PVC

solvent resistant and cosmetic bottles

LDPE

soft, squeezable bottle

HDPE

most opaque consumer bottles

hot-fill applications

BOPP

as PP but better clarity

cosmetic, hard, high gloss

exceptional impact, hot fill

high solvent-resistance barrier

Types of mold (Thermoforming)

Male mold and female mold

Least time consuming and cheapest method

male or positive mold

mimics the final shape of the part, but the part is fabricated over its outer surface

male mold

male molds should be used when fewer than ______ parts are being produced

5-10

-more costly -finishing time is significantly reduced because every part emerges with a smooth outer surface

female molds

Female molds also lend themselves to use with core materials because

the outer skin is always smooth

T or F. The part of the mold that touches the plastic first will have a thinner plastic material

False, thicker plastic material

The side of the side of the plastic in contact with the mold will have a more accurate or controlled dimension. inside- outside-

inside- male mold outside- female mold

allow better dismolding or part removal since the plastic will shrink from the cavity when cooled.

Female molds

The cooled plastic will tend to tighten around the mold

male molds

Molds are usually placed or mounted on a steel plated called the

baseboard

Molds are sometimes coated with ______ or other coating to aid in dismolding

Teflon

Help release the mold quicker during dismoulding.

drafts

allow a plug assist to down into the mold with less risk of the plug hitting the walls of the mold

drafts

allow several parts to be nested on top of one another. This is useful during shipping

tapered parts

RADII One of the most difficult features in thermoforming is the ______ in a female mold

three-sided sharp corner

RADII this feature accentuates the draw ratio because it forces the material to cover the _______ as it is pushed in the corner

three walls

RADII The material appears to stretch and thin out at a geometric rate, usually causing the material to either

thin to an unacceptable ending gauge or actually tear and create a hole in the part

RADII A quick check to see if this condition is occurring is to

hold a part up to a light source and inspect the corners to see if the gauge is so thin that light can be transmitted through the part

The other advantage of radii and chamfers is that they

distribute stress over a larger area that sharp 90 degree corner

Depth of part: 0-3 in

Radii: .015-.025 in

Depth of part: 3-6 in

Radii: .125-.250 in

Depth of part: 6-12 in

Radii: .250-

A common design technique is to use radii and/or a chamfers on the part, preventing the material from having to continue deeper into the corner, thus

arresting the thing that would normally occur

The radius at the bottom of the draw is

most critical

The deeper the part the

larger the radius or chamfer required

can be added to provide stability and additional strength

Ribs

The distance between each rib should be ______ than or equal to its depth

greater

Draw ratio can be aptly called

stretch ratio

the most common ways to solve draw ratio

H:d and areal draw ratio

This is the ratio of the depth of the draw to the longest distance of the mold opening

H:d draw ratio

Usually, most polymers should not exceed 1:1 ratio. So therefore a part which is 1 foot across should not be

1 foot dip

can help manufacture large H:d ratio parts

Plug assist and other methods

This is the amount of surface area that needs to be covered by the plastic material divided by the amount of available plastic material

Areal draw ratio

Surface area of the part/ footprint of the part

Draw ratio