Week 15 - Molding and casting
Assignment
Review the safety data sheets for each of your molding and casting materials, then make and compare test casts with each of them.
1. VytaFlex 50
Introduction: this is a rubber Urethane used for molds. It comes with two components you have to mix before use. (Link) VytaFlex mold rubbers work especially well for casting pigmented / colored concrete. You have different types of VitaFlex. From 10 to 60. This number is the hardness of the material
General instructionsSafety Sheet: https://www.smooth-on.com/tb/files/Vytaflex_Series_TB.pdf
Material Safety Data Sheet (MSDS): http://www.sculpt.com/2017/Tech/MsdsTechSheets/MSDS_Vytaflex_Series.pdf
Technical specifications:
Pot Life: 60 minutes (how long can you use it after mixing)
Cure time :16 hours
Flash Point: >132 °C (temperature at which it gives off vapor)
Flammability Classification: Non-Flammable
Hardness: 50
General Safety
If heated or sprayed it can cause long problems
Inhalation: Vapors can cause irritation
Eye: May cause irritation and blurred vision.
Skin: Contact can cause irritation
Safety Steps:
Good ventilation (room size)
Safety glasses
Long sleeves
Rubber gloves
Pre Use conditions:
Store and use at room temperature (23°C)
Use in a humidity below 50% Relative humidity (RH)
How to use:
Apply release wax (or other material to make sure it will not stick on the model)
Mix 1/1 both components for 2 minute
Pour over the model
Wait for 16 hours to cure
2. PMC 121/30
Location of safety (Link)
Health
Hazards to health:
H302 Acute toxicity, oral - Category 4
H312 Acute toxicity, dermal - Category 4
H332 Acute toxicity, inhalation - Category 4
H315 Skin irritation - Category 2
H319 Eye irritation - Category 2
AH335Specific target organ toxicity-single exposure - Category 3 (respiratory)
H351 Carcinogenicity - Category 2
Health hazards: skin irritation, don't swallow, serious eye irritation, may cause respiratory irritation, Suspected of causing cancer.
Not for kids.
Don't breath it.
Wash with soap thoroughly after use.
Use outdoors or in well ventilated area.
Wear protective gloves, clothing, eye and face protection.
What to do when exposed:
Swallow: go to doctor, bring the material.
on skin: wash thoroughly.
Inhaled: leave the room with the fumes.
In eyes: wash with water, remove contact lenses. Go to doctor if it feels bad.
If skin irritation occurs: go to doctor.
Storage:
Store in a well-ventilated place, and keep it behind a lock. Label properly. Keep away from heat and sunlight. Reseal carefully after opening. Avoid water contamination.
Be advised: symptoms can be delayed and only occur after 48 hours.
Fire/heat
When on fire you can squelch it with: water fog, dry chemical, and carbon dioxide foam. When heated material may expand and burst out of its container.
Environment:
Don't let it get into the sewer or drainage or open water ways. No special environmental precautions required.
Technical specifications:
Color: Clear Amber
Shore Hardness: 30 A
Pot Life 30 minutes
Cure Time 16 hours
Shrinkage < .001 in. / in.
Instructions for use.
PMC121/30 is a urethane rubber. It is used to create a mold which in turn is used to create the model. (You also need a mold to cast the rubber. So the rubber mold is mold 2.) It can be used for casting waxes, Smooth-On liquid plastics, gypsum plasters and other materials. Easy to mix and pour. You can add color by adding color tints.
Safety clothing
Wear safety glasses, long sleeves and rubber gloves to minimize contamination risk.
What mold to use
You use a hard mold for soft material and a soft mold for hard material. The hardness is defined by the 'shore'.
xThe Shore 00 Hardness Scale measures rubbers and gels that are very soft.
xThe Shore A Hardness Scale measures the hardness of flexible mold rubbers.
xThe Shore D Hardness Scale measures the hardness of hard rubbers, semi-rigid plastics and hard plastics.
PMC121/30 has a shore of 30A, which is defined as soft in the picture above. So I will use a hard mold.
Release agents
The PMC needs a release agent. This is stuff you spray over your first mold before you cast the rubber. This helps getting it out after it is cured. Like buttering your cake form before entering the dough.
Preparations
Mixing: add equal volumes of Part A and Part B. Mix thoroughly.
3. Smooth-Cast 325
The Smooth-Cast™ 325 plastics are urethane resins that were developed specifically for adding color pigments and fillers to achieve true color representation or filler effect.
Pot life is defined as the amount of time it takes for an initial mixed viscosity to double, or quadruple for lower viscosity products (<1000 cPs).
Safety
Wear safety glasses, long sleeves and rubber gloves to minimize contamination risk. Use only in a well-ventilated area
Preparation
should be used as soon as possible.
stored and used in a warm environment (73°F/23°C).
All liquid urethanes will react with moisture in the air, causing bubbles.
Mixing sticks should be flat and stiff with defined edges for scraping the sides and bottom of your mixing container.
Applying A Release Agent
A liberal coat of release agent should be applied onto all surfaces that will contact the plastic.
Part A (Yellow Label) /Part B (Blue Label)
Pigmenting
Generally, 0.5% - 1% Smooth-On pigment added by weight of Part B will yield rich, vibrant color. For translucent effect, add 0.1% pigment.
Measuring & Mixing
Liquid urethanes are moisture sensitive and will absorb atmospheric moisture.
Mixing tools and containers should be clean and made of metal, glass or plastic.
Stir or shake both Part A & Part B thoroughly before dispensing.
Dispense equal volumes of Parts A and B into the mixing container (115A:100B by weight) and mix thoroughly.
Curing - Important:
Use this product with at least room size ventilation or in proximity to a forced outlet air vent and do not inhale/breathe fumes. Castings with significant mass may be hot to the touch and irritate skin immediately following cure. Let casting cool to room temperature before handling. Smooth-Cast™ 325 will cure in 7-10 minutes
Post Curing
Castings will reach “full cure” faster and achieve maximum physical properties if post cured. Allow material to cure for recommended cure time at room temperature followed by 4 - 6 hours at 150°F / 65°C.