Open Molding Test Questions and Correct Answers (All Modules), With Complete Solution 2024.
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Course
Open Molding
Institution
Open Molding
Open Molding Test Questions and Correct Answers (All Modules), With Complete Solution 2024.
What are the basic process principles of open molding?
Saturating a fiber reinforcement with a thermoset polymer matrix;
depositing this reinforcement onto an open mold (exposed to the atmosphere, not enc...
Open Molding Test Questions and Correct
Answers (All Modules), With Complete Solution
2024.
What are the basic process principles of open molding?
Saturating a fiber reinforcement with a thermoset polymer matrix;
depositing this reinforcement onto an open mold (exposed to the atmosphere, not enclosed);
curing the laminate at ambient temperature.
What are two advantages of composites that are used in construction applications?
Material weight savings for transportation and assembly, and composites typically have excellent
weathering and corrosion properties.
A tool, often referred to as a mold, is used to produce parts in the open molding lamination process.
Once a part has been designed, what is the first step in the tooling process?
The first step is to produce a master model mode, also commonly referred to as a pattern or plug.
If several molds will be required to support production it is best to construct a durable polyester or
epoxy reinforced master plug from the first mold. What two things affect the durability of a master
model mode?
The materials and the method of construction affect the durability of a master model.
During the cross-inking process, what happens to the thermoset resin?
The thermoset resin shrinks.
What must happen after a pattern (or mold) has been conditioned (sanded and buffed) before it is
ready for production?
The pattern or mold must be waxed with a release agent that has been specially formulated for open
molding lamination and is compatible with the specific gel coat and resin that will be used to produce
the part.
The tooling gel coat should be applied in two evenly sprayed coats of what thickness?
18 + 2 wet mils for each coat.
Many modern mold builders have master models in
____________ formats?
Digital formats for easy reference and use with modern equipment and software packages.
What is used to determine when to do a preventative maintenance program for composite tools?
,An evaluation of the number of parts (pulls) that a mold will allow before polystyrene begins to appear
and spread over the mold surface, creating sticking.
What is the purpose of the cured resin (resin matrix)?
to protect the fiber reinforcement;
transfer loads through the reinforcement;
provide shape to the laminate
What does it mean for a resin system to be pre promoted by the resin supplier?
Additives, formulation and chemicals have been put into the resin at the manufacturer to provide
particular properties for its intended use in production.
What are the five basic components of a resin system (resin matrix)?
resin polymer
monomer
inhibitor
promoter
initiator is added to begin the cure
Why are polyester resins the most commonly used resin systems in open molding lamination?
Polyester resins are low cost and the cured physical properties meet many of the needs in the
commercial composite industry.
Why would a higher cost vinyl ester resin be used in an open molding lamination?
It offers superior corrosion resistance and mechanical properties.
What is a polymer backbone?
The polymer backbone refers to the specific type of molecule that is the basic building block of the resin
system.
What are the purposes of a monomer as it is used in a polyester resin?
It co-reacts with the backbone polymer in a resin system when polymerization (crosslinking) takes place
(reactive);
It reduces the viscosity of the polymer to provide a workable liquid product, acting as a diluent.
What are the two most common monomers used with polyester and vinyl ester resins?
Styrene;
Methyl methacrylate (MMA)
What is the purpose of using an inhibitor?
Raw styrene and polyester resin will self-polymerize without the addition of initiator. This polymerization
cannot be stopped, but can be controlled with the addition of an inhibitor, which consumes free radicals,
which naturally occur in the resin.
, Why is a promoter required in open molding lamination resins?
Initiators do not react rapidly enough in resin to produce a workable gel time at room temperature. A
promoter must be added to the resin to interact with the initiator and produce a reasonable cure time.
What is the difference between a catalyst and an inhibitor?
In technical terms, a catalyst causes a chemical reaction but does not enter into the reaction. An initiator
initiates a reaction but becomes consumed in the process.
Resin cures by a process called free radical polymerization. Explain this process.
The initiator decomposes into free radical molecules, which begins the process of crosslinking the
polyester molecules with the styrene molecules in the resin. Increasing the amount of initiator added to
the resin will increase the rate of cure.
What is the most common initiator used in open molding lamination?
MEKP (methyl ethyl ketone peroxide)
What are the general additives that are used to modify and enhance resin properties?
Fillers;
Pigments and colorants;
Fire retardants;
Suppressants or film formers;
UV inhibitors;
Conductive additives
What are the active molecules in an initiator?
Oxygen
What can cause a poor cross-linking reaction in open molding lamination?
A poor initial cross-linking reaction can be caused by low initiator levels, improper amounts of promoter
or inhibitor in the resin, and/or low shop temperature.
What production procedures can be implemented to correct quality problems that are a direct result
of a faulty cure?
Use the proper initiator in the proper ratio;
maintain shop temperatures above 60° F at all times;
pay attention to details such as initiator mixture, compressed air quality;
evaluate application techniques.
What is the definition of viscosity as it relates to open molding lamination?
Viscosity is a measure of fluid resistance to flow. This is the proper definition that should be used when
discussing resins.
In open molding, what flow characteristics must a resin have?
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