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Questions and Answers
Vat photopolymerization processes primarily use radiation-curable resins as their primary materials.
Vat photopolymerization processes primarily use radiation-curable resins as their primary materials.
True
Some visible light systems are used in photopolymerization processes.
Some visible light systems are used in photopolymerization processes.
True
Photopolymers were developed in the late 1960s and soon became widely applied in several commercial areas.
Photopolymers were developed in the late 1960s and soon became widely applied in several commercial areas.
True
Stereolithography was the first vat photopolymerization process.
Stereolithography was the first vat photopolymerization process.
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Longer polymer molecules yield higher molecular weights, indicating a more complete reaction
Longer polymer molecules yield higher molecular weights, indicating a more complete reaction
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Fig. 4.4 shows the P–I term indicating a photoinitiator, $I$ symbol as a free radical, and $M$ as a monomer
Fig. 4.4 shows the P–I term indicating a photoinitiator, $I$ symbol as a free radical, and $M$ as a monomer
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Polymerization terminates from recombination, disproportionation, or occlusion
Polymerization terminates from recombination, disproportionation, or occlusion
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Occlusion occurs when free radicals become 'trapped' within a solidified polymer, affecting aging and mechanical properties
Occlusion occurs when free radicals become 'trapped' within a solidified polymer, affecting aging and mechanical properties
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Cationic photopolymerization involves a photoinitiator generating a cation, reacting with a monomer, and a termination process
Cationic photopolymerization involves a photoinitiator generating a cation, reacting with a monomer, and a termination process
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Basic raw materials like polyols, epoxides, and (meth) acrylic acids are used for radiation curing
Basic raw materials like polyols, epoxides, and (meth) acrylic acids are used for radiation curing
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Resin formulations include multifunctional monomers, polyol polyacrylates, and various oligomers
Resin formulations include multifunctional monomers, polyol polyacrylates, and various oligomers
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Photosensitizers are often used with photoinitiators, and various additives are used to achieve optimal performance
Photosensitizers are often used with photoinitiators, and various additives are used to achieve optimal performance
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The photoinitiator's role is to convert light energy into reactive intermediates, either radicals or cationic species
The photoinitiator's role is to convert light energy into reactive intermediates, either radicals or cationic species
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In VP, radical photoinitiator systems include compounds that undergo unimolecular bond cleavage upon irradiation
In VP, radical photoinitiator systems include compounds that undergo unimolecular bond cleavage upon irradiation
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The Irgacure family of radical photoinitiators from Ciba Specialty Chemicals is commonly used in VP
The Irgacure family of radical photoinitiators from Ciba Specialty Chemicals is commonly used in VP
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Photoinduced cationic polymerizations have received much less attention but have seen rapid development since the 1970s
Photoinduced cationic polymerizations have received much less attention but have seen rapid development since the 1970s
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Thermoplastic polymers are typically injection molded with a linear or branched molecular structure, while VP photopolymers are cross-linked and do not melt, exhibiting less creep and stress relaxation.
Thermoplastic polymers are typically injection molded with a linear or branched molecular structure, while VP photopolymers are cross-linked and do not melt, exhibiting less creep and stress relaxation.
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The first US patents for SL resins were published in 1989 and 1990, prepared from acrylates, which produced weak parts due to shrinkage and curling.
The first US patents for SL resins were published in 1989 and 1990, prepared from acrylates, which produced weak parts due to shrinkage and curling.
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Acrylate-based resins typically could only be cured to 46% completion when exposed to the laser, leading to accuracy issues and curling during or after part fabrication.
Acrylate-based resins typically could only be cured to 46% completion when exposed to the laser, leading to accuracy issues and curling during or after part fabrication.
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Patents for epoxide composition for SL resins appeared in 1988 (Japanese), producing more accurate, harder, and stronger parts with lower shrinkage and reduced susceptibility to oxygen inhibition.
Patents for epoxide composition for SL resins appeared in 1988 (Japanese), producing more accurate, harder, and stronger parts with lower shrinkage and reduced susceptibility to oxygen inhibition.
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Epoxy resins have disadvantages of slow photospeed and brittleness, requiring the addition of acrylate to rapidly build part strength and reduce brittleness.
Epoxy resins have disadvantages of slow photospeed and brittleness, requiring the addition of acrylate to rapidly build part strength and reduce brittleness.
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Most commercially available SL resins today are epoxides with some acrylate content to combine the advantages of both curing types and improve accuracy.
Most commercially available SL resins today are epoxides with some acrylate content to combine the advantages of both curing types and improve accuracy.
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VP photopolymers consist of photoinitiators, reactive diluents, flexibilizers, stabilizers, and liquid monomers, reacting with UV radiation to start polymer chains and cross-link.
VP photopolymers consist of photoinitiators, reactive diluents, flexibilizers, stabilizers, and liquid monomers, reacting with UV radiation to start polymer chains and cross-link.
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Two main types of photopolymer chemistry are evident: free-radical photopolymerization (acrylate) and cationic photopolymerization (epoxy and vinylether).
Two main types of photopolymer chemistry are evident: free-radical photopolymerization (acrylate) and cationic photopolymerization (epoxy and vinylether).
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Acrylate photopolymers exhibit high photospeed but significant shrinkage and a tendency to warp and curl, thus rarely used without epoxy or other elements.
Acrylate photopolymers exhibit high photospeed but significant shrinkage and a tendency to warp and curl, thus rarely used without epoxy or other elements.
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Epoxy SL resins typically have much smaller shrinkages and less tendency to warp and curl due to ring-opening polymerization, resulting in minimal volume change.
Epoxy SL resins typically have much smaller shrinkages and less tendency to warp and curl due to ring-opening polymerization, resulting in minimal volume change.
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Almost all commercially available SL resins have significant amounts of epoxies, with polymerization being an exothermic reaction requiring a catalyst.
Almost all commercially available SL resins have significant amounts of epoxies, with polymerization being an exothermic reaction requiring a catalyst.
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The free radical-initiated polymerization process involves the production of radicals from photons, which can lead to the polymerization of over 1,000 monomers.
The free radical-initiated polymerization process involves the production of radicals from photons, which can lead to the polymerization of over 1,000 monomers.
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Photopolymerization was developed in the late 1960s and found wide applications in commercial areas such as coating and printing industries.
Photopolymerization was developed in the late 1960s and found wide applications in commercial areas such as coating and printing industries.
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Stereolithography (SL) technology was introduced in the mid-1980s.
Stereolithography (SL) technology was introduced in the mid-1980s.
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Vat photopolymerization encompasses SL and related processes, using various types of radiation including gamma rays, X-rays, electron beams, UV, and visible light to cure commercial photopolymers.
Vat photopolymerization encompasses SL and related processes, using various types of radiation including gamma rays, X-rays, electron beams, UV, and visible light to cure commercial photopolymers.
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Photopolymers are predominantly used in dentistry for sealing teeth surfaces and preventing cavities.
Photopolymers are predominantly used in dentistry for sealing teeth surfaces and preventing cavities.
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Vector scan and mask projection approaches in vat photopolymerization require scanning laser beams.
Vector scan and mask projection approaches in vat photopolymerization require scanning laser beams.
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UV-curable photopolymers are used in a variety of applications including photoresists in the microelectronics industry.
UV-curable photopolymers are used in a variety of applications including photoresists in the microelectronics industry.
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In SL systems, UV radiation is used exclusively, although other types could be used.
In SL systems, UV radiation is used exclusively, although other types could be used.
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Vat photopolymerization processes include vector scan, mask projection, and two-photon approaches.
Vat photopolymerization processes include vector scan, mask projection, and two-photon approaches.
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3D Systems was created to market SL machines as 'rapid prototyping' machines to the product development industry.
3D Systems was created to market SL machines as 'rapid prototyping' machines to the product development industry.
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In mask projection DMD-based systems, UV and visible light radiation are used.
In mask projection DMD-based systems, UV and visible light radiation are used.
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The two-photon approach in vat photopolymerization fabricates parts below the resin surface without the need for recoating.
The two-photon approach in vat photopolymerization fabricates parts below the resin surface without the need for recoating.
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Vat photopolymerization processes use only visible light for curing commercial photopolymers.
Vat photopolymerization processes use only visible light for curing commercial photopolymers.
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Study Notes
Photopolymerization and Vat Photopolymerization Processes
- Photopolymerization, a complex reaction involving many chemical participants, was developed in the late 1960s and found wide applications in commercial areas such as coating and printing industries.
- Photopolymers are widely used in glossy coatings on paper and cardboard, and in dentistry for sealing teeth surfaces and preventing cavities.
- Stereolithography (SL) technology was introduced in the mid-1980s, allowing the production of solid 3D parts by curing one layer over a previous layer using UV-curable materials and a scanning laser.
- 3D Systems was created to market SL machines as "rapid prototyping" machines to the product development industry.
- Vat photopolymerization encompasses SL and related processes, using various types of radiation including gamma rays, X-rays, electron beams, UV, and visible light to cure commercial photopolymers.
- Photopolymers are used in microelectronics industry for photomask materials, typically irradiated using far UV and electron beams, while dentistry predominantly uses visible light.
- Vat photopolymerization processes include vector scan, mask projection, and two-photon approaches, each with distinct configurations and applications.
- Vector scan and mask projection approaches require scanning laser beams, while the two-photon approach fabricates parts below the resin surface without the need for recoating.
- The vector scan SL machines and technologies are presented, followed by the presentation and contrast of mask projection approaches with the vector scan approach.
- UV-curable photopolymers, developed in the late 1960s, are used in a variety of applications including photoresists in the microelectronics industry, with critical requirements on accuracy and feature resolution.
- Various types of radiation sources, including gamma rays, X-rays, electron beams, UV, and visible light, can be used to cure commercial photopolymers, with UV and visible light being predominantly used in commercial systems.
- In SL systems, UV radiation is used exclusively, although other types could be used, and in mask projection DMD-based systems, UV and visible light radiation are used.
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Description
Learn about thermoplastic polymers, VP photopolymers, and SL resins, including their molecular structures and properties.
