Fabricating with Foam Models Materials and Methods Orthotic

Fabricating with Foam Models: Materials and Methods Orthotic and Prosthetic Devices To take full advantage of the learning opportunities presented in this resource, Internet access is recommended. Also, view the presentation in “Slide Show” mode. Click on the “Slide Show” tab in your Microsoft® Power. Point® tool bar, then click on the “From the Beginning” tab. As an alternative, you may press the F 5 key as a shortcut to begin the presentation.

OVERVIEW Below are the sections of the presentation. Review the sections in the order they are presented or click on a section heading to navigate directly to that section. In-House vs. Outsource (This presentation assumes in-house carver and in-house fabrication) Foam Thermoplastics Textiles Chemicals Fabricating Over Foam Models: Thermoforming Knowledge Check

Home IN-HOUSE vs. OUTSOURCE IN-HOUSE CARVER IN-HOUSE FABRICATION OUTSOURCE CARVER IN-HOUSE FABRICATION Obtain digital image (Scanner) Make modifications (Software) Order foam blanks for Carver; Central Fabrication (C-FAB) facility may be the supplier Send digital CAD file to Central Fabrication (C-FAB) facility CAM: Carver takes digital CAD file and uses foam blanks to carve and produce positive model CAM: C-FAB facility receives digital CAD file and uses foam blanks to carve and produce positive model; sends foam model to your facility Determine materials and methods needed for fabrication Prepare foam model for fabrication

Home FOAM

Open- vs. Closed-Cell Foams OPEN-CELL FOAM CLOSED-CELL FOAM Pores are connected to form an interconnected network, which allows air to flow between the cells. Pores are not interconnected, but instead “piled” together. When air fills the space, the foam becomes soft. Bubbles of trapped air are surrounded by cell walls, making the foam more rigid. Breathable, soft, spongy. Lightweight and washable. Low Density: ½ to ¾ of a pound per cubic foot. Medium Density: 2 - 3 pounds per cubic foot. Absorbs moisture. Does not absorb fluids/moisture. Resistant to compression deformation. Susceptible to compression. One of the most common open-cell foams used in O&P is Poron®. It is a polyurethane foam that is compression-set resistant, fungal resistant, and breathable. Typical applications for Poron in the O&P field include custom and prefabricated orthoses, prosthetic padding, and biomechanical supports. Foam blanks for carving are made out of urethane and polyurethane. Polyurethane is lightweight, odorless, and will not absorb water. It has both rigid and flexible forms. Typical applications in the O&P field include not only foam blanks but also shockabsorbing materials and flexible foams.

OPTIONS FOR FOAM CARVING BLANKS Urethane, Polyurethane Block Tubular Oval Ovoid Trapezoid Custom BK AK TLSO AFO FO MATERIAL SHAPE DENSITY 2 lb. 4 lb. 6 lb. OPTIONS PURCHASE DEVICE SIZE Height, Width, Depth Singular, Box of multiples

OPTIONS: VENDOR DESCRIPTIONS BLOCK, AK MEDIUM 165 mm X 255 mm X 445 mm …Our prosthetic blocks have an average density of 7. 0 pounds per cubic foot while our orthotic blocks average 6. 0 pounds per cubic foot. This density provides you with a block that will stand up to the temperatures and pressures of vacuum forming thermoplastics used in the O&P industry… Source: Friddle's Orthopedic Appliances, Inc. BLANK STANDARD BK TRANSTIBIAL 8 cm x 16 cm (20 in. x 40 in. ); Dense urethane foam; Convenient, cost effective, lightweight carving medium; Manufactured to withstand the rigors of thermoforming or laminating; Hazmat: No. Source: SPS CARVING BLANKS …Unique foam makeup that maintain shape during the high temperatures and pressures created during lamination and vacuum processes. The distinctive foam composition has a 90% closed cell structure resulting in no voids or air pockets in the foam. The foam has more dimensional stability over a broad range of operating temperatures. Source: The Ohio Willow Wood Company

Conversion Chart When ordering foam carving blanks, sizes may be quoted in centimeters and/or inches. For example, a description may state that the foam is 16” x by 8” or that it is 40. 6 cm x 20. 3 cm. If it does not provide the conversion, use a conversion resource as a quick reference guide to convert centimeters to inches and inches to centimeters. The following Web sites provide conversion calculation: § Metric Conversions: Metric Conversions Centimeters to Inches. http: //www. metric-conversions. org/length/centimeters-to-inches. htm. § Manuel’s Web: The link follows: Manuel’s Web. http: //www. manuelsweb. com/in_cm. htm.

Home THERMOPLASTICS

THERMOPLASTICS Plastic materials (polymers) that soften when heated and harden when cooled. They can be remolded and reshaped to accommodate changes or pressure areas. Thermoplastics provide many benefits because they are lightweight, durable, easy to fabricate, water resistant, easily adjustable, and recyclable. Typically sold in sheets, thermoplastics are available in many thicknesses, strengths, colors, and finishes.

Thermoplastic vs. Thermoset THERMOSET PROCESS THERMOPLASTIC PROCESS Chemical bonding takes place. Polymers form an irreversible chemical bond when heated. The material will not re-melt when heat is applied. Materials are heat and deformation resistant, and tend to be strong and brittle. No chemical bonding takes place. Polymers soften when heated but can be remolded and recycled without affecting the material’s properties. Materials tend to be high strength, shrink resistant, chemical resistant, and easily bendable. PROS CONS Hard crystalline or rubbery surfaces Generally more expensive than thermoset Can be remolded and reshaped to accommodate changes or pressure areas Can melt if heated Recyclable VS. PROS CONS Generally less expensive than thermoplastic Somewhat difficult to surface finish High level of dimensional stability Cannot be remolded or reshaped Good for high-heat applications; Resistant to high temperatures Cannot be recycled

TYPES OF THERMOPLASTICS § Acrylic § Polyethylene (PE)—typically categorized by their densities: • Low density (LDPE) • Medium density (MDPE) • High density (HDPE) • Ultra-high density (UHMWPE) § Polypropylene (PP)—one of the most rigid thermoplastics § Polyvinyl Chloride (PVC) § Co-polymer—a blend of polypropylene and 5% to 10% of LDPE § Polystyrene § Acrylonitrile Butadiene Styrene (ABS) § Nylon § Polyethylene terephthalate glycol-modified (PETG) § Proflex/Proflex with Silicone

ATTRIBUTES OF COMMONLY USED THERMOPLASTICS Polypropylene Rigid, strong, impact and fatigue resistant, no moisture absorption, self adhesive Modified Polyethylene In between co-polymer and LDPE Surlyn® Minimal rigidity, flexible, vacuum formable Co-polymer Good formability, rigid yet flexible, self adhesive PETG (Vivak®) Transparent color, tough, hard, easy to bond and fabricate Sub. Ortholen® High molecular weight HDPE, flexible, tough polymer, more durable than Ortholen LDPE Soft, flexible, low tensile strength, easy formability Polycarbonate High impact strength, durable Proflex Rubber-like ethylene based, durable, flexible HDPE Ortholen® Durable, flexible, strong, resistant Tough, corrosion resistant, does not to impact, lightweight become brittle or absorb perspiration Proflex with Silicone Very flexible, minimal rigidity, flexible

PROPERTIES OF COMMONLY USED THERMOPLASTICS Homopolymer Polypropylene SURFACE: Smooth FLEXIBILITY: Very little RIGIDITY: Very rigid IMPACT STRENGTH: Reasonable to Poor *HEATING TEMPS: 325 – 350 0 F COMMON USES IN O&P: Body jackets, ankle foot orthoses (AFOs), definitive sockets Low Density Polyethylene (LDPE) Colyene Co-Polymer SURFACE: Smooth FLEXIBILITY: More flexible than Homopolymer Polypropylene RIGIDITY: Semi-rigid to rigid IMPACT STRENGTH: Very good *HEATING TEMPS: 300 – 350 0 F COMMON USES IN O&P: Helmets, definitive sockets, body jackets, splints Modified Polyethylene PETG (Vivak®) SURFACE: Smooth FLEXIBILITY: Minimal RIGIDITY: Very rigid IMPACT STRENGTH: Very brittle *HEATING TEMPS: 250 – 300 0 F COMMON USES IN O&P: Face masks, check sockets, burn management, upper limb static orthoses High Density Polyethylene (HDPE) SURFACE: Smooth FLEXIBILITY: More flexible than Homopolymer Polypropylene RIGIDITY: Moderate IMPACT STRENGTH: Very good *HEATING TEMPS: 325 – 350 0 F SURFACE: Smooth FLEXIBILITY: More flexible than Homopolymer Polypropylene RIGIDITY: Semi-rigid IMPACT STRENGTH: Very good *HEATING TEMPS: 270 – 330 0 F SURFACE: Smooth FLEXIBILITY: More flexible than Modified Polyethylene RIGIDITY: Semi-rigid IMPACT STRENGTH: Very good *HEATING TEMPS: 325 – 350 0 F COMMON USES IN O&P: Pediatric AFOs, splints, flexible socket interfaces COMMON USES IN O&P: Spinal orthoses, COMMON USES IN O&P: May be used in interim type of upper and lower limb place of Polypropylene; tends to crack orthoses under stress

THERMOPLASTICS COMMONLY USED IN O&P DEVICES HEAD and FACE DEVICES: Polypropylene, Co-polymer, PETG, Polycarbonate NECK and SPINE DEVICES: Polypropylene, Co-polymer, Modified Polyethylene SPINAL DEVICES: Polypropylene, Co-polymer, LDPE, HDPE, Modified Polyethylene, Kydex®, ABS UPPER and LOWER LIMB DEVICES: Polypropylene, Co-polymer, LDPE, HDPE, TPE, PETG, Proflex with Silicone ANKLE and FOOT DEVICES: Polypropylene, Co-polymer HDPE, TPE, Acrylic, Acetal KNEE DEVICES: Polypropylene, Copolymer Image Source: Pixabay. com. Public Domain. CC 0.

Home TEXTILES

TEXTILES Textiles have numerous uses within the O&P field. The lamination process for orthoses and prostheses, for example, involves the saturation of reinforcement textiles with a resin. A reinforcement textile is a fabric/fiber, such as fiberglass, nylon, cotton, Dacron®, carbon, and Kevlar®, used to provide strength. The strength of the laminate is determined by the material properties of the fiber and the resin. Important properties to consider include stress, strain, stiffness (Young’s Modulus), ultimate tensile strength (UTS), yield strength, brittleness and ductility.

Types of Textiles Perlon® Stockinette Used for socket laminations, AFOs, KAFOs, KOs; compatible with all types of resins; superior elasticity; smooth appearance. Nyglass Stockinette Used for sockets that need to be lightweight and thin, socket laminations, AFOs, KOs; combines the lightweight strength of fiberglass with the elasticity of nylon. Nylon Stockinette Used for socket laminations—TF and TT; nylon fibers add durability to artificial limbs and other orthotic devices. Basalt Braid Used for composite sockets and AFOs, plastics reinforcement; tough, durable, strong, lightweight, superior resin saturation. Dacron Straps Used for arm harnesses and as reinforced strapping. Strong, durable. Resists elongation under tension. Dacron Felt Used in laminations as “base” layer/inner surface of a lamination, on the outside of the sockets for lining and padding, around trim lines; provides extra material inside of socket for grinding out reliefs without sacrificing integrity of the reinforcement material; provides little strength. Carbon Fiber Braid Used for strong, lightweight layups, reinforcement for laminated devices, prosthetic sockets; lightweight, strong, conforms to irregular shapes. Fiberglass Tapes and Sleeves Used for reinforcement and wrapping applications to cover small areas or unique shapes; compatible with polyester, vinyl ester, and epoxy resins. Velcro® As a hook and loop fastener, used for attaching straps or padding to hard-surface materials, such as splints and braces.

Home CHEMICALS

Types of Chemicals CHEMICAL STYRENE A colorless liquid consisting of carbon and hydrogen; can have an odor. Primarily a synthetic chemical. ACETONE A colorless, volatile liquid with a mint-like odor. Moderately aggressive. USES for O&P DANGERS Used to make plastics, rubbers, and resins. Also used as a filler or thinner and reactive cross-linker to polyester resins. Regarded as a hazardous material and possibly a carcinogen. Possible irritation to the eyes, nose, respiratory system, central nervous system, liver, reproductive system. Used as a solvent for plastics and Slight toxicity in normal use. Highly synthetic fibers, a thinner to flammable. Not regarded as a carcinogen. polyester and epoxy resins, and to Possible irritation to the eyes, nose, synthesize Bisphenol A (BPA), a throat, respiratory system, central chemical found in hard plastics nervous system. Considered safer and epoxy resins. less toxic than toluene solvents. TOLUENE Used as a solvent. Resembles Benzene, a colorless and highly flammable liquid with a sweet smell. Harmful vapor/fumes. Flammable. Possible irritation to the eyes, nose, respiratory system, central nervous system, liver, kidneys. METHYL KETONE (MEK) Used as a thinner for polyester and epoxy resins. Used when an evaporation slower than acetone is desired. Water soluble. Harmful vapors/fumes. Flammable. Possible irritation to the eyes, nose, respiratory system, skin, central nervous system, mucous membranes. A colorless liquid with an aromatic Benzene-like odor. A colorless liquid with a sharp, sweet alcohol-like odor. Also known as Butanone.

Chemicals Below is an overview of two types of thermosetting resins commonly used in the O&P field. Attributes to consider when comparing and selecting resins to use in any given situation include ease of use, cost, degree of possible toxicity, strength and flexibility, degree of adhesion, shrinkage, cure time, and shelf life. ACRYLIC RESINS Produced from methyl methacrylate (MMA) and dissolved polymethyl methacrylate (PMMA). Hardness can be adjusted for various applications. More water resistant than polyester resins. Bonds to core materials better than polyester resins. Shrinks less than polyester resins on curing. More expensive than polyester resins; less expensive than epoxy resins. VS. EPOXY RESINS Thermosetting polymer combined with hardeners. Also known as a polyepoxide. High tension strength. Greater flexibility than polyester resins. Better than polyester resins for high-strength bonding. Does not contain styrene. Reinforces glass and carbon materials. Very little shrinkage. Able to bond dissimilar and already cured material. Longer cure time than polyester resins. More expensive than acrylic resins and polyester resins.

Chemicals: Dust Particles Working with carbon fiber and metals adds dust particles and other abrasive elements into the air. They are by-products of the manufacturing process. Sanding and grinding create more fine dust than cutting. Depending on the material, particle size and concentration, and exposure time, dust can cause a variety of health problems. Images Source: Pixabay. com. Public Domain. CC 0. GOALS: Reduce dust infiltration for health reasons and minimize/eliminate the possibility of combustion. A cloud of dust can cause an explosion. Even materials that do not burn in larger pieces (such as aluminum or iron) can explode in dust form, given the proper conditions. The risks associated with working around dust particles can be managed/minimized. SOLUTIONS: Proper ventilation and airpurifying systems Proper and frequent training for best practices Proper collection systems Use of masks and respirators, especially when cutting, grinding, and sanding materials

Chemicals: Protection TYPES OF PROTECTION FROM CHEMICALS AND DUST: E! VIC D A D OO nd of e e h t at oughly eating and r o h t ior to hands Wash ivity and pr ct each a. ive rotect ng p l a n drinki rso ate pe clothing to i r p o r p. d Use ap ent (PPE) an nd the face a , m equip hands, eyes g t clothin k r o protec w any r wet o e c d a l e t p a min ve/re Remo omes conta ds. ec ui that b mmable liq la tilated n from f e v y l er a prop n i k r Wo ts ment. n o r a Shee i t v a D en y et ial Saf case of r e t a e Keep M available in ovide a wid t ) rs pr ding fi nd (MSDS ncies. They u l c n i , a e n, emerg informatio e elements f v o ti range tment, reac s. a e aid tre ting measur h fire fig G • Rubber or plastic gloves and sleeves protect against heat and abrasion. Consider a heat insulating terrycloth or leather glove. • Simple protective glasses can protect against flying dust and small particles. A face shield provides additional coverage and may be necessary when dealing with caustic fluids. • Proper ventilation can dramatically control the amount of dust and other particles in and around a work area. • A filtration mask/device may be necessary when working close to the source of dust or chemical. Images Source: Pixabay. com. Public Domain. CC 0.

Home FABRICATING OVER FOAM MODELS: Thermoforming

Thermoforming Over Foam Models NOTE: The following provides tips, methods, and suggestions for preparing the model. Methods vary among professionals and are not meant to be absolute or all-inclusive. Apply two layers of stretch nylon over the model. Also, for AFOs and other irregularly shaped models, staple a piece of 2” cotton stockinette from your vacuum source to the end of the model outside of the finished trim lines (this will act as a wick), and finally wet the entire model before forming. Pull a layer of stockinette and then a layer of nylon over the mold. Then, either dip the whole model in water, or use a spray bottle to saturate the textiles. The trick is to have enough moisture to prevent the plastic from sticking to the mold, but not so much as to cause steam bubbles. Seal the foam model with fast curing resin using a hand “washing” technique. Wear two pairs of gloves. Pour promoted resin into the palm, and spread it over the foam model. Go easy on the promoter or the layer will crack from the heat. You can add fillers such as microballoons or Solka-Flok® to create a putty, let it cure, and smooth with sanding screen. Source: www. oandp. com. E-mail message board OANDP-L: 2/03/2009 “Pulling Plastic Over Foam Molds. ” Reply excerpts have been abstracted.

Thermoforming Over Foam Models continued Forming over polyurethane foam requires the following: oven (uniform controlled heat), fractional melt index plastic, heat-resistant proper density foam, non-stick two-layer very wet fine weave stockinette, mold preparation, instant vacuum. Use electrical conduit pipe to hold the AFO cast. Flatten the end, then split the end into a fork. Hammer this into the cast to hold it for vacuuming. Use stockinette and sew up the end, then soak in water. Once soaked, pull over the cast. Apply four layers of nylon hose. If forming joints into the device, apply these, then cover with another layer of nylon. Use a spray bottle and spray water onto the textiles until they are just dripping water. Then pull plastic. Do not use too much water. Source: www. oandp. com. E-mail message board OANDP-L: 2/03/2009 “Pulling Plastic Over Foam Molds. ” Reply excerpts have been abstracted.

Thermoforming Over Urethane Foam Models Q/A with Roger Wagner, Prosthetic Practitioner Instructor, Century College, White Bear Lake, Minnesota Urethane Model Compression (Reduction) and/or Thermoplastic Shrinkage SITUATION: 1. Can (or does) the presence of heat and negative pressure during the vacuum-forming process lead to unwanted compression of the foam model? 2. Can (or does) compression also occur to positive models, depending on the type and thickness of thermoplastic being used?

Thermoforming Over Urethane Foam Models continued Q. Do you “upsize” the model prior to the forming process to maintain the desired fitting dimensions of the interface? A. Prosthetically, we do not upsize the model. You would sacrifice your original design and shape by doing any upsizing of the model. We modify the model, carve the model and, if possible, roll the liner onto the model, and pull the test socket directly over the carve and the liner. If you use a liner that is not heat tolerant, then re-cast the liner over the model, fill that with plaster and pull the test socket that way. Q. Discuss what, if any, model compression issues you have experienced and how one can safeguard against it. A. We have not experienced any shrinkage issues with the models. We use the dense foam blanks, the hardest available. Perhaps the softer ones shrink. It’s my opinion that upsizing the model for shrinkage would be guesswork and I would not do it or recommend doing that type of modification. Certain plastic can shrink if you cut them off too quickly, but I still would not upsize the model. I would allow the plastic to cool properly. Q / A with Roger Wagner, Prosthetic Practitioner Instructor, Century College, White Bear Lake, Minnesota

Thermoforming Over Urethane Foam Models continued Q. Do you use any mold release agents, such as power or silicone spray? A. Prosthetically, we use Trans-tibial Vivak®, leaving the cellophane on the inside of the model-drape molding with cornstarch and no nylon. This provides a smooth clear inner surface (heat at 340 degrees). Use Trans-femoral Vivak nylon over the distal end, drill air holes down to the distal end and under the ischial seat, and cover with cornstarch. This provides a smooth clear inner surface (heat at 340 degrees). Q. What are you doing to prepare the urethane CAD model for thermoforming process, if anything, such as use a nylon sock(s) and/or a PVA bag over the model? A. Orthotically—With thermoplastics, we use a nylon sock with cornstarch as a separating agent. For TLSO, the same, no PVA bags, silicone sprays, or water. Q. Do you cool down the model before thermoforming process either with water or refrigeration? A. No, we don’t cool down the model or the plastics. We let them cool down to room temperature. Q / A with Roger Wagner, Prosthetic Practitioner Instructor, Century College, White Bear Lake, Minnesota

Home REVIEW—KNOWLEDGE CHECK: Test your knowledge of the material with the following questions. Click for the correct answer and to proceed to the next slide.

REVIEW—KNOWLEDGE CHECK: 1. Does the following statement describe an open-cell or closed-cell foam? Pores are not interconnected but instead are “piled” together. Answer: Closed-cell foam. 2. Does the following statement describe thermoset or thermoplastic process? No chemical bonding takes place; can be remolded and reshaped to accommodate changes or pressure areas. Answer: Thermoplastic process.

REVIEW—KNOWLEDGE CHECK: 3. HDPE stands for: Answer: High density polyethylene 4. Does the following statement describe an acrylic or an epoxy resin? Also known as a polyepoxide; high tension strength; does not contain styrene; thermosetting polymer combined with hardeners. Answer: Epoxy resin.

REVIEW—KNOWLEDGE CHECK: 5. True or False: A cloud of dust can cause an explosion. Answer: True. Even materials that do not burn in larger pieces (such as aluminum or iron) can explode in dust form, given the proper conditions.

REVIEW—KNOWLEDGE CHECK: 6. Fiberglass, nylon, cotton, Dacron, carbon, and Kevlar are all examples of: Answer: Reinforcement textiles.

REVIEW—KNOWLEDGE CHECK: 7. Options to consider when ordering foam carving blanks include (6 responses, in no particular order): Answer: Shape of the blank Device the blank will be used for Size of the blank Material blank is made of Density of the foam How many to purchase (singular or box, for example)

References, Resources, and Acknowledgements Home This workforce product was funded by a grant awarded by the U. S. Department of Labor’s Employment and Training Administration. The product was created by the grantee and does not necessarily reflect the official position of the U. S. Department of Labor. The U. S. Department of Labor makes no guarantees, warranties, or assurances of any kind, express or implied, with respect to such information, including any information on linked sites and including, but not limited to, accuracy of the information or its completeness, timeliness, usefulness, adequacy, continued availability, or ownership. Produced 2016. HOPE Careers Consortium is a partnership of five institutions of higher education that is building exciting new programs that will provide valuable career education and training in the Orthotics, Prosthetics, and Pedorthics (O&P) sector. The five institutions are: Baker College—Flint, Michigan; Century College—White Bear Lake, Minnesota; Oklahoma State University Institute of Technology—Okmulgee, Oklahoma; Spokane Falls Community College—Spokane, Washington; and St. Petersburg College—St. Petersburg, Florida. Although the authoring institution of this educational resource has made every effort to ensure that the information presented is correct, the institution assumes no liability to any party for any loss, damage, or disruption caused by errors or omissions. Except where otherwise noted (e-mail message board comments and images from Pixabay. com), this work by Oklahoma State University Institute of Technology (OSUIT) is licensed under the Creative Commons Attribution 4. 0 International License. To view a copy of this license, click on the following link: Creative Commons Licenses 4. 0. Dacron is a registered trademark of Du. Pont. Kevlar is a registered trademark of Du. Pont. Ortholen is a registered trademark of Teufel Orthopedic / Wilhelm Julius Teufel. Perlon is a registered trademark of Perlon -Monofil GMBH. Sub. Ortholen is a registered trademark of Teufel Orthopedic. Surlyn is a registered trademark of Du. Pont. Velcro is a registered trademark of Velcro Industries B. V. VIVAK is a registered trademark of Sheffield Plastics Inc. Solka-Flok® is a registered trademark owned by Nordic Sugar. Microsoft and Power. Point are either registered trademarks or trademarks of Microsoft Corporation in the United States and/or other countries.