"3D LAMINATING OF WOOD COMPOSITE PANELS Washington State University"
3D LAMINATING OF WOOD COMPOSITE PANELS Washington State University 39th International Wood Composites Symposium Jim Barnett Marketing Manager American Renolit Corporation email@example.com 3D Lamination • The history of thermoforming • Today’s end-market applications • The thermoforming process • Material choices and requirements – Membranes – Adhesives – 3D Laminates Thermoforming - History • Vacuum formers have been around since the 1960s but were used sparingly for simple edge routed parts • In 1988, a revolution began driven by the culmination of a few new technologies – MDF quality and availability – CNC routing – Water-based cross-linking adhesive systems – Rigid PVC films (5% or less plasticizer) – Pressure assisted thermoforming equipment Thermoforming - History • From a market demand side in the 90’s – White doors were again popular in kitchen and bath cabinetry – Painted white doors were problematic • Cracking paint at joints • Discoloration – A thermoformed door eliminated steps and labor required to make a typical 5 piece raised panel door Thermoforming - History • Early problems with 3D lamination – Films were prone to yellow when exposed to light • Poor film formulation • Natural rubber membranes interactions with films – Delamination due to poor gluing and pressing processes Today’s End-Market Applications Kitchen Cabinets Closet Systems Office Furniture 3D Laminate - Horizontal Durability Grade School Desk Seamless Table Tops Store Fixture, Display, Kiosks •Hospitality •Food Service •Health Care •Dorms •Casino Millwork Crown molding Basic Types of Presses • Vacuum formers • Membrane or bladder presses • Membraneless presses Vacuum Formers Heat source Membrane Film Seals Routed part Vacuum table Platform Membrane or Bladder Press Heat source Pressure inlet Seals Membrane Film Routed part Vacuum table Platform Membraneless Press Heat source Pressure inlet Seals Film Routed part Vacuum table Platform The Pressing Process • Parts are produced from MDF or HDF usually with panel saws and CNC routers The Pressing Process • Parts are sprayed with adhesive and dried (except for preapplied adhesive) The Pressing Process • Parts are placed in the press with pedestal or pins to lift off of the vacuum table • Parts are separated • by 2-3 finger width The Pressing Process • Film is pulled across the table covering seals • The film and parts are blown off to eliminate any loose fiber The Pressing Process • The cycle begins after the membrane is heated The Pressing Process • The press is sealed • Preheat (the film is softened) The Pressing Process • Pressure and vacuum are applied • Heat melts and activates the adhesive The Pressing Process • Cooling and press opening The Pressing Process • The press is opened and the parts are trimmed • The backs are buffed to remove any excess adhesive The Pressing Process Material Choices Membranes • Since membrane presses can be used for rigid thermofoil and veneers, it is important to choose membranes by the applications • Veneers can use natural rubber • Rigid thermofoil should use 100% silicone – Eliminating problems such as: • Migration of staining antioxidants from membrane • Migration of plasticizers from membrane • Interactions with rubber curing agents and PVC (sulfur staining) Material Choices - Adhesives • 2 Part Polyurethane Dispersions (PUD) • 1 Part Polyurethane Dispersions (PUD) • Preapplied Adhesives 2 Part Polyurethane Dispersions (PUD) • A two-part water-based sprayable adhesive is mixed • Water based polyurethane • Isocyanate catalyst (MDI) • The adhesive is sprayed onto parts using an HVLP gun • Edges are double sprayed • Tops are sprayed once • Parts are set in racks for about one hour to remove the water • Pot life is about 4-8 hours • A press temperature of 130 to 150ºF (depending on adhesive) kicks off catalyst in the adhesive • Full cure is reached after 24-28 hours with about 190ºF heat resistance 1 Part Polyurethane Dispersions (PUD) • A one-part water-based adhesive is used without mixing • The adhesive is sprayed onto parts using an HPLV gun • Edges are double sprayed • Tops are sprayed once • Parts are set in racks for about one hour to remove the water • Shelf life is several months under controlled conditions • A press temperature of 150-170ºF or more kicks off catalyst in the adhesive • Full cure is reached after 24-28 hours with a maximum of 190ºF heat resistance Preapplied Adhesives • Preapplied Adhesive – Blended polyolefin or polyurethane adhesive is applied to the back of the rolls of film – Typically 3 mils thick, some 2 mil versions – They melt and adhere at 150-170ºF – As a hot melt, the heat resistance equals the softening temperature Adhesive Choices Comparison 2 Part Catalyzed PUD 1Part Catalyzed PUD Preapplied hot melt Heat Resistance Consistently 190 Maximum 190 Maximum 160 (ºF) Application Mix and spray on-site Spray on-site Applied to film usually off-site Pressing 130ºF-150ºF to activate 145ºF-170ºF to activate 140ºF-170ºF to adhere Fatty Edge No No Yes Grain raise Yes Yes No Requirements for Good spraying technique, Good spraying technique, Good lamination to maximizing quality limited pot life limit storage time film Yield 100% 100% 55 to 70% Material Choices - Laminates Choices by End Use • Standard Vertical Grade Films – Solid colors, woodgrains, metallic and abstracts – Satin, medium and high gloss – Embossing • Horizontal Grade Films – Work surface durability • Improved scratch, mar, abrasion, impact and stain – Aesthetics of gloss and texture limited by use 3D Laminate Structure Typical solid color construction Opaque Rigid Film Layer Lacquer Primer 3D Laminate Structure Typical Printed Construction (woodgrain) Lacquer Transparent Film Ink Base Layer Primer Material Choices – Laminates Supply Chain Needs • Presser: needs to press the same every time – No appearance change from free film to pressed part – A defect free product (no pin holes, streaks, contaminates, flow) • Component and furniture makers/installers – Mar and scratch resistance – Color, gloss and texture consistency • End user – Durable, easily cleaned, scratch and stain resistant – Excellent color hold over a long life – Long lasting bond of laminate to the MDF/HDF part Presser Cabinet Home Installer Owner Maker Specifications For Pressers • Dimensional Stability • Embossing Retention • Color Consistency • Gloss Consistency Dimensional Stability • Dimensional Stability is tested after 10 minutes at 100ºC – Maximum film dimensional change • 5% shrinkage in the machine direction • 2% growth in the cross machine direction Embossing Retention • IVK Standards: – Embossing stability after 10 minutes at 120ºC • No change in gloss or embossing depth • LMA – 3D Laminates: voluntary standards – Embossing retention after 10 minutes at 100ºC • No change in gloss or embossing depth Embossing stability Ro.3 Ro.2 Tolerance Ro.1 0 10 20 30 40 50 Gloss 60° 130°C 100°C Tolerance 75°C 70°C 0 10 20 30 40 50 60 Gloss 60° Color Consistency • Solid Colors – ASTM E-1164/D-2244 • DE ≤ 0.50 – DIN 6174 • DE ≤ 0.50 • DL ± 0.3 • Da ± 0.2 • Db ± 0.3 • Prints – Visual matches to standards Color and Design Consistancy solid colour: max. 0.5 DE woodgrain: visual produced May 00 produced March 01 produced October 01 produced June 02 Gloss Consistency • DIN 67530 (60º geometry) – Gloss 0-15 Tolerance: ± 2 – Gloss 16-30 Tolerance: ± 3 – Gloss 31-50 Tolerance: ± 5 – 51 and higher Tolerance: ± 7 • ASTM D-523 (60º geometry) – Gloss ≤ 30 Tolerance of ± 3 – Gloss > 30 Tolerance of ± 5 Specifications For End Users • Light fastness • Chemical resistance • Scratch resistance • Abrasion resistance • Heat resistance Light Fastness • The resistance of films to color change and degradation due to interior weathering has multiple tests – DIN 53387 2-F: 1200 hours of Xenon Arc exposure behind window glass with 50% dark time and 40-60% humidity • CIELab ΔE < 1.7 • ISO 105 B02: Gray scale ≥ 6 Anti-yellowing Formulation Lightfastness Accelerated Testing Original color mastersample after 300 hours color variation: 0.8 DE after 600 hours color variation: 1.9 DE after 1200 hours color variation: 2.9 DE color variation: 0.9 DE Chemical Resistance • Defined by the end use markets – General use testing: DIN E-12720 – Office furniture: NEMA LD3 2000 3.4 – Kitchen: ANSI/KCMA 161.1 2000 Reagent IVK: DIN E-12720 LD3-2000 3.4 ANSI/KCMA 161.1 2000 10% acetic acid/vinegar Yes Yes 4.4% acetic acid Yes 10% citric acid/lemon juice Yes Yes acetone Yes Yes 10% ammonia solution Yes grape juice Yes blackcurrent juice Yes citric acid Yes cleansing agent Yes coffee (from instant) Yes Yes Yes 0.5% phenol disinfectant Yes 2.5% p-toluene sulphone chloramide sodium Yes endorsing ink Yes 96% ethanol Yes 48-50% ethanol Yes Yes Yes 1:1 ethyl-butyl acetate Yes condensed milk (10% fat) Yes olive or cooking oil Yes Yes Yes paraffin oil Yes sodium carbonate Yes 15% sodium chloride Yes 5% sodium chloride Yes tea (10g/l) Yes Yes deionized water Yes Yes detergent solution (0.5% hand soap) Yes catsup Yes Yes yellow mustard Yes 10% Povidone iodine (betadine) Yes permanent marker pen Yes #2 pencil Yes wax crayon Yes shoe polish Yes Scratch Resistance • LMA: Hoffman Scratch Tester – 200 g, 1 inch per second – Method only, results are recorded • DIN 53799: Erichson Tester – Result: 4D (≥ 1.5 Newtons) Scratch Testing Equipment Abrasion Resistance • LMA: ANSI/NEMA LD-3 2000 3.13 – Taber abrasion with results as follows: • Weight loss at 100 cycles • Cycles to failure (e.g. print loss) • IVK: DIN68861 Part 2 Heat Resistance • KCMA 9.1: Door Test – Heat resistance – 24 hours in a 120ºF, 70% RH hot box – Pass if no delamination, discoloration or surface blistering, checks or other film failure • KCMA Door Test – Temperature cycle – 5 cycles of 1hour at 120ºF followed by 1 hour at -5ºF. – Pass if no delamination, discoloration or surface blistering, checks or other film failure KCMA Heat Resistance Example of Delamination Significant Failure: Oven with air circulation 24 hours at 120°F Heat resistance –Failure Point Testing after 1h in heat circulation oven at 60°C +1h 70°C +1h 80°C +1h 90°C +1h 100°C +1h 110°C In Summary • Thermoforming encompasses many variations – equipment – process – materials • Matching these variations to the needs of the presser and end market is critical to success Special Thanks to the following for information and content: • Stiles Machinery / Wemhöner Press • Jowat Adhesives • Daubert Chemical