Enhancing the Bonding of Dissimilar Materials with Plasma. Andy Stecher Plasmatreat North America

Transcription

1 Enhancing the Bonding of Dissimilar Materials with Plasma Andy Stecher Plasmatreat North America

2 Key Take-Aways Materials joining in manufacturing of lightweight, often dissimilar substrates present technical challenges. Surface conditioning prior to bonding dissimilar materials enables better adhesion. Plasma cleans surfaces by removing surface contaminants and activates surface chemistries - eliminating primers. Plasma stabilizes manufacturing bonding processes. Plasma coatings modify surfaces to provide corrosion protection, and improves or inhibits adhesion.

3 About Plasmatreat Subsidiaries and distribution partners worldwide in 34 countries Germany Steinhagen Birkenfeld China Shanghai Guangdong - Dongguan Japan Tokyo Osaka USA & Canada Elgin Belmont Ancaster Singapore Great Britain London France Paris Spain Barcelona Italy Venice Turkey Istanbul Author, Plasmatreat GmbH 3

4 About Plasmatreat PlasmaTreat tm North America Inc. is part of PlasmaTreat Worldwide operating in 34 countries with 15 subsidiaries and over 200 employees. North America with three locations: Toronto, Ontario; San Francisco, CA and Chicago, IL. Breakthrough Openair tm plasma technology introduced to industry in 1995, patented worldwide in more than 100 international patents Over 6,000 Systems with more than 20,000 Plasma Jets in Service. Automotive, Aerospace, Medical, Electronics, and other highperformance applications.

5 Outline 1. Industry Trends and Motivation 2. Surface Conditioning and Adhesion 3. Plasma Composition and Generation 4. Surface Cleanliness and Activation 5. Process Measurement 6. PlamaPlus Coating 7. Important Results

6 1. Industry Trends and Motivation 2. Surface Conditioning and Adhesion 3. Plasma Composition and Generation 4. Surface Cleanliness and Activation 5. Process Measurement 6. PlamaPlus Coating 7. Important Results

7 Industry Trends & Motivation Top Challenges to Achieve Fuel Efficiency / Emission Standards

8 Industry Trends & Motivation Weight reduction involves substituting lightweight materials such as aluminum, alloys, composites and plastics for steel.

9 Industry Trends & Motivation Without the use of bonding technology, modern lightweight designs would hardly be feasible especially when it comes to bonding dissimilar and/or new materials. Dr. Andreas Gross, Fraunhofer IFAM

10 Industry Trends & Motivation Source: EWI 2010

11 Industry Trends & Motivation Adhesion to combinations of difficult substrates Unequal thermal expansion coefficients Galvanic reactions between dissimilar metals How to uniformly distribute mechanical stresses Paintability of mixed assemblies Source: Mix and Match for Lightweight Autos, Manufacturing Engineering, September 2014

12 Industry Trends & Motivation Steel is easy To Clean To Bond To To Paint

13 Industry Trends & Motivation Compared with metals, plastics have low surface energy Surface energy in mj/m 2 Source: Permabond Engineering Adhesives

14 Industry Trends & Motivation

15 1. Industry Trends and Motivation 2. Surface Conditioning and Adhesion 3. Plasma Composition and Generation 4. Surface Cleanliness and Activation 5. Process Measurement 6. PlamaPlus Coating 7. Important Results

16 Surface Conditioning & Adhesion According to Sherwin- Williams, 80% of coating failures can be tied to inadequate surface preparation. Source:

17 Surface Conditioning & Adhesion Covalent Bonding Mechanical Any contamination that comes between the ink, coating or adhesive and the substrate surface will weaken the bonding forces

18 Surface Conditioning & Adhesion Weldon (2009): Surface preparation is a critical factor in obtaining good adhesion. Soils and other contaminants inhibit adhesion through though both chemical and physical pathways. By reducing the influence of intermolecular forces between the surface and the applied material, or by blocking sites that provide an opportunity for physical anchoring. Schuman and Thames (2005): A variety of important coating properties such as hardness, scratch resistance, chip resistance and gloss are affected by the underlying surface s cleanliness, hardness, smoothness and chemical bonding to the coating.

19 Surface Conditioning & Adhesion Davis (1993): Contamination is one of the most insidious factors affecting adhesive bond performance

20 1. Industry Trends and Motivation 2. Surface Conditioning and Adhesion 3. Plasma Composition and Generation 4. Surface Cleanliness and Activation 5. Process Measurement 6. PlamaPlus Coating 7. Important Results

21 Surface Conditioning & Adhesion Plasma: Cleans Activates Coats Prior to: Printing Decorating Bonding On: Plastics Glass Metal Ceramic

22 Plasma Composition & Generation

23 Plasma Composition & Generation Adding energy to oxygen breaks apart the O 2 molecules, and then the oxygen atoms themselves, to produce a number of reactive species:

24 C O O N * * * * N N O N N N O N O O N O * * * H H H H H H H C C C C C C C H H H H H H H Cleaning Effect Plasma Composition & Generation

25 Plasma Composition & Generation Generator Transformer Plasma Jet

26 Plasma Composition & Generation OPENAIR Plasma Jet High voltage Current Ionization Gas Cathode Discharge Chamber Plasma Beam Substrate

27 Plasma Composition & Generation OPENAIR Plasma Jet RD 2004

28 Plasma Composition & Generation Aurora LC

29 Plasma Composition & Generation Aurora LC

30 Plasma Composition & Generation Openair plasma is routinely used for 3-dimensional, contoured surfaces using fixed automation or 6-axis electronic robots.

31 1. Industry Trends and Motivation 2. Surface Conditioning and Adhesion 3. Plasma Composition and Generation 4. Surface Cleanliness and Activation 5. Process Measurement 6. PlamaPlus Coating 7. Important Results

32 Surface Cleanliness and Activation External Surface Contamination Internal Surface Contamination Oil Slip Agents, Waxes Antioxidants Crosslinkers Fingerprints Contamination Dust Contamination Pigments Fillers Grease UV Modifiers

33 Mechanical Wet Chemical Physical Surface Cleanliness and Activation Surface Modification Options Scuff Sand Blast Cleaner Solvent Primer Flame Corona Plasma

34 Surface Cleanliness and Activation Organic solvents used to dissolve contaminants are well known to pose some significant health, safety and environmental risks. Courtesy Texas A&M University

35 Mechanical Wet Chemical Physical Surface Cleanliness and Activation Surface Modification Options Scuff Sand Blast Cleaner Solvent Primer Flame Corona Plasma

36 Surface Cleanliness and Activation ANTEC 2013

37 Surface Cleanliness and Activation Differences in coefficients of thermal expansion constrain the use of high temperatures for many applications where expansion causes dimensional tolerance issues or mechanical stresses/ thermal shock Source: Permabond Engineering Adhesives

38 Surface Cleanliness and Activation Dry No thermal impact Touchless Avoids penetrating or impacting the bulk matrix No Waste

39 Oxygen Containing Plasma Surface Cleanliness and Activation Plasma from oxygen (present in air) react with organic materials to form harmless carbon dioxide and water: Organic Contaminants

40 Percent of Carbon Surface Cleanliness and Activation Before Plasma Cleaning After Plasma Cleaning Baseline Carbon Level Depth, Angstroms Source: Shun ko & Belkin, 2007

41 Surface Cleanliness and Activation XPS spectra Courtesy, BTR Labs

42 Surface Cleanliness and Activation XPS spectra Courtesy, BTR Labs

43 Surface Cleanliness and Activation - Waxes - Thicker film oils - Denser Contamination - Inorganic Contamination

44 Surface Cleanliness and Activation - Waxes - Thicker film oils - Denser Contamination - Inorganic Contamination Openair Plasma + Compressed Process Gas

45 Surface Cleanliness and Activation - Waxes - Thicker film oils - Denser Contamination - Inorganic Contamination Openair Plasma/Laser

46 Surface Cleanliness and Activation Surface treatment using Plasma and Laser Hybrid Technology is unprecedented. A new global patent for surface cleaning.

47 C O N C C C C C C C H H H H H H H H H H H H H H O O O O O O N N N N N N N * * * * * * * Activation Effect Surface Cleanliness and Activation

48 Surface Cleanliness and Activation Atmospheric Pressure Plasma Process - Activation Activation results in the formation of Oxygen functional groups(e.g. Carbonyl, Hydroxyl) as well as Nitrogen functional groups (e.g. Nitrate) C - C Binding Energy (ev) PP: untreated (surface free energy: 27,0 mn/m) C = O O = C - O C - OH C - O - C C - C Binding Energy (ev) 2,5 2,4 2,3 2,2 2,1 2,0 NO 3 NO PP: Openair tm Plasma treated (surface free energy: up to 72 mn/m) 2 NO NOH Binding Energy (ev) Courtesy: Fraunhofer Institute for Processing Technology and Materials Research

49 Surface Plasma Cleanliness surface treatment and Activation effects Atomic Force Microscopy Study on PET 1 m Surface roughness decreased, actual surface area increased by 30% UNTREATED PLASMA TREATED Fraunhofer Institut Fertigungstechnik Materialforschung

50 1. Industry Trends and Motivation 2. Surface Conditioning and Adhesion 3. Plasma Composition and Generation 4. Surface Cleanliness and Activation 5. Process Measurement 6. PlamaPlus Coating 7. Important Results

51 Process Measurement Contaminated and low energy surfaces cause water to bead up and do not wet out.

52 Process Measurement Handheld easy-to-operate yet accurate and reliable contact angle measurement uses a self contained reference fluid.

53 Process Measurement An OSEE Surface Cleanliness Measurement System

54 Process Measurement The Photo Electric Effect:

55 Process Measurement Optically Stimulated Electron Emission (OSEE)

56 Process Measurement An OSEE Surface Cleanliness Measurement System Before Cleaning After Cleaning

57 1. Industry Trends and Motivation 2. Surface Conditioning and Adhesion 3. Plasma Composition and Generation 4. Surface Cleanliness and Activation 5. Process Measurement 6. PlamaPlus Coating 7. Important Results

58 PlasmaPlus Coating Process As substitution for primers on metals Long-term durable bonding Corrosion inhibiting Environmentally friendly because no solvents are used and no drying is required Recyclable because if their marginal layer thickness

59 PlasmaPlus Coating Process Adhesion promoting layers for hybrid materials (thermoplastic-metal or rubber-metal) Coating of steel, stainless steel, zincplated steel, titanium, aluminum and electro-deposition. Good success with PA6, PBT and TPU No primer necessary

60 PlasmaPlus Coating Process 1. Surface cleaning (organic materials) 2. Coating with silicon-organic compounds 3. Activation to improve bonding

61 PlasmaPlus Coating Process 1. Surface cleaning (organic materials) 2. Coating with silicon-organic compounds 3. Activation to improve bonding

62 PlasmaPlus Coating Process 1. Surface cleaning (organic materials) 2. Coating with silicon-organic compounds 3. Activation to improve bonding

63 Atomic Percent PlasmaPlus Coating Process Depth profile of a silicon-organic AES Depth Profile of 25x6 Film on 5754 Al adhesion promoter coating on aluminum (Auger Electron Spectroscopy) Depth (angstroms) Carbon C O Oxygen Aluminum Si Silicon Uniform, Approx.130nm thick Carbon-poor (<5 %) inorganic coating

64 PlasmaPlus Coating Process Important aspects of PlasmaPlus Coating Technology Properties: Silicon-organic and organic coatings with functional groups Hydrophilic or hydrophobic properties Layer-densities between 20 and 700 nm Deposition rates up to approx. 1µm/sec Substrates: metals, polymers, ceramics, glass PlasmaPlus -Coating of a windscreen for primer-free bonding (FORD Motor Company) Possibilities: Anticorrosion Adhesion promotion Release-coatings Non-Stick-coatings for tacky surfaces Optical coatings Protective coatings

65 1. Industry Trends and Motivation 2. Surface Conditioning and Adhesion 3. Plasma Composition and Generation 4. Surface Cleanliness and Activation 5. Process Measurement 6. PlamaPlus Coating 7. Important Results

66 Important Results Control Plasma-Treated MN/m2 psi MN/m2 Psi Polyimide (PMR -15) Polyphenylene sulphide (Ryton R-4) Polyether sulphone (Victrex 4100G) Polyethylene / PTFE (Tefzel ) ---- Very Low HDPE LDPE Polypropylene Polycarbonate (Lexan ) Nylon Polystyrene Mylar A PVDF (Tedlar ) PTFE Source: Liston et al., (1993) Plasma Surface Modification of Polymers for Improved Adhesion: a Critical Review, Journal of Adhesions Science & Technology.

67 Important Results Test Results of Adhesive Bonded Joints Substrate Combination Polyimide + Titanium Polyimide + Titanium Treatment Joint Type Bond Area (mm2) Failure Mode Joint Strength (Mpa) Std. Dev. (Mpa) Untreated Overlap Adhesive Atmospheric Plasma Overlap Cohesive Source: Akrama, et al., In New Materials and Processes for a New Economy: 55th International SAMPE Symposium, Seattle, USA, May SAMPE USA, 2011.

68 Important Results Aluminum EN6016, Thermal Cure Epoxy Adhesive Adhesive Failure (AF) AF AF CF CF Cohesive Failure (CF) AF error: ± 1 MPa

69 Pull Strength Important Results Not only an Increase in Bond performance But a Decrease in Variance Without Plasma Mean Std. Dev. With Plasma (Source: Kegel & Schmid 1999)

70 Important Results Peel test results from various pretreatments on aluminum. Urethane adhesive. Plasma treatment leads to cohesive failures. Plasma coated aluminum provides the bond line with greater protection through a 96 hour salt spray test

71 Key Take-Aways Materials joining in manufacturing of lightweight, often dissimilar substrates present technical challenges. Surface conditioning prior to bonding dissimilar materials enables better adhesion. Plasma cleans surfaces by removing surface contaminants and activates surface chemistries - eliminating primers. Plasma stabilizes manufacturing bonding processes. Plasma coatings modify surfaces to provide corrosion protection, and improves or inhibits adhesion.

72 Thank You! Time for Some Questions? Andy Stecher