Grantee Research Project Results
Final Report: Solventless Adhesive Systems
EPA Contract Number: 68D99051Title: Solventless Adhesive Systems
Investigators: Gumbs, Ronald W.
Small Business: Gumbs Associates Inc.
EPA Contact:
Phase: I
Project Period: September 1, 1999 through March 1, 2000
Project Amount: $70,000
RFA: Small Business Innovation Research (SBIR) - Phase I (1999) RFA Text | Recipients Lists
Research Category: SBIR - Pollution Prevention , Pollution Prevention/Sustainable Development , Small Business Innovation Research (SBIR)
Description:
This report describes a research and development program to develop adhesives, sealants and caulking compounds that do not contain VOCs of HAPs. The experimental adhesives are based on nonvolatile acrylic monomers, which polymerize after application to provide the required adhesion for building construction and automotive body assembly operations. The monomers are blended with proprietary oligomers, which were developed during the program, and mixed with initiators to constitute a two-part adhesive system. Toward the end of the project, Foresight Science & Technology, Inc. under contract with the EPA on behalf of Gumbs has concluded the following:1. The auto industry has essentially replaced solvent-based adhesives with hot melts and water based adhesives as a result of pressure from the EPA, OSHA and labor unions.
2. While there is still a problem with the emissions of VOCs from the auto industry, the main sources stem from cleaning, casting and spraying operations.
3. Adhesives that still pose a problem in the auto industry include plastisol used for door sealants, some solvent-containing pressure sensitive adhesive tapes used in the assembly process, adhesives used in brake linings and adhesives used in priming metal for painting.
4. During automotive body assembly, the most significant chemical releases occur during painting and finishing.
In the light of the preceding, Foresight has recommended the development of performance-based adhesives for the secondary wood, laminating and furniture industries where there is a major problem with the use of replacements for solvent-based adhesives. This problem represents an attractive area of opportunity for the rapid-curing adhesives of the present project because the trend in these industries is toward increasingly higher production speeds.
The overall objective of Phase I was to demonstrate the feasibility of replacing VOCs and HAPs in solvent-based adhesives used in building construction and automotive assembly operations. The specific technical objectives of Phase I were:
1. Screen acrylic monomers for miscibility and compatibility with polymers used in adhesives.
2. Formulate the compatible monomer/polymer mixtures in two-part adhesives.
3. Evaluate the acrylic adhesives on various substrates.
4. Optimize the adhesives to meet specifications for selected applications.
The work during Phase I was organized along three main tasks: preliminary screening of monomers and polymers, formulation and evaluation. This was to culminate in the optimization of the most promising adhesives formulated to meet specifications for selected applications in the construction and automotive industries. Because of the much larger size of the market for adhesives used in building construction, the emphasis during Phase I was placed on developing adhesive systems in this area.
Three different types of curing were investigated: radiation, epoxy/amine and redox. In a critical study conducted late in the program, the exotherm profiles of 100 g. batches were measured in order to determine pot life and rate of redox curing at room temperature.
Evaluation of the formulated adhesives entailed determining the adhesive strength on aluminum, polypropylene, Lexan polycarbonate, plasticized polyvinyl chloride, steel, plywood, particle board, glass, gypsum wallboard, Saran, Mylar and polyethylene. UV-cured pressure sensitive adhesives (PSAs) exhibited strong adhesion to glass slides, paper, aluminum foil, plastic and wood. Measurements of tensile adhesive and shear strength of redox-cured adhesives on wood were not possible because failure of the bonds under stress occurred in wood rather than in the adhesive or at the interface.
Summary/Accomplishments (Outputs/Outcomes):
Pressure sensitive adhesives, epoxy/amine oligomer adhesives, rapid-curing adhesives and contact cements with good adhesion were developed in Phase I.The PSAs of the present work rely on a photocure with the focus on reduction of cost and odor. With judicious selection of comonomers in the synthesis of the oligomer, these adhesives are cost competitive with current UV-curable PSAs.
Containing about 50% Epon 828, the epoxy/amine/oligomer adhesives behaved essentially similar to conventional epoxy adhesives. The advantage of using the oligomer is lower viscosity and cost, combined with tailorable adhesive properties for the specific application.
Because the rate of redox curing is dependent on both the concentrations of reducing and oxidizing agent, the experimental adhesives can be completely cured in less than one minute at room temperature, if necessary.
With respect to solventless contact cements for bonding plastics to wood surfaces, what is envisoned is the simple application of one part of the redox curable adhesive to one surface, e.g. wood or particleboard, and the other part to the second surface, e.g. the high-density paper-and-plastic or polyester overlay. Because both parts contain monomer and oligomer, bonding and curing take place upon contact, eliminating the difficulties encountered with current replacements for contact cements.
Conclusions:
The major accomplishments of the Phase I work may be summarized as follows:1. It is 100% feasible to prepare solventless adhesives based on oligomers dissolved in nonvolatile monomers that can compete with solvent-based adhesives or their replacements used in building construction and automotive assembly operations.
2. The chemical nature of the oligomers as synthesized ensures low viscosity and tailorable adhesive properties.
3. Adhesion to plastic, metal, wood and glass is good.
4. Pressure sensitive, epoxy/amine/oligomer, rapid-curing adhesives and contact cements are feasible using the systems developed during Phase I.
5. A redox system that permits variable curing rates at room temperature is feasible.
6. The automobile industry has virtually replaced all solvent-based adhesives used in assembly operations.
7. The probability of penetrating markets in the secondary wood, laminating and furniture industries is quite high because of difficulties encountered with current replacements for solvent-based adhesives.
Supplemental Keywords:
solventless, adhesives, redox-curable, pressure-sensitive construction, wood, laminating, furniture., Economic, Social, & Behavioral Science Research Program, Scientific Discipline, Air, Toxics, Sustainable Industry/Business, air toxics, cleaner production/pollution prevention, Chemistry, HAPS, VOCs, Technology for Sustainable Environment, New/Innovative technologies, Engineering, Engineering, Chemistry, & Physics, Market mechanisms, Economics & Decision Making, polymeric coating, hazardous air pollutants, hazardous emissions, alternative materials, polymers, polymer conformation, solvent substitute, hazardous air pollutants (HAPs), coating formulations, Volatile Organic Compounds (VOCs), cost effective, pollution prevention, adhesives, coatings, polymer design, solvents, cost effectivenessThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.