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CHAPTER 7 POLYESTER RESIN
1) Polyester Resin2) Components3) Characteristics of Polyester Resin4) Methods of
Polyester resin material is a three-component material. However, the manufacturer mixes the two reactive parts. At the time of application, a catalyst is added to start the reaction. Then the material is sprayed onto the roadway. Refl ective beads are added using a separate gun located directly behind the paint gun.
The material is composed of pigments that are very similar to those used in other pavement markings. The pigments are used to impart color, hiding and other desirable properties, like all other markings. However, these pigments are pre-ground prior to being blended into the resin.
The marking has polyester resin that is mixed with a reactive solvent, a styrene compound. Normally, solvents are expected to evaporate and not participate in the setting up process. In addition to acting as a solvent, the styrene participates in the polymerization process. In order for this material to begin to react, a catalyst must be added to initiate the reaction.
Driers are added to assist in the curing process.
Refl ective Beads
Beads are uniformly applied across the entire width of the marking by either a gravity or pressurized bead applicator located immediately behind the polyester spray gun. Beads are generally applied at a rate of 8 lb/gal.
CHARACTERISTICS OF POLYESTER RESIN
The material has the potential to be 100 percent solid. This depends on how fast the reaction takes place. The styrene is volatile prior to the reaction. Heat is not typically added to the system except when cure time is expected to be long, such as on cool spring or fall days. The catalyst is added to drive the reaction. Usually, the catalyst is methyl ethyl ketone (MEK) or benzoyl peroxide. The polyester resin and the styrene solvent react together to crosslink, or polymerize, to form a fi lm. The polyester resin system will not cure properly if the appropriate quantity of catalyst is not added.
• Essentially two components in one container
• Peroxide catalyst is a very reactive oxidizer
• Requires placarding as a hazardous material
• Flush solvent is fl ammable and a hazardous waste
• Moisture in surface a major factor and detriment
• Set up time depends on type of resin (usually 3-20 minutes)
• Diffi cult to determine whether mixed properly
METHODS OF APPLICATION
The catalyst can be added by either external or internal mixing. External mixing requires the use of two guns; one sprays the catalyst into and on the freshly applied liquid immediately prior to refl ective bead application. This is the preferred method when an airless gun is used. With a conventional system, it is possible to have a set up where the catalyst is injected into a mixing chamber within the gun, by which the catalyst is added to the material stream. Atomizing the air mixes the material just prior to it being sprayed onto the roadway.
The lower the air and road surface temperature, the longer it will take for the material to react and set up. There are two types of material: a slow dry that takes about 10 minutes at 70°F and a fast dry that takes about 3 minutes at 70°F. The minimum road and air temperature to apply polyester pavement marking is 50°F and rising.
The material is not dependent upon heat to make it set up. However, the application of minimal heat (130°F) is helpful in the spring and fall.
Pavement Surface Considerations
Polyester cannot be applied to new HMA until the road surface oils have been removed. Concrete must have curing compounds, latency, dust, dirt, and other debris removed prior to application.
Figure 7.1 is a polyester application troubleshooting table using the conventional application method. Figure 7.2 is a polyester application troubleshooting table using the airless application method.
Polyester Application Troubleshooting
- Use or adjust shrouds if edges are “fuzzy or light.
- Apply small amount of heat during application (no more than 120 °F)
Figure 7.1 Polyester application troubleshooting
Polyester Application Troubleshooting –continued
Polyester Application Troubleshooting
Polyester application troubleshooting for airless application
VIRGINIA DOT REFERENCES
VIRGINIA DOT ROAD & BRIDGE SPECIFICATION BOOK
Section 246.01 thru 246.02 (a) (a) Color Requirements
Section 246.02 (d) 1. and 2.
(d) Polyester Resin (Type B, Class II) 1. Composition 2. Physical Requirements
Section 704.01 thru 704.03 (a) 2. b.
704.01 thru 704.03 Description, Material Types, and Procedures (a) Pavement Markings 2. Type B Markings b. Polyester Resin (Class II) Application and Bead Application
VIRGINIA MANUAL OF INSTRUCTIONS
Section 204.30 (a) (1) and (2)(1) Sampling, Testing, and Approval(2) Acceptance (Requires Cert. I)
VIRGINIA TEST METHOD
VTM-94 Quality Control Testing of Pavement Markings
What is one advantage for using polyester pavement marking materials ?
a) The peroxide catalyst is a very reactive oxide.
b) It is a relatively inexpensive material.
c) Asphalt paving oils used are a detriment.
d) This material’s use requires placarding.
specifi ed thickness for polyester pavement markings is
a) 20 ± 2 mils when wetb) 12 ± 1 mils when wetc) 15 ± 1 mils when wetd) 90 ± 5 mils when wet
Polyester resin will not cure properly if the appropriate amount of catalyst is not added .
Polyester pavement marking material may be applied over any existing type of marking.
5. The minimum road and air temperature required to apply polyester pavement marking is:
Polyester resin is dependent upon heat to make it set up.
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