Nine formulations of thermoplastic materials for traffic marking were prepared using a resin based on maleic anhydride modified with rosin in different proportions (18, 22 and 26%). As plasticizer a liquid coconut long oil alkyd resin (100% solids) was employed Hiding pigment was titanium dioxide; calcium carbonate and micronized tale were used as extenders. Coarse marble powder is used to facilítate the incorporation of glass beads. The operation was made employing a double Z mixer oil heated to obtain a mass temperature of 180-190 QC. The mixer was provided with two asynchronous arms rotating at 46 rpm.
Dry and wet abrasión tests were carried out and the obtained results indicated that wearing valúes are three times greater in the case of the wet test.
It is demonstrated that plasticization degree controls hardness variation as a function of temperature, determining a critical point which is the beginning of an abrupt reduction of hardness. Water absoption increases when plasticizer content increases. Matrix correlation of tests results was used to analize the obtained numeric valúes

Aznar, Alberto C.

Caprari, Juan J.

Meda, Jorge F.

Slutzky, O.

Centro de Servicios en Gestión de Información

STUDY OF FORMULATION VARIABLES OF THERMOPLASTIC REFLECTING MATERIALS FOR TRAFFIC MARKINGESTUDIO DE VARIABLES DE LA FORMULACION DE MATERIALES TERMOPLASTICOS PARA USO VIALA.C  Aznar, J J. Caprari1, J.F. Meda and O. Slutzky1 Miembro de la Carrera del Investigador del CONICETSUMMARYNine formulations of thermoplastic materials for traffic marking were prepared using a resin based on maleic anhydride modified with rosin in different proportions (18, 22 and 26%). As plasticizer a liquid coconut long oil alkyd resin (100% solids) was employedHiding pigment was titanium dioxide; calcium carbonate and micronized tale were used as extenders. Coarse marble powder is used to facilítate the incorporation of glass beads. The operation was made employing a double Z mixer oil heated to obtain a mass temperature of 180-190 QC. The mixer was provided with two asynchronous arms rotating at 46 rpm.Dry and wet abrasión tests were carried out and the obtained results indicated that wearing valúes are three times greater in the case of the wet test.It is demonstrated that plasticization degree controls hardness variation as a function of temperature, determining a critical point which is the beginning of an abrupt reduction of hardness. Water absoption increases when plasticizer content increases. Matrix correlation of tests results was used to analize the obtained numeric valúes.Keywords: thermoplastic materials, reflecting properties, agglutinant, dry abrasión test, wet abrasión test, bond strength, water elimination rate.INTRODUCTIONFrequently reflecting thermoplastics applied in cily streets, roads or highways lost their efficiency due to the wearing or to the partial detachment of the used materials. The appareance and physical characteristics were modified.The adequate life-time is a funtion of different variables [1], acting individually or as a whole: adhesión to the surface where they were applied on (asphalt or concrete), resistance to abrasión  and weathering (moisture due to rain, dew remaining long time in contact with 17thermoplastic marks), high temperatures producing deformation or low temperatures disminishing elasticity and favouring checking or cracking of the coat.An important aspect is related to the influence of traffic intensity and the rolling action of tires, specially the pressure when the tire takes contact with the line or the suction when rolling over them. A high quality result is related to the components of the formulation and to the adequate cleaning of the surface before application. A best performance was always obtained in asphalt pavements [2].The objective of this research is to determine the influence of composition variables (pigment/binder ratio, resin content, plasticizer type and content, filiéis employed, and PVC) on the adhesión or wearing resistance of the thermoplastic applied on a concrete surface.EXPERIMENTALNine samples of thermoplastics reflecting materials were formulated, containing as agglutinant a resin based on maleic anhidride and modified with rosin (A.I.= 14; melting point 114  QC). The modified resin was used in 18, 22 or 26% on the total formulation. As plasticizer a coconut oil alkyd resin was employed (without organic solvents) in a proportion between 2.7 and  6.5 per cent.As hiding pigment titanium dioxide rutile type was employed, to obtain a white colour with high luminosity (Y>80). Pigment formulation was completed using filiéis as calcium carbonate and tale, which are of good wearing resistence. Samples formulation were indicated in Table 1.Composition of the thermoplastic materials*TABLE1Material IA IB IC HA HB nc IDA 11TR meMaleic  resin 18.0 22.0 26.0 18.0 22.0 26.0 16.0 22.0 26.0Alkyd  resin 2.7 3.3 3.9 3.6 4.4 5.2 4.5 5.5 6.5Titanium dioxide 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0Glass beads 20.0 20.0 20.0 20.0 20.0 20.0 20.0 20.0 20.0Marble 22.4 20.3 18.2 22.0 19.8 17.6 21.6 19.3 17.0Calcium carbonate 22.4 20.3 18.2 22.0 19.8 17.6 21.6 19.3 17.0Tale 4.5 4.1 3.6 4.4 4.0 3.6 4.3 3.9 3.5* g.ioo gA double Z mixer (Fig. 1) was used for the thermoplastic preparation, having the mixer two asyncrhonic arms, one of them rotating at 46 rpm. For heating a mineral thermic fluid which circulates in the heating jacket was employed (máximum temperature 300 QC).Titanium dioxide, fillers and glass beads were incorporated at 180-190 2C. The operation at this temperature lasts 30 minutes. After that, the product obtained was casted in special molds.18Fig. 1.- Double Z inixer for test saín pies preparation Fig. 2.- Adhesión-strength determination by CIDEPINT methodFig. 3.- Wet and dry abrasión test equipment.19The samples tests were performed at different temperatures; wet and dry abrasión, Shore A hardness, adhesion-cohesion, water absorption and water elimination rate were determined.For the wet and dry abrasión test [3],circular specimens were employed (80 mm diameter and 3 mm thick). After 24 hours samples were abraded using a Taber Abraser equipment, with a H-22 abrasive and 1000 g load (ASTM D 4060). The dust produced by the wearing operation was eliminated constantly by flowing pressurized air. When a track is formed as a consequence of wearing, the sample is weighed with an exactitude of 1 mg. After that, the wearing operation is continued along 100 revolutions of the equipment and newly weighed. The difference between the two valúes obtained is expressed as dry wearing (Fig. 2).After finishing the previous test, distilled water is added to the track and the operation continued during 100 revolutions more. The sample is now conditioned for water elimination and weighed. The difference with the previous valué is expressed as wet wearing.Shore A hardness [4] at temperatures between 40 and 70 2C was determined each 5 CC, according to DIN 53505. In this case test plates are 50 mm diameter and 3 mm thick; the valué was registered after 15 seconds. Samples were stabilized during 1 hour at test temperature before hardness determination.To obtain adhesión and cohesión strength valúes a method developed at CIDEPINT was employed [5,6]. The melted material was put in the midst of concrete probes (3 mm trick), previously  primed with an acrylic vamish and preheated at 40 2C. An iron flexible wire was inserted in test probes to allow the clamps of a dinamometer. The traction effort was performed at a velocity of 200 mm.min1 and at a temperature of 20 2C (Fig. 3).For the determination of water absorption and water elimination rates [7,8,9], specimens of 50 mm diameter and 3 mm thick were prepared and weighed with the precisión of 1 mg. Hung by means of a copper wire, they were completely submerged in distilled water at 20 + 1 2C for 24 hours. After that, they were dried with filter paper and weighed; the operation was made after 48 and 72 h. Absoption valúes were obtained by difference with the initial weight of the samples .Afterwards the probes were conditioned at 20 2C and 50 % HR. By weighing, water elimination valúes were obtained.DISCUSSIONThe maleic resin is the agglutinant used in the formulation of thermoplastic traffic materials. The modification of physical properties (reduction of melting point and adequate elasticity characteristics) by means of an alkyd resin improved the system wetting, facilitating the incorporation of the hiding pigment (TiO2), fillers and glass beads. In those conditions a homogeneous distribution of glass beads was obtained. This is a very important aspect in field behaviour; in wearing, an adequate distribution of beads in the mass assures adequate night visibility, during a long period.A certain correlation was observed between the thermoplastic traffic materials composition and the valúes of the obtained physical properties (Table 2).21Correlation between materials composition variables and physical propertiesTABLE 2R P M C T w+ AS D A PVC WR 1.00 0.58 -0.97 -0.93 -0.98 -0.92 0.98 -0.31 -0.89 -0.97 -0.90P 0.58 1.00 -0.75 -0.77 -0.72 -0.71 0.43 -0.94 -0.73 -0.76 -0.75M -0.97 -0.75 1.00 0.97 0.99 0.95 -0.91 0.51 0.93 1.00 0.94C -0.93 -0.77 0.97 1.00 0.97 0.98 -0.85 0.55 0.93 0.97 0.98T -0.98 -0.72 0.99 0.97 1.00 0.95 -0.91 0.48 0.91 1.00 0.94w+ -0.92 -0.71 0.95 0.98 0.95 1.00 -0.87 0.50 0.84 0.95 1.00AS 0.98 0.43 -0.91 -0.85 -0.91 -0.87 1.00 -0.15 -0.83 -0.91 -0.84D -0.31 -0.94 0.51 0.55 0.48 0.50 -0.15 1.00 0.46 0.52 0.55A -0.89 -0.73 0.93 0.93 0.91 0.84 -0.83 0.46 1.00 0.92 0.84PVC -0.97 -0.76 1.00 0.97 1.00 0.95 -0.91 0.52 0.92 1.00 0.95w -0.90 -0.75 0.94 0.98 0.94 1.00 -0.84 0.55 0.84 0.95 1.00concentration of the different samples. Two series of wearing valúes were obtained (Fig. 4).Key of the tableR: resin P: PlastidzerM: marble powder C: calcium carbonateT: micronized tale W+: water absorptionAS: adhesión-strength D: hardness at 55°CA: abrasión PVC: PVCW: water eliminationIn the dry abrasión test the trend of wearing is determined by pigment volumePVCDry abrasión Wat abrasiónFig. 4.- Comparative result of dry and wet abrasión test.22The wet abrasión test shows greater wearing valúes than those obtained in the dry abrasión test.Results of hardness test, as a ñrntion of temperature, are related to the plasticization degree of the agglutinant resin. This is particularly observed over a temperature of 55 CC, which is considered critical; over this temperature valué, hardness disminishes abruptly in practically all the samples. This characteristics is independent of plasticizer level and PVC valúes (Fig. 5).Fig. 5.- Variations of hardness as a function of the temperature.The indicated critical temperature is a harmful interactive factor in the material application.Adhesion-tension valúes are lineally dependent on the employed resin (Fig. 6) and not related with the plasticizer level; the obtained valúes expressed in kg.cm"2 are of the same order than those of the standards used to qualify this type of materials.In the results of water absorption (Fig. 7) and water elimination (Fig. 8) tests, the increase  of weight of the termoplastic mass during inmersión is faster than the elimination valué.2316Resin content (%)Fig. 6.- Variations in adhesion-strength as a function of resin contenLCONCLUSIONS1. - The wet abrasión wearing valúes are higher than those obtained in the dry abrasión test. Wearing  is directly dependent on the plasticizer level but independent of the maleic resin content.2. - Plasticization degree has a high influence on hardness variation as a function of temperature. A critical point appears at 55 QC with a sudden reduction of hardness valúes.3. - Adhesión strength is dependent on the resin content, a higher content increases adhesión strength. This parameter is independent of the plasticization degree.4. - Water absorption decreases when plasticizer increases, independently of the resin content. Water elimination rate decreases too.5. - The retained moisture of the thermoplastic traffic material after inmersión must be considered as a harmful property in relation to the wearing resistence in service.24Water (mg) Water (mg)Fig. 7.- Water absorption valúes as a function of time.Fig. 8.- Water elimination valúes as a function of time.25REFERENCES[1] Lindberg, B., “Painting Concrete", J. Oil. Col. Chem. Assoc., 57, 100-113 (1974).[2] Nutt, N.O., “A Quantitative Method for Determining the Adhesión of Coatings to Plastics“, J. Oil Col. Chem. Assoc., 75, 53-58 (1992).[3] Departamento de Entradas Rodagen de Estado de Sao Pablo. Especificacoes e métodos de ensaios de materiais de sinalizacao redoviaria, 1990.[4] ASTM D-2240. Rubber property - Durometer Hardness, test 35, 702-705 (1980).[5] ASTM D-4796. Standard test method for bond strength of thermoplastic traffic marking materials, Vol. 06.01, 846-849 (1980).[6] Aznar, A.C., “Proposal for a method to determine the cohesive and adhesive bond strength of traffic marking thermoplastic materials”, CIDEPINT-Anales, 215-226 (1994).[7] Norma IRAM 1211. Recubrimientos termoplásticos para la demarcación de pavimentos (1981).[8] Norma IRAM 1212. Recubrimientos termoplásticos reflectantes para la demarcación de pavimentos (1981).[9] Koleske, J.V. (De.), “Paint and Coating Testing Manual”, Chapter 66, Fourteenth Edition of the Gardner-Sward Handbook, ASTM Manual Series MNL17 (1995).26

Study of formulation variables of thermoplastic reflecting materials for traffic marking

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Study of formulation variables of thermoplastic reflecting materials for traffic marking

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