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To improve Barrier Protection in off-shore structures, petrochemicals, paper mills, under water structures, pen stocks, cross country pipelines…etc. The coating is a self priming layer and over coats are compatible. Protects M.S. and concrete in confined areas and satisfies Low VOC requirements.

Provides excellent adhesion, along with moisture tolerance and Elastomeric Properties, to the Epoxy Coating. Highly suited for underwater structures.

A long-life Primer on Steel under corrosive environments, especially in underwater structures. Primer for blast cleaned steel during storage, fabrication and construction.

Is recommended for the protection of MS/RCC substrate subjected to continuous water immersion, exposure to marine environment, high humidity or subsoil conditions.

A fast drying coating exhibiting excellent colour and gloss retention, resilience, scratch hardness, weathering and resistance to mild acids, alkalis and salt water.

Suited for weathering. Water resistant, flexo-hard features, bond strength, wear & impact resistance. The membrane will meet the requirements of Water tank linings, cross country pipe wrapping and impermeable lining for dyke walls and partitions.. The coating is designed to suit normal traffic.

e-mail: <seshadrisharan@gmail.com>

]]> http://fatiguetester.wordpress.com/2009/08/01/fatigue-tester-by-proto-tech/ Sat, 01 Aug 2009 19:59:43 +0000 JC40 http://fatiguetester.wordpress.com/2009/08/01/fatigue-tester-by-proto-tech/ The new Fatigue Tester by Proto-tech can cycle four specimens independently up to 400N max. Here is a recent installation at the Kois Center in Seattle.

Fatigue Tester

L.G. CUNHA, University of Taubaté – UNITAU, Taubaté, Brazil, R.C.B. ALONSO, University of Campinas – UNICAMP, Piracicaba, Brazil, L.R. SILVA-CONCILIO, Taubaté University – UNITAU, Taubaté, Brazil, A.C.C. NEVES, Universidade de Taubate, Taubaté, Brazil, J.L. FERRACANE, Oregon Health & Science University, Portland, OR, and M.A.C. SINHORETI, State University of Campinas, Piracicaba, Brazil
Objectives: This study evaluated the influence of curing methods on the relation between the development of stress rate and magnitude and volumetric shrinkage and bond strength of a composite restorative. Methods: For the stress test, composite (0.84 mm thick) was applied between two 5-mm diameter glass rods, mounted in a servohydraulic machine. Stress rate was taken as the value of stress/time each second. Volumetric shrinkage was measured in a mercury dilatometer each three seconds. Bond strength was measured by push-out test. C-factor was 3.0 and the composite was Filtek Z250 (3M-ESPE) in all tests. Seven curing methods were evaluated, four using halogen light (VIP, Bisco): Continuous light (CL), Soft-Start (SS), and two Pulse Delay methods, using different initial irradiances: 80 mW/cm2 (PD80) and 150 mW/cm2 (PD150), and three using LED light (Freelight II – 3M-ESPE): High (HLED), Medium (MLED), and Low (LLED) Intensity. The results were analyzed by ANOVA/Tukey’s test (p=0.05). Results: Stress values ranged from 7.9 MPa (PD80) to 10.5 MPa (HLED). PD80 showed a statistically inferior stress compared to the others, except PD150. HLED presented the highest stress rate, followed by LC, MLED, SS, PD150 and PD80. Volumetric shrinkage ranged from 2.15% (PD80) to 2.27% (MLED), with no statistical differences among curing methods. Shrinkage rate results followed the same order as stress rate for the curing methods. Bond strength values varied from 24.6 MPa (HLED) to 35.5 MPa (PD150), and PD150 and PD80 were higher than the others. Conclusions: Modulated curing methods were shown to be effective in reducing stress rate and shrinkage rate, while improving the strength of the bonded interface, and without affecting the volumetric shrinkage of the restorative composite. Supported by CAPES (Brazil – PDEE grants BEX3428/04-4).

This is a nice study that found that reduced stress rate, effected by different curing schemes, was matched by higher bond strength in a push-out type specimen. The specimen geometry is important here because it is the confinement of the composite in a cylindrical hole that causes the stress rate to create damage at the interface. There’s a leap of faith in comparing results from the servohydralic stress tester to the mercury dilatometer to the push-out test. But assuming the conditions are similar, i.e. comparable illumination, this is an interesting result. How can there be a 25% range in stress values, a 33% range in bond strengths, and hardly any difference in shrinkage values? Doesn’t shrinkage cause stress? Or rather, doesn’t stress accumulate in a confined composite volume at about the same rate as shrinkage in a free composite? The answer has something to do with how the formation of the network proceeds in the presence of a stress field. I look forward to the article when it appears in print.