Self-assembled VMs and the advantages of using them in Isabella Goldmints, Rajiv Taribagil, Stuart Briggs Infineum USA, LP
Outline Viscosity modifier chemistry, structure, and properties Unique properties of self assembled hydrogenated styrene diene (HSD) VMs Trends in motor oil Self-assembled HSD VMs for higher Group base stocks and low viscosity grades Shear stability of self-assembled HSD VMs Soot credits of self-assembled HSD VMS Conclusions
Role of Viscosity Modifiers (VMs) in an Engine Oil Main role of VMs is to increase Viscosity Index (VI) to make a multigrade oil Main properties are: Contribution to viscosity per unit mass measured by thickening efficiency (TE) Resistance to permanent shear, and consequent viscosity loss measured by Shear Stability Index (SSI) TE/SSI balance Other performance characteristics: Compatibility with a range of basestocks Oxidative stability Deposit control Soot control
VM Chemistry The chemistry of a VM impacts its TE, SSI, interaction with baseoiland other components Polymethacrylates (PMA) were among the first VMs Known for excellent low temperature pumpability Poor TE, high treat rate Possible deposit issues PMAs were displaced by olefin copolymers (OCP) Higher TE, low treat rate and low cost Lower VI than PMAs Ø SC-OCPs (high ethylene) have high TE but can form structures and gels at low temperature Ø A-OCPs (lower ethylene) are less likely to form crystalline structures, but have lower TE than SC-OCP Hydrogenated Styrene Diene (HSD) polymers Amorphous, good low T pumpability Good TE, low treat rate Ø Stars: covalently bound Ø Diblocks: assemble in micelles PMA Semi-Crystalline OCP Amorphous OCP HSD Star Di-block HSD
VM properties depending on self-assembly Tunability of TE in various base stocks: Size of the aggregate can be different depending on the baseoil quality Superior shear stability Due to partial demicellization under shear and micelle repair after shear Soot control Due to affinity of polystyrene block to soot surface and steric stabilization by h-diene block
Current Trends in Motor Oils Better Basestocks Lower Vis Grades Improved Shear Stability Soot Handling
Current Trends in Motor Oil Properties Better Basestocks Lower Vis Grades
Trends in Motor Oils Lower viscosity grades and better basestocks: Most VMs have lower solubility and lower thickening efficiency in higher quality basestocks 10-15% reduction in TE in Group III basestocks 25 SSI OCP 25 SSI HSD Star 10 SSI HSD Diblock TE in Gr I 1.7 2.6 2 TE in Gr III 1.5 2.3 1.7 Structure of the diblock can be tuned to form aggregates (micelles) with optimal thickening efficiency at desired SSI: Block sizes control aggregation number, hydrodynamic radius, and thus TE and viscometricproperties
Unique Feature of Diblock VMs: Self-Assembly Micellization Demicellization Diblock Polymer Micellar Assembly Diblock VMs have two distinct polymeric blocks with differing oil solubility Oil-phobic block Polystyrene Tunable phobicity allows for reversible association-dissociation Oil-philic block Hydrogenated polydiene responsible for thickening of oil Diblock molecules self-assemble in the oil: Aggregation depends on the absolute and relative sizes of both blocks, temperature and quality of baseoil Aggregation is dynamic, i.e. fully reversible
Tunability of Micellization Oil-phobicity of polystyrene block drives micellization Critical Micelle Temperature Increasing temperature beyond a critical value reduces oilphobicity Micelles dissociate reflected in viscosity drop Micelle Rheometric Profile of Diblock Concentrate Free chains
Tunability of Micellization Oil-phobicity of polystyrene block drives micellization Increasing temperature beyond a critical value reduces oilphobicity Critical Micelle Temperature Higher saturates Micelles dissociate reflected in viscosity drop Micelle Critical Micelle Temperature (CMT) is unique to basestock system Higher saturates, higher CMT Dictates viscometrics of diblock VM Rheometric Profile of Diblock Concentrate Free chains
Tunability of Micellization Oil-phobicity of polystyrene block drives micellization Increasing temperature beyond a critical value reduces oilphobicity Micelles dissociate reflected in viscosity drop Critical Micelle Temperature (CMT) is unique to basestock system Higher saturates, higher CMT Dictates viscometrics of diblock VM Changing polystyrene block size allows for tuning CMT to fit the basestock system Micelle Decreasing PS block size Rheometric Profile of Diblock Concentrate Critical Micelle Temperature Higher saturates Free chains
The Next Generation Diblock for Better Base Stocks Micellization Demicellization Diblock Polymer Micellar Assembly Next Generation Diblock contains: A polystyrene block designed for better quality basestocks A revised hydrogenated polydieneblock to provide optimized commercially attractive balance of thickening efficiency and shear stability Retains soot credits and shear stability
Next Generation Diblock in Finished Oils SAE 10W-40 SAE 10W-40 Top Tier Full SAPS HDD DI Current Diblock Next Gen. Diblock Diblock Polymer Treat, % 0.65 0.55 Grp III 4cSt/6cSt 1/4.0 1/14.6 Viscometrics KV100 (cst) 12.8 13.0 HTHS150 (cp) 3.8 3.8 CCS @ 25 C (cp) 6329 5864 Improved thickening gives lower polymer treat rate Increase in heavier basestock At matching KV and HTHSV, CCS is improved Next Generation Diblock in Group III offers increased use of heavier base stocks at a lower VM treat rate, and improved low temperature performance due to use of better diluent oil
Current Trends in Motor Oil Properties Improved Shear Stability
New engine designs: severe shear environment Advances in engine cam drive gear set design is creating a more severe shear environment Low Contact Ratio Spur Gears have been replaced with High Contact Ratio gear sets More, smaller teeth on same pitch diameter Reduced noise, vibration and harshness for the driver/operator More aggressive shear device
Shear Stability in Mack MP-8 Field Trial Mack MP-8 415 HP engines are representative of high shear, low soot environment The results are averages from at least four drains and two trucks Diblocks retain viscosity and show very good shear stability in the severe field service *the results are not corrected for fuel dilution or soot
Retained Kurt Orbahn Shear Stability of Next Generation Diblock The Next Generation Diblock shear stability matches Current Diblock in KO (ca. 1.0 cst @ 90cycles) Current Diblock Next Gen. Diblock Initial KV (cst) 15.5 15.5 KV after 30 cycle KO (cst) 15.0 15.1 KV after 90 cycle KO (cst) 14.4 14.5
Excellent Shear Stability in Mack MP-8 Field Test Shear stability of Next Generation Diblock vs. Current Diblock) in SAE 15W-40 oils in Mack MP-8 field test (2 trucks per oil) Similar shear stability in the high shear field service Wear metals at EOT are low for both oils Fe < 50ppm Cu < 25ppm Pb < 3ppm Current Diblock Oil Next Gen. Diblock Oil 15W-40 KV100 limit
Current Trends in Motor Oil Properties Soot Handling
Diblock Soot Handling Capability in Mack T11 Test Addition of Diblock VM improves soot induced viscosity increase in Mack T11 engine test SAE 5W-40
Next Generation Diblock Retains Soot Credit in Mack T11 Test at Lower Treat SAE 10W-40 Current Diblock Experimental Top Tier low SAPS HDD DI* Next Gen. Diblock Diblock Polymer Treat, % 0.72 0.62 Grp III 4cSt/6cSt 1/11.1 1/8.6 Viscometrics KV100 (cst) 13.0 13.0 HTHS @ 150 C (cp) 3.7 3.7 CCS @ 25 C (cp) 6616 6260 *slim DI for borderline performance % Soot @ 15.0 cst Increase limit <6.70% Next Generation Diblock compared to Current Diblock and Infineum Star VM At 14% lower VM treat rate the Next Gen. Diblock oil closely matches the reference
Soot Handling Capability in DV4 Test Addition of Diblock VM improves soot induced viscosity increase in DV4 engine test in the SAE 5W-40 passenger car diesel oil 25 % Viscosity increase 20 15 10 5 Repeat Repeat 0 Single VM- no HSD diblock Mixed VM with HSD diblock
Next Generation Diblock Retains Soot Credit in DV4 Test SAE 5W-40 Experimental Top Tier PCMO DI* Current Diblock Next Gen. Diblock Diblock Polymer Treat, % 0.42 0.42 Infineum Star VM Treat, % 1.13 1.13 Grp III 4cSt/6cSt 1.7/1 1.7/1 Viscometrics KV100 (cst) 14.51 14.59 HTHS @ 150 C (cp) 3.8 3.8 CCS @ 30 C (cp) 4977 4520 *slim DI for borderline performance Next Generation Diblock gives equal/better soot handling performance than Current Diblock at equal treat rate
Soot Handling Capability in DV6 Test Similar improvement in soot induced viscosity control is seen in DV6 test (SAE 5W-40 passenger car diesel oil) KV100 (cst) 50 40 30 20 10 HSD Star HSD Diblock 0 0 2 4 6 8 Soot (%)
Conclusions Self-assembled VMs offer unique features in lubricant formulations for Tunable aggregate structures for better viscometric properties Reversible partial disassembly for better shear stability Soot handling credits Next Generation Diblock is designed for the use in low viscosity grade oils containing higher group basestocks Compatibility with higher group basestocks allowing greater use of Group III Favorable viscometrics in Group III formulations allowing lower VM treat Retention of critical performance parameters: shear stability and boost in soot handling
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