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Using Rheology to Characterize Flow and Viscoelastic Properties of Hydrogels, Adhesives and Biopolymers

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Using Rheology to Characterize Flow and Viscoelastic Properties of Hydrogels, Adhesives and Biopolymers Tianhong Terri Chen PhD Senior Applications Scientist TA Instruments – Waters LLC TAINSTRUMENTS.COM Outline Basics in Rheology Theory TA Instruments Rheometers and DMAs Instrumentation Test methodologies Rheological Applications in Biopolymer and Biomedical Materials Hydrogels and creams Adhesives Drug capsules Polymers for medical devices TAINSTRUMENTS.COM Rheology: An Introduction TAINSTRUMENTS.COM Rheology: An Introduction Rheology: The study of the relationship between a stress and deformation Deformation Solid F = F(x); F ≠ F(v) Purely Elastic Most material Deformation + Flow Viscoelastic Flow Liquid F = F(v); F ≠ F(x) Purely Viscous Stress Stress = Modulus = Viscosity Strain Shear rate TAINSTRUMENTS.COM What does a Rheometer do? Rheometer – an instrument that measures both viscosity and viscoelasticity of fluids, semi-solids and solids It can provide information about the material’s: Viscosity - defined as a material’s resistance to flow deformation and is a function of shear rate or stress, with time and temperature dependence Viscoelasticity – is a property of a material that exhibits both viscous and elastic character. Measurements of G’, G”, tan δ with respect to time, temperature, frequency and stress/strain are important for characterization. TAINSTRUMENTS.COM Who Will Need Help with Rheology Analysis? Food Personal Care Pharmaceutical Polymers Adhesives & coating Automotive Aerospace Bio-medical devices Asphalt TAINSTRUMENTS.COM TA Instruments Rheometers and DMAs TA Rotational Rheometers ARES-G2 and ARES (Strain Control – SMT) DHR or AR (Stress Control – CMT) TA DMAs RSA-G2 and RSA (Strain Control – SMT) DMA Q800 (Stress Control – CMT) TAINSTRUMENTS.COM Rotational Rheometers at TA ARES G2 DHR Controlled Strain Controlled Stress Dual Head Single Head SMT CMT TAINSTRUMENTS.COM Geometry Options Concentric Cone and Parallel Torsion Cylinders Plate Plate Rectangular Very Low Very Low Very Low Solids to Medium to High Viscosity Viscosity Viscosity to Soft Solids Water to Steel TAINSTRUMENTS.COM DMAs from TA Instruments RSA G2 Q800 ARES G2 and DHR Controlled Strain Controlled Stress DMA mode SMT CMT (oscillation) TAINSTRUMENTS.COM DMA Clamps Submersible Submersible S/D Cantilever Tension-Film Shear-Sandwich Compression 3 Pt Bend Submersible 3-Point Bending Tension-Fiber Compression Tension TAINSTRUMENTS.COM ElectroForce Load Frames ElectroForce 3300 ElectroForce 3510 ElectroForce 3500 Floor Standing (7500 N) (15000 N) ElectroForce 3300 (3000 N) (3000 N) ElectroForce 3200 (450 N) ElectroForce 5500 ElectroForce 3100 (200 N) (22 N) Frequency Forces to Interchangeable to 300 Hz 15kN Fixtures TAINSTRUMENTS.COM Common Rheological Experimental Methods TAINSTRUMENTS.COM Flow Experiments What flow measures o Viscosity “lack of slipperiness,” resistance to flow The viscosity of water at room temperature is 1cP Type of flow measurements on rheometer o Viscosity vs. time Viscosity at single shear rate/stress Time dependence (Thixotropy or Rheopexy) o Viscosity vs. shear stress or rate Newtonian Shear thinning, shear thickening, Yield stress o Viscosity vs. temperature TAINSTRUMENTS.COM Flow Behaviors TAINSTRUMENTS.COM Information from a Flow Curve What shear rate? 4) Chewing, swallowing 5) Dip coating 1) Sedimentation 6) Mixing, stirring 2) Leveling, Sagging 7) Pipe flow 3) Draining under gravity η log 8) Spraying and brushing 9) Rubbing 10) Milling pigments 11) High Speed coating 4 5 6 8 9 1 2 3 7 10 11 1.00E-5 1.00E-4 1.00E-3 0.0100 0.100 1.00 10.00 100.00 1000.00 1.00E4 1.00E5 1.00E6 shear rate (1/s) TAINSTRUMENTS.COM Dynamic Oscillatory Tests Phase angle δ Strain, ε Stress, σ* Dynamic stress applied sinusoidally User-defined Stress or Strain amplitude and frequency TAINSTRUMENTS.COM Viscoelastic Parameters The Modulus: Measure of materials overall ̍∗ = ̴̙̲̥̳̳ ∗ resistance to deformation. ̴̡̙̲̩̮ The Elastic (Storage) Modulus: Measure of ɑ ·΢ΠΓΡΡ ∗ elasticity of material. The ability of the G = ·΢ΠΏΗΜ cos δ material to store energy. The Viscous (loss) Modulus: ∗ G" = ·΢ΠΓΡΡ sin δ The ability of the material to dissipate ·΢ΠΏΗΜ energy. Energy lost as heat. Tan delta (phase angle): ͻ" tan δ = ͻɑ Measure of material damping - such as vibration or sound damping. G* The triangle relationship G" Phase angle δ G' TAINSTRUMENTS.COM Understanding Oscillation Experiments What oscillation measures? oViscoelastic properties (G’/E’, G”/E”, tan δ) Approach to Oscillation Experimentation oStress and Strain Sweep • Measure linear viscoelastic region • Yield stress, stability oTime Sweep • Stability and structure recovery • Curing o Frequency Sweep • Measure polymer relaxation • Compare viscoelasticity of different formulations oTemperature Ramp • Measure glass transition, • Temperature operation range of a material TAINSTRUMENTS.COM Rheology Applications in Biopolymers & Biomedical Materials TAINSTRUMENTS.COM Purpose of a Rheological Measurement Three main reasons for rheological testing: • Characterization Structure-property relationship. MW, MWD, branching, state of flocculation, etc. • Process performance Formulation stability, processing temperatures, extrusion, blow molding, pumping, leveling, etc. • End product properties Mechanical strength, glass transition and sub-ambient transition temperatures, dimensional stability, settling stability, etc. TAINSTRUMENTS.COM Hydrogels and Creams • Hydrogels and creams are soft matters that contain high level of liquids such as water or oil • Hydrogels and creams are used in a wide variety of applications including tissue engineering, wound patch, drug delivery, contact lenses and superabsorbent materials • Rheology can provide key information on gel formation and gel strength on different formulations TAINSTRUMENTS.COM Natural Polymer: Hyaluronic Acid • Hyaluronic acid is a natural polysaccharide, which is commonly used in pharmaceutical, biomedical and personal care • Rheology can evaluate the visco-elastic properties as function of concentration, ionic strength, Mw, degree of crosslinking, formulations etc. TAINSTRUMENTS.COM Hyaluronic Acid Gels: • Hyaluronic acid gels are used as lubricating agent during abdominal surgeries to prevent adhesion and also for join lubrication, wound healing etc. • Rheology can monitor HA gelation and evaluate the gel strength TAINSTRUMENTS.COM Gels: Gelatin Gelation vs. Temperature Thermal reversible gelatin gels: o Measure gelation and gel melt TAINSTRUMENTS.COM Gelatin Gel Strength at Different Concentration • A dynamic frequency sweep test can be used to compare gel strength at applications temperature TAINSTRUMENTS.COM Gelatin/Chitosan Conjugation • Use enzymatic approach to covalently graft gelatin to chitosan • The conjugate exhibits interesting Tyrosine mechanical properties • Applications as biomedical adhesives Chen et al. Biopolymers, Vol. 64, 292-302 (2002) TAINSTRUMENTS.COM Vesicle-Biopolymer Gels • Attach n-dodecyl tails to Chitosan backbone to obtain an associating biopolymer (HM-Chitosan) • HM-Chitosan mixed with surfactant vesicle solution leads to a gel formation • This hydrogel showed strong elasticity HM-Chitosan behavior and has potential applications in biomedical control release Chen T; Raghavan SR et al, Langmuir, 21, 26-33 (2005) TAINSTRUMENTS.COM Contact Lens Visco-elasticity • Compare frequency dependency of contact lens elasticity 0.3500 " t͕͢ = ɒ 0.3000 Vendor A 0.2500 0.2000 Vendor B tan(delta) 0.1500 0.1000 0.05000 0 1.000 10.00 100.0 ang. frequency (rad/s) TAINSTRUMENTS.COM Creams/Lotions: Stability Testing Stability, phase separation of a cosmetic cream 1E+06 l G' emulsion Ap G'' emulsion A l G' emulsion Bp G'' emulsion B 1E+05 l l l l l l l l l l l l l 1E+04 l p p p lp p ' ' ' ' l' 'p 'p 'p 'p 'p 'p l l Moduli [Pa] G'' G' & l l l l 1E+03 0 1 2 3 4 5 6 7 8 910 strain [%] TAINSTRUMENTS.COM High Temperature Performance of Lotions A: Hydrating Lotion B: UV Protection C: Generic Brand o 10 3 G‘ for A decreases at 37 C G‘ for B withstands higher temperature =>used at 10 2 2 higher temperature hydrating beauty lotion δ same lotion with UV protection conditions (beach) generic hydrating lotion 1 10 G‘ for lotion C increases Loss tan before dropping; tan δ decreases => phase ModulusG' [Pa] 0 10 0 separation for lotion C Tan δ for A & B increases above 37 oC=> wax crystals 0 10 20 30 40 50 60 melt and lower the modulus Temperature T [°C] Ming L. Yao; Jayesh C. Patel Appl. Rheol. 11 ,2,83 (2001) TAINSTRUMENTS.COM Low Temperature Performance of Lotions 0.8 7 6 10 w/o emulsion 10 o/w emulsion: G' G' 10 6 G" 0.6 G" 5 tand δ 10 10 5 0.4 δ 10 4 tan 10 4 3 Modulus G' [Pa] 10 0.2 Modulus G', G" [Pa] Modulus G" G', Modulus G’, G” [Pa] G” G’, Modulus 2 10 3 10 -8 oC 0.0 -30 -20 -10 0 10 20 30 -100 -80 -60 -40 -20 0 20 40 60 80 100 Temperature T [ oC] Temperature T [ oC] In an o/w emulsion the freezing point of water is depressed due to the dispersed oil phase. Cooling below the freezing point has a major effect on temperature stability In an w/o emulsion, the dispersed water droplets freeze, but not the matrix. These emulsions do not have a sharp freezing point R.Brummer Rheology essentials of Cosmetics Springer ISBN: 3-540-25553-2 TAINSTRUMENTS.COM Emulsion Temperature Stability • Cycle temperature to evaluate temperature stability of emulsions V. André, N. Willenbacher, H. Debus, L. Börger, P. Fernandez, T. Frechen, J. Rieger. Prediction of Emulsion Stability: Facts and Myth . Cosmetics and Toiletries Manufacture
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