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Thermal properties

Thermal properties. THERMAL PROPERTIES. Plays a vital role in evaluating the product performance & processibilty characteristics in polymers.

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Thermal properties

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  1. Thermal properties

  2. THERMAL PROPERTIES • Plays a vital role in evaluating the product performance & processibilty characteristics in polymers. • Thermal analytical methods monitor differences in some sample property as the temperature increases, or differences in temperature between a sample and a standard as a function of added heat. These methods are usually applied to solids to characterize the materials. Corporate Training & Planning

  3. THERMAL PROPERTIES • Heat Deflection Temperature (HDT) • Vicat Softening Temperature (VSP) • Thermal Endurance • Thermal Conductivity • Thermal Expansion • Low Temperature Brittleness • Flammability • Melting Point, Tm, and Glass Transition, Tg (DSC) • Thermomechanical Analysis Corporate Training & Planning

  4. HEAT DEFLECTION TEMPERATURE Defined as the temperature at which a standard test bar (5 x ½ x ¼ in ) deflects 0.010 inch under a stated load of either 66 or 264 psi. • Significance: • HDT values are used to compare the elevated temperature performance of the materials under load at the stated conditions. • Used for screening and ranking materials for short-term heat resistance. • HDT values do not represent the upper temperature limit for a specific material or application. • The data are not intended for use in design or predicting endurance at elevated temperatures. Corporate Training & Planning

  5. HEAT DEFLECTION TEMPERATURE • Test Method: • ASTMD 648, ISO 75 -1 and 75-2 • Test Specimen: • 127mm (5 in.) in length, 13mm (½ in.) in depth by any width from 3mm (⅛ in.) to 13mm ((½ in.) • Conditioning: • 23 ± 2oC and 50 ± 5% RH for not less than 40 hrs prior to test. • Two replicate specimens are used for each test Corporate Training & Planning

  6. HEAT DEFLECTION TEMPERATURE • APPARATUS • Specimen Supports: • Metal supports for the specimen of 100 ± 2mm • Immersion Bath • Deflection Measurement Device • Weights: 0.455 MPa (66 psi) ± 2.5% or 1.82 MPa (264 psi) ± 2.5%. • Temperature Measurement System Apparatus for Determination of HDT Corporate Training & Planning

  7. HEAT DEFLECTION TEMPERATURE • PROCEDURE • Measure the width and depth of each specimen • Position the test specimens edgewise in the apparatus • Position the thermometer bulb sensitive part of the temperature • Stir the liquid-heat transfer medium thoroughly • Apply the loaded rod to the specimen and lower the assembly into the bath. • Adjust the load to obtain desired stress of 0.455 MPa (66 psi) or 1.82 MPa (264 psi) • Five minutes after applying the load, adjust the deflection measurement device to zero or record its starting position • Heat the liquid heat-transfer medium at a rate of 2.0 ± 0.2oC/min. • Record the temperature of the liquid heat-transfer medium at which the specimen has deflected the specified amount at the specified fibre stress. Corporate Training & Planning

  8. HEAT DEFLECTION TEMPERATURE CALCULATION The weight of the rod used to transfer the force on the test specimen is included as part of the total load. The load (P) is calculated as: P = 2Sbd2 / 3L Where, S = Max. Fibre stress in the specimen of 66 Psi / 264 Psi b = Width of specimen d = Depth of specimen L = Width of span between support (4 in) Corporate Training & Planning

  9. HEAT DEFLECTION TEMPERATURE • RESULTS & CONCLUSION • A bar of rectangular cross section is tested in the edgewise position as a simple beam. • Load applied at the center to give maximum fibre stresses of 66 /264 psi. • The specimen is immersed under load in a heat-transfer medium provided with a means of raising the temperature at 2 ± 0.2oC/min. • The temperature of the medium is measured when the test bar has deflected 0.25mm (0.010 in). • This temperature is recorded as the deflection temperature under flexural load of the test specimen. Corporate Training & Planning 9

  10. HEAT DEFLECTION TEMPERATURE • FACTORS INFLUENCING • HDT of unannealed (heat treatment) specimen is usually lower than that of annealed specimen. • Specimen thickness is directly proportional to HDT because of the inherently low thermal conductivity of plastic materials. • Higher the fibre stress or loading lower the HDT. • Injection moulded specimen tend to have a lower HDT than compression – moulded specimen. • Compression moulded specimen are relatively stress free. Corporate Training & Planning

  11. TYPICAL FIBRE STRAIN VS. TEMPERATURE DIAGRAM OF A PLASTIC SAMPLE Corporate Training & Planning

  12. VICAT SOFTENING POINT (VSP) Defined as the temperature at which a flat ended probe with 1 mm2 cross section penetrates a plastic specimen to 0.04 inch (1 mm) depth. • SIGNIFICANCE • Data obtained by this test method may be used to compare the heat-softening qualities of thermoplastic materials. • This test method is useful in the areas of quality control, development and characterization of plastic materials. Corporate Training & Planning

  13. VICAT SOFTENING POINT (VSP) • Test Method: • ASTMD 1525 or ISO 306 • Test Specimens : • The specimen shall be flat, between 3 and 6.5mm thick and at least 10 by 10mm in area or 10mm in diameter. • Conditioning: • 23 ± 20C and at 50 ± 5 % relative humidity of not less than 40 hrs A minimum of two specimens shall be used to test each sample. Corporate Training & Planning

  14. VICAT SOFTENING POINT (VSP) • APPARATUS • Immersion Bath • Heat-Transfer Medium • Specimen Support • Penetration-Measuring Device Masses: 10 ± 0.2N or 50 ±1.0N • Temperature-Measuring Device • Needle Fig. 2 Apparatus for Softening Temperature Determination Corporate Training & Planning 14

  15. VICAT SOFTENING POINT (VSP) PROCEDURE • Prepare the immersion bath so that the temperature of the heat-transfer medium is between 20 and 23oC at the start of the test • Place the specimen, which is at room temperature, on the specimen support. • The needle should not be nearer than 3mm to the edge of the specimen. • Gently lower the needle rod, without the extra mass, so that the needle rests on the surface of the specimen and holds it in position. • Position the temperature-measuring device so that the sensing end is located within 10mm from where the load is applied to the surface of the specimen. Corporate Training & Planning

  16. VICAT SOFTENING POINT (VSP) PROCEDURE • Lower the assembly into the bath and apply the extra mass required to increase the load on the specimen to 10 ± 0.2N (Loading 1) or 50 ± 1.0N (Loading 2). • After a 5-min waiting period, set the penetration indicator to zero. • Start the temperature rise. • Record the temperature of the bath when the needle has penetrated 1 ± 0.01mm into the test specimen. RESULTS & CONCLUSION • Vicat softening temperature is expressed as the arithmetic mean of the temperature of penetration of all specimens tested. • If the range of penetration temperatures for the individual test specimens exceeds 2oC, record the individual results and repeat the test, using at least two new specimens. Corporate Training & Planning

  17. VICAT SOFTENING POINT (VSP) CASE STUDY Typical example of depth of penetration with temperature Corporate Training & Planning

  18. TORSION PENDULUM TEST (THERMAL ENDURANCE) • The torsion pendulum test determines shear modulus and mechanical power factor over a wide range of temperatures. In this test an attached flywheel torsionally deforms a specimen, which is allowed to oscillate a in free vibration SIGNIFICANCE: • Determines the effect of elevated temperature on dynamic mechanical properties of plastics. • Provides a indication of a materials upper use temperature limit for short-term exposure and degradation phenomenon in polymeric materials. • Gives a quantitative idea on glass transition temperature & crystalline melting point in polymers. • Test method: ASTMD 2236, DIN 53445 • Test Specimen: Specimens of rectangular or cylindrical shape and different length and width are used Corporate Training & Planning

  19. TORSION PENDULUM TEST (THERMAL ENDURANCE) • APPARATUS • Rigidly fixed & movable clamp • Disk or a rod with a known moment of inertia • A differential transformer • Strip chart recorder • An insulated chamber • Heater Torsion Pendulum tester for determining shear modulus in plastic materials Corporate Training & Planning

  20. TORSION PENDULUM TEST (THERMAL ENDURANCE) • PROCEDURE • The temp equilibrium should be established first in the chamber. • The clamped specimen is put into oscillation and the period and rate of decay of the amplitude of oscillation are measured. • The elastic shear modulus is calculated from the specimen dimensions, moment of inertia of the movable chamber and period of movement. • RESULTS & CONCLUSION • The log decrement is observed to be an approximate 1st derivative of the modulus temperature curve • The maximum at temperatures at which the modulus shows rapid drop. indicates the effective maximum load – bearing temp. Corporate Training & Planning

  21. TORSION PENDULUM TEST (THERMAL ENDURANCE) • FACTORS INFLUENCING • Specimen thickness, strain rate influences the test values • Modulus increases with the incorporation of fibres/reinforcements • Incorporation of additives also influences the storage & loss modulus along with the damping characteristics. Corporate Training & Planning

  22. TORSION PENDULUM TEST (THERMAL ENDURANCE) CASE STUDY • Shear modulus vs Temp. graph shows the effects of glass transition temperature. • The modulus is very high at the beginning of the curve which decreases slowly as the temperature increases. • Near the glass transition temperature the modulus decreases very rapidly in a short temperature span. Corporate Training & Planning

  23. TORSION PENDULUM TEST (THERMAL ENDURANCE) CASE STUDY Shear modulus & tan d of Makrolon 280 & Makrolon 8030 PC resins. • The damping expressed as log decrement is calculated from the rate at which the amplitude of oscillation decreases. • The plot of log decrement versus temperature shows the onset of the transition and this temperature is regarded as the maximum usable load-bearing temperature. Corporate Training & Planning

  24. THERMAL CONDUCTIVITY • Rate at which heat is transferred by conduction through a unit cross sectional area of a material when a temperature gradient exists perpendicular to the area. • The coefficient of thermal conductivity (K factor), is defined as the quantity of heat that passes through a unit cube of the substance in a given unit time when the difference in temperature of the two faces is 10C. • Mathematically, thermal conductivity is expressed as K = Qt/A(T1-T2) • Q = amount of heat passing through a cross section, A causing a temperature difference, ∆T (T1-T2), t = thickness of the specimen. • K is the thermal conductivity, typically measured as BTU.in / (hr.ft2.0F) indicates the materials ability to conduct heat energy. Corporate Training & Planning

  25. THERMAL CONDUCTIVITY • SIGNIFICANCE • Thermal conductivity is particularly important in applications such as headlight housings, pot handles & hair curlers that require thermal insulation or heat dissipation properties. • Computerized mold-filling analysis programs requires special thermal conductivity data derived at higher temperatures than specified by most tests. • TEST METHODS & SPECIMEN • Test method: Guarded hot plate test ASTM 177, ISO 2582 • Test Specimen: Two identical specimens having plane surface of such size as to completely cover the heating unit surface • The thickness should be greater than that for which the apparent thermal resistivity does not change by more than 2% with further increase in thickness Corporate Training & Planning

  26. THERMAL CONDUCTIVITY APPARATUS The apparatus is broadly of two different categories of the following: • Type I (low temperature) Temperature of cold plate : 21 K, Temperature of heating unit: <500 K • Type II (High temperature) Temperature of heating unit range:>550 K -<1350K • Heating units • Gap & Metering Area • Unbalance Detectors • Cooling units • Sensors for measuring Temperature difference • Clamping force • Measuring system for Temperature detector outputs Corporate Training & Planning

  27. GUARDED HOT PLATE APPARATUS Guarded Hot plate Apparatus Courtesy: Bayer Material Data Sheet Corporate Training & Planning

  28. THERMAL CONDUCTIVITY PROCEDURE • Two test specimens are sandwiched between the heat source (main heater) & heat sink; one on either side of the heat source. • The clamping force is so adjusted that the specimens remain in perfect contact with the heater & sink • Guard heaters are provided to prevent heat flow in all except in the axial direction towards the specimen • The time of stabilization of input & out put temperature is noted. • Temperature difference between the hot & cold surfaces of the specimen should not be less that 5 K or suitable differences as required. Corporate Training & Planning

  29. THERMAL CONDUCTIVITY CALCULATION • The relationship between the quantity of heat flow and thermal conductivity is defined as Q ~ K x Q = Quantity of heat flow K = Thermal Conductivity X = The distance the heat must flow • Thermal conductivity is calculated as : K = Qt / A (T1 – T2) Q = Rate of heat flow (w) T = Thickness of specimen (m) A = Area under test (m2) T1 = Temperature of hot surface of specimen (k) T2 = Temperature of cold surface of specimen (k) Corporate Training & Planning

  30. THERMAL CONDUCTIVITY RESULTS & CONCLUSION • Thermal conductivity is calculated by using the value of rate of flow at a fixed temperature gradient. • Data are obtained in the steady state FACTORS INFLUENCING • Crystallites have higher conductivity. • As the density of the cellular plastic decreases, the conductivity also decreases up to a minimum value and rises again due to increased convection effects caused by a higher proportion of open cells. Corporate Training & Planning

  31. THERMAL CONDUCTIVITY CASE STUDY • Variation of thermal conductivity with temperature Corporate Training & Planning

  32. THERMAL EXPANSION (COEFFICIENT OF LINEAR THERMAL EXPANSION, CLTE) • Measures the change in length per unit length of a material, per unit change in temperature. • Expressed as in/in/0F or cm/cm/0C • Mathematically, CLTE (α), between temperatures T1 & T2 for a specimen of length L0 at the reference temperature, is given by : • α = (L2 – L1)/[L0(T2 – T1­)] = L/L0ΔT • SIGNIFICANCE • Determines the rate at which a material expands as a function of temperature. • The higher the value for this coefficient the more a material expands and contracts with temperature changes. • Plastics tend to expand and contract anywhere from six to nine times more than materials that are metallic. • The thermal expansion difference develops internal stresses and stress concentrations in the polymer, which allows premature failure to occur. Corporate Training & Planning

  33. THERMAL EXPANSION (COEFFICIENT OF LINEAR THERMAL EXPANSION, CLTE) Test Method: • ASTMD 696 Test Specimen: • 12.5 by 6.3mm (½ in. by ¼ in.) 12.5 by 3mm (½ by ⅛ in.), 12.5mm (½ in.) in diameter or 6.3mm (¼ in.) in diameter. Conditioning: • 23 ± 2oC & 50 ± 5% RH for not less than 40h prior to test. Corporate Training & Planning

  34. THERMAL EXPANSION (COEFFICIENT OF LINEAR THERMAL EXPANSION, CLTE) • APPARATUS • A vitreous silica dilometer • Dial gage • The weight of the inner silica tube + the measuring device reaction shall not exert a stress > 70 kPa on the specimen so that the specimen is not distorted or appreciably indented. • Scale or Caliper • Controlled Temperature Environment • Means shall be provided for stirring the bath • Thermometer or thermocouple Corporate Training & Planning 34

  35. THERMAL EXPANSION (COEFFICIENT OF LINEAR THERMAL EXPANSION, CLTE) PROCEDURE • Measure the length of two conditioned specimen at room temperature • Mount each specimen in a dilatometer, install the dilatometer in the –30oC control environment. • Maintain the temperature of the bath in the range –32oC to –28oC ± 0.2oC until temperature of the specimen along the length is constant • Record the actual temperature and the measuring device reading. • Change to the + 30oC bath, so that the top of the specimen is at least 50mm below the liquid level of the bath. Corporate Training & Planning

  36. THERMAL EXPANSION (COEFFICIENT OF LINEAR THERMAL EXPANSION, CLTE) PROCEDURE • Maintain the temperature of the bath in the range from + 28 to 32oC ± 0.2oC • Record the actual temperature and the measuring device reading. • Change to –30oC and repeat the above procedure & measure the final length of the specimen at room temperature. • If the change in length per degree of temperature difference due to heating does not agree with the change length per degree due to cooling within 10% of their average investigate the cause of the discrepancy and if possible eliminate. • Repeat the test until agreement is reached. Corporate Training & Planning

  37. THERMAL EXPANSION (COEFFICIENT OF LINEAR THERMAL EXPANSION, CLTE) CALCULATION Calculate the CLTE over the temperature range as: α = ΔL/LoΔT α = Average coefficient of linear thermal expansion degree Celsius. ΔL = Change in length of test specimen due to heating or to cooling, Lo = Length of test specimen at room temperature (ΔL &Lo being measured in the same units), and ΔT = Temperature differences, oC, over which the change in the length of the specimen is measured. The values of α for heating and for cooling shall be averaged to give the value to be reported. Corporate Training & Planning

  38. THERMAL EXPANSION (COEFFICIENT OF LINEAR THERMAL EXPANSION, CLTE) RESULT & CONCLUSION • Provide a means of determining the CLTE of plastics, which are not distorted or indented by the thrust of the dilatometer on the specimen. • The specimen is placed at the bottom of the outer dilatometer tube with the inner one resting on it. • The measuring device, which is firmly, attached to the outer tube is in contact with top of the inner tube and indicates variations in the length of the specimen with changes in temperature. • Temperature changes are brought about by immersing the outer tube in a liquid bath or other controlled temperature environment maintained at the desired temperature. • The nature of most plastics and the construction of the dilatometer make –30 to +30oC a convenient temperature ranges for linear thermal expansion measurements of plastics. • This range covers the temperatures in which plastics are most commonly used. Corporate Training & Planning

  39. THERMAL EXPANSION (COEFFICIENT OF LINEAR THERMAL EXPANSION, CLTE) FACTORS INFLUENCING • Thermal expansion is substantially affected • by the use of additives • especially fillers • Wt% Of loading • Lowers the coefficient of thermal expansion. Corporate Training & Planning

  40. FLAMMABILITY • Plastics are carbon-based materials and burn and give off gases and smoke when subjected to a flame. • Plastics are excellent fuels but are generally classed as ordinary combustibles • For combustion to take place, three components form the 'fire triangle’ Corporate Training & Planning

  41. FLAMMABILITY THE PROCESS OF COMBUSTION IN PLASTICS FOLLOWS 6 SEPARATE STAGES TESTING FOR FLAMMABILITY UL 94 Limiting Oxygen Index Rate of burning Smoke density Corporate Training & Planning

  42. FLAMMABILITY - UL 94 • Method of classifying a material’s tendency to either extinguish or spread a flame once it has been ignited SIGNIFICANCE • 12 flame classifications specified in UL 94. • Describes materials burning characteristics after test specimens have been exposed to a specific test flame under controlled laboratory conditions. • The classifications relate to rate of burning time to extinguish ability to resist dripping and whether or not the drips are burning. Test Method: IEC 60707, 60695-11-10, 60695-11-20, ISO 9772 & 9773. Specimen: 125 x 15 mm (5 x ½ in) Conditioning: 23 ± 2oC & 50 ± 5% RH for not less than 40h prior to the test. Corporate Training & Planning

  43. FLAMMABILITY - UL 94 APPARATUS • Fume Hood • Laboratory Burner • Burner Wing Tip • Ring Stands • Timing Devices • Measuring Scale • Wire Gauze • Conditioning Room or Chamber • HB Support Fixture • Micrometer • Desiccator • Conditioning Oven • Specimen Mandrel Form • Tape • Support-Gauze • Manometer/Pressure Gage Flow Meter Corporate Training & Planning

  44. FLAMMABILITY - UL 94 PROCEDURE • Horizontal Testing (HB) • Specimen is supported in a horizontal position, tilted at 45°. • Flame applied to the end of the specimen for 30 seconds or until the flame reaches the 1 inch mark. • If the specimen continues to burn after the removal of the flame, the time for the specimen to burn between the 1 and 4 inch marks are recorded. • If the specimen stops burning before the flame spreads to the 4 inch mark, the time of combustion and damaged length between the two marks is recorded. • Three specimens are tested for each thickness. Corporate Training & Planning

  45. FLAMMABILITY - UL 94 HORIZONTAL TESTING (HB) Corporate Training & Planning

  46. FLAMMABILITY - UL 94 VERTICAL TESTING (V-0, V-1, V-2) • A specimen is supported in a vertical position and a flame is applied to the bottom of the specimen. • The flame is applied for 10 secsand then removed until flaming stops at which time the flame is reapplied for another 10 secs and then removed. • Two sets of five specimens are tested. • The two sets are conditioned under different conditions. Corporate Training & Planning 46

  47. FLAMMABILITY - UL 94 VERTICAL TESTING (V-0, V-1, V-2) Corporate Training & Planning 47

  48. FLAMMABILITY - UL 94 VERTICAL TESTING (V-0, V-1, V-2) Corporate Training & Planning 48

  49. FLAMMABILITY - UL 94 VERTICAL TESTING (V-0, V-1, V-2) Corporate Training & Planning 49

  50. FLAMMABILITY - UL 94 VERTICAL TESTING (5V, 5V-A, 5V-B) • Tests on both bar and plaque specimens. • Bar specimen supported in a vertical position • flame is applied to lower corners of the specimen at a 20° angle. • flame is applied for 5 seconds and is removed for 5 seconds. • flame application and removal is repeated five times. • Plaques specimen mounted horizontally • flame applied to the center of the lower surface of the plaque. Corporate Training & Planning 50

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