Scope: The Ash Content test is used to determine the amount of fillers in a specimen after the polymer has been burned off.
Generally, a 2g sample is weighed out and placed into a dried crucible. The sample is then burned in a muffle furnace at 600°C until the entire polymer has been burned off. The crucibles are then placed into desiccators to cool. The ash that is left in the crucibles is then weighed to give the ash content of the specimen.
Scope: Bulk density is defined as the weight per unit volume of material. Bulk density is primarily used for powders or pellets.
A funnel is suspended above a measuring cylinder. The funnel is filled with the sample and allowed to freely flow into the measuring cylinder. The excess material on top of the measuring cylinder is scraped off with a straight edge. The sample and the cylinder is then weighed and the weight / volume (Bulk Density) is determined.
Scope: Compression set testing is used to determine the ability of elastomeric materials to maintain elastic properties after prolonged compressive stress.
The thickness of the original specimen is measured. The specimen is then placed between spacers and in the compression device. The specimen is compressed to 25% of its original height, using spacers to accurately measure the compression. Within two hours of assembly, the compression device is placed in an oven at a specified temperature for the suggested time periods of 22 hours and 70 hours. After removing the sample from the oven, the specimen is allowed to cool for 30 minutes before measuring the final thickness
Scope: Charpy Impact is a single point test that measures a materials resistance to impact from a swinging pendulum. Charpy impact is defined as the kinetic energy needed to initiate fracture and continue the fracture until the specimen is broken.
The specimen is mounted horizontally and supported unclamped at both ends. The hammer is released and allowed to strike through the specimen. If breakage does not occur, a heavier hammer is used until failure occurs.
Scope: Determination of carbon black content in Olefin materials like polyethylene or polypropylene that do not contain nonvolatile additives or fillers.
A sample of known weight is placed into a weighed combustion boat. The sample is then placed into a 600�C tube furnace under a dry oxygen free Nitrogen purge. After a set time the combustion boat with the burn residue is cooled under the nitrogen purge and weighed. The combustion boat is then placed into a 600�C muffle furnace to oxidize the carbon residue. When the carbon is completely oxidized the combustion boat is cooled and weighed.
Scope:The test is used to determine the kinetic (moving) and static (starting) resistance of one surface being dragged across another.
A specimen is attached to a sled of specified weight. The sled is pulled across a second surface at a speed of 150 mm/minute. The force to get the sled started (static) and to maintain motion (kinetic) is measured
Scope: Heat deflection temp. is defined as the temperature at which a standard test bar deflects a specified distance under a load.
The bars are placed under the deflection measuring device. A load of 0.45 MPa or 1.80 MPa is placed on each specimen. The specimens are then lowered into a silicone oil bath where the temperature is raised at 2� C per minute until they deflect 0.25 mm for ASTM, 0.32 mm for ISO flatwise, and 0.34 mm for ISO edgewise.
Scope: Density is the mass per unit volume of a material. Specific gravity is a measure of the ratio of mass of a given volume of material at 23�C to the same volume of deionized water.
There are two basic test procedures, Method A and Method B. The more common being Method A, can be used with sheet, rod, tube and molded articles. For Method A, the specimen is weighed in air then weighed when immersed in distilled water at 23�C using a sinker and wire to hold the specimen completely submerged as required. Density and Specific Gravity are calculated.
Scope: Durometer Hardness is used to determine the relative hardness of soft materials, usually plastic or rubber. The test measures the penetration of a specified indentor into the material under specified conditions of force and time.
The specimen is first placed on a hard flat surface. The indentor for the instrument is then pressed into the specimen making sure that it is parallel to the surface. The hardness is read within one second (or as specified by the customer) of firm contact with the specimen.
Scope: Using a DSC (differential scanning calorimeter) the following are commonly found: Tg = Glass Transition Temperature = The temperature (�C) at which an amorphous polymer or an amorphous part of a crystalline polymer goes from a hard, brittle state to a soft, rubbery state.
Tm = Melting point = The temperature (�C) at which a crystalline polymer melts.
D Hm = The amount of energy in (joules/gram) a sample absorbs while melting.
Tc = Crystallization point = is the temperature at which a polymer crystallizes upon heating.
D Hc = The amount of energy (joules/gram) a sample releases while crystallizing.
The data can be used to identify materials, differentiate homopolymers from copolymers or to characterize materials for their thermal performance.
A sample of 10 to 20 mg. in an aluminum sample pan is placed into the differential scanning calorimeter. The sample is heated at a controlled rate (usually 10�/min) and a plot of heat flow versus temperature is produced. The resulting thermogram is then analyzed.
Scope: Dielectric Constant is used to determine the ability of an insulator to store electrical energy. The dielectric constant is the ratio of the capacitance induced by two metallic plates with an insulator between them to the capacitance of the same plates with air or a vacuum between them. Dissipation factor is defined as the reciprocal of the ratio between the insulating materials capacitive reactance to its resistance at a specified frequency. It measures the inefficiency of an insulating material. If a material were to be used for strictly insulating purposes, it would be better to have a lower dielectric constant.
A sample is placed between two metallic plates and capacitance is measured. A second run is made without the specimen between the two electrodes. The ratio of these two values is the dielectric constant.
Scope: The Flexural test measures the force required to bend a beam under 3 point loading conditions. The data is often used to select materials for parts that will support loads without flexing. Flexural modulus is used as an indication of a material�s stiffness when flexed. Since the physical properties of many materials (especially thermoplastics) can vary depending on ambient temperature, it is sometimes appropriate to test materials at temperatures that simulate the intended end use environment.
Most commonly the specimen lies on a support span and the load is applied to the center by the loading nose producing three point bending at a specified rate. The parameters for this test are the support span; the speed of the loading; and the maximum deflection for the test. These parameters are based on the test specimen thickness, and are defined differently by ASTM and ISO.
Scope: The flammability test is used to determine the relative rate of burning of self-supporting plastics. This test is mainly used for quality control, production control and material comparisons. It cannot be used as a criterion for fire hazard.
The various flammability tests are all similar in that they (1) orient a test sample either horizontally or vertically and place it in a test chamber; (2) apply a flame from a Bunsen Burner for a specified time; and (3) measure the time or distance that the flame propagates.
Scope: Falling dart impact is a traditional method for evaluating the impact strength or toughness of a plastic film. This test uses a single dart configuration and a single drop height, while varying the weight of the dart. Test results can be used either as a quality control evaluation or for end use comparisons.
The test specimen is clamped securely in a pneumatic ring at the base of the drop tower. The mounting bracket is adjusted to the appropriate drop height, and the dart is inserted into the bracket. The dart is released to drop onto the center of the test specimen. The drop weight and the test result (pass / fail) are recorded. Test method A specifies a dart with a 38 mm (1.5") diameter dropped from 0.66 m (26") Test method B specifies a dart with a 51 mm (2") diameter dropped from 1.5 m (60")
Scope: Notched Izod Impact is a single point test that measures a materials resistance to impact from a swinging pendulum. Izod impact is defined as the kinetic energy needed to initiate fracture and continue the fracture until the specimen is broken.
The specimen is clamped into the pendulum impact test fixture with the notched side facing the striking edge of the pendulum. The pendulum is released and allowed to strike through the specimen. If breakage does not occur, a heavier hammer is used until failure occurs.
Scope: Melt Flow Rate measures the rate of extrusion of thermoplastics through an orifice at a prescribed temperature and load.
The material is loaded into the barrel of the melt flow apparatus, which has been heated to a temperature specified for the material. A weight specified for the material is applied to a plunger and the molten material is forced through the die. A timed extrudate is collected and weighed. MFR values are calculated in g/10 min.
Scope: To determine the minimum concentration of oxygen in an oxygen/nitrogen mixture that will support a flaming burn in a plastic specimen. There is no correlation to real end use conditions.
The test sample is positioned vertically in a glass chimney, and an oxygen/nitrogen environment is established with a flow from the bottom of the chimney. The top edge of the test sample is ignited, and the oxygen concentration in the flow is decreased until the flame is no longer supported.
Scope: The Peel Test measures the strength required to pull apart a bonded surface. It is useful in evaluating adhesives, adhesive tapes, or other attachment methods.
The sample is measured for thickness, it is placed in a fixture in a universal tester. The specimen is pulled at the specified speed until either the part or the bond fails. Types of failure are noted as cohesive, adhesive, or substrate failure.
Scope: Accelerated weathering simulates damaging effects of long term outdoor exposure of materials and coatings by exposing test samples to varying conditions of the most aggressive components of weathering - ultraviolet radiation, moisture and heat. A QUV test chamber uses fluorescent lamps to provide a radiation spectrum centered in the ultraviolet wavelengths. Moisture is provided by forced condensation, and temperature is controlled by heaters.
Up to 20 test samples are mounted in the QUV and subjected to a cycle of exposure to intense ultraviolet radiation followed by moisture exposure by condensation. Various cycles are defined depending upon the intended end use application e.g., a typical cycle for automotive exterior applications would be 8 hours UV exposure at 70� C followed by 4 hours of condensation at 50� C. These cycles would be continued for extended periods of time - up to thousands of hours - simulating even longer periods of time in the real world.
Scope: This test covers the evaluation of plastic materials for resistance to chemical reagents, simulating performance in potential end use environments. Chemical reagents can include lubricants, cleaning agents, inks, foods, or anything else that the test material may be expected to come in contact with. The test includes provisions for reporting changes in weight, dimensions, appearance and strength properties. Provisions are made for various exposure times, strain conditions and elevated temperatures.
Multiple specimens, at least 5, should be used for each material/chemical/time/strain condition. Specimens can be weighed and measured prior to contact with the chemical reagent. To simulate end use stress in the test samples, strain jigs designed for ASTM izod bars or ASTM Type I tensile bars are used. Depending upon the type of contact anticipated for the test sample, the exposure to the chemical agent could be immersion, wipe, spray, or saturated gauze. The test samples are then sealed in a container, and either left at room temperature or placed in an oven. After the agreed upon period of time, the specimens are removed and evaluated for desired properties such as change in weight, appearance or tensile properties vs. controls.
Scope:Shear strength testing is used to determine the load at which a plastic or film will yield when sheared between two metal edges. Shear strength results are important to designers of film and sheet products that tend to be subjected to shear loads, or in applications where applied crushing loads are a risk.
The test is performed by clamping a test sample attached to a 1-inch punch between two metal fixtures. A male punch is then forced through the hole in the metal fixture causing shear along the edge of the hole. A universal testing machine is used to push the punch until shearing of the specimen occurs.
Scope: Surface resistivity is the resistance to leakage current along the surface of an insulating material. Volume resistivity is the resistance to leakage current through the body of an insulating material. The higher the surface/volume resistivity, the lower the leakage current and the less conductive the material is.
A standard size specimen is placed between two electrodes. For sixty seconds, a voltage is applied and the resistance is measured. Surface or volume resistivity is calculated, and apparent value is given (60 seconds electrification time)..
Scope: A pendulum impact tester is used to measure the force required to propagate an existing slit a fixed distance to the edge of the test sample. One use of these results would be for the specification of material and thickness for plastic film used in packaging.
Ten samples each are cut from the plastic film in the machine direction and in the transverse direction. A sample is positioned in the tester and clamped in place. A cutting knife in the tester is used to create a slit in the sample which ends 43mm from the far edge of the sample. The pendulum is released to propagate the slit through the remaining 43mm. The energy loss by the pendulum is used to calculate an average tearing force.
Scope: Tensile tests measure the force required to break a specimen and the extent to which the specimen stretches or elongates to that breaking point. Tensile tests produce a stress-strain diagram, which is used to determine tensile modulus. The data is often used to specify a material, to design parts to withstand application force and as a quality control check of materials.
Specimens are placed in the grips of the Instron at a specified grip separation and pulled until failure. For ASTM D638 the test speed is determined by the material specification. For ISO 527 the test speed is typically 5 or 50mm/min for measuring strength and elongation and 1mm/min for measuring modulus.
Scope: Tensile tests measure the force required to break a specimen and the extent to which the specimen stretches or elongates to that breaking point. The data is often used to specify material, to design parts to withstand application forces and as a quality control check of materials.
Place specimens in the grips of the Instron at a specified gage length and pull until failure. The testing speed is determined by the material specification. An extensometer can also be attached to test specimen to determine elongation and tensile modulus.
Scope:In a Thermo-gravimetric Analysis, the percent weight loss of a test sample is recorded while the sample is being heated at a uniform rate in an appropriate environment. The loss in weight over specific temperature ranges provides an indication of the composition of the sample, including volatiles and inert filler, as well as indications of thermal stability
Set the inert (usually N2) and oxidative (O2) gas flow rates to provide the appropriate environments for the test. Place the test material in the specimen holder and raise the furnace. Set the initial weight reading to 100%, then initiate the heating program. The gas environment is preselected for either a thermal decomposition (inert - nitrogen gas), an oxidative decomposition (air or oxygen), or a thermal-oxidative combination.
Scope: The Vicat softening temperature is the temperature at which a flat-ended needle penetrates the specimen to the depth of 1 mm under a specific load. The temperature reflects the point of softening to be expected when a material is used in an elevated temperature application.
A test specimen is placed in the testing apparatus so that the penetrating needle rests on its surface at least 1 mm from the edge.
A load of 10N or 50N is applied to the specimen. The specimen is then lowered into an oil bath at 23 degrees C. The bath is raised at a rate of 50� or 120� C per hour until the needle penetrates 1 mm.
Scope:Dilute Solution Viscosity is used as an indication of the molecular weight of polymers. The results of the test are expressed in Relative Viscosity, Inherent Viscosity, or Intrinsic Viscosity. It is used for polymers that dissolve completely without chemical reaction or degradation and can provide an excellent determination of lot-to-lot consistency or be used to compare molded parts to original resin for determinations of degradation from molding.
The polymer is first weighed and then dissolved in an appropriate solvent. The solution and viscometer are placed in a constant temperature water bath. Thermal equilibrium is obtained within the solution. The liquid is then brought above the upper graduation mark on the viscometer. The time for the solution to flow from the upper to lower graduation marks is recorded.
Scope: Water absorption is used to determine the amount of water absorbed under specified conditions. Factors affecting water absorption include: type of plastic, additives used, temperature and length of exposure. The data sheds light on the performance of the materials in water or humid environments.
For the water absorption test, the specimens are dried in an oven for a specified time and temperature and then placed in a desiccator to cool. Immediately upon cooling, the specimens are weighed. The material is then emerged in water at agreed upon conditions, often 23�C for 24 hours or until equilibrium. Specimens are removed, patted dry with a lint free cloth, and weighed.
Scope:Accelerated weathering simulates the damaging effects of long term outdoor exposure of materials and coatings by exposing test samples to varying conditions of the most aggressive components of weathering - light, moisture, and heat. A Weather-Ometer uses a xenon arc light source to provide a radiation spectrum that simulates natural sunlight. Glass filters around the xenon arc temperature is controlled by heaters. Microprocessors monitor and precisely control the radiation applied to the test samples. No direct correlation can be made between accelerated weathering duration and actual outdoor exposure duration. However, modify the light spectrum to simulate the appropriate end use conditions. Moisture is provided by a humidifier and direct spray, and performance comparisons under the controlled conditions of accelerated weathering can be compared to documented performance of materials and coatings that have experienced extended periods of end use exposure.
Up to 60 test samples are mounted in the Xenon Arc and subjected to a cycle of exposure to specified combinations of light, humidity, temperature and water spray. Various cycles are defined by the appropriate specifications depending upon the intended end use application.
Polystyrene Lightfastness Standards are included among the test samples to monitor and verify the performance of the equipment. These cycles would be continued for extended periods of time - up to thousands of hours - simulating even longer periods of time in the real world.