FTIR Method
Purpose
This procedure utilizes Fourier transform infrared spectroscopy to measure the carbon dioxide concentration within carbonated beverage containers.
Preform and Bottle Testing
PTI offers over fourteen different tests for preform and bottle testing. If you would like to submit samples for testing please download and complete our Analytical Testing Sample Submission Form. If you have any questions, please contact us and we can help.
Acetaldehyde
AA Container Head Space
Purpose
This procedure measures the amount of acetaldehyde in PET bottles 24 hours after blow molding.
Description
Bottles are blow molded using standard blow air and flushed with nitrogen for 30 seconds and sealed approximately one hour after blow molding. The bottles are stored in a 72°F, 50% RH environment for 24 hours and then analyzed for acetaldehyde content in the bottle headspace at 24±1 hrs of age. A suitable standard is prepared and used to calibrate the gas chromatograph. The maximum height of the AA peak for the sample is compared against the AA peak for a known standard to determine the amount of AA within the bottle headspace.
AA Generation, Resin
Purpose
Determine the AA generated by a resin as a function of time at a given temperature.
Description
PET resin or preform samples are ground to a small particle size. A known weight of this ground material is sealed into a glass vial equipped with a teflon-lined rubber septum. These vials are then heated to drive the AA to the headspace of the vial. A sample of the equilibrated headspace in the vial is removed and is injected into a gas chromatograph and the software measures the acetaldehyde peak area. A suitable acetaldehyde standard is used to calibrate the gas chromatograph. This is then used to calculate the amount of acetaldehyde in the samples.
Burst Pressure
Purpose
This procedure evaluates the performance of a bottle when the container is pressurized to very high levels. Failure location reveals weak areas of the bottle.
Description
Bottles are pressurized with air and water in the AGR PPT burst testing device. Pressure is added until the bottle fails or the testing limits are met. The PPT burst tester can be programmed to run many different pressure profiles from quick jumps to elevated pressures with hold times. Profiles can also be created for cycle testing and step pressure increases.
Carbon Dioxide Retention Testing
Description
CO2 absorbs IR radiation in a very specific range of wavelengths. As the concentration of carbon dioxide decreases the measured CO2 absorption correspondingly decreases. The IR absorption value is divided by the length of the path through the container to account for the change in the container shape (there is usually a slightly shorter path length by end of test) over the time of the test. This calculation yields a concentration value for a particular sample. The concentration is then plotted against time to determine the rate of CO2 loss. The typical test time is 49 days with an interim report at 25 days.
CarboQC Method
Purpose
This procedure determines the CO2 shelf life of a given carbonated beverage container by evaluating the CO2 level within sample bottles over time using a CarboQC test instrument.
Description
The CarboQC uses an automated piercing method, which improves test repeatability as well as operator-to-operator test reproducibility relative to tests using a manual piercing method. It also corrects for the amount of air in the package and reports both the volumes of carbon dioxide with the impact of air factored out and the parts per million of air in the sample. Sixty bottles are carbonated to 4.2 ± 0.1 volumes CO2 and then stored in a constant temperature chamber at 72°F, 50% RH for the duration of the test procedure. Six bottle samples are destructively evaluated using the CarboQC to measure pressure and temperature data to calculate volumes of CO2 at the following intervals: 0 hrs, 24 hrs, 2, 4, 6, 9, 12, 16, 20 and 24 weeks. Packages are sampled by piercing them through the top panel of the closure with an automated sampling tube, then drawing a fixed volume of liquid into a test cell. After the aliquot has been drawn into the cell and equilibrated by agitation, the cell is expanded by first 10%, then by 30%, with the pressure and temperature being measured after each expansion. The pressure at 10% sample chamber expansion, the pressure at 30% sample chamber expansion, and measured temperatures are then used to calculate the CO2 volumes contained within the bottle and the average % CO2 loss per week is determined. The value of CO2 volumes calculated by this method is corrected for the air content in the sample. This correction is possible because of the differences in solubility of CO2 and air in water. As the test cell expands, the pressure contributed by CO2 will remain the same as more CO2 is pulled from the liquid phase, while the pressure contributed by air will drop as there is relatively minimal air dissolved in the liquid phase that can be drawn out to further fill the expanded cell headspace. Air content is also reported as parts per million of air. This test measures the CO2 loss from the entire package (bottle and closure) not just the bottle alone, as does Zahm & Nagel testing.
Differences from manual Zahm & Nagel testing:
- CarboQC measurements are more repeatable and reproducible because of the automated piercing and sampling.
- The CarboQC reports a more accurate CO2 content as the calculations subtract the pressure contribution from air or nitrogen.
- The CarboQC reports amount of air content in ppm in addition to volumes of CO2.
- Volumes of CO2 as reported by CarboQC will be nearly identical to volumes reported by Zahm & Nagel methods if the water is effectively de-aerated prior to carbonation as it is in many production filling operations. If the water is not de-aerated prior to carbonation, total pressure in packages measured by CarboQC to have the same volumes will be higher in package pressure by an amount proportional to the amount of pressure in the package due to air content. This higher pressure will vary depending on how much air is entrained in the water being used for filling, which depends on water temperature among other variables. Use of water without effective de-aeration will typically add pressure equivalent to another 0.2 to 0.5 volumes of CO2 content. Since this added pressure will lead to more tension stress for a package filled to a given “CarboQC volumes” than would be experienced by a package filled to the same nominal “Zahm & Nagel volumes,” it is critical that everyone who will use the results of the testing understand the effects of this difference on testing results.
PTI “Zahm & Nagel”
Purpose
This procedure determines the CO2 shelf life of a given carbonated beverage container by evaluating the CO2 level within sample bottles over time using a Zahm & Nagel test device.
Description
One hundred and twenty bottles are carbonated to 4.2° ± 0.1 volumes CO2 and then stored in a constant temperature chamber at 72°F, 50% RH for the duration of the test procedure. Twelve bottle samples are destructively evaluated using the Zahm & Nagel device for internal pressure and temperature at the following intervals: 0 hrs, 24 hrs, 2, 4, 6, 9, 12, 16, 20 and 24 weeks. The internal pressure and temperature are then correlated to the CO2 volumes contained within the bottle and the average % CO2 loss per week is determined. This test measures the CO2 loss from the entire package (bottle and closure) not just the bottle alone.
Coefficient of Friction Testing
Coefficient of Friction Testing
Purpose
This procedure determines the coefficient of friction between two PET film samples using an adapted version of ASTM D1894.
Description
Bottle samples are prepared and handled with gloves during both injection and blow molding to prevent contamination that might affect the COF results. The bottle sidewalls are cut from the bottle and one sidewall is mounted to a metal sled while the other sidewall is mounted to a flat plane. The COF assembly is then attached to the Instron machine and the force required to move the sled across the plane is measured using the 10lb load cell. The data is plotted as force (lbs) vs. the sled travel (in.) and is typically reported graphically. Our typical test usually results in a series of static COF values rather than an initial static value followed by a kinetic value; this is because our samples usually “jump” across the sidewalls rather than pull uniformly. The COF value is calculated by dividing the measured force by the weight of the sled.
Density
Preform Density
Purpose
This procedure determines a sample density and correlates that density to crystallinity using theoretical PET amorphous and crystalline densities according to ASTM D1505.
Description
Five samples are prepared by cutting approximately 1/4″ samples from a preform or bottle without touching the samples to prevent oils from disturbing the testing. The entrapped air is removed from the surface of the sample and the samples are then dropped into a density gradient column and allowed to settle for approximately 15 minutes. The height of the samples is then carefully measured. Standard density balls are used to calibrate the density of the column. The sample density is then correlated to the theoretical amorphous (1.3331) and crystalline (1.45234) PET densities to determine the % crystallinity.
Dimensions
Wall Thickness
Purpose
This procedure determines the wall thickness at given locations on samples using a magnetic thickness gauge.
Description
The heights where thickness readings will be taken are determined and then wall thicknesses are measured with a magnetic thickness gauge.
Section Weights
Purpose
This procedure determines the weight of specified container sections by physically cutting the container at defined locations.
Description
Twelve bottles are cut at given height locations (typically found on a container drawing or specified by a project engineer) and each section is weighed. The average and standard deviations are determined for each section. A general weight specification range will be the target weight + / -0.5g.
Finish Dimensions
Purpose
The Finish Dimensions test is designed to ensure that all thread finishes on bottles or preforms comply with the dimensions and allowable tolerances specified on the respective bottle finish design drawings. In addition, there shall be no continuous or excessive flash, and no overhang between the F and G dimensions.
Description
The laboratory should consult with the customer or bottle supplier (if the bottle supplier is not the customer) to ensure that copies of the most recent drawings are available for each finish that is specified for use with the bottles to be measured. Using an optical comparator of at least 20X magnification or a vision system, the following dimensions are typically evaluated, designations and descriptions are per ISBT:
- T: Thread crest diameter
- E: Thread root diameter
- A: Tamper evident bead diameter
- C: Control diameter (ID) at TOF (Top of finish)
- H: Clearance height required for proper closure function
- D: Tamper evident bead height measured from TOF to gauge pt
- X: Height from TOF to bottom of support ledge
Capacity Shrinkage
Purpose
This procedure determines the amount of shrinkage in a blown container in the first 24 hours after blow molding by evaluating the bottle height and diameters and overfill volume at 0.5, 5 and 24 hours.
Description
Six test bottles are measured 30 minutes, 5 hours and 24 hours after blow molding to determine the bottle height, diameters and overfill volume. The container shrinkage is then determined based on this information.
Bottle Dimensions
Purpose
This procedure is designed to measure the dimensions of a bottle to ensure the containers meet the requirements and tolerances specified on the bottle drawings.
DSC Thermal Analysis
Purpose
This procedure measures the quantity of energy absorbed or released as the temperature of a plastic sample increases from 30°C to 300°C, is quench cooled and then reheated from 30°C to 300°C.
Description
10mg of a finely ground sample is weighed out into an aluminum DSC boat. This sample is then heated to 30° above the anticipated melting temperature. It then is quickly quenched in liquid nitrogen to retain the properties of the material. At this point it then is reheated. During both of these heating periods, the caloric values of the energy required to make the temperature change are recorded. A graph is then produced and analyzed. From this analysis, glass transition temperature (Tg), crystallinity temperature (Tc) and melting temperature (Tm) are determined.
Hot Fill (Container)
Purpose
This procedure evaluates the performance of a heat set bottle when filled with heated water. The methodology used simulates filling and capping as found in production.
Description
The physical measuring consists of the following: initial bottle diameters measured at designated heights 90° from the parting lines, overall bottle heights and overfill volumes. After the initial measurements are taken, the bottles are filled to the brim with heated water. A head space is created after allowing the bottles to set for a pre-determined amount of time and the bottles are capped and sealed. The bottles are allowed to set for a pre-determined amount of time and are then immersed into cool water and remain there until the bottles are room temperature to touch. The bottles are then removed and dried. Final maximum and minimum diameter measurements are then taken at the same heights as the initial measurements. Overfill volumes are repeated and the overall heights are taken with the closure removed. The bottles are cut at designated heights and then weighed.
Impact
Dart Impact – Bruceton Staircase Method
Purpose
This procedure determines the weight, height and energy where a sample fails when it is impacted with a free-falling weight using the Bruceton Staircase Method.
Description
Samples are prepared as for ASTM D3029-F and impact tested using the drop weight impact tester. If the sample did not fail at a given height/ weight, either the height or weight is increased incrementally until failure occurs. Once failure has occurred, the height/weight is decreased by the same increment and the process is repeated until all samples are utilized. Typically, an odd number of samples are used for the Bruceton Staircase technique to obtain several data points around the breakage point.
Preform Dart Impact – ASTM D3029-F
Purpose
This procedure determines the weight, height and energy at which a sample fails when it is impacted with a free-falling weight according to ASTM D3029-F.
Description
A drop weight impact tester is used to drop a weighted dart onto a specimen that has been clamped into a flat position. The dart weight is increased incrementally until at least half of the samples tested fail. Each sample is tested only once. The drop height may also be adjusted to increase the dart velocity upon impact.
Solution Intrinsic Viscosity
Purpose
This procedure is used to determine the intrinsic viscosity (IV) of the material. IV is a measure of the Molecular Weight (MW) of PET. The properties of PET are better at higher MW (higher IV) and worse at lower MW (lower IV). Comparing the SIV results from resin and molded parts can provide an understanding of the drying and process conditions.
Description
The test procedure used is ASTM D4603. The solvent system used is 60% phenol/ 40% tetrachloroethane. The PET concentration is 0.50% and samples are analyzed at 30°C. The test can be run on resin, film, preforms and bottles. Corrections are made for samples if they contain >1.% additives or colorants. It is important to know the level of additives present when submitting a sample for analysis. PTI uses Rheotek equipment to measure IV . SIV data reported to the customer will be measured at a single concentration to obtain the inherent viscosity. The intrinsic viscosity is mathematically calculated from the inherent viscosity using the Billmeyer Equation.
Moisture Analysis
Purpose
This procedure measures the amount of moisture within a sample.
Description
A sample is deposited into the analyzer and heated to release all of the moisture within the sample. The moisture then reacts with the iodine and generates a current which allows for an accurate measurement to be made. Once the analyzer moisture reading falls to within the background reading, the analyzer calculates the ppm moisture by the calculated weight of water (reacted with the iodine) divided by the input sample weight.
Permeability Measurements
Oxygen – Container
Purpose
This procedure measures the permeation rate of oxygen through a container or film using a MOCON OX-Tran or Oxysense. The device will be selected based on the scope of the testing and the requirements of the container.
Pasteurization
Purpose
This procedure tests the performance of bottles as they are pasteurized.
Description
Eight (8) bottles are measured to determine the bottle diameters at several locations, the base material distribution, the push-up height, the overfill volume and the perpendicularity. The bottles are then carbonated to 2.95-3.13 volumes of CO2, and allowed to equilibrate. The bottles are placed into a pasteurization spray chamber and sprayed with controlled hot water until the internal water temperature reaches the targeted temperature at the coldest spot in the container. The temperature is then maintained for a predetermined amount of time. The bottles are then sprayed with cold water until the internal water temperature decreases to 40°C. The bottles are then removed and remeasured.
Sidewall Tensiles
Purpose
This procedure is used to measure properties like the elastic modulus, the stress and the strain properties of a material using either injection molded tensile bar specimens or thin sidewall specimens cut from container.
Description
The Instron is programmed to pull the specimen at a specific rate until the specimen breaks. Data is collect continuously during the test and Stress vs. Strain curves are generated from this information. These curves are then analyzed and information such as the elastic modulus, % strain at yield, % strain at break, stress at yield (psi) and stress at break (psi) are reported.
Stress Crack
Preform ISBT
Purpose
This procedure evaluates the performance of bottle bases when they are exposed to a 0.2% solution of NaOH (Sodium Hydroxide) to simulate the failure associated with Stress Cracking.
Description
Each bottle is filled to net target content with water equilibrated to 22°C +/- 1°C (72 +/- 2°F). Bottles are pressurized with compressed air to the equivalent internal pressure of 531 +/- 4 kilopasclals (77 +/-0.5 psi). After 5 minutes, the fill line on each of the bottles is marked and they are placed in individual pockets of 0.2% Sodium Hydroxide solution. The containers remain in the caustic solution until they fail by either catastrophic burst or leaking through cracks that develop in the base. The time to failure is recorded for each container. Failed containers are removed and the location of the failure is determined and recorded.
Standard PET Industry 28 Day Test Method
Purpose
This procedure evaluates the performance of PET bottles when they are dipped in a stress agent and then subjected to high temperature and high humidity conditions.
Description
Bottles are carbonated to a predetermined elevated CO2 level and then placed in the 100°F, 85% RH chamber overnight. These bottles are then dipped in a stress crack agent such that the entire base of the bottle is covered with the agent. The bottles are then placed back into the 100°F, 85% RH chamber for a period of 28 days. During this period, bottles are examined daily and all breakers, leakers and pressure loss bottles are recorded and removed from the chamber. At the conclusion of the 28 days, the remaining bottles are removed and checked for pressure to assure that none were missed during the 28 days of the test. A report of the bottle performance is then created.This procedure evaluates the performance of PET bottles when they are dipped in a stress agent and then subjected to high temperature and high humidity conditions.
Thermal Stability
Purpose
The Thermal Stability Test is designed to insure that dimensional changes in carbonated PET bottles will not be excessive during their expected lifetime. This is also known as a “creep” test.
Description
Representative bottles are measured under “as-received” non-carbonated conditions. Bottles are then carbonated and placed in an environmental room at 37.8°C ± 2.5° (100°F ± 5°) and 85% ± 10% humidity for 24 hours. After this time, bottles are removed from the room and re-measured (final measurements). These final measurements must be completed within 4 hours of removal from the environmental chamber and must be made at the same locations as the initial measurements. A comparison is then made between the “as-received” and the final measurements.
Tilt Test
Preform Tilt Test
Purpose
This procedure determines the angle at which a bottle will tip and fall once the center of gravity has been overcome on tilting.
Description
A tilt test device is fitted with the appropriate surface. The test device is then tipped until a test bottle breaks the plane of contact because the center of gravity of the bottle has been overcome. The angle at which this tipping occurs is considered the tilt angle. Typically, twelve bottles are tested and the average tilt angle is determined for the set of bottles.
Top Load
Purpose
To ensure that the vertical strength of PET bottles is sufficient to meet minimum performance standards for vertical loading as might be encountered during bottle filling, capping and stacking of filled product.
Volumes
Capacity
Purpose
This procedure is used to determine the overfill (brimful) and fill line volume of each container in a set. This test can be used for either statistical information like average and standard deviation numbers or can be used to obtain mold specific information. Our typical test is either 12 samples chosen at random from a full mold round or it could be one container from each blow mold cavity.
Description
The overfill and fill line volumes are determined on twelve containers. Overfill is simply filling the container to a level equal to the top of the finish of the container. The typical methods for measuring fill line volume are: 1. Filling the container to a specific height and measuring the volume at that point. 2. Filling the container with a specific volume of water and measuring the height of the liquid and comparing it to the target height. The weight of the water at these two points is used to calculate the volume of the container by dividing the weight by the density of water at the recorded temperature.
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