Test of packaging materialPurpose of testing packaging material 1. 2. 3. 4. Selection of packaging material Comparison of two or more different packaging materials As an aid in designing of package Assure quality and conform specification In overall we test packaging material to see it’s whether it has the required functions. 1. Tensile Strength: It is a measure of film’s resistance to being pulled apart at a constant rate of speed. Maximum load that a material can support without fracture when being stretched, divided by the original cross-sectional area of the material. Tensile strengths have dimensions of force per unit area and in the English system of measurement are commonly expressed in units of pounds per square inch, often abbreviated to psi. When stresses less than the tensile strength are removed, a material returns are either completely or partially to its original shape and size. As the stress reaches the value of the tensile strength, however, a material, if ductile, that has already begun to flow plasticity rapidly forms a constricted region called a neck, where it then fractures. Tensile properties are an important and common way to compare physical properties of diverse materials, from steel to plastic. In the narrower realm of flexible films, these tests provide measurement of attributes we can see and feel: strength, stiffness, and resistance to stretching. The tensile strength of polypropylene increases significantly by the orientation process. Resin selection and orientation method are the primary variables that influence tensile values. Therefore, tensile properties are almost entirely defined by product design itself. Small variations in tensiles will inevitably result due to normal process variation, but the performance effect is insignificant. Test principles Each end of a film specimen, of specific width and measured thickness, is held by a clamp or grip. One grip is stationary, while the other is pulled away from the first at a pre-selected velocity. The machine continuously measures the changing distance between the grips and the force exerted on them as they pull the film apart. The test is completed when the sample breaks. Today, most machines run automatically after the operator selects settings, loads the specimen, and initiates the test. Most are also equipped with microprocessors that perform the calculations and automatically display all the resulting values. But, the test concepts are best understood by studying loadextension curves like the ones shown in Graph 1. These are actual machine direction (MD) and transverse direction (TD) load-extension curves for a typical, tender-oriented, 75 gauges OPP. In Graph 1, load is plotted as a function of extension, and the tensile tester software calculates the following properties that are noted in Table 4. Standard laboratory temperature is 72°F (22°C) ± 2°F (1°C).Graph 1: Typical OPP load-extension curves Table 4: Tensile values from Graph 1 Results 1 Sample Description Thickness (mil) Ultimate Strength (kspi) Modulus (kpsi) Elongation (%) MD pull .75 39. A large value for elongation is an index of toughness. so it is important to conduct tests in a controlled environment. since it indicates a material will absorb a large amount .00075 in2 ÷ Extension (in) 2 in Extension at failure x 100 2 in Test conditions like pull speed.75 18. Other factors affecting the tensile strength are the composition of material.3 687 Table 4 values are software-generated results based on the following equations.00075 in Modulus (psi) = At any point on the elastic region tangent line (Stress ÷ Strain) = Load (lbf) Initial cross-sectional area Elongation (%) = ÷ Extension (in) Initial grip separation Extension at failure x 100 Initial grip separation = = Load (lbf) . Max Load (lbf) Initial cross-sectional area Ultimate Tensile Strength (psi) = 45 = Max Load (lbf) 1 in x . Tensile strength is a most important value for materials used in applications such as heavy-duty bags. and sample width will affect the results. their physical properties and Machinability. method of processing. Tensile properties can change with small changes in temperature.9 343 174 2 TC pull . full-scale load. initial grip separation. type of packaging material. The specimen is clamped between jaws in sigmoid shape. Tear strength is reported in grams. Samples of paper or film are clamped into the tester and nicked to start the . High tear values may be needed for machine operations or for package strength. low tear values are necessary and useful for easy opening of some package types. An instrument called Good Brand Tensile Tester is used for this purpose. Instrument Van der Korput Baarn Tensile Tester is used for this purpose. The force at which the specimen breaks is noted as kg/15mm. However. The specimen is clamped between jaws and pulling force is applied. The pendulum is released and the impact (kg. The paper is clamped in a sigmoid shape. then quickly releasing it. and a scale that registers the arc through which the released pendulum swings. means for holding this pendulum in a raised position. 2. This test is very important for all films as well as for paper. A tear tester has a stationary clamp and a movable clamp on a pendulum. Elongation is a strength property. A pendulum is released to cut the paper. Tear resistance It is the force necessary to continue tearing a sample after a nick has been made.of energy before breaking.cm) as registered on the scale is noted. It is measured by the same instrument on a calibrated scale (having a pointer) and the result is expressed as: % Elongation = (reading×100) / (2 inch) A schematic diagram of the instrument is given below: Dynamic Tensile Strength This measures the energy required to break a specimen of specified dimension by subjecting it to an impact stress. This test is important for construction of multiwall paper bags as it gives an index to the capacity of the sample to absorb impact shock. the bottom package in a stack during storage in a warehouse.tear. Tear test is of two types edge tearing and internal tearing. calibration of the arc gives the tear strength. An instrument named Tear-ASTM-D-1922 is most widely used for measuring tear resistance. This tears the sample and the scale registers the arc. Stack load test The Compression/Stacking Tests: This test is performed to assess the ability of a transport package to withstand compressive forces and to protect its contents during compression. Volume loss = weight loss/specific gravity. The test consists of abrading the sample with a wheel of standard abrasion pad (abradant) for a definite number of revolutions and finding its volume loss. As the arc is proportional to the tear strength of the sample. Resistance to abrasion This test is done to measure the ability of a packaging material to withstand surface wear during rubbing and friction. Fig: Drop testing of a box 4. 3. as in the picture beside. Drop test Drop Test: The test simulates actual shocks by dropping the package and its content freely against a rigid plane surface from a predetermined height. The test may also be used as a stacking test to investigate the performance of i. Internal tearing is mostly frequently used for measuring the tear resistance of papers and plastic films. processing method and the condition of testing. then the pendulum clamp is released. . a drop test can be conducted so that the package hits the surface diagonally against one corner. physical properties. For example. The tear resistance depends on the type of packaging material. 2.e. 6. A random (all frequencies at once) test is generally considered to more closely replicate a real world environment. even though most real-world vibration occurs in various axes simultaneously. but ExxonMobil has . Other "response" points experience maximum vibration level (resonance) or minimum vibration level (anti-resonance). This property is also important for finding the stacking height in a warehouse. usually with some type of shaker. The oscillations may be periodic such as the motion of a pendulum or random such as the movement of a tire on a gravel road. Generally. paper box. For higher frequencies. Vibration testing is accomplished by introducing a forcing function into a structure.The test is carried out by stacking the packaged material above one another or by placing a fixed weight above the unit pack for a certain time. released in late 2008. Gas transmission rate Water vapor transmission rate(WVTR) Definition WVTR (water vapor transmission rate) is the steady state rate at which water vapor permeates through a film at specified conditions of temperature and relative humidity. Most vibration testing is conducted in a single DUT axis at a time. Fig: compression testing of a wooden box. a DUT (device under test) is attached to the "table" of a shaker. 5. Test Method 527. Vibration test The Vibration Test: Various forms of transportation vibrations can be simulated in a laboratory through a vibration test. servo-hydraulic (electro-hydraulic) shakers are used. It can also be done by compressing a pack from two opposite sides and measuring the pressure applied to break/deform the container. Test conditions vary. The test-bench can be made to swing and vibrate in almost any direction with a number of frequencies and amplitudes to emulate the transportation being used. Overall migration test a. MIL-STD-810G. Sine (one-frequency-at-a-time) tests are performed to survey the structural response of the device under test (DUT). For relatively low frequency forcing.and sine test. cans and other secondary packaging material. one or more "input" or "control" points on the DUT are kept at a specified vibration level. This test is generally applicable in case of wooden box. Two typical types of vibration tests performed are random. electro-dynamics shakers are used. Alternately. such as road inputs to a moving automobile. Values are expressed in g/100 in 2/24 hr in US standard units and g/m2/24 hr in metric (or SI) units. Vibration refers to mechanical oscillations about an equilibrium point. Water vapor transmission rate b. paperboards. calls for multiple exciter testing. its WVTR will be half the value. trained operators using this type of instrumentation will generate values from .) 3.35 g/100 in2/24 hr. At this point. The partial pressure difference creates a driving force for the water vapor to permeate through the film to the low pressure side.." and therefore. chewing gum. bulk film property of OPP. which is the most common set of conditions reported in North America. Relevance to package performance A critical function of flexible packaging is to keep dry products dry (potato chips. Lower values indicate better moisture protection. fortune cookies. The order of water vapor resistivity in films of 1 mm is as follows.36 when testing a 1 mil OPP with a nominal WVTR of .) and moist products moist (cheese. and degree of crystallinity can account for up to a 10% difference in WVTR. 2. It is common to find variation in the reported WVTR values for same-gauge OPP films produced or measured by different manufacturers.. WVTR values. and chewy products are hard and dry.8°C) and 90% RH. products will quickly gain or lose moisture until they are at equilibrium with the environmental relative humidity. Raw material: Homopolymer PP resin differences in average molecular chain length. MOCON®. Measurement: The instrument manufacturer. Dry nitrogen gas is swept through a chamber where the test film acts as the membrane separating this dry gas stream from a "wet" nitrogen stream on the other side. WVTR is the standard measurement by which films are compared for their ability to resist moisture transmission. . In other words. Without protective packaging. Test principles ExxonMobil test cell looks like Figure below. orientation efficiently "packs" polymer chains. This is so because WVTR is an inherent. crispy products are soggy.. muffins. The barrier of the film determines how much water vapor can transfer. Therefore. The primary factors causing these differences are: 1. pretzels. so that larger spaces are minimized. Process conditions affect this "packing. range of chain lengths. because the crystalline regions of the polymer matrix are aligned.34 to .. Only values reported at the same temperature and humidity can be compared.states a test precision of :t3% with their PERMATRON-W® product line. BOPP > HDPE > cast PP >BPET >LDPE>EVOH at 100°F (38°C).standardized to 100°F (37. and this is continuously measured by an infrared detector in the outgoing stream of the dry side. Additives and copolymer resin layers can account for differences of up to 30%. 90% RH for 1 mil film What affects the WVTR of OPP films ? The most obvious factor that impacts WVTR is thickness: if an OPP of the same product design is twice as thick as another. (WVTR is reduced through orientation. because transmission rates are affected by both of these parameters. Process: Normal differences in process conditions between one orienter and another account for about 5% variation in WVTR values.). Most of the chemical and biological reactions that create rancid oils. Relevance to package performance The air we breathe is about 21% oxygen and 79% nitrogen. Essential to human and animal life. 1. with very small concentrations of other gases like carbon dioxide and argon.Figure 3: Cross-section of a WVTR test cell The test is complete when equilibrium. Oxygen transmission rate Definition OTR (oxygen transmission rate) is the steady state rate at which oxygen gas permeates through a film at specified conditions of temperature and relative humidity. The shelf lives of . So. Value are expressed in cc/100 in 2/24 hr in US standard units and cc/m2/24 hr in metric (or SI) units. or steady state. is achieved. Standard test conditions are 73°F (23°C) and 0% RH. This is also called gas flushing. which is when the infra-red sensor detects water molecules leaving the dry chamber at a constant rate. 90% RH. The most common replacement gases are nitrogen or nitrogen/carbon dioxide mixtures. There are two methods for reducing product exposure to oxygen via flexible packaging. it is not surprising that food packaging (and some non-food packaging for products where atmospheric oxygen causes harm) has progressed and found ways to reduce oxygen exposure and extend the shelf life of oxygen-sensitive products. MAP (modified atmosphere packaging) is a process for replacing the air in the headspace of a package with another gas before the final seal is made. This rate is the sample WVTR and is recorded in units of g-H2O/100 in2/24 hr at 100°F (37.8°C). molds. oxygen gas is also a reactive compound that is a key player in food spoilage. and flavor changes require oxygen in order to occur. The amount of water vapor permeating through the sample per unit time period is not changing. the thicker the oxygen barrier-providing layer. An industry rule-of-thumb is that a material is considered a "high oxygen barrier" if its OTR is less than 1 cc/100 in 2/24 hr (15.2. as well as those other properties necessary to produce a serviceable package. The second section displays the OTRs for coated or metallized films where the total film thickness is unimportant. 2.4 times the OTR value at 73ºF (23ºC). Vacuum packaging is where the atmosphere is drawn out and eliminated. Note that the table is divided into two sections.potato chips. the CO2 TR is approximately 1. Thickness of barrier layer: Generally. ExxonMobil does not perform transmission testing with these gases.2 . This vacuum forces the flexible material to conform to the product shape. because the barrier is primarily coming from the additional layer. Meats (fresh and processed) and cheeses are commonly packaged this way. and polymerization process: All PVdCs (or EVOHs or PVOHs) are not created equal. 1. and shredded cheese are commonly extended by this packaging method. 0% RH.5 cc/m2/24 hr). but needs moisture barrier and mechanical properties provided by layers that are coextruded or laminated around it. CO2 TR will be 3 to 5 times the OTR value at 73ºF (23ºC). but a value range can be estimated from OTR values by using the following relationships. Properties are compromised during polymer and product development. OTR is most affected by the following factors. at the same conditions. there must be an adequate oxygen barrier and seal integrity to keep a low oxygen concentration inside the pack. What affects the OTR of films Good oxygen barrier is achieved by combining functional layers to create a film with the required barrier. The first contains normalized (1 mil) values for common materials. For example. the better the barrier. Generally asked question: Many customers ask about the carbon dioxide (CO 2) and nitrogen (N2) transmission rates through film. dried fruits. 2. Copolymer ratio. Otherwise.2 to .0 cc/100 in2/24 hr and the N2 TR is approximately . OTR values are used to compare the relative oxygen barrier capabilities of packaging films. 16 cc/100 in2/24 hr. 0% RH N2 TR will be . the driving force created by the oxygen partial pressure differences (21% outside the bag and 0-2% inside the bag) will cause an ingress of oxygen and destroy the benefit of removing it in the first place. 0% RH For example. Table 10 shows OTR values for common polymer packaging films. But there are process and cost limitations that restrict the thicknesses that can be realistically produced or successfully utilized. rather than being replaced by another gas. There can be substantial . EVOH has exceptional OTR properties. the OTR of 110 AXT is . Therefore.08 to .40 cc/100 in 2/24 hr @ 73ºF (23ºC). so that total performance in target applications is optimized. Once air has been replaced or eliminated from the package. nuts. plasticizer content. differences in OTR values depending on the selections made.5 cc/100 in 2/24 hr and . It is important to discuss the effects of relative humidity on OTR. both ASB-X and AXT are PVdC-coated and sealable. For example. The partial pressure difference creates a driving force for oxygen molecules to diffuse through the film to the low pressure side. This is evidenced by Met PET's exceptional barrier. where the test film acts as the membrane separating this stream from an oxygen stream on the other side. 3. The film barrier determines the rate of oxygen permeation. Relative humidity has a dramatic and negative effect on the OTRs of some materials. The effect is especially pronounced at RHs over about 70%. and this is continuously measured by a MOCON® patented coulometric sensor in the outgoing . Figure 4: Cross-section of an OTR test cell The test is complete when equilibrium. 73°F (23°C) and 0% RH. 0% RH. it is complete when the sensor detects a constant amount of oxygen in the nitrogen carrier stream.stream of the nitrogen side. The rate of oxygen permeating through the sample is not changing. EVOH and PVOH. This rate is the sample OTR and is recorded in units of cc/100 in 2/24 hr or cc/m2/24 hr at 73°F (23°C). but their OTRs are 4. that is. a test cell looks like Figure 4. is achieved. ASB-X has the poorer OTR. . Dry nitrogen gas is swept through a chamber. or steady state. and to a lesser degree. but a broader seal range than AXT. even though the ASTM standard procedure is at dry conditions. 4. respectively. The standard test conditions are. as well as the difference in OTRs between various metallized OPP products Test Principle Conceptually. most notably nylon. Base film surface compatibility: The physical and chemical characteristics of the base film surface have a major effect on the OTR after metallization. after coating.40 cc/1 00 in 2/24 hr. 200 2300 . ExxonMobil uses 45-degree gloss. it is not valid to compare the gloss values of transparent films and opaque films. where the incident light beam strikes the film surface at a 45 degree angle from the perpendicular. using the same procedure and test angle.160 1550 .005 .12 .5 18.2 .08 . You may divide by the gauge (in mil) in order to approximate OTR at a different thickness.6200 LDPE (low density polyethylene) 450 . A sensor measures the amount of light reflected by the film at a mirror image angle.8500 7. Gloss: Gloss is a measurement of the relative luster or shininess of a film surface.3100 HDPE (high density polyethylene) 150 .200 2300 .2. The gloss value is the ratio of this reflected light to incident light and is reported in gloss units. Although rare.Film Type OTR @ 73°F (23°C). They can be valuable appearance attributes for packages.9 Biax Nylon-6 1.2500 Cast PP 150 . Day-to-day process variations will have an insignificant effect on gloss.1. this can lead to gloss values that exceed 100. labels. In particular. Theoretically. What affects film gloss Gloss is primarily determined by material selection and surface smoothness. Transparent films have two reflecting surfaces.39 OPET (oriented polyester) 2-6 31 . or graphic arts items. Optical test -gloss -opacity -haze -light transmission -optical density a. brilliance. EVOH* (ethylene vinyl alcohol) . Shininess. the range of the gloss scale is 0 to 100. and sparkle are properties related to a film's gloss value. Precise comparisons of gloss values can only be made when the measurements are performed on samples of the same general type of material. 0% RH (cc/100 in2/24 hr) (cc/m2/24 hr) The following OTRs are bulk material properties displayed at 1 mil. .3100 OPS (oriented polystyrene) 280 ..500 7000 . which are defined during product and process development.400 4350 .93 OPP 100 .6 . . and ExxonMobil uses the one called "89% reflectance backing. opacity values for OPPalyte films range from 60% to 95%. The simplified diagram in Figure 2 graphically summarizes the test. Because white opaque films are replacing paper in some applications. Relevance to performance Originally developed for paper." This value is equal to 100 times the ratio of the diffuse reflectance of a film sample backed by a black body (<. most notably labels.5% reflectance) to the diffuse reflectance of the same sample backed by a white body (89% reflectance)." also called "contrast ratio. It is primarily used as a property of paper and predicts the relative visibility on one side of the paper of the images that exist on the other side. because the print showing through from the other side is less noticeable. Higher opacity values allow better readability on one side. Now. The units are percent. Depending on the product design and film thickness. ExxonMobil measures opacity for some white films. and a perfectly opaque material will have an opacity value of 100%.Test principles ExxonMobil uses commercially available gloss meters to measure 45-deg gloss consistent with ASTM procedure D 2457. Opacity Definition Opacity represents a substrate's light blocking ability. this property predicts the appearance of two-side printed paper. the same test used for paper is being applied to opaque polymer films that compete in paper markets. Figure 2: Gloss measurement b. There are two common types of opacity measurements. light transmission. Relevance to performance Transmission densitometers are traditionally used to evaluate the light transmission properties of photographic film. The same test is now used to also represent the thickness of the aluminum layer of vacuum-metallized films. is determined mostly by pigment and cavitation characteristics. which is equivalent to light transmission values of 0. This value will be higher than R 0 (or equal to it. which ExxonMobil measures with a transmission densitometer. Depending on the product design.89) CO.89 is the contrast ratio. and it enhances the data resolution for materials that transmit only a small fraction of incident light.1% to 1. c. ExxonMobil uses optical density measurements with metallized films only. which are controlled by proprietary resin formulations and film-making process conditions.5% reflectance or less.89 is the reflectance of the substrate when it is backed by a white body having a reflectance of 89%. Test principles Although opacity has to do with light-blocking ability. R0. with descriptions of the variables follows.89 = 100 (R0 + RO.What affects the opacity of OPPalyte films Opacity. ExxonMobil metallized films have optical density values ranging from 2. . like light transmission.0. Since layer thickness affects important performance-related properties like film barrier.0 to 3. Opacity (89% reflectance backing) = CO. The optical density scale is unitless and logarithmic. the test actually measures two reflectance values. which is another name for this type of opacity measurement. The equation. Optical density Definition Optical density. Any light that passes through a partially opaque sheet will reflect back negligibly. such as calcium carbonate (CaCO 3) and titanium dioxide (TiO2). is a representation of a material's light blocking ability. optical density provides critical data for process control of the metallizing process.0%. The ratio of these values times 100 is equal to percent opacity. if the sample is perfectly opaque) because any light that passes through the substrate will largely be reflected. and appearance. ExxonMobil technology creates high opacity levels with a minimum use of inorganic fillers. and a portion of that will transmit through the film a second time (in the opposite direction). R0 is the reflectance of the substrate when it is backed by a black body of 0. Compared to other flexible plastic films. can further affect haze.5° (degrees) from the direction of the incoming beam. What determines the haze level of a clear film Haze is greatly influenced by material selections and product design.What affects the optical density of metallized films Metallizing process parameters and base film characteristics control the aluminum layer thickness and uniformity. Additional variables. Test principles . The light that is transmitted through the film is collected. Test principles ExxonMobil data are provided by commercial densitometers that meet standard conditions defined by ANSI. such as crystallinity and molecular weight distribution. perpendicular light beam is directed onto the film sample. Optical Density (unitless) = log10( Incident light Transmitted light ) = log10( 100 Light transmission (%) ) Optical density values are reported to two decimal places. measured. More technically. the optical density. Resin characteristics. d. Additives and coatings usually contribute to increased haze. It tends to symbolize quality and contributes to the positive visual display of the product. This property is used to describe transparent and translucent films. Haze Definition Haze is the scattering of light by a film that results in a cloudy appearance or poorer clarity of objects when viewed through the film. Copolymers are generally hazier than homopolymers. clear OPP has one of the lowest haze values. and logarithmically amplified. so they are tightly controlled. not opaque films. like process temperatures in the different stages of film-making. Relevance to performance Film clarity is a highly desirable feature for most clear packaging and label applications. The densitometer calculates and displays the optical density value. A unidirectional. All other things being equal. and therefore. haze is the percentage of light transmitted through a film that is deflected more than 2. thicker films will be hazier than thinner films. generally less than 3%. ExxonMobil uses the Tobias TBX transmission densitometer and Macbeth models TD903 and TD932. have a key impact. The optical density values represent the following calculation and relationship to % light transmission. e. Relevance to performance This property is significant to the performance of opaque films like OPPalyte. OPPalyte film light transmission values range from 15% to 50%. a unidirectional light beam is directed onto the film specimen. After it enters an integrating sphere. but the preferred test for . provided it meets the procedure requirements.5°. Figure 1: Haze measurement Commercial hazemeters are typically used for this testing. The hazemeter may also be set up to measure and display light transmission.5°. ExxonMobil generally evaluates this property for OPPalyte films. ExxonMobii uses the SKY-Gardner XL-211 Haze-gard and Haze-gard plus hazemeters consistent with ASTM guidelines. Customers expect these products to obstruct light transmission in a predictable way. NOTE: Metallized films are very effective at blocking light transmission. Haze is the percentage of total transmitted light that is scattered by more than 2. depending on the product design and film thickness.As represented in Figure 1. Light transmission Definition Light transmission is the percentage of incident light that passes through a film. which is important for the appearance of printed graphics and protecting light-sensitive packaged products. but ASTM D 1003 also allows the use of a spectrophotometer. a photo detector measures the total light transmitted by the film and the amount of transmitted light that is scattered more than 2. Handling properties . boards and films. Tester has a means of measuring difference between potential energy of pendulum at maximum height in free swing . Since light transmission is usually a critical property for white opaque films. It also includes the following.Crimp test . Elongation impact test Impact Strength The pendulum impact tester can be used to measure impact strength of papers. An impacting head on the end of a pendulum is swung through an arc into and through sample. Product will be rejected if values are outside the specified tolerance limits. ExxonMobil uses the BYKGardner XL-211 haze-gard and haze-gard plus hazemeters consistent with ASTM guidelines.Efficiency . require less cutting force and power. 8. What affects light transmission In OPPalyte films. The hazemeter when set up to measure light transmission will display the final result as a percentage to the nearest tenth. Test principles A unidirectional perpendicular light beam is directed onto the film specimen. . it is measured regularly. but ASTM D 1003 also allows for the use of a spectrophotometer. Material with a lower machinability causes less tool wear.Sealibility etc 9. Machinability test Machinability refers to the ease of which packaging material may be used in manufacturing and packaging operations.Slip properties/frictional properties .these films is optical density. Light Transmission (%) = Total light transmitted by specimen Incident light x 100 The same test equipment with a different setup is also used to measure and display haze. and a photo detector measures the total light transmitted by the specimen after it enters an integrating sphere. provide a better surface finish and better chip disposal. light transmission is determined mostly by pigment and cavitation characteristics. provided that it meets the procedure requirements.Convenience function . Commercial hazemeters are typically used for this testing. which are controlled by proprietary resin formulations and film-making process conditions.Printability . It is useful in predicting resistance of a material to breakage from dropping or other quick blows. Significance and purpose are the same as in the pendulum test.Burst Strength/Bursting strength test It is the ability of a material to resist rupture by pressure This test is also known as Muller test. A test similar in scope. The instrument may use hydraulic or pneumatic pressure. The pressure (psig or kg/cm2) at which the specimen ruptures is noted. This test is used as a control test in the paper mill. 10. The specimen is fixed in the testing equipment and the pressure (pneumatic or hydraulic) is applied. This difference in energy is defined as impact strength and is reported in units of kilogram-centimeters. Fig: horizontal impact test These tests give an index of material's dynamic strength and approximate what will occur when package is dropped. The bursting strength test gives an indication of tensile strength and stretch of paper. The bursting strength is largely accepted as a specification for boards used in container construction and also for all types of papers. Dart unit is weight of dart in grams that breaks sample 50% of the time. Weighted dart is dropped from standard height onto taut sample. . method and significance is the dart drop test.and potential energy of the pendulum after rupture of sample.