Plastics Testing Method

Plastics Testing Method:

Metal: A Material is that out of which anything is or may be made. A material relates itself to matter. Materials comprise a wide range of metals which must be operated upon to form the finished product. Extractive metallurgy is usually subdivided into two categories.

Ferrous: Ferrous metallurgy is concerned with iron and steel and the alloy of iron and steel.

Non-ferrous: Non-ferrous metallurgy encompasses all metal and alloy with the exception of the iron and steel and their alloy.

Ceramics: Ceramics usually consist of oxides, nitrides, carbides, silicates or borides of various metals. Ceramics are any inorganic, non-metallic solids processed or used at high temperature. Ceramic material contains compounds of metallic and non-metallic element, such as MgO, SiO2, SiC, BaTiO3, glasses, etc. Brittleness, Resistance to high temperatures, Hardness, Rock-like appearances, Abrasiveness, Insulation (to flow of electric current), Corrosion resistance, Opaque to light, High temperature strength . 

Example of Ceramic material is: Sand, Refractoriness, Glass, Boron nitride, Brick, Cement, Concetete, Insulators, Silicon carbide, Plaster, Abrasives

Organic materials: They are polymeric materials of carbon compounds. Polymers are solid composed of long molecular chains. There are countless organic materials, natural, synthetic or manufactured and based chemically on carbon. Important material of organic materials: Rubber, Fuels, Paper, Lubricants, Wood, Paints and finishes, Textiles, Explosives, Adhesives, plastics.

HUE: Simply put, hue is just another word for color. Bright yellow is a hue, and so is gray. One aspect of hue or color is that each has a visual temperature - warm or cool.

Testing: Testing yield basic information about a plastic its properties relative to quality in reference to a standard.

Specification and standard: A standard is a detailed, formally ratified and fixed technology, format or method which enables the performance of a particular task or activity. A specification can be considered to be a ‘draft standard’, in that it is a step on the path towards formal standardisation, but can be incomplete and is inherently subject to change and development. Conformance to a specification allows a degree of standardisation in advance of the development and formal ratification of a standard; input in the specification development process by commercial organisations can help ensure the longevity of resources produced in conformance with these specifications.

International standard organisation (ISO): standards are developed according to strict rules to ensure that they are transparent and fair. The reverse side of the coin is that it can take time to develop consensus among the interested parties and for the resulting agreement to go through the public review process in the ISO member countries. For some users of standards, particularly those working in fast-changing technology sectors, it may be more important to agree on a technical specification and publish it quickly, before going through the various checks and balances needed to win the status of a full International Standard. Therefore, to meet such needs, ISO has developed a new range of "deliverables", or different categories of specifications, allowing publication at an intermediate stage of development before full consensus: Publicly Available Specification (PAS), Technical Specification (TS), Technical Report (TR), and International Workshop Agreement (IWA).

Mechanical Properties: The properties of materials when subjected to stresses and strains are called “mechanical properties”. In other words the properties that determine the behavior of engineering mats under applied forces are called “mechanical properties”. Among all the properties of plastic material are aften the most important properties. Packing of polymer molecules into crystalline lattice generally restricts their mobility and stiffness their reversible mechanical properties. Elongation in polymer that is near or above the glass transition temperature generally decreases as crystallinity increases. Creep and compliance creep of polymer, above the glass transition temperature, are greatly reduced by crystallinity.  Crystallinity often decreases impact strength and large crystallites particularly produce brittleness as explained below. the material rection for a variety of application is after.

Elasticity: A liquid or gas adapts itself to the shape of its container, but a solid has a shape of its own, which it tends to preserve. This tendency of a deformed solid to seek its original dimensions upon unloading is ascribed to a property called Elasticity. The recovery from the distorting effects of the loads may be instantaneous or gradual, complete or partial. A solid is called perfectly elastic. Concepts of Strain, Stress, and Modulus of Elasticity.

                           Load (P)                         Change in length ( /\l)

       Stress=   ----------------         , Strain= ------------------------------

                           Area (A)                          Original length (l) 

Plasticity: Plasticity is that property of a material by virtue of which it may be permanently deformed when it has been subjected to an externally applied force great enough to exceed the elastic limit. The minimum stress that should cause permanent deformation can be computed from knowledge of the Bond strength. Crystalline materials undergo plastic deformation as the result of slip along definite crystallographic planes whereas, in amorphous materials, plastic deformation occurs when individual molecules or groups of molecules slide past one another. 

Stress–strain curve: If a load applied to the material is static or changing slowly with time and it is applied uniformly on the surface of interest, then we can test the behavior of the material under applied load by a test called “stress-strain” test. During tensile testing of a material sample, the stress–strain curve is a graphical representation of the relationship between stress, derived from measuring the load applied on the sample, and strain, derived from measuring the deformation of the sample, i.e. elongation, compression, or distortion.

The slope of stress-strain curve at any point is called the tangent modulus; the slope of the elastic (linear) portion of the curve is a property used to characterize materials and is known as the Young's modulus. The area under the elastic portion of the curve is known as the modulus of resilience. The nature of the curve varies from material to material. The following diagrams illustrate the stress–strain behaviour of typical materials in terms of the engineering stress and engineering strain where the stress and strain are calculated based on the original dimensions of the sample and not the instantaneous values.

Tension test: The load and deformation relationship depends on the geometrical factors of the specimen; therefore, normalization of them to geometric dimensions are helpful in comparing the materials.

Compression test: is not very common. It is usually used if the material application consists of compressive force system or if the material is brittle under tensile force. Compressive force is negative by convention yielding negative stress and strain.

Yielding and yield strength: Most structures are designed to ensure that only elastic deformation will result when a stress is applied.

Therefore it is useful to know the stress level at which plastic deformation begins or where the yielding occurs. If the transition from elastic to plastic behavior is gradual, the point of yielding may be determined as the initial departure from linearity (P=proportional limit). In cases where it is difficult to determine this point (P point) precisely, a conventional approach is used. A straight line is constructed parallel to the elastic deformation line at a strain offset usually 0.002. The stress correspoding to this point is yield strength ((y). For the materials having nonlinear elastic region, yield strength is defined as the stress required to produce some amount of strain ((=0.005).

Tensile strength: ASTMD-638, BS-2782, ISO-527 Injection moulded specimen will have high value than the compression specimen. A load applie paralled to the direction of molecular orientation may have higher value. As the temperature incress the tensile strength decress. Tensile strength may vary between 50 MPa to as high as 3000 Mpa. M is the stress at the maximum point of the stress-strain curve. F is the fracture point. 

Impect strength: ASTMD-256, The most uridely used test for impect strength is the holched izodunpact swung from cestoun heigh is made to impect on a holched contilevered specimen.

The test can also be with the notch reserved in which case it is reversed impect strength respectively. Specimen size = 63.5x 12.7x 3.2mm.

Charpy impect strength: ASTND-6110 it is less commonus but is widly used in Europ. The test identical to izod test eccept that inpacted midlong b/w the supports. Speciman size = 12.7x 6.4x 127.00mm

Abrasion resistance: ASTMD-1044, ISO-9353 speciman sie = 110mm dia with 3mm thickness, Abrosulon resistance is the abibility to with stand the progressive remoral of material from it’s surface as result of mechanical action of rubbing, scrapping as essoion. Most test an abrasos out at least 5000 reralution. Test result are reposted as weight less in mg/1000 eycles.

Yield strength: The stress a material can withstand without permanent deformation. This is not a sharply defined point. Yield strength is the stress which will cause a permanent deformation of 0.2% of the original dimension.

Ultimate strength: The maximum stress a material can withstand.

Breaking strength: The stress coordinate on the stress-strain curve at the point of rupture.

Ductility: It is a measure of the degree of plastic deformation that has been sustained at fracture. A material that experiences very little or no plastic deformation upon fracture is termed brittle. Ductility of materials is important for at least two reasons: (i) it indicates the degree to which a structure will deform plastically, (ii) it specifies the degree of allowable deformation during fabrication. Fracture strain of brittle materials is about 5%. 

Resilience: is the capacity of a material to absorb energy when it is deformed elastically and then upon unloading to have this energy recovered.Modulus of resilience (Ur) = strain energy per unit volume required to stress a material from an unloaded state up to the point of yielding.

Tlexural strength: ASTMD-790, ISO-178, JIN-53452, ∆S-2782, ∆HS-K-7203 Tlecural strength is the abolity of the material strength to bending forces applied perpendicular to its longitudinal axis the stress eiduced due to flecural load are a comlainaton of coupresure and tensile strength specimen size 3.2x 12.7x 1270mm.

Toughness: is a mechanical term. It is a measure of the ability of a material to absorb energy up to fracture. For dynamic loading conditions and when a notch is present, notch toughness is assessed. Fracture toughness is material’s resistance to fracture when a crack is present. For low strain rate situation, the area under (-( curve up to the point of fracture corresponds to toughness. For a material to be tough, it must display both strength and ductility and often ductile materials are tougher than brittle ones.

Hardness: is a measure of a material’s resistance to localized plastic deformation.Measured hardnesses are relative (not absolute). Hardness tests are; simple and inexpensive, test is nondestructive, other mechanical properties can be estimated from hardness data.

Rockwell Hardness tests: (ASTM standard E 18)Several different scales can be used from possible combinations of various indenters and different loads.Indenters: spherical and hardened steel balls (1/16, 1/8, ¼, ½ in. diameter) and a conical diamond (Brale) intender.

Hardness number is determined by the difference in depth of penetration resulting from the application of an initial minor load followed by a larger load, On the basis of minor and major loads there are two tests: Rockwell and superficial Rockwell tests. 

Knoop and Vickers test: A very small diamond indenter having pyramidal geometry is forced into the surface of the specimen. Applied loads=1-1000 g. the impression is analyzed by microscope and measured.

The measurement is then converted to hardness number.

Creep: The phenomenon under deformation with time. Graph ::OP-constant  PQ-primary creep  QR-constant creep RS-fracture.

Brinell hardness tests: The diameter of the hardened steel or tungsten carbide indenter is 10 mm. Applied Loads= 500-3000 kg.The diameter of resulting indentation on the surface is measured using a special low power microscope. the measurement is converted to hardness number. 

Impact Strength: The ability of a material to absorb mechanical energy in the process of deformation and fracture under impact loading. The term “impact strength, ” as well as the term “impact energy, ” is also applied to the amount of energy absorbed before fracture.To determine impact strength, a bending impact test is commonly used. The specimen in this case has a prismatic bar shape, and a transverse notch is cut in one side of the specimen. The impact strength is regarded as the work required for the fracture of the specimen. In the USSR the work is generally referred to the cross-sectional area of the specimen at the base of the notch and is expressed in joules per square meter, newton-meters per square meter, or kilogram-force-meters per square centimeter.Impact strength is one of the most important strength characteristics of a metal. When the test temperature is lowered over a series of tests, a sharp drop in impact strength indicates the brittle temperature of the material. Reliable performance of the material is possible only at temperatures above the brittle temperature. In another type of bending impact test that is sometimes used, a small fatigue crack is produced in advance at the base of the notch; the crack is 1.5 mm in length. In this case a measurement is made of the specific work required for fracture of the specimen. Compared with the impact strength as measured in the first type of test described, the impact strength measured in this way provides a more sensitive characterization of the brittleness of high-strength materials.

Thermal properties: Thermal properties of plastic material are equally as important us the mechanical properties. The test delta of thermal properties of plastic are much useful for the design engineers to reject a suitable material at which enrolment the finally product is to be subjected.

Heat deflection temperature: is determined by the following test procedure outlined in ASTM D-648. The test specimen is loaded in three-point bending in the edgewise direction. The outer fiber stress used for testing is either 0.455 MPa or 1.82 MPa, and the temperature is increased at 2 °C/min until the specimen deflects 0.25 mm. This is similar to the test procedure defined in the ISO Limitations that are associated with the determination of the HDT is that the sample is not thermally isotropic and, thick samples in particular, will contain a temperature gradient. The HDT of a particular material can also be very sensitive to stress experienced by the component which is dependent on the component’s dimensions. The selected deflection of 0.25 mm (which is 0.2% additional strain) is selected arbitrarily and has no physical meaning. Heat distortion temperature (HDT, HDTUL, or DTUL) is the temperature at which a polymer or plastic sample deforms under a specified load. This property of a given plastic material is applied in many aspects of product design, engineering, and manufacture of products using thermoplastic components.

Vicat softening point: or Vicat hardness ASTMD-1525, ISO-306, specimen size =10x 10x 3mm  is the determination of the softening point for materials that have no definite melting point, such as plastics. It is taken as the temperature at which the specimen is penetrated to a depth of 1 mm by a flat-ended needle with a 1 square mm circular or square cross-section.

For the Vicat A test, a load of 10 N is used. For the Vicat B test, the load is 50 N. Standards to determine Vicat softening point include ASTM D 1525 and ISO 306, which are largely equivalent.

Surface Resistance: ASTMD-257, ISO- 3915, Specimen size = 110mm dia with 3mm thickness. Is yhe ralve to the direct voltage applied to the electrodes  to the portin of the arrent b/w then which is primarily in min layers of moisture or other semi-conducting material that many be deposited on the surface. The volume resistance is defend as the rate of direct voltage applied to two electrodes that are in connect with a specimen to the position of the current B/w then is disturbed through the volume of the specimen. The electrical resistance between two electrodes in contact with a material surface is the ratio of the voltage applied to the electrodes to that portion of the current between them which flows through me surface layers. 

Volume Resistance: The volume resistance is defend as the rate of direct voltage applied to two electrodes that are in connect with a specimen to the positives of the current B/w then that is disturbed through the volume of the specimen. The electrical resistance between opposite faces of a 1-cm cube of insulating material, expressed in ohm-centimetres. 

Dielectric strength: ASTMD-1009, ISO-132, Specimen size = 50mm or dia 3mm, when an issulator is subjected to increases high voltage it event wall breaks down and allows a current just before it breaks down dour de by the thickness of the sample is know as dielectrul strength of the material measured in voltmeter.

Arc Resistance: ASTMD- 1195, The ability of a material to resist the action of a high voltage electrical arc, usually stated in terms of the time required to render the material electrically conductive. Failure of the specimen may be caused by heating to incandescence, burning, tracking or carbonization of the surface. Breakdown between two electrodes usually occurs as a conducting path is burned on the surface of the dielectric material. 

Dielectric: (ASTMD-150, specimen size 50mm, dia 30mm thickness.) is an electrical insulator that can be polarized by an applied electric field. Dielectrics are things that do not conduct electricity well, if at all. Dry air is a great example of a dielectric. A wall is another. Materials have different dialectics constants at room temperature. For example, air is about 1, paper is 3, and rubber is 7. The dielectric constant is the ratio of the electrical conductivity of a dielectric material to free space. Tools like an electronic stud sensor uses the property of dielectric constants to measure the relative density of a wall and identify when that density changes, as when the sensor passes over a wood stud. When a dielectric is placed in an electric field, electric charges do not flow through the material, as in a conductor, but only slightly shift from their average equilibrium positions causing dielectric polarization. Because of dielectric polarization, positive charges are displaced toward the field and negative charges shift in the opposite direction. This creates an internal electric field which reduces the overall field within the dielectric itself. If a dielectric is composed of weakly bonded molecules, those molecules not only become polarized, but also reorient so that their symmetry axis aligns to the field.

Dissipation factor: (DF) is a measure of loss-rate of energy of a mode of oscillation (mechanical, electrical, or electromechanical) in a dissipative system. It is the reciprocal of Quality factor, which represents the quality of oscillation. For example, electrical potential energy is dissipated in all dielectric materials, usually in the form of heat. In a capacitor made of a dielectric placed between conductors, the typical lumped element model includes a lossless ideal capacitor in series with a resistor termed the equivalent series resistance (ESR) as shown below.  The ESR represents losses in the capacitor. In a good capacitor the ESR is very small, and in a poor capacitor the ESR is large. Note that the ESR is not simply the resistance that would be measured across a capacitor by an ohmmeter. The ESR is a derived quantity with physical origins in both the dielectric's conduction electrons and dipole relaxation phenomena. In a dielectric only one of either the conduction electrons or the dipole relaxation typically dominates loss. For the case of the conduction electrons being the dominant loss.

Comparative Tracking Index or CTI: is used to measure the electrical breakdown (tracking) properties of an insulating material. To measure the tracking, 52 drops of 0.1% ammonium chloride solution are dropped on the material, and the voltage measured for a 3mm thickness is considered representative of the material performance. Also term PTI (Proof Tracking Index) is used: it means voltage at which during testing on five samples the samples pass the test with no failures. Tracking is an electrical breakdown on the surface of an insulating material. A large voltage difference gradually creates a conductive leakage path across the surface of the material by forming a carbonized track. Testing method is specified in IEC standard 60112. Performance Level Categories (PLC) were introduced to avoid excessive implied precision and bias. The CTI value is used for electrical safety assessment of electrical apparatus, as for instance carried out by Underwriters Laboratory. The minimum required creep age distances over an insulating material between electrically conducting parts in apparatus, especially between parts with a high voltage and parts that can be touched by human users, is dependent on the insulators CTI value. Also for internal distances in an apparatus by maintaining CTI based distances, the risk of fire is reduced.

Optical Clarity: ASTMD-1746, Specimen 75x75mm, Due to its excellent clarity and purity combined with its outstanding toughness, Makrolon® can fulfill most needs in applications requiring high transparency.

Haze and luminous transmittance: Haze and Luminous Transmittance of transparent plastics. In this test, haze of a specimen is defined as the percentage of transmitted light which, in passing through the specimen, deviates more than 2.5° from the incident beam by forward scattering. Luminous transmittance is defined as the ratio of transmitted to incident light. These qualities are considered in most applications for transparent plastics. They form a basis for directly comparing the transparency of various grades and types of plastics. A haze meter and/or a recording spectrophotometer are used in the test. ASTMD-1003.

Kinematic Viscosity: The absolute (dynamic) viscosity of a fluid divided by the density of the fluid. The ratio of the kinematic viscosity of a specified solution of the polymer to the kinematic viscosity of the pure solvent.

Die swell: also known as extrudate swell, is a common phenomenon in polymer processing. Die swell occurs in instances of polymer extrusion, in which a stream of polymeric material is forced through a die, a specialized tool in manufacturing to shape or cut polymeric materials. Die swell is an instance where a polymer stream is compressed by entrance into a die, and is followed by a partial recovery or “swell” back to the former shape and volume of the polymer after exiting the die, hence the term die swell.

Dgnamie viscosity: The resistance to flow encountered when one layer or plane of fluid attempts to move over another identical layer or plane of fluid at a given speed. Dynamic viscosity is also called absolute viscosity. Learn more about dynamic viscosity in the class "Hydraulic Fluid Selection 320" below.

Electrical Properties: Crystallinity restricts the mobility of polar groups in the polymer molecules and thus affects dielectric properties of the polymer.  In the molten state thermal randomization of polar groups is greater than orienting effects of an electric field and dielectric constant rather low. With decreasing the temperature thermal randomization decreases, the orienting and polarization effects of the electric field remains and thus dielectric constant increases. 

Water absorption: The amount of water absorbed by a composite material when immersed in water for a stipulated period of time. (2) The ratio of the weight of water absorbed by a material, to the weight of the dry materials. All organic polymeric materials will absorb moisture to some extent resulting in swelling, dissolving, leaching, plasticizing and/or hydrolyzing, events which can result in discoloration, embrittlement, loss of mechanical and electrical properties, lower resistance to heat and weathering and stress cracking. Adsorption is the adhesion of atoms, ions, bio molecules or molecules of gas, liquid, or dissolved solids to a surface. This process creates a film of the adsorbate (the molecules or atoms being accumulated) on the surface of the adsorbent. It differs from absorption, in which a fluid permeatesor is dissolved by a liquid or solid. The term sorption encompasses both processes, while desorption is the reverse of adsorption. It is a surface phenomenon.

Water Solubility (SW) - "The solubility of a chemical in water may be defined as the maximum amount of the chemical that will dissolve in pure water at a specified temperature. Above this concentration, two phases will exist if the organic chemical is a solid or a liquid at the system temperature: a saturated aqueous solution and a solid or liquid organic phase. Aqueous concentrations are usually stated in terms of weight per weight (ppm, ppb, g/kg, etc.) or weight per volume (mg/L, moles/L, etc.)." Solubility is the property of a solid, liquid, or gaseous chemical substance called solute to dissolve in a solid, liquid, or gaseous solvent to form a homogeneous solution of the solute in the solvent. The solubility of a substance fundamentally depends on the used solvent as well as on temperature and pressure. 

Environmental Stress Cracking: (ESC)ASTMD-1693, is one of the most common causes of unexpected brittlefailure of thermoplastic (especially amorphous) polymers known at present.

Environmental stress cracking may account for around 15-30% of all plastic component failures in service. ESC and polymer resistance to ESC (ESCR) have been studied for several decades. Research shows that the exposure of polymers to liquid chemicals tends to accelerate the crazing process, initiating crazes at stresses that are much lower than the stress causing crazing in air. The action of either a tensile stress or a corrosive liquid alone would not be enough to cause failure, but in ESC the initiation and growth of a crack is caused by the combined action of the stress and a corrosive environmental liquid. It is somewhat different from polymer degradation in that stress cracking does not break polymer bonds. Instead, it breaks the secondary linkages between polymers. These are broken when the mechanical stresses cause minute cracks in the polymer and they propagate rapidly under the harsh environmental conditions. It has also been seen that catastrophic failure under stress can occur due to the attack of a reagent that would not attack the polymer in an unstressed state. Metallurgists typically use the term Stress corrosion cracking or Environmental stress fracture to describe this type of failure in metals.

Reagent: is a "substance or compound that is added to a system in order to bring about a chemical reaction, or added to see if a reaction occurs.  Although the terms reactant and reagent are often used interchangeably, a reactant is less specifically a "substance that is consumed in the course of a chemical reaction". Solvents and catalysts, although they are involved in the reaction, are usually not referred to as reactants. In organic chemistry, reagents are compounds or mixtures, usually composed of inorganic or small organic molecules that are used to affect a transformation on an organic substrate. Examples of organic reagents include the Collins reagent, Fenton's reagent, and Grignard reagent. There are alsoanalytical reagents which are used to confirm the presence of another substance. Examples of these are Fehling's reagent, Millon's reagent and Tollens' reagent.

Gas permeability: The most important task during development of new packaging materials for food is therefore to minimise oxygen permeability. The permeation is affected in a complex way by a number of parameters within the material, like the flexibility of the polymer chains, morphology including orientation effects, crystallinity and interaction between the permeant molecules and the polymer, and interaction with an eventual filler. Also the relative humidity has a great influence on certain materials like EVOH. The expression ”permeation” aims at the whole transport process which simply put is a result of sorption (or condensation), diffusion and desorption (or evaporation), see figure below.

Water Vapour Transmission Rate: (WVTR) ASTME-96, ASTMD-1653, ISO-1663 measures the ability to transport moisture through a material of specified thickness. WVTR is measured in grams per square meter (g/m2 ) over a 24 hours period according to the US standard ASTM – E398 . The Bio Bag material used for the ventilated kitchen caddies and other applications related to food waste collection has a WVTR larger than 950 g/m2 for a film thickness of 30 micron. In comparison polyethylene has a WVTR of approximately 20 g/m2. Thinner materials will have higher WVTR.

Volatile loss: ASTMD-1203, The test methods are intended to be rapid empirical tests which have been found to be useful in the relative comparison of materials having the same nominal thickness. When the plastic material contains plasticizer, loss from the plastic is assumed to be primarily plasticizer. The effect of moisture is considered to be negligible. Correlation with ultimate application for various plastic materials shall be determined by the user. To obtain accelerated tests that more nearly approach actual service conditions, refer to Specification .

Loss on Ignition: ASTMD-2584, is a test used in inorganic analytical chemistry, particularly in the analysis of minerals. It consists of strongly heating ("igniting") a sample of the material at a specified temperature, allowing volatile substances to escape, until its mass ceases to change. This may be done in air, or in some other reactive or inert atmosphere. The simple test typically consists of placing a few grams of the material in a tarred, pre-ignited crucible and determining its mass, placing it in a temperature-controlled furnace for a set time, cooling it in a controlled (e.g. water-free, CO2-free) atmosphere, and redetermining the mass. The process may be repeated to show that mass-change is complete. A variant of the test in which mass-change is continually monitored as temperature is changed, is thermogravimetry.

Heat treating: ASTMD-3045, ASTMC-1246, is a group of industrial and metalworking processes used to alter the physical, and sometimes chemical, properties of a material. The most common application is metallurgical. Heat treatments are also used in the manufacture of many other materials, such as glass. Heat treatment involves the use of heating or chilling, normally to extreme temperatures, to achieve a desired result such as hardening or softening of a material. Heat treatment techniques include annealing, case hardening, precipitation strengthening, tempering and quenching. It is noteworthy that while the term heat treatment applies only to processes where the heating and cooling are done for the specific purpose of altering properties intentionally, heating and cooling often occur incidentally during other manufacturing processes such as hot forming or welding.

Weathering Testing: Sunlight, heat and moisture can cause serious product deterioration–such as fading, color change, cracking, peeling, oxidation or loss of strength.  Damage from weathering or corrosion occurs both outdoors and indoors, and its severity can vary greatly in different climates. Even materials that are resistant to sunlight alone or to moisture alone often fail when exposed to sunlight and moisture in combination. CRT Labs now offers weathering testing using the latest Q-Lab weatherability testing equipment. Whether your need is to test the damaging wavelengths of light encountered either indoors or outdoors, or weathering testing related to moisture exposure, CRT Labs has a solution.

Biological and microbiological attack: ASTMD-5209, were conducted to determine the susceptibility of the products of biodegradation. Biodegrading process starts when the plastic material comes in the contact with screw age with sewage sludge or compost where the naturally occurring microorganisms such as bacteria, fungi and algae start their action to degrade the materials. Primary bio-degradability is the alteration in chemical structure of the material and loss of specific properties.

Optical Properties: Crystallinity increases the density of the polymer, which decreases the speed of light passing through it and thus increases the refractive index. When crystals are larger than the wavelength of visible light about 400-700mµ lights passes through much successive crystalline and amorphous area is scattered and clarity of the polymer decreased. Large single crystal scatters light at wide angels and thus causes haze. 

Chemical Properties: The tigtly packed regular structure of crystalline polymers is so stable that it is impossible to break the lattice using chemicals, Liner amorphous polymers dissolve easily in a range of organic solvents, Crystalline polymers are usually insoluble and can be dissolved only under limited condition in few specific solvents,  Crystalline polymers can be dissolve above their melting point where sufficient thermal energy has already been supplied to separate the polymer molecules from the tight crystalline structure.

Physical Properties: 

1.) Dimension: Dimension of a material implies its size (i.e. length, bright, height.) and shape (i.e. square, circular, angle, channel).

2.) Appearance: Different materials have different looks. A metal looks clearly distinct from wood or plastic. Even metals themselves have got different appearance e.g. Aluminum is a silvery white metal whereas copper appears brownish red. Appearance includes luster, color and finish (e.g., line marks on the surface.) of a material.

3.) Luster: Luster is the ability of material to reflect when finely polished. It is the brightness of a surface. A metal can be classified from a non-metal on the basic of luster. Wrought iron has got red scaly appearance. Cast iron shows sandy facture. Mild steel has smooth finish with bluish black sheen.

4.) Color: Color is that aspect of appearance of a material that depends on the spectral composition of the light reaching the retina of the eye, and on the light’s temporal and spatial distribution. The colors of a material depend upon the wavelength of the light that the material can absorb. The color of the material is very helpful in identification of a metal.

5.) Density: The density is the weight of unit volume of a material expressed in the metric units; its value for metals can be calculated from the following relation-

                  n A

Density=---------- (for cubic lattices.) 

                 a3 N

n=number of atom per unit cell,

A=weight of a gram-atom

a=lattice parameter 

N=number of atoms per gram-atom..

6.) Melting point: One metal can be distinguished from the other on the basic of its melting point. Melting point of a metal is that temperature at which the solid metals changes into the molten state. Melting point of the materials is related to the bonding forces in solid. Materials having strong bonds tend to have higher melting points. Thus, materials having covalent, ionic, metallic and molecular bond having points in decreasing order. For example, diamond, having perfect covalent bond possesses highest melting point. Melting point of mild steel, copper and aluminum are about 1500, 1080, and 650*C respectively. 

7.) Porosity: A material is said to be porous if it has pores within it. Pores absorb lubricant as a sintered self-lubricant bearing.

                               Total pore volume 

True porosity=------------------------------------------

                               Bulk (total) volume 

8.) Structure:  Structure means geometric relationship of material components. Structure also implies the arrangement of the internal components of matter-

1.) Electron structure.

2.) Micro structure.