Polymers and Plastics

In contemporary manufacturing, plastics and polymers are fundamental materials used extensively in automotive structural components, medical device housings, pharmaceutical packaging, electrical insulation, optical instrumentation, and aerospace assemblies. While these materials offer significant versatility, they are also susceptible to diverse failure modes.

Material failures – such as thermal softening during operation, impact-induced fracture of enclosures, compromised oxygen barrier properties in films, dimensional instability due to moisture absorption in thermoplastics, or inconsistent hydroxyl content in polyol formulations – can be mitigated through rigorous standardised testing. Implementing such protocols ensures that material deficiencies are identified before production commitment.

The testing of polymers and plastics is a systematic discipline focused on acquiring mechanical, thermal, chemical, and physical property data. This quantitative information is essential for material selection, design validation, production qualification, and failure analysis. The following sections detail the primary ASTM methodologies employed by Infinita Lab’s network of accredited facilities to support various industrial applications.

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Tensile Testing for Plastics

Tensile properties  –  the strength, elongation, and modulus of a plastic under tensile loading  –  are the most fundamental characterisation data for any structural or semi-structural plastic material. They determine whether a material can carry the loads its application demands, whether it will deform elastically or yield permanently before breaking, and whether it meets the specification required for its intended use. A plastic with inadequate tensile strength fails structurally. One with insufficient elongation breaks brittlely when it should flex. One with an incorrect modulus deflects more or less than the design expects.

Relevant ASTM Standards:

ASTM D638 – Tensile Properties of Plastics. ASTM D638 measures various tensile properties, such as tensile strength, breaking strength, and maximum elongation, of reinforced and unreinforced plastics. The standard test samples are prepared as dumbbell-shaped specimens and tested under defined pretreatment conditions, including temperature, humidity, and testing machine speed. ASTM D638 is used to measure the force required to rupture a plastic sample and to determine the extent of the sample’s elongation to the breaking point. This test is one of the most widely specified in polymer material data sheets, procurement specifications, and product qualification programs across automotive, consumer goods, electrical, and industrial plastic applications.

Flexural Properties Testing

Many plastic components in structural applications are loaded in bending rather than pure tension  –  a snap-fit tab, a PCB substrate, a housing rib, a plastic bracket. For these applications, flexural strength and flexural modulus are the governing material properties, not tensile properties. A plastic that passes tensile testing may still fail a structural design requirement if its flexural stiffness is insufficient to resist the bending loads it will experience in service.

Relevant ASTM Standards:

ASTM D790 – Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials. ASTM D790 measures the flexural strength and flexural modulus of plastics and electrical insulating materials under three-point bending loads. Specimens are supported at two points and loaded at the midpoint until failure or a defined deflection is reached. Flexural data from ASTM D790 is used in the design and specification of rigid plastic components for consumer products, electrical enclosures, automotive interiors, structural panels, and any application where resistance to bending loads is a performance requirement.

Impact Resistance Testing

Impact resistance  –  the ability of a plastic to absorb energy and resist fracture when struck by a sudden load  –  is one of the most practically relevant mechanical properties for any plastic used in real-world applications. Drop events, tool impacts, installation loads, and in-service collisions are all impact events that a plastic housing, enclosure, or structural component may encounter. A plastic with high tensile strength can still be dangerously brittle if its impact resistance is inadequate, failing catastrophically under sudden loading that a tougher material would absorb.

Relevant ASTM Standards:

ASTM D256 – Izod Impact Resistance of Plastics ASTM D256 measures the energy required to break a notched plastic specimen under a swinging pendulum impact using the Izod configuration. The notch concentrates stress at a defined point, making the test sensitive to the material’s notch toughness. This property governs brittle fracture in service applications with stress concentrations. This test is a standard qualification requirement for plastic enclosures, tool housings, automotive components, toys, and any plastic part where impact survival under handling or service loading is a specification requirement.

ASTM D1709 – Impact Resistance of Plastic Film by the Free-Falling Dart Method ASTM D1709 determines the impact resistance of plastic films and thin sheeting using a free-falling dart dropped from a defined height onto a supported film specimen. This test is specifically designed for flexible film materials used in packaging, where the ability to resist puncture and tearing under impact loading determines whether the package protects its contents through the distribution chain. Results from ASTM D1709 are used in the qualification and quality control of polyethylene, polypropylene, and other packaging films.

Heat Deflection Temperature (HDT) Testing

Every thermoplastic has a temperature above which it begins to soften and lose its ability to carry structural loads  –  the heat deflection temperature. This is not the material’s melting point, but the more practically relevant threshold at which the material can no longer maintain its shape under a specified bending stress. Understanding the HDT of a plastic is essential for any application where the component will be exposed to elevated temperatures  –  whether from a hot-fill process, a dishwasher cycle, an automotive underhood environment, or proximity to electronic components that generate heat.

Relevant ASTM Standards:

ASTM D648 – Deflection Temperature of Plastics Under Flexural Load ASTM D648 determines the heat deflection temperature (HDT) of plastic materials by measuring the temperature at which a specimen deforms by a specified amount under a defined bending stress. The test is conducted at two standard stress levels  –  0.455 MPa and 1.82 MPa  –  providing data relevant to both lightly and heavily loaded applications. HDT data from ASTM D648 is used in material selection for plastic components in automotive, appliance, electronics, and industrial applications where exposure to elevated temperatures during processing, assembly, or service is a design consideration.

Shore Hardness Testing

Hardness in polymeric materials  –  from the firm rigidity of a structural thermoplastic to the soft compliance of a rubber seal  –  is a property that directly affects product performance, user perception, and functional behaviour. Shore hardness testing quantifies this property across the full range of polymer stiffnesses encountered in industrial and consumer applications, from the softest elastomers used in gaskets and cushioning to the hardest engineering thermoplastics used in structural components.

Relevant ASTM Standards:

ASTM D2240 – Rubber and Plastic Shore Durometer Hardness ASTM D2240 evaluates the Durometer hardness of polymeric and plastic materials using two scales: Shore A for soft rubbers and elastomers, and Shore D for hard plastics and semi-rigid polymers. The test measures resistance to penetration by a standardised indenter under defined load conditions, providing a quick, reproducible quality-control measurement to verify material consistency, evaluate batch-to-batch variability, and confirm that materials meet their hardness specifications. Shore hardness testing is routinely applied in quality control for seals, gaskets, footwear soles, grips, bumpers, and plastic components across consumer and industrial applications.

Compression Set Testing for Elastomers and Rubbers

Rubber and elastomeric polymer components used as seals, gaskets, vibration isolators, and cushioning elements are subjected to sustained compressive deformation throughout their service life. The degree to which these materials permanently deform under constant compression  –  and fail to recover their original thickness when the load is removed  –  determines whether they will continue to seal, isolate, or cushion effectively after prolonged use. Compression set testing quantifies this residual deformation, providing data essential for predicting the long-term sealing and cushioning performance of elastomeric components.

Relevant ASTM Standards:

ASTM D395 – Compression Set of Rubber ASTM D395 determines the permanent deformation remaining in a rubber or elastomeric polymer specimen after being compressed under defined conditions of load, temperature, and time. Method B – the constant deflection method – is the most widely used procedure, compressing a specimen to a fixed percentage of its original thickness and measuring the residual deformation after recovery. Compression set data from ASTM D395 is used in the specification and quality control of rubber seals, O-rings, gaskets, vibration mounts, and any elastomeric component for which dimensional recovery under sustained compression is a functional requirement.

Water Absorption Testing for Plastics

When a plastic component absorbs moisture from its environment  –  through immersion, humidity exposure, or condensation  –  the absorbed water can cause the material to swell dimensionally, reduce its mechanical strength, alter its electrical insulation properties, and degrade its appearance. The degree to which a plastic absorbs moisture depends on its chemical structure, and understanding water absorption behaviour is a prerequisite for selecting plastic materials for wet-environment, food-contact, or outdoor applications.

Relevant ASTM Standards:

ASTM D570 – Water Absorption of Plastics. ASTM D570 measures the percentage weight increase of plastic specimens after immersion in water under defined temperature and time conditions. The test distinguishes between surface and bulk absorption, providing data relevant to the dimensional stability, retention of mechanical properties, and electrical performance of plastics in humid or wet environments. ASTM D570 data is used to qualify plastics for dishwasher-safe consumer products, bathroom accessories, outdoor signage, electrical enclosures, and any plastic application where moisture exposure is part of the service environment.

Chemical Resistance Testing for Plastics

Plastics in service are routinely exposed to cleaning agents, solvents, lubricants, food acids, cosmetics, and industrial chemicals. A plastic component that discolours, swells, loses strength, or becomes brittle after chemical contact has failed in a way that rigorous chemical compatibility testing at the material selection stage would have prevented. Chemical resistance testing provides quantitative, standardised data on how a plastic material responds to specific chemical environments, enabling engineers to select materials appropriate for their application’s chemical exposure conditions.

Relevant ASTM Standards:

ASTM D543 – Resistance of Plastics to Chemical Reagents. ASTM D543 evaluates the response of plastic materials to immersion in specified chemical reagents under controlled conditions, measuring changes in weight, dimensions, appearance, and mechanical properties. The standard provides a structured approach to chemical compatibility evaluation that covers household cleaners, solvents, acids, bases, and other common chemical environments. Results from ASTM D543 testing are used in material selection for food-contact packaging, chemical storage containers, medical devices, consumer product housings, and industrial components where chemical exposure is a service reality.

Moisture Content in Plastics (Loss-in-Weight Method)

Residual moisture content in hygroscopic thermoplastics  –  nylon, PET, polycarbonate, ABS, and others  –  is a critical processing variable. Even small amounts of moisture cause hydrolytic degradation during melt processing, reducing molecular weight, generating surface defects, degrading mechanical properties, and producing voids and splay marks in finished parts. Accurate moisture determination before processing is a fundamental quality control requirement in plastic manufacturing.

Relevant ASTM Standards:

ASTM D6869 – Coulometric and Volumetric Determination of Moisture in Plastics Using the Karl Fischer Reaction. ASTM D6869 provides both coulometric and volumetric Karl Fischer titration methods for the precise determination of moisture content in plastic materials. The Karl Fischer method directly measures water content rather than measuring total mass loss, making it more specific and accurate for moisture determination than gravimetric methods. This test is used in incoming material inspection, pre-drying verification, and production quality control for hygroscopic thermoplastics to ensure that moisture content is within the acceptable range before processing.

Oxygen Transmission Rate Testing for Polymer Films and Packaging

Polymer films used in food packaging, pharmaceutical blister packs, and barrier packaging applications must restrict the transmission of oxygen from the external atmosphere into the package interior. Oxygen ingress accelerates food spoilage, degrades pharmaceuticals, and shortens the shelf life of oxygen-sensitive products. Measuring the oxygen transmission rate (OTR) of a packaging film or barrier laminate under defined conditions is the fundamental test for quantifying its barrier performance and predicting shelf life.

Relevant ASTM Standards:

ASTM D3985 – Oxygen Gas Transmission Rate Through Plastic Film and Sheeting Using a Coulometric Sensor. ASTM D3985 measures the steady-state oxygen transmission rate through plastic films, sheets, laminates, and coated substrates using a coulometric detection system. The test is conducted under controlled temperature and humidity conditions. It provides the quantitative OTR data used in the selection and specification of barrier packaging materials for food, pharmaceutical, and speciality packaging applications where oxygen ingress must be controlled to protect product quality and shelf life.

Water Vapour Transmission Rate (WVTR) Testing for Packaging Films

Moisture transmission through packaging films affects the shelf life of dry foods, the stability of hygroscopic pharmaceuticals, and the moisture protection of electronic components. A packaging film with inadequate water vapour barrier performance allows moisture to permeate, compromising the product inside. WVTR testing under standardised conditions provides the barrier performance data that packaging engineers need to specify films for their application.

Relevant ASTM Standards:

ASTM F1249 – Water Vapour Transmission Rate Through Plastic Film and Sheeting Using a Modulated Infrared Sensor ASTM F1249 measures the water vapour transmission rate through plastic films, sheets, and laminates using a modulated infrared sensor detection system. This test method is widely specified for flexible packaging materials, including polyethylene, polypropylene, polyester, and laminated barrier films used in food, pharmaceutical, and speciality packaging, where moisture barrier performance is a product specification requirement.

Hydroxyl Number Testing for Polyurethane Polyols

Polyurethane formulations  –  used in foams, adhesives, coatings, elastomers, and sealants  –  are built from polyol components whose hydroxyl content directly determines the stoichiometry of the urethane reaction. Variations in hydroxyl number between polyol batches lead to inconsistent crosslink density, inconsistent foam density or hardness, and ultimately inconsistent end-product performance. Accurate measurement of the hydroxyl number is a fundamental quality-control requirement for polyurethane raw-material qualification and formulation development.

Relevant ASTM Standards:

ASTM D4274 – Hydroxyl Numbers of Polyols ASTM D4274 establishes the hydroxyl content of polyol raw materials for polyurethane systems using acetylation or phthalation reaction methods. The hydroxyl number – expressed as milligrams of potassium hydroxide equivalent per gram of polyol – is the fundamental raw material specification parameter for polyurethane formulation, enabling manufacturers to verify incoming polyol consistency, adjust formulations for batch-to-batch variability, and maintain the uniformity of polyurethane end products across production batches.

Accelerated UV Weathering Testing for Polymers and Plastics

Polymers and plastics used in outdoor applications  –  garden furniture, automotive exterior components, signage, solar panel frames, agricultural films, building products  –  are subject to continuous UV radiation, moisture cycling, and temperature extremes that degrade colour, surface gloss, mechanical properties, and long-term structural integrity. Accelerated UV weathering testing condenses years of outdoor exposure into weeks of controlled laboratory testing, enabling manufacturers to evaluate durability, predict service life, and compare material performance before committing to production specifications.

Relevant ASTM Standards:

ASTM D4329 – Fluorescent UV Exposure of Plastics ASTM D4329 specifies fluorescent UV-B 313 lamp exposure cycles for the accelerated weathering testing of plastic materials and coatings in outdoor UV environments. The test provides comparative UV degradation data  –  including changes in colour, gloss, tensile properties, and surface appearance  –  for material selection, product qualification, and service life prediction for plastics in outdoor applications.

ASTM D4459 – Accelerated Weathering of Plastics Intended for Indoor Use Under Xenon Arc Exposure ASTM D4459 evaluates the accelerated weathering performance of plastic materials intended for indoor use  –  such as automotive interior components, furniture, consumer electronics housings, and indoor signage  –  under xenon arc lamp exposure that simulates the spectrum and intensity of indoor lighting and window-filtered sunlight. Results support material selection and product qualification for plastics where resistance to indoor light-induced colour change and surface degradation is a specification requirement.

Solar Reflectance Index (SRI) for Polymer-Based Roofing and Coating Materials

Polymer-based roofing membranes, coatings, and surface materials must reflect solar radiation and efficiently emit absorbed heat to control building surface temperatures, reduce urban heat island effects, and improve building energy efficiency. The Solar Reflectance Index (SRI) is a standardised metric that quantifies combined solar and thermal performance, providing a single number for use in green building specifications, energy codes, and product certification programs.

Relevant ASTM Standards:

ASTM E1980 – Calculating Solar Reflectance Index of Horizontal and Low-Sloped Opaque Surfaces. ASTM E1980 calculates the Solar Reflectance Index for opaque surfaces,s, including polymer-based roofing membranes, coatings, and surface materials, by combining solar reflectance and thermal emittance measurements into a single performance index. SRI values calculated per ASTM E1980 are used in LEED certification, building energy codes, cool roof specifications, and product qualification programs for roofing and surface materials where thermal performance and energy efficiency are specification requirements.

Total Normal Emittance Testing for Plastic Surfaces

Thermal emittance  –  the efficiency with which a material surface radiates absorbed heat as infrared energy  –  is a critical thermal management parameter for plastic components in electronics, automotive, and building applications. A plastic surface with high emittance radiates heat effectively and remains cooler under the same heat load than one with low emittance. Accurate measurement of emittance enables designers to select surface materials and coatings that optimise thermal performance in applications where heat management is a design priority.

Relevant ASTM Standards:

ASTM E408 – Total Normal Emittance of Surfaces Using Inspection-Meter Techniques ASTM E408 measures the total normal emittance of material surfaces  –  including polymer-based coatings and plastic surfaces  –  using portable emittance meter techniques. This test is used to characterise thermal management materials, roofing products, building envelope components, and any surface for which the ratio of radiated heat emission to that of a perfect blackbody is a relevant performance parameter for design or specification purposes.

Peel Adhesion Testing for Polymer Laminates and Adhesive Bonds

Polymer films, laminates, and adhesive-bonded assemblies depend on the integrity of their bond interfaces for their performance and durability. A packaging laminate that delaminates at the seal, a polymer coating that peels from its substrate, or an adhesive-bonded plastic assembly that separates under stress  –  these are bond failures that peel strength testing catches before the product is committed to production or service.

Relevant ASTM Standards:

ASTM D903 – Peel or Stripping Strength of Adhesive Bonds ASTM D903 determines the peel or stripping strength of adhesive bonds in flexible laminates and bonded assemblies by measuring the force required to separate bonded layers at a defined peel angle and crosshead speed. This test is used in the qualification of polymer film laminates, adhesive-bonded packaging, protective film applications, and any bonded plastic or polymer assembly where interfacial adhesion is a performance-critical specification requirement.