Guide to Laboratory Testing of Plastics and Polymers

Updated April 30, 2026, to include additional testing methods and key ASTM and ISO standards for polymer testing

Introduction: Why Rigorous Polymer Testing Is Essential

Plastics and polymers are the most widely used class of engineering materials in the world — present in automotive components, medical devices, food packaging, electronic enclosures, aerospace structures, construction materials, consumer goods, and textiles. Global plastic production exceeds 400 million metric tons per year, spanning a material universe of thousands of distinct polymer types, grades, and formulations, each with different mechanical, thermal, chemical, and electrical properties.

Laboratory testing of plastics and polymers serves multiple commercial purposes: quality control at incoming material receipt (verifying that resin pellets match the specification); product development and formulation (optimizing blend ratios, additive concentrations, filler loading); regulatory compliance (food contact migration testing, RoHS/REACH restricted substances, biocompatibility for medical plastics); failure analysis (identifying why a part failed in service); and competitive intelligence (reverse-engineering competitor materials).

ContractLaboratory.com connects manufacturers, materials engineers, quality teams, and R&D organizations with accredited polymers, plastics, and rubber testing laboratories and materials evaluation and testing specialists. See also our detailed guides to polymer material performance testing and size exclusion chromatography/GPC for polymers.

Major Polymer Classes and Their Testing Priorities

Testing requirements are driven by both polymer type and application. The major classes and their primary testing priorities:

• Commodity thermoplastics (PE, PP, PVC, PS, PET): Melt flow rate (MFI/MFR), tensile and flexural properties, density, HDT/Vicat softening temperature, impact resistance, UV/weathering stability for outdoor applications. Food contact migration testing for packaging applications.
• Engineering thermoplastics (ABS, PC, PA/nylon, POM, PBT, PEEK): Mechanical properties at elevated temperatures (HDT, DMA), dimensional stability (TMA/CTE), impact strength at low temperatures, chemical resistance, UL 94 flammability rating (for electronics applications), and surface hardness.
• Thermosets (epoxy, polyurethane, polyester, phenolics, silicone): Cure characterization by DSC, crosslink density, glass transition temperature (Tg), hardness, adhesion, flexural modulus, thermal stability by TGA.
• Elastomers and rubbers (natural rubber, EPDM, NBR, SBR, silicone): Tensile strength and elongation at break, Shore A durometer hardness, compression set, ozone resistance, heat aging, and dynamic mechanical properties.
• Biopolymers and biodegradable plastics (PLA, PHA, starch blends): Disintegration/biodegradation testing per ISO 14855/ASTM D5338, thermal characterization by DSC, mechanical properties, moisture uptake.
• Recycled content plastics: Contamination screening by FTIR, melt flow rate before/after reprocessing cycles, mechanical property retention, additive quantification, and Py-GC-MS for polymer blend identification.

Chemical and Structural Analysis

FTIR and ATR-FTIR — The Foundation of Polymer Identification

Fourier Transform Infrared (FTIR) spectroscopy is the single most widely performed polymer identification test. Every polymer type produces a characteristic infrared absorption spectrum — a vibrational fingerprint — by which it can be identified and distinguished from other polymers. Comparison against reference library spectra provides rapid, definitive polymer identification without complex sample preparation.

The most common FTIR sampling mode for plastics is ATR-FTIR (Attenuated Total Reflectance FTIR): a flat piece of polymer is pressed against a crystal (zinc selenide, diamond, or germanium), and the evanescent wave penetrates approximately 1–2 μm into the surface. The result is a spectrum representative of the polymer composition in the surface layer — collected in seconds, without sample preparation, and non-destructive in many cases. ATR-FTIR is the standard method for:

• Polymer type identification: Distinguishing PE from PP from PVC from ABS from PC — critical for incoming raw material verification, recycled content characterization, and failure analysis where material mislabeling is suspected.
• Contamination identification: Identifying foreign materials in polymer moldings, coatings, or films. FTIR microscopy (FTIR microspectroscopy) can map contaminants at the micron scale in cross-sectioned parts.
• Degradation product detection: Polymer oxidation and hydrolysis produce characteristic carbonyl and hydroxyl peaks visible in FTIR spectra. Tracking oxidation induction time (OIT) and oxidative degradation in aged vs. reference materials by DSC combined with FTIR provides a comprehensive thermal/oxidative stability assessment.
• Additive and filler characterization: Identifying common polymer additives (antioxidants, plasticizers, flame retardants, compatibilizers) and fillers (calcium carbonate, talc, glass fiber, carbon black) from their characteristic absorption bands.

Complementary spectroscopic techniques: Raman spectroscopy — particularly useful for colored plastics where IR absorption is problematic; differentiates PE from PP with high precision; used for microplastics identification at sub-20 μm resolution. X-Ray Fluorescence (XRF) — rapid, non-destructive elemental analysis for heavy metals and halogen screening in RoHS/REACH compliance testing. NMR spectroscopy — definitive structural characterization of polymer microstructure, copolymer composition, and tacticity.

GPC/SEC — Molecular Weight Distribution

Gel Permeation Chromatography (GPC), also called Size Exclusion Chromatography (SEC), determines the complete molecular weight distribution of a polymer: Mn (number-average molecular weight), Mw (weight-average molecular weight), and dispersity Đ (Mw/Mn, formerly polydispersity index, PDI). These parameters directly govern processing behavior (melt viscosity, flow), mechanical properties (strength, toughness), and end-use performance.

Standard GPC conditions: organic solvent systems (THF for most thermoplastics; DMF for polyamides; trichlorobenzene at 150°C for polyolefins); differential refractive index (dRI) detector as primary concentration detector; optional multi-angle light scattering (MALS) for absolute molecular weight without column calibration standards. For absolute MW determination, GPC-MALS (SEC-MALS) eliminates assumptions about polymer conformation inherent in conventional calibration. See our detailed guide to SEC/GPC for polymers for comprehensive coverage.

Py-GC-MS — Pyrolysis Gas Chromatography-Mass Spectrometry

Pyrolysis-GC-MS thermally decomposes polymer samples into characteristic molecular fragments that are separated by GC and identified by MS. It is the method of choice for: identifying polymer types in complex blends; characterizing copolymer composition; identifying unknown additives, stabilizers, and plasticizers that are not IR-detectable; and forensic analysis of counterfeit materials. Unlike FTIR, Py-GC-MS provides quantitative compositional data on multi-component systems and can resolve closely related polymer structures that produce overlapping FTIR spectra.

Thermal Analysis Methods

Three thermal analysis instruments provide complementary information on polymer thermal behavior:

• Differential Scanning Calorimetry (DSC — ASTM E1356/ISO 11357): Measures heat flow as a function of temperature. Provides: glass transition temperature (Tg) for amorphous polymers; melting temperature (Tm) and crystallization temperature (Tc) for semi-crystalline polymers; degree of crystallinity; heat of fusion; cure characterization for thermosets; oxidation induction time (OIT) for antioxidant content assessment. DSC is the most widely used polymer thermal analysis technique.
• Thermogravimetric Analysis (TGA — ASTM E1131/ISO 11358): Measures weight loss as a function of temperature under controlled atmosphere. Provides: thermal stability and decomposition temperature; filler and ash content (e.g., glass fiber content in composites); residual moisture and volatile content; polymer blend composition based on sequential decomposition stages; carbon black content in polyolefins.
• Dynamic Mechanical Analysis (DMA/DMTA — ASTM E1640/ISO 6721): Applies an oscillating stress to a polymer specimen over a temperature range and measures the storage modulus (E’, elastic response), loss modulus (E”, viscous response), and tan delta (damping). DMA provides the most sensitive and accurate measurement of Tg, detects multiple transitions (secondary relaxations), characterizes viscoelastic behavior for vibration damping applications, and evaluates cure completeness in thermosets.
• Thermomechanical Analysis (TMA — ASTM E831/ISO 11359): Measures dimensional changes in a polymer specimen as a function of temperature under minimal load. Provides: coefficient of thermal expansion (CTE) — critical for polymer-metal assemblies where CTE mismatch drives stress; softening temperature under penetration mode; anisotropy of expansion in reinforced composites.

Heat Deflection Temperature (HDT) and Vicat Softening Temperature

• HDT / Deflection Temperature Under Load (DTUL — ASTM D648 / ISO 75): The temperature at which a polymer beam of standardized dimensions deflects 0.25 mm under a 3-point bending load of 0.455 MPa (66 psi) or 1.82 MPa (264 psi). HDT is the most widely cited indicator of a polymer’s practical upper service temperature and appears on every commercial polymer datasheet. Filled/reinforced polymers have significantly higher HDT than unfilled versions — glass fiber reinforcement typically increases HDT by 50–100°C.
• Vicat Softening Temperature (VST — ASTM D1525 / ISO 306): The temperature at which a flat-ended needle of 1 mm² cross-section penetrates a test specimen 1 mm under a specified load (10 or 50 N). The Vicat temperature is usually higher than HDT and provides a measure of the temperature at which significant softening begins. Used for material selection in continuous-use temperature specifications.

Mechanical Testing of Plastics and Polymers

Tensile Testing — ASTM D638 / ISO 527

Tensile testing is performed on dumbbell-shaped specimens (dogbones) pulled apart at a defined crosshead speed. Key outputs: tensile strength at break (MPa or psi — maximum stress before failure); tensile modulus (Young’s modulus — slope of the linear stress-strain region, a measure of stiffness); elongation at break (% — total extension at failure, indicating ductility vs. brittleness). ASTM D638 (US standard) and ISO 527 (international, used in EU, Asia-Pacific, automotive) use different specimen geometries (Type I vs. 1A) and speed requirements — results can differ between standards and are not directly interchangeable. Both standards and their outputs should be specified when ordering tensile testing for global markets.

Impact Testing — ASTM D256 (Izod) / ASTM D4812 / ISO 179 (Charpy) / ISO 180

Impact resistance testing measures the energy absorbed by a polymer specimen when struck by a pendulum swinging at a controlled velocity:

• Izod impact (ASTM D256 / ISO 180): The specimen is held vertically and struck on one face. Results are expressed as energy absorbed per unit width (J/m or ft·lb/in). Notched Izod is the most common form — the notch concentrates stress and identifies brittle vs. ductile failure modes. Unnotched Izod is also performed.
• Charpy impact (ISO 179 / ASTM D6110): The specimen is supported horizontally at both ends and struck in the center. Charpy is the preferred impact test in European and Asian markets and better correlates with thin-section performance in some applications. ISO 179 is the standard form of Charpy for plastics.
• Falling weight/drop weight impact: Used for sheet, film, and thin-section parts; measures multiaxial impact behavior more relevant to real-world loading than notched pendulum tests.

Flexural Testing — ASTM D790 / ISO 178

Flexural properties are measured by a 3-point or 4-point bend test, where a rectangular specimen is supported at two points and loaded at the center. Key outputs: flexural strength (stress at failure or 5% strain, whichever occurs first); flexural modulus (stiffness in bending). Particularly important for rigid plastics and structural composites. ASTM D790 and ISO 178 use different specimen dimensions and strain rate criteria — results should be specified by standard when ordering.

Hardness — ASTM D2240 (Shore) / ASTM D785 (Rockwell) / ASTM D2583 (Barcol)

Shore durometer hardness is the most widely used hardness test for flexible and semi-flexible polymers: Shore A for flexible materials (elastomers, soft plastics); Shore D for harder materials (semi-rigid to rigid plastics). The test indents the surface with a standardized needle under defined load and time — lower numbers indicate softer materials. Rockwell hardness (R or L scale) is used for rigid engineering plastics. Barcol hardness is used specifically for fiber-reinforced composites.

Melt Flow Rate (MFR / MFI) — The Processability Test

Melt Flow Rate (MFR), also called Melt Flow Index (MFI), is the most commercially important processability test for thermoplastic resins. It quantifies how easily a molten polymer flows under defined conditions: ASTM D1238 and ISO 1133 specify a temperature and load appropriate to each polymer family, and the mass of polymer extruded in 10 minutes through a standardized die is measured and reported in g/10 min.

MFI is critical for: incoming raw material verification (every PE, PP, ABS, PS, PET, nylon datasheet lists MFI at specific conditions); detecting polymer degradation from reprocessing (MFI increases as molecular weight decreases during thermal/oxidative degradation); grade differentiation within a polymer family (injection moulding grades are high-MFI; blow moulding grades are low-MFI; sheet extrusion grades are very low MFI); and detecting counterfeit or mislabeled materials (MFI mismatch immediately flags a suspect material). MFI testing can be performed on pellets, regrinds, films, or molded specimens dissolved and reprecipitated for reliable results.

Flammability and Fire Safety Testing

UL 94 — Flammability Ratings for Plastic Parts

UL 94 (Underwriters Laboratories Standard for Flammability of Plastic Materials for Parts in Devices and Appliances) is the most commercially referenced plastics flammability standard globally — it is a prerequisite for virtually every plastic component used in electronics, electrical equipment, and appliances. UL 94 classifies materials into ratings based on burn behavior under two test geometries:

• Horizontal Burning — HB: The lowest classification. The specimen must stop burning within 76 mm of the flame impingement, or have a burning rate below 40 mm/min (for specimens under 3 mm thick) or 75 mm/min (over 3 mm). HB materials are acceptable only in low-risk applications.
• Vertical Burning — V-2, V-1, V-0: The flame is applied to the bottom of a vertically suspended specimen. V-0 is the most flame-retardant classification: the specimen must extinguish within 10 seconds of each of two 10-second flame applications, without dripping ignited particles. V-1 allows 30-second extinguishing with non-igniting drips. V-2 allows 30-second extinguishing but permits drips of ignited particles. Electronic housings, switches, and connectors typically require V-0 or V-1.
• 5VA and 5VB: The most stringent UL 94 ratings for sheet and molded materials — tested with a more severe flame. 5VA materials form no burn-through holes; 5VB allows burn-through in sheet specimens.

UL 94 rating is thickness-dependent — a material may be V-0 at 3.2 mm but only V-1 at 1.6 mm. Test reports must specify the thickness at which each rating was achieved.

Limiting Oxygen Index (LOI) — ASTM D2863 / ISO 4589

The Limiting Oxygen Index (LOI) is the minimum concentration of oxygen in a nitrogen/oxygen mixture that supports sustained combustion of a polymer specimen under defined conditions. LOI values above 21% indicate that the polymer will not sustain combustion in normal air (21% oxygen). Materials with LOI > 28% are considered flame-retardant by most standards. Common LOI values: polyethylene ~17%; polypropylene ~17%; PVC ~45%; PTFE ~95%. LOI is a quantitative comparative metric and is widely used in polymer flammability research and flame retardant development.

Electrical Testing of Polymers

Electrical properties of polymers are critical for applications in electronics, cables, connectors, and insulating materials. Key electrical tests:

• Volume resistivity and surface resistivity (ASTM D257): Measures the resistance to the passage of current through the bulk and across the surface of a polymer. Insulators have volume resistivity >10¹² Ω·cm; conductive compounds (with carbon black or metal fillers) can be engineered to 10² Ω·cm. Critical for selecting insulating materials and specifying antistatic grades.
• Dielectric constant and dissipation factor (ASTM D150 / IEC 60250): The dielectric constant (relative permittivity) measures the ability of a material to store electrical energy. Low dielectric constant materials (PTFE, liquid crystal polymers) are preferred for high-frequency circuit boards to minimize signal loss. The dissipation factor measures energy loss as heat — important for microwave and RF applications.
• Dielectric strength/breakdown voltage (ASTM D149): The voltage per unit thickness at which a dielectric polymer fails (breaks down) — expressed in kV/mm or V/mil. Critical for electrical insulation applications.
• Arc resistance (ASTM D495): Time for a high-voltage, low-current arc to cause surface tracking failure — important for switch and circuit breaker components.

Weathering and Environmental Aging Testing

Polymers exposed to outdoor environments or UV light undergo photodegradation, oxidative aging, and hydrolysis that reduce mechanical properties, cause color change, and promote surface cracking. Accelerated weathering tests simulate years of outdoor exposure in weeks or months:

• UV fluorescent lamp weathering (ASTM G154 / ISO 4892-3): Uses UV fluorescent bulbs (UVA-340 lamps best simulate solar UV) to accelerate UV degradation. Results measured after specified irradiation hours: tensile strength retention %, elongation retention %, color change (ΔE by CIELAB colorimetry), gloss retention, and visual assessment of chalking/cracking.
• Xenon arc weathering (ASTM G155 / ISO 4892-2): The xenon arc lamp most closely replicates the full solar spectrum (UV + visible + infrared). Used when both UV and visible light-induced degradation are relevant. Also used for automotive interior and exterior plastic specifications, which typically require xenon arc rather than UV fluorescent.
• ASTM D4329 and D4587: Specific standard practices for UV weathering of plastics and coatings, providing defined exposure cycles including UV light + condensation phases.
• Salt spray/salt fog (ASTM B117): Widely used for coated plastic parts and plastic assemblies with metal inserts to assess corrosion resistance of surface treatments and adhesive joints.
• Thermal aging (ASTM D3045): Elevated temperature oven aging to assess thermal oxidative stability of polymer compounds — determines how well antioxidant packages perform over time at elevated use temperatures.

Chemical Resistance and Environmental Stress Cracking

Chemical resistance testing evaluates a polymer’s ability to maintain its properties when exposed to specific chemicals, solvents, fuels, cleaning agents, or biological fluids:

• Immersion testing (ASTM D543 / ISO 175): Specimens are immersed in test chemicals for defined periods, then evaluated for change in mass, dimensions, tensile properties, and visual appearance. Test liquids are selected based on the intended use environment.
• Environmental Stress Cracking Resistance (ESCR — ASTM D1693 / ASTM D2561): Measures the susceptibility of polyethylene and other thermoplastics to cracking when stressed in the presence of a stress-cracking agent (e.g., Igepal CO-630 surfactant). ESCR is a critical quality parameter for PE bottles and containers — failure in service due to ESCR is one of the most common causes of field recalls.
• Solvent resistance: Many engineering plastics (PC, ABS) are susceptible to stress cracking in the presence of specific solvents, cleaning agents, or mold release compounds. Chemical compatibility mapping against the intended use environment is essential for material selection.

Regulatory Compliance Testing

Food Contact Compliance — FDA 21 CFR and EU Regulation 10/2011

Plastics used in food contact applications — packaging films, containers, utensils, food processing equipment — must be tested for compliance with food safety regulations governing which substances may be present and at what levels:

• FDA 21 CFR (Parts 177 and 178): US regulations listing which polymers and additives are approved for specific food contact uses. Compliance testing involves overall migration testing (total extractables into standardized food simulants) and specific migration testing for regulated substances such as bisphenol A (BPA), BADGE, vinyl chloride monomer (VCM), and antimony from PET catalysts.
• EU Regulation No. 10/2011 (Plastic Food Contact Materials): The EU framework for food contact plastics, listing authorized substances and their Specific Migration Limits (SMLs) in mg/kg food. Migration testing uses standardized simulants: 10% ethanol (aqueous foods), 95% ethanol (alcoholic foods), 3% acetic acid (acidic foods), and isooctane or ethanol 50% (fatty foods). Migration testing is performed at 10°C, 20°C, or 40°C, depending on food type, or at 70°C for heat-processed foods.

RoHS and REACH — Restricted Substances Compliance

Plastics used in electronics, electrical equipment, and other consumer products must be screened for restricted substances under EU environmental regulations:

• RoHS (Restriction of Hazardous Substances Directive, EU 2011/65/EU): Restricts six substances in electrical and electronic equipment: lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls (PBBs), and polybrominated diphenyl ethers (PBDEs). Later amendments added DEHP, BBP, DBP, and DIBP phthalates. Screening by XRF (X-ray fluorescence) provides rapid non-destructive screening; confirmation of positives by ICP-MS (metals) or GC-MS (organics/phthalates).
• REACH SVHC (Substances of Very High Concern): EU Regulation 1907/2006 REACH requires manufacturers to communicate about Substances of Very High Concern present in articles above 0.1% by weight. The SVHC candidate list continuously expands and includes phthalate plasticizers (DEHP, DBP, BBP, DIBP), flame retardants (TBBPA, HBCD), and other regulated chemicals commonly found in plastics formulations.

Medical Device Biocompatibility — ISO 10993 Series

Plastics used in medical devices — from simple packaging to implantable components — must undergo biocompatibility evaluation per ISO 10993 (Biological evaluation of medical devices). The scope of testing is determined by the nature and duration of patient contact:

• ISO 10993-1: Evaluation and testing within a risk management process — the framework standard that maps contact type and duration to required testing.
• ISO 10993-5 (Cytotoxicity): Cell culture testing for cytotoxic effects — the first biocompatibility test performed, using extract-based, agar diffusion, or direct contact methods.
• ISO 10993-10 (Sensitization): Guinea pig maximization test or murine local lymph node assay — evaluates potential for allergic sensitization.
• ISO 10993-12 (Chemical characterization of medical device materials): Extractables and leachables testing — identifying and quantifying chemical substances that may migrate from the polymer into body fluids under simulated use conditions.

Key ASTM and ISO Standards for Polymer Testing: Quick Reference

Failure Analysis of Polymer Components

When a polymer part fails in service, laboratory testing identifies the root cause. Failure analysis is one of the highest-value services in polymer testing, combining multiple analytical techniques:

• Visual and stereomicroscopic examination: Fracture surface morphology — brittle cleavage, ductile tearing, fatigue striations, impact failure — provides immediate clues about failure mode and direction of crack propagation.
• SEM (Scanning Electron Microscopy) and EDX: Fracture surface examination at high magnification; SEM-EDX provides elemental analysis of contaminants, inclusions, or failure-initiating features.
• FTIR of failed material vs. reference: Detects oxidation, hydrolysis, contamination, or wrong material at the failure site.
• DSC of failed material vs. reference: Detects changes in crystallinity, thermal history, or degradation (loss of antioxidant/stabilizer OIT) that may have contributed to failure.
• GPC of failed material vs. reference: Molecular weight reduction indicates thermal/oxidative degradation or stress cracking (chain scission) at the molecular level.
• Stress analysis and load simulation: Combined with finite element analysis (FEA) using laboratory-measured mechanical properties, to determine whether service stresses exceeded material capabilities.

Finding Accredited Plastics and Polymer Testing Laboratories

Polymer testing laboratories range from general-purpose materials testing labs (offering standard mechanical, thermal, and chemical tests) to highly specialized facilities (polymer GPC/SEC, food contact migration, biocompatibility, advanced spectroscopy). For regulated testing (food contact compliance, RoHS/REACH, medical device biocompatibility), laboratories must hold ISO/IEC 17025 accreditation for the specific methods required, and may need additional credentials (FDA facility registration for medical device testing, state certification for environmental testing).

ContractLaboratory.com connects manufacturers, R&D teams, quality engineers, and procurement organizations with specialized polymers, plastics, and rubber testing laboratories for the full spectrum of polymer characterization and compliance testing. See related resources: polymer material performance testing guide, SEC/GPC molecular weight analysis, chromatography types guide, and materials evaluation and testing.

Frequently Asked Questions About Plastics and Polymer Testing

Conclusion

Laboratory testing of plastics and polymers spans a remarkably comprehensive analytical toolkit: chemical identification by FTIR and spectroscopy; molecular weight characterization by GPC/SEC; processability assessment by melt flow index; thermal characterization by DSC, TGA, DMA, and TMA; mechanical performance by tensile, impact, flexural, and hardness testing; fire safety qualification by UL 94 and LOI; environmental durability by weathering and chemical resistance testing; and regulatory compliance across food contact, RoHS/REACH, and biocompatibility frameworks. No single test characterizes a polymer completely — comprehensive material qualification requires a strategically selected battery of tests matched to the material’s application requirements and the regulatory standards governing its end use.

ContractLaboratory.com connects polymer manufacturers, processors, importers, and product developers with accredited polymers, plastics, and rubber testing laboratories for the full spectrum of polymer testing. Submit a testing request or contact our team.