Chemical Composition Analysis of Recycled Materials: Testing Methods, Standards, and Applications

Recycled material chemical composition analysis is the systematic identification and quantification of polymers, elements, additives, and contaminants in recycled plastics, rubbers, and metals using spectroscopic, chromatographic, and thermal analytical techniques. Accurate compositional data is essential for incoming quality control, regulatory compliance with RoHS, REACH, and food-contact requirements, and verification of recycled content claims across global supply chains. This article explains typical sample types, key testing parameters, applicable standard test methods, and practical industry applications of chemical composition analysis for recycled materials.

Technical Overview

Recycled materials—including post-consumer recyclate (PCR), post-industrial recyclate (PIR), and outputs from both mechanical and chemical recycling processes—are inherently heterogeneous compared with virgin feedstock. Collection streams introduce mixed polymers, metal fragments, adhesives, printing inks, label residues, cleaning-agent residues, and legacy additives that may no longer be permitted under current regulations. Chemical composition analysis provides the objective analytical data needed to manage this variability.

The core objectives of chemical composition analysis for recycled materials are to confirm polymer identity and purity, quantify blend composition, detect and measure restricted substances, characterize additive and filler content, and demonstrate lot-to-lot consistency between production batches. Accredited third-party laboratories operating under ISO/IEC 17025 quality management systems typically perform this testing using a combination of spectroscopic, chromatographic, elemental, and thermal methods.

Because recycled feedstock may carry substances of very high concern from previous product lifecycles—such as brominated flame retardants, phthalate plasticizers, or heavy-metal pigments—comprehensive chemical characterization is a prerequisite for regulatory compliance, food-contact safety evaluation, and confident substitution of virgin resin with recyclate.

Testing Samples

Recycled Thermoplastics

The most common sample matrixes include recycled PET (rPET) in bottle-grade flakes, pellets, or fiber-grade form; recycled HDPE, LDPE, and PP from packaging, crates, and battery casings; and engineering recyclates such as rABS, rPC, rPA (nylon), rPS, and rPVC. Samples are submitted as flakes, granules, pellets, regrind, or finished parts containing recyclate.

Recycled Rubber and Elastomers

Samples include tire-derived crumb rubber, devulcanized and reclaimed rubber, thermoplastic elastomer (TPE/TPU) recyclate, and rubber-modified plastic blends. Analysis focuses on polymer type, carbon black and filler loading, and restricted substances such as PAHs and organotin compounds.

Recycled Metals and Metal-Bearing Streams

Recycled aluminum, copper, brass, zinc alloys, and steel scrap are analyzed for alloy composition and tramp elements. Shredded residues from waste electrical and electronic equipment (WEEE) and lithium-battery recycling streams are characterized for metal content and hazardous elements.

Other Recycled Feedstock

Additional sample types include glass cullet, recycled textile fibers, wood-plastic composites containing recovered fillers, and mixed plastic bales that require preliminary sorting verification before processing.

Testing Items

Typical testing parameters for recycled material chemical composition analysis include:

• Polymer identification and purity verification (PET, PE, PP, PS, ABS, PC, PA, PVC, PMMA, and others), including detection of polyolefin or PVC cross-contamination in PET streams
• Quantification of polymer blends and copolymer composition
• Elemental composition: major, minor, and trace elements, including ash and filler constituents (calcium carbonate, talc, titanium dioxide, glass fiber)
• Restricted heavy metals and elements: lead, cadmium, mercury, hexavalent chromium, arsenic, antimony, barium, selenium, and total bromine as an indicator of brominated flame retardants
• Brominated flame retardants: polybrominated biphenyls (PBBs), polybrominated diphenyl ethers (PBDEs), and HBCD
• Phthalate plasticizers: DEHP, DBP, BBP, DIBP, DINP, DIDP, and DNOP
• Other substances of concern: bisphenol A, short-chain chlorinated paraffins, polycyclic aromatic hydrocarbons (PAHs), organotin compounds, nonylphenol and its ethoxylates, and residual monomers such as styrene, acrylonitrile, vinyl chloride, and caprolactam
• Additives: phenolic and phosphite antioxidants, UV absorbers, hindered amine light stabilizers, slip and antistatic agents, and colorants
• Contaminants: PVC traces in rPET, EVA and PVDC barrier residues, silicones, adhesives, ink residues, metallic particles, and detergent residues
• Volatile organic compounds (VOCs) and odor-active species
• Moisture and volatile content, ash content, and carbon black loading
• Thermal identity markers: glass transition temperature, melting and crystallization behavior, and oxidation induction parameters

Testing Methods

Infrared and Raman Spectroscopy

Fourier transform infrared spectroscopy (FTIR) in ATR or transmission mode, performed in accordance with ASTM E1252 and ASTM D5576, is the primary technique for polymer identification and detection of foreign-polymer contamination. Raman spectroscopy is increasingly applied to dark or carbon-black-loaded recyclates where infrared signals are masked.

Chromatographic and Mass-Spectrometric Analysis

Gas chromatography–mass spectrometry (GC-MS) is used for phthalates, PAHs, flame retardants (PBBs and PBDEs per IEC 62321-6, phthalates per IEC 62321-8), and headspace VOC screening. Pyrolysis-GC/MS provides detailed polymer and additive fingerprints for complex or highly contaminated recycled matrixes. High-performance liquid chromatography (HPLC) and LC-MS quantify bisphenol A and phenolic antioxidants, while ion chromatography measures chloride as a PVC tracer and residual surfactant species.

Elemental Analysis

X-ray fluorescence (XRF) spectrometry delivers rapid screening of lead, cadmium, mercury, bromine, and chromium per IEC 62321-3-1, with quantitative wavelength-dispersive XRF performed per ASTM E1621. Confirmatory testing uses microwave acid digestion followed by ICP-OES or ICP-MS for lead, cadmium, and mercury per IEC 62321-4 and IEC 62321-5, with ICP-MS procedures aligned to ISO 17294-2. Hexavalent chromium is determined by alkaline digestion with colorimetric UV-Vis detection per IEC 62321-7-1. Migration-based elemental testing for toy applications follows EN 71-3 and ISO 8124-3.

Thermal and Gravimetric Analysis

Differential scanning calorimetry (DSC) per ISO 11357, ASTM E1356, and JIS K 7121 determines melting, crystallization, and glass transition behavior, confirming polymer identity and revealing polyolefin contamination in PET streams. Thermogravimetric analysis (TGA) per ISO 11358 and ASTM E1131 separates volatile, polymer, carbon black, and ash fractions to quantify filler loading. Conventional ash determination follows ISO 3451-1 and ASTM D5630, and glass-fiber content in reinforced recyclates is measured by calcination per ISO 1172.

Ancillary Physical-Chemical Characterization

Melt mass-flow rate per ISO 1133-1, ASTM D1238, and JIS K 7210 serves as an indirect indicator of molecular degradation and batch consistency. Moisture is determined by Karl Fischer titration per ASTM E203 and ISO 760, and density per ISO 1183 provides a rapid contamination screen. For electrical applications, recycled compounds may additionally be evaluated under the framework of UL 746A short-term property evaluations.

Applications

Chemical composition analysis of recycled materials supports decision-making throughout the recycling and manufacturing value chain:

• Incoming quality control and supplier qualification for compounders, extruders, and molders incorporating recyclate into new products
• Lot-to-lot consistency verification between recycled material production batches
• RoHS compliance verification for electrical and electronic products per Directive 2011/65/EU as amended by (EU) 2015/863, and China RoHS requirements under GB/T 26572
• REACH compliance screening of restricted substances and SVHC candidates under Regulation (EC) No 1907/2006
• End-of-life vehicle material compliance under Directive 2000/53/EC for automotive recyclate applications
• Food-contact safety evaluation of recycled PET and polyolefins against Regulation (EU) No 10/2011, 21 CFR 177.1630, and GB 4806.7, supporting recycling-process safety assessments
• Recycled-content verification and traceability support under EN 15343, underpinning mass-balance and recyclate certification claims
• WEEE and battery recycling stream characterization for metal recovery optimization
• Failure analysis of defects such as black specks, off-odors, discoloration, and embrittlement traced to recycled feedstock contamination
• Research and development of compatibilizers, decontamination processes, and recyclate formulation strategies

FAQ

What is included in recycled material chemical composition analysis?

A typical analytical program combines polymer identification by FTIR, elemental screening by XRF with ICP confirmation, restricted-substance testing for heavy metals, phthalates, and flame retardants, additive and filler quantification by chromatography and TGA, and thermal verification by DSC. The scope is tailored to the polymer type, intended application, and applicable regulations.

Why is PVC contamination in recycled PET such a critical parameter?

Trace PVC releases hydrogen chloride during PET melt processing at levels as low as tens of parts per million, causing molecular degradation, yellowing, and loss of mechanical strength. Chloride screening by ion chromatography or combustion analysis, combined with thermal identification, is therefore a standard quality gate for rPET.

Can recycled plastics be approved for food-contact applications?

Yes, when chemical composition analysis demonstrates that potential migrants—such as heavy metals, phthalates, VOCs, and legacy additives—remain within the limits of applicable food-contact regulations such as Regulation (EU) No 10/2011, 21 CFR 177.1630, and GB 4806.7, typically as part of a recycling-process safety evaluation.

How is recycled content in a material verified?

Recycled content is primarily verified through traceability and chain-of-custody documentation under EN 15343, supported by analytical evidence that the material composition is consistent with the declared recyclate stream rather than disputed purely by measurement alone.

How much sample is required, and what is the typical turnaround time?

Most spectroscopic, thermal, and elemental tests require only a few grams of material, while comprehensive restricted-substance panels may require 20 to 50 grams depending on the polymer and digestion method. Standard turnaround at accredited third-party laboratories is typically five to ten working days, with expedited options available.

What accreditation should the testing laboratory hold?

Testing should be performed by laboratories accredited to ISO/IEC 17025 for the specific test methods used, ensuring that results are technically valid, traceable to international standards, and acceptable to regulators, certification bodies, and downstream customers.