Chemical Analysis and Polymer Structure

• Laboratories of separation methods
• Laboratories of spectral methods
• Laboratory of elemental analysis and electrochemistry
• Laboratory of solution methods
• Laboratory of special methods of materials evaluation
• Laboratory of mechanical properties of polymers

The members of this team have knowledge and experience in the field of analysis of plastics and additives for plastics by using both chemical and physical methods which use procedures according to international standards (ISO, DIN, ASTM) or which have either been modified in this laboratory or have been developed in PIB.

From the polymer chemistry viewpoint, the group has traditionally been focused on polyolefins (especially PE and PP).

Instrumental equipment enables the examining of:

• molecular structure of polymers
• non-polymeric components content and character of these such as fillers, stabilisers and other additives, impurities and residues from previous operations (e.g. traces of polymerisation catalyst residues, auxiliary materials, solvents)
• purity of input materials (monomers, auxiliary materials and additives)
• identification of polymers and/or unknown compounds present in the system.

Laboratories of separation methods

Chromatographic methods (GC/MS, GLC, HPLC) are used for:

• identification and determination of stabilisers and other additives in plastics as well as their transformation products (PP, PE, ABS, polystyrene, polycarbonates, PVC)
• analyses of deposits formed during plastics processing
• identification of bad odour volatile organic compounds using head-space technique in connection with closed loop stripping analysis and head-space analysis with gas chromatography and mass spectroscopy
• determination of trace impurities in monomers (CO, CO₂, AsH₃, PH₃, H₂S, COS, mercaptans, alcohols, ketones)
• determination of residual monomers in plastics using head-space technique with gas chromatography and mass spectroscopy (closed loop static and dynamic stripping analysis)
• analyses of oils, waxes, solvents and emulsifiers
• analyses of paint thinners
• gas analyses
• water analyses

Laboratories of spectral methods

Infrared spectroscopy is used for qualitative studies such as:

• identification of polymer materials, stabilisers and additives
• general identification of substances and purity determinations
• FTIR spectroscopy
• identification of small objects in materials with IR microscopy Continuum from size 15x15mm

and for quantitative studies, namely:

• determination of composition of copolymers, additive content in polymers, monitoring degradative changes in polymer
• degree of branching, degree of crystallinity of semicrystalline polymers, dichroic ratio in oriented polymers

UV-VIS-NIR spectroscopy is employed mainly for:

• determination of purity degree of organic solvents
• photometric control of stabiliser dosage in PP and PE
• determination of -OH groups in silica supports
• determination of polystyrene content in styrene (ASTM D2121)
• determination of p-tert-butylcatechol in styrene (ASTM D4590)
• spectrophotometric determination of some metals

NMR spectroscopy - examples of use:

• structure identification, purity determination, degree of deuteration
• determination of isomerisation degree of polymer chains
• branching of polymers, detection, identification and quantification of branches
• structural defects of macromolecules, tacticity determination
• analysis of propylene/ethylene or other 1-olefin copolymers, determination of number average molecular weight by means of quantitative end group analysis

Atomic absorption spectroscopy (AAS)
AAS is used for the qualitative and quantitative determination of metals. Possible applications: analysis of the catalytic systems, traces of catalyst residues in polymers, content of fillers, determination of metals in fillers etc.

Atomic absorption spectroscopy with electrothermal analysis (ETA-AAS)
Electrothermal analysis AAS in connection with microwaves decomposition is able to determine traces of metals at ppb levels. Possible application: determination of impurities in monomers.

Laboratory of elemental analysis and electrochemistry

The following determinations can be carried out in this laboratory:

• determination of water by the Karl Fischer procedure (including coulometric determination)
• determination of bromine index
• determination of carbon-black and ash content in plastics
• determination of active oxygen (peroxide level)
• polarographic determinations
• determination of F, Cl and Br in plastics, conductivity and pH determination

Laboratory of solution methods

The following activities of this department can serve as examples:

• determination of average relative molecular weights and distribution curves of HDPE, PP and their copolymers by using gel permeation chromatography (GPC) and viscometry
• viscometric determination of viscosity number and limiting viscosity number of polymers and copolymers in a given solvent and at a certain temperature according to ISO 1628 and ISO 307
• GPC determination of branched PE: the connection of GPC apparatus with the viscometer detector enables the determination of branching coefficient, branching factor and the distribution of branches in whole range of molecular weights measured
• determination of structure heterogeneities of PE and PP by the TREF method in analytical and preparative mode

Laboratory of special methods of materials evaluation

The following measurements can be carried out as routine activities:

Thermal analysis (DSC, TGA, DTA) is used especially for:

• determination of melting and crystallisation temperature
• determination of structure heterogeneity of PE (PP) by the SIS(SSA)/DSC
• determination of degree of crystallinity of polymers and composites
• measurement of glass transition temperature
• analysis of the blends of polymers on the basis of their characteristic melting temperatures
• study of the kinetics of crystallisation
• measurement at low temperatures (to -90 °C)
• determination of the thermooxidative stability of polyolefines
• measurement of the thermal stability and mass changes in temperature range 25-1000 °C
• determination of organic and inorganic part content in composites

Methods for measurements of segment distribution and short chain-branching in copolymers, composition and crystallisability distribution
Apart from GPC, isothermal crystallisation (measured by DSC) and NMR, the methods of fractional crystallisation either from solution or polymer melt are used, e.g.:

• temperature raising elution fractionation (TREF), composition distribution, crystallisability distribution
• successive multistep isothermal crystallisation (SIC or SIS)
• successive self nucleation annealing (SSA, SNA)
• combination of methods, e.g. TREF-SIC, TREF-SNA

Microscopy
In involves both optical microscopy for examination of samples in transmitted and reflected light and electron microscopy (fitted with SEM/EDX probe) which is applied for morphological studies of polymers, composite materials, fillers and other solid materials.
Typical examples of this method are:

• determination of particle size and shape
• dispersion of inorganic fillers and elastomers in composites
• qualitative and semiquantitative analysis of elements (EDX, Z=11+ or Z=5+) in ash of polymers and composites as well as in screenpack deposits and other solid substances

X-ray analysis.
The method is employed for both qualitative and quantitative analysis of samples, crystallinity determination, size of crystalline parts and determination of degree of orientation. Difractor SIEMENS D-500 is used.

Evaluation of powdered materials. The following methods are available:

• particle size determination (laser analyser, 0.02 - 2000 mm)
• determination of whiteness of powders and composite materials

Other methods of evaluation

• Flammability testing:
  • LOI determination according to (ISO 4589, CSN 640756)
  • UL-94 procedure (HB, V-0, V-1, V-2)
  • glow wire test (DIN IEC 695, CSN 345615)
  • combustible building materials (DIN 4102-1/B2)
  • determination of burning behaviour of interior materials (ISO 3795)
  • cleaning of parts according to ISO16 232
  • microtome cuts
  • emission properties of materials (PV 3341, PV 3900, PV3015, PV3925)