Task 39
Task 39
SHC Task 39

Polymeric Materials for Solar Thermal Applications

Polymeric Materials and Solar Glossary

Polymeric Materials

Solar Thermal Systems

Polymeric Materials


ABS Acrylonitrile butadiene styrene
CPVC Chlorinated polyvinyl chloride
EPDM Ethylene Propylene Diene Monomere
HD-PE High density polyethylene
hPE High chlorinated PE
IIR Isoprene-isobutene rubber
PA Polyamide
PBT Polybutylene terephthalate
PC Polycarbonate
PE Polyethylene
PEEK Polyetheretherketone
PEI Polyetherimide
PERT Raised temperature PE
PES Polyethersulphone
PEX Cross-linked polyethylene
PTFE Polytetrafluoroethylene
PFA Perfluoroalkoxy polymer resin (see Teflon)
PLS Polysulfone
PMMA Polymethyl methacrylate
POM Polyoxymethylene, also known as
acetal resin, polytrioxane, polyformaldehyde, and paraformaldehyde
PP Polypropylene
PPA Polyphtalamide
PPE Polyphenylene ether
PPS Polyphenylene sulfide
PS Polystyrene
PSU Polysulfone, or PSU, is a polymer thermoplastic material
PU Polyurethane
PVC Polyvinyl Chloride
PPO Polyphenyleneoxid
PBTP, PBT Polybutylene Terephthalate
PTFE Polytetrafluoroethylene
TPE Thermo plastic elastomer

Brand Names1

Beta-PPR Borealisgroup PP Random Co-polymer
GRILAMID EMS-Chemie PA, transparent, PA12
LEXAN SABIC Innovative Plastics PC
NORYL SABIC Innovative Plastics PPE/PS or PPO/PS
PPR Borealisgroup PP Random Co-polymer
RYTON Chevron Phillips Chemicals PPS
XTEL Chevron Phillips Chemicals PPS alloys

1 Only brand names of Task 39 industry partners included

Terms and Definitions

Additive - In the plastics industry: materials added in minor amounts to basic resins or compounds to alter properties. Examples include flame retardants, thermal stabilizers, and UV stabilizers.

Aging - The process of, or the results of, exposure of plastics to natural or artificial environmental conditions for a prolonged period of time.

Abrasion Resistance - The ability of a material to withstand mechanical actions such as rubbing, scraping, or erosion, that tends progressively to remove material from its surface. Additive - In the plastics industry: materials added in minor amounts to basic resins or compounds to alter properties.

Aging - The process of, or the results of, exposure of plastics to natural or artificial environmental conditions for a prolonged period of time.

Alloy - A term used in the plastics industry to denote blends of polymers or copolymers with other polymers or elastomers. - i.e. ABS/Polycarbonate.

Amorphous - Devoid of crystallinity or stratification. Most plastics are amorphous at processing temperatures.

Annealing - The process of relieving stresses in moulded plastic articles by heating to a predetermined temperature, maintaining this temperature for a predetermined length of time, and slowly cooling the articles to be painted which might craze due to solvent attack.

ASTM - Abbreviation for American Society for Testing and Materials.

ATR Spectroscopy- Attenuated Total Reflectance Spectroscopy - Characteristic (vibration) absorption bands in infrared range

Blow Moulding - The process of forming hollow articles by expanding a hot plastic element called a parison against the internal surfaces of a mould.

Bulk Density -The density of a modking material in loose form expressed as a ratio of weight to volume.

Charpy Impact Test - A destructive test of impact resistance, consisting of placing the specimen in a horizontal position between two supports, then applying a blow of known magnitude. If the specimen does not break, a new specimen is put in position and the magnitude is increased until the specimen breaks. (ASTM D-256, Method B)

Coextrusion - The process of extruding two or more materials through a single die with two or more orifices arranged so that the extrudates merge and weld together into a laminar structure before chilling.

Composite - An article or substance containing or made up of two or more different substances.

Compound - A mixture of resin and the ingredients necessary to modify the resin to a form suitable for processing into finished articles.

Compounding - The step of mixing base resins with additives such as stabilizers, fillers, pigments into a form suitable for processing into finished articles

Compression Moulding - A method of melding in which the melding material, generally preheated, is placed in an open heated mould cavity, the mould is closed with a top force, pressure is applied to force the material into contact with all mould areas, and heat and pressure are maintained until the melding material has cured. This process is most often used with thermoses.

Copolymer - This term usually, but not always, denotes a polymer of two chemically distinct monomers. Due to its viscoelastic nature, a plastic subjected to a load for a period of time tends to deform more than it would from the same load released immediately after application, and the degree of this deformation is dependent of the load duration.

Cross-Linking - The setting up of chemical links between the molecular chains.

Crystal - A homogeneous solid having an orderly and repetitive three-dimensional arrangement of its atoms.

Degradation - A deleterious change in the chemical structure, physical properties or appearance of a plastic caused by exposure to heat, light, oxygen or weathering.

DEA - Dielectric Analysis - A technique for investigating the processing behaviour and physical and chemical structure of polymers by measuring the dielectric properties (permittivity and loss factor). Characterization of curing process and crosslinking density. Characterization of curing process; characterization of crosslink density principle source

DMA - Dynamic Mechanical Analysis - A technique for observing the viscoelastic properties of polymers. Characterization of thermo-mechanical properties (e.g. E-Modulus, glass transition temperature, crosslinking density). Characterization of thermo-mechanical properties; determination of Glass transition temperature; determination of crosslink density

DSC - Differential Scanning Calorimetry - Characterisation of thermal behaviour

Elastomer - A material, which at room temperature can be stretched repeatedly to at least twice its original length and, upon immediate release of the stress, will return with force to its approximate original length.

Engineering Plastics - A broad term covering all plastics, with or without fillers or reinforcements, which have mechanical, chemical and thermal properties suitable for use, in construction, machine components and chemical processing equipment.

Extruder - A machine for producing more or less continuous lengths of plastics sections such as rods, sheets, tubes, and profiles.

Extrusion - The process of foaming continuous shapes by forcing a molten plastic material through a die.

Elastomer - Amorphous crosslinked polymer, glass transition below room temperature.

Filler - A relatively inert substance added to a plastic compound to reduce its cost and/or to improve physical properties, particularly hardness, stiffness and impact strength.

Fatigue strength - Stress level at which polymer can endure N cycles.

Flame Retardant - Having the ability to resist combustion (A flame retardant plastic is considered to be one that will not continue to burn or glow after the source of ignition has been removed.)

Flame Retardants - Additives that reduce the tendency of plastics to burn.

Glass Fibers - A family of reinforcing materials for reinforced plastics based on single filaments of glass.

Glass Transition Temperature - The temperature at which a polymer changes from (or to) a viscous or rubbery condition (or from) a hard and relatively brittle one.

Impact Resistance - The resistance of plastic articles to fracture under stresses applied at high speeds.

Impact Strength - The ability of a material to withstand shock loading.

Injection Melding - The method of forming objects from granular or powdered plastics, most often of the thermoplastic type, in which the materials is fed from a hopper to a heated chamber in which it is softened, after which a ram or screw forces the material into a mould. Pressure is maintained until the mass has hardened sufficiently for removal from the mould.

ISO - Abbreviation for the International Standards Organization.

Izod Impact Strength - A measure of impact strength determined by the difference in energy of a swinging pendulum before and after it breaks a notched specimen held vertically as a cantilever beam.

Melt Index - The amount of a thermoplastic resin, measured in grams, which can be forced through a specified orifice within ten minutes when subjected to a specified force. (ASTM D-1238)

Moisture Absorption - The pick-up of moisture from the environment by a material.

Mould (n) - A hollow form or matrix into which a plastic material is placed and which imparts to the material its final shape as a finished article.

Mould (v) - To impart shape to a plastic mass by means of a confining cavity or matrix.

Mould Release - In injection melding, a lubricant used to coat the surface of the mould to enhance ejection of the moulded article or prevent it from sticking to the tool.

Melding Cycle - The period of time occupied by the complete sequence of operations on a melding press requisite for the production of one set of moulded articles.

Melding Pressure - The pressure applied to the ram of an injection machine or press to force the softened plastic completely to fill the mould cavities.

Molecular Weight - The sum of the atomic weights of all atoms in a molecule.

Molecule - The smallest unit quantity of matter, which can exist by itself and retain all of the properties of the original substance.

Monomer - A relatively simple compound, usually containing carbon and of low molecular weight, which can react to form a polymer by combination with itself or with other similar molecules or compounds.

Notch Sensitivity - The extent to which the sensitivity of a material to fracture is increased by the presence of a surface notch or sudden change in section.

Nozzle - In injection moulding, the orifice containing plug at the end of the injection cylinder which contacts the mould sprue bushing and conducts the molten material into the mould.

Opaque - Not able to transmit light.

Pellets - Tablets or granules of uniform size, consisting of resins or mixtures of resins with compounding additives which have been prepared for Degradation of plastics due to the action of light.

Pigments - General term for all colorants, organic and inorganic, natural and synthetic, which are insoluble in the medium in which they are used.

Pit - An imperfection, a small crater in the surface of the plastic.

Plastic - A material that contains as an essential ingredient one or more organic polymeric substances of large molecular weight, is solid in its finished state, and, at some stage in its manufacture or processing into finished articles, can be shaped by flow.

Plastic Deformation - A change in dimensions of an object under load that is not recovered when the load is removed.

Plasticity - The ability of a material to withstand continuous and permanent deformation by stresses exceeding the yield value of the material without rupture.

Plasticizer - A substance or material incorporated in a material (usually a plastic or an elastomer) to increase its flexibility, workability or extensibility.

Poisson's Ratio - The constant relating the changes in dimensions, which occur when a material is stretched. It is obtained by dividing the change in width per unit length by the change in length per unit length.

Polyblend - A colloquial term used for physical mixtures of two or more polymers. Such blends usually yield products with favourable properties of both components, sometimes opening markets not available to either of the separate components. The term Alloy is sometimes used for such blends.

Polymer - (Synthetic) The product of a polymerization reaction. The product of polymerization of one monomer is called a homopolymer, monopolymer or simply a polymer, when two monomers are polymerized simultaneously the product is called a copolymer. The term terpolymer is sometimes used for polymerization products of three monomers.

Polymerization - A chemical reaction in which the molecules of a simple substance (monomer) are linked together to form large molecules whose molecular weight is a multiple of that of the monomer.

Polymer Structure - A general term referring to the relative positions, arrangement in space, and freedom of motion of atoms in a polymer molecule.

Purging - In extrusion or injection melding, the cleaning of one colour or type of material from the machine by forcing it out with the new colour or material to be used in subsequent production, or with another compatible purging material.

Raman Spectroscopy - Spectroscopic method to study vibrational, rotational and other low-frequency modes of a system. It relies on inelastic or Raman scattering of monochromatic light (from a laser in visible, NIR and NUV range). Laser interacts with photons in the system resulting in the laser energy shifted up or down.

Reinforced Plastic - A plastic composition in which fibrous reinforcements are imbedded, with strength properties greatly superior to those of the base resin.

Resin - (Synthetic) The term is use to designate any polymer that is a basic material for plastics.

Screw - In extrusion, the shaft provided with helical grooves which conveys the material from the hopper outlet through the barrel and forces it out through the die.

Solvents - Substances with the ability to dissolve other substances.

SPE - Abbreviation for the Society of Plastics Engineers.

Stabilizer - An agent used in compounding some plastics to assist in maintaining the physical and chemical properties of the compounded materials at suitable values throughout the processing and service life of the material and/or the parts made there from.

Strain - In tensile testing, the ratio of the elongation to the gage length of the test specimen, that is, the change in length per unit of original length.

Stress - The force producing or tending to produce deformation in a body measured by the force applied per unit area.

Stress-Crack - External or internal cracks in a plastic caused by tensile stresses less than that of its short-time mechanical strength. Note: The development of such cracks is frequently accelerated by the environment to which the plastic is exposed.

Stress-Strain Curve - The curve plotting the applied stress on a test specimen versus the corresponding strain. Stress can be applied through shear, compression, flexure, or tension.

Structural Foam - A term originally used for cellular thermoplastic articles with integral solid skins having high strength-to-weight ratios, but now sometimes also used for high density cellular plastics which are strong enough for structural applications.

Tensile Strength - The maximum tensile stress sustained by the specimen during a tension test

Thermoelasticity - Rubber-like elasticity exhibited by a rigid plastic resulting from an increase in temperature.

Thermoforming - The process of forming a thermoplastic sheet into a three-dimensional shape by clamping the sheet in a frame, heating it to tender it soft and flowable. Then applying differential pressure to make the sheet conform to the shape of a mould or die positioned below the frame.

Thermoplastics - Materials that become soft when heated and solid when cooled to room temperature. This softening and setting may be repeated many times.

Thermoplastic Elastomers - The family of polymers that resemble elastomers in that they can be repeatedly stretched without distortion of the unstressed part shape, but are true thermoplastics and thus do not require curing.

Thermotropic Additive - Additive, which shows a significant change of the refractive index at a certain temperature; thermotropic component for the production of �thermotropic materials with fixed domains�.

Thermosets - Materials that may not be reheated and softened again. Once the structural framework is set, these plastics cannot be reformed.

Tool - In injection melding, the term sometimes used to describe the mould.

Vicat Softening Temperature - The temperature at which a flat-ended needle will penetrate a thermoplastic specimen under specific conditions. (ASTM D-15225)

Virgin Material - Any plastic compound or resin that has not been subjected to use or processing other than that required for its original manufacture.

Viscoelasticity - This property, possessed by all plastics to some degree, dictates that while plastics have solid-like characteristics such as elasticity, strength and form-stability, they also have liquid-like characteristics such as flow depending on time, temperature, rate and amount of loading.

Viscosity - A measure of the resistance to flow due to internal friction when one layer of fluid is caused to move in relationship to another layer.

Weathering - A broad term encompassing exposure of plastics to solar or ultraviolet light, temperature, oxygen, humidity, rain, snow' wind, and air-borne biological and chemical agents.

Yellowness Index - A measure of the colour on the yellow scale.

Yield Point - In tensile testing, yield point is the first point on the stress-strain curve at which an increase in strain occurs without an increase in stress.

Yield Strength - The stress at which a material exhibits a specified limiting deviation from the proportionality of stress to strain.

Solar Thermal Systems


CFD Computational Fluid Dynamics
DHW Domestic hot water
FEA Finite element analyses
ICS Integral collector-storage system
PIV Particle Image Velocimetry
TES Thermal energy storage

Terms and Definitions

Absorber - component of a solar collector for absorbing radiant energy and transferring this energy as heat into a fluid*

Absorptance - ratio of the radiant flux absorbed by an element of a surface to that of the incident radiation*

Aperture area, collector - maximum projected area through which unconcentrated solar radiation enters the collector*

Auxiliary heat source - source of heat, other than solar, used to supplement the output provided by the solar heating system*

Azimuth angle, solar - projected angle between a straight line from the apparent position of the sun to the point of observation and due south (in the northern hemisphere) or due north (in the southern one), measured clockwise in the northern hemisphere and anticlockwise in the southern one, using the projections on the local horizontal plane. Note: The solar azimuth is negative in the morning (eastern directions), 0� to 180� at noon (depending on the relative values on solar declination and local latitude), and positive in the afternoon (western directions), over the whole globe. It diverges from the geographical azimuth, which is measured clockwise from due north, over the whole globe.*

Boiler - a complete unit to heat up a fluid, typically water. A boiler consists of a burner, a combustion unit and a heat exchanger to transfer the heat to the fluid. Alternatively electrical heating elements are used.

Burner � the device within a boiler managing the combustion of a fuel, e.g. a gas burner. The combustion chamber, the exhaust system and e.g. a water heat exchanger are not part of the burner.

Coating - see selective coating

Collector, solar (thermal) - see solar (thermal) collector

Collector cover, collector glazing - transparent (or translucent) material(s) that cover the absorber to reduce heat losses and provide weather protection*

Collector efficiency, solar - ratio of the energy removed by the heat transfer fluid over a specified time period, to the product of a defined collector area (gross, absorber or aperture) and the solar irradiation incident on the collector for the same period, under steady-state conditions*

Collector loop - circuit, including collectors, pump(s) or fan(s), pipework and heat exchanger(s) (if present), which is/are used to transfer heat from the collectors to a heat storage*

Combisystem � Short expression of a solar heating system for space heating and domestic hot water preparation

Drainback system - a solar heating system, in which, as a part of the normal working cycle, the heat transfer fluid is drained from the solar collector into a storage vessel when the pump is turned off, and refills the collector when the pump is turned on*

Drain-down system - a solar heating system, in which the heat transfer fluid is drained from the solar collector and run to waste, e.g. to prevent freezing*

Emittance - ratio of radiant exitance of a body to that of a full radiator (blackbody) at the same temperature*

Flat plate collector - non-concentrating solar collector in which the absorbing surface is essentially planar*

Flow temperature � temperature of a heat transfer fluid before (useful) energy is removed, typically temperature of the fluid leaving a heat source

Fluid temperature (inlet, outlet) - temperature of the heat transfer fluid at the accordant position of a component within the overall system

Forced circulation system - a solar heating system that utilizes (a) pump(s) or (a) fan(s) to circulate a heat transfer fluid through the collector(s)*

Geomembrane - impermeable sheets produced from polymeric materials

Glazing - see collector cover, collector glazing

Global (solar) radiation - hemispherical solar radiation on a horizontal plane*

Heat transfer fluid, heat carrier - fluid that is used to transfer thermal energy between components in a system, e.g. solar heating system*

(Heat) store - a device designed to maintain a shift between heat production, e.g. by a solar heating system or a gas boiler and the heat consumption by temporarily storing heat for later supply

Heating system - system for the production of heat for different purposes

Hemispherical (solar) radiation - solar radiation on a plane surface received from a solid angle of 2π sr (from the hemisphere above); Note (1): The tilt angle and the azimuth of the surface should be specified, e.g. horizontal. (2) Hemispherical solar radiation is composed of direct solar radiation and diffuse solar radiation.*

High flow technology - a way of designing and operating a solar heating system, in which the mass flow rate in the collector loop is higher than approx. 20 l/(h m2 collector area)

Irradiance - power density of radiation incident on a surface, i.e. the quotient of the radiant flux incident on the surface and the area of that surface, or the rate at which radiant energy is incident on a surface, per unit area of that surface. Irradiance is normally expressed in [W/m2]*

Irradiation - the incident energy per unit area of a surface, found by integration of irradiance over a special time interval, often an hour or a day. Irradiation is normally expressed in [MJ/m2] *

Integral collector-storage system (ICS) - solar heating system in which the solar collector also functions as a heat (water) storage *

Liner � (geo)membrane that serves as an impermeable barrier

Load - heat supplied to the user, e.g. in form of space heating or domestic hot water*

Low flow technology - a way of designing and operating a solar heating system, in which the mass flow rate in the collector loop is significantly lower than approx. 20 l/(h m2 collector area)

Open system - system in which the heat transfer fluid is in (extensive) contact with the atmosphere*, see vented systems

Parasitic energy - electricity consumed by pumps, fans and control equipment in a solar heating system*

Photovoltaic (PV) cell - semiconductor device that converts radiant energy (usually solar radiation) into electrical energy by means of the photovoltaic effect

Pool absorber - usually a solar collector without transparent cover over the absorber

Primary energy - energy that has not undergone any sort of conversion, e.g. crude oil

Radiation, global (solar) - see global (solar) radiation

Reflectance - ratio of the radiant flux reflected from a surface to that of the incident radiation*

Return temperature (of a heat transfer fluid) - temperature of the fluid after (useful) energy has been removed, typically temperature of the fluid entering a heat source

Thermal energy storage (TES) � TES can refer to different technologies that store thermal energy in a reservoir for later utilization

Seasonal thermal energy storage � see TES, storage of thermal energy between seasons, e.g. from summer to winter

Secondary energy - produced by the conversion of primary energy, e.g. electricity, oil or gas to be used for heating purposes

Service time - of a product is its expected lifetime or the expected period of use in service. It is the time that any manufactured product can be expected to be 'serviceable'.

Selective surface - surface whose optical properties of reflectance, absorptance, transmittance and emittance are wavelength dependent*

Solar combisystem - Solar heating system for space heating and domestic hot water preparation

Solar contribution - energy supplied by the solar part of a solar heating system*

Solar fraction - energy supplied by the solar part of a solar heating system divided by the total system load*

Solar heating system - system composed of solar collectors and other components to supply heat for different purposes*

Solar loop - see collector loop

Solar-plus-supplementary system - a solar heating system that utilizes both, solar and auxiliary energy source(s) in an integrated way. A solar-plus supplementary system is able to provide a specified heating service independently of solar energy availability.*

Solar radiation, global - see global (solar) radiation

Solar radiation, hemispherical - see hemispherical (solar) radiation

Solar (thermal) collector - a device designed to absorb solar radiation and to transfer the thermal energy so produced to a fluid passing through it*

Space heating system - a heating system providing heat to maintain thermal comfort in a building

Stagnation - status of a collector or solar heating system when no heat is removed by a heat transfer fluid*

Steady state - status of a collector, when the rate of heat removal including heat losses is equal to the rate of solar energy input*

Storage, heat - see thermal energy storage

Store, heat - see heat store

Stratifier, stratifying unit - a device for enhancing stratification in the heat store

Thermal Energy Storage - a device to store thermal energy

Thermal (solar) collector - see solar thermal collector

Thermosiphon system - a solar heating system that utilizes only density changes in the heat transfer fluid to achieve circulation between collector and storage device or collector and heat exchanger(s)*

Tilt angle, collector - angle between the horizontal plane and the plane of the specified surface*

Transmittance - ratio of the radiant flux passing through a body to that of the incident radiation*

Useful energy - the energy drawn by consumers from their own appliances after its conversion (i.e. in its final utilisation); examples: electric light, mechanical energy, comfort heat, domestic hot water

Vented system - system in which contact between the heat transfer fluid and the atmosphere is restricted either to the free surface of the feed-and-expansion cistern or to an open vent-pipe only*

*According to DIN EN ISO 9488