polymer discovery system

8/6/2019 Polymer Discovery System

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Polymer Discovery System

::: Intelligence in Rheometry

Today, polymers are among the most important materials in

existence as the properties of polymers can be adapted in a

very wide range to fit the field of application. Some polymers

are hard and brittle or tough and shock-resistant, while

other polymers are soft and flexible. The manufacturing and

characterization of polymers is therefore the focus of activity for

numerous industrial companies and research institutes.

IntroductionPlastics are organic or semi-organic substances with a high

molecular weight. The length of the molecular chains and the

entanglement between them are decisive parameters which

influence the properties of the material. Many of the relevant

properties can be characterized using rheological tests.

Polymers have complex chemical and morphological structures

and a wide range of variation in the composition and possibility

of modifying the material. Therefore they show complex

behaviors which need to be taken into consideration whenusing or manufacturing these materials, e.g. the viscoelasticity,

non-Newtonian flow behavior, anisotropy (dependent on

orientation or modification), complex aging behavior and much

more. Describing the properties of polymers requires versatile

procedures in order to obtain the needed information.

Many methods are used for processing and manufacturing

plastics. The majority are forming and reforming procedures

(compression molding, calendering, film extrusion, blow &

injection molding, etc.). Optimizating these procedures and

their quality control is therefore extremely important in the

production of plastics.

Source: accelrys

Models of oxygen and water molecules in an amorphous polymer matrix.


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Material characterization

Molar Mass DistributionRecently, mathematical models have been developed which

allow the determination of the molar mass distribution via

rheological measurement.

Correlations to molar mass distribution or material branching

can be seen in the viscoelastic behavior, which influence

both, the manufacturing process and the properties of

the end product. The molar mass is the most important

structural parameter which affects the flow behavior of

polymers.

Process SimulationCorrelation to manufacturing conditionsMeasurements at low shear rates are mainly used for

analyzing manufacturing problems. Whereas manufacturing

processes such as extrusion or injection molding occur

at high shear rates, differences between the materials are

usually seen at low shear rates. Manufacturing problems

often occur at low shear rates, e.g. delayed die swell with

extrusion or delay due to irregular relaxation during the

cooling phase of injection molded parts. Polymer melts

show pronounced shear thinning behavior, i.e. the viscosity

decreases with increasing shear rate. Flow curves are

important for the manufacturing of polymers to determine the

energy required for the process. Oscillatory measurements

also reveal information about the elasticity of the melt, which

can be correlated with die swell.

The viscosity curve becomes flatter with decreasing shear

rate and the polymer melt shows Newtonian behavior with

a constant viscosity. This region at low shear rates is called

the terminal relaxation zone or the 1st newtonian plateau.

The constant viscosity in this range is called the zero-shear

viscosity 0 and represents an important temperature dependent

material parameter. For most technical polymers, the zero-shear

viscosity is directly proportional to the average molar mass.

The rheological measurement therefore clearly shows small

differences in the molar mass.

At a constant average molar mass, the energy required for shear

thinning in the manufacturing process can be correlated with

the molar mass distribution. Polymers with a wide molar mass

distribution have more of a tendency to shear thinning, even at

low shear rates, than more narrowly distributed materials with

the same average molar mass. Broadening the molar massdistribution aids extrusion and shaping. This means, for example,

that the surface quality of molded plastic parts can be improved

by varying the distribution width. The width of the molar mass

distribution correlates with the cross-over point between the

storage modulus G and the loss modulus G in a frequency

sweep.

Rheological Tests on Polymers

G'

G''

Angular Frequency

> narrow

lower averagemolar mass (MW)

longer / branchedmolecules

GX, X


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BranchingThe number, length and mobility of side chains influence the

rheological properties. If the side chains are not very long,

this leads to increased viscosity at low shear rates and more

pronounced shear thinning compared to the corresponding

linear polymer.

If a polymer has long-chain branching, it will display low

viscosity at low shear rates. The extent of branching can

therefore be used to control manufacturing and product

characteristics.

FillersFillers also influence the manufacturing process and the

properties of the end product. Important factors are size,

form and concentration of the fillers and the interactions

between the particles. Fillers usually lead to an increase in

the melting viscosity and a reduction of die swell. From a

rheological standpoint an increasing filler content results in asmaller so-called linear visco-elastic (LVE) range, which can

be determined in an amplitude or strain sweep.

Measurements on solidsWith the appropriate accessories, a rheometer can be used

to perform dynamic mechanical thermal analysis (DMTA)

on solid samples by measuring the samples in torsion.

The solid properties are usually determined as a function

of the temperature and the results give insight into the

morphological properties and behavior of the polymer when

in use. Measurement of the glass transition temperature

(Tg) and storage modulus (G) below the glass transition

temperature gives information on the maximum service

temperature and the impact strength, embrittlement and

stiffness of the material. For crystalline or partially-crystalline

polymers the melting temperature (Tm) is another important

material parameter accessible with such a DMTA test.

Conversion and analysis methods


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Applications

Fig. 1: FLOW AND VISCOSITY CURVE or

how to get information about the flowability of athermoplastic:Flow and viscosity curves give information about the flowability of

thermoplastics under different shear and process conditions. The zero-

shear viscosity 0 at low shear rates is an important material property

and is directly proportional to the average molar mass Mw. In order to

determine a viscosity curve over a broad range of shear rates a master

curve can be constructed using time temperature superposition in

combination with the conversion method according to Cox Merz. In

addition, conversions from transient tests and a direct measurement

with controlled shear rate provides the whole spectrum of shear rates.

Powerful regression methods may help to calculate the zero-shear

viscosity 0 and the infinite-shear viscosity inf in a shear range where

all the molecules are totally disentangled and oriented.

Fig. 3: CROSS OVER POINT Gx or how tocompare the molar mass of thermoplastics within10 minutes:Within 10 minutes, the molecular structure can be analyzed with

respect to the average molar mass Mw and the molar mass distribution

MMD. A powerful and model free method is given for a relative

comparison of thermoplastics. A qualitative measure for the average

molar mass is expressed by the horizontal position of the cross-over

point Gx while the vertical position of Gx indicates the MMD. In addition

the degree of branching can lead to a horizontal shift of Gx while

comparing polymers of the same type.

Fig. 2: TIME TEMPERATURE SUPERPOSITIONTTS or looking deep into the macromolecularstructure of a polymer melt:The Dynamic mechanical analysis (DMA) in torsion, determined

via time temperature superposition TTS, provides shear and

time dependent information about the viscoelastic properties of

a material. Predictions regarding "Die Swell are possible. All the

information about the polymeric macro-structure and its short

and long term behavior is already included in the "Master Curve.

Comparative average molar mass and molar mass distribution,

as well as the calculation of their absolute values, are supported.

Conversions into transient and oscillatory material functions are

applicable.


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Fig. 4: MOLAR MASS CALCULATION a method

used not only for short or narrow distributedpolymer melts:Processability and product performance depend very much on the

molecular structure of the polymer melt, so it is important to analyze

thermoplastics with respect to their molecular structure. A rheological

dynamic mechanical measurement (DMA) in combination with the

latest sophisticated MMD analysis methods has major advantages

and is still easy to use. The thermoplastic material can be measured

as molten material and does not need to be diluted in an aggressive

solvent. The method has no upper limits regarding length and

distribution of the molecules; rather there are advantages due to

the higher sensitivity with increasing average molar mass Mw. Input

data for the method include a frequency sweep showing zero-shear

viscosity and cross-over point Gx.

Fig. 6: TRANSIENT TEST TYPES (Creep, StressRelaxation and Stress Growth Tests) find outmore about the time response of your material:Step stress (creep & recovery), step strain (stress relaxation) and

step rate (stress growth / start up flow) experiments are typically

performed to measure the time (transient) response of a material to

a given constant shear stress, shear strain or shear rate. Analysis

methods enable the calculation of important material constants such

as zero-shear viscosity, plateau modulus, creep compliance and the

conversion from the transient material functions to oscillatory material

functions - G(), G(). In Figure 6, a stress growth experiment is

presented.

Fig. 5: DYNAMIC MECHANICAL THERMALANALYSIS (DMTA) in TORSION or how todetermine phase transitions of thermoplastics,thermosets and elastomers:This test provides the essential information about the materials

phase transitions. Glass transition (Tg), melting (Tm) and

crystallization temperature (Tc) can be determined with high

precision using the environmental chamber CTD 600. Information

about the degree of crystallinity or cross-linking is expressed in the

slope of the material functions G and G. With the film and fibre

fixture, DMA and DMTA tests in tension can be performed even on

soft polymeric films and fibres. In figure 5, a multiwave experiment

is presented with the determination of the glass transition

temperature, expressed as the maximum in tan(). As can be seen,

Tg is a function of the applied frequency.


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Physica rheometers for polymer testing

Electrical Temperature Device P-ETD 4004 Electrical resistance heating

4 Specially suited for samples which are measured at high temperatures

4Very rapid heating rates

4The special design enables water cooling (liquid circulator) as well as

electrical heating

4 Use of liquid nitrogen for temperatures as low as -130 C

Electrical Temperature Device H-ETD 4004 Electrically heated hood

4Active heating of the sample area and measuring system

4An essential accessory for preventing temperature gradients in the

sample

4The hood can be purged with inert gas to prevent oxidation or otherchemical reactions

Convection Temperature Device CTD 6004 Extremely small temperature gradients

4 No temperature overshoots

4 Measured temperature always represents the sample temperature

4 No ice formation at low temperatures

4 Compact, robust design

4Automatic adjustment of liquid nitrogen consumption

4 Easy to open, good sample access

4 Sample observation during the measurement is possible

4 Chamber can be touched at all test temperatures

4Wide range of accessories: torsion and film/fibre tool, UV-option,

disposable plates, etc.

Environmental SystemsSince temperature has a great influence on the rheological

behavior of all polymeric samples, precise temperature

control is crucial to obtaining reliable rheological data.

However, in practical tests, inaccurate temperature control

is still responsible for a large number of measurement

uncertainties and errors. To address these issues, our

engineers have taken great care to develop various

temperature control systems based on different principles.

These systems fulfill the requirement of accurate temperature

control in all respects and are still commercially affordable,

putting Anton Paar in the lead position with respect to

temperature control in rheology. Numerous patents and

scientific reports about the performance of the various

environmental system have been published. Some key

features include the broadest temperature range available

(-150 C to 1000 C) for a standard rheometer, proof of

performance, i.e. as results of temperature gradient testing,

and the availability of certified temperature sensors which

allow software controlled automatic temperature calibration in

a broad temperature range.


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Included:

Trimming tool for easy

sample trimming on

all sides

Included:

Filling ring for melting

and molding polymer

granuls

Simple to remove

before measurement

Included:

Scraper for fast and

effective cleaning

Option:

Stamping press

This press enables the

production of sample

discs in a thickness

up to 2 mm and in

diameters of 25, 12

and 8 mm.

Helpfull accessories for the CTD 600

Systems Polymer Discovery System Polymer Melt Rheometer

Rheometer Physica MCR Series incl. Toolmaster Physica MCR Series incl. Toolmaster

Temp.-Control System:

Convection Temperature Control Device CTD 600

incl. accessories for polymer handling

Temperature Calibration Sensor CS/CTD

Electrically Heated Temperature Device ETD 400

Measuring System:

Measuring Plate PP25

Lower Measuring Plate PP25 with built-in

temperature probe

Measuring Plate PP25

Software:

RheoPlus SoftwareRotation and Oscillation

DSO Direct Strain Oscillation

Polymer Analysis Package consisting of:Master curves, Relaxation Time Spectra,Retardation Time Spectra,Molar Mass Distribution

RheoPlus SoftwareRotation and Oscillation

Options:

Solid Torsion Bar Fixture STBF

Film and Fibre Fixture

Tool for Extensional Rheology

Low Temperature Option (LN2 Evaporation Unit EVU), TruGap

DSO Direct Strain Oscillation

Polymer Analysis Package consisting of:

Master curves, Relaxation Time Spectra,

Retardation Time Spectra, Molar MassDistribution

Temperature Calibration Sensor CS/CTD


8/802/04 B61IP08-B

Specifications

subject to change

without notice

Fotos: Croce & Wir

Anton PaarGmbH

Anton-Paar-Str. 20

A-8054 Graz

Austria - Europe

Tel.: +43 (0)316 257-0

Fax: +43 (0)316 257 257

E-mail: [email protected]

Web: www.anton-paar.com

International Product

Management:

Anton Paar Germany GmbH

Helmuth-Hirth-Str. 6

D-73760 OstfildernGermany - Europe

Tel.: +49 (0)711 72091-0

Fax: +49 (0)711 72091-630

E-mail: [email protected]

Web: www.anton-paar.com

Instruments for:

Density and concentration

measurement

Rheometry and viscometry

Sample preparation

Colloid science

Microhardness testing

X-ray structure analysis

CO2 measurement

High-precision temperature

measurement

polymer discovery system

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