ORIGINAL RESEARCH

Compact and flexible optical sensor designedfor on-line monitoring

Laurent Jourdainne & Rodrigue Matadi Boumbimba &

Badi Triki & Michel Bouquey & René Muller &

Pascal Hébraud & Pierre Pfeiffer

Received: 5 May 2010 /Accepted: 4 December 2010 /Published online: 18 December 2010# Springer-Verlag France 2010

Abstract A new on line optical sensor based on lightscattering dedicated to real-time monitoring during processingof polymers blends and polymers nanocomposites has beendeveloped. The sensor is designed to monitor the quality of apolymer melt or of a dispersion of nanofillers in a polymericmatrix during the process of extrusion. This sensor presentsthree openings: two for light sensor setups (one for transmis-sion measurements and the other for 90°-scattered lightmeasurements) and one for the incident laser beam. Theexperimental validation of this optical sensor has been realizedon two materials: poly(methyl methacrylate) (PMMA) and onthe nanocomposites obtained by the melt mixing of thispolymer matrix with modified montmorillonite (MMT) clays.Experimental results proved the good results in terms of signalrepeatability and sensitivity to organoclay particle concentra-tion and structures of nanocomposites respectively.

Keywords A. nanoclays . A. nano composites . D. opticalmeasurements . E. extrusion

Introduction

Polymer/ clay nanocomposites are a new class of materials inwhich inorganic particles with at least one nanoscaledimension are dispersed in the organic polymer matrix.Because of their nanoscale size, nanocomposites exhibit alarge spectrum of improved properties compared to micro-composites or polymer without any filler [1–4]. In generalthese kinds of materials have superior mechanical properties[2], thermal stability [3], flame retardant and gas barrierproperties [5]. This improvement in properties is caused bydifferent parameters, such as quality of clay dispersion in thematrix, intercalation of polymers chains into the interlamellarspacing [6], and the exfoliation of clay platelets [7].

To successfuly fabricate polymer/clay nanocomposites,the inherent immiscibility between most organic polymersand inorganic clay fillers must be overcome [8]. Naturalclays such as montmorillonite (MMT) may be organicallymodified to make the silicate sheets more organophilic andcompatible with the polymer [8]. Alkylammonium cationsare commonly used to modify the surface of clay particles[9]. This surface modifiers decrease the surface energy [9,10] of the silicate platelets, and increase the basal spacingbetween the layers [9, 10], which can lead to easypenetration of polymeric chains.

One of the most commonly used methods for thepreparation of polymer-clay nanocomposites is melt inter-calation [11]. This method involves the thermal treatment,in most cases under shear, of polymer/clay mixtures attemperatures above the polymer softening point [11]. Thistechnique is environmentally safe due to the absence oforganic solvents, and is compatible with current industrialprocesses, such as extrusion and injection molding [12, 13].

Various methods or tools are needed to characterize thestructure of the nanocomposites and to estimate the degree

L. Jourdainne : R. Matadi Boumbimba :B. Triki :M. Bouquey :R. Muller (*)Laboratoire d’Ingénierie des Polymères pour les HautesTechnologies, ECPM-LIPHT, University of Strasbourg,25 rue Becquerel,67087 Strasbourg, Francee-mail: rene.muller@unistra.fr

P. HébraudInstitut de Physique et Chimie des Matériaux de Strasbourg,CNRS-UDS, University of Stasbourg,23 rue du Loess,67034 Strasbourg, France

P. PfeifferLaboratoire des Systèmes Photoniques, University of Strasbourg,Boulevard Sébastien Brant, BP 10413, 67412 Strasbourg,France

Int J Mater Form (2012) 5:1–9DOI 10.1007/s12289-010-1015-6

of exfoliation of clay particles. Among these methods wecan mention transmission electron microscopy (TEM), Xray diffraction (XRD) [9], and melt rheology which permitto identify the intercalated-exfoliated type of structure andto examine the ability of polymer to enhance the nano-dispersion of silicate layers in the matrix. The maindrawback of all these characterisation methods is that theyare carried out off-line. Off-line analysis implies longfeedback times to adjust the processing parameters of aproduction line. The longer the feedback time, the larger arethe waste of material and energy. Several in-line methods tomonitor the extrusion process have been already developedand reported in the literature. Fischer et al. [14] showed thatit was possible to determine the polyethylene / polystyreneblend composition by NIR spectroscopy and ultrasonicmeasurements. The precision of NIR spectroscopy for thedetermination of the composition of polymer mixtures is ofabout 1%. In another paper, Fischer et al. [15] comparedvarious in-line spectroscopic methods like near-infrared,Raman and ultrasonic spectroscopy to monitor the compo-sition of polypropylene melts in the presence of Irganox .The authors assessed the accuracy of spectroscopic methodsto determine the concentration of additives in real-time, andconfirmed the advantages of ultrasonic spectroscopy com-pared to the others characterization tools, with respect to itsrobustness and low cost.

To improve the process of formulation of nanocompositematerials, it seems therefore necessary to develop newmethods and new characterization tools. In-line or on-linesensors are the main investigated tools to reduce thefeedback time of the manufacturing process of nano-composites. When the characterisation of the melt takesplace inside the extruder, the method is called in-line. Dueto the proximity of the screws, the lack of space and thedifficulty to install a sensor in a pressurized zone of theextruder, in-line methods are not always possible. For thisreason on-line methods are often preferred: a small sampleof the melt is taken through a by-pass, to a zone where it iseasier to install a sensor, and to analyze the material.

The design of the sensor is strongly dependent to thechoice of an in-line or on-line system. Both systems haveadvantages and drawbacks. In our case the on-line solutionwas chosen for several reasons. The first one is that thedesign of an in-line setup would be too much dependent onthe type of the extruder head or line. As these are differentfor each type of extruder, the sensor would necessarily bededicated to a specific type of extruder. The second reasonis related to the flow of material close to the measurementzone in the sensor. For an in-line device, the flow velocityof the material may be very high and require very high dataacquisition frequencies for the light intensity measure-ments. On the other hand, the thickness of the polymerinside the head of an extruder can be large enough so that it

could completely absorb the laser light and no signal couldbe detected. These reasons lead us to design an on-linesetup, where a fraction of the extruded material iscontinuously taken through a by-pass.

Few experiments based on the interaction between thevisible light and organoclay nanocomposites have beenreported in the literature. Small angle laser light scatteringexperiments (SALLS) were realized to monitor the effect ofclay addition on the critical temperature of phase separationin a polymer / polymer blend. Light scattering patternsobtained for neat polymer blends were compared to thoseobtained for polymer blends with clay particles underdifferent temperatures [16]. The same kind of experimentswere used to monitor the influence of organoclay on thephase separation in a polymer / epoxy mixture [17]. Thecontrol of the optical quality is representative of the clayparticle dispersion. Wang et al. carried out some measure-ments on transmitted light by a BR / clay nanocompositeand thus controlled the dispersion of particles [18]. In aprevious paper, we characterized the progress of dispersionof montmorillonite in poly(lactic acid) by comparingrheological behaviour and light attenuation [19]. A com-parison between in-line dielectric spectroscopy and in-lineoptical measurements was published by Bur et al. [20, 21].These two sensors were integrated at the exit of a twin-screw extruder and enabled a real-time monitoring of theexfoliation. According to the best of our knowledge, theseresults are the only ones which associate an opticalcharacterization method and an in-line or on- line designof the sensor.

The aim of the present paper is first to describe thepreliminary results which lead us to propose an alternativemethod for the real-time characterization of polymer blendsor composites during extrusion, and secondly to describe afirst prototype of the sensor. Our sensor will be based on anoptical characterization and for the first time, the extrudedmaterial will be characterized both by transmitted andscattered light.

Before developing the sensor itself, various preliminaryexperiments were realized in order to determine thetechnical requirements of an on-line optical sensor. Thefirst experiments were carried out to determine the mostsuitable range of scattering angles where the scatteredintensity is sensitive to the concentration and shape of theparticles. A control of the dependence of transmitted andscattered light to the size distribution of the particles wasalso realized. A detailed description of the first prototype ofthe on-line sensor and validation experiments are thenpresented. Final aim of the present work was to provide anapparatus able to realize a real-time control quality ofpolymer melts in an industrial environment. The sensorshould therefore be as small as possible, not too expensive,and suitable for a large variety of extruders.

2 Int J Mater Form (2012) 5:1–9

Materials and apparatus

Models samples for the determination of scattering vectorrange

The aim of the preliminary experiments is to determine therange of scattering angles in which the measurementsshould be realized. For this purpose, off-line tests wererealized on a mixture of spherical silica particles and anaqueous solution of poly (ethylene oxide) (POE) (Mv≈106 g/mol, Sigma Aldrich, St. Quentin, Fallavier, France).The POE solution was obtained by dissolving 5 g ofpolymer in 130 g of water at 80°C under stirring. Itsviscosity was around 2,500 mPa.s (viscometer DV-II+,Brookfield, Middleboro, MA, USA) at room temperature tolimit the sedimentation of particles during the time ofoptical measurements. The silica particles used for experi-ments had a diameter of 100 or 440 nm. The tests weremade at different concentrations of silica particles rangingfrom 0.5 to 5 wt%.

Materials and melt processing for the validation of the oneline sensor

The poly(methyl methacrylate) used in this study wassupplied by Unigel Plasticos, sa Bernado do campo Brazil.The two organoclay used as fillers, were Cloisite 20A(C20A) (MMT-alk: modified by dimethyl-2 ethylhexyl(hydrogenated tallow alkyl) ammonium, and Cloisite 30B(C30B) (MMT-(OH)2 , modified by methyl bis(2-hydrox-yethyl) hydrogenated tallow alkyl) ammonium- cation),which contained 21 and 26 wt% of organic modifiers,respectively. More details about the products and nano-composites preparation can be found in [22]. Since a twin-screw extruder was not available for this first series of teststhe optical sensor was first mounted on a single screwextruder (Fairex (Villeparisis, France) Dia. 30–24 L / Dcompact C2). Since this extruder did not allow a goodmixing, we first prepared the organoclay nanocompositeson a BUSS Kneader, and then introduced pellets of theobtained material into the single-screw extruder for theoptical characterization.

The morphology of the two obtained nanocompositeswas investigated in a previous study [22]. It was shown thatthey presented a good dispersion of organoclay in thePMMA matrix. In addition, it was found that the organo-clay nanocomposite PMMA/C30B presented an exfoliatedmorphology, whereas the organoclay nanocompositePMMA/C20A presented an intercalated morphology. Aftermelt mixing on the BUSS Kneader, the obtained pelletswere dried and then introduced into the single screwextruder. A small fraction of the melt is taken through aby-pass mounted just before the die of the single screw

extruder for the optical analysis using the sensor developedin this study. The working temperature was 200°C, dataacquisition rate was about 10 Hz, and the screw speed ofthe extruder was fixed at 20 Rpm. A typical test consistsfirst in extruding pure PMMA during 200 s and thenemptied the hopper and feeding it again with the nano-composite pellets. The Estimated time for the material toarrive from the hopper to the sensor window is about 390 s.

Description of the off-line setup

An off-line setup was used to measure scattered lightintensity at a chosen angle. Figure 1 shows a view of theoff-line setup along the vertical axis where the samples areplaced in a transparent cylindrical cell. The incident lightbeam of a HeNe Laser (4 mW at 1=632.8 nm, polarized,Uniphase, model 1107p) was split by a polarized beams-plitter which reflects the vertical component and transmitsthe horizontal component of the linearly polarized incidentlight. As a consequence, the polarization of the beam isparallel to the incident plane, which contains the incidentand scattered light beams, at the level of the cell. Thediameter of the laser beam is equal to 2 mm. A siliconphotodiode (13DAH005, f=1 mm, CVI Melles Griot,Voisins le Bretonneaux, France) is used to continuouslymonitor the intensity of the vertical component. Thephotodiode is connected to a data acquisition module(USB-6009, National Instrument, Nanterre, France).

An avalanche photodiode (APD) (S2383 Si-APD, f=1 mm, Hamamatsu, Massy, France) is used as the scatteredlight detector, and connected to a multimeter (Fluke 45,Roissy, France). Different neutral density filters reduce thelaser intensity to avoid saturation. The APD is mounted ona step-by-step motor (M-URM88CCHL, Newport, Evry,France) used to displace the photodectector with a precisionof 0.001° on a range of 300° around the sample. It is drivenby a microcontroller (Newport MM4006).

Fig. 1 Light scattering setup. Samples are contained in a 4 mm-diameter cell

Int J Mater Form (2012) 5:1–9 3

A GPIB interface (National Instrument, GPIB-USB-HS)is used for the communication between the devices and acomputer. A virtual instrument was developed with Lab-view (National Instrument).

Description of the on-line sensor

Figure 2 shows a cross section of the sensor with theconnection of optical fibres for light emission and lightdetection. One can notice that there are three openings:, twofor light sensor setups, one for transmission measurementsand the other for 90°-scattered light measurements, and onefor the incident laser beam (on the left part of the drawing).The design of the openings in the flow channel, which isonly 6 mm in diameter, was a source of problems for thetightness of the system. A solution was found by pasting acylindrical quartz window (thickness of 2 mm, diameter of4 mm) in a conical-ended holder, which ensures thetightness thanks to the pressure exerted by the collimatorand lens holder. As a matter of fact, these parts are screwedin the sensor and press the window holders. Quartzwindows were chosen for their optical quality, mechanicaland thermal resistance. At one end of the holders part, alens can be glued (PCX12, Edmund Optics), and at theother side the part is designed to receive either sma-connection fibres, or a collimator.

The light source which was used is a fiberred laser diodefrom Opton Laser International (model PL63C0016FCA -0-0-01). The emitted wavelength is about 630 nm for amaximal power of 1 mW. The laser diode is temperature-and power-controlled. These regulations are carried out bya diode controller (pro 8000 and ITC 8022 by Thorlabs).For the temperature control, a Peltier component is pastedon the laser diode. The temperature- is controlled so that thedeviations are less than 0.01°C per hour. The power controlallows to limit the deviations to less than 0.001 mW perhour. The laser diode is fibered, so that the light is guideduntil a collimator (F220FC-B, Thorlabs), which transformthe divergent output beam into a parallel beam. At the other

side of the collimator holder, the convergent lens has beenchosen with a focal length which enables to focus the laserbeam on the axis of the cylinder. The multi-mode opticalfibres were specifically designed for this application (Fiber-guide). Gold-coated fibres were chosen for their better hightemperature resistance, up to 700°C. The core is about200 μm, the clad is 220 μm, and the numerical aperture isof 0.22.

Strong pressures (5 MPa) and high temperature until520°K will be the permanent environmental conditions.The various characteristics of the materials to be analyzedimpose the sensor’s ability to work in a wide range of flowrates, melt viscosities and clay particles concentrations.

The overall dimensions of our optical sensor are close tothat of a pressure sensor as shown in Fig. 3. Reduceddimensions and easy connection to a processing machineare important criteria for a sensor to be used in an industrialenvironment. Further desired characteristics are robustnessand easiness of cleaning.

To make the sensor as adaptable as possible, Dynisco-type connections were chosen, since most extruders areequipped with pressure transducers and Dyisco-type fit-tings. The optical sensor is thus designed to be mounted inplace of a pressure sensor. A further condition comes fromthe fact that the sensor is designed as a by-pass and thatsome amount of material is continuously flowing throughit. This material should flow downwards when it comes outof the sensor, which requires the possibility to fix theangular orientation of the sensor.

This finally leads to two independent mechanical parts: atube with a dynisco fitting acting as a connection betweenthe extruder and the sensor. The length of this part isdefined in function of the available space around theextruder. The second part is the main part of the sensorwhich contains the optical components.

All mechanical parts are made of 40CMD8 steel. AllSurfaces were treated by nitruration, which allowed to

Incident light Transmitted light

Scattered light

Optical fibre connector

Collimator fibre connector

Lens

Quartz window

Fig. 2 Cross section of the on-line sensorFig. 3 Comparison between the size of a commercial pressure sensorand the size of our pressure sensor

4 Int J Mater Form (2012) 5:1–9

avoid light reflexions which could have affected thetransmission and scattering measurements.

Figure 4 is a schematical view of the sensor duringoperation. The flow rate of material through the sensor canbe adjusted by the position of the cone-ended screw on theleft part of the figure.

Results and discussion

Determination of the scattering vector range usingthe off-line setup

The aim of the experiments made with the off-line setup isto find the angles where the scattering measurements can berealized. As mentioned above, different suspensions ofparticles in POE solution were prepared for this purpose. Ina first step, we have measured the light intensity as afunction of scattering angle at a given particle concentra-tion. Then, some experiments were carried out at 0°corresponding to the transmitted light. Finally the influenceof the size of particles were carried out at fixed angle andparticle concentration the Figs. 5 and 6 show the lightintensity as a function of scattering angle for variousconcentrations of silica particles with a diameter of 100 nm.According to these results, there is no significant scatteringpeak observable at given angles. The setup is sensitive tothe concentration above q=15 μm−1 (θ=50°). Above q=17 μm−1(θ=68°), the intensity is nearly independent of thescattering vector and is almost completely constant for q=23 μm−1 (θ=100°). This behaviour is representative ofmultiple scattering. The range of scattering angles around100° seems interesting for characterization because smallerrors on the detector position will not result in largeuncertainties on light intensity like it would be the case formeasurements at smaller angles (q<8 μm−1, θ<30°), wherethe cylindrical geometry of the cell seems to create somemisleading interferences.

As reported in Figs. 5 and 6, the best compromise tocombine multiple scattering behaviour and easiness ofmanufacturing is a light scattering angle of 90°. Figure 7shows the transmitted θ=0° and scattered θ=90° (q=21 μm−1) light intensities at different particle concentra-tions. As expected the scattered light intensity increaseswith increasing particle concentration, whereas at the sametime the transmitted light intensity decreases.

The third series of experiments concerns the estimation ofthe sensitivity of the sensor to the size of particles at constantvolume fraction. Silica particles of 100 and 440 nm weremixed together at different relative concentrations but bykeeping constant the overall mass fraction of particles in thesuspension at a value of 0,5%. p represents the weight percentof large particles in the solid phase. This mass fraction waschosen because of the good sensitivity of the setup in this

Flow regulation system

Transmitted light

Flow of the composite Incident light

Connection to extension piece withdynisco connector

Fig. 4 Technical drawing of the matter rate regulation system. Darkarrows represent the flow of matter, the orange part is the regulationsystem

Fig. 5 Light intensities measured for several samples (POE matrix,various concentrations of 100 nm-diameter silica particles)

15 20 250.0

0.5

1.0

1.5

2.0

2.5

Sca

ttere

d lig

ht in

tens

ity (

U. A

.)

q (µm-1)

5% 4% 3% 2% 1% 0.5%

Fig. 6 Light intensities measured for several samples (POE matrix,various concentrations of 100 nm-diameter silica particles). q isdefined by q ¼ 4p

l ns sinq2

� �where λ=0.6328 μm, ns=1.52 and θ is the

scattering angle

Int J Mater Form (2012) 5:1–9 5

range. Figure 8 represents light intensities measured at 0° and90° versus p. The results seem more sensitive to the sizedistribution at small values of p (<0.50), so that the.Sensitivity to the composition of the solid phase is thehighest in the case of a small proportion of large particles.The setup is thus able to discriminate small to largerparticles, under specific conditions.

A final series of experiments concerned the repeatability ofresults for: various positions of the incident light beam withinthe same sample and the control of the stability of incidentlight intensity. The HeNe Laser beam we used exhibitsintensity variations below 5% after one hour (data not shown).Transmitted or scattered light measured for different positionsof the incident beamwithin a homogeneous samplemadewithPOE and silica particles (0.5% mass fraction, 100 nm-diameter) exhibited variations below 5%.

On-line sensor validation

Figures 9 and 10 show respectively the transmitted andscattered light intensity as a function of experimental timefor the pristine PMMA and the PMMA/C20A organoclaynanocomposites with different clay concentrations. Thefirst 390 s on the time scale of these curves correspond tothe signal collected for pristine PMMA samples, beforethe injection of nanoclays. Then, after a transient behavior,a permanent regime is reached where the intensities aretime independent. In this regime, the scattered intensityincreases and the transmitted intensity decreases withorgananoclay concentration. For the pristine PMMA onecan see that both signals are very flat and the repeatabilityis very good. We can also notice that the optical sensor isvery sensitive to the organoclay concentration. The curvesfor transmitted light (Fig. 9) show that the light intensitydecreases with increasing organoclay concentration. Thisdecreasing in light intensity is probably due to the

Fig. 9 Measurements of transmitted light intensity of pristine PMMAand PMMA organoclay nanocomposites with different organoclayconcentrations

Fig. 8 Light transmitted (▲) and scattered (○) by a poly(ethyleneoxide) aqueous solution containing silica particles at 0.5% in massfraction. p represents the part of particles which have a diameter of440 nm and (1-p) represents those which have a diameter of 100 nm

Fig. 7 Light transmitted (▲) and scattered at θ=90° (○) by 100 nmdiameter silica particles at various mass fraction in a poly(ethyleneoxide) aqueous solution

Fig. 10 Measurements of scattered light intensity of pristine PMMAand PMMA organoclay nanocomposites with different organoclayconcentrations

6 Int J Mater Form (2012) 5:1–9

reduction of optical transparency caused by the presenceof organoclay. As expected the scattered signal shows anincrease of scattered light intensity with increasingorganoclay concentration, due to the increasing organo-clay particle size.

The transient regime between the pristine PMMAsignal and the stationary regime at long times presents arich behavior: during the first 80 s, a quasi-lineardecrease (resp. increase) of the transmitted (resp. scat-tered) intensity is observed, followed by a slowerdecrease of both the scattered and the transmittedintensities. This behavior is observed for the threestudied concentrations. In order to compare the intensityevolutions for the three studied concentrations, let usconsider the normalized intensities:

InorðtÞ ¼ IðtÞ � Iðt ¼ 0ÞIððt ! 1Þ � Iðt ¼ 0Þ

Whatever the volume fraction, the initial evolution of thenormalized intensities (Figs. 11 and 12) during the first80 s of the transient regime, perfectly superimpose. In thisregime, we thus simply observe the gradient of concen-tration resulting from the injection of PMMA/nanoclaysamples after pristine PMMA samples. Let us moreovernotice that rescaling of the time scale is not necessary toobtain the superposition of all the data. The observedgradients of concentration are thus due to convection inthe mixture, and not due to diffusion of the charges insidethe polymeric matrix. On the contrary, the longer timedecrease of both the scattered and the transmittedintensities at 4% do not superimpose with the curvesobtained at 1% and 2%. Light is more scattered and lesstransmitted than the master curve obtained at the lowestorganoclay fractions. Due to the incompleteness of ourscattering measurements (we only collect light at 90° andin the forward direction), we cannot assert the origin of the

Fig. 11 Evolution of the normalized transmitted intensities as afunction of time. Continuous line: f=1%, short dashed line f=2%,long dashed line, f=4%

Fig. 13 Measurements of scattered light intensity of both PMMA/C30B (exfoliated) and PMMA/C20A (intercalated)

Fig. 12 Evolution of the nor-malized transmitted intensitiesas a function of time. Continu-ous line: f=1%, short dashedline f=2%, long dashed line, f=4%; the small figure at the toprepresents the evolution of thescattered intensity in the longtime stationary regime as afunction of organoclay content.The straight line is an affine fitto the first two concentrations

Int J Mater Form (2012) 5:1–9 7

excess of scattering and lack of transmission for all thevolume fractions. Nevertheless, we must admit that sometransient change in the system occurs on times of the orderof 150 s after the beginning of mixing. The excess ofscattering could thus be due to the existence of gradientsof concentrations and, as a consequence, of refractiveindexes, due to non-perfect mixing. It could also be due toa slow change in the aggregation state of the organoclayparticles after mixing. Both phenomena would lead to anincrease of the scattered signal. The non-scaling behaviorof the light scattered and transmitted by the 4% sample,may be explained by multiple scattering as the concen-tration of the nanoclay is increased. Indeed, a posterioriobservation of the mixture reveals that the mostconcentrated sample is very turbid. In this case, theoptical path rapidly increases with the concentration. Asa consequence, both scattering and absorption increasewith the volume fraction faster than a linear behavior, asobserved for times ranging from 80 to 200 s after thebeginning of the mixture. The occurrence of multiplescattering, leading to non-linear evolution of the intensi-ties with the organoclay (Fig. 12) content is moreoverconfirmed by the observation of the asymptotic long timestationary scattered intensities: although the intensity isaffine with the scattered intensity for ϕ=1 and 2%, the 4%sample scatters less. As absorption and single lightscattering would lead to affine behaviors, this proves thatmultiple scattering plays a role for the most concentratedsample.

The very stable signal obtained for the nanocomposites,can lead to the conclusion that the organoclay are welldispersed in the PMMA matrix. To see the sensitivity ofnanocomposite structure, the PMMA/C30B at 4 wt% oforganoclay (exfoliated), and the PMMA/C20A at 4 wt%of organoclay (intercalated) were introduced separately inthe extruder and the sensor. The results obtained arepresented in Fig. 13. One can observe that the opticalsensor is sensitive to the nanocomposite morphology. Thescattered signal curves reveal that the light intensityscattered by the intercalated nanocomposite (PMMA/C20A at 4 wt %) is greater than that scattered by theexfoliated nanocomposite (PMMA/C30B at 4 wt %). Thisobservation is in agreement with TEM observations,where the organoclay particle sizes in an intercalatedstructure are greater compared to those in the exfoliatedstructure.

Conclusion

The development of a new optical sensor based on lightscattering dedicated to real-time monitoring in nanocompo-sites processing was described. Preliminary results on

model samples lead us to designdrove a light scatteringwith two angles of measurement: 0° for light transmission,and 90° for light scattering. The on-line sensor is verycompact and can be easily connected on many polymerprocessing device as soon as dynisco (pressure) fittings areavailable. Validation experiments proved the quality ofresults in terms of signal repeatability and sensitivity toorganoclay particle concentration and nanocomposite struc-tures respectively. This work will now be extended to thedirect characterization of the influence of processingconditions of a twin-screw extruder on the nanocompositemorphology.

Acknowledgements This study was carried out in the frame IPEuropean research program “MULTIHYBRIDS”, No. 026685-2, inthe 6th Framework Program. We also thank Mr Christophe MELARTand Mr Christophe SUTTER for their help and their availability.

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