PolymerViscosit Lab Report-1

Running head: POLYMER VISCOSITY

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Polymer Viscosity Laboratory 2

University of Technology, Jamaica Polymer Science March 29 , 2017

Aim: To determine: ●

The absolute viscosity of a polystyrene-toluene system of d ifferent concentrations

●

The viscosity average molecular weight of a polystyrene-toluene polymer

Theory:

According to Elert (2015), Viscosity describes the internal friction of a moving fluid that


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causes resistance to flow. All polymers increase the viscosity of the solvent that the y are dissolved in. This increase allows for a convenient method of determining the molecular weight of polymers. The relation between viscosity and concentration becomes more complicated when, with increasing concentration, the molecules begin to interact with each other, first through hydrodynamic interaction that is a long range effect, and then by forming actual contacts, aggregates, and networks (Weissberg, Simha & Rothman, 19 51). Dilute Solution Viscosity is used as an indication of the molecular weight of polymers, the test result of this is called the intrinsic viscosity. According to Intertek Plastics Technology Laboratories (n.d.), the intrinsic viscosity is used for polymers that dissolve completely without chemical reaction or degradation and can provide an excellent determination of lot-to-lot consistency or be used to compare molded parts to original resin for determinations of degradation from molding. The intrinsic viscosity,[ η ] as function of average molecular weight, M is represented by Mark-Houwink-Sakurada equations

[η] = KMα (1) where K and α are constants for a given polymer– solvent – temperature solvent – temperature system (Yacob et al., n.d.).

The plots used to find the intrinsic viscosity are called the Huggins plot ( hred vs. c ) and the Kraemer plot ( ln(h / h o) vs. c ). As shown on the graph below, the curves of both plots should be linear and have a common intercept that is the intrinsic viscosity.


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In this experiment, the absolute viscosity and the av erage molecular weight of polystyrene

  C and a value of 0.72 dissolved in toluene is investigated. investigated. A K value of 11.0 E-3 at 30 (Ebewele, 2000) are used in the th e calculation for this experiment. Polystyrene is a vinyl a vinyl polymer.

Structurally, it is a long hydrocarbon chain, with a phenyl group attached to every other carbon atom. Polystyrene is produced by free by free radical vinyl polymerization, from polymerization, from the monomer styrene (The University of Southern Mississippi, 2005a).


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The weight-average molecular weight (Mw) of the commercially-available PS that is widely used as industrial material is generally 150,000 to 400, 000 (Application brief, 1995). However, according to Wegner (n.d.), the molecular weight for anionically produced polystyrene ranged from 4500 to 510000. Toluene on the other hand, han d, is a colorless, water-insoluble liquid with the smell associated with paint-thinners. Apparatus & Materials: ●

Polystyrene

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Viscometer

●

Toluene

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250ml beaker

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100ml measuring cylinder

●

spatula

Methodology: As seen on Laboratory Sheet

Results: Toluene

Concentration gPS/100g Toluene

Kinematic Viscosity (mm2/s)

Run 1 0.00 0.34139 Run 2 0.00 0.34131 Average 0.00 0.34135 s Table 1. Viscosity results upon measuring pure toluene.


Solution 1 Kinematic Viscosity (mm2/s)

Dynamic Viscosity (mPa.s) 0.28956 0.28950

Density (g/cm3)

Temperatur e (oC)

0.8482 0.8482

40.0060 40.0080

0.28952

0.8482

40.007

Dynamic Viscosity (mPa.s)

Density (g/cm3)

Temperatur e (oC)


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Run 1 0.01 1.0668 0.92747 Run 2 0.01 1.0912 0.94378 Average 0.01 1.079 0.935625 s Table 2. Viscosity results upon measuring a solution of 0 .01gPs/100g toluene.


Solution 2 Kinematic Viscosity (mm2/s) 0.64874 0.66492


Run 1 0.005 Run 2 0.005 Average 0.005 0.65683 0.56041 s Table 3. Viscosity results upon measuring a solution of 0.005gPs/100g toluene..

0.8507 0.8507

40.0070 39.9880

0.8507

39.9975

Density (g/cm3)

Temperatur e (oC)

0.8492 0.8496

40.0080 39.9910

0.8494

39.9995

Density (g/cm3)

Temperatur e (oC)

0.8488 0.8487

40.0110 40.0060

0.84875

40.0085

Density (g/cm3)

Temperatur e (oC)

Solution 3


Kinematic Viscosity (mm2/s) 0.49286 0.49652


Run 1 0.0025 Run 2 0.0025 Average 0.0025 0.49469 0.41989 s Table 4. Viscosity results upon measuring a solution of 0 .005gPs/100g toluene.


Solution 4 Kinematic Viscosity (mm2/s) 0.41441 0.41542


Run 1 0.00125 0.8486 Run 2 0.00125 0.8486 Average 0.00125 0.414915 0.35208 0.8486 s Table 5. Viscosity results upon measuring a solution of 0.00125gPs/100g toluene.

39.9920 39.9980 39.995


Solution Concentration Averages

Toluene 0

6

ηrel

0.34135 1

ηspec

0

ηred

-

ηinh

-

Solution 1.079 1

0.01

3.160978468 2.160978468 216.0978468 115.0881621

Solution 0.65683 2

0.005

1.924212685 0.924212685 184.842537 130.9033778

Solution 0.49469 3

0.0025

1.449216347 0.449216347 179.6865387 148.409184

Solution 0.414915 4

0.00125

1.215511938 0.215511938 172.4095503 156.1322689

Table 6. Relative, specific, reduced,and inherent viscosity results upon measuring varied concentrations of Polystyrene-Toluene solutions.


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Viscosity of Polystyrene-Toluene Solution 250

y = 4898.7x + 165.3 200

150

y = -4653.3x + 159.45 100

50

0 0

0.002

0.004

0.006

0.008

0.01

0.012

Reduced Viscosity

Inherent Viscosity

Linear (Reduced Viscosity)

Linear (Reduc ed ed Viscosit y) y)

Line ar ar (Inher en ent Visc os osity)

L in ine ar ar (In he her en ent Viscosity)

Graph 1. Reduced and inherent viscosity vs concentration of a polystyrene-toluene solution.

[ƞ] =

165.3 K= 11E-03 a= 0.725 M= 577050.77 Table 7. Showing results of viscosity average molecular weight based on the reduced viscosity v iscosity of polystyrene-toluene solution


[ƞ] =

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159.45 K= 9.30E-03 a= 0.72 M= 549073.04 Table 8. Showing results of viscosity average molecular weight based on the inherent viscosity of polystyrene-toluene solution

Average Molecular weight (577050.77 + 549073.04)/2= 563061.96 g/mol

Sample Calculations: Using Kinematic Viscosity

Relative Viscosity

ηrel = η/η0 = 1.079/

0.34135

=3.160978

Specific viscosity

ηs = ηr-1 =3.160978-1 =2.16097

Reduced Viscosity

(ηr -1)/C= ηred = 2.16097/0.01


=216.0978 Inherent Viscosity

ηinh= (ln (ηrel))/C = (ln(3.160978))/0.01 = 115.0882

Intrinsic Viscosity At concentration =0

ηred [C=o]= ηintrinsic ηred = 165.3

ηinherent [C=o]= ηintrinsic ηinh = 159.45

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Discussion:

In the experiment conducted it was expected ex pected of the experimenters to determine the viscosity average molecular weight and the absolute viscosity of polymer solutions. The solution that was mentioned was of varying concentrations con centrations of toluene with a constant mass of polystyrene. In this manner both molecules are both nonpolar no npolar allowing the dissolution of the polystyrene in the toluene. The dissolution also occurs due to the fact that the polymer-solvent interactions are greater than that of the polymer-polymer pol ymer-polymer attractive forces. This phenomena causes the polymer chain segment to absorb ab sorb solvent molecules, increasing the volume of the polymer matrix, and loosening out from their coiled shape, thus altering the solution viscosity (University of Southern Mississippi, 2005b). Polystyrene is a thermoplastic polymer made from petroleum, it is a non-sustainable, non-renewable, heavily polluting and fast-disappearing commodity (The Way To Go, n.d.). According to ChemicalSafetyFacts.org, polystyrene is made b y stringing together, or polymerizing, styrene, a building-block chemical used in the manufacture of many products. Toluene, also known as methylbenzene, is an organic chemical compound. Toluene is a very good solvent because, unlike water, it can dissolve many organic compounds compound s (Nissa Garcia, n.d.). Intrinsic Viscosity (IV) is a measure of the polymers molecular weight and therefore

reflects the material’s melting point, crystallinity and tensile strength (Lloyd Instruments, 2013). According to Wagner (n.d.), a less complicated method of determining the weight average molecular weight is the intrinsic viscosity; this is so as this method yields the viscosity average molecular weight which is close in value to that of the weight average molecular mole cular weight.


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According to Gooch (n.d.), reduced viscosity is the fluid viscosity increase per unit of polymer solute concentration. A plot of the Concentration against Reduced Viscosity also known as the Huggins Plot seeks to satisfy the Mark-Houwink-Sakurada equation. According to Neira-Velazquez et al. (n.d.) the intrinsic viscosity as the limiting value of the ratio of the solution’s specific viscosity to the concentration of the solute as the concentration approaches zero, reflects the capability of a polymer in solution to increase the viscosity of the solution. Therefore, the intrinsic viscosity viscosity is the y-intercept on a graph of concentration against reduced viscosity & inherent viscosity; the intrinsic viscosity was found to be 165.3 ml/g and 159.45 ml/g respectively. All polymers increase the viscosity of the solvent in which they are dissolved. This increase allows for a convenient method of o f determining the molecular weight of polymers (Hester, 2001). This can be seen in figure 1 as the concentration increases, so does the reduced viscosity of the system. The Mark-Houwink-Sakurada equation was u sed to determine the molecular weight of the polystyrene-toluene system. This was don e by utilizing the intrinsic viscosity found as well as the constants K and a at 11E-03 and 0.725 respectively. The molecular weight was found to be 563061.96 g/mol which is slightly outside the region stated by Wegner (n.d) and application brief (1995) of between 4500 and 510000. Based on the graph, the reduced and inherent viscosity lines are straight lines as expected however they did not converge at the y intercept hence the average molecular weight was found by finding the molecular weight of each line and then averaging them. The resulting average molecular weigh was found to be outside the range of commercially acceptable polystyrene this could be as a result of the the viscometer used being designed to be used for oil based substances and not polymers.


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Conclusion

It can be concluded that toluene is categorized as a good solvent thus producing an intrinsic viscosity for the polystyrene- toluene system of 165.3 ml/g and 15 9.45 ml/g using the reduced viscosity and inherent viscosity respectively, this resulted in an av erage molecular weight of 563061.96 g/mol.


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References

Application brief. (1995). DSC measurement of Polystyrene- The Effects of Molecular Weight on Glass Transition. Retrieved from http: http://www.hitachihightech.com/file/global/pdf/products/science/appli/ana/thermal/application_TA_068e.pdf Chemical Safety Facts. (2016). Polystyrene. Retrieved from https://www.chemicalsafetyfacts.org/polystyrene-post/?tab=1 Ebewele, R.(2000). Polymer Science and Technology. CRC Press LLC: USA Elert, G. (2015). Viscosity. Retrieved from http://physics.info/viscosity/ http://physics.info/viscosity/ Garcia, N. (n.d.). What is Toluene?-Structure, Toluene? -Structure, Uses & Formula. Retrieved from http://study.com/academy/lesson/what-is-toluene-structure-uses-formula.html Gooch, J.W. (2011). Reduced Viscosity. Retrieved from http://link.springer.com/referenceworkentry/10.1007%2F978-1-4419-6247-8_9831 Guadalupe etal. (n.d). Polymer Molecular Weight Measurement. Retrieved on March 31, 2016 from: https://www.researchgate.net/file.PostFileLoader.html?id=54203675d039b158168b 4616&assetKey=AS%3A273610176557057%401442245157430. Hester, R. (2001). Molecular Weight Determination By Dilute Solution Viscosity Measurements. Retrieved from http://pslc.ws/macrog/lab/dsvh.htm Intertek PTL (n.d.). Dilute Solution Viscosity of Polymers. Retrieved from http://www.ptli.com/testlopedia/tests/iv-d2857.asp Kulicke, M & Clasen, C. (2004). Viscosimetry of pol ymers and polyelectrolytes. SpringerVerlag Berlin Hiedelberg: USA Lloyd Instruments. (2013).The Importance Of Intrinsic Viscosity (IV) Measurement Throughout The PET Supply Chain - Lloyd Instruments. Retrieved from


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http://www.azom.com/article.aspx?ArticleID=4577 The University of Southern Mississippi. (2005a). Polystyrene. Retrieved on March 30, 2016 from http://pslc.ws/macrog/styrene.htm The University of Southern Mississippi. (2005b). How a pol ymer gets dissolved. Retrieved from http://pslc.ws/macrog/property/solpol/ps3.htm The University of Southern Mississippi. (2005c). Molecular weight. Retrieved from http://pslc.ws/macrog/weight.htm The University of Southern Mississippi. (2005d). Dilute solution viscometry. Retrieved from http://pslc.ws/macrog/vis.htm TheWayToGo. (2008). Polystyrene Fast Facts. Retrieved from http://isites.harvard.edu/fs/docs/icb.topic967858.files/PolystyreneFactSheets.pdf Wegner, H. (n.d.). The Mark-Houwink-Sakurda Eq uation for the Viscosity of Atactic Polystyrene. Retrieved from http://www.nist.gov/data/PDFfiles/jpcrd286.pdf Weissberg, S.G., Simha, R. & Rothman, S. (1951). Viscosity of Dilute and Moderately Concentrated Polymer Solutions. Journal of Research of the National Bureau of Standards, 7. Retrieved from http://nvlpubs.nist.gov/nistpubs/jres/47/jresv47n4p298_A1b.pdf Yacob, N., Talip, N., Mahmud, M., Sani, N.A., Samsuddin, N.A. & Fabillah, N.A. (n.d.) Determination of Viscosity-Average Molecular Weight of Chitosan Using Intrinsic Viscosity Measurement. Retrieved from http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/44/122/44122710.pdf

PolymerViscosit Lab Report-1

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