Dilute solution viscosity of polyethylene terephthalate (PET)

The Viscotek Dilute Solution Viscosity (DSV) system provides fully automated determination of the viscosity of polyethylene terephthalate (PET) resins, with safety, precision, and accuracy

Introduction

The Viscotek Dilute Solution Viscosity (DSV) system provides fully automated determination of viscosity. The system features the Viscotek Y-501 Relative Viscometer, the semi-automated sample preparation (SASP) and injection system, software, and accessories to provide for the ultimate in automation, safety, precision, and accuracy. The DSV system provides excellent results for the solution viscosity of polyester terephthalate (PET) resins, as shown in this application communication.

Experimental

In this work, the samples were analyzed in two solvents, o-chlorophenol (OCP) and 3:2 Phenol:TCE. Sample preparation was made automatically on the SASP system with a correction for thermal expansion. The run conditions were as follows: The temperature was fixed at 30° C. The concentration was 0.500 g/dL. The total solvent usage per sample with duplicate injections and including washing was 50 mL. The time of analysis per injection was 5.5 minutes and the average standard deviation of analysis was less than 0.0003 dL/g. Both solvent dispensing and sample analysis were carried out in a closed loop system to minimize solvent exposure.

Measurements were made on duplicate preparation and duplicate injections from each vial to show the precision of both the viscometer and the sample preparation system.

Results

The exact concentrations of the PET/OCP samples are given in table 1. The precision of the thermal expansion correction from the room temperature concentration to the analytical temperature concentrations should be noted.


Table 1: Concentrations prepared by the SASP system with the correction for room temperature.

Vial

Sample (g)

Volume (mL)

Room Temp. Conc. (dL/g)

Analytical Temp. Conc. (dL/g)

1A

0.1925

38.25

0.5034

0.4999

1B

0.1649

32.75

0.5036

0.5002

2A

0.1794

35.63

0.5036

0.5002

2B

0.1829

36.32

0.5035

0.5001

3A

0.1606

31.90

0.5035

0.5000

3B

0.1897

37.67

0.5035

0.5001

4A

0.1701

33.80

0.5034

0.4999

4B

0.1763

35.03

0.5035

0.5000

5A

0.1750

34.75

0.5036

0.5002

5B

0.1754

34.85

0.5033

0.4999

The phenol:tetrachloroethane (Phenol:TCE) proved to be a better solvent for dissolution of the samples. The SASP preparation system was used to prepare single volumes of each Phenol:TCE sample. Duplicate injections were made from each vial. The Viscotek Model Y-501 Relative Viscometer measures solution viscosities of the sample relative to the reference solvent simultaneously, thereby avoiding errors due to temperature fluctuation and solvent variations.

Table 2 : Accuracy and precision of the Y-501 viscometer for the OCP samples.

Sample

Injection

Run

Specific Viscosity

Inherent Viscosity (dL/g)

PET1

A

1

0.3306

0.5713

2

0.3312

0.5724

B

1

0.3323

0.5737

2

0.3329

0.5745

PET2

A

1

0.3242

0.5615

2

0.3244

0.5617

B

1

0.3239

0.5610

2

0.3240

0.5613

PET3

A

1

0.3238

0.5609

2

0.3239

0.5611

B

1

0.3240

0.5612

2

0.3244

0.5618

PET4

A

1

0.3528

0.6059

2

0.3542

0.6066

B

1

0.3639

0.6059

2

0.3539

0.6059

PET5

A

1

0.3299

0.5700

2

0.3299

0.5700

B

1

0.3293

0.5695

2

0.3293

0.5695

Table 2 gives the details the accuracy and precision of the Y-501 Viscometer for the OCP samples: The data for the samples run in 60% phenol / 40% TCE is shown in table 3. Note the reproducibility within each run.

Table 3: High reproducibility of the samples ran in 3:2 Phenol:TCE

Sample

Run

Specific Viscosity

Inherent Viscosity (dL/g)

PET1

1

0.3791

0.6426

PET1

2

0.3792

0.6429

PET2

1

0.3716

0.6317

PET2

2

0.3723

0.6328

PET3

1

0.3690

0.6284

PET3

2

0.3690

0.6284

PET4

1

0.4037

0.6780

PET4

2

0.4039

0.6784

PET5

1

0.3753

0.6372

PET5

2

0.3751

0.6370

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