ML100271832

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Investigation of Relative Deterioration Temps & Hydrogen Chloride Evolution of Chlorinated Jacket Compounds by Means of Thermal Gravimetric Analysis & Differential Thermal Analysis
ML100271832
Person / Time
Site: Indian Point Entergy icon.png
Issue date: 02/04/1982
From:
Boston Insulated Wire & Cable Co
To:
Shared Package
ML093430851 List:
References
B902, NUDOCS 8202090373
Download: ML100271832 (12)
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Text

AN INVESTIGATION OF THE RELATIVE DETERIORATION TEMPERATURES AND HYDROGEN CHLORIDE EVOLUTION OF CHLORINATED JACKET COMPOUNDS BY MEANS OF THERMAL GRAVIMETRIC ANALYSIS AND DIFFERENTIAL THERMAL ANALYSIS Report No. B902 BOST

'J________

INSULATZ_

WIRE & CABLE CO.

65 BAY STREET BOSTON, MASSACHUSETTS 02125 820209o373 826204 PDR ADOCK 05000286 P

PDR

D TABLE OF CONTENTS Page

1.

INTRODUCTION 1I.

CHOICE OF MATERIAL............

111.

OBJECTIVE.

I

V. PROCEDURE

V.

RESULTS 0

J

I. INTRODUCTION The destruction by fire of a reinforced concrete German plastics plant, where large quantities of polyvinyl chloride (PVC) were stored, prompted this Boston Insulated Wire & Cable Co. (BIW) research project. The aftermath of the fire, which revealed that the steel reinforcing rods were cor roded, caused BIW engineers to wonder what would happen to BIW cable compounds when sub jected to fire and water or steam. They engaged the services of Arthur D. Little, lnc.,.a prominent consulting firm, to assist in a total evaluation.

It was found that a rapid increase in the evolution of hydrogen chloride (HCI) gas occurs alike in PVC and BIW compounds of neoprene and chlorosulphonated polyethylene (CSPE) between 3000 C and 350 0C, with a gradual lessening at temperatures above 350 0C. Above this tempera ture, however, the 8IW neoprene compound evolves about one-half as much HCI gas as PVC, and the BIW CSPE compound evolves only about one-fifth as much HCI gas as PVC. The relative hazard of corrosion from similar quantities of BIW neoprene compound and BIW CSPE com pound is less than from PVC, and BIW CSPE compound is less hazardous than neoprene. All three materials are very stable to HCI liberation at the normal-rated temperature of about 1000C and also through the maximum temperature range of 150 0C, which may be encountered during an incident.

The ultimate effect of these gases and the corrosive effect of hydrochloric acid, which would be promptly formed in the case of fire extinguished by water or in the presence of steam, is open to question. Concrete is a material which would neutralize the HCI before it could reach the rein forcing rods unless a continually large volume of HCI were concentrated in a particular area of concrete.

It should be pointed out that these results are derived from representative BIW and commercial compounds, that a number of assumptions have had to be made in the calculations and that the conditions of temperature rise are arbitrary, i.e., from room temperature to 4000C in one-half hour.

This report, therefore, can be taken as an initial step in the analysis of the hazards which might be present with the adoption of flameproof cable-jacketing materials.

0-II. CHOICE OF MATERIAL Chlorinated polymers are required in jacketing materials when cables are to be exposed to oil and must be flame and radiation resistant. It is recognized that many other compositions of cable jackets are now in use, and this should be the basis for further study. However, this report con cerns itself only with compounds incorporating chlorine for flame resistance in their molecules when subjected to temperatures high enough to cause thermal decomposition of these polymers The most generally accepted chlorinated compound cable constructions are:

PVC...........

as insulation as jacket over insulation as jacket of cable Neoprene..........

as jacket over insulation as jacket of cable CSPE...........

as insulation as jacket over insulation as jacket of cable Therefore, two 81W compounds and one purchased compound were taken as the basis for this study, and the following results are derived from these representative compounds.

Ill. OBJECTIVE The objective of this investigation is to determine the decomposition temperatures and relative amounts of HCI gas evolved from the decomposition of PVC, CSPE and neoprene. Typical BIW and commercial compounds were used at temperatures from 1 50C to 4000C.

The compounds used were:

PVC.

Neoprene.

CSPE purchased 900C appliance-wire compound.

BIW-SOX.

heavy-duty neoprene jacket.

BIW BOSTR AD 7 heat and radiation-resistant.

compound for nuclear power plants.

0

I

V. PROCEDURE

Approximately 17 milligrams of each material was exposed to thermal analysis and close exami nation was made of the corrosive gases (HCI) evolving at particular temperatures.

1. Thermogravi metric Analysis (TGA) reveals the continued change in weight during heating period.
2. Differential Thermal Analysis (DTA) measures the thermal changes of each sample with increasing temperature and determines the temperature at which these compounds become exothermic.
3. Continual monitoring of the acidity (pH) values of the evolved gases during the thermal cycle (TGA) which determines the relative amount of gases which dissolve in water, with the assumption that the pH changes are de rived from HCI gas. The evolved gases were bubbled through distilled water and the pH of the water was taken as the material reached the following temperatures:

Every 500C up to 2000C, Every 250C from 2000C to 3000C, Every 50C from 3000C to 3500C, and At 3750C, and at 4000C.

In order to arrive at some relative values of HCI evolved, a curve of pH vs. normality of HCI was plotted, using data from page 1721 of the 1958-59 edition of the "Handbook of Chemistry and Physics," and extrapolated to a pH of 6.

In all cases, the evolved gases were bubbled through 50 milliliters of distilled water (and here we must assume 100% solution of the HCI gas). A reasonable assumption is that a conversion of pH to per cent HCI evolved from the gas can be made.

V. RESULTS

1.

GRAPH A the results of the TGA up to temperatures of 4750C indicate that there is only slight weight loss up to 3000C. Above 3500C, CSPE has slightly less weight loss than neo prene, and both have considerably less than PVC. At 4750C, the per cent weight losses were as follows:

CSPE (BOSTRAD7 )

= 35%

Neoprene (B lW-SOX) = 39%

PVC

= 62%

It is possible that the weight loss of neoprene may be overshadowed by its rapid oxygen absorp tion at these temperatures.

2.

GRAPH B The results of the OTA indicate that all three materials become exo thermic at approximately 2500C, which is indicative of decomposition. The sharp rise in the curve with neoprene and the dip in the curve with CSPE, in the temperature range from 3000C to 3500C, is not easily explained. One possible explanation is that, in neoprene, oxidation first ex hibits itself by a lowering of elongation and an increase, or a very slight change, in tensile strength.

(This is quite similarto what happens in the vulcanization process, which is an exothermic process.)

This cross-linking process, due. to oxidation, is probably more exothermic than chain scission and results in a decrease in the length of the polymer chain which follows this high rise. CSPE is more stable to oxidation in this temperature range and may become endothermic due to evapora-0 tion of volatile materials in the compound.

From this data, the conclusion may be drawn that jackets of CSPE compound are better than neoprene and possess about the same degree of stability as PVC jackets from the aspect of thermal degradation due to overheating up to 4000C.

3.

The results of the analysis of the decomposition gases by measuring the pH of the solution, through which the HCI gas passes during the heating periods, are shown in the following graphs:

GRAPH C

. plots the pH of the solutions as observed for the three materials over the temperature range to 4000C.

GRAPH D... plots the pH vs. normality of hydrochloric acid for use in computation of the amount of HCI gas evolved. The extrapolation to an original pH of 6 was necessary as the ini tial values of pH were noted as 5.8 - 5.9.

4

An example of the calculation of the per cent HCI gas by weight from a specimen follows:

Material PVC Temperature 350C pH of Solution at 3500 C

= 2.85 (Graph C)

Normality of HCI corresponding to a pH of 2.85 =.00135 (Graph D)

Molecular weight of HCI = 36.47 Concentration of HCI per liter of water at pH of 2.85 =.00135 x 36.47

=.0482 grams per liter Since 50 milliliters of water were used in the test:*

HCI evolved =.0482 x 5 0

=

.00241 grams 1000 2.41 milligrams Original weight of PVC

= 16.82 milligrams Per cent HCl evolved is 2.41 = 14.3%

16.82 GRAPH E portrays the percentages of the three materials calculated in this manner over the temperature range to 4000 C. The actual calculated values and the relationship of one ma terial to another are as follows:

PERCENTAGE OF EVOLVED HCl

°C CSPE Neoprene PVC 150 0

0 0

300

.15%

.10%

3.6%

350 2.7%

7.6%

14.3%

400 3.2%

8.7%

16.3%

CSPE Relative CSPE Relative Neoprene Relative

°c to Neoprene to PVC to PVC 150 300 350 400 0

0 35%

37%

0 4%

19%

20%

0 3%

53%

53%

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