Chlorinated polyethylene (tyrin) &

ChlOROSULPHONATED Polyethylene

(hypalon)

Modification of PolyethyleneAdvantage of choosing PE: Saturated backbone Cheapest monomer Good thermal, oxidative stability & excellent weather ability.

Modification may be of two types:A. Co-polymerisation:

EPDM LLDPE VLDPE EVA

B. Chemical modification (post polymerisation modification): Chlorinated polyethylene (CPE) Chlorosulphonated polyethylene (CSM)

Chlorinated polyethylene (CPE)Introduction of Cl group has various opposing effects:

i)Reduces chain regularity (Cl group is introduced randomly), thereby restricting the polymer to crystallize which tends to increase rubberiness.ii)It increases interchain attraction .iii) Imparts good oil resistance and flame resistance properties.iv) Compatibility with polar rubber increases.

Commercial products:

Commercially available CPE : 26-42% chlorinationNormal grade: 36% Cl content, ML (1+4) @ 120°C : 85

Chlorinated polyethylene (CPE)Manufacturing process:TYRIN CPE products are made by chlorinating polyethylene (PE) to form CPE.

Cl content Brittleness temp (°C) RT structure Physical form Softening

point (°C)

8 % < -70 Crystalline --- 69

25% < -70 Mainly amorphous Rubbery 20

40% ~ -70 Amorphous Soft & flexible 20

54% + 20 Amorphous Rigid 52

60% + 40 Amorphous Rigid & brittle 67

Chlorinated polyethylene (CPE)Processing of CPE:CPE can be processed in conventional elastomer processing equipment like internal mixers, 2 roll mill etc.Conventional mixing technique is adopted, otherwise for highly loaded stocks ‘upside down’ technique is followed.Thermal softening during processing is a reversible phenomenon.Good bin stability.

Compounding of CPE:1.CPE polymer type2.Performance requirements3.Compounding ingredients4.Total cost of producing the final article

Curing of CPE: Generally peroxides are used for curing for CPE. Most commonly used are:I. Dicumyl peroxideII. Bis(t-butylperoxyisopropyl)benzeneIII. 2,5-dimethyl-2,5-di(t-butylperoxy)hexane

Theses peroxides are used in conjunction with a promoter like triallylcyanurate (TAC)

Non peroxide curing involves thiadiazole derivatives in conjunction with aniline-butyraldehyde derivatives.

MgO is used as a heat stabiliser. To avoid moisture sensitivity lead stabilisers may be used.

Expensive polar plasticizers like DOP, DOS are used.

Chlorinated polyethylene (CPE)

Chlorinated polyethylene (CPE)Cable heater jacket formulation using CPE (90°C rating):

Ingredients Functions Amount (phr)

Tyrin CM 0136 Base polymer 100

CaCO3 Filler 50

Di – isononyl phthalate Plasticizer 25

Amino silane functionalised hydrated aluminium silicate Filler 60

MgO Acid acceptor 5

Polymerised 1,2 dihydo 2,2,4 trimethyl quinoline Antioxidant 0.2

Bis(t-butylperoxyisopropyl)benzene dispersed on clay (40% active) Peroxide 5

85% Sb2O3 Flame retardant 6

TAC Coagent 5

Chlorinated polyethylene (CPE)Applications of CPE:

Waterproofing membrane

Cable insulation

I. Wire and cable application (good heat and flame resistance property)II. Automotive hose coveringIII. Available in powder form : impact modifiers for plastics.

Chloro-sulphonated polyethylene(CSM)Chlorosulphonation:The CSM rubber contains both chlorine and sulphonyl chloride (-SO2Cl) group (Acts as a cure site).Chlorosulphonation is brought about by the Reed-Horn reaction that involves co reaction of SO2 and Cl2 in presence of light.

Cl2 hʋ

2 Cl

RH + Cl R + HCl

R + SO2 RSO2

RSO2 + Cl2 RSO2Cl + Cl

R + Cl2 RCl + Cl

[sulphochlorination]

[Chlorination]

Commercial products:

Chloro-sulphonated polyethylene(CSM)Chemical structure:

General characteristics:I. Very good weather ability, oxygen and ozone resistance owing to its

saturated backbone.II. The balance of chain flexibility and Cl content is such that the material

exists in rubbery range.III. Presence of chlorine confers hydrocarbon oil resistance and flame

resistance.IV. Very good heat resistance with an ‘EE’ rating by ASTM D 2000 being

obtainable.

Dry grade polymers (normal rubber compounds)Solution grade polymers (coating application)

% sulphur : ~ 1.87%% Chlorine : ~ 27%

Chloro-sulphonated polyethylene(CSM)Effect of chlorine content:

Heat and oil resistance of various elastomer:

Modified CSM (ACSM – Acsium®)Alkylated Chloro-sulphonated polyethylene:

Low temperature property is better than CSMHydrocarbon oil resistance property is inferior.

% sulphur : ~ 1.31%% Chlorine : ~ 36%

Compounding and vulcanization of CSM

HYPALON should be mixed and processed at as low a temperature as is practical.

Due to the presence of highly reactive sulphonyl group a wide variety of curing system can be applied:

I. Metallic oxide + rubber acclII. Metallic oxide + polyfunctional alcohol + rubber acclIII. Epoxy resin + rubber acclIV. Metallic oxide + bismaleimideV. Metallic oxide + peroxide coagent

ZnO is never used as if may lead to the formation of ZnCl2 which will degrade the

polymer. In case of diene rubber ZnO may be used with proper care.

Stearic acid can be used as a mould releasing agent..

CSM industrial roll cover : heavy duty mining cable jacket

Ingredients Amount(phr)

Hypalon 40 100

N990 100

PE617A 2

Carbowax 3350 1

Stearic acid 1

Loght process oil 10

DOP 15

Pentaerythritol PE200 3

Maglite D (MgO) 4

MBTS 0.5

Tetron A 1.5

Cured at 152°C for 20 minsHardness: 71 shore ATensile strength: 15.2 Mpa%EAB : 275

Applications of CSM1. Coated fabric and sheeting2. Wire and cable application3. Hoses and automotive application4. Heater hose, radiator hose, fuel hose.,

References

1. J.A.Brydson, “Rubbery Materials and Their Compounds”, 4th edition, Elsevier Applied Science, New York 1990.

2. “The Vanderbilt Rubber Handbook”, R.T Vanderbilt Company Inc. 13th edition,30, Winfield Street, 1990

3. C.M.Blow and C. Hepburn, “Rubber Technology and Manufacture”, 2nd edition Butterworth Scientific, London, 1982.