1. Compounding Technique

2. Rubber compounding
What is rubber compounding? Why we are doing? How can we do it successfully?

3. Definition of Rubber Compounding
is the art and science of selecting and combining elastomers and additives to obtain an intimate mixing that will develop the necessary physical and chemical properties for a finished product.

4. Objective of Rubber Compounding
1. To secure certain properties in the finished product to satisfy service requirements. 2. To attain processing characteristics necessary for efficient utilization of available equipment. 3. To achieve the desirable properties and processability at lowest possible cost.

5. To be Sucessful in Compounding
Must understand the properties and function of hundreds of elastomers and rubber chemicals
Must also have intimate knowledge of the equipment used for mixing, extrusion, calendering, molding and vulcanization.

6. Procedure for Compound Development
1. Set specific objectives (properties, price, etc.).
2. Select base elastomer(s).
3. Study test data of existing compounds.
4. Survey compound formulations and properties data presented by material suppliers in their literature .
5. Choose a starting formulation.

7. To be continued 6. Develop compounds in laboratory to meet objectives.
7. Estimate cost of compound selected for further evaluation.
8. Evaluate processability of compound in factory.
9. Use compound to make a product sample
10. Test product sample against performance specification.

8. Classification of Compounding Ingredients
1. Elastomers
2. Vulcanizing Agents (Curatives)
3. Accelerators
4. Activators and Retarders
5. Antidegradants(Antioxidants, Antiozonants, Protective Waxes)
6. Processing Aids(Peptizers, Lubricants, Release Agents)

9. To be continued 7. Fillers (Carbon Blacks, Non-black Materials)
8. Plasticizers, Softeners, and Tackifiers
9. Color Pigments
10. Special Purpose Materials(Blowing Agents, Reodorants, etc,)

10. Requirements of Rubber Compound for Good Processing
1. Uniform plasticity and recovery.
2. Uniform scorch rate.
3. Uniform rate of cure.

11. Vulcanizing Agents
To cause chemical reaction resulting in crosslinking of elastomer molecules.
Sulfur is by far the most widely used.

12. VULCANIZING AGENTS
TYPE COMMON USE
Sulfur or Sulfur- Natural Rubber, bearing Materials Isoprene, SBR, Buty1, Butadiene, EPDM, Nitrile,Norsorex
Organic Peroxides Urethane, Silicone, Chlorinated Polyethylene, Crosslinked Polyethylene, Vamac, Vynathene, PVC/ Nitrile

13. To be continued TYPE COMMON USE
Metallic Oxides Neoprene, Hypalon,Thiokol
Organic Amines Acrylic, Fluorocarbon, Epichlorohydrin, Vamac
Phenolic Resins Butyl

14. ACCELERATORS
Use to reduce vulcanization time, or cure time by increasing the speed of vulcanization
Most are organic substance containing both nitrogen and sulfur(Today)
Inorganic accelerator was widelyused years ago (litharge, lime, and magnesia)

15. ORGANIC ACCELERATORS TYPE EXAMPLE TYPICAL USE
Aldehyde-amine Reaction product of Fast curing butyral dehyde and accelerator for aniline reclaim,hard rubber and self curing cements
Amines Hexamethylene Delayed action tetramine slow accelerator for natural rubber

16. To be continued TYPE EXAMPLE TYPICAL USE
Guanidines Diphenyl guanidine Secondary accelerator (DPG) to activate thiazole type accelerator
Thioureas Ethylene thiourea Fast curing accelerator (ETU) for Neoprene,Hypalon and Epichlorohydrin

17. To be continued TYPE EXAMPLE TYPICAL USE
Thiazoles Benzothiazyldisulfide Safe-processing (MBTS) moderately fast curing accelerator for natural rubber, Isoprene,SBR, Nitrile,Butyl and EPDM
Thiurams Tetramethylthiuram Fast curing sulfur disulfide (TMTD) bearing accelerator for SBR, Nitrile, Butyl and EPDM

18. To be continued TYPE EXAMPLE TYPICAL USE
Sulfenamides N-cyclohexyl Safe-processing, benzothiazyl delayed action sulfenamide accelerator for (CBS) natural rubber, SBR and Nitrile
Dithiocarbamates Zinc dimethyl Fast curing accelerator
Xanthates Dibutylxanthogen Fast curing, low disulfide temperature accelerator for natural rubber and SBR

19. Activators and Retarders
Activators used to activate the accelerator and improve its effectiveness (ZnO, stearic acid, litharge, magnesia, and amine) attain good crosslink efficiency
Retarders used to reduce the scorchness (phthalic anhydride, salicylic acid and sodium acetate)

20. Antidegradants
To retard the deterioration of rubber compounds initiated by
- oxygen, ozone
- heat, light
- metal catalyst and
- mechanical flexing

21. PROCESSING AIDS
To facilitate processing operation such as Mixing Calendering Extrusion and Molding

22. PROCESSING AIDS Activated Dithio- Pepton 44 Peptizer for NR
COMPOSITION EXAMPLE(Tradenames) FUNCTION
Activated Dithio- Pepton Peptizer for NR
bisbenzanilide
Poly Polyac Chemical conditioner
paradinitrosobenzene for IIR

23. To be continued
COMPOSITION EXAMPLE(Tradenames) FUNCTION
Xylyl mercaptans RPA Peptizer for NR, IR, SBR and NBR Stabilizer for cement viscosity
Low-molecular A-C Polyethylene Release agent, weight A lubricant polyethylene
Calcium oxide DesiCal P Dessiccant

24. To be continued
COMPOSITION EXAMPLE(Tradenames) FUNCTION
Aliphatic Strucktol 60NS Homogenizing naphthenic- agent for all aromatic resins elastomers
Paraffin Wax Numerous Release agent, lubricant
Polyethylene Carbowax PEG Activator for glycol silica lubricant
Petroleum Petrolatum Release agent, hydrocarbon lubricant

25. Fillers To reinforce physical properties To reduce cost
Devided into two types(Reinforcing and Extending)
Selection of reinforcing filler is the third most important task in compounding(next to elastomer and cure system)

26. Types of Fillers Reinforcing Type
Carbon Black (listed in order N220 (ISAF) of increasing particle size) N330 (HAF) N550 (FEF) N762 (SRF-LM) N990 (MT)
Non-Black Silica Zinc Oxide Magnesium Carbonate Aluminum Silicate Sodium Aluminosilicate Magnesium Silicate

27. Types of Fillers (continued)
Extending Type - Calcium Carbonate - Barium Sulfate - Aluminum Trihydrate - Talc

28. Hardness NR has hardness itself (no filler) 35-40 IRHD
ISAF phr increases 1 IRHD
HAF phr increases 1 IRHD
Hisil phr increases 1 IRHD
Hard clay phr increases 1 IRHD
Soft clay phr increases 1 IRHD
Whiting phr increases 1 IRHD CaCO3
Oil phr decreases 1 IRHD

29. Particles Size
Play a major role in the tensile strength small particle size highest tensile strength at optimum loading
Fine fillers is difficult to process (need more energy for their dispersion into the elastomer)
Effects Mooney scorch small particle size the scorch resistance reduces

30. PLASTICIZERS,SOFTENERS, AND TACKIFIERS
Objective for Using Aid mixing, Modify viscosity, Produce tack, Provide flexibility at low temperature

31. Selection of Plasticizers
The important criteria are:
Compatibility
Efficiency
Cost
Example:
- Aromatic type oil is not compatibe with NR, Isoprene, IIR, EPDM
- Paraffinic type oil is not compatible with SBR, butadiene, NBR, CR

32. PLASTICIZERS,SOFTENERS, AND TACKIFIERS
CATEGORY OF MATERIAL FUNCTION
Petroleum Oils -Aromatic Plasticizer,Softener Paraffinic Naphthenic
Ester Plasticizers - Dioctyl phthalate Dioctyl sebacate Tributoxyethyl phospate Low temperature - Di (butoxyethoxyethyl) formal plasticizers - Triglycol ester of vegetable oil

33. To be continued CATEGORY OF MATERIAL FUNCTION
Vulcanized Vegetable Oils Extender, Plasticizer
Asphaltic Hydrocarbon Extender, Plasticizer
Pine Tar Plasticizer,Tackifier
Resins -Coumarone-indene Tackifier,Plasticizer Petroleum Phenolic
Polymeric esters Extender, Plasticizer
Rosins - Hydrogenated rosin Tackifier

34. Special Purpose Materials
Not require in the majority of rubber compound
Used for specific purpose Example:
- Blowing agents Reodorants Adhesion promotors Flame retardant Fungicide UV light absorbers