Compounding Technique

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-2-
  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

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

23
To be continued

• COMPOSITION EXAMPLE(Tradenames)
  FUNCTION
• Xylyl mercaptans RPA3 Peptizer
  for NR, IR, SBR and NBR.
  Stabilizer for cement viscosity
• Low-molecular- A-C Polyethylene
  Release agent, weight 617 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 PEG3350
  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 1.7 phr increases 1 IRHD
• HAF 1.9 phr increases 1 IRHD
• Hisil 233 2 phr increases 1 IRHD
• Hard clay 5 phr increases 1 IRHD
• Soft clay 7.7 phr increases 1 IRHD
• Whiting 6.4 phr increases 1 IRHD CaCO3
• Oil 2 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,Plasticize
  r - 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