Additives of Polyamide 6
1. Functional Additives 2. Fillers
3. Reinforcements
Functional Additives
1. Anti oxidants 2. Heat stabilizers
3. UV stabilizers 4. Nucleating agents
Fillers:
1. Silicon dioxide - increase tear strength
2. Mica and talc improve stiffness, strength, hardness, heat distortion characteristics, dimensional stability and surface finish
3. Metal powders (aluminium, bronze, steel, lead, zinc, copper, nickel) improve heat distortion characteristics and particularly, electrical conductivity
4. MoS2 and graphite are used particularly in glass fiber reinforced polyamides to improve slip and wear characteristics.
Reinforcements:
- The main reinforcement for PA is glass fiber material.
- It is used in proportions of up to 50% w/w in PA 6 and PA 66 and upto 30% w/w in PA 69, 61, 11 and 12. Tensile strength, stiffness, hardness, heat distortion characteristics, tracking resistance, chemical and hydrolysis resistance are all improved.
- Carbon fibers increase the elastic modulus significantly more than glass fiber material and also improve slip properties, thermal and electrical conductivity.
Grades of Polyamide 6
The Polyamide 6 is available in various grades
- Injection molding grade
- Extrusion grade
- Rotational Molding grade
- Fluidized bed coating grade
Processing considerations for Polyamide 6
- The tendency of the material to absorb water
- The high melting point of the homopolymer
- The low melt viscosity of the homopolymers
- The tendency of the material to oxidise at high temperature where oxygen is present
- The crystallinity of the solid polymer and hence the extensive shrinkage during cooling.
- The material has to be predried at 80°C for 2 - 4 hours.
While molding Polyamide attention on the following points is essential.
- High Injection speed of the molding machine
- Control of shot or size
- Minimizing drooling by nozzle of reverse tapper type.
- Shrinkage of the part
- Annealing at 130° to 149°C for 10 - 20 hrs.
Polyamide 6 – By casting Technique
Cast Polyamide 6: This is made by activated anionic polymerization of monomeric caprolactam in molds. Properties are similar to PA 6. Cast Polyamide 6 is normally of very high molecular weight. Depending on the polymerization condition, its properties can be varied between tough and elastic to tough and hard.
- Thick walled mouldings, high weight mouldings (upto 1000 Kg), embedding of components (Roller cores)
Large mouldings of all kinds eg. heating oil tanks upto 10000 liters capacity
Surface finishing of Polyamide 6:
- Moldings may be painted or printed without pretreatment
- The high resistance of PA to solvent facilitates coating and even recoating with stoving requires bond on UF or MF resins
- Mouldings can be colored by immersing in aqueous or alcoholic solution of dye stuffs, particularly azo dyes
- Hot embossing with suitable foils pose no problem
- Metal finishes are applied by vacuum metallization
- In Recent years there has been growing interest in electroplated PA moldings
- These require extremely high quality surfaces
- Products containing fillers are used for reflective electroplated parts
- Special purpose glass fibre reinforced grades are suitable for moldings with extruded surfaces
- Applications include wheel trims, door handles, window winder and water fittings
Machineability of Polyamide 6:
Cutting: Casted products/ molded products are workable with most of the tools and machining which are designed for working with wood and metal.
- However higher efficiency is obtainable with equipment specially designed for plastics
Joining: PA components are frequently joined with ordinary or self-lapping screws and rivets as well as snap connectors
Welding of Polyamide 6
- All processes developed for welding thermoplastics are suitable for polyamides.
- The preferred methods are ultrasonic friction and heated tool welding (heating by contact or radiation).
- High frequency and heat impulse welding are used mainly for joining films.
- The ultrasonic method enables welding of standard injection molded parts to be integrated in automated production.
Bonding of Polyamide 6
- Polyamides can be bounded with numerous adhesives based on solvents or lacquers.
- An adhesive can be quickly prepared by shaking a rerorcinol/ Ethanol solvent mixture for 15 minutes.
- Concentrated formic acid, dimethyl formamide and aqueous phenol (12% water) are also suitable.
- A polyamide containing calcium carbide/ ethonal solvent adhesive can be used for food applications or in water supplies.
- It is resistant, non-toxic and odour-free, solid adhesives with or without chemical cross linking can be used for example for bonding bearing bushes into metal assemblies
Applications of Polyamide 6(Areas of Applications)
1. Appliances 2. Automotive
3. Business equipment 4. Consumer products
5. Electrical 6. Hardware
7. Machinery 8. Packaging
Applications of Polyamide 6
- Laundry equipment - Dishwashers and disposers
- Cooking equipment - Housecleaning equipment
- Consumer electronics - Small kitchen appliances
- Sewing machine - Personal care and grooming
- Cooling equipment
Automotive
- Chassis parts - Power plant
- Decorative body parts - Functional body parts
- Electrical parts - Fuel system
- Instrumentation - Heating, ventilating
- Air-conditioning - Accessories
Business equipment
- Business machines - Vending machines
- Office equipment
Consumer products
- Kitchen utensils - Toys
- Sporting goods - Apparel fitments
- Personal accessories - Photographic equipment
- Musical instruments. - Brush bristles
- Packaging - Film for cooking
- Fishing line
Electrical
- Industrial controls - Wiring and associated devices
- Industrial connectors. - Batteries
- Telephone parts. - Switches
Hardware
- Furniture fittings Door and window fittings. - Tools
- Lawn and garden implements - Boat fittings
Machinery
- Agricultural Mining and oil drilling - Food processing
- Printing. - Textile processing
- Engine parts - Pumps, valves, meters, filters
- Air blowers - Material handling equipment
- Standard components. - Gears
- Cams - Sprockets. - Bearings
- Gaskets. - Pulleys. - Brushes
- Film and coated substrates
- In compatible hydrocarbon polymers such as PE can be melt with Polyamides to yield compositions that have improved higher permeability and are processable film and filaments and bottles.
- Improvement in moisture absorption, impact strength, flexibility, moulding characteristics and structure uniformity are claimed for blends made from Polyamide and ethylene / alkyl acrylate ester copolymers.
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