An electric hand mixer is a basic houseware essential for mixing, blending, whipping and beating. This electric hand mixer helps automate the repetitive tasks of stirring whisking and beating. These are portable and possess mixing and blending tools that has two removable metal beaters and variable speeds. This kitchen device uses a gear driven mechanism to rotate a set of beaters.
Mixers for the kitchen first came into use in nineteenth century. Due to industrialization the demand from commercial bakers in large scale developed. Because of that. demand for mixer increased.
The first mixer with electric motor was invented by American Rufus Eastman in 1885. The new models were introduced in 1914 played a major role in the mixer part in industry.
The Hobart Kitchen Aid and Sunbeam Mixmaster (first produced 1910) were two very early US brands of electric mixers.
Since the technology has been developed today there are various types of mixers can be found in market.
• Stand mixer
• Spiral mixer
• Planetary mixer
• Hand mixer
• Dough mixer
Function of beater is to mix the ingredients which we put into the bowl.
Most probably beaters are inContact with water and atmospheric oxygen. Since it contacts with them beater should be made of stainless steel to avoid rusting. Therefore, stainless steel material is used in beater. Stainless steel is an alloy and it is an anticorrosive material.
Properties of stainless steel
• Higher corrosion resistance
• Higher ductility
• Higher work hardening rate
• Higher hot strength
• Higher strength and hardness
• A more attractive appearance
i. Corrosion resistance
Stainless steel are iron based alloys. It contains a minimum of around 10.5% chromium. a self-healing protective clear oxide layer is formed by chromium. corrosion resistance is given by this oxide layer. Even if the material surface is cut or damaged, selfheal will occur, and corrosion resistance will be maintained. painting or galvanizing are two methods to protect normal carbon steel from corrosion.
ii. Higher ductility
The % elongation during a tensile test is given by the ductile property. The elongation for austenitic stainless steels is high.
iii. Higher work hardening rate
Stainless steel has the significant increases to the strength of the metal can be achieved through cold working. cold working and annealing stages can give a specific strength.
iv. Higher hot strength
This property depends in accordance with the Chromium content in the alloy. silicon, nitrogen and rare earth elements are also can increase the hot strength of the stainless steel. High chromium ferritic grades like 446 can also show high hot strength. The high chromium content of stainless steels also helps to resist scaling at elevated temperatures.
v. The strength and hardness
Stainless steels tend to have higher tensile strength when compared to mild steel. The duplex stainless steels have higher tensile strengths than austenitic steels.
The highest tensile strengths are seen in the martensitic (431) and precipitation hardening grades (17-4 PH). These grades can have strengths double that of TYPES 304 and 316, the most commonly used stainless steels.
Different types of stainless steel
• Austenitic stainless steel
• Ferritic stainless steel
• Martensitic stainless steel
• Duplex stainless steel
1) Austenitic stainless steel
This contains a minimum of 16% chromium and 6% nickel. They range from basic grades like 304 through to super austenitics such as 904L and 6% Molybdenum grades. These are non- magnetic.
The properties of the steel can be modified by adding elements like molybdenum, Titanium and Copper. As results of modifications steel suited to high temperature applications or increase corrosion resistance. Most steels become brittle at low temperatures but the Nickel in austenitic stainless makes it suited to low temperature or cryogenic applications. A common name for 304 stainless steel is 18/8, for 18% chromium and 8% nickel.
Applications for austenitic stainless steels include:
• Kitchen sinks
• Architectural applications such as roofing and cladding
• Roofing and gutters
• Doors and Windows
• ovens and chemical tanks
• Benches and food preparation areas
• Food processing equipment
• Heat exchangers
2) Ferritic stainless steel
This contains grades like 430 and contain only chromium as a major alloying element. The quantity of chromium present ranges from 10.5 to 18%. This steels are magnetic. These are not susceptible to stress corrosion cracking.
Ferritic stainless steels are typically used in:
• Vehicle exhausts
• Fuel lines
• Cooking utensils
• Architectural trim
• Domestic appliances
3) Martensitic stainless steel
This steel composed of high carbon and lower chromium content. They are magnetic, have moderate corrosion resistance and poor weldability.
Martensitic stainless steels are typically used for:
• Knife blades
• Surgical instruments
4) Duplex stainless steel
This steel has high chromium and low nickel contents. They include alloys like 2304 and 2205. These alloys are so named due to their respective compositions – 23% chromium, 4% nickel and 22% chromium, 5% nickel. Duplex grades are resistant to stress corrosion cracking, but not to the same level as ferritic grades. The toughness of duplex grades is superior to that of the ferritic grades – but inferior to that of the austenitic grades. These grades are readily welded and have high tensile strengths.
Duplex stainless steels typically find application in areas like:
• Heat exchangers
• Marine applications
• Desalination plants
• Food pickling plants
• Off-shore oil & gas installations
• Chemical & petrochemical plant
Function of the outer cover is to protect the interior parts of the mixer.
Outer cover of the electric hand mixer is made of plastic. Plastic means a kind of polymer. By examining the outer cover carefully, we discovered that the casing is made of PVC. (Poly Vinyl Chloride).
PVC (Poly Vinyl Chloride)
PVC is a thermoplastic polymer and it is widely used plastic type. This has been initially synthesized in 1872 by the Goodrich company. It is resistance to environmental degradation, chemical and to alkalis. PVC is very dense compared to most plastics (specific gravity around 1.4). these are readily available and cheap. Rigid PVC is very hard and has extremely good tensile strength.
Plastics are malleable and can be molded into solid objects. They have plasticity property. They are organic polymers with high molecular mass.
There are seven different types of plastics.
1. Polyethylene Terephthalate (PETE or PET)
2. High – Density Polyethylene (HDPE)
3. Poly Vinyl Chloride (PVC)
4. Low Density Polyethylene (LDPE)
5. Polypropylene (PP)
6. Poly Styrene or Styrofoam (PS)
7. Miscellaneous plastics (includes: polycarbonate, polylactide, acrylic, acrylonitrile butadiene, styrene, fiberglass and nylon)
Advantages of plastics
• Highly resistive to electricity
• Light weight
• Low cost
• Resist to corrosion and chemicals
• Resist to water
• Easy to manufacture
Types of plastics
• Polyethylene Terephthalate (PETE or PET)
J. Rex Whinifield and James T. Dickson introduced this plastic type in 1940. These are used for crystal clear beverage bottles, soda bottles, water bottles, medicine jars, combs, and carpets. These are repurposed to make textiles, carpets, life jackets, pillow stuffs, auto parts, shoes and luggage. These can be recycled.
• High Density Polyethylene
This type was introduced by Kari Ziegler and Erhard Holzkamp in 1953. Initially this plastic type was used for pipes in storm sewers. At present these are used in milk jugs, juice containers, grocery bags, shampoo and conditioner bottles, detergent containers and in bleach containers. These can be recycled.
• Poly Vinyl Chloride
This was discovered on accident twice, once in 1838 by Henri Victor and again in 1872 by Eugen Baumann. “Poison plastic” is another name for PVC. This is the least recycle material. These are used in shoes, gutters and windows.
• Low Density Polyethylene (LDPE)
This type is used for cling wrap, sandwich bag, grocery bags, frozen food bags and flexible container lids.
Polypropylene was discovered by J. Paul Hogan and Robert L. Banks in 1951. This is used in plastic diapers, Tupperware, kitchenware, yogurt container, bottle caps and in margarine tubes. Polypropylene cannot be recycled.
• Polystyrene or Styrofoam (PS)
Polystyrene was discovered accidently by German apothecary Eduard Simon in 1839. Hermann Staudinger did a research and expand the use of this plastic; polystyrene. This is used in disposable coffee cups, plastic food boxes, packing foam and packing peanuts. These are cannot be recycled.
• Miscellaneous plastics
These are polycarbonate, polylactide, acrylic, acrylonitrile butadiene, styrene fiberglass and nylon. These are used in plastic CDs and DVDs, baby bottles, medical storage containers eyeglasses and exterior lighting fixtures. These are cannot be recycled.
Polymer is a useful chemical made out of a lot of repeating units. These repeating units are often made of carbon, hydrogen and sometimes nitrogen, oxygen, chlorine, Sulphur, florin, phosphorous and silicon. These repeated union of small molecules are known as monomers. Polymers have unique properties according to type of molecule being bonded. As these are large, polymers are also called as macromolecules.
Polymers can be divided into two;
Polymers which have same type of repeating units.
Polymers composed of two or more different repeat units.
Properties of polymers.
I. Unique flexibility
II. Light in weight with significant degree of strength
III. Chemical resistance
IV. High durability
V. Easy processability
VI. Thermal and electrical insulation properties
VII. Cost effectiveness
Physical properties of polymers
Physical properties of polymers include molecular weight, molar volume, density, degree of polymerization and crystallinity of materials.
• Molecular weight
Molecular weight is expressed by the equation;
Mn = mean (middle) molecular weight of size range i.
xi = the fraction of the total number of chains with the corresponding size range.
• Weight average molecular weight
Weight average molecular weight is expressed by the equation;
Mi = the mean molecular weight within a size range
wi = the weight fraction of molecules within the same size interval.
This is based on the weight fraction of molecules within the various size ranges.
Mechanical properties of polymers
• Stress-strain curve
• Tensile strength
• % elongation to break
• Young’s Modulus
The stress which needs to break a sample is called as tensile stress. This is a valuable property for polymers that are going to be stretched.
The ratio of stress to strain is called the Young’s modulus. In a graphical representation it is given by the gradient of stress-strain curve.
The toughness is the measure of energy that a sample can absorb before breaking.
In day today, life we can identify different types of motors such as AC motor, DC motor and special types of motors. Here in hand mixer we were able to find an AC motor. There are several parts in a motor as they are specialized to perform different task. Some of them are stator, rotor and shaft. We were finally able to recognize that the mid steel was used to make the motor.
Function of the motor is supply needed energy to perform the task of the equipment.
Mild steel is a kind of steel with a low content of carbon. Hence it is known as “low carbon steel”. The amount of carbon typically found in mild steel is 0.05% to 0.25% by weight. Mild steel is not an alloy steel hence, it does not contain large number of other elements.
Composition of mild steel
• Carbon 0.05% – 0.25%
• Manganese 0.7% – 0.9%
• Silicon maximum 0,40%
• Sulfur maximum 0.04%
• Phosphorous maximum 0.04%
Properties of mild steel
2) Machinable and weldable
3) Impossible to harden and strength through heating and quenching.
4) Have magnetic property as it contains high amount of iron.
5) Relatively affordable when compared with other steel.
6) Mechanical properties
Mechanical property Metric Imperial
Hardness, Brinell 126 126
Hardness, Knoop 145 145
Hardness, Rockwell 71 71
Hardness, Vickers 131 131
Tensile strength, ultimate 440MPa 63800psi
Tensile strength, Yield 370MPa 53700psi
Elongation at break 15% 15%
Reduction of area 40% 40%
Modulus of elasticity 205GPa 29700ksi
Bulk modulus 140GPa 20300ksi
Poisson ratio 0.29 0.29
Machinability 70% 70%
Shear modulus 80GPa 11600ksi
Applications of mild steel
ii. Structural steel