G Love: Background
G Love: Background
The purpose of this project was to create a "smart" glove that will keep one's hand warm in a cold environment. The gloves will either be heated by a resistive heating element attached to a battery, which turns itself off when reaching a maximum temperature, or give off heat by releasing the latent heat stored by phase change materials sewn into the material of the glove.
While there are a number of heated gloves already on the market, many are extremely bulky and therefore not suitable for everyday wear. For instance, most of these gloves are heated with the power of two D cell batteries (one for each glove) or four AA cell batteries (two for each glove) which must be strapped around the wrist. Others are very thick and are only intended for activities such as skiing or motorcycle riding where intense winds are experienced. The gloves vary in thickness of materials and fabrics being used as well as the specified use of the gloves. Many of the companies that produce battery powered gloves do not disclose what wire is used as the heating element. However, engineers at Malden Mills stated that their gloves use stainless steel wire and their new fabric with wire woven into it also contains stainless steel. Examples of several gloves are shown below:
Price $139
These gloves, manufactured by Gerbing's Heated Clothing, require 22 Watts of energy (the G Love design will require 2.7 Watts) to run. The outer material is leather with Kevlar protection and the inner is a Helsapor lining. The gloves heat the entire length of each finger as well as the back of the hand. (This is similar to the G Love design). However, the gloves must be plugged into a special socket located in a "Gerbing's jacket or in a three-plug harness, provided at no extra cost.
Price $19.98
These gloves are supplied online by Harriet Carter. They are powered by two D cell batteries. The gloves are made of insulated nylon that also helps to keep out cold and moisture.
Price Was $39.95, now $29.95
The company that produces these gloves is Weather Affects. These gloves are battery powered by two D cell batteries. The power can be turned off when you don't need it. There is a knit cuff at the wrist to aid keeping in heat. These are available in small, medium and large.
Price $59.95
These electric hand warmers are made of two waterproof mylar layers with a heating element sealed between each layer. The gloves are made of polypropylene. The gloves require 2 AA batteries each. The gloves are meant to be inserted into insulated ski gloves to give extra warmth for "up to 8 hours." The batteries are attached at the wrist by a neoprene strap. These gloves require that you have another pair of gloves in which they can be inserted.
As a PCM undergoes a liquid/solid phase transition at a constant temperature, they store/release heat as the latent heat of fusion. While most heating systems are based on sensible heat (the heat of an object that is changing temperature), latent heat applications are becoming more and more popular because they have a much greater volumetric heat storage capacity.
In addition to clothing, PCMs are also commonly used in building applications such as insulation for houses.
Parrafin wax and polyethylene glycol (PEG) are two PCMs with this capability. They can be incorporated into clothing fabric to maintain a comfortable temperature in cold weather. For example, while a person is physically active in the cold outdoors, the body is giving off enough heat to melt the PCM. Thermal energy is then stored in the PCM. When the person is at rest or exposed to a colder environment, the body needs additional heat to remain comfortable. Thus, the PCM freezes and releases the stored thermal energy, providing warmth to the person. A major advantage of PCMs is that they are completely reversible. They can be heated and cooled repeatedly without changing their thermal properties.
For paraffin wax, the exact temperature of the liquid/solid transition is dependent on the number of carbon atoms on the chain backbone. Octadecane (C18H38) has a melting temperature of 27°C, which is close to the temperature of the human body (37°C). Thus the PCM can be re-melted just from heat produced by the body. A high heat of fusion and commercial availability at reasonable cost are two advantages to using octadecane.
PEG with a molecular weight of approximately 1000g/mole also has a phase transition in the desired temperature range. One advantage of PEG is that a permanent press finishing technique utilized in the fabric industry can be employed to bind PEG to fabric. Clothing with PEG can endure numerous washing cycles, and even though PEG is in direct contact with the skin, it does not cause irriation. For more information about PEG and octadecane, see the materials page.
A major challenge with using PCMs for a heating element is how to incorporate the phase change material into the fabric. One major factor to consider is the efficiency of heat release. One method that has been used to incorporate PCMs into fabric is microsphere fabrication. Theoretically, the advantage of microspheres is based on their large surface to volume ratio. This means that heat can be released more quickly from the spheres resulting in a more efficient glove. Microsphere fabrication is a relatively straightforward process. It has a wide range of applications and is commonly used in many different types of drug delivery systems.
Microspheres containing PCM, made by Outlast Technologies for use in clothing.
Two companies that specialize in PCMs for use in clothing are Frisby Technologies and Outlast Technologies. For an excellent animation about how PCM microspheres store and release heat, view this Technology Review article.
A second method of incorporating phase change materials into clothing is to embed them in a material where the PCM will phase separate. This may be more efficient than microspheres simply because it removes a step from the fabrication process. A good example of this method is the co-extrusion of polypropylene and polyethylene glycol. Because polypropylene is very hydrophobic and PEG is very hydrophilic the two materials phase separate when mixed together resulting in small particles of PEG encapsulated in polypropylene. However, one limitation of this process is that one cannot go above PCM concentrations of approximately 20% by volume. Above 20% the PEG will begin to form channels in the polyproplene resulting in a very different microstructure that is not appropriate for the heating element desired in the gloves.
Back to Team 2 Home Page.