Soft body armor is essential for law enforcement officers, military personnel, and others whose jobs involve exposure to potentially lethal projectiles. It is designed to absorb and disperse the energy of a bullet or other projectile, reducing the likelihood of injury or death. However, soft body armor can be affected by environmental conditions, including extremely cold or hot temperatures. 

Soft body armor is typically made with woven materials such as Aramid (typically known as Kevlar) or other synthetic unidirectional fibers such as Ultra-high-molecular-weight polyethylene (UHMWPE), to create a flexible, lightweight fabric. When a bullet or other projectile strikes the armor, the energy of the impact is spread out over a large area, reducing the force that is transmitted to the wearer's body. However, the armor's effectiveness depends on the fibers' ability to absorb and disperse the energy of the impact. This is where exposure to cold temperatures can become a concern.  

 

Extreme cold weather conditions

When the temperature drops, many materials become more brittle and less flexible. This is because the molecules that make up the material slow down, making it more difficult for them to move around and adapt to changes in shape. In the case of soft body armor, exposure to direct freezing temperatures when not worn against the body, can cause the fibers to become stiff and brittle, reducing their ability to absorb and disperse the energy of a bullet impact, which may result in a higher likelihood of projectile penetration. 

The effects of extreme cold on soft body armor can vary depending on several factors, including the type of fibers used in the armor, the temperature and duration of exposure, and the specific design of the armor. Some synthetic fibers, such as UHMWPE, are more susceptible to degradation from extreme cold than Aramids. For example, a study published in the Journal of Polymer Science found that exposure to -40°C (-40°F) for 24 hours resulted in a decrease in the tensile strength of UHMWPE fibers. The researchers also noted that exposure to extreme cold caused the fibers to become more brittle, potentially reducing the effectiveness of UHMWPE soft body armor. 

Another study published in the journal Applied Polymer Science found that exposure to temperatures below -60°C (-76°F) for 24 hours caused UHMWPE fibers to become more rigid and brittle, resulting in a decrease in the material's ballistic performance. The researchers noted that exposure to extreme cold could cause irreversible damage to UHMWPE fibers, reducing the overall effectiveness of soft body armor made from this material. 

In general, the longer the exposure to extremely low temperatures, the greater the risk of degradation. 

To mitigate the risk of cold weather affecting the efficacy of soft body armor, it is essential to take proper care of the armor and to follow manufacturer guidelines for use and storage. For example, during winter, it's crucial to ensure the body armor is not stored outdoors in snowy or freezing temperatures. If exposure to extreme cold is unavoidable, allowing the armor to warm up gradually before use is important. Rapid temperature changes can cause the fibers to become more brittle and increase the risk of material degradation.  

Despite these precautions, it is essential to recognize that exposure to extremely cold temperatures can still potentially degrade the efficacy of soft body armor. However, by taking proper precautions and following manufacturer guidelines, wearers can help minimize the risk of injury or death and ensure that their soft body armor remains an effective tool for protecting their lives. 

 

Extreme hot weather conditions

As mentioned above, soft body armor panels are typically made of high-performance fibers, such as Kevlar and/or Ultra-high-molecular-weight polyethylene UHMWPE, that are woven or laminated to create a strong, flexible barrier against ballistic threats. However, these fibers can degrade when exposed to extreme heat. 

When exposed to extreme heat or direct exposure to sunlight (UV radiation), the materials in the armor can become more susceptible to wear and tear from everyday use. For example, heat can cause the fibers to become more brittle, leading to increased fraying or tearing with repeated use. This can further compromise the armor's integrity and reduce its effectiveness over time. Prolonged exposure to direct sunlight can cause the fibers to break down, lose their strength and effectiveness, and eventually, compromise the protective capabilities of the armor.

Kevlar is made up of long chains of molecules called polymers, which are held together by strong chemical bonds. These chains are aligned in a specific way to give Kevlar its unique properties, including its strength and resistance to impact and abrasion.

When Kevlar is exposed to direct sunlight, the ultraviolet (UV) rays in the sunlight can break down the chemical bonds that hold the polymer chains together. This process, known as photodegradation, weakens the material and can cause it to lose its strength and durability over time.

When UHMWPE body armor is exposed to extreme heat, several things can happen. The fibers can start to melt or soften, which can cause the armor to lose its shape and become less effective at stopping projectiles. Additionally, the heat can cause the material to degrade, leading to a reduction in its overall strength and durability. The yield strength of UHMWPE generally decreases with increasing temperature. When the fibers are exposed to high temperatures, they can lose their structural integrity, reducing the armor's ability to absorb and distribute the impact of a bullet or other ballistic threat.

Rapid changes in temperature, such as going from extreme heat to extreme cold or vice versa, can cause soft body armor to undergo thermal stress. This stress can cause the fibers in the armor to expand or contract rapidly, leading to changes in their structure and performance. Over time, repeated exposure to thermal stress can weaken the fibers and reduce the overall effectiveness of the armor. 

Typically, soft body armors that contain aramids and/or UHMWPE degrade with long exposures to direct sunlight, heat, moisture, and extreme cold. An example of what not to do with soft body armor is to store it outdoors, where it could potentially be exposed to direct sunlight, as UV radiation degrades the material, potentially decreasing the performance of the soft body armor over time.

Proper care and maintenance of soft body armor help ensure that it remains effective in providing reliable protection against ballistic threats and is ready for use when needed. Wearers of soft body armor must follow the manufacturer's instructions and any regulations or standards for proper maintenance to ensure the armor's integrity and effectiveness. So, regular inspections, cleaning, and proper storage should be a routine for anyone who relies on soft body armor for protection.