Body armor has evolved significantly over time. In our article level 3+ ceramic plates we talked about the history of hard body armor and its evolution. In this article, we will be talking about two common materials used in soft body armor, UHMWPE vs Kevlar. This article is of particular importance to me coming from a family who served their county and community in the military and law enforcement.

UHMWPE (Ultra-High Molecular Weight Polyethylene) and Kevlar are two materials widely used in the manufacturing of body armor. In this article, we will delve into the key differences and similarities between UHMWPE and Kevlar body armor, to help you see the evolution of soft body armor.

Armor Overview

Soft body armor
Flexable, soft body armor

UHMWPE Body Armor

UHMWPE is a long-chain thermoplastic known for its remarkable strength, durability, and lightweight properties. These characteristics make it an attractive choice for body armor. UHMWPE fibers are woven into sheets and then layered to create ballistic panels, which can be used in various types of body armor including bulletproof vests and helmets.

Kevlar Body Armor

Kevlar is a para-aramid synthetic fiber also renowned for its high strength-to-weight ratio and durability. It was invented in 1965 by chemist Stephanie Kwolek. The fibers found their way to replacing steel parts on tires, used in canoes, and all types of products. Kevlar fibers are woven into a fabric, which is then layered and used to produce ballistic panels for body armor applications. The precursor to UHMWPE, Kevlar is utilized in bulletproof vests, helmets, and other protective gear.

Ballistic Performance

Both UHMWPE and Kevlar offer excellent ballistic performance. However, UHMWPE exhibits a higher tensile strength, which translates to superior energy absorption capabilities. Consequently, UHMWPE body armor tends to be more effective at stopping bullets and reducing blunt force trauma. Kevlar, while still providing strong ballistic protection, does not perform as well as UHMWPE under similar circumstances. Ultimately, Kevlar paved the way for UHMWPE and is now an obsolescent design, but that doesn’t mean it’s bad. Kevlar was the peak of performance back in the day, and was used in law enforcement vests, flak jackets, and helmets. Kevlar led to the ultimate functional design of UHMWPE. 


Weight is a factor when considering body armor as it directly impacts the wearer’s mobility and comfort. Let’s be honest, if body armor is too uncomfortable who would wear it? UHMWPE body armor comes in at a lower weight than Kevlar due to the material’s inherently low density. This reduced weight not only enhances wearer comfort but also allows for improved maneuverability. This makes UHMWPE armor a good choice for those who require extended periods of wear.

Durability and Environmental Resistance

Both UHMWPE and Kevlar body armor demonstrate impressive durability and resistance to environmental factors. However, UHMWPE offers better resistance to moisture, UV radiation, and chemicals, which can be significant in maintaining the armor’s performance over time. Kevlar is more susceptible to degradation when exposed to certain chemicals and UV radiation, which may necessitate more frequent replacement or additional protective measures. That said, most armor manufacturers recommend replacing soft body armor every five years, more often if it is worn every day, due to the interaction with body fluids and oils. 

Flexibility and Comfort

UHMWPE fibers are more flexible than Kevlar fibers, which can impact the overall comfort of the body armor. The increased flexibility of UHMWPE allows for greater freedom of movement and a more comfortable fit. Kevlar tends to be a bit more rigid and needs more form fitting. 

When it comes to UHMWPE vs Kevlar, they are both high-performance materials used in body armor, with unique strengths and characteristics. However, they are both an example of the evolution of body armor. Kevlar used to be the premiere option for soft armor. UHMWPE is now considered to be and is also used in the production of many hard armor plates. It is likely as armor advances there will be a new contender that will knock UHMWPE off its throne.

The opinions expressed in this post are those of the author and do not necessarily reflect the views and opinions of Tacticon Armament.

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