Thermoforming vs. Fiberglass: A Manufacturing Needs Comparison

Are you trying to decide between thermoforming and fiberglass? Read this informative guide.

When deciding between thermoforming and fiberglass molding (FRP/GRP) for manufacturing parts, it's crucial to weigh the benefits of each method.

Thermoforming involves heating a two-dimensional thermoplastic sheet and shaping it into a three-dimensional form using vacuum and pressure. Thermoforming offers advantages such as faster production rates, through molded color, and decreased environmental impact.

On the other hand, fiberglass molding entails forming fiberglass-reinforced resin into shape, often by applying multiple layers to enhance strength and achieve the desired thickness. While fiberglass excels in producing large, lightweight structures, it has drawbacks such as limited capacity per tool, highly labor-intensive production, and lack of recyclability.

Part and Production Benefits

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Durability is a critical consideration in part manufacturing. Both thermoformed parts and fiberglass boast excellent durability, withstanding various environmental conditions and everyday wear and tear, but do so in different ways. Fiberglass produces a stiff, rigid part that deflects impact, while thermoform produces a part with some flexibility, allowing it to absorb impact. 

Like fiberglass, different materials, material combinations, and thicknesses change the amount of impact a part can handle. The same ability to vary material combinations also allows both molding processes to handle different environmental conditions, whether the extremes of summer and winter weather or the beating UV conditions of the sun. Both processes have options to handle the worst of Mother Nature's wrath.

Weight Reduction

Weight reduction is another factor, especially in industries like transportation, where fuel efficiency is paramount. Thermoformed parts are lightweight, contributing to fuel efficiency and reducing overall weight in various applications. In many applications, thermoform parts can be as much as 50% lighter than a similar part in FRP.

Speed of Production

Speed of production is often a determining factor when choosing a manufacturing method. Thermoforming offers faster production rates due to shorter cycle times and decreased labor, making it ideal for production quantities that have outpaced the capacity of fiberglass tooling. Fiberglass tooling is often similar in cost to thermoform tooling, so getting more parts per hour from a tool decreases tooling cost on a per-part basis and decreases the requirement to build multiple tooling sets.

Material Benefits

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Recyclability and sustainability are increasingly important considerations in modern manufacturing. Most thermoformed plastics are 100% recyclable, including the excess material (web), contributing to sustainability efforts and reducing environmental impact. The part and web can be ground or pulverized and re-extruded to make new sheets, rods, or resin pellets. While fiberglass parts can be recycled, it rarely is, due to the process being more complex and less efficient than thermoformed plastics.

Chemical Resistance

Chemical resistance is essential in applications where parts are exposed to corrosive substances. Thermoformed parts can be engineered with excellent chemical resistance properties, ensuring longevity and reliability in harsh environments. Fiberglass offers moderate chemical resistance but may require additional coatings or treatments for enhanced protection.


Safety is paramount in manufacturing processes. Thermoformed parts utilize resins that do not outgas volatile organic compounds (VOCs), making them safer for manufacturing processes and end-users. Fiberglass resins, on the other hand, can emit VOCs during curing, necessitating proper ventilation and safety protocols. Additionally, the resins and glass fibers can be skin irritants requiring additional protection when handling throughout the manufacturing assembly process.

Quality and Cost Benefits

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Tooling Costs

Tooling costs and design flexibility play a significant role in determining the feasibility of a manufacturing method. Thermoformed parts boast similar tooling costs; however, due to capacity constraints, multiple tooling sets are often required to produce the same quantity of parts.

Mold in Color

One notable advantage of thermoforming over fiberglass molding in design is the ability to mold parts directly in color and texture. Thermoforming allows for integrating solid colors, material and unique textures directly into the mold, eliminating the need for additional painting processes. This streamlines production and ensures consistent color and texture across all parts, enhancing aesthetic appeal and reducing variability. Additionally, since the part is through-colored, a scratched part is generally less noticeable since vs the off-white substrate color of composites. 

Dimensional Stability

Thermoformed parts exhibit superior dimensional stability, maintaining precise shapes and dimensions throughout production. This consistency is crucial in industries where accuracy and uniformity are paramount, offering manufacturers a reliable solution for their design requirements.


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Choosing between thermoforming and fiberglass molding depends on your specific manufacturing requirements and application needs. Thermoforming is favored in transportation, marine, heavy equipment, recreational vehicles, and medical equipment industries, where lightweight, durable parts are essential. 

By carefully evaluating factors such as durability, weight reduction, production speed, recyclability, chemical resistance, safety, tooling costs, design flexibility, and industry-specific applications, you can make an informed decision to achieve optimal results in your manufacturing processes.

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