Fiberglass – The Unsung Hero Behind The Steel Skeleton Of Engineering Plastics

Commonly used fiberglass in the modified plastics industry can be classified by composition and form:

 

Classification by Chemical Composition:

* **Alkali-Free Fiberglass (E Fiberglass):** Alkali content <1%, balanced insulation, strength, and water resistance; highest production volume; used in wind turbine blades, PCBs, and plastic modification.

* **Medium-Alkali Glass Fiber (C Glass Fiber):** Alkali content 6%-12%, good acid resistance, weaker insulation, low cost; used for chemical corrosion protection and asphalt waterproofing.

 

Classification by Form:

* **Continuous Untwisted Long Glass Fiber:** Glass fibers drawn into bundles and wound into rolls for use in textile processing and structural reinforcement.

* **Cut-Off Glass Fiber:** Glass fiber rolls that are cut short after surface treatment; a major variety for plastic modification and reinforcement.

* **Flat Glass Fiber:** A special variety; glass fibers with an elliptical cross-section controlled during the drawing process; available in long and cut-off forms. It exhibits unique performance in applications.

 

How Fiberglass Creates the "Steel and Iron Bones" of Plastics

 

The core reason why fiberglass is the perfect partner for engineering plastics lies in its ability to compensate for the performance shortcomings of pure plastic resins through a synergistic "fiber-resin" effect and cohesive force transfer.

 

Mechanical Strengthening: Like adding "steel bars" to plastics, tensile strength can increase by 20% to 100%, and impact toughness can even approach metal levels;

Deformation Resistance: It inhibits resin shrinkage, making products less prone to warping under high temperatures and stress, with shrinkage rates controlled to a minimum of 0.15%;

Cost Balancing: Compared to pure engineering plastics, fiber-reinforced materials can achieve high performance requirements at a lower cost. For example, using long fiberglass PA to replace metal in automotive parts reduces weight by 50% while lowering costs by 30%.

 

What are the Unique Aspects of Different Types of Fiberglass in Plastics?

 

However, different forms of fiberglass bring vastly different effects to plastics. Choosing the right type can double the product's performance; choosing the wrong type may result in problems such as exposed fiberglass and easy breakage. Commonly used glass fibers mainly include three types: long glass fibers, short glass fibers, and flat glass fibers. They differ significantly in morphology, performance, processing methods, and application scenarios.

 

Long glass fibers act like "solid steel bars," forming a continuous network within the resin, efficiently transferring stress. This is why their impact strength is 50% to 100% higher than that of short glass fibers.

Short glass fibers act like "crushed stone," uniformly dispersed but with limited length, suitable for applications requiring high isotropy.

Flat glass fibers act like "thin steel sheets," with a thickness of 3-10 μm and a width of 50-200 μm, allowing for a 3-5 times larger contact area with the resin compared to round glass fibers, resulting in a significantly improved surface finish.

 

01

Appearance Characteristics

① Flat Glass Fiber Filled with PC

Due to its flat, ribbon-like structure, the contact area with PC resin is 3-5 times larger than that of round glass fibers of the same weight, resulting in a smoother fiber-resin interface transition. Combined with the low surface roughness achieved through a special drawing process, this leads to a higher surface gloss (measured at a 60° angle).

 

② Short Glass Fiber Filled PC: The short and uniformly dispersed fibers result in gentler light scattering. However, the interface between the round cross-section fiber and resin still exhibits slight reflection, leading to a gloss level slightly lower than flat glass fiber, typically between 70 and 80. The floating fiber effect places higher demands on the molding process.

 

③ Long Glass Fiber Filled PC: Long fibers (6-12mm) tend to aggregate during processing, and the fiber-resin interface has tiny gaps due to the "skeleton effect," causing diffuse reflection of light in these areas. The gloss level is only 50-60, resulting in a slightly matte surface, making it more suitable for functional products such as engineering machinery housings.

 

02

 

Mechanical Properties:

The longer the glass fiber in the plastic, the more bonding points between the glass fiber and resin, resulting in better strength. Long glass fiber plastics can be considered the undisputed "strength champions." Data shows that, at the same content, the tensile strength of long glass fiber reinforced PA is 20%-30% higher than that of short glass fiber, and the notched impact strength is 50%-60% higher, making it particularly suitable for long-term stress components such as automotive bumpers and motor fan blades.

 

Short glass fibers excel in "balance." While slightly weaker in strength, they exhibit good isotropy, resulting in minimal performance differences across different directions, making them suitable for precision parts such as gears and connectors.

 

Flat glass fibers, on the other hand, offer slightly improved "lateral toughness." Using flat glass fibers to reinforce silicone copolymer PC in mobile phone casings improves drop resistance by 40% and avoids the defect of "exposed glass fibers."

 

03

Dimensional Stability Performance

 Long glass fibers' "skeleton effect" effectively holds the resin in place, achieving a shrinkage rate as low as 0.15% in the flow direction. However, the vertical shrinkage difference is significant, making large-area flat panels prone to warping.

Short glass fibers shrink more uniformly, making them suitable for small to medium-sized parts.

Flat glass fibers, with their flat structure, offer more balanced restriction on in-plane shrinkage, making them an ideal choice for automotive interior panels.

 

Appropriate Application: Putting the Right Fiber in the Right Place

 

There is no best glass fiber, only the right choice. Let's look at the "main battlefields" of different glass fibers.

 

Long Glass Fiber: The "Leader" of Heavy Industry For components requiring long-term impact and load resistance, such as car chassis brackets, construction machinery housings, and ski bindings, long glass fiber is the ideal choice. Verton's long glass fiber composite cable supports remain corrosion-free for ten years in underground environments, completely solving the rust problem of metal supports.

 

Short glass fiber: The "king of cost-effectiveness" in everyday consumer goods. For cost-sensitive yet fundamentally strong components like washing machine drums, air conditioner compressor brackets, and electronic connectors, short glass fiber reinforcement is perfectly suited.

 

Flat glass fiber: A combination of aesthetics and performance. For components requiring both shock resistance and aesthetics, such as mobile phone casings, laptop A-sides, and automotive interior panels, flat glass fiber achieves a mirror-like surface while maintaining sufficient strength even with a wall thickness of only 0.8mm.