When a car window breaks or cracks, it can be a frustrating and inconvenient situation. Replacing the window with the right type of plastic is important to restore visibility and safety. The best type of plastic to use depends on the specifics of the damage and your needs. In this comprehensive guide, we will examine the different types of plastic available for broken auto glass windows, the pros and cons of each, and provide recommendations to help you choose the optimal plastic replacement.
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Causes of Broken Car Windows
Before exploring plastic solutions, it’s helpful to understand what causes car windows to break in the first place. Some of the most common causes include:
- Rocks or road debris hitting the glass at high speeds
- Doors or objects impacting the window
- Temperature changes causing contraction and expansion
- Stress cracks from vibration over time
- Attempted break-ins and vandalism
- Improper installation or seal failure
- Manufacturing defects in the glass
Side and rear windows tend to be more vulnerable than windshields since they are not laminated. However, windshields can still crack from impacts. The severity of the damage ranges from minor chips and cracks to completely shattered glass.
Types of Plastic for Repairing Broken Windows
There are three main types of plastic suitable for mending cracked or broken car windows:
- Acrylic: A rigid, transparent thermoplastic often used as a glass substitute. It can be molded or extruded into sheets.
- Polycarbonate: An incredibly strong, impact-resistant plastic. Polycarbonate sheets are a popular auto glass repair option.
- PVB: Polyvinyl butyral is a resin adhesive film used to bind layers of glass and plastic. It is a key component of laminated safety glass in windshields.
Next, we’ll examine the characteristics, pros and cons, and costs of each type in greater detail.
Acrylic Plastic
Acrylic glass, often referred to by brand names like Plexiglas or Lucite, is a transparent plastic composed of methyl methacrylate (MMA). Some key properties include:
- Excellent optical clarity and light transmission.
- More prone to scratching and abrasion than glass.
- Half the weight of glass.
- Resists weathering and yellowing from UV radiation.
- Can crack under heavy impact.
- Available in a diversity of colors and tints.
Some benefits of using acrylic plastic for fixing broken car windows are:
- Lightweight and easy to install
- Transparent replacement maintains visibility
- Impact-resistant for most minor cracks
- Inexpensive compared to polycarbonate
- Easier to cut, drill, and shape
Potential downsides of acrylic include:
- Prone to scratching
- Not as strong as polycarbonate
- Higher long-term maintenance
- Can develop cracks from heat and cold
- Does not offer the same noise insulation as glass
Acrylic sheets typically cost *$15 to $30* per square foot for car window repairs.
Polycarbonate Plastic
Polycarbonate is an incredibly strong, impact-resistant thermoplastic. It offers exceptional durability for replacement auto glass. Some benefits of polycarbonate are:
- Extreme impact strength and shatter resistance
- Excellent optical quality with high light transmission
- Weighs half as much as glass
- Withstands extreme temperatures from -40 to 160°C
- UV filtering options available
Potential disadvantages include:
- Higher cost than acrylic
- Susceptible to scratching unless surface coated
- Not as stiff as glass, subject to flexing
- Difficult to cut and install without cracking
Polycarbonate typically runs *$50 to $100* per square foot, making it a more expensive choice.
PVB Plastic Film
Polyvinyl butyral (PVB) plastic film is commonly used as the inner lamination layer in safety glass for windshields. PVB has these beneficial properties:
- Excellent adhesive properties to bond glass and polycarbonate sheets together
- Impact absorption and crack resistance
- Blocks over 99% of UV rays
- Improves noise insulation
- Increases strength and provides structural rigidity
PVB laminated plastic is not used on its own for replacing windows, but rather for bonding and strengthening repairs. It costs approximately *$3 to $8* per square foot.
Comparing Strength of Plastics
When evaluating the best plastic option for your repair, mechanical strength is often a top concern. Here is how the plastics compare:
| Plastic Type | Tensile Strength | Impact Resistance |
|---|---|---|
| Acrylic | 7,000 psi | Poor |
| Polycarbonate | 9,500 psi | Excellent |
| Glass | 6,000 psi | Fair |
As you can see, polycarbonate is the strongest plastic for impact resistance and durability. Acrylic is considerably weaker but still more flexible and impact-absorbent than glass.
Recommendations by Car Window Type
With an overview of the plastic options, we can now make recommendations based on the specific window needing repair:
Side and Rear Windows
For side and rear car windows that commonly shatter, polycarbonate plastic is the best choice for repairing damage. Reasons why:
- Polycarbonate prevents the entire window from requiring replacement if damaged again.
- It is many times stronger than acrylic and better at stopping objects from penetrating the car.
- Polycarbonate withstands weather extremes without cracking.
- It can be coated to resist scratching and UV damage over time.
Polycarbonate does cost more upfront but lasts much longer than acrylic before needing replacement. For security and longevity, polycarbonate is worth the extra investment.
Windshields
Windshields require a different approach since they consist of two sheets of glass bonded by a PVB plastic interlayer. Small cracks and chips can often be safely repaired with acrylic or polycarbonate resin injections. However, extensive damage will require a complete replacement using factory-grade laminated glass. Reasons include:
- Laminated construction better withstands collisions and protects occupants.
- Only auto-grade PVB and glass provide adequate optical clarity for driver visibility.
- Improper windshield materials can compromise airbag deployment in a crash.
- Replacement ensures proper fitment and seals against the vehicle frame.
While cheaper than a professional replacement, low-grade plastics cannot replicate the safety of a new OEM windshield. Work only with reputable glass shops for windshield installations.
Professional vs. DIY Installation
Once you’ve selected the right plastic, the next decision is whether to tackle the installation yourself or hire a professional. Here are some things to consider:
DIY Replacement
Doing it yourself can save money but has some downsides:
- Difficult getting clean cuts and proper fit without special tools.
- Easy to crack polycarbonate if mishandled.
- Improper sealing can lead to leaks, fogging, and wind noise.
- Limits on quality of plastics available to consumers.
Overall, DIY replacement works fine for minor damage to side windows using basic acrylic. However, polycarbonate and windshield replacements are best left to professionals.
Professional Installation
Hiring an auto glass shop has advantages including:
- Experts can source high-grade OEM replacement glass.
- Proper urethane sealing prevents leaks.
- Finished appearance is smooth and professional.
- Reduced risk of cracks and rework.
- Specialist tools for clean cuts and fit.
- Access to PVB laminate bonding for windshields.
Professional installation costs range from *$100 to $300* on average depending on glass size and type. This added expense gets you superior results and workmanship.
Conclusion
When faced with a broken car window, polycarbonate plastic provides the strongest repair option for side and rear glass. Acrylic suffices for minor cracks but lacks durability. Windshields require factory-laminated glass for proper safety and optics. Where possible, have a professional auto glass technician install the new plastic or glass material. This ensures a higher quality fit and finish. With the right replacement plastic and installation, you can get your car windows looking good as new.