With the advent of hull side windows on most cruisers and yachts, designers and engineers must decide between using either acrylic or glass, whether tempered or in laminated form. Both Acrylic and laminated glass are transparent materials capable of withstanding high impact and weathering under all conditions per ISO 12216, which is ideal for these vessels.
Laminated glass is manufactured using a different method, principally created using numerous layers of float glass fused together, interleaved with sheets of an adhesive polymer such as PVB. This makes the assembly very strong. Nevertheless, polymers have evolved considerably and are now available in new formulations surpassing the characteristics of glass.
Acrylic is a polymer with excellent characteristics, offering superior formability, yet delivering excellent optical quality. Key advantages are outlined below:
1. Impact Resistance: Excellent
Acrylic has a higher impact strength than glass and does not shatter when exposed to high strains or blunt force. The crack resistance is especially valuable when maneuvering yachts close to docks. This is just one advantage that explains why acrylic is used for viewing ports on deep sea submarines.
Furthermore, laminated glass is also subject to delamination, whereupon the bonding between layers fails, displaying unsightly patterns known as “traveling air pockets”.Aside from being unsightly, over time these air pockets can seriously diminish visibility around the edges of the affected transparencies.
2. Weight: Less Than 50%
At less than half the weight of glass — (SG: 1.19 vs. 2.45) — acrylic is an excellent alternative, especially where weight plays a key factor in design. With current trends erring towards operating more efficiently and implementing environmentally conscious manufacturing processes for vehicles and boats, designers are becoming ever more focused on shedding as much weight as possible to achieve greater performance and fuel efficiency.
3. Cost: Substantially Lower
The rule of thumb is that flat unprocessed glass is less expensive than acrylic. However, tempered glass will be about equivalent, and formed and/or laminated glass will be far costlier to produce than acrylic.
If a window is to have a more defined shape, the forming tools for glass are usually steel or ceramic, while acrylic only requires fiberglass reinforced resin. As such, the difference in tooling costs are substantial; a consideration which becomes far more important for low-volume production.
4. Formability: Highly Versatile
Although glass can be formed into curved shapes, due to its restrictive malleability, the finished shape will be quite limited, with complex shapes being far more challenging to achieve. By contrast, acrylic can be formed into far more radical compound shapes with ease, yet are able to retain excellent optical properties with minimal aberrations.
5. Portlights: Ease of Installation
Acrylic has a higher impact strength than glass and does not shatter when exposed to high strains or blunt force. The crack resistance is especially valuable when maneuvering yachts close to docks. This is just one advantage of why acrylic is used for viewing ports on deep sea submarines.
Furthermore, laminated glass is also subject to delamination, whereupon the bonding between layers fails, displayed as unsightly patterns known as “traveling air pockets”. Aside from being unsightly, over time these air pockets can seriously diminish visibility around the edges of the affected transparencies.
5. Optical Transmission: Up to 15% Better
Acrylic transmits more light than glass; in fact, up to 92% of visible light is transmitted through the acrylic. By contrast, mineral glass transmits between 80-90%, depending on the type.
6. Thermal Conductivity and UV Block: Superior
Thermal conductivity in acrylic is lower than laminated glass. This is advantageous for insulation, such as skylights, resulting in lower running costs for heating and air-conditioning. New acrylic formulations are now capable to offer 99% UV blocking and approximately 35% of IR dependent on the tint being used.
This also has the added advantage of protecting the adhesives used to bond the window in its receptacle without the use of a blackout strip, known as a Frit. Furthermore, these specialty grades also protect interior electronic components and upholstery from fading.
Piedmont Marine Grade® SB™ (Solar Block) is a cast acrylic sheet with approved protection against UV radiation. This product helps prevent degradation of materials by blocking harmful UV rays. PMG® SB™ has been tested and approved by the Sika® Corporation for bonding and sealing Organic Windows Systems in the marine industry.
PMG® SB™ has UV blocking (400 nm), which makes PMG® SB™ 62.5% better than standard acrylic glazing. In addition, the UV blocking (below 400 nm) blocks 100% of UV-A range radiation.
7. Scratch Resistance: Approaching Glass
The surface of the acrylic is softer and more easily scratched than mineral glass. However, new technologies have been developed where a silicate hard coating is applied to the exterior surface of acrylic transparencies. This affords far superior protection, thus resisting most scratches and making acrylic impervious to chemical attacks. Nevertheless, as with glass, if the transparency is compromised the entire window must be replaced.
In summation, Acrylic is the dominant solution for cruisers and yachts in need of durable, cost-effective and high-quality window materials.