Bonding and sealing polyethylene tanks using MMA adhesive

As a manufacturer of tanks used for things such as water and wastewater collection, the moulding company was frequently discovering blow holes in its tanks, sometimes up to 2.5cm in size. These tanks are typically made of LDPE and are blow moulded into shape. LDPE has poor adhesion properties due to its low surface energy, and is ordinarily difficult to bond.

Keen to help the company find a solution to its problem, the SCIGRIP team rose to the challenge.

Getting a deeper understanding of the problem was the first step. For these tanks, holes smaller than 1.6mm can result in leaks that lead to the entire tank being scrapped, particularly those used in recreational vehicles (RVs) for wastewater storage. As these holes can be common in the manufacturing process, finding a way to repair the holes would help the moulding company avoid the significant cost implications of wasted materials and production disruption.

The SCIGRIP team suggested the company use SG400LSE to effectively repair the tanks. This two-part translucent MMA (10:1) can bond slippery, low surface energy plastics including polyethylene and polypropylene with minimal surface preparation. As SG400LSE is applied more often in the field and in a broader range of applications, even more successes are expected.

With everyone involved set on SG400LSE, a period of trialling the material began, involving tests on a black wastewater tank, typically used in RVs, to assess the effectiveness of patching and hole-filling (plugging) to combat the problem.

Using SG400LSE to create patches and plugs

The SCIGRIP team approached the problem in two ways: patching for larger holes and plugging for smaller ones.

To set up the patching trial, 2.5cm holes were drilled into the tank. These holes were drilled into what would be the bottom of the tank as it would be installed in a RV in order to simulate damage that might be experienced while traveling. SG400LSE was applied to the tank, completely encircling each hole. A second piece of LDPE, approximately 3mm thick, was then pressed onto the SG400, encircling the hole and forming a seal.

To set up the plugging trial, 3mm and 6.35mm holes were drilled into what would be the bottom of the tank. These holes were meant to simulate a worst-case scenario of what could occur during blow moulding. SG400LSE was dispensed into these holes, completely filling the holes and creating plugs.

The tank was left overnight so that the patched and filled holes could cure. The following day, the tank was filled and positioned vertically to create maximum water pressure. Both repair solutions resulted in no leaking, indicating successful repairs.

SG400LSE was highly effective at repairing the holes and ultimately enabled the manufacturers to improve the quality of their product and make significant savings as a result of reduced scrappage and improved productivity.