Anthony M. Sirignano's research while affiliated with University of Missouri and other places

Plastic lumber is being used to replace wooden lumber in some construction applications, especially in outdoor applications where the plastic lumber is presumed to weather better than the wood. However, the structural properties of the plastic lumber are not well understood, and the use of plastic lumber in structural applications is not authorized in the common building codes. Contractors who use plastic lumber in structural applications such as outdoor decks are in most cases violating the building codes. In this research effort, standard 1 2 6 tongue-in-grove plastic lumber planks were tested for many different structural properties. The tests were conducted at m 23.3°C to simulate winter conditions, and at 40.6°C to simulate summer conditions. In all cases the high temperature strength and stiffness was lower than at low temperature, so the high temperature values would determine the allowable strength and stiffness for design. The conclusion was that the plastic lumber is a good structural material, but that it is not appropriate to simply substitute plastic lumber for wooden lumber pieces of the same size in structural applications. The plastic lumber is not as strong and stiff as the wooden lumber, and so larger sizes must be used to obtain the same strength and stiffness. Because of the much lower modulus, compression members made from plastic lumber may need to be of much larger size to resist buckling.

Plastic lumber is being used to replace wooden lumber in some construction applications, especially in outdoor applications where the plastic lumber is presumed to weather better than the wood. However, the structural properties of the plastic lumber are not well understood, and the use of plastic lumber in structural applications is not authorized in the common building codes. In this research effort, standard 2×6 plastic lumber planks were tested for many different structural properties. The plastic lumber tested was a blend of recycled plastic and sawdust. The tests were conducted at −23.3°C to simulate winter conditions, and at 40.6°C to simulate summer conditions. In all cases the high temperature strength and stiffness was lower than at low temperature, so the high temperature values would determine the allowable strength and stiffness for design. The high temperature modulus of the plastic lumber was 5.79, 1.03, and 1.12 GPa in compression, flexure and tension respectively. High temperature strength values were 16.8, 12.0, and 1.45 MPa in compression, flexure and tension respectively. The high temperature shear strength of the plastic lumber was 5.31 MPa. Strength tests were also performed for nail and screw connections typically used with lumber, and the pull-out and lateral load were comparable to wooden lumber. The plastic lumber performed well under sustained load tests at high temperature. Slip resistance tests were performed, and it was found that the plastic lumber is more slippery than wooden lumber, but probably does not represent a safety hazard. The conclusion was that the plastic lumber is a good structural material, but it is not appropriate to simply substitute plastic lumber for wooden lumber pieces of the same dimension in structural applications. Plastic lumber structures must be designed using the structural properties of the plastic lumber.