PVC Introduction
PVC Introduction
Due to the complexities involved in non-bituminous flexible membranes, “generic” application specifications and details are not possible. This section of the manual contains both an overview of the products, their composition, usage, and design considerations, and the accepted membrane manufacturer's written submissions. In all cases, the membrane manufacturer should be contacted for further recommendations and details.
In order to formulate materials to satisfy the requirements of a roof membrane, the manufacturer must ensure:
- Strict Quality Control
- Proper Mix of Ingredients
- Consistency of Batches
- Minimum Physical Properties are Obtained
The chemical formulations of specific flexible membranes can be complex, but the end product can generally be defined as either a THERMOSET (Section 6.1) or THERMOPLASTIC (Section 6.2).
1 Plastomeric Membranes
Thermoplastic materials are defined as polymers which soften when heated and harden when cooled. This process is repetitive provided the material is not heated above the point at which decomposition occurs. No cross-linking or vulcanization occurs. In addition to heat welding, some materials can be solvent welded. These welds develop bonding strengths equalling or surpassing the strength of the base materials.
Thermoplastics materials used for roof membranes include:
- PVC (Polyvinyl Chloride)
- EIP (Ethylene Interpolymers)
- ECB (Ethylene Copolymer Bitumen)
- TPO (Thermoplastic Polyolefins)
- EPR (Ethylene Propylene Rubber)
2 PVC (Polyvinyl Chloride)
PVC is a thermoplastic material produced through the polymerization of vinyl chloride, resulting in a relatively hard, resinous material. This material is then formulated with compounds, such as plasticizers and stabilizers, depending on the physical properties required for end use. PVC formulations have been developed to suit numerous commercial and industrial applications.
PVC roof systems are single-ply membranes available either non-reinforced or reinforced with polyester fabric or glass fibres, and in thicknesses usually ranging from 1.2 mm to 2.0 mm, depending on the manufacturer. Non-reinforced PVC membranes may typically exhibit excessive shrinkage characteristics, thus their use is often discouraged. The membrane may be applied loose-laid and ballasted, mechanically fastened, or fully adhered. Seams are heat or chemically welded (see manufacturer’s requirements).
PVC membrane should conform to CGSB 37-GP-54M 1979, “Roofing and Waterproofing Membrane, Sheet Applied, Flexible, Polyvinyl Chloride” which lists two types of membrane, according to manufacture:
- Type 1
- non-reinforced
- Type 2
- reinforced
and four classes, according to end use:
- Class A
- non-exposed roofing
- Class B
- exposed roofing
- Class C
- waterproofing
- Class D
- flashing membrane asphalt compatible
This standard covers requirements such as “thickness, lap joint strength, permeability, tensile strength, elongation at break, low temperature flexibility, water absorption, resistance to accelerated weathering, dimensional change after stress relaxation, and cone penetration”
PVC membranes should be applied in conformance with CGSB 37-GP-55M 1979, “Application of Sheet Applied Flexible Polyvinyl Chloride Roof Membrane” and the membrane manufacturer’s printed instructions.