Wood-plastic composite durability and the compelling case for field testing

Manning Mark J., . and Ascherl Fred M., . and Mankowski Mark E., . (2006) Wood-plastic composite durability and the compelling case for field testing. [Proceedings Paper]

Wood-Plastic Composites WPCsused for decking window and door moldings have experienced dramatic growth in North America over the last several years with annual production increasing at rates greater than 20 per annum since 1998. A key factor contributing to this growth has been the successfully communicated message that they are virtually maintenance free. The common perception being that the wood fiber is encapsulated by the thermoplastic resin minimizing the potential for moisture absorption and inhibiting attack by wood destroying organisms. A number of recent publications have raised concerns about the long-term durability of WpcS - in inparticular when used in unprotected above-ground applications. The fundamentals question is whether or not the Moisture Content MC of the wood component can achieve the minimum level necessary to support fungal decay. Laboratory tests utilized by the WPC industry suggest this is not the case and yield values less than 10 MC- well below the accepted minimum threshold of 25 necessary to initiate and support fungal decay. This paper will describe work which evaluates the MC of the wood component in WPC samples exposed in various field sites with different climatic Scheffer indices. These field results yield a dramatically different picture and show the outer portion of the WPC surface can achieve MC levels in the wood components which are in excess of the 25 threshold. Macroscopic evaluations of untreated WPC material exposed in the field revealed evidence of fungal decay. The use of a preservative treatment such as zinc borate to protect against fungal decay will also be discussed.

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Abstract

Wood-Plastic Composites WPCsused for decking window and door moldings have experienced dramatic growth in North America over the last several years with annual production increasing at rates greater than 20 per annum since 1998. A key factor contributing to this growth has been the successfully communicated message that they are virtually maintenance free. The common perception being that the wood fiber is encapsulated by the thermoplastic resin minimizing the potential for moisture absorption and inhibiting attack by wood destroying organisms. A number of recent publications have raised concerns about the long-term durability of WpcS - in inparticular when used in unprotected above-ground applications. The fundamentals question is whether or not the Moisture Content MC of the wood component can achieve the minimum level necessary to support fungal decay. Laboratory tests utilized by the WPC industry suggest this is not the case and yield values less than 10 MC- well below the accepted minimum threshold of 25 necessary to initiate and support fungal decay. This paper will describe work which evaluates the MC of the wood component in WPC samples exposed in various field sites with different climatic Scheffer indices. These field results yield a dramatically different picture and show the outer portion of the WPC surface can achieve MC levels in the wood components which are in excess of the 25 threshold. Macroscopic evaluations of untreated WPC material exposed in the field revealed evidence of fungal decay. The use of a preservative treatment such as zinc borate to protect against fungal decay will also be discussed.

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Item Type:	Proceedings Paper
Additional Information:	8 ills. 19 refs.
AGROVOC Term:	WOOD
AGROVOC Term:	FUNGI
AGROVOC Term:	BIODETERIORATION
AGROVOC Term:	USA
Geographical Term:	MALAYSIA
Depositing User:	Ms. Norfaezah Khomsan
Last Modified:	24 Apr 2025 05:28
URI:	http://webagris.upm.edu.my/id/eprint/16916

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