Author
Abstract
For further details log on website :
http://www.iranwpc.ir/docs/use_of_recycled_plastics_in_wood_plastic_composites_EN.pdf
Saeed Kazemi Najafi ⇑
Department of Wood and Paper Science and Technology, Natural Resources Faculty, Tarbiat Modares University, Iran
Department of Wood and Paper Science and Technology, Natural Resources Faculty, Tarbiat Modares University, Iran
Keywords:
Wood plastic composites
Waste and recycled plastics Degradation
Physical and mechanical properties
Wood plastic composites
Waste and recycled plastics Degradation
Physical and mechanical properties
Article history:
Received 5 December 2012 Accepted 21 May 2013 Available online 15 June 2013
Received 5 December 2012 Accepted 21 May 2013 Available online 15 June 2013
Abstract
The use of recycled and waste thermoplastics has been recently considered for producing wood plastic
composites (WPCs). They have great potential for WPCs manufacturing according to results of some lim-
ited researches. This paper presents a detailed review about some essential properties of waste and recy-
cled plastics, important for WPCs production, and of research published on the effect of recycled plastics
on the physical and mechanical properties of WPCs.
Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction
Recycled and waste thermoplastics are some of the major com- ponents of global municipal solid waste (MSW) and they present a promising raw material source for WPCs, especially because of the large volume and low cost of these materials. Table 1 shows that waste plastics account for 11.2% of the annual 84.2 thousands tons of the municipal waste stream generated in Tehran during 2006 (Ashori, 2008) and 12.4% of 250 million tons in the USA during 2010 (EPA, 2011).
As given in Table 2, high density polyethylene (HDPE), low den- sity polyethylene (LDPE/LLDPE), polypropylene (PP), Polyethylene terephthalate (PET), polystyrene (PS) and polyvinyl chloride (PVC) are the primary constituents of plastics in MSW. The blend of the mixed waste plastics can be changed depending on the re- gional habits and seasons of a year and on the mode of waste col- lection, also (Chanda and Roy, 2007). Table 2 also shows that only 7.6% of 31 million tons (12.4% of MSW) of generated waste plastics were recycled.
Reutilizing the post-consumed polymeric materials reduces the environmental impact and the consumption of virgin plastics. Most single polymer plastics made from petroleum are relatively easy to recycle. Therefore, with an efficient collection, separation and recy- cling system, discarded plastics can be recycled into new products with only the addition of energy (Jayaraman and Bhattacharya, 2004).
Products manufactured from waste plastics for use are increas- ing, including floor carpets, flower vases, waste paper baskets, park benches, picnic tables (DeWeese, 1998) and plastic lumber (Dutta et al., 1994). Also, recycled plastics can be used in wood plastic composites (WPCs), which use will provide an additional market for recycled plastics. Trex, the largest supplier of wood-plastic composite lumber, purchases an average of over 227,000 kg of plastic scrap each day (Principia Partners, 2002). Winandy et al. (2004) listed some wood plastic composite products using recycled plastics, produced commercially in the USA.
Generally in WPC manufacturing, virgin thermoplastic poly- mers are widely used. The most prevalent polymers are PE, PP, PVC and PS. The waste and recycled plastics have been used for manufacturing WPCs already in 1990s and the use has significantly increased in the developed and developing countries in recent years. This paper presents a detailed review about waste and recy- cled plastics and the research published on the effect of recycled plastic on the physical and mechanical properties of WPCs.
2. Properties of waste and recycled plastics
If the recycled plastics are considered as new materials in WPCs production, it is necessary primarily to understand well the ele- mental and fundamental structure of these materials. By knowing the properties of recycled plastics, the processes for manufacturing WPCs can be well controlled and then the relationship between the properties of recycled plastics and their mechanical aspects can be better understood as well as those of the resulted WPC products.
At the end of the first life cycle of plastic products, or after being re-used several times, plastics can be recycled to yield new poly- meric materials or products. Since recycled plastics may be ob- tained from various sources, having been exposed to different storage and reprocessing conditions, they may therefore exhibit different performance depending on their degradation level. Then the post-consumer plastics waste may contain many grades, colors
⇑ Tel.: +98 122 6253101 3.
E-mail address: skazemi@modares.ac.ir
0956-053X/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.wasman.2013.05.017
Recycled and waste thermoplastics are some of the major com- ponents of global municipal solid waste (MSW) and they present a promising raw material source for WPCs, especially because of the large volume and low cost of these materials. Table 1 shows that waste plastics account for 11.2% of the annual 84.2 thousands tons of the municipal waste stream generated in Tehran during 2006 (Ashori, 2008) and 12.4% of 250 million tons in the USA during 2010 (EPA, 2011).
As given in Table 2, high density polyethylene (HDPE), low den- sity polyethylene (LDPE/LLDPE), polypropylene (PP), Polyethylene terephthalate (PET), polystyrene (PS) and polyvinyl chloride (PVC) are the primary constituents of plastics in MSW. The blend of the mixed waste plastics can be changed depending on the re- gional habits and seasons of a year and on the mode of waste col- lection, also (Chanda and Roy, 2007). Table 2 also shows that only 7.6% of 31 million tons (12.4% of MSW) of generated waste plastics were recycled.
Reutilizing the post-consumed polymeric materials reduces the environmental impact and the consumption of virgin plastics. Most single polymer plastics made from petroleum are relatively easy to recycle. Therefore, with an efficient collection, separation and recy- cling system, discarded plastics can be recycled into new products with only the addition of energy (Jayaraman and Bhattacharya, 2004).
Products manufactured from waste plastics for use are increas- ing, including floor carpets, flower vases, waste paper baskets, park benches, picnic tables (DeWeese, 1998) and plastic lumber (Dutta et al., 1994). Also, recycled plastics can be used in wood plastic composites (WPCs), which use will provide an additional market for recycled plastics. Trex, the largest supplier of wood-plastic composite lumber, purchases an average of over 227,000 kg of plastic scrap each day (Principia Partners, 2002). Winandy et al. (2004) listed some wood plastic composite products using recycled plastics, produced commercially in the USA.
Generally in WPC manufacturing, virgin thermoplastic poly- mers are widely used. The most prevalent polymers are PE, PP, PVC and PS. The waste and recycled plastics have been used for manufacturing WPCs already in 1990s and the use has significantly increased in the developed and developing countries in recent years. This paper presents a detailed review about waste and recy- cled plastics and the research published on the effect of recycled plastic on the physical and mechanical properties of WPCs.
2. Properties of waste and recycled plastics
If the recycled plastics are considered as new materials in WPCs production, it is necessary primarily to understand well the ele- mental and fundamental structure of these materials. By knowing the properties of recycled plastics, the processes for manufacturing WPCs can be well controlled and then the relationship between the properties of recycled plastics and their mechanical aspects can be better understood as well as those of the resulted WPC products.
At the end of the first life cycle of plastic products, or after being re-used several times, plastics can be recycled to yield new poly- meric materials or products. Since recycled plastics may be ob- tained from various sources, having been exposed to different storage and reprocessing conditions, they may therefore exhibit different performance depending on their degradation level. Then the post-consumer plastics waste may contain many grades, colors
⇑ Tel.: +98 122 6253101 3.
E-mail address: skazemi@modares.ac.ir
0956-053X/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.wasman.2013.05.017
For further details log on website :
http://www.iranwpc.ir/docs/use_of_recycled_plastics_in_wood_plastic_composites_EN.pdf
No comments:
Post a Comment