- Email: [email protected]
wood polymer composites
May 2002
polyethylene, polypropylene and ABS, as well as polymers like PA6, PA6/6, PBT, PET and PPO. Contact: BKG Bruckmann & Kreyenborg Granuliertechnik GmbH, Hessenweg 3, D-481 5 7 Miinstel; Germany; tel: +49-2.51-26501-O; fax: +49-251-26501-98; e-mail: [email protected]
MARKETS Markets growing for speciality additives in natural/wood polymer composites The market size for speciality additives used in natural and wood fibre polymer composites reached about 19.1 million kg (42 million lb) in 2001, valued at US$57 million. Use of these speciality additives is still in its infancy, but the market is expected to double in value by 2006, according to forecasts in a recently released study from Principia Partners. Formulation enhancements are required to significantly increase performance and improve throughput and cost economics for these composites, and consequently performance-enhancing additives will expand their market acceptance and share. The specific materials and amount of additives required to sufficiently stabilize and improve these natural composites are still under development and evaluation by the Specialty Additives in industry, reports Natural/Wood Polymer Composites. Colorants find widespread, almost universal, usage across all applications, and consequently represent the single largest category of speciality additives consumed in these natural fibre based composites. Lubricants make up the second largest category, primarily based on the increasing role for stearate-based chemistry used at many composite decking producers. Coupling agents like maleated polyolefins are gaining acceptance as the key to improving adhesion between polymer and fibre, thereby increasing the strength of the composite. Currently the high price of light stabilizers, even at very low loading levels, appears to be limiting their usage in these composites. Composite producers find the price too high to
02002 Elsevier Science
Additives for Polymers
justify using UV protection, and question whether the additive can properly protect colour fastness over many years, the report says. However, Principia expects increased use of UV absorbers and hindered amines, as customer expectations for longer lasting colour durability will drive future demand. Heat stabilizers and impact modifiers are primarily used by the few PVC-based wood composite producers active in the business today. All other additives, including antimicrobial agents, chemical foaming agents (CFAs) and flame retardants will find greater use in the future. A significant amount of R&D activity, specifically in antimicrobials and blowing agents, is already underway at many wood fibre-based polymer composite producers, primarily for decking and other building products. CFAs are largely developmental at this stage. Some composite producers are experimenting with formulations containing these additives to reduce weight, increase yield and provide greater ‘wood like’ attributes through the cellular structure imparted by CFAs. The report estimates that the market for additives for natural tibre and wood composites will grow from 2001’s level of 19.1 million kg to 39.5 million kg, valued at more than $120 million, by 2006. The 16% average annual growth rate over this five-year period exceeds the expected rate of growth for the composite industry overall, due to the greater usage of the materials. Several major application areas within building products, including decking and window/door lineals, will use more antimicrobials to prevent mildew staining, more CFAs for lighter weight and thinner walls, coupling agents for superior strength, and colorants/UV stabilizers for improved colour fastness. While these additives generally add to the overall formulation cost, the performance improvements are deemed necessary to improve the long-term viability in current and targeted uses, the report says. According to Lou Rossi of Principia Partners, many of the major plastics additive suppliers are seeking to serve this market segment, and require a greater understanding of the formulation needs and changing technical requirements among composite producers. He concludes that
9
Additives.for
May 2002
Polymers
speciality plastics additives in wood-based composites are one of the most dynamic segments of the plastics industry. Several additive types, including colorants and lubricants, are reasonably well established but other additives have only limited penetration to-date. Opportunities therefore exist for additive suppliers to work with composite producers to utilize more additives in their formulations. The full report is available to subscribers for US$9000. Contact: Principia Partners, PO Box 611, Exton, PA 19341, USA; tel: +I-610-458-3738; fauc: +I484-214-0172; e-mail: [email protected]; URL: www.principiaconsulting.com
TECHNICAL
BRIEFS
Processing and properties of polypropylene composites with high filler content Mineral fillers such as talc and silica are frequently used with polypropylene (PP) as extenders to reduce costs, increase stiffness and decrease shrinkage. However, the non-polar nature of PP limits its adhesion and compatibility with other materials, and therefore a variety of organic compounds, including fatty acids, phosphate esters, silanes and titanates, have been employed as coupling agents to improve interfacial interaction, adhesion and dispersion between the filler and matrix. A study by Z. Ren, R.A. Shanks and T.J. Rook of RMIT University in Melbourne, Australia, has investigated the processing conditions for PP and PP-5% ethylene copolymer with high filler contents (up to 43.8 vol%), and the use of a titanate coupling agent to improve mechanical properties. Neopentyl(diallyl)-oxy-tri(diocty1 pyrophosphato)titanate, with a large functional group, was selected because it is an effective dispersant as well as improving interaction. A lower molar mass silicone coupling agent, with no functional groups, was also tested for comparison with the titanate. The tillers used were calcium carbonate (mean particle diameter: 1.55 urn), talc (17.02 pm) and barium sulphate (4.08 pm). The fillers
10
were surface modified by high speed mixing with 0.3 wt% titanate or 0.4 wt% silicone diluted in hexane. A range of composites were prepared in a single screw extruder with both treated and untreated fillers; filler contents ranged from O-43.8 vol%, as determined by thermogravimetry. The authors observed that surface modification of the fillers facilitated extrusion and reduced brittleness while providing hard composites with high density (Polymers & Polymer Composites, Vol. 10, No. 2, 2002, pp 173-183). Treatment of the fillers with titanate or silicone allowed much higher filler contents than could otherwise be achieved; without modification, filler content is limited to about 10 ~01% maximum in PP. The tensile properties were measured and related to composition, filler type and surface treatment. In highly filled (> 15 ~01%) PP and co-PP composites, Young’s modulus increased with increasing volume fraction of filler, regardless of the different sizes and chemical properties of the fillers. The maximum modulus achieved was nearly 4.5 GPa for 43.8 ~01% talc-filled PP, compared with a Young’s modulus of 1.3 GPa for the unfilled polymer. Talc-filled composites showed much higher Young’s modulus values than for CaCO, or BaSO, because of the platelike shape of the talc particles. In general, yield stress and toughness decreased with increasing filler volume fraction. Comparing the two different coupling agents, the study found that the use of titanate as a reactive coupling agent enhanced the modulus at high filler loadings in some cases, and improved the yield stress and toughness in most cases. However, the nonreactive silicone coupling agent has been found to be a much more effective modifier, improving modulus, yield stress and toughness in most cases, and achieving significantly higher values of these properties than with titanate. While the use of titanate was found to improve particle-matrix interaction, silicone acted as a dispersant, decreasing particle-particle interactions. The authors therefore conclude that, for PP-based composites, the structural modification of the composites - the aggregation and dispersion of filler - is more important than interfacial modification as far as improving the tensile properties is concerned.
02002 Elsevier Science
polyethylene, polypropylene and ABS, as well as polymers like PA6, PA6/6, PBT, PET and PPO. Contact: BKG Bruckmann & Kreyenborg Granuliertechnik GmbH, Hessenweg 3, D-481 5 7 Miinstel; Germany; tel: +49-2.51-26501-O; fax: +49-251-26501-98; e-mail: [email protected]
MARKETS Markets growing for speciality additives in natural/wood polymer composites The market size for speciality additives used in natural and wood fibre polymer composites reached about 19.1 million kg (42 million lb) in 2001, valued at US$57 million. Use of these speciality additives is still in its infancy, but the market is expected to double in value by 2006, according to forecasts in a recently released study from Principia Partners. Formulation enhancements are required to significantly increase performance and improve throughput and cost economics for these composites, and consequently performance-enhancing additives will expand their market acceptance and share. The specific materials and amount of additives required to sufficiently stabilize and improve these natural composites are still under development and evaluation by the Specialty Additives in industry, reports Natural/Wood Polymer Composites. Colorants find widespread, almost universal, usage across all applications, and consequently represent the single largest category of speciality additives consumed in these natural fibre based composites. Lubricants make up the second largest category, primarily based on the increasing role for stearate-based chemistry used at many composite decking producers. Coupling agents like maleated polyolefins are gaining acceptance as the key to improving adhesion between polymer and fibre, thereby increasing the strength of the composite. Currently the high price of light stabilizers, even at very low loading levels, appears to be limiting their usage in these composites. Composite producers find the price too high to
02002 Elsevier Science
Additives for Polymers
justify using UV protection, and question whether the additive can properly protect colour fastness over many years, the report says. However, Principia expects increased use of UV absorbers and hindered amines, as customer expectations for longer lasting colour durability will drive future demand. Heat stabilizers and impact modifiers are primarily used by the few PVC-based wood composite producers active in the business today. All other additives, including antimicrobial agents, chemical foaming agents (CFAs) and flame retardants will find greater use in the future. A significant amount of R&D activity, specifically in antimicrobials and blowing agents, is already underway at many wood fibre-based polymer composite producers, primarily for decking and other building products. CFAs are largely developmental at this stage. Some composite producers are experimenting with formulations containing these additives to reduce weight, increase yield and provide greater ‘wood like’ attributes through the cellular structure imparted by CFAs. The report estimates that the market for additives for natural tibre and wood composites will grow from 2001’s level of 19.1 million kg to 39.5 million kg, valued at more than $120 million, by 2006. The 16% average annual growth rate over this five-year period exceeds the expected rate of growth for the composite industry overall, due to the greater usage of the materials. Several major application areas within building products, including decking and window/door lineals, will use more antimicrobials to prevent mildew staining, more CFAs for lighter weight and thinner walls, coupling agents for superior strength, and colorants/UV stabilizers for improved colour fastness. While these additives generally add to the overall formulation cost, the performance improvements are deemed necessary to improve the long-term viability in current and targeted uses, the report says. According to Lou Rossi of Principia Partners, many of the major plastics additive suppliers are seeking to serve this market segment, and require a greater understanding of the formulation needs and changing technical requirements among composite producers. He concludes that
9
Additives.for
May 2002
Polymers
speciality plastics additives in wood-based composites are one of the most dynamic segments of the plastics industry. Several additive types, including colorants and lubricants, are reasonably well established but other additives have only limited penetration to-date. Opportunities therefore exist for additive suppliers to work with composite producers to utilize more additives in their formulations. The full report is available to subscribers for US$9000. Contact: Principia Partners, PO Box 611, Exton, PA 19341, USA; tel: +I-610-458-3738; fauc: +I484-214-0172; e-mail: [email protected]; URL: www.principiaconsulting.com
TECHNICAL
BRIEFS
Processing and properties of polypropylene composites with high filler content Mineral fillers such as talc and silica are frequently used with polypropylene (PP) as extenders to reduce costs, increase stiffness and decrease shrinkage. However, the non-polar nature of PP limits its adhesion and compatibility with other materials, and therefore a variety of organic compounds, including fatty acids, phosphate esters, silanes and titanates, have been employed as coupling agents to improve interfacial interaction, adhesion and dispersion between the filler and matrix. A study by Z. Ren, R.A. Shanks and T.J. Rook of RMIT University in Melbourne, Australia, has investigated the processing conditions for PP and PP-5% ethylene copolymer with high filler contents (up to 43.8 vol%), and the use of a titanate coupling agent to improve mechanical properties. Neopentyl(diallyl)-oxy-tri(diocty1 pyrophosphato)titanate, with a large functional group, was selected because it is an effective dispersant as well as improving interaction. A lower molar mass silicone coupling agent, with no functional groups, was also tested for comparison with the titanate. The tillers used were calcium carbonate (mean particle diameter: 1.55 urn), talc (17.02 pm) and barium sulphate (4.08 pm). The fillers
10
were surface modified by high speed mixing with 0.3 wt% titanate or 0.4 wt% silicone diluted in hexane. A range of composites were prepared in a single screw extruder with both treated and untreated fillers; filler contents ranged from O-43.8 vol%, as determined by thermogravimetry. The authors observed that surface modification of the fillers facilitated extrusion and reduced brittleness while providing hard composites with high density (Polymers & Polymer Composites, Vol. 10, No. 2, 2002, pp 173-183). Treatment of the fillers with titanate or silicone allowed much higher filler contents than could otherwise be achieved; without modification, filler content is limited to about 10 ~01% maximum in PP. The tensile properties were measured and related to composition, filler type and surface treatment. In highly filled (> 15 ~01%) PP and co-PP composites, Young’s modulus increased with increasing volume fraction of filler, regardless of the different sizes and chemical properties of the fillers. The maximum modulus achieved was nearly 4.5 GPa for 43.8 ~01% talc-filled PP, compared with a Young’s modulus of 1.3 GPa for the unfilled polymer. Talc-filled composites showed much higher Young’s modulus values than for CaCO, or BaSO, because of the platelike shape of the talc particles. In general, yield stress and toughness decreased with increasing filler volume fraction. Comparing the two different coupling agents, the study found that the use of titanate as a reactive coupling agent enhanced the modulus at high filler loadings in some cases, and improved the yield stress and toughness in most cases. However, the nonreactive silicone coupling agent has been found to be a much more effective modifier, improving modulus, yield stress and toughness in most cases, and achieving significantly higher values of these properties than with titanate. While the use of titanate was found to improve particle-matrix interaction, silicone acted as a dispersant, decreasing particle-particle interactions. The authors therefore conclude that, for PP-based composites, the structural modification of the composites - the aggregation and dispersion of filler - is more important than interfacial modification as far as improving the tensile properties is concerned.
02002 Elsevier Science