Abstract
In this study, bamboo charcoal (BC) was used as a substitute filler for bamboo powder (BP) in a lignocellulose-plastic composite made from polylactic acid (PLA), with aluminum hypophosphite (AHP) added as a fire retardant. A set of BC/PLA/AHP composites were successfully prepared and tested for flame-retardancy properties. Objectives were to (a) assess compatibility and dispersibility of BC and AHP fillers in PLA matrix, and (b) improve flame-retardant properties of PLA composite. BC reduced flexural properties while co-addition of AHP enhanced bonding between PLA and BC, improving strength and ductility properties. Adding AHP drastically reduced the heat release rate and total heat release of the composites by 72.2% compared with pure PLA. The formation of carbonized surface layers in the BC/PLA/AHP composites effectively improved the fire performance index (FPI) and reduced the fire growth index (FGI). Flame-retardant performance was significantly improved with limiting oxygen index (LOI) of BC/PLA/AHP composite increased to 31 vol%, providing a V-0 rating in UL-94 vertical flame test. Adding AHP promoted earlier initial thermal degradation of the surface of BC/PLA/AHP composites with a carbon residue rate up to 40.3%, providing a protective layer of char. Further raw material and char residue analysis are presented in Part II of this series.
Highlights
The enormous range and waste volumes of non-biodegradable petroleum-derived plastics produced over past decades are a leading source of land and ocean pollutants and hazards for marine life
bamboo powder (BP) was from milled moso bamboo and bamboo charcoal (BC) was obtained by pyrolizing fresh moso bamboo in a brick kiln at a carbonization temperature of 600 to 800 ◦ C followed by grinding to a particle size of 50 to 200 mesh
BP is comprised of mostly C (47.2%) and O (45.1%) and contains higher amounts of H and O elements making it flammable under dry conditions, similar to wood flour or wood fiber used in wood plastic composite (WPC)
Summary
The enormous range and waste volumes of non-biodegradable petroleum-derived plastics produced over past decades are a leading source of land and ocean pollutants and hazards for marine life. Biodegradable alternatives such as polylactic acid (PLA) have been introduced over the past 40 years in an attempt to reduce the future volume of non-degradable single-use plastic items and packaging [1]. PLA is compostable (under correct conditions) and can be processed into a wide variety of products on standard plastics processing equipment It loses its thermal molecular weight stability at Polymers 2020, 12, 2217; doi:10.3390/polym12102217 www.mdpi.com/journal/polymers
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