Polyurethane Composites Reinforced with Walnut Shell Filler Treated with Perlite, Montmorillonite and Halloysite

Abstract

In the following study, polyurethane (PUR) composites were modified with 2 wt.% of walnut shell filler modified with selected mineral compounds–perlite, montmorillonite, and halloysite. The impact of modified walnut shell fillers on selected properties of PUR composites, such as rheological properties (dynamic viscosity, foaming behavior), mechanical properties (compressive strength, flexural strength, impact strength), dynamic-mechanical behavior (glass transition temperature, storage modulus), insulation properties (thermal conductivity), thermal characteristic (temperature of thermal decomposition stages), and flame retardant properties (e.g., ignition time, limiting oxygen index, heat peak release) was investigated. Among all modified types of PUR composites, the greatest improvement was observed for PUR composites filled with walnut shell filler functionalized with halloysite. For example, on the addition of such modified walnut shell filler, the compressive strength was enhanced by ~13%, flexural strength by ~12%, and impact strength by ~14%. Due to the functionalization of walnut shell filler with thermally stable flame retardant compounds, such modified PUR composites were characterized by higher temperatures of thermal decomposition. Most importantly, PUR composites filled with flame retardant compounds exhibited improved flame resistance characteristics-in all cases, the value of peak heat release was reduced by ~12%, while the value of total smoke release was reduced by ~23%.

Bio-Based Rigid Polyurethane Foam Composites Reinforced with Bleached Curauá Fiber

“…Due to the alignment of the fibers, when RPUF is rising, cells’ elongations are expected, especially when the filler is used above the matrix saturation (i.e., those CF 1). Furthermore, the changing of the cells’ mechanism formation, from homogenous to heterogonous, contribute to the overall distribution and lower uniformity of the RPUF cells’ structure [ 47 ], highlighting, again, those CF 1.…”

Properties of Rigid Polyurethane Foam Filled with Sawdust from Primary Wood Processing

“…For these reasons, the use of various types of nanofillers such as: fume silica [ 16 ], cellulose nanocrystals [ 17 ], spherical TiO 2 , platelet nanoclay, rod-shaped carbon nanofibers [ 18 ], montmorillonite [ 19 ] and others should be considered as promising solutions in this field. They act as nucleation sites and thus reduce the cell size and, as a result, effectively increase the mechanical properties, fire resistance and thermal stability and reduce the thermal conductivity of PUR foams [ 13 , 20 ]. However, a significant problem with the use of such fillers is their relatively high price and their tendency to agglomerate, which in consequence disturbs the foaming process and deteriorates the properties of the finished foam.…”

“…The studies carried out so far show that agricultural waste is a material with high application potential in the production of composite PUR foams. It has been shown that waste products such as buckwheat husks [ 7 ], walnut shells [ 12 , 20 ], plum stones [ 22 ], straw fibre [ 24 ], hemp fibre [ 25 ], wheat slops [ 26 ], rapeseed cake [ 21 ], soy and potato protein [ 27 , 28 ], sugar beet pulp [ 15 ], egg shell [ 29 ], ground coffee [ 30 ], keratin chicken feathers [ 31 ] and many others have a beneficial effect on the properties of foams. Another source of naturally derived fillers is the timber industry.…”

Printable Hydrogels Based on Alginate and Halloysite Nanotubes

“…Due to their properties, HNTs can be used in many fields [ 25 , 26 , 27 , 28 , 29 , 30 ]. The possibility to encapsulate active molecules within their lumen has paved the way for applications in catalysis, food packaging, biomedical technology and cultural heritage treatment [ 31 , 32 , 33 , 34 , 35 , 36 , 37 ].…”