Synergistic Effect of APP and TBC Fire-Retardants on the Physico-Mechanical Properties of Strandboard

This study explored the feasibility of fabricating fire-retardant strandboard with low mechanical properties deterioration to the physico-mechanical properties. A hybrid fire-retardant system of ammonium polyphosphate (APP) and 1,3,5-tris(2,3-dibromopropyl)-1,3,5-triazinane-2,4,6-trione (TBC) was investigated. Thermogravimetric analysis results show that both APP and TBC enhance the thermal stability and incombustibility of wood strands. An infrared spectrum was applied to investigate the effect of flame retardants on the curing behaviors of polymeric diphenylmethane diisocyanate (PMDI) resin. Based on the results of limiting oxygen index (LOI) and Cone calorimetry (CONE), APP and TBC both lead to a higher fire retardancy to strandboard. It is worth mentioning that the two flame retardants lead to evidently differential influences on the modulus of rupture (MOR), modulus of elasticity (MOE), internal bond (IB), and water-soaking thickness swelling (TS) properties of strandboard. Hence, a hybrid flame retardant is prominent in manufacturing strandboard with both good fire retardant and satisfying physico-mechanical properties.

On the Feasibility of a pMDI-Reduced Production of Wood Fiber Insulation Boards by Means of Kraft Lignin and Ligneous Canola Hulls

The thermal insulation of buildings using wood fiber insulation boards (WFIBs) constitutes a positive contribution towards climate change. Thereby, the bonding of wood fibers using mainly petrochemical-based resins such as polymeric diphenylmethane diisocyanate (pMDI) is an important measure to meet required board properties. Still there is a need to reduce or partial substitute the amount of these kinds of resins in favor of a greener product. This study therefore focusses on the feasibility of reducing the amount of pMDI by 50% through the addition of 1% BioPiva 395 or Indulin as two types of softwood Kraft-Lignin and lignin rich canola hulls together with propylene carbonate as a diluent. A panel density of 160 kg/m3 and a thickness of 40 mm was aimed. The curing of these modified pMDI was investigated by using two types of techniques: hot-steam (HS) and innovative hot-air/hot-steam-process (HA/HS). The WFIBs were then tested on their physical-mechanical properties. The equilibrium moisture content (EMC) was determined at two different climates. An exemplary investigation of thermal conductivity was conducted as well. The WFIBs did undergo a further chemically based analysis towards extractives content and elemental (C, N) composition. The results show that it is feasible to produce WFIBs with lower quantities of pMDI resin and added lignin with enhanced physical-mechanical board properties, which were lacking no disadvantages towards thermal conductivity or behavior towards moisture, especially when cured via HA/HS-process.

Highly Loaded Cellulose/Poly (butylene succinate) Sustainable Composites for Woody-Like Advanced Materials Application

We report the manufacturing and characterization of poly (butylene succinate) (PBS) and micro cellulose (MCC) woody-like composites. These composites can be applied as a sustainable woody-like composite alternative to conventional fossil polymer-based wood-plastic composites (WPC). The PBS/MCC composites were prepared by using a melt blending of 70 wt% of MCC processed from bleached softwood. MCC was modified to enhance dispersion and compatibility by way of carbodiimide (CDI), polyhydroxy amides (PHA), alkyl ester (EST), (3-Aminopropyl) trimethoxysilane (APTMS), maleic acid anhydride (MAH), and polymeric diphenylmethane diisocyanate (PMDI). The addition of filler into PBS led to a 4.5-fold improvement of Young’s modulus E for the MCC composite, in comparison to neat PBS. The 1.6-fold increase of E was obtained for CDI modified composition in comparison to the unmodified MCC composite. At room temperature, the storage modulus E′ was found to improve by almost 4-fold for the APTMS composite. The EST composite showed a pronounced enhancement in viscoelasticity properties due to the introduction of flexible long alkyl chains in comparison to other compositions. The glass transition temperature was directly affected by the composition and its value was −15 °C for PBS, −30 °C for EST, and −10 °C for MAH composites. FTIR indicated the generation of strong bonding between the polymer and cellulose components in the composite. Scanning electron microscopy analysis evidenced the agglomeration of the MCC in the PBS/MCC composites. PMDI, APTMS, and CDI composites were characterized by the uniform dispersion of MCC particles and a decrease of polymer crystallinity. MCC chemical modification induced the enhancement of the thermal stability of MCC composites.

Effect of Lignin Plasticization on Physico-Mechanical Properties of Lignin/Poly(Lactic Acid) Composites

Kraft lignin (KL) or plasticized KL (PKL)/poly(lactic acid) (PLA) composites, containing different lignin contents and with and without the coupling agent, were prepared in this study using twin-screw extrusion at 180 °C. Furthermore, ε-caprolactone and polymeric diphenylmethane diisocyanate (pMDI) were used as a plasticizer of KL and a coupling agent to improve interfacial adhesion, respectively. It was found that lignin plasticization improved lignin dispersibility in the PLA matrix and increased the melt flow index due to decrease in melt viscosity. The tensile strength of KL or PKL/PLA composites was found to decrease as the content of KL and PKL increased in the absence of pMDI, and increased due to pMDI addition. The existence of KL and PKL in the composites decreased the thermal degradation rate against the temperature and increased char residue. Furthermore, the diffusion coefficient of water in the composites was also found to decrease due to KL or PKL addition.

Effect of lignin-containing cellulose nanofibrils on the curing kinetics of polymeric diphenylmethane diisocyanate (PMDI) resin

In order to increase the curing rate of polymeric diphenylmethane diisocyanate (PMDI) resin, different contents of lignin-containing cellulose nanofibrils (L-CNFs) were blended into the PMDI. Differential scanning calorimetry (DSC) was used to examine how the addition of L-CNFs influences the curing kinetics of PMDI resin. The activation energy (Ea) of the curing reaction of PMDI/L-CNF systems was calculated using the Kissinger, Friedman and Flynn-Wall-Ozawa model-free methods. The results showed that Ea values calculated by the aforementioned three methods varied in a similar trend with the increase in the L-CNF content. Adding L-CNFs could decrease the Ea value of the curing reaction of PMDI and speed up the curing reaction. The acceleration of the cure rate of the PMDI resin upon the addition of L-CNFs may be attributable to the effective dispersion of the L-CNFs into the PMDI resin as well as the reaction between the hydroxyl (-OH) groups of the L-CNFs and the isocyanate (-NCO) groups of the PMDI.

Structure and properties evaluation of epoxy resin modified with polyurethane based on polymeric MDI and different polyols

The present work investigates the properties and structure of epoxy resin (EP) modified with polyurethane (PUR). This latter was prepared using polymeric diphenylmethane diisocyanate and polyethylene glycol (PEG 400) or polyoxypropylene diol with different molecular weights (POPD 1002 and POPD 2002). It was confirmed that 5% of either PUR improved significantly the mechanical properties of EP. Impact strength and critical stress intensity factor values of modified epoxy compositions were increased by 200 and 100%, respectively, relative to pristine samples. Fourier-transform infrared spectra confirmed the occurrence of chemical reactions between reactive groups of EP and PUR. The fracture surface of EP modified with PUR based on PEG exhibited less plastic yielding, while river-like lines with more pronounced plastic deformations were shown by EP modified with 5% PUR with longest chains.