Mauro Zammarano

Synthesis and characterization of isosorbide-based polyphosphonates as biobased flame-retardants

A new isosorbide-based polyphosphate was synthesized and applied as a flame-retardant for polylactic acid (PLA). The storage modulus and glass transition temperature of PLA/polyphosphonate blends was unaffected by the inclusion of polyphosphonate, but moderate depressions of PLAs tensile strength (16%, 28%, and 45% reduction from PLA at a polyphosphonate mass percentage of 5%, 10%, and 15%, respectively) and strain-at-break (0%, 17%, and 30% reduction from PLA at a polyphosphonate mass percentage of 5%, 10%, and 15%, respectively) were observed. Modified UL-94 flammability testing indicated that isosorbide-based polyphosphonates are effective flame retardants for PLA and are able to self-extinguish flames in less than 2 s to achieve V2 and V0 ratings at polyphosphonate mass percentage of 5% and 15%, respectively. Fire test data indicates a gas phase mechanism that can quench the flame when no external radiant heat flux is present (e.g., in modified UL-94 testing) but does not affect the materials heat release rate in forced combustion (e.g., in cone calorimetry). Use of the biobased flame retardants described herein yields flame retardant PLA containing up to 97% by mass of bio-derived content.

Revealing the interface in polymer nanocomposites.

The morphological characterization of polymer nanocomposites over multiple length scales is a fundamental challenge. Here, we report a technique for high-throughput monitoring of interface and dispersion in polymer nanocomposites based on Förster resonance energy transfer (FRET). Nanofibrillated cellulose (NFC), fluorescently labeled with 5-(4,6-dichlorotriazinyl)-aminofluorescein (FL) and dispersed into polyethylene (PE) doped with Coumarin 30 (C30), is used as a model system to assess the ability of FRET to evaluate the effect of processing on NFC dispersion in PE. The level of energy transfer and its standard deviation, measured by fluorescence spectroscopy and laser scanning confocal microscopy (LSCM), are exploited to monitor the extent of interface formation and composite homogeneity, respectively. FRET algorithms are used to generate color-coded images for a real-space observation of energy transfer efficiency. These images reveal interface formation at a nanoscale while probing a macroscale area that is large enough to be representative of the entire sample. The unique ability of this technique to simultaneously provide orientation/spatial information at a macroscale and nanoscale features, encoded in the FRET signal, provides a new powerful tool for structure-property-processing investigation in polymer nanocomposites.

Formation of extended ionomeric network by bulk polymerization of l,d-lactide with layered-double-hydroxide

Abstract We report the formation of an ionomeric network in a poly( l , d -lactide) hybrid nanocomposite, (PLDLA-HYB) during in-situ melt polymerization of l , d -lactide in the presence of magnesium/aluminum layered-double-hydroxide (LDH) without added catalyst. The effect of LDH mass loading and reaction time on molecular mass and yield of soluble poly( l , d -lactide) (PLDLA-SOL) present in the hybrid was investigated for a better understanding of the conflicting roles of LDH in polymerization and degradation of PLDLA-SOL. High molecular mass PLDLA-SOL is obtained through initiation of polymerization by LDH. However an additional insoluble organic–inorganic fraction, INSOL, is also observed within the product when PLDLA-SOL is extracted using methylene chloride as solvent. It is proposed that INSOL is an ionomeric network comprising hydrogen-bonded, or otherwise co-ordinated, lactic acid monomer salts of magnesium, together with PLDLA in a 24%–76% mass ratio.

Effect of ammonium polyphosphate to aluminum hydroxide mass ratio on the properties of wood- flour/polypropylene composites

Two halogen-free inorganic flame retardants, ammonium polyphosphate (APP) and aluminum hydroxide (ATH) were added to wood-flour/polypropylene composites (WPCs) at different APP to ATH mass ratios (APP/ATH ratios), with a constant total loading of 30 wt % (30% by mass). Water soaking tests indicated a low hygroscopicity and/or solubility of ATH as compared to APP. Mechanical property tests showed that the flexural properties were not significantly affected by the APP/ATH ratio, while the impact strength appeared to increase with the increasing ATH/APP ratio. Cone calorimetry indicated that APP appeared to be more effective than ATH in reducing the peak of heat release rate (PHRR). However, when compared to the neat WPCs, total smoke release decreased with the addition of ATH but increased with the addition of APP. Noticeably, WPCs containing the combination of 20 wt % APP and 10 wt % ATH (WPC/APP-20/ATH-10) showed the lowest PHRR and total heat release in all of the formulations. WPCs combustion residues were analyzed by scanning electron microscopy, laser Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR). Thermogravimetric analysis coupled with FTIR spectroscopy was used to identify the organic volatiles that were produced during the thermal decomposition of WPCs. WPC/APP-20/ATH-10 showed the most compact carbonaceous residue with the highest degree of graphitization.

Smoldering and Flame Resistant Textiles via Conformal Barrier Formation

A durable and flexible silicone-based backcoating (halogen free) is applied to the backside of an otherwise smoldering-prone and flammable fabric. When exposed to fire, cyclic siloxanes (produced by thermal decomposition of the backcoating) diffuse through the fabric in the gas phase. The following oxidation of the cyclic siloxanes forms a highly conformal and thermally stable coating that fully embeds all individual fibers and shields them from heat and oxidation. As a result, the combustion of the fabric is prevented. This is a novel fire retardant mechanism that discloses a powerful approach towards textiles and multifunctional flexible materials with combined smoldering/flaming ignition resistance and fire-barrier properties.

Impact of Test and Foam Design on Smoldering

......................................................................................................................................... iii

A novel application of silicone-based flame-retardant adhesive in plywood

A silicone-based elastomer filled with vinyl-silane treated aluminum hydroxide was used to replace conventional polyurethane-based adhesive to provide a flame-retardant adhesive for plywood. The shear strength and fire performance of such a silicone-based (SI) adhesive glued plywood (SI/plywood) were investigated and compared to those of the polyurethane-based (PU) adhesive glued plywood (PU/plywood). The shear strength of the SI/plywood [(0.92 ± 0.09) MPa] was about 63% lower than that of the PU/plywood at room temperature, but it was less sensitive to water (62% reduction for the PU/plywood and 30% reduction for the SI/plywood after hot-water immersion at 63 °C for 3 h). The fire performance of plywood was assessed by a simulated match-flame ignition test (Mydrin test), lateral ignition and flame spread test, cone calorimetry, and thermocouple measurements. With a higher burn-though resistance and thermal barrier efficiency, and lower flame spread and heat release rate, the SI/plywood exhibited a superior fire-resistance and reaction-to-fire performance and improved fire-resistance as compared to the PU/plywood. The SI adhesive generated an inorganic protective layer on the sample surface that visibly suppressed glowing and smoldering of the plywood during combustion. The SI adhesive was also combined and reinforced with cellulosic fabric (CF) or glass fabric (GF) to prepare composite plywood (SI/CF/plywood and SI/GF/plywood) with improved fire performance. The cone calorimetry and thermocouple measurements indicated that the use of CF or GF in SI/CF/plywood and SI/GF/plywood, respectively, suppressed the delamination and cracking of the composite plywood and promoted the formation of an effective thermal barrier during smoldering and flaming combustion. Particularly, the SI/GF/plywood exhibited the most effective fire barrier with no crack formation, and the lowest heat release rate among the plywood types investigated in this study.

Epoxy Composites Using Wood Pulp Components as Fillers

The components of wood, especially lignin and cellulose, have great potential for improving the properties of polymer composites. In this chapter, we discuss some of the latest developments from our lab on incorporating wood based materials into epoxy composites. Lignosulfonate was used as a flame retardant and cellulose nanocrystals were used as reinforcing materials. Lignosulfonate will disperse well in epoxy, but phase separates during curing. An epoxidation reaction was developed to immobilize the lignosulfonate during curing. The lignosulfonate – epoxy composites are characterized using microcombustion and cone calorimetry tests. Cellulose also has poor interfacial adhesion to hydrophobic polymer matrixes. Cellulose fibers and nanocrystals aggregate when placed in epoxy resin, resulting in very poor dispersion. The cellulose nanocrystal surface was modified with phenyl containing materials to disrupt cellulose interchain hydrogen bonding and improve dispersion in the epoxy resin. The cellulose nanocrystal – epoxy composites were characterized using tensile tests and microscopic techniques.