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This study provides insight into the accelerated hydrolysis of polyester PLA through the addition of phosphites based on pentaerythritol. To control hydrolysis and ensure processing stability, different types of phosphites and combinations of phosphites with acid scavengers were studied. Therefore, commercially available PLA was compounded with selected additives on a twin-screw extruder, and hydrolysis experiments were performed at 23 °C, 35 °C and 58 °C in deionized water. Hydrolysis of PLA was evaluated by the melt volume rate (MVR) and size-exclusion chromatography (SEC). For example, after 4 days of water storage at 58 °C, the number average molecular weight of the PLA comparison sample was reduced by 31.3%, whereas PLA compounded with 0.8% phosphite P1 had a 57.7% lower molecular weight. The results are in good agreement with the expected and tested stability against hydrolysis of the investigated phosphite structures. 31P-NMR spectroscopy was utilized to elucidate the hydrolysis of phosphites in the presence of lactic acid. With the addition of phosphites based on pentaerythritol, the hydrolysis rate can be enhanced, and faster biodegradation behavior of biodegradable polyesters is expected. Accelerated biodegradation is beneficial for reducing the residence time of polymers in composting facilities or during home composting and as litter or microplastic residues.

The multicomponent flame retardant system of melamine polyphosphate (MPP), melamine cyanurate (MC) and aluminum diethylphosphinate (AlPi) is proposed and investigated for thermoplastic polyurethane (TPU). The synergy between those additives and the resulting superior fire performance are discussed. Systematically varied sets of flame retarded TPU with various MPP/MC/AlPi ratios were investigated in terms of fire behavior, pyrolysis products and mechanical properties. The total amount of the additives was always 30 wt.-%. Further, the influence of various AlPi concentrations was investigated. The optimal MPP:MC ratio was determined while keeping the amount of AlPi constant. The combination of 8 wt.-% MPP, 12 wt.-% MC and 10 wt.-% is proposed as the most promising halogen free flame retardant formulation for TPU, because it yielded a reduction in PHRR from 2660 kW/m2 (TPU) to 452 kW/m2 and enabled V-0 classification in the UL 94 test. Combinations of MPP and MC as well a high concentration of AlPi are beneficial for the mechanical properties e.g. tensile strength and elongation at break of the formulations and could be a strong competitor to commercial flame retarded TPUs.

In this study, the flame retardant effect of the Zn salt of 10-hydroxy-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (Zn-DOPOx), melamine polyphosphate (MPP) and their mixture was investigated towards the mode of action in glass fiber-reinforced polyamide 66 (PA 66 GF). The flammability was evaluated using UL 94 V and cone calorimetry. Influence on char formation was analyzed by SEM. Thermal decomposition of Zn-DOPOx and MPP was studied by TGA and ATR-FTIR. The release of gaseous PA 66 decomposition products was investigated using TGA-DTA-FTIR. Combining Zn-DOPOx and MPP leads to an improvement in flame retardancy, most pronounced for equal parts of weight. Mode of action changes significantly for Zn-DOPOx:MPP (1:1) compared to the sole components and a strong interaction between Zn-DOPOx and MPP is revealed, resulting in a more open char structure. Fuel dilution as well as less exothermic decomposition are essential for the mode of action of the combination. Through low HRR values and high CO/CO2 ratio during cone calorimetry measurements, a significant increase in gas phase activity was proven. Therefore, it is concluded that Zn-DOPOx:MPP (1:1) leads to a significant increase in flame retardancy through a combination of mode of actions in the gas and condensed phase resulting from the change in thermal stability.

Thermo-oxidative aging of dipentaerythritol (DPE) stabilized, glass fibre reinforced PA66 compounds was studied at 200°C. The influence of DPE as a thermo-oxidation stabilizer on the retention of tensile properties, molecular weight, crystallinity, oxidized layer thickness as well as the specimen surface and fracture morphology was analysed. Moreover, the impact of DPE on the intrinsic humidity inside the test specimens before aging was examined due to its hygroscopic behaviour. The reduction of the extractable amount of DPE from test granules over the aging time proved the existence of chain extension or crosslinking reactions between the polyamide or its degradation products and DPE. Whereas DPE improves the retention of mechanical characteristics during aging only slightly, the combination of DPE and glass fibres reaches retention of mechanical characteristics above 50 % after 1000 h of aging at 200°C in air. DPE raises the intrinsic humidity during processing and before aging resulting in an increase of PA66 degradation during processing and in the first aging phase due to additional hydrolysis. Both the ensuing shorter chain length and water-induced post-crystallisation give rise to higher crystallinity after processing, increasing the oxygen diffusion limitation which results in slower thermo-oxidation. In addition, DPE accelerates the formation of the oxidized layer on the PA66 surface but slows down its growth during the later aging phase.

The compositional and stereochemical heterogeneity of copolymers are key molecular metrics, and their knowledge is of pivotal importance for evidence based material development. Yet, while it is state of the art to determine these parameters for many petroleum based polymers, little insight exists in that regard for bio-based materials. Towards this end, size exclusion chromatography (SEC) was hyphenated with nuclear magnetic resonance spectroscopy (NMR) in an offline manner and a blend of poly(lactic acid) (PLA) and poly(butylene succinate-co-adipate) (PBSA) investigated. Thus, the microstructural heterogeneity could be shown with regard to tacticity of the PLA and regioregularity of the PBSA component. The results show, that the highest molar mass fraction differs in stereochemical com position from the others. It may be assumed that this is the result of misinsertions with regard to stereochemistry occurring during the catalytic polymerization of the lactide. While the content of both constituent polymers along the molar mass axis could be well studied using a univariate analysis of the infrared (IR) spectra, this method failed to profile the adipate and succinate content individually. For this purpose, SEC was coupled to IR spectroscopy in online mode and the spectra were evaluated by a multivariate protocol. Thus, the content of each monomer along the molar mass distribution could be mapped with high chromatographic resolution.

The commercially available partially bio-based poly(butylene succinate) (PBS) and poly(butylene succinate-co-adipate) (PBSA) are subjected to prolonged and multiple extrusion cycles to investigate their thermal behavior. Empirically, both PBS and PBSA form branches at 190°C, with PBS possessing a higher tendency for branching than PBSA as studied by rheology and size exclusion chromatography (SEC). In each case, the branching is favored by fumaric acid moieties, making both PBS and PBSA susceptible to accelerated thermal oxidation. Indeed, the NMR signal attributed to fumaric acid disappears upon thermal processing of PBS and PBSA. Presumably, the bio-based succinic acid used contains minor quantities of fumaric acid, yet still sufficient to cause this surprising processing behavior. The branching of both polymers is suppressed by stabilizers such as phenolic antioxidants, as proven by rheology and SEC. This is complemented by nuclear magnetic resonance (NMR), revealing that the fumaric acid signal is still well-resolved in the stabilized processed samples.

An IR-camera is used for investigating flame retarding mode of actions during UL94 standard flammability test. Commonly used UL94 tests give qualitative results of burning behavior and are improved by taking temperature profiles with an IR-camera. Analysis of these profiles leads to new insights into the underlying mechanism of the flame retardant. Lower peak temperatures and faster cooling are a hint for a cooling mechanism. A shorter time range to reach the peak temperature is significant for dilution. Every flame retarding mode of action has its own specific influence on the temperature profile. Therefore, a more detailed conclusion of the flame retarding behavior of flame retardants can be obtained by the method described here.

Accelerated (artificial) weathering and thermal aging tests were performed to investigate the effectiveness of different formulations in reducing the UV/heat degradation extent for two low-density polyethylene types (LDPE-A, LDPE-T). The two LDPEs differ in the type and extent of branching due to the applied polymerization process, with LDPE-A being produced in an autoclave and LDPE-T in a tubular reactor. Oligomeric or high molecular weight hindered amine light stabilizer (HALS), and two UV absorbers of benzophenone or hydroxyphenyl-triazine types were equally introduced to both the LDPE grades at a total content of 0.2 wt%. The surface morphology, as well as thermal and mechanical properties, were examined during aging showing a significant degradation extent for the neat samples. In particular, a mechanism of chain scission/branch-ing that resulted in crosslinking was assumed for the neat polyethylenes, after combining the decrease of molecular weight observed in the GPC analysis with the increase in Young's modulus after UV exposure. LDPE-T presented higher photo-ox-idation rates due to its comb-like branched structure and its higher possibility of intermolecular reactions between adjacent chains. Little or no degradation was observed for the stabilized grades, confirming the effectiveness of the selected UV/heat systems in improving the weathering resistance of the two LDPE grades and enhancing their useful lifetime. This publication was made possible by the NPRP award (NPRP 9-161-1-030) from the Qatar National Research Fund (a member of The Qatar Foundation). We are also grateful to BASF and Sabo for supplying the additives at no cost. The statements made herein are solely the responsibility of the author(s). Scopus

Linear economy models are no longer acceptable for the plastic industry and a change to a sustainable circular plastic economy must take place. In the field of thermoplastic foams, the biopolymer poly(lactic acid) (PLA) is a suitable alternative for fossil based foams like polystyrene. However, the production ofPLA bead foams is still a challenge. In regards to circular plastic economy products, a reduction of the needed polymer additives is aspired to simplify the union of end-of-life plastic streams. Flame retardants (FR) are required in many applications and are often the largest proportion of additives. It turns out that the removal of FRs, for example the removal of the REACh registered FR hexabromocyclododecane for polystyrene foams, requires a great effort. This paper shows that PLA bead foams require no FR to achieve a class E classification for construction products. Therefore, nine PLA types are analyzed by differential scanning calorimetry, thermogravimetric analysis, gel permeation chromatography, and rheotens measurements. From five types, PLA bead foams could be produced with two different densities. In addition, PLA bead foams containing 1.5 wt% alkoxy amine FR were produced. The flammability of the PLA bead foams was investigated by LOI, DIN-4102-1-B2, and cone calorimeter tests.

The rapid mass calorimeter (RMC) was used as a screening tool based on accelerated fire testing to assess flame-retarded thermoplastic polyurethane (TPU). The reliability of RMC results was proven with the cone calorimeter as reference fire test. The influence of melamine cyanurate (MC) concentration on the fire performance of TPU was investigated, along with some flame-retardant combinations such as MC with aluminium diethylphosphinate (AlPi), aluminium trihydrate (ATH), and melamine polyphosphate (MPP). The two-stage burning behaviour of TPU was investigated in detail; the first stage corresponds mainly to the hard segments' decomposition and has a much lower effective heat of combustion (EHC) than the second stage, in which mainly the soft segments decompose and an intensive liquid pool fire is observed in the cone calorimeter set-up. In addition to fire testing with the cone calorimeter, RMC, and UL 94 flammability tests, the decomposition of the materials was investigated using thermogravimetric analysis coupled with infrared spectrometry (TGeFTIR). TPU/MC/AlPi shows the most promising results, achieving V-0 classification in UL 94 and reducing the extreme peak heat release rate (PHRR) of the liquid pool fire from 3154 kW/m2 to 635 kW/m2. Using MC/AlPi/MPP enhances the latter PHRR reduction further. The decomposition products identified in the gas phase via TGeFTIR reveal specific MCeAlPi eMPP interactions, as they differ from products seen in systems with MC/AlPi or MC/MPP. Correlations between RMC and cone calorimeter results were examined and presented in the final part of the paper. Several characteristics correlate strongly, pointing out that RMC is a reliable high-throughput fire testing method to screen multicomponent flame-retardant solutions in TPU.

Additives for plastics based on natural raw materials (“bio‐additives”) are well‐known substances that have been used as such or in chemically modified form in the plastics industry for many years. However, interest in new bioadditives is increasing in line with the goal of replacing petrochemical raw materials and promoting a circular economy, as well as with the increasing demand for biopolymers. Since practically all polymers require additives to guarantee their properties, processing and application, it is logical for biopolymer formulations to also be developed entirely on the basis of renewable raw materials, i.e. both the polymer and the additive. The most important additives include plasticizers, antioxidants and flame retardants.

Oxyimides have gained wide interest in different applications because of radical generating properties, such as flame retardants in various polymers. As polyamide-6 (PA6) is highly flammable and shows burning dripping during incineration the mentioned issues have to be overcome by the use of a flame retardant. All previously developed oxyimides already show these properties, but this is based on the ester structure with the consequence of transesterification/transamidation in polyesters/polyamides. In this work, a new class of oxyimides based on ether bonds is synthesized. Oxyimide ethers do not degrade PA6, only sometimes slightly increase MVR, and show excellent flame retardancy in PA6. Depending on the structure, UL 94 V-0 can be reached with very low loadings. This makes oxyimide ethers an alternative to commonly used flame retardants for PA6.

The current article deals with the development of different novel, tailor-made polyolefin formulations exhibiting both low flammability and high weathering resistance, so as to provide value-added polyethylene grades with extended service lifetime. Two low-density (LDPE) and one linear low-density (LLDPE) polyethylene grades were modified via melt compounding with an additive system comprising: (a) a nitrogen-phosphorous intumescent system for flame retardance and (b) a hindered amine light stabilizer and a benzophenone-type UV absorber for UV/heat stabilization, at a total loading of 30-35 wt%. The target was to reach V0 classification in UL94V flammability tests, while to a large extent maintaining the mechanical properties, such as, tensile and impact strength of the investigated polymers, thus ensuring that the additives do not interfere significantly with the material quality. Subsequently, the compounds were subjected to separate artificial UV and heat aging at 100 C for 1500 h; the formulations showed good flame retardance, even after prolonged artificial weathering, but there was an observable, although acceptable, decrease in the mechanical properties. Nevertheless, all the results show that the developed polyethylene compounds are very promising for outdoor applications, such as, irrigation piping and profiles, where long-term weathering stability is important, and where flame retardance is important for safety during storage. This publication was made possible by the NPRP award (NPRP 9-161-1-030) from the Qatar National Research Fund (a member of The Qatar Foundation). We are also grateful to BASF and Sabo for supplying the additives at no cost. We further express our gratitude to Dr. Mabrouk Ouederni from QAPCO for providing us with the three polyethylene grades. The statements made herein are solely the responsibility of the author(s). Scopus

Additive fur Kunststoffe auf der Basis naturlicher Rohstoffe („Bio-Additive“) sind einerseits altbekannte Substanzen, die als solche oder in chemisch modifizierter Form seit vielen Jahren in der Kunststoffwelt eingesetzt werden. Andererseits steigt das Interesse an neuen Bioadditiven mit dem Ziel, petrochemische Rohstoffe zu ersetzen und eine Kreislaufwirtschaft zu begunstigen, sowie auch mit der zunehmenden Nachfrage nach Biopolymeren. Da nahezu alle Polymere Additive benotigen, um Eigenschaften, Verarbeitung und Anwendung sicherzustellen, ist es folgerichtig, auch Biopolymer-Formulierungen vollstandig auf der Basis nachwachsender Rohstoffe zu entwickeln, also sowohl das Polymer als auch das Additiv. Zu den wichtigsten Additiven gehoren Weichmacher, Antioxidantien und Flammschutzmittel.

Novel bifunctional antioxidants (AO) with high molecular weight were successfully synthesized by two-step free-radical thiol-ene click reaction and transesterification. The structures of the stabilizers were confirmed by 1H NMR spectra and Fourier Transform Infrared Spectrometry (FTIR). Thermal gravimetric analysis (TGA) showed high temperature stability above 300 °C, proving suitability as potential stabilizers for standard and technical polymers. The performance of the bifunctional antioxidants was investigated through oxidation induction time (OIT) and accelerated heat aging of PP compounds in comparison to state of the art stabilizers represented through 2,2′-thiodiethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and a binary mixture of pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate) and dioctadecyl 3,3′-thiodipropionate. Reduced degradation and extended maintenance of mechanical values of PP stabilized through the novel antioxidants during heat aging are due to the high amount of alkyl sulfide groups. Furthermore, a low migration tendency of the high-molecular AO could be determined by FTIR mapping of heat-treated samples.

The effect of six halogen-free flame retardant (FR) formulations was investigated on the thermal stability of two low-density polyethylenes (LDPE) and one linear low-density polyethylene (LLDPE), by means of thermogravimetric analysis (TGA) under nitrogen and air atmosphere. The relative data were combined with flammability properties and the overall performance of the FRs was correlated with the type of branching in the polyethylene grades and to their processing behavior. The thermal degradation kinetics was further determined based on the Kissinger and Coats-Redfern methods. In terms of flammability, the addition of a triazine derivative and ammonium polyphosphate at a loading of 35 wt. %. was found to be the most efficient, leading to UL 94 V0 ranking in the case of the LDPE grade produced in an autoclave reactor. - 2019 by the authors. Funding: This publication was made possible by the NPRP award [NPRP 9-161-1-030] from the Qatar National Research Fund (a member of The Qatar Foundation). The statements made herein are solely the responsibility of the author(s). Scopus

Wire and cable coverings are potentially a major cause of fire in buildings and other installations. As they need to breach fire walls and are frequently located in vertical ducting, they have significant potential to increase the fire hazard. It is therefore important to understand the ignition and burning characteristics of cables by developing a model capable of predicting their burning behaviour for a range of scenarios. The fire performance of electrical cables is usually dominated by the fire performance of the sheathing materials. The complexity of the problem increases when cable sheathing incorporates fire retardants. One-dimensional pyrolysis models have been constructed for cable sheathing materials, based on milligram-scale and bench-scale test data by comparing the performance of three different software tools (ThermaKin, Comsol Multiphysics and FDS, version 6.0.1). Thermogravimetric analysis and differential scanning calorimetry were conducted on powdered cable coatings to determine the thermal degradation mechanism, the enthalpy of decomposition reactions, and the heat capacities of all apparent species. The emissivity and the in-depth absorption coefficient were determined using reflectance and transmittance measurements, with dispersive and non-dispersive spectrometers and integrating spheres. Bench-scale tests were conducted with a mass loss calorimeter flushed with nitrogen on samples in a horizontal orientation, for comparison with the pyrolysis model of non-flaming decomposition at an external heat flux of 50 kW m-2. The parameters determined through analysis of the milligram-scale data were used to construct a pyrolysis model that predicted the total mass loss from calorimeter tests in anaerobic conditions. A condensed phase pyrolysis model that accurately predicts in-depth temperature profiles of a solid fuel, and the mass flux of volatiles evolved during degradation of the fuel, is an essential component of a comprehensive fire model, which when coupled to a computational fluid dynamics code can be used to predict the burning processes in a fire scenario. Pyrolysis models vary considerably in complexity based on the assumptions incorporated into the development of the model.