Halogen-free flame-retardant compounds. Thermal decomposition and flammability behavior for alternative polyethylene grades

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)

Mineral and chemical composition of kaolins from Milos Island, Greece - procedure of kaolinite enrichment

Kaolins from three areas of Milos Island show mineral and geochemical similarities. Kaolin from the Rallaki area consists of the following minerals: kaolinite, quartz, cristobalite and alunite. Kaolin from the Kastriani area consists of kaolinite, quartz and cristobalite. Based on the mineral and chemical composition and texture of these kaolins, a method of enrichment by means of liquid separation was applied to obtain material of high quality. In the process of coarse grinding was liquid separation up to 20 μm, no substantial differentiation was apparent in the distribution of the minerals with grain size, while in the procedure of fine grinding and liquid separation up to 2 μm, the picture is more auspicious, especially with respect to quartz. © 1991

Mineral and chemical composition of kaolins from Milos Island, Greece - procedure of kaolinite enrichment

Kaolins from three areas of Milos Island show mineral and geochemical similarities. Kaolin from the Rallaki area consists of the following minerals: kaolinite, quartz, cristobalite and alunite. Kaolin from the Kastriani area consists of kaolinite, quartz and cristobalite. Based on the mineral and chemical composition and texture of these kaolins, a method of enrichment by means of liquid separation was applied to obtain material of high quality. In the process of coarse grinding was liquid separation up to 20 μm, no substantial differentiation was apparent in the distribution of the minerals with grain size, while in the procedure of fine grinding and liquid separation up to 2 μm, the picture is more auspicious, especially with respect to quartz. © 1991

Development of value-added polyethylene grades with extended service lifetime: Weathering resistant flame retarded materials for outdoor applications

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).Scopu

Accelerated ageing and hydrolytic stabilization of poly(lactic acid) (PLA) under humidity and temperature conditioning

The accelerated hygrothermal ageing of two commercial poly(lactic acid) grades, a semi-crystalline and an amorphous one, was studied in order to establish a baseline degradation mechanism and kinetics. In particular, the water uptake, the molecular weight, the carboxylic end groups concentration and the thermal properties were monitored during the course of humidity and temperature conditioning at 70 °C and 80% relative humidity (RH), revealing significant extent of chain scission. The effect of four commercial anti-hydrolysis agents of different composition was then examined in order to stabilize the two PLA grades. The additives comprised an epoxy-based chain extender, an aromatic carbodiimide, as well as an aromatic and an aliphatic polycarbodiimide. The epoxy-based additive did not exhibit any stabilizing effect, while the other three carbodiimide-based additives were found efficient as anti-hydrolysis agents at a concentration of 1% especially in the case of the amorphous grade

Artificial weathering and accelerated heat aging studies on low-density polyethylene (Ldpe) produced via autoclave and tubular process technologies

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).Scopu