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

Abstract

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.

Flame-Retarded and Heat-Resistant PP Compounds for Halogen-Free Low-Smoke Cable Protection Pipes (HFLS Conduits)

“…Accordingly, the two FR compounds exhibited a more slowly increasing trend of tensile strength (σ max , Figure 5a), ending up at 2000 h at a total deviation in the range of 17-19%. Especially for the initial 500 h, the relative increase in tensile strength can be due to annealing of the polymer [19]. Regarding the strain at break (ε max , Figure 5b) and Young's modulus (Figure 5c), no clear trend was observed, as anticipated, due to embrittlement: FR1 was quite stable throughout the ageing time, ending up with an insignificant reduction of ε max in the range of ca.…”

“…Regarding impact strength values (Table S2), in FR1, where the FR loading is 11 wt.%, an increased a iu compared to reference PP was determined, unlike in the case of FR2, where the low loading of 4 wt.% did not seem to significantly affect the a iu . In terms of tensile properties, the FR compounds at both total loadings (11 and 4 wt.%) exhibited similar values for Young's modulus and stress at yield (tensile strength) with reference PP, but they presented a more brittle and stiffer behavior based on the strong decrease in the strain at break (ε max ), with RSD values between 10% and 20% [19,48].…”

“…Typically, polyolefins with increasing ageing time exhibit oxidative degradation triggered by heat and/or UV radiation in the presence of oxygen [15,39,40]. In terms of tensile properties, PP, upon ageing, typically exhibits an increase in the Young's modulus (E), with a strong reduction in the elongation at break, a behavior well-known as embrittlement [19,48,[51][52][53][54]. This was observed clearly for reference PP (Figure 5).…”

Enhancing the UV/heat stability of LLDPE irrigation pipes via different stabilizer formulations

“…The stabilized heat‐aged samples were not observed by SEM, as they are expected to maintain their smooth surface, since HALS is known to contribute also to long‐term thermal stability. [ 15,29,32 ]…”

“…Moreover, this work is a precursor for examining the performance of the pertinent systems when combined with halogen‐free flame‐retardants. [ 29 ] In particular, the combination of the two functionalities—flame retardance (FR) and weathering stability—is studied in very few papers on polyolefins and the retention of FR properties after UV exposure consists of a challenge due to the fact that synergistic and/or antagonistic actions can be present. [ 30–32 ] Accordingly, the effect of different HALS and UV‐A was herein investigated for LLDPE by means of twin‐screw extrusion so as to induce the first functionality of UV stability.…”