Degradation Of Linear Low Density Polyethylene Research Articles

Effects of Pine Needle Extracts on the Degradation of LLDPE.

Polyolefin suffers from degradation during processing and application. To prolong the service life, antioxidants are needed in the packing formula of polyolefin products. The usage of natural antioxidants could avoid potential health hazards aroused by synthetic ones. Pine needles have long lives and hardly rot, suggesting their high resistance to degradation. To provide a new candidate of natural antioxidants and add more value to pine needles, pine needle extracts (PNE) were investigated as the antioxidant of linear low-density polyethylene (LLDPE). PNE-modified LLDPE (PE-PNE) exhibited much better short-term and long-term aging resistance than pure LLDPE (PE): Oxidation induction time (OIT) of PE-PNE was 52 times higher than that of PE, and the increments of carbonyl index (CI) of PE-PNE-1st samples placed under daylight and in the dark were approximately 75% and 63% of PE under the same conditions. It could be attributed to the attractive antioxidant capacity of PNE (IC50 of DPPH radical scavenging was 115 μg/mL). In addition, the PE-PNE sample showed high processing stability and maintenance of the mechanical property during multiple extrusions: only a 0.2 g/10 min decrease in melting flow rate was found after five extrusions; the tensile strength and elongation at break were almost unchanged. All results reveal that pine needle extracts could play a role in LLDPE stabilization. Moreover, as pine needles are mainly considered a kind of waste, the present study would benefit the budget-reducing polyolefin industry.

Eco-sustainable design of humic acids-doped ZnO nanoparticles for UVA/light photocatalytic degradation of LLDPE and PLA plastics

The mismanagement of plastics is associated with high levels of waste and release into the environment, where they can persist for long times due to the low degradation rate. Photocatalytic methods, based on the action of Reactive Oxygen Species (ROS) generated by semiconductor materials, are promising eco-friendly and low-cost process for the plastics degradation. Here, eco-designed Humic Acids-doped/ZnO nanoparticles were synthesized via solvothermal route and tested as photocatalysts for the degradation of linear low-density polyethylene (LLDPE) and polylactic acid (PLA) thin films, under UVA/light irradiation. LLDPE is one of the most common commercial polymers widely used in packaging field wherein PLA is also broadly used to replace conventional plastics. The combination of analytical techniques allowed to define the structure-property-function relationships of the hybrid nanomaterials and to monitor the chemical, structural and morphological changes occurring on the polymeric films as a consequence of the photodegradation. Experimental results demonstrated the validity of this eco-sustainable approach to realize hybrid photocatalysts with enhanced ROS-generating ability suitable for an improved photo-oxidation of plastics in aqueous environment.

Thermal Properties of Olive Pomace Filled Linear Low Density Polyethylene Bio-Composites

Differential scanning calorimetry (DSC) and thermo-gravimetric analysis (TGA) were performed to evaluate the influence of olive pomace flour (OPF) and a coupling agent (C) on linear low-density polyethylene (LLDPE) bio-composites. The glass transition temperature (Tg ), melting temperature (Tm ), enthalpy of fusion (ΔHm ), crystallization temperature (Tcryst .), heat of crystallization (ΔHcryst ,) and percent crystallinity (Xc ) were extracted from the DSC results. The degradation behavior was extracted from the TGA. Tg value (–114 °C) was unaffected by the addition of both OPF and C. A sharp DSC Tm peak, around 125 °C, was observed with its position being dependent on both filler and C contents. The ΔHm for the filler at 40% content decreased slightly, from 132 J/g for 0% filler to 123 J/g. TGA showed that the thermal degradation of LLDPE in the composite became easier upon increasing the OPF filler and coupling agent.

Catalytic degradation of linear low-density polyethylene over HY-zeolite via pre-degradation method

The catalytic degradation of linear low-density (lldPE) polyethylene over HY-zeolite catalyst was studied in a semi-batch reactor. One of the important problems encountered during catalytic pyrolysis of macromolecules is the contact with the catalyst, which is known to affect the product distribution and the quality of the coke formed. A pre-degradation procedure was introduced to achieve efficient contact between the LLDPE macromolecules and the catalyst. The influence of the pre-degradation to the reaction conditions including holding time, temperature, polymer to catalyst ratio and flow rate of carrier gas was examined. Moreover, the pre-degradation results were compared with the results obtained using normal mixing procedure. The results obtained showed that, pre-degradation promotes the liquid fraction by a factor of more than one-fold increase at the expense of the gas fraction and the coke yield. The optimal liquid fraction with pre-degradation was obtained at low reaction temperature and catalyst amount respectively, i.e. high polymer to catalyst ratio, making it economically viable method for the degradation of lldPE.The coke content was analysed using TGA in nitrogen atmosphere to remove the soft coke and then in air isothermally at the final temperature to burn the hard coke. The TGA results of the coked sample show less concentration of coke components on the catalyst using the pre-degradation method as compared to the normal mixing which shows high concentration of coke components especially at low reaction temperature. Moreover, the majority of the coke components produced using the pre-degradation method were soft coke, making it more efficient for the re-usability of the catalyst.The liquid samples collected were analysed using gas chromatography and the products distribution were presented in the form of boiling point distribution curves. The bulk of the liquid products produced were lighter fractions with a peak around the gasoline range.

Effect of trace chloride on the char formation and flame retardancy of the LLDPE filled with NiAl‐layered double hydroxides

SummaryLayered double hydroxides (LDHs) have received intensive attentions for the potential as flame retardants of polyolefin. In the work, trace amounts of chloride were investigated for their synergistic effects on the char formation and flame retardancy of the linear low‐density polyethylene (LLDPE) filled with NiAl‐LDHs. Results showed that 0.5 wt% of NH4Cl incorporation enabled the char yield of 20%LDH/LLDPE (20 wt% of NiAl‐LDH) increase from 10.4% to 49.6%. Other chlorides likewise offered significant increase in the char yield of 20%LDH/LLDPE. With the flame‐retardant measurements of cone calorimeter and limiting oxygen index device, it is revealed that the flame retardancy of LLDPE filled with NiAl‐LDHs could be greatly improved when trace amounts of NH4Cl were further introduced. Thermal stability analysis illustrated that the presence of NiAl‐LDHs or NH4Cl all had positive effects on the thermal stability of LLDPE, in which the chlorides influenced the LLDPE thermal stability via direct participation in the degradation of LLDPE. The synergetic mechanism analysis reveals that the introduction of chloride enabled the LLDPE decomposed products have more tendency to grow carbon nanotubes with the presence of NiAl‐LDH catalysts. Finally, the mechanical properties of LLDPE filled with NiAl‐LDHs and NH4Cl were also investigated.

Weather-Induced Degradation of Linear Low-Density Polyethylene: Mechanical Properties

Abstract Plastics degrade through the influence of such factors as the sun's radiation, temperature, humidity, rain, the oxygen content of the air, and atmospheric pollutants. The most deleterious of these effects is radiation, which is responsible for breaking up polymer chains. The sun emits a complete spectrum of energy radiation, with waves similar in physical structure but varying in length and therefore in photon energy. Wavelength has an inverse relationship to quantum energy, as shown in Fig. 1.