Linear Low Density Polyethylene Composites Research Articles

Filler effect of potato starch and urea on degradation of linear low density polyethylene composites

Starch and urea are used as fillers, owing to their good mechanical and degradable properties, in linear low density polyethylene matrix. Composites of varying amount of starch and urea composition are prepared. Various properties like tensile strength, elongation at break, Young's modulus, shore-D hardness, and water absorption are studied. The tensile strength, elongation at break, Young's modulus, and Shore-D hardness decrease with maleic anhydride treatment of starch and urea for polymer composites. On increasing the amount of filler in the composites, the mechanical properties decrease. The soil-burial treatment of these composites also causes reduction in these properties. The absorption of water increases for one month and decreases later during the period 2–5 months. The increase in absorption might be due to the onset of degradation of composites. The degradation of the composites is also observed by the presence of grooves and pits in optical micrographs of soil-exposed composites.

Tensile property and interfacial dewetting in the calcite filled HDPE, LDPE, and LLDPE composites

Mechanical properties and complex melt viscosity of unfilled and the calcite (calcium carbonate: CaCO 3) filled high density polyethylene (HDPE), low density polyethylene (LDPE), and linear low density polyethylene (LLDPE) composites using dumbbell bar and film specimens are studied. In addition, the formation of air holes between calcium carbonate and the resin matrix was investigated from the phase morphology and interfacial behavior between the above constituents upon stretching using scanning electron microscopy. The tensile stress and the complex melt viscosity of the calcite filled (50%) polyethylene composites were higher than that of unfilled ones, implying that the reinforcing effect of calcium carbonate. The crack was initiated up to first 50% elongation along the transverse direction and the formation of air holes was originated by dewetting occurring through machine direction in the interface between calcium carbonate surface and HDPE. The propagation mechanism of the air hole formation was proposed to firstly originate by dewetting up to 300% elongation, and enlarged not only by breaking of a superimposed fibril structure, but also by merging effect air holes between fibrous resin matrix. However, the crack propagation was not observed at the very beginning elongation for the calcite filled LDPE and LLDPE systems. Less fibril structure was observed in LLDPE, then LDPE composites. The observed shape and the average size of the air holes were different from system to system. This sort of different interfacial behavior and mechanical properties may arise from different configuration of polyethylene.

Thermal degradation of magnesium hydroxide and red phosphorus flame retarded polyethylene composites

The thermal degradation of flame-retarded linear low-density polyethylene (LLDPE) composites containing magnesium hydroxide (MH) and red phosphorus (RP) has been studied by thermogravimetric analysis, real time Fourier transform infrared (FTIR) and pyrolysis gas chromatography mass spectrometry (Py-GC/MS). The Kissinger and Flynn–Wall methods were used to calculate the apparent activation energy ( E a) of the degradation of LLDPE and LLDPE composites. The FTIR studies show that addition of MH to LLDPE improves the thermo-oxidative stability, especially LLDPE/MH composites with suitable amount of RP at higher temperatures. The Py-GC/MS data indicate that incorporation of RP into the LLDPE/MH composite results in a change of pyrolysis mode and thus a great increase of the amounts of compounds with high molecular weights.

Degradation studies and moisture uptake of sago-starch-filled linear low-density polyethylene composites

The degradation and moisture uptake of sago-starch-filled linear low-density polyethylene (LLDPE) composites have been studied. Enzymatic hydrolysis of the composites apparently involves surface starch granules; embedded granules are not easily accessible because of the poor moisture absorption or transmission property of the matrix. Exposure of the composites to weathering resulted in massive deterioration typified by turbidity, discoloration, embrittleness and dimensional changes. Soil burial led to a drop in the pH of the soil and the presence of holes on the samples, probably due to microbial activity. Furthermore, the drop in mechanical properties of the composites increased with time of burial for the first four months and decreased gradually thereafter. Moisture uptake increased with increased starch content and immersion time. The time taken for the composites to equilibrate was about three months even when they were immersed completely in water. The mechanical properties of the composite also dropped with increasing moisture uptake.

Dynamic mechanical behavior of LCP fiber/glass fiber–reinforced LLDPE composites

AbstractLiquid crystalline polymer (LCP) fibers and glass fibers have been used to rein force linear low density polyethylene (LLDPE) by using an elastic melt extruder and the compression molding technique. The impact behavior of hybrid composites of different composition is compared and is explained on the basis of the volume frac tion of the fibers. Addition of glass fibers decreases the Izod impact strength LLDPE. The impact strength of the composites increases when glass fibers are placed by LCP fibers. Dynamic mechanical α and β relaxations are studied and effect of variation of fiber composition on these relaxations is reported in the tem perature range from −50 to 150°C at 1 Hz frequency, a relaxation shifts toward higher temperatures with addition of fibers in LLDPE. Addition of fibers increases the storage modulus of LLDPE.

A study on the effect of pro-oxidant on the thermo-oxidative degradation behaviour of sago starch filled polyethylene

The degradation of linear low density polyethylene (LLDPE), formulated with sago starch, elastomers, viz. styrene butadiene rubber and epoxidised natural rubber and a metal salt, was studied to evaluate the effect of different material compositions on the overall degradation process. LLDPE and its composites were prepared using an internal mixer at 150°C a rotor speed of 20 rpm. Results indicate that the incorporation of up to 6 wt.% sago starch into LLDPE produced composite with a good combination of strength and toughness. Thermo-oxidative aging (TOA) of LLDPE and its composites were carried out in an air oven at 70°C for a maximum period of four weeks. The progress of TOA was followed by monitoring physical and chemical changes of the samples by using tensile tests and fourier transform Infra-red spectroscopy and scanning electron microscope. TOA studies revealed that the incorporation of pro-oxidant which consisted of metal salts and unsaturated elastomer enhanced the degradation rate of sago starch filled LLDPE composites.

Migration phenomena of surfactants in polyethylene film

Migration diffusion coefficients of two surfactants (sorbitan laurate, SPAN-20 and sorbitan palmitate, SPAN-40) in polyethylene blend are calculated in the desorption process by means of Fourier transform infrared (FT-IR) spectroscopy technique at 25°C. They are 2.31 and 2.24 × 10−11 cm2/s, respectively, which show no significant dependency of molecular weights of the surfactants on diffusion. The composition of LLDPE (linear low-density polyethylene) and LDPE (low-density polyethylene) in LLDPE blend is a 7 : 3 ratio, and ethylene acrylic acid (EAA) copolymer is used to verify its role as a migration controller. The key factor affecting the diffusion of the surfactant is suggested to be the segmental mobility by the semicrystalline LLDPE blend. Incorporation of 20 wt% EAA in the LLDPE blend retards the migration rate of the surfactants by reducing the diffusion coefficients to be 9.6 and 7.7 × 10−12 cm2/s and this is believed to be due to the blocking effect of EAA. Although the diffusion coefficient was varied from system to system, the migration kinetics of the surfactants in short times obeys the Fickian behavior if the experimental error is allowed. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1387–1395, 1999

13C NMR Determination of the Composition of Linear Low-Density Polyethylene Obtained with [η3-Methallyl-nickel-diimine]PF6 Complex

A complete 13C NMR characterization of two linear low-density polyethylenes (LLDPE), one highly branched and the other lowly branched, is presented. These LLDPE were synthesized with a new catalyst: the [η3-methallyl-nickel-dad]PF6 complex by homopolymerization of ethylene, using different experimental conditions. Methyl, ethyl, propyl, butyl, amyl, and long branches were assigned and quantified.

LLDPE Composites Filled with Corona Discharge Treated Ground Rubber Tire Crumb

The effects of corona discharge treatment (CDT) of ground rubber tire crumb (GRT) on the impact property of the thermoplastic composites containing GRT have been investigated. The composites were prepared by melt blending 40% GRT (average mesh size 40) into a linear low density polyethylene (LLDPE) matrix. Ethylene-co-glycidyl methacrylate polymer (IBE) was used as a compatibilizer. X-ray Photoelectron Spectroscopy (XPS) analysis shows that the corona discharge treatment of GRT increases the oxygen containing groups on the ground rubber surface. The CDT conditions such as the exposure time and power input for CDT have a moderate influence on the increase in oxygen concentration on the ground rubber surface. In some composites it has been found that treated-GRT marginally improved the impact property of the composites. However, prolonged times of treatment and higher power inputs for corona discharge of GRT reduce the impact strength of the composites. The improvement in impact energy in the former case is believed to be because of better interaction between the epoxy groups of the compatibilizer and the oxygen containing groups on the ground rubber surface. While in other cases the decrease in impact property may be the result of hardening of the GRT surface and/or differing levels of aging and rubber composition in worn tires before grinding.

Use of grafted aspen fibers in thermoplastic composites: IV. Effect of extreme conditions on mechanical properties of polyethylene composites

AbstractHardwood fibers of aspen in the form of chemithermo‐mechanical pulp (CTMP) have been used as reinforcement in linear low density polyethylene (LLDPE). The effect of composite treatment (immersion in boiling water, heat exposure at 105°C for seven days or at a temperature of −40°C) on resulting mechanical properties were evaluated. The grafted aspen CTMP composites showed by far the best results with regard to secant modulus, tensile strength, energy, and strain when compared to those of wood flour, mica or glass–fiber filled LLDPE, as well as to virgin LLDPE. Finally, the dimensional stability of CTMP aspen‐filled LLDPE composites immersed for four hours in boiling water was better than that of mica or glass–fiber filled LLDPE.