High Density Polyethylene Mixtures Research Articles

Degradation of high density polyethylene, polypropylene and their mixtures in supercritical acetone

The degradation of high density polyethylene (HDPE), polypropylene (PP) and their mixtures was carried out in supercritical acetone under the reaction temperature ranging from 450 ‡C to 470 ‡C, pressure ranging from 60 atm to 100 atm and reaction duration time as 60 min. The yields of gas, oil and wax components and the compositions and distributions of liquid-like products were measured by means of gas chromatography and gas chromatography/mass spectrometer. In every run, the reaction was completed in 30 min after reaching the prescribed temperature. The yields of oil and gas degraded from PP were not greatly influenced by the temperature, whereas in HDPE, the yields of oil decreased and that of gas increased, respectively, with rising temperature. The yields of oil from HDPE and PP increased with increasing pressure up to 7 atm and the values under higher pressure remained almost constant, i.e., 88% for HDPE and 96% for PP. Correspondingly, the yields of wax from HDPE and PP decreased with increasing pressure below 75 atm and above the value they remained almost constant, especially zero with PP. Generally, the degradation performance was influenced by the temperature rather than applied pressure. For the degradation of mixtures of HDPE and PP, with increasing PP composition, the yield of oil increased, whereas that of wax decreased, and above 80% of PP composition, it decreased to zero. For example, the yields of oil, wax and gas from a 52 wt% HDPE-48 wt% PP mixture, amounted to 90 wt%, 1 wt% and 9 wt%, respectively. The yield of wax decreased with increasing PP percentage.

HDPE/ROSIN blends: I-Morphology, mechanical and rheological properties

Melting mixtures of high density polyethylene (HDPE) and glycerol ester of hydrogenated rosin (ester gum) were prepared under select conditions using up to 50% of rosin. All blends showed phase separation. The size of rosin domains varied with the content of low molecular weight constituent. The 50/50 blend showed the highest dispersion and the presence of micro and macro rosin domains. Up to 20% rosin a slight decrease of Young's modulus was noticed while above this rosin content a slight increase occurred. The stress and elongation dropped markedly above 10% of rosin. The hardness of blends showed the same behavior as the elastic modulus. The melt flow index increased exponentially with the rosin content while processability has improved.

Microwave welding of high density polyethylene using intrinsically conductive polyaniline

AbstractThe use of intrinsically conductive polymers in welding of plastics and composites offers the possibility of developing new welding methods. Intrinsically conductive polyaniline (PANI) composite gaskets were used to microwave weld high density polyethylene (HDPE) bars. Two composite gaskets were made from a mixture of HDPE and PANI powders in different proportions. Adiabatic heating experiments were used to estimate the internal heat generation and electric field strength in the gasket. During welding, the effects of heating time, heating pressure and welding pressure were evaluated. It was found that increasing the heating time and the welding pressure increased the joint strength. The maximum tensile joint strength was achieved using a 60 wt% PANI gasket with a heating time of 60 sec and a welding pressure of 0.9 MPa; this resulted in a tensile weld strength of 24.79 ± 0.34 MPa, which equals the tensile strength of the bulk HDPE.

Thermal degradation of polymer-fire retardant mixtures: Part V—Polyethylene-chloroparaffin mixtures

Volatilisation of mixtures of high density polyethylene (PE) with a fire retardant chloroparaffin (CP) occurs in two separate steps on programmed heating. CP eliminates HCl at 250–370°C whilst, at 400–530°C, hydrocarbons are formed by quantitative volatilisation of PE. However, chlorine radicals which propagate the thermal dehydro-chlorination of CP induce crosslinking of PE. Furthermore, in the presence of CP, a larger ratio of saturated to unsaturated hydrocarbons is obtained than from PE alone. The fire retardant activity of CP in PE-CP mixtures, although slight, is likely to be of the ‘condensed phase’ type. This is in agreement with the separate evolution of the flame inhibitor HCl, and flammable hydrocarbons and with the change in the composition of the hydrocarbons evolved by PE degrading in the presence of CP.

Fibre formation in injection-moulded polyethylene-sodium lignosulphonate blends and its relationship to the morphological zones

In injection-moulded parts, the degree of orientation (anisotropy) varies over the cross-section. Normally, such parts exhibit a layered structure, with a biaxially oriented surface layer (stretching of the flow front during mould filling), a highly oriented shear zone, and a core region with a relatively low orientation. This paper describes a novel method to show the different morphological zones by studying the occurrence and structure of fibres formed during injection moulding of certain incompatible blends, in the present case a mixture of high-density polyethylene and a technical lignosulphonate grade (Wanin S). The polyethylene fibres formed during processing of this composite were ribbon-shaped in the surface layer (biaxial orientation), while they had a normal appearance in the shear zone. Only relatively few fibres were found in the core region. A qualitative agreement was found when the fibre character in the various layers was compared with orientation data from thermal shrinkage measurements, as obtained with pure polyethylene samples (test bars).