Search results for " polyethylene"

Durability of Basalt/Hemp Hybrid Thermoplastic Composites

2019

The Achilles heel of thermoplastic natural fibre composites is their limited durability. The environmental degradation of the mechanical properties of hemp and hemp/basalt hybrid-reinforced high-density polyethylene (HDPE) composites has been investigated with a special focus on the effects of water ageing and accelerated ageing, including hygrothermal and UV radiation. Modification of the matrix was carried out using a maleic anhydride high-density polyethylene copolymer (MAPE) as a compatibilizer. Hybridization of hemp fibres with basalt fibres and the incorporation of MAPE were found to significantly decrease the water uptake (up to 75%) and increase the retention of mechanical propertie…

Finely tuned nickel complexes as highly active catalysts affording branched polyethylene of high molecular weight: 1-(2,6-Dibenzhydryl-4- methoxyphen…

2018

Abstract A series of unsymmetrical 1,2-bis(imino)acenaphthenenickel(II) halides containing N-2,6-dibenzhydryl-4-methoxyphenyl – a single bulky group with adjusted electron donating properties – has been synthesized and characterized. These compounds adopt distorted tetrahedral geometry and their 1H NMR spectra show the paramagnetically shifted peaks. On activation with a low amount of Et2AlCl or ethylaluminum sesquichloride (EASC), these nickel complexes display high activity in ethylene polymerization, yielding the polyethylene of high molecular weight. They are also stable at elevated temperature; superb activity of 2.51 × 106 g of PE (mol of Ni)−1 h−1 can be attained at 90 °C. The result…

1989

A commercial low density polyethylene was irradiated by gamma irradiation at room temperature with different integrated doses and dose rates. The modifications induced in the material were studied by means of solubility and swelling measurements and related to structural modifications by calorimetric measurements. Results indicate that crosslinking prevails with respect to degradation at high dose rates and that the ageing phenomena occur essentially in the amorphous phase. Ein kommerzielles Polyethylen niedriger Dichte wurde bei unterschiedlicher integrierter Dosis und unterschiedlicher Dosisleistung bei Zimmertemperatur mit Gammastrahlung behandelt. Die Veranderungen des Materials wurden …

Ionic Hydrogel Based on Chitosan Cross-Linked with 6-Phosphogluconic Trisodium Salt as a Drug Delivery System.

2018

[EN] In this work, 6-phosphogluconic trisodium salt (6-PG(-)Na(+)) is introduced as a new aqueous and nontoxic cross-linking agent to obtain ionic hydrogels. Here, it is shown the formation of hydrogels based on chitosan cross-linked with 6-PG(-)Na(+). This formulation is obtained by ionic interaction of cationic groups of polymer with anionic groups of the cross linker. These hydrogels are nontoxic, do not cause dermal irritation, are easy to extend, and have an adequate adhesion force to be applied as polymeric film over the skin. This AWN formulation exhibits a first order release kinetic and can be applied as drug vehicle for topical administration or as wound dressing for wound healing…

Poly(Ethylene Glycol) Dimethacrylates with Cleavable Ketal Sites: Precursors for Cleavable PEG-Hydrogels.

2017

The authors introduce poly(ethylene glycol) (PEG) based macromonomers containing acid-labile ketal moieties as well as terminal methacrylate units that are amenable to radical polymerization. The synthesis of PEGs of different molecular weights (ranging from 2000 to 13 000 g mol-1 with polydispersities <1.15) with a central ketal unit (PEG-ketal-diol) and their conversion to PEG-ketal-dimethacrylates (PEG-ketal-DMA) is introduced. Degradation rates of both PEG-ketal-diols and PEG-ketal-DMA are investigated by in situ 1 H NMR kinetic studies in deuterated phosphate buffer. Hydrogels containing 0, 5, or 10 wt% of PEG-ketal-DMA and 100, 95, or 90 wt% of PEG-DMA, respectively, are synthesized a…

Comprehensive Study on the Performance of Waste HDPE and LDPE Modified Asphalt Binders for Construction of Asphalt Pavements Application

2022

This research is aimed at investigating the mechanical behavior of the bitumen by the addition of high-density polyethylene (HDPE) and low-density polyethylene (LDPE) obtained from waste plastic bottles and bags. Polymers (HDPE and LDPE) with percentages of 0%, 2%, 4%, and 6% in shredded form by weight of bitumen were used to evaluate the spectroscopic, structural, morphological, and rheological properties of polymer-modified binders. The rheological properties for different factors; viscosity (&#7968;) from Rotational Viscometer (RV), rutting factor G*/Sin (&delta;), fatigue characteristics G*. Sin (&delta;), for the modified binder from dynamic shear rheometer (DSR), Short and long-term a…

Necking behavior of low-density polyethylene-isotactic polypropylene blends: A morphological investigation

1984

The tensile behavior of low-density polyethylene-isotactic polypropylene blends was investigated at room temperature. Neck formation and propagation along the whole length of the samples were observed for the whole range of composition. This behavior, which is not indicated by most data available in the literature, was examined in relation to sample morphology by scanning electron microscopy. The results of this investigation indicated some differences between the morphology of these materials and the morphology of blends which do not undergo necking propagation.

Study of thermal properties of polyethylene and polypropylene nanocomposites with long alkyl chain-substituted POSS fillers

2016

The effect of incorporation of octakis({alkyl}dimethylsiloxy)octasilsesquioxanes molecules with n-octyl, n-octadecyl and 4-methyl-hexyl substituents on thermal properties of polypropylene (PP), low-density polyethylene (LDPE) and high-density polyethylene (HDPE) was investigated. Thermal properties of those composite materials were evaluated by means of the differential scanning calorimetry (DSC) and thermogravimetric analysis (TG) methods. The type and mass% content of POSS nanofillers influenced the crystallization and melting properties as well as thermal stability of the obtained polyolefin nanocomposites. The incorporated POSS particles—acting as nucleating agents—improved the crystall…

Effectiveness of organoclays as compatibilizers for multiphase polymer blends - A sustainable route for the mechanical recycling of co-mingled plasti…

2014

We prepare and characterize multiphase systems in which small amounts of recycled polymer, namely polyethylene terephtalate (PET) ground from waste bottles, are dispersed in a co-continuous blend of high-density polyethylene (HDPE) and polypropylene (PP). Some of such ternary systems are also filled with plate-like clay nanoparticles with different polarities, in order to assess their influence on the morphology and mechanical behaviour of the blends. On the basis of preliminary wettability considerations and inspections by means of scanning electron microscopy (SEM), the PET is found to preferentially locate within the PP phase. Such a positioning is desirable in order to minimize the pres…

Effect of Palletized Map Storage on the Quality and Nutritional Compounds of the Japanese Plum cv. Angeleno (Prunus salicina Lindl.)

2016

The influence of active modified atmosphere packaging MAP (10.0 kPa of O2 and 5 kPa of CO2) on palletized system was evaluated to extend the marketability of fresh plums cv. Angeleno. Fruits were wrapped with a polyethylene film in pallet bag units at 1C and 90% relative humidity for up to 60 days. The gas values of the pallet bags, the fruit weight losses and their qualitative and nutraceutical characteristics were periodically monitored to evaluate the goodness of storage. The results showed as the pallet bag have maintained the market life of Angeleno plums to up to 60 days, preserving the most important qualitative traits of fruits. After 20, 40 and 60 days the MAP treatment maintained …