Mechanical, thermal, diffusion and degradation properties of high density polyethylene ‘and’ cellulose blends
Agan, Paul Okelo
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Advanced technology in petrochemical based polymers has brought many benefits to mankind. However; it has become evident that the ecosystem is being disturbed because of non-biodegradable plastic materials. The environmental impact of persistent plastic wastes is growing into a more global concern. Currently, there is considerable interest in biodegradable polymers, which can be used as alternatives to traditional plastics, thus reducing the pollution caused by plastic wastes. The main aim of this work was to recognize the basic properties of polyethylene ‘and’ cellulose blends and to investigate how the content of cellulose and polyethylene ratio reflects onto relaxation properties of this blend. The study focused on the preparation of thermoplastic blends based on high density polyethylene and cellulose and their propensity to environmental degradation as promoted by bio-fragmentation. The dynamic mechanical analyses were carried out in the frequency range from 1 to 30 Hz and temperature range from -30oC to 120oC. The effects of the concentration on relaxation processes were observed. Creep measurements were performed at 30oC, 40 oC, 50oC and 60oC. The time for application of force was 12 minutes and sample allowed to relax for 12 minutes. Diffusion measurements was done at room temperature and monitored by measuring the mass difference at specific periods of time. Thermal degradation was done by lindberg blue tube furnace .The models of analysis for DMA and Creep data were Vogel-Fulcher-Tamman(VFT) or William-Landel-Ferry(WLF) and Arrhenius laws whereas in diffusion measurements Fick’s second law was used. The dynamic mechanical analysis measurement indicated significant increase of the storage modulus and Loss modulus of HDPE/CELL; depending on the cellulose content in the HDPE matrix. One relaxation process was observed which was assigned to main chain motion followed Vogel-Fulcher-Tamman (VFT) law. There was also a shift towards a higher value of glass transition temperature of the HDPE/CELL as cellulose loading increased. This implies increased resistance to deformation of the blend. TGA measurements for all blends showed two step weight loss. The activation energy of thermal degradation of the blends decreased with cellulose intake. This implied decreased thermal stability. Creep analysis showed that the creep decreased with increase of cellulose loading in the blend and also increased with increase of time and temperature. Temperature dependence of storage master curves follows William-Landel-Ferry (WLF) law. The time-temperature superposition principle master curves indicated prediction of the long-term property of composites and extend up to more than 106s in time scale. Diffusivity also increased with cellulose intake. Rate of biodegradation increased with cellulose loading. .