Biopolymer composite based on natural and derived hemp cellulose fibres

The aim of this research was to study the effect of pre-treatment and modification processes on the properties of hemp cellulose fibre for biopolymer composites application. Hemp fibres have been modified by various extraction, swelling, chemical and enzymatic treatments. The morphology and mechanical properties of the modified fibres have been measured. Biopolymer composites have been prepared using the modified fibres and matrices of cellulose acetate butyrate and cellulose solutions derived from hemp. The first fibre treatment employed was acetone extraction and mercerization. A low pressure acrylonitrile grafting initiated by azo-bis-isobutylonitrile was performed using alkali treated fibre. The AN grafted fibres had no transformation of crystalline structure as observed after mercerization. The mechanical properties performed by a single fibre test method were strongly influenced by the cellulose structure, lateral index of crystallinity, and fraction of grafting. Bioscouring of hemp using pectate lyase (EC 4.2.2.2), Scourzyme L, was performed. Greater enzyme concentration and a longer treatment improved the removal of the low methoxy pectin component. Removal of pectate caused no crystalline transformation in the fibres, except for a slight decline in the X-ray crystalline order index. Smooth surfaces and separated fibres were evidence of successful treatment. The shortening of fibre by grinding and ball-milling was introduced to achieve a desired fibre size. An increase in the milling duration gradual ly destroyed the crystalline structure of the cellulose fibres. An increase in solvent polarity, solvent-fibre ratio, agitation speed and drying rate resulted in the rearrangement of the ball-milled cellulose crystalline structure to a greater order. The thermal degradation behaviour of hemp fibres was investigated by using TGA. The greater activation energy of treated hemp fibre compared with untreated fibre represented an increase in purity and improvement of structural order. The all hemp cellulose composites were prepared by an introduction of fibres into 12% cellulose N-methyl-morpholine N-oxide (NMMO) solution and water-ethanol regeneration. A broadening of the scattering of the main crystalline plane, (002) and a depression of the maximum degradation temperature of the fibres were observed. These revealed a structural change in the fibres arising from the preparation. The mechanical properties of composites depended on size, surface area, crystallinity and the structural swelling of the fibres. Composites of cellulose acetate butyrate (CAB) and modified hemp fibres were prepared. Composites containing pectate lyase enzyme treated fibres showed better mechanical property improvement than untreated and alkali treated fibres respectively

Preparation of Pectin–ZnO Nanocomposite

Pectin–ZnO nanocomposite was prepared in the aqueous solution condition at room temperature. The Fourier transform infrared, X-ray diffraction, and transmission electron microscope (TEM) measurements confirmed the nanoscaled structure of pectin–ZnO composite. According to the TEM observation, the average composite granules size was about 150 nm and the embedded ZnO nanoparticles were uniform with an average diameter of 70 nm

Biocomposites of cellulose acetate butyrate with modified hemp cellulose fibres

Cellulose acetate butyrate biocomposites, plasticized with tributyl citrate at volume fraction Vf = 0.1-0.3, were prepared with modified hemp. Inclusion of modified hemp fibres at Vf = 0.4 enhanced the modulus and strength of the flexible plasticized cellulose acetate butyrate. Composites containing pectate lyase enzyme treated fibres showed a modulus greater than untreated or alkali treated fibres, when compared at a similar fibre length of 100 µm. Composites containing the shortest alkali treated fibres of 45 µm gave the greatest property improvement, while 500 µm fibres showed worsened properties. Ball-milled fibres provided reduced values of properties due to cellulose structural disruption, while compression moulding gave better compaction by removing voids

Preparation, structure and mechanical properties of all-hemp cellulose biocomposites

All-hemp (Cannabis sativa L.) cellulose composites were prepared by a mechanical blending technique followed by hot pressing and water-ethanol regeneration. The alkali treated fibres were ground and sieved to a size ranging from 45 µm to 500 µm. Introduction of fibres into 12% w/v cellulose N-methyl-morpholine-N-oxide (NMMO) solution was performed with low solution viscosity at 100 °C. The solid mixtures were cut and heat pressed between heated glass and PTFE plates at 85 °C to obtain a flat smooth-surfaced composite sheet of approximately 0.2 mm thickness. The cellulose was regenerated in a 50:50 water¿ethanol mixture that subsequently removed NMMO and stabilizer (Irganox 1010, Ciba) from the composite. FTIR and X-ray diffraction measurements were performed to investigate the structural change of cellulose from fibre into partially regenerated composite. Composition and thermal stability of composites were investigated using thermogravimetry. A broadening of the scattering of the main crystalline plane (0 0 2) and a depression of the maximum degradation temperature of fibre were observed. The observations revealed a structural change in the fibres. The mechanical properties of composites depended on size, surface area, crystallinity and the structural swelling of fibres

Melting and crystal rearrangement of polypropylenes with comparison of various modulated temperature differential scanning calorimetry techniques

Many grades of polypropylene (PP) are available with varying tacticity, comonomers and comonomer content and distributions. These PP differ in crystaIlinity, crystal perfection, melting temperature and crystal equilibration. Differential scanning calorimetry (DSC) techniques are available to study crystal melting processes using continuous temperature scanning, stepwise isothermal scanning and temperature modulation scanning. Examples of these DSC techniques\ave been applied to investigate the melting characteristics of PP with varying tacticity, ethylene or butene comonomers, and varying comonomer content and distribution. The results distinguish the PP morphologies and provide a comparison related to the applications of each PP

Solvent and enzyme induced recrystallization of mechanically degraded hemp cellulose

The structural degradation of cellulose fibre from hemp (Cannabis Sativa L.) by a ball-milling process and the recrystallization behavior of the product were studied. A linear increase in the Brunauer-Emmett-Teller specific surface area was observed; indicating the fibre bundles were being crushed and disrupted to single fibres, which was confirmed by SEM. An increase in the milling duration gradually destroyed the crystalline structure of the cellulose fibres, observed by a reduction of the 002 plane intensity in wide angle X-ray scattering measurements. The crystalline order index calculated from the area ratio of the 002 to the 021, 10 (1) over bar and 002 planes was decreased from 65 to 36 after milling for 330 min. Subsequently the lower thermal stability of ball-milled fibre was observed from a decrease in the temperature at the maximum mass loss rate using thermogravimetry. An increase in solvent polarity, solvent-fibre ratio, agitation speed and drying rate resulted in the rearrangement of ball-milled cellulose crystalline structure to a greater order. Moreover, an increase in the BET specific surface area and the amorphous fraction improved the scouring efficiency of the ball-milled cellulose using the pectate lyase enzyme (EC. 4.2.2.2)

Composition, structure and thermal degradation of hemp cellulose after chemical treatments

The thermal degradation behaviour of hemp (Cannabis sativa L.) fibres under a nitrogen atmosphere was investigated by using thermogravimetry (TGA). The kinetic activation energy of treated fibres was calculated from TGA data by using a varied heating rate from 2.5 to 30 °C/min. The greater activation energy of treated hemp fibre compared with untreated fibre represented an increase of purity and improvement in structural order. A hydrophobic solvent affected the degree of non-cellulosic removal. Mercerisation and enzyme scouring removed non-cellulosic components from the fibre; however, structural disruption was observed after higher alkaline concentration, 20 %wt/v and longer scouring time, respectively. Structural disruption was observed by X-ray measurement. The FTIR results indicated an elimination of the non-cellulosic components by the mercerisation treatment and a specific removal of low methoxy pectin by use of pectate lyase enzyme (EC 4.2.2.2). An increase of temperature at the maximum rate of degradation and the rate of weight loss was characteristic of the purity and structure of treated hemp fibre

Morphology and structure of hemp fibre after bioscouring

Bioscouring of hemp (Cannabis Sativa L) using pectate lyase (EC 4.2.2.2), Scourzyme L, was performed at 55 degrees C and pH 8.5 in a nonagitated system. The enzyme concentration, treatment time and substrate concentration were varied to obtain the kinetic constants, K-m and V-m. Greater enzyme concentration and a longer treatment improved the removal of the low methoxy pectin component as indicated by UV spectroscopy. Removal of pectate caused no crystalline transformation in the fibres, except for a slight decline in the crystallinity order index analysed by Fourier Transform infrared spectroscopy and wide angle X-ray diffraction. This corresponded well with the single fibre bundle tensile mechanical properties test. Smooth surfaces and separated fibres observed using SEM images were evidence of successful treatment, supported by weight loss at low temperature of a pectic substance. After treatment, the pectin substance was no longer observed during thermogravimetry. An increase in surface area and pore size after scouring were further evidence of modification