Effect of compatibiliser on the biodegradation and mechanical properties of high-content starch/low-density polyethylene blends (original) (raw)
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This study presents the utilization of starch from botanical resources for the development of biodegradable materials. A thermoplastic starch obtained from cassava starch and potato starch was successfully prepared using glycerol as a plasticizer. Polypropylene matrix filled with starch along with a compatibilizer was prepared by a melt-mixing technique, using an injection molding machine at different starch contents (0 to 50 wt. %) whereas compatibilizer was used at 10 wt. % based on starch content. The effects of starch content, plasticizer and compatibilizer on the tensile, water absorption, and biodegradable properties of starch/PP blends have been investigated. Results showed that plasticized starch content exhibited an inverse relationship with the tensile strength, elongation at break and directly related to Young's modulus, water absorption index and weight loss of the starch/PP blends. However, the addition of PP-g-MA to the blends improved all the properties under study; though tensile strength and elongation at break were still lower than the neat PP. On comparison, potato starch/PP blends exhibited higher tensile, lower biodegradable and higher water absorption properties than cassava starch/PP blends due to fibre, amylose-amylopectin ratio and phosphorus contents. Biodegradation products had no adverse effects on the growth of soya bean and wheat plants. The morphology of the blends was studied using SEM and compatibilized blends showed better results.
ANALYSIS OF THE MECHANICAL AND DEGRADATION PERFORMANCES OF SELECTED STARCH/POLYPROPYLENE BLENDS
Effects of starch content and compatibilizing agent on the tensile, water absorption and biodegradability properties of starch blended polypropylene (PP) have been investigated. The starches used in this study were native cassava and sweet potato starch. Dried cassava or sweet potato starch with particle size of 0.075 mm was used at 0-50 wt. % of PP, while polypropylene graft maleic anhydride was used as a compatibilizer at 10 wt. % based on starch content. The various starch/PP blends were prepared in an injection molding machine and injected as sheets. Tensile tests were carried out using Instron tester. The water absorption test and biodegradability of the blend samples by soil burial test were investigated for a period of 90 days. Results showed that the tensile properties of the compatibilized starch/PP blends were greater than the uncompatibilized starch/PP blends particularly at higher starch content. The water absorption of the various starch/PP blends increased with increase in starch content and immersion time, and decreased on addition of PP-g-MA to the blends. The percent weight loss due to degradation of the blends was observed to increase with increase in starch content and burial period, and decreased with the incorporation of PP-g-MA into the blends. The effects biodegradation of the various starch blended PP buried in the soil on the growth of wheat and soy bean plants studied indicated that plants grow normally in the soil containing the degraded blends. The interfacial properties between starch filler and PP matrix were improved after the addition of PP-g-MA as it is evident from the fracture micrographs using SEM.
Polymer Bulletin, 2005
The use of biodegradable polymers has provided an alternative to the problem of polymer-based products discarded in the environment. Poly(ε-caprolactone) (PCL) is a biodegradable polymer that has been used industrially, but it is very expensive. Starch is a potentially useful material for biodegradable plastics because of its natural abundance and low cost. The aim of this work was to examine the effect of adding azodicarbonomide (ADC) as an expansor to blends of PCL with corn starch. Different proportions, of ADC (0.1%, 0.2% and 0.3%, w/w) were added to pure PCL and to PCL/starch (50/50) blends and their properties were studied. Biodegradable blends of PCL with starch had a higher density than PCL alone and the addition of ADC reduced the density of the materials. The incorporation of starch increased the water absorption and ADC did not significantly alter this property. The incorporation of starch into PCL reduced the tensile strength and the elongation at break; ADC enhanced these reductions and also decreased the Young's modulus of PCL. SEM showed that blends prepared with starch were immiscible, had a homogeneous dispersion of starch, and poor interfacial adhesion. The addition of ADC resulted in cells in the interior of the polymers. The 50/50 PCL/starch blends biodegraded faster than PCL, and ADC had no significant influence on the biodegradation of the blends but inhibited the biodegradation of PCL.
Journal of Applied Polymer Science, 1999
In the present article a series of low-density polyethylene (LDPE) blends with different amounts of fatty esters of amylose and starch, were prepared in a Haake-Buchler Reomixer. The tensile as well as the dynamic thermomechanical (DMTA) properties of the blends were measured. It was found that as the amount of the esters increases in the blends, the tensile strength and especially the elongation at break decrease nonlinearly. Scanning electron microscopy (SEM) was used to assess the interfacial adhesion between LDPE and the corresponding esters. The incompatibility of the blends was also verified with DMTA and differential scanning calorimetry (DSC). From the biodegradation studies of the blends during exposure in activated sludge, it was found that all esters are biodegradable, although to a much lesser degree compared to pure strach. The biodegradation rate of the composites is relatively small due to the low biodegradation rate of the pure esters.
Carbohydrate Polymers, 2011
A series of starch acetates (SAs) with different degrees of substitution (DS) were prepared by chemically converting the hydroxyl group of natural cornstarch (NS) into an acetyl group. Biodegradable poly (propylene carbonate) (PPC) was melt blended with these SAs in a Haake mixer. The morphologies, mechanical and thermal properties of PPC/SA and PPC/NS blends were investigated. PPC/SA (DS < 0.88) showed better tensile property and impact strength than those of PPC/NS. Scanning electron microscopy (SEM) and Fourier transform infrared spectra (FTIR) revealed strong interfacial adhesion between the SA fillers and PPC matrix. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) demonstrated the addition of SA led to improved thermal stability of the blend. Among all the samples prepared, the PPC/SA (DS = 0.51) has the optimal mechanical and thermal properties. The methodology described here represents a promising approach for the production of cost competitive biodegradable polymer blends.
LDPE/starch blends compatibilized with PE-g-MA copolymers
Journal of Applied Polymer Science, 1998
In the present study, low-density polyethylene (LDPE) and plasticized starch (PLST) blends, containing different percentages of PLST, were prepared. In these blends, two different polyethylene/maleic anhydride graft (PE-g-MA) copolymers containing 0.4 and 0.8 mol % anhydride groups, respectively, were added as compatibilizers at 10 wt % PLST. The compatibilization reaction was followed by FTIR spectroscopy. The morphology of the blends was studied using scanning electron microscopy (SEM). It was found that as the amount of anhydride groups in the copolymers increases a finer dispersion of PLST in the LDPE matrix is achieved. This is reflected in the mechanical properties of the blends and especially in the tensile strength. The blends compatibilized with the PE-g-MA copolymer containing 0.8 mol % anhydride groups have a higher tensile strength, which in all blends, even in those containing 20 and 30 wt % PLST, is similar to that of pure LDPE. The biodegradation of the blends followed the exposure to activated sludge. It was found that the compatibilized blends have only a slightly lower biodegradation rate compared to the uncompatibilized blends.
EFFECTS OF STARCH BLEND ON THE MECHANICAL PROPERTIES AND BIODEGRADABILITY OF POLYPROPYLENE
The effect of corn and cassava starch blends on the mechanical properties and biodegradability of polypropylene was studied using the gravimetric (weight loss) method. The results showed that tensile strength of the polymer decreased progressively from 2.497 Mpa of pure polymer to 0.250 Mpa for corn starch (90 % weight loss) and 0.500 Mpa for cassava starch (80 % weight loss) each at 50 % starch addition. At the same rate, elongation at break also decreased from 1.087 % of pure polymer to 0.10 % for corn starch (91 % weight loss) and 0.15 % for cassava starch (86 % weight loss). The biodegradability of a 10 % starch filled polymer composite within 30 days incubation was enhanced by more than 70 % in the presence of the microorganism and it increased with incubation period.