Effect of Groundnut Shell Powder on the Mechanical Properties of Recycled Polyethylene and Its Biodegradability

Natural fiber reinforced composites have gained considerable attention particularly in the manufacturing industry owing to their light weight, corrosion resistance, abundance, and biodegradability. In this work, alkaline treated and untreated groundnut shell powder (GSP) was used to reinforce recycled polyethylene to produce GSP-recycled polyethylene composites with improved mechanical properties and biodegradability. GSP with particle sizes of 0 - 300 μm and 300 - 600 μm was used in different proportions: 5%, 10%, 15%, 20%, 25%, and 30% wt. The fiber was immersed for 5 hours in a 10 wt% NaOH solution. Tensile and hardness test data showed an improvement in mechanical properties of the treated fiber composites. Results of water absorption test also showed that treated GSP-recycled polyethylene composites had a lower rate of water absorption than the untreated GSP-recycled polyethylene composites. Through Fourier transform infrared spectroscopy, disappearance of characteristics peaks of hemicellulose and lignin was observed. Growth of fungi on the fiber-reinforced composites was observed, which was evidence that GSP-recycled polyethylene composite was biodegradable. Finally, SEM micrographs showed uniform distribution of treated fibers in the polymer matrix;this explained the observed improvement in the mechanical properties of treated GSP-recycled polyethylene composites.

Optimization of Extrusion Process Parameters of Recycled High-Density Polyethylene-Thermoplastic Starch Composite for Fused Filament Fabrication

High-density poly-ethylene (HDPE) is a nonbiodegradable recyclable plastic which is widely utilized in single use packaging applications. Consequently, it constitutes a significant amount of plastic waste found in landfills. From literature, it has been shown that parts produced using composites of HDPE with carbohydrate-based polymers, such as thermoplastic starch (TPS), experience mechanical degradation through hydrolytic degradation process. The possible utilization of recycled-HDPE (rHDPE) and TPS composite in nonconventional manufacturing processes such as Fused filament fabrication (FFF) has however not been explored. This study explores the potential application of rHDPE and TPS composites in FFF and optimizes the extrusion process parameters used in rHDPE-TPS filament production process. Taguchi method was utilized to analyze the extrusion process. The extrusion process parameters studied were the spooling speed, extrusion speed and the extrusion temperatures. The response variable studied was the filament diameter. In this research, the maximum TPS content achieved during filament production was 40 wt%. This filament was however challenging to use in FFF printers due to frequent nozzle clogging. Printing was therefore done with filaments that contained 0 - 30 wt% TPS. The experimental results showed that the most significant parameter in extrusion process was the spooling speed, followed by extrusion speed. Extrusion temperature had the least significant influence on the filament diameter. It was observed that increase in TPS content resulted in reduced warping and increased rate of hydrolytic degradation. Mechanical properties of printed parts were investigated and the results showed that increasing TPS content resulted in reduction in tensile strength, reduction in compression strength and increase in stiffness. The findings of this research provide valuable insights to plastic recycling industries and researchers regarding the utilization of recycled HDPE and TPS composites as substitute materials in FFF.

STUDIES ON GRAFT COPOLYMERIZATION OF DL-LACTIDE ON CORN STARCH AND BIODEGRADABILITY OF THE COPOLYMERS

The starch/D,L-lactide graft copolymers were synthesized by reacting D,L-lactide with corn starch in N,N-dimethylacetamide (DMAM) in the presence of triethylamine (NEt3) and anhydrous lithium chloride. The effect of reaction time and the molar ratio of D,L-lactide to glucose structural unit of starch on monomer conversion(C%), graft (G%) and graft efficiency (GE%) were studied. The C%, G% and GE% could approach 37.3%,179.7% and 68.0%, respectively when the molar ratio of D,L-lactide to glucose structural unit of starch is 10:1 and the graft copolymerization was carried out at 80-85℃ for 4 hours under nitrogen atmosphere. The Fourier transforms infra-red (FTIR) spectroscopy, differential scanning calorimetry (DSC) and X-ray diffraction (XRD) spectroscopy were used in order to characterize the graft copolymers. FTIR spectra show that absorption band at 1740 cm-1 confirmed the formation of ester bond, indicating the starch /D,L-lactide graft copolymers were produced, the DSC characteristic results show the melting temperature of the graft copolymer were elevated slightly as the molar ratio of D,L-lactide to glucose structural units of starch increased and the X-ray diffraction spectra show the synthesized graft copolymers were amorphous. The degradability of graft copolymer was tested with the aid of acid, alkali and microbe such as bacillus subtilis and staphylococcus aureus. The results of water resistance show the graft copolymer produced can be used as a component of impermeable coating for cardboard.

A Starch-Based Biodegradable Polyethylene for Municipal Solid Waste Mitigation

This work reports a method for reducing the longevity of the polymer content of Municipal Solid Wastes (MSW) in the environment. In this approach biodegradability was imparted on polyethylene, a popular, low-cost commodity polymer, using starch additives. Corn starch and cassava starch in varying proportions were compounded with suitably prepared polyethylene powder and compression-moulded in steel dies. Alongside tensile test, biodegradability tests were carried out by burying samples for 28 days in two different soil types with different pH, fungi and bacteria load. Cassava starch additions were found to be better at imparting biodegradability. Also, alkaline soil types with higher bacteria load seemed a more favourable environment for accomplishing biodegradation in the starch-polyethylene composites.

Extrusion of Thermoplastic Starch: Effect of “Green” and Common Polyethylene on the Hydrophobicity Characteristics

Novel plastics that are biodegradable, environmentally benign, and made from renewable natural resources are currently being researched as alternatives to traditional petroleum-based plastics. One such plastic, thermoplastic starch (TPS) is produced from starch processed at high temperatures in the presence of plasticizers, such as water and glycerol. However, because of its hydrophilic nature, TPS exhibits poor mechanical properties when exposed to environmental conditions, such as rain or humidity. The overall objective of this research work was to produce a thermoplastic starch based material with low water absorption that may be used to replace petroleum-based plastics. With a recent emergence of “green” polyethylene (GPE), sourced from renewable feedstock, it has become possible to develop novel biodegradable polymers for various applications. In this work, GPE was melt blended with starch in three different ways;reactive extrusion of GPE and starch facilitated by maleic anhydride (MAH) and dicumyl peroxide (DCP), melt blending of GPE and starch by extrusion, and melt blending of maleated polyethylene and starch by extrusion. Comprehensive testing and analysis has shown that all methods reduced water absorption significantly with some variations across the board.

PROPERTIES OF BIODEGRADABLE THERMOPLASTIC STARCH

Thermoplastic starch is a kind of modified starch produced by mixing starch with additives and processing the mixture in an extruder. The mechanical properties, including tensile strength and elongation at break, biodegradability and rheological properties were studied. Glycerol and urea, to some extent, can both decrease the tensile strength and increase percentage elongation at break, because the former acts as a plasticizer and the latter can break down interactions among starch macromolecules. Thermoplastic starch shows thermoplasticity and its melt behaves as a pseudoplastic liquid at a low shear rate. Its biodegrading extent is slightly higher than that of native starch. The molecular weight of starch displays a decreasing tendency after thermoplastic modification.

Effect of TiO2 Nanoparticles on Biodegradability of Polystyrene/Starch Blends

A study of biodegradation behavior of Polystyrene/Starch/TiO2 nanocomposites based on evaluating the weight loss of the tested films after water immersion, a-amylase enzymatic solution immersion and soil burial and the tensile properties of the tested fdms. Blend films and the nanocomposites were prepared by hand layup methodwith different weight percentage ratios of TiO2 nanoparticles. The results show that the weight loss of the tested films due towater immersion, enzymatic solution immersion and soil burial decreased with the increasing of TiO2 nanoparticles content but the mechanical properties were enhanced by the addition of TiO2 nanoparticles.

Progress in Researches on Biodegradable Starch-Based Materials

As one type of environment-friendly polymer, biodegradable starch-based materials have been widely explored in recent years and considered one of the most promising plastics in the future. Currently, either synthetic biodegradable aliphatic polyesters or certain natural polymers are usually blended with thermoplastic starch to enhance hydrophobicity and service performance of starch-based materials. The main deficiency lies in the low compatibility between starch and polyester phases. Therefore amphiphilic compatibilizers, such as hydroxyl functioned polyesters, need to be developed in the future. Moreover, multi-phase blending systems including two or more polyester phases are also supposed to be designed.

Utilization of Starch to Accelerate the Growth of Degrading Microorganisms on the Surface of Natural Rubber Latex Films

NRL （natural rubber latex） films with 0 （control） and 10 phr sago starch loading were buried in compost soil for 4 weeks. The biodegradation assessments were carried out through films WVT （water vapor transmission） and mass loss. Scanning electron microscopy was carried out to identify and monitor the properties of rubber degrading organism colonies. Results showed that incorporation of sago starch increased the formation and rates of propagation for microorganism colonies on NRL films with duration of biodegradation. The results also indicate the mechanism of sago starch granules utilization as sole source of energy for microbial growth. The behavior and characteristics of microorganisms involved in NRL films degradation also successfully discussed.

Study on Structure and Performance of Starch and Styrene Graft Copolymer

[Objective] The paper was to study the structure and performance of starch and styrene graft copolymer. [Method] The microscopic structure of corn starch and styrene graft copolymer was analyzed by using infrared spectrum and scanning electron microscope, and the property of starch and styrene graft copoly- mer was confirmed through grinding experiment, tensile strength, water absorption rate, hot water resistance properties and enzymatic properties analysis. [Result] The starch and styrene graft copolymer had the properties of thermoplastic and microbial degradation. IConclusion] The starch and styrene graft copolymer is expected to be developed as a biodegradable material.

Study on the Properties of Esterified Corn Starch/Polylactide Biodegradable Blends

Fully bio-based and biodegradable starch/polylactic acid blends have received increasing attentions for their biodegradability and potential to offset the use of unsustainable fossil resources,specifically,their application in packaging.Herein,corn starch was first esterified with maleic anhydride and then compounded with polylactide(PLA)to prepare esterified corn starch/polylactic acid blends with starch content up to 35 wt%.The structures,morphologies,thermal and mechanical properties of starch or blends were investigated.The results showed that corn starch was successfully grafted with maleic anhydride,which showed increased crystallinity and particle size than native starch.Esterified corn starch/polylactic acid blends showed good surficial compatibility and good thermal stability with main decomposition temperature in the range of 300℃to 400℃.Additionally,incorporation of corn starch increased the hydrophilicity and water uptake of composites.However,the tensile and flexural strengths of blends decreased with increasing esterified starch amount.

State of Knowledge on Starch as an Alternative Solution to Petrochemical Resources—A Review

The use of plastics from petrochemical resources poses environmental impacts, and one of the alternative solutions is the use of starch. The objective of this present work has been to present the literature on starch, and to highlight the debate in the development of composite films. The approach adopted was to present the state of the art on starch and thermoplastic starch matrix composites. The work shows that starch is available worldwide and can be used in the manufacture of biodegradable plastics;the debate remains on the reinforcement of thermoplastic starch to improve its physical and mechanical properties poor;then researchers must diversify the reinforcements to see the impact on the properties of thermoplastic starch.

Biodegradation and Mechanical Property of Polylactic Acid/Thermoplastic Starch Blends with Poly (ethylene glycol)

The effects of adding poly （ethylene glycol） （PEG） into polylactic acid/thermoplastic starch blends （PLA/TPS） on the properties were investigated by DSC, SEM and mechanical property-testing. The blends of PLA/TPS blended with increasing content PEG exhibited lower temperature of glass transition （T） and lower temperature of melting （T） as well as higher melt flow index （MFI）, which indicates the plasticization and proeessability of the composites were dramatically improved. The tensile strength, flexural strength and izod impact strength of PLA/TPS （80/20） increased at first and then decreased with increasing content of PEG due to stronger interfacial adhesion. The optimized mechanical property can be obtained for the blend with 3 wt % PEG. The samples containing PEG after soil burial for 5 months showed quicker degradation being accompanied with large weight loss and mechanical properties loss.

Studies on Mechanical Properties of Full-Biodegradable Starch-PVA-Polyester Films

A kind of full biodegradable film material is discussed in this article. The film material is composed of starch, PVA, degradable polyesters(PHB, PHB V, PCL) with built plasticizer, a cross linking reinforcing agent and a wet strengthening agent. It contains a high percentage of starch, costs cheap and is excellent in weather fastness, temperature resistance and waterproof and it could be completely biodegraded. The present paper deals mainly with a new technical route using a new type of electromagnetic dynamic blow molding extruder and some effects on mechanical properties of the system.

Influence of Phase Behavior and Miscibility on Mechanical, Thermal and Micro-Structure of Soluble Starch-Gelatin Thermoplastic Biodegradable Blend Films

Polymer blends of cold water soluble starches (amylose or amylopectin soluble starch) with gelatin were prepared using solvent casting method. The solid state miscibility and polymer-polymer interactions between the constituent polymers were studied by fourier transforms infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorirmetry (DSC), light optical microscopy (OP) and scanning electron microscopy (SEM), whereas the thermal stability of the blends was studied by thermogravimetric analysis (TGA). Furthermore, tensile and water vapor barrier properties of the blends were assessed. The obtained results exhibited that gelatin was more miscible with amylose soluble starch than with amylopectin soluble starch. Moreover, enhancing mechanical and water barrier properties of amylose soluble starch/gelatin blends were more pronounced than those of amylopectin soluble starch/gelatin blends. Generally, tensile strength (TS) and Elongation percentage (E) of the blend films were found to be gradually increased with increasing the proportion of gelatin. Nevertheless, increasing starch proportion was in favor of decreasing water vapor permeability (WVP). At equal proportions of starch and gelatin (1:1), TS was raised up to 8.69 MPa for amylose soluble starch/gelatin blend films while it raised up to 4.96 MPa for amylopectin soluble starch/gelatin blend films, and so on E was increased to its maximum by ~179.6% for soluble amylose starch/gelatin blends while it was increased to ~114.5% for amylopectin soluble starch/gelatin blends. On the other hand, WVP was significantly decreased to be 6.46 and 12.09 g·mm/m2·day·kPa for blends of amylose and amylopectin soluble?starches, respectively.

Biodegradation Behavior of Starch in Simulated White Water System of Old Corrugated Cardboard Pulping Process

Considering the serious barriers/issues induced by the accumulated starch generated in white water system of old corrugated cardboard(OCC)pulping process,large amounts of accumulated starch in white water would be decomposed by microorganisms and could not be utilized,thereby resulting in severe resource wastage and environmental pollution.This study mainly explored the effects of biodegradation/hydrolysis conditions of the two types of starch substrates(native starch and enzymatically(α-amylase)hydrolyzed starch),which were treated via microorganism degradation within the simulated white water from OCC pulping system and their biodegradation products on the key properties were characterized via X-ray diffraction(XRD),Fourier-transform infrared spectroscopy(FT-IR),and gel permeation chromatography(GPC)technologies.The effects of system temperature,pH value,starch concentration,and biodegradation time on starch biodegradation ratio and the characteristics of obtained biodegradated products from the two types of starches were studied.In addition,the effect ofα-amylase dosage on the biodegradation ratio of enzymatically hydrolyzed starch and its properties was investigated.It was found that the native starch presented a maximal degradation ratio at a system temperature of 55℃and pH value range of 5-7,respectively,the corresponding starch concentration within simulated white water system was 200 mg/L.Whereas the enzymatically hydrolyzed starch exhibited a highest degradation ratio at a system temperature of 50℃and pH value of 5.5,respectively,and the corresponding starch concentration within simulated white water system was 100 mg/L.It was verified that native starch is more readily bio-hydrolyzed and biodegradation-susceptive by microorganisms in simulated white water system of OCC pulping process,while the enzymatically hydrolyzed starch exhibits better biodegradation/hydrolysis resistance to the microbial degradation than that of native starch.This study provides a practical and interesting approach to investigate the starch hydrolysis or biodegradation behaviors in white water system of OCC pulping process,which would greatly contribute to the full recycling and valorized application of starch as a versatile additive during paperboard production.