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1.
Graft copolymers of starch and polyacrylamide (PAAm) were prepared using reactive extrusion in a corotating twin screw extruder.
The effect of cationic starch modification was examined using unmodified and cationic dent starch (≈23% amylose) and waxy
maize starch (≈2% amylose). For a fixed acrylamide/starch feed ratio, conversion, graft content, and grafting efficiency were
essentially unaffected by starch type or modification. Cationic starch graft copolymers generally had lower molecular weight
PAAm grafts compared to the unmodified starch, whereas amylose content had little or no significant effect. In addition, the
frequency of grafting was higher with cationic starch. These results indicate that cationic modification of starch enhances
formation of grafting sites, resulting in graft copolymers with more grafts of lower molecular compared to unmodified starch.
Cationic modification may therefore be a way to tailor the properties of starch–PAAm graft copolymers. 相似文献
2.
LDPE has been mixed with LDPE-g-mA (LDPE grafted with (0.5%) maleic anhydride) in 1:1 ratio containing a polar group in the LDPE backbone. Blown film samples
containing various percentages of Potato Starch 0, 2.5, 5.0, 7.5, 10.0, 12.5 and 15% and LDPE grafted with maleic anhydride/LDPE
(1:1), have been prepared using extrusion film blowing under temperature profile ranging from 120 to 160 °C. Characteristics
of prepared packaging films up to 15% Potato Starch were analysed for their mechanical properties (Tensile strength, Elongation
at break, Bursting strength and Tear strength), water absorption properties and morphology. The compatibility of the system
with the introduction of 50% LDPE grafted with maleic anhydride with various ratios of starch, have been verified with the
help of resulting datasets. The resulting datasets were placed in theoretical models of Willet modifies Kerner’s equation and Nicolais and Narkis models. Procedure adopted above could make thermally stable, highly flexible, crystalline resultant material, which can be adopted
as an alternative of LDPE material especially for packaging applications. 相似文献
3.
This paper reports the effect of glycerol on thermal, mechanical and morphology of the wheat-flour based thermoplastic sheets (<3 mm) fabricated using single screw extrusion followed by compression molding. The amount of glycerol (plasticizer) added during the formulation varies from 20 to 35 % w/w (20, 23, 25, 30 and 35 % w/w). Results indicate that increase in the amount of glycerol in the starch based thermoplastic sheets, lowers its hardness and tensile properties while an increase in the melt flow index. Variation in the glycerol content from 20 to 25 % w/w increases the impact strength of the thermoplastic sheets beyond this limit it decreases. The contact angle analysis shows that glycerol has effect on the surface energy and work of adhesion of the thermoplastic sheets. However, the presence of glycerol has no significant influence on the thermal stability of thermoplastic sheets above 200 °C. 相似文献
4.
There is a paradigm shift from non renewal resources to renewable resources in view of problems of disposal of plastic products
after their life cycle. This paper deals with the approach, preparation and product properties of polymer prepared by using
polysaccharide based biodegradable polymer. Basic material has been prepared by mixing LDPE, LDPE-g-mA (LDPE grafted with
(0.5%) maleic anhydride (1:1)) containing a polar group in the LDPE backbone. Prepared basic material has been compounded
in twin screw extruder with 0, 2.5, 5.0, 7.5, 10.0, 12.5 & 15% of Potato Starch. Thereafter, after conditioning blown film
samples were prepared using extrusion film blowing technique, under temperature profile ranging from 120 to 160 °C. Packaging
films have been prepared with maximum 15% potato starch contents and have been characterized by FTIR, DSC, TGA, and XRD techniques
to ascertain its impact on some structural and thermal properties like thermal stability, flexibility, crystallinity, crystal
size etc. 相似文献
5.
The use of native starch as a thermoplastic polymer is limited by its fragility and high water absorption. Due to the presence of several hydroxyl groups in its structure, water acts as a natural plasticizer of starch, modifying its properties. It is necessary to chemically modify starch molecules by replacing hydroxyl groups with other functional groups to reduce water absorption. Chemical modification of starch granules also alters its swelling and gelatinization behavior. In this contribution we describe the chemical modification of starch and its influence on its hydrophilicity and heat resistance. Acetic acid, maleic anhydride and octanoyl chloride were used as derivatizing reagents. The effectiveness of the treatments was evaluated by means of infrared spectroscopy. Different tests were conducted in order to evaluate the influence of the different chemical modifications on starch structure and properties. Results showed that the treatments effectively reduced starch moisture susceptibility, while substantially altering other properties such as amylose content, swelling power, solubility, and heat resistance. Finally, films were prepared from native and derivatized starch and their surface polarity was evaluated. 相似文献
6.
Shouhai Li Chunpeng Wang Xiaowei Zhuang Yong Hu Fuxiang Chu 《Journal of Polymers and the Environment》2011,19(1):301-311
Renewable resource-based composites were prepared with acorn powder and Thermoplastic resin poly(lactic acid) (PLA) by twin-screw
extrusion followed by injection molding processing or hot-compression molding processing. The study of the composites microstructure
showed poor adhesion between acorn powder and PLA matrix. The hygroscopicity, mechanical properties and melt flow property
of composites were promising even though the composites had a 70 wt% content of acorn powder. Silane coupling agent, 4,4′-Methylenebis
(phenyl isocyanate) and PLA grafted with maleic anhydride did not show obvious effect on mechanical properties of composites.
The impact resistance strength of reinforced composites with steel fiber webs were improved greatly in comparison with those
having no steel fiber webs. Thermal properties results of DSC and DMA showed that the presence of acorn powder significantly
affected the crystallinity, crystallization temperature (Tc), glass transition temperature (Tg) and melting temperature (Tm) of PLA matrix. The study results proved that composites had superior mechanical properties, enough to partially replace
the conventional thermoplastic plastics. 相似文献
7.
Arturo U. Rodriguez Subrata B. Ghosh Robert Jeng Mohini M. Sain 《Journal of Polymers and the Environment》2010,18(3):430-436
Starches modified by Ophiostoma spp. have been investigated to develop bio-materials with enhanced mechanical and physical properties for thermoplastic applications.
In this study, glass transition temperature (Tg) of modified starches was investigated in both dynamic mechanical analyzer (DMA) and differential scanning calorimeter (DSC)
to detect molecular changes in the starch’s structure. Overall, two thermal transitions were observed in modified starches,
as opposed to one in their native counterparts. Scanning electron microscopy of granular modified starch indicated visible
damages and internal structural perturbations in addition to occlusion of granular pores by extraneous materials owing to
possible enzymatic degradation and production of secondary metabolites. Modified starches registered two-fold improvement
in storage modulus as compared to that of native starches. From the study of second derivative of the mass loss against temperature,
two thermal transitions were also identified in modified starches. X-ray diffraction analyses showed that crystalline regions
of the starch granules remained intact after the modification. It is proposed that the second phase transition potentially
corresponds to modified amylose fractions and/or exopolysaccharides produced by the fungi. 相似文献
8.
Maryam Sabetzadeh Rouhollah Bagheri Mahmood Masoomi 《Journal of Polymers and the Environment》2018,26(6):2219-2226
In this work, morphology, rheological and tensile properties of low-density polyethylene/linear low-density polyethylene/thermoplastic oxidized starch (LDPE/LLDPE/TPOS) blends are studied. The blends of LDPE/LLDPE (70/30, w/w) containing 0–20 wt% TPOS in the presence of 3 wt% of PE-grafted maleic anhydride (PE-g-MA) as a compatibilizer are prepared by a twin screw extruder and then converted to appropriate thin films using an extrusion film blowing machine. Scanning electron microscopic images show that there is a relative good dispersion of oxidized starch particles in PE matrices. However, as TPOS content in the blends increases, the starch particle size increases too. The rheological analyses indicate that TPOS can decrease the elasticity and viscosity of the blends. The LDPE/LLDPE/TPOS blends show power-law behavior and as the TPOS content increases the power-law exponent (n) and consistency index (K) decrease. The ultimate tensile strength and elongation at break of the final blend films reduce, when TPOS content increases from 5 to 20 wt%. However, the required mechanical properties for packaging applications are achieved when 10 wt% oxidized starch is added, according to ASTM D4635. 相似文献
9.
Foam extrusion of biodegradable polyester [poly(butylene adipate-co-terephthalate) (PBAT)] and its blends with maleated thermoplastic
starch (MTPS) using a chemical blowing agent was performed. The effect of MTPS and percentage of chemical blowing agent on
various foam properties is discussed. In general, an increased amount of PBAT in the foams improves the properties of the
foams. The foam samples were characterized by measurements of density, expansion ratio, specific length, compressive strength,
resiliency, moisture sorption, and imaging using digital light microscopy. Density, expansion ratio, and specific length measurements
show that the best characteristics of lowest density, highest expansion ratio, and highest specific length are exhibited by
the PBAT samples. The compressive strength and foam density exhibit a power-law relationship. Greater amounts of PBAT in the
samples increase the resiliency and decrease the steady state weight gain during moisture sorption. All samples show regions
of unfoamed material when only 3% chemical blowing agent is used, but when 5 and 7% chemical blowing agent is used, the samples
exhibit cells throughout the matrix. 相似文献
10.
The aim of this study was to evaluate the suitability of in vitro enzymatic methods for assaying the biodegradability of new starch-based biopolymers. The materials studied included commercial starch-based materials and thermoplastic starch films prepared by extrusion from glycerol and native potato starch, native barley starch, or crosslinked amylomaize starch. Enzymatic hydrolysis was performed using excessBacillus licheniformis -amylase andAspergillus niger glucoamylase at 37°C and 80°C. The degree of degradation was determined by measuring the dissolved carbohydrates and the weight loss of the samples. Biodegradation was also determined by incubating the samples in a compost environment and measuring the weight loss after composting. The results indicated that the enzymatic method is a rapid means of obtaining preliminary information about the biodegradability of starch-based materials. Other methods are needed to investigate more accurately the extent of biodegradability, especially in the case of complex materials in which starch is blended with other polymers. 相似文献
11.
Effect of Orientation on the Morphology and Mechanical Properties of PLA/Starch Composite Filaments 总被引:1,自引:0,他引:1
Randal L. Shogren Gordon Selling J. L. Willett 《Journal of Polymers and the Environment》2011,19(2):329-334
Polylactic acid (PLA)/starch fibers were produced by twin screw extrusion of PLA with granular or gelatinized starch/glycerol
followed by drawing through a set of winders with an intermediate oven. At 30% starch, fibers drawn 2–5x were highly flexible
(elongation 20–100%) while undrawn filaments were brittle (elongation 2–9%). Tensile strength and moduli increased with increasing
draw ratio but decreased with increasing starch content. Mechanical properties were better for composites made with gelatinized
starch/glycerol than granular starch. In conclusion, orientation greatly increases the flexibility of PLA/starch composites
and this may be useful not only in fibers but also possibly in molded articles. Other advantages of starch addition could
include fiber softness without added plasticizer, moisture/odor absorbency and as a carrier for active compounds. 相似文献
12.
Penggang Ren Tingting Shen Fang Wang Xing Wang Zhengwei Zhang 《Journal of Polymers and the Environment》2009,17(3):203-207
The thermoplastic starch (TPS) and nanocomposite(TPS/OMMT) was prepared with 15% carbamide, 15% ethanolamine and different
contents of organic activated montmorillonite (OMMT) by twin-screw extruder with a 130 °C barrel temperature. Fourier transforms
infrared spectroscopy and wide angle X-ray diffraction shown that the alkylamine in dodecyl benzyl dimethyl ammonium bromide
could react with MMT via cation exchange reaction. After treated, the d(001)space distance of MMT increased from 1.5 to 1.7 nm. Scanning electron microscope revealed that the lower contents of
OMMT could disperse well in the matrixes of TPS. The carbamide, ethanolamine and the OMMT could destroy the crystallization
behavior of starch, but only the OMMT restrained this behavior for long-term storing. Mechanical properties investigation
indicated that the tensile strength and modulus of TPS/OMMT nanocomposites were better than those of TPS, while the elongation
at break was descended with the increasing of OMMT contents. When the content of OMMT was 4%, the tensile strength and modulus
of TPS was improved from 4.2 and 42 MPa to 6.0 and 76 MPa, respectively. 相似文献
13.
Application of Cellulose Microfibrils in Polymer Nanocomposites 总被引:1,自引:0,他引:1
Cellulose microfibrils obtained by the acid hydrolysis of cellulose fibers were added at low concentrations (2–10% w/w) to polymer gels and films as reinforcing agents. Significant changes in mechanical properties, especially maximum load and tensile strength, were obtained for fibrils derived from several cellulosic sources, including cotton, softwood, and bacterial cellulose. For extruded starch plastics, the addition of cotton-derived microfibrils at 10.3% (w/w) concentration increased Young’s modulus by 5-fold relative to a control sample with no cellulose reinforcement. Preliminary data suggests that shear alignment significantly improves tensile strength. Addition of microfibrils does not always change mechanical properties in a predictable direction. Whereas tensile strength and modulus were shown to increase during addition of microfibrils to an extruded starch thermoplastic and a cast latex film, these parameters decreased when microfibrils were added to a starch–pectin blend, implying that complex interactions are involved in the application of these reinforcing agents. 相似文献
14.
Loose-fill packaging sponges were extruded from mixtures of 54–62% hydroxypropylated (HP 5%) amylomaize V (50% amylose) and wheat starches, 17–24% synthetic polymer, 13% water, 7% blowing agent(s), and 0.5% nucleating agent. One product made from 28% HP wheat starch, 28% HP amylomaize V starch, 12% ethylene vinyl alcohol (EVOH) copolymer, 8% polystyrene (PS), and 3% polystyrene maleic anhydride (PSMA) copolymer, plus the other raw materials, had a compressibility and resilience that matched those of expanded polystyrene (EPS), although its bulk density was four times higher. The starchy sponge showed 16% shrinkage in volume at 90% relative humidity and was 2% soluble in excess water, both at 25°C. After aging for 18 months near 25°C, the HP starchy sponge gave only a trace of fines in a simulated shipping test, compared to 20% fines from a biodegradable, starch-based, loose-fill sponge of commerce. 相似文献
15.
Wei Zou Xingxun Liu Long Yu Dongling Qiao Ling Chen Hongsheng Liu Nuozi Zhang 《Journal of Polymers and the Environment》2013,21(2):359-365
The effects of starch structures, in particular amylose content, on grafting reactions were investigated using thermal gravimetric analysis (TGA), nuclear magnetic resonance, X-ray diffraction (XRD). As a model system, corn starches with different amylose contents (0, 26, 50 and 80 %) were grafted onto acrylamide to produce superabsorbent polymers (SAPs). The weight loss measured by TGA at different temperature was used to analyze the grafting ratio in quantity. In general, the grafting ratio increased (about 10 %) with increasing starch amylose content, and graft chain segment lengths were much lower for the amylopectin-rich (waxy) starch. The high molecular weight and branched structure of the amylopectin reduced the mobility of the polymer chains and increased viscosity, which resulted in resistance to chain growth. The water absorption capability was increased with increasing amylose content for the starch-based SAPs. XRD detection showed that the crystalline structure of all starches was destroyed after grafting reactions. The thermal stability of the polyacrylamide grafted onto the starches increased by about 10 °C, which could be explained by the strong bonding between the grafted polymer chains and the starch matrices. 相似文献
16.
Shouhai Li Chunpeng Wang Fuxiang Chu Jianling Xia Yuzhi Xu 《Journal of Polymers and the Environment》2013,21(4):1072-1082
Two dissimilar renewable resource-based thermoplastic acorn nutlet (TPAN) materials were prepared via twin-screw extrusion with the aid of glycerol or monoethanolamine as plasticizers, and then two TPAN/polycaprolactone (PCL) composites with different plasticized systems were prepared. Mechanical test showed that glycerol-based composites had excellent tensile properties, and at a PCL content of 50 wt%, their tensile strength and elongation at break reached 14.4 MPa and 1,361 %, respectively. The micro-morphologic investigation of liquid-nitrogen brittle fracture surface indicated certain interface adhesion between glycerol-based thermoplastic acorn nutlet (GTPAN) and PCL. Dynamic mechanical thermal analysis , differential scanning calorimetry and thermogravimetric analysis demonstrated that the weight ratios of TPAN in composites significantly affected the crystallinity, glass transition temperature (Tg), melting temperature (Tm) and thermal stability of composites. Soil burial degradation analysis displayed that all composites had excellent biodegradability. These results demonstrated that GTPAN/PCL composites had superior mechanical and biodegradable properties, enough to partially replace the conventional thermoplastic plastics. 相似文献
17.
The Effect of Starch Composition on Structure of Foams Prepared by Microwave Treatment 总被引:2,自引:0,他引:2
A microwave technique was used to prepare foams from different potato starches in granular form, with varying amounts of amylose content, and water. In addition to native potato starch (PN), high amylose potato starch (HAP) and potato amylopectin (PAP) were used, as well as mixtures thereof. In all cases the native crystallinity of starch granules was lost upon microwave treatment and an amorphous material was created. An increased concentration of starch in the initial water dispersion resulted in a less dense foam structure. The potato amylopectin formed open cell foams, whereas increased amylose content, as in native potato starch, yielded a more compact structure with irregular pore shapes. The high amylose potato starch yielded a structure with hardly any porosity. Foaming experiments were done to compare pre-gelatinized and granular starches dispersed in water. The pre-gelatinisation did not affect the pore formation process. These experiments indicated that the molecular architecture of starch polymers is more important for foam formation than starch polymer organization in the granules. Studies of temperature profile and dry matter content during microwave treatment showed that water evaporates more rapidly from a high amylose starch solution than native potato starch and potato amylopectin solutions. Rheological measurements showed that the amylose solution had much lower viscosity than starch and amylopectin. This confirms that polymer – water interaction, such as in amylopectin solution, favours stabilization of bubbles formed upon boiling and evaporation of water, which yields high porosity materials. 相似文献
18.
Ivan S. Ristić Ljiljana Tanasić Ljubiša B. Nikolić Suzana M. Cakić Olivera Z. Ilić Radmila Ž. Radičević Jaroslava K. Budinski-Simendić 《Journal of Polymers and the Environment》2011,19(2):419-430
Different synthesis methods were applied to determine optimal conditions for polymerization of (3S)-cis-3,6-dimethyl-1,4-dioxane-2,5-dione (l-lactide), in order to obtain poly(l-lactide) (PLLA). Bulk polymerizations (in vacuum sealed vessel, high pressure reactor and in microwave field) were performed
with tin(II) 2-ethylhexanoate as the initiator. Synthesis in the vacuum sealed vessel was carried out at the temperature of
150 °C. To reduce the reaction time second polymerization process was carried out in the high pressure reactor at 100 °C and
at the pressure of 138 kPa. The third type of rapid synthesis was done in the microwave reactor at 100 °C, using frequency
of 2.45 GHz and power of 150 W at the temperature of 100 °C. The temperature in this method was controlled via infrared system
for in-bulk measuring. The solution polymerization (with trifluoromethanesulfonic acid as initiator) was possible even at
the temperature of 40 °C, yielding PLLA with narrow molecular weight distribution in a very short period of time (less than
6 h). The obtained polymers had the number-average molecular weights ranging from 43,000 to 178,000 g mol−1 (polydispersity index ranging from 1 to 3) according to the gel permeation chromatography measurements. The polymer structure
was characterized by Fourier transform infrared and NMR spectroscopy. Thermal properties of the obtained polymers were investigated
using thermogravimetry and differential scanning calorimetry. 相似文献
19.
Preparation and Characterization of Compatible and Degradable Thermoplastic Starch/Polyethylene Film 总被引:2,自引:0,他引:2
The degradability of the compatible thermoplastic starch/polyethylene film was investigated by weight loss percent (WLP),
Fourier Transform Infrared (FT-IR) Spectroscopy, and Scanning Electron Microscope (SEM). The compatible film was prepared
by using the particles of thermoplastic starch/polyethylene blends that were produced by one-step reactive extrusion. The
weight of the film after degradation reduced more than 3% for 30 days and 4% for 60 days. The FTIR results revealed that both
starch and polyethylene in the film exhibited varying degrees of degradation. SEM photographs of the films after degradation
showed that starch particles in the film disintegrated into smaller particles or separated out of the film surface. Degradation
studies demonstrated that the compatible thermoplastic starch/polyethylene film had increased degradability at the given degradable
environment. The information implies that this film could be utilized as a degradable plastic. 相似文献
20.
S. Devereux P. S. Shuttleworth D. J. Macquarrie F. Paradisi 《Journal of Polymers and the Environment》2011,19(4):971-979
The wastewater generated at a facility specialising in potato processing was found to contain high levels of insoluble potato
starch. Several separation methods were employed to obtain maximum potato starch recovery from the industrial wastewater.
Centrifugation was proved to be the most effective means of separation. Following potato starch recovery, a variety of chemical
and physico-chemical properties were investigated. Potato starch quality and consistency were assessed and monitored across
a 1 year period, between 2007 and 2008. Based on the various starch characteristics that were obtained, it was established
that the recovered potato starch was of a high quality and is therefore suitable for subsequent processing, without the need
of performing any pre-treatment. Properties including total starch, damaged starch, protein, lipid and amylose content, as
well as gelatinisation and retrogradation, were evaluated and a high level of consistency throughout the course of 1 year
was recorded. 相似文献