Erratum

Abstract

Southern pine and aspen flakes were acetylated with acetic anhydride alone without cosolvent or catalyst by a simple dip procedure. The new procedure greatly shortens reaction time and simplifies chemical recovery. Acetylation weight gains of 15% to 20% can be achieved in 1 to 3 hours with southern pine flakes and in 2 to 4 hours with aspen flakes.

Flakeboards made from acetylated southern pine or aspen flakes absorbed much less water, both in water-soaking tests and when subjected to humid air, and swelled at a lower rate and to a lower extent than did control boards.

Hygroscopicity of the resulting flakeboards decreased with increased level of wood acetylation. The equilibrium moisture content (EMC) for flakeboards made from acetylated flakes was lower at each relative humidity tested than that of control boards.     

Vapor Phase Acetylation of Southern Pine,Douglas-Fir,and Aspen Wood Flakes

Abstract

Southern pine, Douglas-fir, and aspen wood flakes were acetylated with acetic anhydride vapor and compared with flakes acetylated with liquid acetic anhydride diluted with xylene. The rate of acetylation was much lower for the vapor than for the liquid phase reaction. Acetylation weight percent gains above 20 were achieved by both methods. Flakeboards made from both types of flakes absorbed much less water, both in water soaking tests and when subjected to humid air, and swelled at a lower rate and to a lower extent than did control boards. At low weight gains of vapor phase acetylation, the rate and extent of swelling were higher than those found for the controls.

Hygroscopicity of the resulting flakeboards decreased with increased level of wood acetylation. The equilibrium moisture content for flakeboards made from liquid phase acetylated flakes was the lowest at each relative humidity tested as compared to control boards, and boards made from vapor acetylated flakes at the same weight gain.     

ACETYLATED PLANT-FIBER-REINFORCED POLYESTER COMPOSITES: A STUDY OF MECHANICAL,HYGROTHERMAL, AND AGING CHARACTERISTICS

The potential of acetylation of plant fibers to improve the properties of composites was studied. The chemical modification of oil palm empty fruit bunch (EFB), coconut fiber (Coir), oil palm frond (OPF), jute, and flax using noncatalyzed acetic anhydride were investigated. Proof of acetylation was indicated by the increase in weight percent gain (WPG). Acetylation at a reaction temperature of 120°C had resulted in the reduction in the tensile properties (stress, modulus, and elongation at break) of EFB and Coir composites. However, at 100°C, the acetylated samples exhibited improved properties. The mechanical properties of acetylated EFB- and Coir-fiber-reinforced polyester composites was evaluated at different fiber loadings. The tensile strength and modulus were improved, but elongation at break was slightly reduced upon acetylation, particularly at high fiber loading. Impact properties were moderately increased for those composites with fiber loadings up to 45%. Acetylation exhibited a low moisture absorption, comparable with glass-fiber composites. Acetylated EFB and Coir composites showed superior retention of tensile and impact properties after aging in water up to 12 months.     

Effect of oxidation level on the dual modification of banana starch: The mechanical and barrier properties of its films

Banana starch was oxidized at three different levels and then acetylated. The double‐modified starch was used for film preparation. The physical, mechanical, and barrier properties were tested. The oxidation level increased the whiteness of the film, and the second modification (acetylation) did not affect this parameter. The solubility increased with temperature and oxidation level. However, acetylation decreased the solubility value. At the longest storage times, the solubility decreased because of starch reorganization inside the polymeric matrix. In general, oxidation increased the tensile strength of the films, and a slight increase was observed when the oxidized starch was acetylated. This effect was more noticeable at the longest storage time. The oxidation level decreased the percentage elongation at break, and a slight effect due to acetylation was observed. The film of oxidized–acetylated starch showed a higher elastic modulus value than its oxidized counterpart. The water vapor permeability increased with oxidation level, but the acetylation decreased this parameter. The oxidation increased the hydrophilic character of the starch because of the formation of carbonyl and carboxyl groups that showed more affinity for water molecules. When the oxidized banana starch was acetylated, a decrease in the water vapor permeability was found because the acetylation increased the hydrophobic character of the starch due to the ester group. Films prepared with the double‐modified banana starch had some improved physical, mechanical, and barrier properties, and they may be used in specific applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Influence of the oxidation and acetylation of banana starch on the mechanical and water barrier properties of modified starch and modified starch/chitosan blend films

Banana starch was oxidized at three different levels and afterwards acetylated. The double‐modified starch was used for film preparation with the addition of chitosan. The physical, mechanical, and barrier properties were tested. The oxidation level increased the moisture content of the film, but the acetylation and the addition of chitosan decreased this characteristic. The oxidation level increased the whiteness of the film, but the second modification (acetylation) and the addition of chitosan to the blend did not affect this parameter. The solubility increased with the temperature and the oxidation level but decreased with the storage time of the film. The oxidation increased and the acetylation reduced the solubility with respect to the native starch film. The dual modification produced a solubility value less than that of its oxidized counterpart, and the addition of chitosan produced the highest solubility value. The addition of chitosan increased the tensile strength of the film, and the effect was higher with the oxidation level and longest storage time. The addition of chitosan produced a higher elongation value than that of its double‐modified film, but at the longest storage time, this parameter decreased. The water vapor permeability increased with the oxidation level because of the hydrophilic character, but the acetylation reduced this parameter because the acetylation increased the hydrophobic character of the starch due to the ester group. Films prepared with the double‐modified banana starch and the addition of chitosan had some improved physical, mechanical, and barrier properties, and they may be used in specific applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Influence of nanoclay on properties of HDPE/wood composites

Composites based on high density polyethylene (HDPE), pine flour, and organic clay were made by melt compounding and then injection molding. The influence of clay on crystallization behavior, mechanical properties, water absorption, and thermal stability of HDPE/pine composites was investigated. The HDPE/pine composites containing exfoliated clay were made by a two‐step melt compounding procedure with the aid of a maleated polyethylene (MAPE). The use of 2% clay decreased the crystallization temperature (T_c), crystallization rate, and the crystallinity level of the HDPE/pine composites, but did not change the crystalline thickness. When 2% MAPE was added, the crystallization rate increased, but the crystallinity level was further lowered. The flexural and tensile strength of HDPE/pine composites increased about 20 and 24%, respectively, with addition of 1% clay, but then decreased slightly as the clay content increased to 3%. The tensile modulus and tensile elongation were also increased with the addition of 1% clay. The impact strength was lowered about 7% by 1% clay, but did not decrease further as more clay was added. The MAPE improved the state of dispersion in the composites. Moisture content and thickness swelling of the HDPE/pine composites was reduced by the clay, but the clay did not improve the composite thermal stability. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Enhancing the reactivity and strength of cotton fibers

Both sodium hydroxide solution of mercerizing strength and anhydrous methylamine are suitable pretreatments for enhancing the reactivity of cotton cellulose. Favorable results are achieved by maintaining the fiber material in the never-dried state after the swelling treatment. Extraction by organic solvents is to be preferred over water-washing in order to remove the swelling agent. When cotton is swollen with either aqueous sodium hydroxide or anhydrous methylamine and then washed and dried, its crystallinity, as determined by X-ray diffraction is not lowered as much as it is if it is acetylated to an acetyl content of about 9% before drying. The greatest modifications of the crystal structure of cotton were found on methylamine treatment followed by chloroform and pyridine washing and acetylation in the never-dried state (MeCP product), as well as by alcoholic mercerization followed by ethanol and pyridine washing and acetylation in the never-dried state (AMEP). As determined by moisture regains, no significant differences are apparent between the accessibility of samples of low acetyl content (ca. 9%) prepared by either the AMEP or by the MeCP treatment. The DTA curves of methylamine-treated cotton with an acetyl content close to that of commercial diacetate and the commercial product are dissimilar. It can be concluded from the DTA curve of the deacetylated product prepared from this MeCP sample that it has a highly disordered structure. The tensile properties of the acetylated products of low acetyl content are considerably improved if acetylation is preceded by mercerization with subsequent solvent exchange, and less so if it is preceded by methylamine followed by solvent exchange. Incorporation of acetyl groups significantly enhances the breaking strength and extensibility of mercerized solvent-washed materials.     

Preparation and characterization of polychloroprene nanocomposites with cellulose nanofibers from oil palm empty fruit bunches as a nanofiller

Cellulose nanofibers (CNFs) from oil palm empty fruit bunches were chemically modified by acetylation with acetic anhydride and pyridine (as the solvent and catalyst). The acetylated CNFs showed good dispersion in a polychloroprene (PCR) matrix. The tensile strength and modulus of neat PCR were improved, whereas its elongation at break decreased with increasing nanofiber content. Above the glass‐transition temperature (T_g), the dynamic mechanical analysis profiles showed that the storage modulus of the PCR–cellulose nanocomposites was higher than that of neat PCR. Meanwhile, the thermal stability was still maintained, and the T_g was close to the neat PCR at the 5 wt % addition level of CNFs. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40159.     

乙酰化淀粉/聚己内酯共混物的制备和性能研究

分别采用淀粉(TPS)、乙酰化淀粉(TPAS)与聚己内酯(PCL)进行熔融共混，制备了可生物降解的塑料，探讨了淀粉乙酰化改性后对共混物力学性能、耐水性、熔融流动性、相容性及生物降解性的影响。共混物的拉伸强度均随PCL用量的增加而增大，TPAS／PCL体系的拉伸强度低于TPS／PCL体系，而断裂伸长率高于TPS／PCL体系。PCL可以明显改善淀粉基材料的耐水性，淀粉乙酰化后共混体系的相容性及熔体流动性得到一定的改善，生物降解性略微下降。     

Behavior of polyolefin blends with acetylated sisal fibers

The influence of acetylation on the mechanical, thermal and thermodegradative behavior of sisal fiber‐reinforced PP, PP/HDPE and PP/HDPE with functionalized and non‐functionalized EPR composites was studied. Acetylation of the fiber improves adhesion of the fiber to the polyolefin matrix. In general, acetylation of the sisal fiber was found to enhance the tensile strength and modulus of the resulting composites, except in some cases. Thermal properties suggest that the mixing and molding temperatures are between 160 and 230 °C and that when acetylated fiber is mixed with polyolefins, greater polymer‐fiber interactions takes place, which slightly favor stability of these composite materials. The results allow us to suggest that a satisfactory profit/cost relation justifies the addition of acetylated fiber to PP, PP/HDPE, and PP/HDPE/EPR. © 2000 Society of Chemical Industry     

Potential of producing carbon fiber from biorefinery corn stover lignin with high ash content

The possibility of producing carbon fiber from an industrial corn stover lignin was investigated in the present study. As‐received, high‐ash containing lignin was subjected to methanol fractionation, acetylation, and thermal treatment prior to melt spinning and the changes in physiochemical and thermal properties were evaluated. Methanol fractionation removed most of the impurities in the raw lignin and also selectively removed the molecules with high melting points. However, neither methanol fractionation nor thermal treatment rendered melt‐spinnable precursors. The precursors were highly viscous and decomposed easily at low temperatures, attributed to the presence of H, G phenolic units, and abundant hydroxycinnamate groups in herbaceous lignin. A two‐step acetylation of methanol fractionated lignin greatly improved the mobility of lignin, while enhancing the thermal stability of the precursor during melt‐spinning. Fourier Transform Infrared and 2D‐NMR analysis showed that the contents of phenolic and aliphatic hydroxyls, as well as the hydroxycinnamates, decreased in the acetylated precursors. The optimum precursor was a partially acetylated lignin with a glass transition temperature of 85 °C. Upon oxidative stabilization and carbonization, the carbon fibers with an average tensile strength of 454 MPa and modulus of 62 GPa were obtained. The Raman spectroscopy showed the I_D/I_G ratio of the carbon fiber was 2.53. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45736.     

Simultaneous full‐interpenetrating polymer networks of blocked polyurethane and vinyl ester. II. Static and dynamic mechanical properties

Simultaneous full‐interpenetrating polymer networks (full‐IPNs) based on blocked polyurethane (PU) and vinyl ester (VE) have been prepared. The static and dynamic properties of these IPNs have been examined. Results show that the tensile strength and flexural strength of IPNs increased with blocked PU content to a maximum value at 7.5 wt % PU content and then decreased. The tensile modulus, flexural modulus, and hardness of IPNs decreased with increasing blocked PU content. The impact strength of IPNs increased with increasing blocked PU content. The tensile strength, flexural strength, tensile modulus, and flexural modulus of IPNs increased with filler (kaolin) content to a maximum value at 20 to 25 phr filler content and then decreased. The higher the filler content, the greater the hardness, and the lower the impact strength of IPNs. The tensile strength, flexural strength, tensile modulus, flexural modulus, and hardness of IPNs increased with increasing VE initiator content. The dynamic technique was used to determined the damping behavior across a temperature range. Results show that the glass transition temperature (T_g) of IPNs are shifted inwardly compared with pure PU and VE, which indicated that the blocked PU–VE IPNs showed excellent compatible. Meanwhile, the glass transition temperature was shifted to a higher temperature with increased filler content. The dynamic storage modulus (E′) of IPNs increased with increasing VE and filler content. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1977–1985, 1999     

Preparation and Characterization of Bioblends from Gelatin and Linear Low Density Polyethylene (LLDPE) by Extrusion Method

Abstract

Bioblends are composites of at least one biodegradable polymer with a non-biodegradable polymer. Successful development of bioblends requires that the biodegradable polymers be compatible with other component biodegradable/synthetic (non-biodegradable) polymers. Bioblends from LLDPE and gelatin were prepared by extrusion and hydraulic heat press technique. The gelatin content in the bioblends was varied from 5 to 20 wt%. Various physico-mechanical properties such as tensile, bending, impact strength (IS), thermal ageing and soil degradation properties of the LLDPE/gelatin bioblends with different gelatin contents were evaluated. The effect of thermal ageing on mechanical properties was studied. The mechanical properties such as tensile modulus (TM), bending strength (BS), bending modulus (BM) were found to increase with increasing gelatin content up to 20 wt%, however tensile strength (TS) and elongation at break (%E _b) were decreased with increasing gelatin content. Impact strength value increased with increasing gelatin content up to 10 wt% and then decreased slightly with increasing gelatin content. The blend containing 20 wt% gelatin showed relatively better mechanical properties than other blends. The values of TS, TM,%E _b, BS, BM and IS for the bioblend with 20 wt% gelatin content are 5.9MPa, 206.3MPa, 242.6%, 12.1MPa, 8 MPa and 13.7 J/cm², respectively. Water uptake increases with increasing soaking time in water and weight loss due to soil burial also increases with increasing gelatin content in the blends but both are significantly lower than that of pure gelatin sheet. Weight loss values after thermal ageing increase with time, temperature and increasing gelatin content in the blend but are much lower than pure gelatin. Mechanical properties such as TS, TM are increased and %E _b is decreased after thermal ageing at 60°C for 30 min. Consequently, among all of the bioblends prepared in this work the blend having 20% gelatin content yields properties such that it can be used as a semi-biodegradable material.     

Utilization of bowstring hemp fiber as a filler in natural rubber compounds

The cure characteristics and physicomechanical properties of natural rubber (standard Nigerian rubber) vulcanizates filled with the fiber of bowstring hemp (Sansevieria liberica) and carbon black were investigated. The results showed that the scorch and cure times decreased, whereas the maximum torques increased, with increasing filler loadings for both bowstring hemp fiber and carbon black filled vulcanizates. The tensile strength of both bowstring hemp fiber and carbon black filled vulcanizates increased to a maximum at a 40 phr filler concentration before decreasing. The elongation at break and rebound resilience decreased, whereas the modulus, specific gravity, abrasion resistance, and hardness increased, with increasing filler contents. The carbon black/natural rubber vulcanizates had higher tensile strength, which was about 1.5 times that of bowstring hemp fiber/natural rubber vulcanizates. This superiority in the tensile strength was probably due to the higher moisture content and larger particle size of the bowstring hemp fiber. However, the bowstring hemp fiber/natural rubber vulcanizates showed superior hardness. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effects of superheated steam treatment on moisture adsorption and mechanical properties of pre-dried rubberwood

Abstract

Rubberwood (Hevea brasiliensis) was treated with superheated steam (140–160?°C) for 1–3?h and then its adsorption ability, mechanical properties, and color changes were investigated. The results of adsorption show decreased equilibrium moisture content (EMC) for all heat-treated cases throughout the hygroscopic range. The Hailwood–Horrobin model was used to analyze the sorption isotherms and determine the monolayer and polylayer moisture contents for untreated and heat-treated rubberwood. The monolayer moisture content clearly decreased with treatment temperature and duration, whereas the reduction in polylayer moisture was relatively smaller. Moreover, the least density of water adsorption sites was found in wood after treatment at 160?°C for 3?h, indicating this as the cause for reduced equilibrium adsorption. All treatment conditions had improved mechanical properties, including compression parallel-to-grain, hardness, and tensile strength. The total color difference of the wood surface increased with increasing temperature and treatment duration.     

Factors influencing the tensile properties of ramie

Many investigators have claimed that tensile breakage of native cellulose fibers occurs primarily by repture of covalent bonds in the cellulose molecules rather than by chain slippage resulting from repture of such interchain bonds as hydrogen bonds. This claim has been made partly on the basis of a comparison of tensile properties of ramie fiber and of the fully esterified counterpart. This comparison indicated that the breaking load of ramie was similar to that of the fully esterified fiber. In studying the tensile properties of ramie fiber and of fully acetylated ramie fiber, we found that the degree of polymerization of the fiber was lowered during the acetylation process. Also, it was evident that both degree of polymerization and degree of crystallinity are important factors to be considered when comparing the tensile strength of native cellulose fibers and their acetylated counterparts. Although the primary cause of tensile breakage of native cellulose fibers may be due to chain scission rather than to chain slippage, it is difficult to claim supporting evidence for this theory from studies made so for on the tensile properties of esterified ramie fibers.     

Effect of surface acetylated‐chitin nanocrystals on structure and mechanical properties of poly(lactic acid)

In this work, the miscibility between chitin nanocrystals (ChNs) and poly(lactic acid) (PLA) was expected to be improved by surface acetylation of ChN. The reaction of acetic anhydride onto the ChN surface was confirmed by FTIR and ¹³C NMR, while XRD and TEM proved the crystalline structure and rod‐like morphology were maintained. The acetylated ChN (AChN) was incorporated into a PLA matrix by solution blending, and resulted in an increase of tensile strength and Young's modulus and they reached to the maximum value as 45 and 37% higher than neat PLA film, respectively, with the loading level of AChN reaching to 4 wt %. The enhancement could be attributed to that acetylation improved dispersion of AChN in the PLA matrix and interfacial adhesion between AChN and PLA. The performances of the nanocomposites based on PLA and chitin nanocrystals derived from renewable resources have good potential for industrial applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39809.     

Morphology and mechanical properties of PP/POE/nano‐CaCO3 composites

The mechanical properties including tensile, flexural, and impact of the nanometer on calcium carbonate (nano‐CaCO₃) filled polypropylene (PP)/poly (ethylene‐co‐octene) (POE) composites were measured at room temperature to identify the effects of the POE content on the mechanical properties. It was found that the Young's modulus, tensile strength, and tensile elongation at break decreased nonlinearly while the tensile fracture strength varied slightly with increasing the POE weight fraction; the V‐notched and unnotched Izod impact fracture strength increased nonlinearly with an increase of the POE weight fraction; the flexural modulus and strength decreased roughly linearly with increasing the POE weight fraction. Furthermore, the impact fracture surface of the specimens was observed by means of a scanning electronic microscope to discuss the toughening mechanisms. POLYM. COMPOS., 37:539–546, 2016. © 2014 Society of Plastics Engineers     

浆液体系中木薯淀粉乙酰化反应均匀性及基团分布特征

以木薯淀粉为原料、乙酸酐为酰化剂，在浆液体系中制备乙酰化淀粉，采用4.3 mol·L^-1 CaCl₂溶液对乙酰化淀粉颗粒进行化学表面糊化处理，获得不同表面糊化程度的剩余淀粉颗粒，通过SEM、XRD表征剩余颗粒的形貌及结晶结构，采用皂化法测定剩余颗粒的乙酰基含量，并利用最小二乘法拟合取代基含量在淀粉颗粒径向上的分布曲线，考察乙酰化反应均匀性和乙酰基分布的影响因素。结果发现：乙酰基团在淀粉颗粒中呈现外高内低的非均匀分布，30%以上的乙酰基分布在对比半径0.9~1.0的外部区域，而在0~0.7比较大的范围内仅占28%左右；反应温度升高、反应时间延长和酰化剂用量增大，乙酰基含量在淀粉颗粒内的分布离散程度减小，有利于乙酰化反应和乙酰基团分布更趋均匀；随着表面糊化程度增大，剩余颗粒均能保持木薯淀粉的形貌和“A”型结晶结构特征，但粒径稍有减小，结晶度整体呈现下降趋势，部分稍有突跃。以上结果说明，结晶结构与非晶结构在木薯淀粉颗粒内交替存在，且各区域结晶区和非晶区比例存在一定差异，适当改变反应条件可改善木薯淀粉颗粒内乙酰化反应和乙酰化基团非均匀分布的状况。     

Effect of acetylation and oxidation on some properties of breadfruit (Artocarpus altilis) seed starch

Starch extracted from seeds of Artocarpus altilis (Breadfruit) was chemically modified by acetylation and oxidation, and its functional properties were evaluated and compared with these of native starch. Analysis of the chemical composition showed that moisture content was higher for modified starches. Ash, protein, crude fiber and amylose contents were reduced by the modifications, but did not alter the native starch granules' irregularity, oval shape and smooth surface. Acetylation produced changes in water absorption, swelling power and soluble solids, these values were higher for acetylated starch, while values for native and oxidized starches were similar. Both modifications reduced pasting temperature; oxidation reduced maximum peak viscosity but it was increased by acetylation. Hot paste viscosity was reduced by both modifications, whereas cold paste viscosity was lower in the oxidized starch and higher in the acetylated starch. Breakdown was increased by acetylation and reduced with oxidation. Setback value was reduced after acetylation, indicating it could minimize retrogradation of the starch.