Synthesis and characterization of new polybenzoxazines from renewable resources for bio‐composite applications

Renewable natural resources such as eugenol, furfurylamine, stearylamine, and jute fiber were used to prepare polybenzoxazine composites. The purity of eugenol which is extracted from clove was confirmed by gas chromatography. FTIR, ¹H, and ¹³C NMR spectroscopic analysis were used to determine the structure of eugenol and the benzoxazine monomers namely 6‐allyl‐3‐furfuryl‐8‐methoxy‐3,4‐dihydro‐2H‐1,3‐benzoxazine (EF‐Bz) and 6‐allyl‐3‐octadecyl‐8‐methoxy‐3,4 dihydro‐2H‐1,3‐benzoxazine (ES‐Bz) synthesized from it. The curing analysis from differential scanning calorimetric analysis shows that the onset of curing is shifted to lower temperature (161°C) for EF‐Bz, when compared with ES‐Bz (174°C). The thermal stability analyzed from thermogravimetric analysis shows that the polybenzoxazine EF‐Pbz has higher thermal stability (T_5% = 361°C) with that of ES‐Pbz (T_5% = 313°C). The storage modulus, tensile, and flexural strength of the EF‐Bz/Jute fiber composite show high value when compared with ES‐Bz/Jute fiber composites. POLYM. COMPOS., 37:1821–1829, 2016. © 2014 Society of Plastics Engineers     

Difurfuryl diisocyanates: New adhesives derived from renewable resources

The syntheses of difurfuryl diisocyanates [e.g., ethylidenebis (2,5-furandiylmethylene) diisocyanate (EDFI)] have been reported in the literature. Difurfuryl diisocyanates are structurally similar to diphenylmethane diisocyanate (MDI), which has proven to be an excellent adhesive for bonding wood composites. The MDI regin is synthesized from petroleum-derived chemicals; the EDFI resin is synthesized from biomass-derived chemicals. In this study, the mechanical properties of aspen flakeboards bonded with MDI and EDFI are compared. In general, results show that the strength properties of flakeboards bonded with MDI are only marginally better than those bonded with EDFI. Because EDFI is more viscous than is MDI less than optimum atomization of the EDFI resin during spraying of the flakes is believed to be largely responsible for the differences in strength property values. The dry internal bond strength values of flakeboards bonded with MDI (1.33 MPa; 193 lb/in.²) at 3% resin content are significantly greater than the 0.41 MPa (60 lb/in.²) required by the American National Standards Institute (ANSI/A208.1) for type-2 medium-density particleboard. © 1993 John Wiley & Sons, Inc.

1 This article is a US Government work and, as such, is in the public domain in the United States of America.

     

Hybrid composite based on poly(vinyl alcohol) and fillers from renewable resources

Hybrid composite laminates consisting of polyvinyl alcohol (PVA) as continuous phase (33% by weight) and lignocellulosic fillers, derived from sugarcane bagasse, apple and orange waste (22% by weight) were molded in a carver press in the presence of water and glycerol such as platicizers agents. Corn starch was introduced as a biodegradation promoter and gluing component of the natural filler and synthetic polymeric matrix in the composite (22% by weight). The prepared laminates were characterized for their mechanical properties and degradative behavior in simulated soil burial experiments. The fibers type and content in composite impacted mechanical properties. Materials based on PVA and starch with apple wastes and sugarcane bagasse fillers were much harder (Young's Modulus respectively, 57, 171 MPa) than materials prepared with orange wastes (17 Mpa). Respirometric test revealed that soil microbes preferentially used natural polymers and low molecular weight additive as a carbon source compared to biodegradable synthetic polymer. The presence of PVA in formulations had no negative effect on the degradation of lignocellulosic fibers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Novel coatings from renewable resources for the protection of bronzes

End-capped poly(lactic acid)s with a benzotriazole moiety were synthesized by Ring Opening Polymerization of lactide, characterized by spectroscopic methods and tested as protective coatings on selected bronze surfaces. Performances of functionalized polymers were evaluated in terms of colour changes of the treated metal and stability of the coating. A comparison between end-capped polymers and a mixture of poly(lactic acid) and benzotriazole was also run. End-capped poly(lactic acid)s showed excellent stability to photochemical and thermo-hygrometric ageing and better performances than a blend of poly(lactic acid) and benzotriazole. These polymers show promising performances for metal's coating.     

Biodegradable binders and cross-linking agents from renewable resources

Conclusions  Recently, epoxidised vegetable oils have found industrial application as cross-linking agents in environment-friendly solvent-free powder coatings. A variety of vegetable oil-based epoxidised cross-linking agents is available by both chemical and enzymatic routes with high chemical purities. Furthermore, it was shown that functionalised vegetable oils can serve as building blocks for the preparation of biodegradable hydrophobic plastics poly-hydroxy alkanoates (PHAs) exhibiting good drying properties. The mechanical and physical performance of these binders (flexibility, adhesion, drying etc.) can be monitored easily by a proper choice of the vegetable oils used to prepare coatings for different substrates.     

Polyesters from renewable resources: Preparation and characterization

Polyesters were synthesized with monoglycerides prepared from rubber seed oil, a renewable resource. Monoglycerides were obtained by an alcoholysis method from the oil, which was neat or modified by treatments with different amounts of maleic anhydride at 230°C. The polyester resins were subsequently prepared by the condensation polymerization of the monoglycerides with phthalic anhydride. The monoglycerides and resins were characterized by spectroscopic analysis and measurements of the physicochemical properties. The chemical resistance of the polyesters was also studied. The results revealed that the polyesters prepared from the modified monoglycerides possessed better properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3748–3755, 2006     

Highly processible maleimide and nitrile functionalized benzoxazines for advanced composites applications

Maleimide and 2‐aminobenzonitrile (MIan)‐based benzoxazine has been synthesized and characterized. MIan contains imide, oxazine, and nitrile functional groups that can react almost simultaneously, leading to complicated reaction mechanisms. For understanding the fundamental polymerization mechanism, the model benzoxazine compound is synthesized. The ortho‐nitrile group in the model compound undergoes cyclization reaction, producing the thermally stable six‐membered ring species resulting in the excellent thermal properties of the material. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

From monomers to polymers from renewable resources: Recent advances

Considering the state of affairs related to polymers and their applications, the plastic-dependence of the modern society is evident and becomes now needless to mention. Together with that, the exhaustive discussion about the quick depletion of petroleum resources and the obvious alternative that lies on the great versatility of renewable feedstocks, it is clear that the most recent efforts should be – and are – directed to design more sustainable polymers to replace the classic ones. This review aims to offer a panoramic overview of the recent progress, but mainly of the broad possibilities that are still available in the hands of researchers working on this topic.     

绿色可再生能源之生物质能源

介绍了生物质能转化技术,综述了目前国内外生物质能源的利用现状、存在问题及其发展趋势,进一步指出生物质能的开发利用,对于我国能源结构调整、能源安全以及环境保护具有十分重要的意义.     

Thermoresponsive hydrogels based on renewable resources

This work aims to synthesize novel thermoresponsive hydrogels from renewable resources, bacterial cellulose (BC), and castor oil (CO), and to investigate the effect of CO on physical and thermal behaviors of BC/Poly(N-isopropylacrylamide) (PNIPAM) hydrogels. The structural properties of the hydrogels are analyzed by Fourier-transform infrared (FTIR) spectroscopy. Differential scanning calorimeter (DSC) technique and thermogravimetric analysis (TGA) are also performed to examine the thermal properties of the hydrogels. The morphological differences of the hydrogels are analyzed by scanning electron microscope (SEM). The thermoresponsive performances of the hydrogels are examined by swelling and deswelling behaviors. The hydrogel with CO is found to be more sensitive to temperature changes than the one without CO. Deswelling study demonstrates 91 and 25% of water loss for hydrogels with and without CO, respectively. The present study shows a novel approach to synthesize thermoresponsive hydrogels with renewable resources for biomedical applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48861.     

Modification of melamine‐formaldehyde resins by substances from renewable resources

In the present contribution, investigations on the chemical modification of thermosetting melamine formaldehyde resins by natural polyol compounds are presented. As representative agents soluble starch, sucrose, and glycerol were chosen to cover three different classes of polyols. The major aim was to use substances produced from natural bio‐renewable feedstock that are available in large quantities and may serve as environmentally innocuous and bio‐renewable substitutes for petro‐chemically derived and potentially hazardous materials. Different reaction conditions lead to resins with varying technical performance. For soluble starch no reaction conditions could be found that allow the adoption of this substitute for the laminate industry due to insufficient technological performance. Sucrose and glycerol on the other hand yielded impregnation resins with suitable performance. Chemical linkage of the modifying agent into the chain propagation by poly‐condensation however, was only found with glycerol. The covalent incorporation of glycerol in the network was observed with addition of glycerol at different stages during synthesis. The technological performance of the various modified thermosetting resins was assessed by determining flow viscosity, molar mass distribution, the storage stability, and in a second step laminating impregnated paper to particle boards and testing the resulting surfaces according to standardized quality tests. Spectroscopic evidence of chemical incorporation of glycerol was found by applying by ¹H, ¹³C, ¹H/¹³C HSQC, ¹H/¹³C HMBC, and ¹H DOSY methods. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Fabrication and characterization of eggshell powder particles fused wheat protein isolate green composite for packaging applications

Ample biodegradable eggshell powder (ESP)/wheat protein isolate (WPI) composite films were made by solution casting method of altering the WPI solution and fused with ESP particles in the percentage of 5, 10, 20, 30, and 40% (w/w) and asses the properties, i.e., physical, mechanical, and thermal as a function of ESP concentration. Determine the unification of ESP particles into the WPI matrix by X‐ray diffraction, fluorescence spectra, and SEM analysis. The data clearly showed the successful incorporation of ESP particles and good compatibility with the WPI and also mechanical properties and thermal stability of composite film increasing with the increasing ratio of ESP. Microstructural evaluation confirmed the aggregation and distribution of ESP particles within the WPI matrix and validated the results of functional properties of the WPI/ESP film. The results confirmed that the composite films have potential applications in the field of food and medicinal packaging especially for photosensitive medicines in a very simple and cheap way. POLYM. COMPOS., 37:3280–3287, 2016. © 2015 Society of Plastics Engineers     

Polymers from renewable resources. XII. Structure property relation in polyamideimides from rosin

Polyamideimides were synthesized from rosin maleic anhydride adduct either by reacting the acid chloride of the latter with different diamines or by self-polycondensation of rosin imido amino acid in the presence of thionyl chloride. The rosin imido amino acids were prepared by condensing rosin-maleic anhydride adduct with diamines. The presence of lithium chloride was found to have pronounced effect on yield and molecular weight of the polymers. The polyamideimides were characterized by infrared, elemental analysis, and viscosity measurements. The polymers were either amorphous or poorly crystalline in nature and soluble only in highly polar solvents. The thermal stability of the polymers has been studied. Some generalizations about structure-property relation in polyamideimides were made.     

Oleochemical esters — environmentally compatible raw materials for oils and lubricants from renewable resources

Due to the increasing market relevance of environmentally labelled products, the ecological properties of oleochemical esters have been intensively studied within the last couple of years. In general, their aquatic toxicity is very low or almost negligible, and they are readily biodegradable in most cases. They have not to be labelled as “dangerous for the environment” according to the EU Dangerous Substance Directive. Their origin from renewable resources results in lower net CO₂-emissions (“global warming”) compared to petrochemical products. Not many lubricants have such rather positive ecological profiles. Thus, most of them are classified in the most favourable water hazard class, i.e. in WGK 0. In addition, they fulfill the requirements of several European environmental labels, e.g. “Blauer Engel”. These favourable ecological properties together with their well established technical performance recommend the oleochemical esters as suitable base oils for the development of high performance “green” oil and lubricant products.     

Main-chain benzoxazine oligomers: A new approach for resin transfer moldable neat benzoxazines for high performance applications

A new approach has been developed to enhance the processability of main-chain benzoxazine polymers by synthesizing benzoxazine main-chain oligomers that are low in viscosity while maintaining the major part of the advantages of main-chain type polybenzoxazines. A series of main-chain benzoxazine oligomers have been synthesized using bisphenol-F isomers. The structure of the oligomers has been characterized by nuclear magnetic resonance spectroscopy (NMR) and Fourier transform infrared spectroscopy (FT-IR). The molecular weight has been evaluated using size exclusion chromatography (SEC). For a viscosity study, a mixture of benzoxazine monomers derived from the same bisphenol-F isomers has been used as control and a reactive diluent to control the viscosity.     

环氧树脂/棕榈酰氯改性玉米秸秆复合材料力学性能研究

以棕榈酰氯改性的玉米秸秆作为填料,将环氧树脂（EP）作为基体树脂,制备环氧树脂/改性玉米秸秆生物质复合材料。利用红外光谱和X射线光电子能谱对改性前后的秸秆进行结构表征,采用电子万能试验机对复合材料进行力学性能分析,利用扫描电子显微镜对复合材料的微观形貌进行分析。结果表明,红外谱图中在1 754 cm^-1处有新的C=O特征伸缩振动峰出现;X射线光电子能谱图中C1（C=C、C—C）、C2（C—O）含量分别从47.85 %和40.24 %下降到41.30 %和30.64 %,C3（C=O）、C4（C—O—C）含量分别从9.12 %和2.79 %增加到20.56 %和7.20 %,说明改性后玉米秸秆疏水性增强,与EP的相容性得到改善;随着玉米秸秆含量的增加,EP复合材料的拉伸性能与纯EP比增加了100.3 %和157.77 %;弯曲强度呈现出先增加后下降的趋势;未改性秸秆添加量达到10 %时,冲击强度最大比纯EP提高了16.8 %,而改性后秸秆的含量达到15 %时,比纯EP提高了70.53 %。     

Synthesis,characterization, and properties of isocyanate-free urethane coatings from renewable resources

Isocyanate-free urethane coatings were prepared from renewable resources through the aminolysis reaction of five-membered cyclic carbonate from linseed oil and phenalkamine from cashew nut shell liquid. The five-membered cyclic carbonate functional reactants were synthesized from epoxidized linseed oil through carbon dioxide insertion. The porous-free urethane coatings were prepared on aluminum substrates using synthesized carbonated linseed oil and phenalkamine at three different mixing ratios (1:0.5, 1:0.75, and 1:1.25) and at three different cure temperatures (60, 80, and 100°C). The formation of urethane linkages and the rate of cyclic carbonate conversion during the aminolysis reaction were characterized using FTIR spectroscopy. The thermal behavior of the cured urethane films was characterized using thermogravimetry. The effects of amine concentration and cure temperature on the optical, mechanical, and end-use properties of the coatings were evaluated by measuring specular gloss, solvent resistance, crosshatch, solvent swelling, and impact strength. The increase in cure temperature was directly proportional to the rate of aminolyis reaction and also to the coating performances.     

Preparation and properties of starch thermoplastics modified with waterborne polyurethane from renewable resources

A waterborne polyurethane (PU) aqueous dispersion was synthesized from castor oil, and blended with thermoplastic starch (TPS) to obtain a novel biodegradable plastic with improved physical properties. The effect of PU content on the morphology, miscibility and physical properties of the resulting blends was well investigated by scanning electron microscopy, differential scanning calorimetry, dynamic mechanical thermal analysis and measurements of mechanical properties and water sensitivity. The research results show that the blends exhibit a higher miscibility when PU content is lower than 15 wt% due to the hydrogen bonding interaction between urethane groups and hydroxyl groups on starch, whereas obviously phase separation occurs in the blends with more than 15 wt% PU. Incorporating PU of 4-20 wt% in TPS results in the blends with improved Young's modulus (40-75 MPa), tensile strength (3.4-5.1 MPa), elongation at break (116-176%). Further, PU also plays an important role in improving the surface- and bulk-hydrophobicity and water resistance of the resulting blends.