二氧化硅填料对环氧Vitrimer动态性能的影响

将SiO_(2)颗粒引入动态环氧类玻璃高分子(Vitrimer)网络中,制备了具有可控动态性能的环氧Vitrimer。结果表明:填料含量的增加对环氧Vitrimer的基础性能负面影响小,但环氧Vitrimer的特征弛豫时间(τ)、活化能(Ea)、Arrhenius指前因子(τ0)和拓扑冻结转变温度(Tv)等典型动力学参数都可以很容易地通过填料的含量来调整。SiO_(2)的引入使环氧Vitrimer性能可控,能够按需实现材料的再加工成型。

A sustainable process to 100%bio-based nylons integrated chemical and biological conversion of lignocellulose

Considerable progress has been made in recent years to the development of sustainable polymers from bio-based feedstocks.In this study,100%bio-based nylons were prepared via an integrated chemical and biological process from lignocellulose.These novel nylons were obtained by the melt polymerization of 3-propyladipic acid derived from lignin and 1,5-pentenediamine/1,4-butanediamine derived from carbohydrate sugar.Central to the concept is a three-step noble metal free catalytic chemical funnelling sequence(Raney Ni mediated reductive catalytic fractionation-reductive funnelling-oxidative funnelling),which allowed for obtaining a single component 3-propyladipic acid from lignin with high efficiency.The structural and thermodynamic properties of the obtained nylons have been systematically investigated,and thus obtained transparent bio-based nylons exhibited higher Mw(>32,000)and excellent thermal stability(Td5%>265℃).Considering their moderate Tg and good melt strength,these transparent bio-based nylons could serve as promising functional additives or temperature-responsive materials.

Aqueous-phase reforming of hydroxyacetone solution to bio-based H_(2)over supported Pt catalysts

Aqueous-phase reforming(APR)is an attractive process to produce bio-based hydrogen from waste biomass streams,during which the catalyst stability is often challenged due to the harsh reaction conditions.In this work,three Pt-based catalysts supported on C,AlO(OH),and ZrO_(2)were investigated for the APR of hydroxyacetone solution in afixed bed reactor at 225℃and 35 bar.Among them,the Pt/C catalyst showed the highest turnover frequency for H_(2)production(TOF of 8.9 molH_(2)molPt^(-1)min^(-1))and the longest catalyst stability.Over the AlO(OH)and ZrO_(2)supported Pt catalysts,the side reactions consuming H_(2),formation of coke,and Pt sintering result in a low H_(2)production and the fast catalyst deactivation.The proposed reaction pathways suggest that a promising APR catalyst should reform all oxygenates in the aqueous phase,minimize the hydrogenation of the oxygenates,maximize the WGS reaction,and inhibit the condensation and coking reactions for maximizing the hydrogen yield and a stable catalytic performance.

基于酯交换的生物基Vitrimer材料制备及性能

以异甘露糖醇(IMT)、六亚甲基二异氰酸酯(HDI)、1,4-丁二醇(BDO)、丙三醇(GI)为原料,设计合成了生物基Vitrimer材料IMT-COO。通过傅里叶变换红外光谱和X射线衍射对其结构进行了表征;通过热重分析、差示扫描量热分析、应力-应变曲线、动态力学热分析(DMA)探究了IMT-COO材料热稳定性、玻璃转变温度、力学性能及储能模量。结果表明,IMT-COO具有良好热稳定性及力学强度,热分解温度达256℃,应力为1.24 MPa、应变为140%。DMA结果表明,IMT-COO的储能模量最高达2671 MPa。IMT-COO的自愈合试验表明在自愈前后,各项性能无明显降低。

碳纤维增强Vitrimer环氧树脂复合材料层间修复与热塑成型行为

研究了新型碳纤维增强Vitrimer环氧树脂复合材料(V-CFRP)的层间修复性能和热塑成型工艺,并分析了热压修复与热塑成型机理。结果表明:新型Vitrimer环氧树脂的玻璃化转变温度(T_(g))为92.8℃,其高于T_(g)温度下表现出显著的应力松弛行为,应力松弛时间与温度呈现线性关系;采用三点弯曲实验研究了V-CFRP复合材料的热压修复行为与热塑成型能力,热压修复研究发现在180~220℃,5 MPa条件下热压1.5~2.0 h可实现复合材料层间破坏近乎100%的修复;热压成型研究表明,V-CFRP复合材料在180~220℃预加热5~30 min,其弯曲模量和弯曲强度下降超过80%,弯曲模量的大幅下降意味着V-CFRP适于热压再成型;并采用模塑热压方法,在200℃,5 MPa和2 h热压条件下,实现了V-CFRP板材热塑成型制备具有三维特征的结构件,证明了V-CFRP复合材料的热压模塑成型能力。

生物基Vitrimer高分子材料的研究进展

传统高分子材料分为热塑性材料和热固性材料,热塑性材料可二次加工但刚性不足,热固性材料虽刚性大但回收困难。类玻璃高分子(Vitrimer)材料则介于热塑性材料与热固性材料之间,是一种具有高交联密度网络、可进行二次加工的材料。根据Vitrimer的网络交换机理重点介绍了生物基类玻璃高分子的发展史和研究进展,对基于不同共价键的生物Vitrimer进行了详细介绍:动态酯交换反应的条件相对温和,反应速度快,反应原料广泛,但材料力学性能和可逆性较差;动态二硫键交换的可逆性与可控性更好,且反应对外界酸碱环境要求并不苛刻,然而反应底物一般具有毒性和刺激性气味;动态亚氨键交换可使得材料具有良好的机械性能和耐久性,生物相容性较好,但反应条件与原材料选择相对单一。综述了生物基Vitrimer材料的应用与优势,动态共价键的引入弥补了传统3D打印材料刚性不足和功能单一的缺点,增强了碳纤维复合材料的综合性能,提高了弹性体材料的使用寿命及自我修复效率。并对未来发展前景做出了展望。

Vitrimer材料的研究现状与展望

Vitrimer材料在高温下可进行再加工,通过可逆的交换反应进行材料内部网络拓扑结构的重排,释放材料内部应力,并且具有优于热塑性材料的力学性能、耐热性能、耐腐蚀性能等特点。主要介绍了Vitrimer材料的研究背景和特性;讨论和对比了以结合键类型为基础的分类反应机理;阐述了近几年Vitrimer材料的研究进展;以及对Vitrimer材料的应用前景作出展望,以期能够为Vitrimer材料的研究提供新的研究思路和研究方向。

Elastic Bio-based Polyurethane Nanofibrous Membrane with Robust Waterproof and Breathable Properties

Elastic bio-based waterproof and breathable membranes(EBWBMs) allow the passage of water vapor effectively and resist the penetration of liquid water,making it ideal for use under extreme conditions.In this study,we used a facile strategy to design the bio-based polyurethane(PU) nanofibrous membranes with the nanoscale porous structure to provide the membranes with high waterproof and breathable performances.The optimization of nanofibrous membrane formation was accomplished by controlling the relative ambient humidity to modulate the cooperating effects of charge dissipation and non-solvent-induced phase separation.The obtained EBWBMs showed multiple functional properties,with a hydrostatic pressure of 86.41 kPa and a water vapor transmission(WVT) rate of 10.1 kg·m^(-2)·d^(-1).After 1 000 cycles of stretching at 40% strain,the EBWBMs retained over 59% of the original maximum stress and exhibited an ideal elasticity recovery ratio of 85%.Besides,even after 80% deformation,the EBWBMs still maintained a hydrostatic pressure of 30.65 kPa and a WVT rate of 13.6 kg·m^(-2)·d^(-1),suggesting that bio-based PU nanofibrous membranes could be used for protection under extreme conditions.

聚烯烃Vitrimer材料的设计、合成和性能

当前,为了实现资源的可持续发展和对环境的保护,塑料橡胶制品的回收和再利用是工业界和科研领域十分关注的课题。Vitrimer材料能够在维持交联结构稳定的同时实现网络拓扑结构的重排,将灵活的共价交联网络属性、强健的力学和热力学性能与优异的重复加工性相统一,将分子水平重构及宏观水平重塑的能力结合起来,成为区别于常规热固性材料和热塑性材料的第三类新兴聚合物类型。这种新兴的Vitrimer材料的设计为传统的塑料橡胶制品的回收和再利用开辟了一条新的途径。本文综述了基于工业上广泛应用的聚烯烃材料转化为Vitrimer材料的设计方法,详细介绍了广泛应用的动态β-羟基酯键交换(有机网络酯交换和纳米界面酯交换)和动态B-O键交换(硼酸酯和二醇或酯基的动态酯交换反应、硼酸酯复分解反应和环硼氧烷复分解反应)的动态交换机理及其在设计聚烯烃基Vitrimer材料上的应用,最后对聚烯烃基Vitrimer材料存在的问题进行了分析并对未来研究发展方向进行了展望。

Eco-friendly physical blowing agent mass loss of bio-based polyurethane rigid foam materials

Through systematical experiment design, the physical blowing agent(PBA) mass loss of bio-based polyurethane rigid foam(PURF)in the foaming process was measured and calculated in this study, and different eco-friendly PBA mass losses were measured quantitatively for the first time. The core of the proposed method is to add water to replace the difference, and this method has a high fault tolerance rate for different foaming forms of foams. The method was proved to be stable and reliable through the standard deviations σ1and σ2for R1(ratio of the PBA mass loss to the material total mass except the PBA) and R2(ratio of the PBA mass loss to the PBA mass in the material total mass) in parallel experiments. It can be used to measure and calculate the actual PBA mass loss in the foaming process of both bio-based and petroleumbased PURF. The results show that the PBA mass loss in PURF with different PBA systems is controlled by its initial mass content of PBA in PU materials ω. The main way for PBA to dissipate into the air is evaporation/escape along the upper surface of foam. This study further reveals the mechanism of PBA mass loss: the evaporation/escape of PBA along the upper surface of foam is a typical diffusion behavior. Its spread power comes from the difference between the chemical potential of PBA in the interface layer and that in the outside air. For a certain PURF system, R1has approximately linear relationship with the initial mass content of PBA in PU materials ω, which can be expressed by the functional relationship R1= kω, where k is a variable related to PBA’s own attributes.

CO_(2)-Responsive Smart Foams Stabilized by an Extremely Rigid Bio-Based Surfactant

Environment friendly and intelligent surfactants have attracted great attention in recent years.A bio-based CO_(2)responsive surfactant rosin acid dimaleimide choline(R-BMI-C)with an extremely rigid skeleton was prepared using rosin and choline as raw materials by Diels-Alder addition reaction and acid-base neutralization reactions.Its structure was confirmed by IR and^(1)H NMR spectra.The foams’properties of R-BMI-C could be adjusted by bubbling CO_(2)/N_(2)to change the structure of the surfactant.At pH 10.4,R-BMI-C forms an unstable foam with a half-life of 1.5 h.When the pH was reduced to 7.4 by bubbling CO_(2),R-BMI-C forms an extremely stable foam with a half-life of 336 h.The surfactant R-BMI-C changed from bola type to conventional type when bubbling CO_(2).And the internal aggregation structure of R-BMI-C aqueous solution changed from spherical micelles to laminar micelles according to the cryogenic-transmission electron microscope.We know that the lamellar structure tends to adsorb at the air/water interface or is trapped in the foam film,which slows down the foam coarsening and agglomeration process,resulting in a significant increase in foam stability.R-BMI-C could be used in oil extraction,fire-fighting and chemical decontamination due to its excellent foaming,stabilization and defoaming properties.

Fully Bio-Based Composites of Poly(Lactic Acid)Reinforced with Cellulose-Graft-Poly-(ε-Caprolactone)Copolymers

Due to the increasing demand for modified polylactide(PLA)meeting“double green”criteria,the research on sustainable plasticizers for PLA has attracted broad attentions.This study reported an open-ring polymerization method to fabricate cellulose(MCC)-g-PCL(poly(ε-caprolactone))copolymers with a fully sustainable and biodegradable component.MCC-g-PCL copolymers were synthesized,characterized,and used as green plasticizers for the PLA toughening.The results indicated that the MCC-g-PCL derivatives play an important role in the compatibility,crystallization,and toughening of the PLA/MCC-g-PCL composites.The mechanical properties of the fully bio-based PLA/MCC-g-PCL composites were optimized by adding 15 wt%MCC-g-PCL,that is,the elongation at break was 22.6%(~376%higher than that of neat PLA),the tensile strength was 47.3 MPa(comparable to that of neat PLA),and the impact strength was 26 J/m(~130%higher than that of neat PLA).DSC results indicated that MCC-g-PCL reduced the Tg of the PLA blend.When the addition amount was 15 wt%,the Tg of the blend was 58.4°C.Compared with MCC,MCC-g-PCL polyester plasticizer has better thermal stability,T5%(°C)can still be maintained above 300°C.The rheological results showed that MCC-g-PCL acted as a plasticizer,the introduction of PCL flexible chain increased the mobility of PLA molecular chain,and decreased the complex viscosity,storage modulus and loss modulus of PLA blends.The MCC-g-PCL derivatives,as a new green plastic additive,have shown an interesting prospect to prepare fully bio-based composites.

Synthesis,Characterization and Water Absorption Analysis of Highly Hygroscopic Bio-based Co-polyamides 56/66

This study aims to develop highly hygroscopic bio-based co-polyamides(CPs)by melt co-polycondensation of polyamide(PA)56 salt and PA66 salt with varying molar fractions.The functional groups and the chemical structure of the prepared samples were determined by Fourier transform infrared(FTIR)spectroscopy and proton nuclear magnetic resonance(^(1)H-NMR)spectroscopy.The relative viscosity was determined with an Ubbelohde viscometer.The melting behavior and the thermal stability of CPs were investigated by differential scanning calorimetry(DSC)and thermogravimetric analysis(TGA).Furthermore,the water absorption behavior of CP hot-pressed film was studied.The results reveal that the melting point,the crystallization temperature and the crystallinity of CPs firstly decrease and then increase with the molar fraction of PA66 in CPs.The copolymerization of PA56 with PA66 leads to an obvious increase in water absorption.The CPs with PA66 molar fraction of 50%possess a high saturated water absorption rate of 17.6%,compared to 11.6%for pure PA56 and 7.8%for pure PA66.

High Water Resistance and Enhanced Mechanical Properties of Bio-Based Waterborne Polyurethane Enabled by in-situ Construction of Interpenetrating Polymer Network

In this study,acrylic acid was used as a neutralizer to prepare bio-based WPU with an interpenetrating polymer network structure by thermally induced free radical emulsion polymerization.The effects of the content of acrylic acid on the properties of the resulting waterborne polyurethane-poly(acrylic acid)(WPU-PAA)dispersion and the films were systematically investigated.The results showed that the cross-linking density of the interpenetrating network polymers was increased and the interlocking structure of the soft and hard phase dislocations in the molecular segments of the double networks was tailored with increasing the content of acrylic acid,leading to enhancement of the mechanical properties and water resistance of WPU-PAA films.Notably,with the increase in content of acrylic acid,the tensile strength,Young’s modulus,and toughness of the WPU-PAA-110 film increased by 3 times,and 8 times,and 2.4 times compared with WPU-PAA-80,respectively.The WPU-PAA-100 film showed the best water resistance,and the water absorption rate at 96 h was only 3.27%.This work provided a new design scheme for constructing bio-based WPU materials with excellent properties.

Research Status and Prospects of Bio-based Materials for Grease Barrier Coatings on Paper Food Packaging

Increased environmental and health concerns over the use of plastic packaging or fluorine-containing coatings,in combination with increased market demand for products with a longer shelf life,make bio-based materials one of the most important research candidates for alternative paper packaging materials for oil resistance.These bio-based materials have excellent oxygen and oil barriers,which are critical for food packaging.Moreover,they are biodegradable,naturally renewable,and safe.In this artical,two main groups of bio-based oil repellents for paper food packaging,including polysaccharide-based biopolymers and protein-based biopolymers,are enumerated,and the advantages and weaknesses of bio-based oil repellents are discussed,and effective solutions are proposed.Finally,research status and prospects on the development of bio-based oil-resistant coatings for the food packaging industry are presented.

Recycled, Bio-Based, and Blended Composite Materials for 3D Printing Filament: Pros and Cons—A Review

In recent years, additive manufacturing (AM), known as “3D printing”, has experienced exceptional growth thanks to the development of mechatronics and materials science. Fused filament deposition (FDM) manufacturing is the most widely used technique in the field of AM, due to low operating and material costs. However, the materials commonly used for this technology are virgin thermoplastics. It is worth noting a considerable amount of waste exists due to failed print and disposable prototypes. In this regard, using green and sustainable materials is essential to limit the impact on the environment. The recycled, bio-based, and blended recycled materials are therefore a potential approach for 3D printing. In contrast, the lack of understanding of the mechanism of interlayer adhesion and the degradation of materials for FDM printing has posed a major challenge for these green materials. This paper provides an overview of the FDM technique and material requirements for 3D printing filaments. The main objective is to highlight the advantages and disadvantages of using recycled, bio-based, and blended materials based on thermoplastics for 3D printing filaments. In this work, solutions to improve the mechanical properties of 3D printing parts before, during, and after the printing process are pointed out. This paper provides an overview on choosing which materials and solutions depend on the specific application purposes. Moreover, research gaps and opportunities are mentioned in the discussion and conclusions sections of this study.

Vitrimer材料的制备及性能研究进展

Vitrimer材料是一种含动态交联网络的高分子聚合物,在高温条件下,快速的动态交换反应使网络的拓扑结构发生改变和重排,从而使材料具有黏弹性和"流动性";并在保持材料化学结构和性能完整的情况下具有可塑性和可再加工性能。文中重点从酯交换反应、转酰胺反应、二硫化物重排反应和烷基转移反应等可逆交换反应类型论述了近年来国内外Vitrimer材料最新研究进展,对材料的动态可逆机理及性能特征进行了分析和对比,并对未来研究发展趋势进行了展望。

二胺结构对聚亚胺vitrimer材料性能的影响

利用对苯二甲醛和三(2-氨基乙基)胺分别与己二胺、1,4-二氨基环己烷、对苯二胺和间苯二胺发生席夫碱反应制备了PTI–H,PTI–CH,PTI–pP和PTI–mP四种聚亚胺vitrimer材料,并通过傅里叶变换红外光谱对其结构进行了表征。通过拉伸测试和动态热机械分析测试研究了二胺结构对聚亚胺vitrimer材料物理力学性能的影响。结果表明,具有刚性结构、较高交联密度的PTI–CH和PTI–mP展现出高的拉伸强度(≥55 MPa)、储能模量(>1.8 GPa)和低断裂伸长率(≤36%);具有刚性苯环结构但交联密度较低的PTI–pP具有最高的断裂伸长率(55.9%)和低的拉伸强度(38 MPa)、储能模量(1.77 GPa);具有柔性脂肪链结构、较低交联密度的PTI–H显示最低的拉伸强度(30.9 MPa)、储能模量(1.68 GPa)和较高的断裂伸长率(51.2%)。四种聚亚胺材料在玻璃化转变温度方面的排序为PTI–CH(86℃)>PTI–mP(84℃)>PTI–H(67℃)>PTI–pP(63.8℃)。四种聚亚胺材料在较低温度(120℃)下可重塑,经过两次重塑后,PTI–H的拉伸强度无明显降低,PTI–CH,PTI–pP和PTI–mP的拉伸强度有所提高,但四种材料的断裂伸长率均下降。

基于酯交换和纤维素基Vitrimer材料的制备与性能研究

以邻苯二甲酸醋酸纤维素(CAP)为基体、丁二酸酐(SA)为助剂、双酚A二缩水甘油醚(DGEBA)为固化剂制备了纤维素基可重塑Vitrimer材料CAP-SA-DGEBA,并优化了反应条件。采用FT-IR、凝胶分数测试(Gf)、DSC、SRA、TGA等对CAP-SA-DGEBA进行了表征,结果表明,体系内部形成了共价交联网络,CAP-SA-DGEBA凝胶分数可达71.4%,材料的玻璃化转变温度为44℃,应力松弛时间随温度升高而快速降低,较CAP的热分解温度提高了121℃。对材料进行重塑形发现,材料具备可重塑性能,重塑后依然保持良好的机械性能。

Bio-Based Hyperbranched Toughener From Tannic Acid and Its Enhanced Solvent-Free Epoxy Resin with High Performance

It is essential to design economic and efficient tougheners to prepare high-performance epoxy resin;however,this has remained a huge challenge.Herein,an eco-friendly,low-cost,and facile-fabricated bio-based hyperbranched toughener,carboxylic acid-functionalized tannic acid(CATA),was successfully prepared and applicated to the preparation of solvent-free epoxy resins.The mechanical performance,morphology,structural characterization,and thermal characterization of toughened epoxy resin system were studied.The toughened epoxy resin system with only 1.0wt%CATA reached the highest impact strength,111%higher than the neat epoxy resin system.Notably,the tensile strength and elongation at break of toughened epoxy resin systems increased moderately with increasing CATA loading.Nonphase-separated hybrids with significant toughening effect were obtained.Additionally,the thermal stabilities of toughened epoxy resin systems decreased with increasing CATA loading.This study provides an eco-friendly,cost-effective,and facile approach for the preparation of high-performance,solvent-free epoxy resins with potential for practical applications in sealing integrated circuits and electrical devices fields.