Use of wood fibers in thermoplastics. VII. The effect of coupling agents in polyethylene–wood fiber composites

Linear low density polyethylene (LLDPE) was reinforced with different wood fibers, aspen chemithermomechanical pulp (bleached and unbleached), and other commerical wood pulps. Silane coupling agents A-172, A-174, A-1100, and polymethylene polyphenyl isocyanate were used to improve the bonding between the fiber and matrix. LLDPE filled with pretreated wood fiber produced a significant improvement in tensile strength and modulus. Comparison of tensile and impact properties of wood fiber composites with mica and glass fiber composites shows the potential advantage (in terms of material cost and specific properties) of wood fiber as a reinforcement.     

Thermoplastic composties of polystyrene: Effect of different wood species on mechanical properties

Both softwood (spruce) and hardwood (aspen and birch) species in the form of different pulps (e.g., sawdust, chemithermomechanical pulp, explosion pulp and OPCO pulp) have been used (10–40 wt% composite) as reinforcing fillers for thermoplastic composites of polystyrene. Mechanical properties, are examined, e.g., tensile modulus, tensile strength at maximum point, and the corresponding elongation and energy as well as impact strength of compression molded composites. To improve the compatability of wood fibers which are hydrophilic and the polymer matrix which is hydrophobic, poly[methylene(polyphenyl isoeyanate)] (2 and 8 wt % of polymer) was used as a coupling agent. The mechanical properties of the treated composites are improved up to 30% in fiber content whereas a downward trend for untreated composites was observed when an increase in fiber content occurred. The overall improvements in mechanical properties due to the addition of isocyanate can be explained by the linkage of isocyanate molecules with fiber matrix through the chain of covalent bonds and the interaction of π-electrons of benzene rings of polystyrene as well as isocyanate. As a result, poly[methylene(polyphenyl isocyanate)] forms a bridge between fiber and polymer on the interfaces. This result is instrumental for efficient stress transfer between cellulose fibers and thermoplastics. The performance of different pulps of various wood species as reinforcing fillers for thermoplastic composites is also examined.     

废旧聚甲醛/改性竹纤维复合材料的力学性能研究

采用碱(NaOH)、硅烷偶联剂(KH560)、异氰酸酯(IPDI)等不同处理方法对废旧聚甲醛/竹纤维（POM/BF）复合材料的界面进行调控,研究了竹纤维改性方法和竹纤维含量对复合材料力学性能的影响。结果表明,NaOH+IPDI和NaOH+KH560能够实现对复合材料界面的调控,利用NaOH+2 %IPDI对BF进行处理后,POM/BF复合材料［BF为20 %（质量分数,下同）］的弯曲强度增加了13.38 %,拉伸强度为50.36 MPa;利用NaOH+5 %KH560对BF进行调控处理后,POM/BF复合材料的弯曲强度增加了12.61 %,拉伸强度为46.87 MPa;NaOH+2 %IPDI对BF的处理具有更好的效果,BF含量为20 %时复合材料的力学性能最佳。     

苎麻落麻的表面处理及其复合材料的性能研究

采用甲基丙烯酸甲酯、丙烯腈接枝,硅烷偶联剂(A-151)偶联,聚氯乙烯(PVC)包覆等方法对苎麻落麻纤维进行表面处理;测试了处理前后落麻纤维的吸水率、单丝强度及其与环氧树脂(EP)、酚醛树脂(PF)和不饱和聚酯(UP)等的接触角;观察了偶联和包覆后落麻纤维的表面状况;选取偶联和包覆后的落麻纤维制备了UP/落麻毡和PP/落麻纤维复合材料,测试了其拉伸和弯曲性能并观察了处理前后复合材料的拉伸断面形貌。结果表明,接枝、偶联和包覆不仅降低了落麻纤维的吸水速率。而且也降低了平衡吸水量;接枝对落麻纤维单丝强度影响最大,偶联次之,包覆最小;接枝、偶联和包覆均能大幅度改善落麻纤维与EP、PF和UP的浸润性;偶联和包覆后的落麻纤维表面都比处理前粗糙;偶联使UP/落麻毡复合材料的拉伸强度、拉伸弹性模量提高了21％,弯曲强度提高了34％,弯曲弹性模量提高了40％,包覆使PP/落麻纤维复合材料的拉伸、弯曲强度提高了20％左右。     

The Mechanical Properties of Wood Fiber-reinforced Polymethylmethacrylate

Abstract

The mechanical properties, e.g. tensile modulus (at 0.1% strain), tensile strength at maximum point and corresponding elongation and breaking energy, as well as impact strength, of compression molded PMMA and PMMA filled with wood fibers (10%-40% by weight of composite) have been investigated. Optimization of molding conditions, (e.g. temperature, time, pressure and mixing aids) was carried out. In optimum conditions of mixing and molding, the effect of different parameters, (e.g. nature and concentration of coupling agents (isocyanates), coating treatment, nature of wood species in the form of various pulps) on the mechanical properties of the resulting composites were evaluated. PMPPIC having 2%-4% (by weight of polymer) was found to behave as a true coupling agent because modulus as well as the tensile and impact strengths were improved. Moreover, PMPPIC acted as a coupling agent even when it was used for treatment of PMMA and fiber or to precoat the fiber. A distinct effect of the morphology of wood species and fiber-making techniques on the mechanical properties of wood fiber-filled composites was also observed.     

Influence of fiber surface treatment on mechanical performance of Xanthoceras sorbifolia bunge husk fibers/PP composites

The PP Composites containing Xanthoceras sorbifolia Bunge husks fibers with different surface treatments were prepared. The mechanical properties such as tensile properties and impact properties of the composites were investigated. It is revealed that the composites with fibers treated by alkali and the following treatments of silane coupling agents KH570, titanate coupling agent JN‐9A, acetic anhydride, MAPP, or bleach, all performed higher in tensile properties than that with untreated fibers, while lower in impact properties. Meanwhile, all treated fibers performed better thermal stability than untreated fibers. The fibers treated by alkali followed by KH570 treatment were added into PP with different contents. It is found that as the fiber content increases, the elastic modulus and impact strength of the composites increase sharply at first followed by a decrease, while the tensile strength decrease initially and increase with a peak at 10%, then decrease continuously. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41217.     

香蕉纤维的表面改性及其增强环氧树脂复合材料的性能研究

采用硅烷偶联剂(A-174)偶联、高锰酸钾接枝和乙酰化包覆等3种方法对香蕉纤维进行表面改性,制备了改性香蕉纤维增强环氧树脂复合材料,测试其拉伸、弯曲、压缩、冲击等力学性能。结果表明,偶联、接枝、包覆等表面改性均能明显改善香蕉纤维与基体树脂的相容性,提高复合材料的力学性能,其中偶联改性的效果最好。当改性香蕉纤维含量为10wt%时,与未改性的香蕉纤维比较,复合材料的拉伸强度、弯曲强度、压缩强度分别提高了1.8、1.0、2.6倍;随着纤维含量的增加,复合材料的力学性能明显提高。     

Acid-base interfaces in fiber-reinforced polymer composites

The role of Lewis acid-base interactions at the fiber-matrix interface in composites is studied with both glass and Teflon fibers. In the glass fiber case, surface chemistry is modified with amino-, methacryloxy- and glycidoxy-silane coupling agents (A-1100, A-174 and A-187, respectively). Silane adsorption mechanisms as well as the properties of filament-wound, unidirectional epoxy and polyester composites are explained by a combination of X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and flow microcalorimetry. The heats of adsorption of pyridine and phenol prove that the coupling agents add acidic sites to the glass fiber surface as well as stronger basic sites. The subsequent adhesion of the matrix polymers and the short beam shear strengths of composites are explained on this basis. The Teflon fibers are first etched with sodium naphthalene solutions, and then sequentially hydroborated and acetylated, producing approximately monofunctional hydroxyl (acidic) and ester (basic) groups on the surfaces, as determined by XPS, FTIR, and electrophoretic mobility analyses. Composites prepared with the acetylated fibers and a chlorinated polyvinyl chloride (acidic) matrix are superior in tensile properties, and SEM fractography shows PTFE fibrillation, indicative of good fiber-matrix adhesion and stress transfer, in this case only.     

Effect of Mercerization on Surface Modification of Henequen (Agave fourcroydes) Fiber by Photo-Curing with 2-Hydroxyethyl Methacrylate (HEMA)

Abstract

Henequen fibers were cured under ultraviolet (UV) radiation with 2-hydroxyethyl methacrylate (HEMA) in order to improve the mechanical properties and reduce the water absorption. A series of solutions of different HEMA concentration in methanol along with photoinitiator Irgacure 907 was prepared. The radiation dose, monomer (HEMA) concentration and soaking time were optimized with respect to grafting of monomer and mechanical properties of cured fiber. 3% HEMA, 5 min soaking time, at the ninth pass of radiation, produced higher tensile strength (190%) and elongation at break (195%), than those of the virgin fiber, as well as the highest grafting value (4.2%). For further improvement of the mechanical properties, the fibers were treated with an alkali (KOH) solution of various concentrations for 1 h before curing. 10% alkali-treated fibers showed increased properties, such as grafting (5.4%), tensile strength (300%), and elongation at break (290%) over raw fiber. The treated fiber showed lower water uptake than the untreated ones. The grafted fibers were also characterized by IR and it was observed that HEMA deposited on the fiber surface may react with the cellulose backbone of the Henequen fibers.     

发泡工艺对高回弹聚氨酯泡沫塑料力学性能的影响

采用自制聚合物聚醚多元醇(POP-A)和聚醚多元醇(KGF5020)与异氰酸酯(PM200/TDI)体系制备一种高回弹聚氨酯泡沫塑料。探讨了发泡工艺对其力学性能的影响。确定了最佳发泡工艺:m(H2O)∶m(A-1)∶m(A-33)∶m(多元醇)为(3.0～3.5)∶0.15∶0.30∶100;采用Y-10366为泡沫稳定剂,DEOA为扩链剂。聚醚中KGF5020以及异氰酸酯中TDI的质量分数为50%。异氰酸酯指数大于1.02,模具的温度为65℃,室温下熟化时间为72h。在此条件下制品的力学性能:拉伸强度为171kPa,断裂伸长率为230%,回弹率为58.7%,Tg为47℃,撕裂强度为3.2N/cm,压陷因子为2.3,氧指数为28。     

氧化锌晶须/聚丙烯复合材料性能的研究

制备了四针状氧化锌晶须(T—ZnOw)／聚丙烯复合材料,研究了不同偶联剂处理的T—ZnOw及其用量对复合材料力学性能的影响,并对偶联机理做了初步探讨。研究结果表明,当添加T-ZnOw质量分数为20％时,复合材料的力学性能最好;与处理前相比,处理后的T—ZnOw复合材料的拉伸强度和冲击强度有不同程度的提高;不同偶联剂处理的T—ZnOw对复合材料力学性能的影响不同。     

Surface modification of aramid fibers with CaCl2 treatment and secondary functionalization of silane coupling agents

Aramid fibers have excellent mechanical properties as the main reinforcing filler in high-performance composites. However, the adhesion properties between fibers and most polymer matrices were poor. In this study, aramid fiber (AF) was modified by KH550 through surface coating based on the treatment with CaCl₂ solution. The new surface treated with complexing agents could act as an active platform for secondary reactions for further modification. The surface morphology and composition of the treated aramid fibers were tested by scanning electron spectroscopy and X-ray photoelectron spectroscopy, the interlaminar shear strength and the tensile strength of aramid fiber-reinforced polymer (AFRP) of were evaluated. The results showed that the silane coupling agent KH550 was successfully grafted onto the surface of aramid fibers after treatment with CaCl₂. Interlayer shear strength is greatly improved and the tensile strength of AFRP through further grafting with KH550 on the surface treated with CaCl₂ was improved by 48.7%, compared with untreated aramid fiber. In the current scenario, this study is of immense importance because it validates the possibility of secondary modification after fiber complexation modification and useful modification methods, and provides a new direction for the modification of AF.     

生物可降解山麻杆韧皮纤维增强PBS复合材料的性能研究

以山麻杆韧皮纤维为增强体,其与PBS颗粒按质量比20∶80模压成型制备了4种板材,探讨了表面处理对纤维微观结构与物理性能的影响,分析比较了板材力学性能及生物降解性。结果表明, 采用物理化学相结合方法预处理后,表面依然存留一定量的果胶等物质;预处理纤维进一步碱处理后表面出现“S”形凹槽,预处理纤维进一步偶联剂处理后表面凹槽连续性好、深度深;碱处理、偶联剂处理后纤维拉伸强度分别提高5.08 %和降低3.58 %;相比纯PBS,偶联剂处理后纤维复合材料拉伸强度与弯曲强度各提高48.32 %和25.97 %,拉伸模量与弯曲模量各提高146.45 %和128.30 %;3种纤维复合材料生物可降解性变化趋势一致,但偶联剂处理后的材料失重率变化幅度最小。     

Surface modification of cellulose fibers. II. The effect of cellulose fiber treatment on the performance of cellulose–polyester composites

Cellulose fibers treated with different coupling agents based on trichloro-s-triazine have been evaluated in terms of their reinforcement effect on unsaturated polyesters. The treatment with coupling agents containing double bonds resulted in what we believe to be the formation of covalent bonds between fiber and matrix. This has been compared with a treatment, which can only lead to formation of close interfacial molecular contact by wetting. The tensile properties of composites prepared from treated and untreated fibers were studied before and after exposure to water. It was found that all types of fiber treatment decreased water absorption and the reduction of mechanical properties in wet conditions, but that the degradation at the fiber/matrix interface which occurs from immersion in water and drying could only be avoided through the development of covalent bonds between fiber and matrix. Scanning electron microscopy was used to study the adhesion between fiber and matrix. An explanation of the reduction of mechanical properties of cellulose-fiber reinforced polymers in wet conditions is proposed.     

Performance of hybrid reinforcements in PVC composites. II: Use of surface-modified mica and different cellulosic materials as reinforcements

The effect of the composition of various wood fibers and surface-treated mica as well as different surface treatments of cellulosic materials on the mechanical properties of PVC composites has been evaluated. Cellulosics were surface modified by prior coating with maleic andydride (MA), mixtures of MA and Na-silicate and isocyanate. The filler concentration was fixed at 25 wt%. Both tensile strength and modulus of composities filled solely with mica are superior to those of non-treated wood fiber-filled composities. while the reverse is true for impact strength (except for bagasse-filled composities), ultimate elongation, and tensile toughness. Moreover, the mechanical properties of composities, with the exception of modulus, filled only with mica and/or non-treated wood fibers are inferior to those of unfilled PVC. Compared to non-treated fiber-filled composites, properties improved when surface-modified wood fibers were used alone, or along with mica. Isocyanate-coated wood fibers ranked best with regard to the mechanical properties of the composities. Properties also changed with the change of wood species and compositions of mica and wood fibers. Experimental results indicate good compatibility between surface-treated wood fibers/mica and PVC composities.     

Effect of macromolecular coupling agent on the property of PP/GF composites

Silane‐grafted polypropylene manufactured by a reactive grafting process was used as the coupling agent in polypropylene/glass‐fiber composites to improve the interaction of the interfacial regions. Polypropylene reinforced with 30% by weight of short glass fibers was injection‐molded and the mechanical behaviors were investigated. The results indicate that the mechanical properties (tensile strength, tensile modulus, flexural strength, flexural modulus, and Izod impact strength) of the composite increased remarkably as compared with the noncoupled glass fiber/polypropylene. SEM of the fracture surfaces of the coupled composites shows a good adhesion at the fiber/matrix interface: The fibers are coated with matrix polymer, and a matrix transition region exists near the fibers. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1537–1542, 1999     

The influence of chemical surface modification on the performance of sisal‐polyester biocomposites

This article concerns the effectiveness of various types and degrees of surface modification of sisal fibers involving dewaxing, alkali treatment, bleaching cyanoethylation and viny1 grafting in enhancing the mechanical properties, such as tensile, flexural and impact strength, of sisal‐polyester biocomposites. The mechanical properties are optimum at a fiber loading of 30 wt%. Among all modifications, cyanoethylation and alkali treatment result in improved properties of the biocomposites. Cyanoethylated sisal‐polyester composite exhibited maximum tensile strength (84.29 MPa). The alkali treated sisal‐polyester composite exhibited best flexural (153.94 MPa) and impac strength (197.88 J/m), which are, respectively, 21.8% and 20.9% higher than the corresponding mechanical properties of the untreated sisal‐polyester composites. In the case of vinyl grafting, acrylonitrile (AN)‐grafted sisal‐polyester composites show better mechanical properties than methyl‐methacrylate (MMA)‐grafted sisal composites. Scanning electron microscopic studies were carried out to analyze the fiber‐matrix interaction in various surface‐modified sisal‐polyester composites.     

Effect of grafting yield and molecular weight of m‐TMI‐grafted‐PP on the mechanical properties of wood fiber filled polypropylene composites

m‐Isopropenyl‐α, α‐dimethylbenzyl isocyanate (m‐TMI) was grafted on isotactic polypropylene (PP) using di‐cumyl peroxide as a reaction initiator under varying reaction conditions to yield m‐TMI‐g‐PP coupling agent with four sets of grafting yield and molecular weight. Grafting yield of the synthesized m‐TMI‐g‐PP were 1.80%, 2.01%, 9.05%, and 8.86% and molecular weight of the corresponding grafted polymer were 129,225; [Correction made here after initial online publication.] 187,240; 124,130; and 180,838, respectively. Rubberwood flour reinforced polypropylene composites were prepared using these coupling agents and tested for mechanical properties. m‐TMI‐g‐PP coupling agent with 9.09% grafting and 124230 M_w was found to give the highest tensile and flexural strengths. Flexural modulus of the coupled composites was higher than uncoupled composites. Interfacial region of the composites characterized by scanning electron microscope (SEM) suggest effective wetting of fiber by PP in the case of coupled composites. The effect of fiber loading on composites indicates continuous increment in tensile and flexural strengths in coupled composites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44196.     

Surface modification of bagasse fibers by silane coupling agents through microwave oven and its effects on physical,mechanical, and rheological properties of PP bagasse fiber composite

Polypropylene/bagasse fiber composites were prepared by compounding polypropylene (PP) with bagasse fibers as reinforcing filler. Surfaces of fibers were modified through the use of silane coupling agents (Vinyltrimethoxysilane and γ‐Glycidoxypropyltrimethoxysilane). The fiber coating was performed by mixing of silane with fibers and cured through microwave oven in presence of catalyst. It was found that modification of surface fiber will change the physical, mechanical, morphological, and rheological properties of composite. It was observed from scanning electron microscopy that fiber adhesion to matrix has been improved and so as dispersion. Addition of fibers increases the melt viscosity in unmodified fibers but reduced the melt viscosity for modified fibers and even the viscosity is lower at higher loading compared with unmodified fibers. The tensile strength and tensile modulus increased in modified fibers compared with the unmodified on the same loading, but elongation at break decreased. The effect of coupling agent on properties of filled PP depend on the content of coupling agents and optimum amount was achieve through measurement of water absorption. Two types of coupling agents were used, one as A‐171 [CH₂CHSi (OCH₃)₃] and second one as A‐187 [CH₂OCHCH₂O (CH₂)₃Si(OCH₃)], the first one shows better adhesion to the fibers and improvements in mechanical properties are much better compared with the second one. POLYM. COMPOS., 28:713–721, 2007. © 2007 Society of Plastics Engineers     

Use of wood fibers in thermoplastic composites: VI. Isocyanate as a bonding agent for polyethylene–wood fiber composites

Linear low density (LLDPE) and high density (HDPE) polyethylenes were reinforced with wood fibers of aspen chemithermomechanical (CTMP) pulp. The different isocyantes: (i) polymethylene (polyphenyl isocyanate), (ii) tolene –2–4-diisocyanate, (iii) 1–6 hexamethylene-diisocyanate, and (iv) ethyl isocyanate used as bonding agents improved the tensile properties of the composites. HDPE performed better in comparison with LLDPE composites. Also, shorter fibers (mesh size 60) produced higher tensile strength and modulus in HDPE. The comparison of HDPE reinforced with aspen, mica, and glass fibers showed the effectiveness of wood fibers in terms of their cost and performance.