Oil Palm Wood Flour Filled Natural Rubber Composites: The Effects of Various Bonding Agents

Abstract

The effects of various bonding agents on curing characteristics and mechanical properties of oil palm wood flour (OPWF) filled natural rubber composites were examined. Compared to control compound the presence of various bonding agents increase the curing time, t₉₀ , maximum torque (except phenol formaldehyde(PF) and resorsinol formaldehyde(RF)/Silica(Sil)), tensile strength, tensile modulus (except PF and RF/ Sil), and hardness (except PF) but decrease the elongation at break and fatigue life of the composites. Swelling test results indicate that the presence of various bonding agents lead to stronger adhesion at the OPWF-rubber interface. Overall results indicate that RF/Sil/Hexa (Hexamethylene tetramine) is the most suitable bonding system for OPWF filled natural rubber composites.     

Effect of Coupling Agent Concentration,Fiber Content,and Size on Mechanical Properties of Wood/HDPE Composites

In this study, the influence of coupling agent concentration (0 and 3 wt%), wood fiber content (50, 60, 70, and 80 wt%), and size (40–60, 80–100, and 160–180 mesh) on the mechanical properties of wood/high-density-polyethylene (HDPE) composites (WPCs) was investigated. WPC samples were prepared with poplar wood-flour, HDPE, and polyethylene maleic anhydride copolymer (MAPE) as coupling agent. It was found that the tensile properties and the flexural properties of the composites were improved by the addition of 3 wt% MAPE, and the improved interfacial adhesion was well confirmed by SEM micrographs. It was also observed that the best mechanical properties of wood/HDPE composites can be reached with larger particle size in the range studied, while too-small particle size was adverse for the mechanical properties of wood/HDPE composites. Moreover, the tensile modulus, tensile strength, and flexural strength of WPCs decreased with the increase in fiber content from 50 to 80 wt%; the flexural modulus of WPCs increased with the increase in fiber content from 50 to 70 wt% and then decreased as the fiber content reached 80 wt%. The variances in property performance are helpful for the end-user to choose an appropriate coupling agent (MAPE) concentration, wood fiber content, and particle size based on performance needs and cost considerations.     

硅烷偶联剂在玻纤增强复合材料领域中的应用

介绍了玻纤生产中常用硅烷偶联剂的种类、结构、偶联机理及使用方法。着重介绍了硅烷偶联剂在玻纤增强复合材料中的应用,特别是硅烷结构类型、用量对复合材料性能的影响。同时,对硅烷偶联剂的作用及其在玻纤增强热固性和热塑性树脂中的应用进行了阐述。     

木纤维增强热塑性复合材料的界面研究现状

综述了目前国内外关于木纤维增强热塑性复合材料界面的研究进展，介绍了常用的几种改善木塑复合材料界面相容性的方法，并分析了各自的优缺点。     

嵌段共聚物偶联剂对玄武岩纤维增强聚丙烯复合材料的改性研究

玄武岩纤维(BF)增强聚丙烯(PP)复合材料体系中,引入了聚苯乙烯(PS)与聚丙烯酸羟乙酯(PHEA)的嵌段共聚物大分子偶联剂(PS-b-PHEA),以改善复合材料的界面性能。结果表明:通过嵌段共聚物PS-b-PHEA对复合材料改性,一方面能够使玄武岩纤维与PP基体具有良好的界面黏结,另一方面能够在界面处形成柔性层,松弛界面热应力,迅速分散外加载荷,吸收外力的能量,实现复合材料的增强增韧。     

偶联剂在热塑性聚合物/天然纤维复合材料中的研究进展

偶联剂是一种重要的助剂,按化学组成可分为有机偶联剂、有机-无机偶联剂、无机偶联剂。文章重点阐述应用于热塑性聚合物/天然纤维复合材料中各种偶联剂的作用机理及改性效果。     

Immersion Temperature Effects on the Water Absorption Behavior of Hybrid Lignocellulosic Fiber Reinforced-Polyester Matrix Composites

Although economic, ecological, processing and property considerations suggest that it is very attractive to use lignocellulosic fibers as reinforcement in polymer matrix composites, moisture can strongly and deleteriously affect their properties. In this work the water absorption behavior of sisal/cotton, jute/cotton and ramie/cotton hybrid fabric reinforced composites is evaluated. The effect of the temperature of immersion, fiber volume fraction, and predrying of the fabrics before their incorporation onto the composites are evaluated. Sisal was shown to be the most hygroscopic of the fibers analyzed, and its presence leads to higher values of the maximum water content and of the diffusion coefficient of sisal/cotton reinforced composites. Under the range of temperatures analyzed (30–60°C) the volume fraction of the fibers, rather than the temperature itself, was shown to be the main parameter governing water absorption. Predrying usually lowers maximum water content, although for sisal/cotton reinforced composites a reverse trend was observed for the composites with higher volume fractions. This behavior was again attributed to the higher hydrophilic behavior of sisal fibers.     

Influence of Polar Monomers on the Performance of Wood Fiber Reinforced Polystyrene Composites. I. Evaluation of Critical Conditions

Abstract

Wood fibers and nonpolar thermoplastics, e.g. polystyrene, are not the ideal partner for the preparation of composites because of a wide difference in their polarity. In the present study, polarity of the polystyrene was modified by the introduction of a—COOH group, through the reaction with maleic anhydride (MA) in the presence of an initiator (benzoyl peroxide: BPO) in a roll mill at the elevated temperatures. Optimum conditions for the preparation of polar polystyrene have been investigated. The temperature of the roll mill, i.e., the reaction temperature, and reaction time varied between 160–175°C and 10–15 min., respectively. The concentrations of the monomer, (MA) as well as the initiator (BPO), also varied: 0–10% and 0–2% (by weight of polymer), respectively. The mechanical properties of chemithermomechanical pulp (CTMP)-filled modified polystyrenes were evaluated. The effect of 3% coupling agent [e.g. poly(methylene (polyphenyl isocyanate))] (PMPPIC) on the mechanical properties of the same composites was also determined.

Generally, mechanical properties of the composite materials were enhanced when modified polymers were used as base polymers. Moreover, the extent of the improvement in mechanical properties depends on the reaction temperature and time, as well as on the concentrations of the monomer (maleic anhydride) and initiator. Maximum improvements in mechanical properties occur when the temperature was maintained at 175°C for 15 min. In addition, preferred concentrations of both the monomer and initiator were found to be 5% and 1% (by polymer weight), respectively. Once again, properties were further accelarated when coupling agent (e.g. PMPPIC) was used in addition to the modified polystyrene. The improvements in mechanical properties (over those of the original polymer and those of composites containing unmodified polymers) indicate that the compatibility between hydrophilic cellulosic fiber and hydrophobic polymer has increased.     

Dynamic Mechanical and Thermal Properties of Modified Poly(propylene) Wood Fiber Composites

Dynamic mechanical and thermal properties of poly(propylene) (PP)/wood fiber composites have been studied using Dynamic Mechanical Analysis (DMA). In order to modify the PP matrix maleated poly(propylene) (PPMA) and poly(butadiene‐styrene) rubber were used as compatibilizer and impact modifier, respectively. tan δ peak temperature of the compatibilized systems was found to increase in comparison to that of composites without coupling agent, indicating improved adhesion and interaction between PP matrix and wood fibers. The storage modulus (E′)‐temperature (T) relationship of all composites is characterized by two transition points. The E′ of compatibilized composites exhibits higher values than those of the uncompatibilized ones at low temperatures (up to the β‐relaxation). In the temperature interval from β‐transition to 60 °C, the composites containing PPMA have lower modulus, and above 60 °C the E′‐T curves tend to converge. DSC indicates that the wood fibers act as nucleating agent for PP. Maleated poly(propylene) slightly retards the crystallization rate, resulting in a composite structure, composed mainly of large spherulites, with a higher crystallinity index. Fourier Transform Infrared (FT‐IR) microscopy was also applied to explore the interface between wood fibers and PP matrix. The strong absorption band at 1 738 cm^?1 in the IR spectrum scanned at the interfacial region between the fiber and matrix indicated that PPMA had probably reacted either by formation of ester bonds or hydrogen bonding with hydroxyl groups from cellulose.

Optical micrograph of PPWF composite in polarized light.     

Effect of Coupling Agents on the Performance of PP/MAH-g-PP/CaCO3 Ternary Composites

This study deals with the creation and characterization of a polypropylene/calcium carbonate composite in the presence of maleic anhydride–grafted polypropylene used as a compatibilizer. In order to improve the properties of the interfacial zones, the reinforcing filler was treated with two different coupling agents, which were a silane named Dow Corning Z-6020 and a zirconate coupling agent named Ken-React NZ-44. The performance of the interface within the composites was assessed through the measurement of the mechanical and thermal properties. The results revealed an important enhancement of the impact strength and the heat deflection temperature as a result of surface treatment. The analysis of the relative evolution of those properties showed that a more pronounced reinforcing effect was obtained with the NZ-44 coupling agent. The improvement in the properties seemed to depend particularly on the state of the dispersion of the filler throughout the matrix and on the nature of the interface. The thermogravimetric analysis allowed the conclusion that the filler improved the thermal stability of the material but the coupling agent did not seem to have any influence on this property.     

Influence of Electron Beam Irradiation and Coupling Agents on the Thermal Stability of Sugar Cane Bagasse Fiber-Thermoplastics Scrape Composite

The influence of blending of sugar cane bagasse with thermoplastics scrape as well as incorporation of some coupling agents has been conducted using thermogravimetric analysis (TGA). In addition, the effect of electron beam preirradiation of low density polyethylene on the properties of the bagasse-LDPE composite was also studied. Simulation of TGA data reveals that the presence of bagasse fiber accelerates the volatilization of either polypropylene or polyvinylchloride. On the other hand, polyethylene and polystyrene were stable against the heat evolved during the pyrolysis of bagasse fibers. Also, it was found that incorporation of a mixture of pentaerithrol tetraacrylate (PETA) and dicumyl peroxide (DCP) as coupling agents improve the thermal stability of low density polyethylene whereas the role of irradiation was insignificant. Moreover, pronounced enhancement in the thermal stability was detected in polypropylene followed by polystyrene and polyvinylchloride on using PETA.     

Influence of a Rare-Earth Coupling Agent on the Interfacial Interaction of Wood Flour/Polypropylene Composites

Abstract

In this article, the influence of a rare-earth (RE) coupling agent on the interfacial interaction of wood flour/polypropylene composites (WF/PP) was investigated by studying the rheology behavior and the mechanical properties and using differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The increased equilibrium torque results implied that the composites had a greater frictional shear force, which probably resulted from strong adhesion at the interface between the WF and PP. The mechanical property results showed that the added RE improved: the tensile strength by 42.6%; the flexural strength by 66.7%; and the impact strength by 92.3%, when compared to the WF/PP composites containing no RE material. According to the DSC results, the addition of the RE decreased the crystallization temperature and melting temperature. These results showed that the RE improved the interfacial adhesion. This was further confirmed by the SEM analysis of the composites.     

复合材料用天然植物纤维改性研究进展

天然植物纤维的结构和性能独特,与树脂基体复合仍存在诸多问题。天然植物纤维改性对于提高反应活性、改善其与基体树脂的界面相容性及复合材料的综合性能有重要影响。从天然植物纤维原料的组成、结构及性能分析出发,重点介绍了蒸汽爆破预处理、热预处理、高能辐射预处理、碱预处理、过氧化物预处理和组合法预处理等预处理技术以及酯化改性、接枝共聚、偶联剂改性和其他改性方法,并综述了改性天然植物纤维在复合材料中的研究进展,总结了天然植物纤维改性对复合材料性能的影响,以期为天然植物纤维复合材料的研究提供思路和参考。     

偶联剂对稀土荧光竹塑复合材料发光性能和流变性能的影响

研究了马来酸酐接枝聚乙烯(MAPE)、γ(2,3-环氧丙氧)丙基三甲氧基硅烷(KH-560)、异丙基三(硬脂酰基)钛酸酯(YB-510)3种偶联剂对稀土荧光竹塑复合材料发光性能和流变性能的影响。利用荧光分光光度计和旋转流变仪对复合材料的发光性能和流变性能进行了表征。结果表明,相比于未添加偶联剂,3种偶联剂均能改善复合材料的加工流动性和铝酸锶荧光粉的分散性,提高了发光强度,MAPE改善得最好;储能模量(G′)和损耗模量(G″)随频率的增大而呈线性增大,高频区逐渐趋于缓和,在低频区,添加偶联剂的复合材料的“似固体行为”对频率的依赖性较弱,填料与基体形成的网状结构更明显;偶联剂降低了复合体系的复数黏度,改善了加工性能, KH-560和MAPE的改善效果较好。     

Investigation of Steel/Epoxy Adhesion Durability Using Polymeric Coupling Agents III. Influence of Coupling Agent Layer Thickness

Steel/epoxy peel specimens were prepared using ethylene-mercaptoester (EME) copolymer coupling agents (90 wt% mercaptoester units) applied in thickness ranging from 25 to 350 Å. An optimum thickness of approximately 140 Å, which corresponded to an over 200% increase in peel strength when compared to 50 Å thick samples, was determined from ellipsometry and 90° peel strength measurements. The corrosion protection obtained was essentially independent of coupling agent thickness.     

Evaluation of Coupling Agents in Poly(propylene)/Fly Ash Composites: Effect on Processing and Mechanical Properties

Composites containing 50 wt.‐% fly ash in a PP homopolymer were prepared via batch mixing and compression moulding. The following coupling agents were evaluated: Lubrizol Solplus C800, N,N′‐(1,3‐phenylene)dimaleimide, γ‐methacryloxypropyltrimethoxysilane and maleic‐anhydride‐grafted PP. At the filler level investigated, C800 gave the best balance of composite strength and toughness. In the latter case filler‐matrix adhesion appeared weaker relative to γ‐MPS, BMI and m‐PP, all of which gave excessively strong filler‐matrix adhesion leading to a reduction in composite toughness. The unexpected weakness of the C800/fly ash interaction may be related to removal of surface calcium ions from the fly ash via reaction of a single calcium ion with two C800 molecules.

     

不同相容剂对PP/木粉复合材料力学性能的影响

研究了3种相容剂和3种偶联剂分别在单独使用和配合使用情况下对PP/木粉(质量比50/50)复合材料力学性能的影响。相容剂PP-g-MAH、PE-g-MAH、SBS-g-MAH单独使用发现:SBS-g-MAH使材料综合性能最好,PE-g-MAH对冲击强度提高明显。硅烷偶联剂HP-172在提高复合材料的冲击强度和拉伸强度方面较好,HP-174对弯曲性能改善较好,钛酸酯偶联剂NDZ-201仅对弯曲模量有所改善,而对其它性能改善不大。相容剂与偶联剂共同使用具有协同效应,其中HP-174与SBS-g-MAH并用效果最好,使各项力学性能都有提高。     

Short Palm Tree Fibers Polyolefin Composites: Effect of Filler Content and Coupling Agent on Physical Properties

Short date palm tree lignocellulosic fibers have been used as a reinforcing phase in commodity thermoplastic matrices [poly(propylene) and low density polyethylene]. Compatibilization of the fibers was carried out with the use of maleic anhydride copolymers. The morphology, thermal and mechanical properties of the resulting composites were characterized using SEM, DSC and tensile tests. The reinforcing capability of the unmodified fibers was found to depend on the nature of the matrix and the main parameter governing the composite behavior was the degree of crystallinity of the matrix. Compatibilization was reported to enhance the mechanical performances for both sets of composites up to a critical amount of compatibilizer beyond which the degree of crystallinity of the matrix decreases.

     

Modification of Rheological Properties Under Elongational Flow by Addition of Polymeric Fine Fibers

A new technique to provide melt elasticity using flexible fine fibers prepared from a polymer with high melting point is demonstrated. A polymer composite of poly(propylene) with a small amount of fine fibers of poly(butylene terephthalate) shows marked strain‐hardening behavior in elongational viscosity, i.e., a rapid increase in the transient elongational viscosity with time or strain. The blend also shows prominent normal stress difference at steady shear. These elastic properties have not been observed for polymer composites with rigid fibers and can be applicable to the modification of rheological properties and thus the improvement of processability.

     

The Influence of Excess Coupling Agent on the Microdeformation Processes and Mechanical Properties of Poly(propylene)/Wood‐Flour Composites

Summary: It is well known that coupling agents improve the adhesion between poly(propylene) and wood fillers leading to an increase of the composite mechanical properties. Above a certain concentration limit of the coupling agent, however, deterioration of the mechanical properties often occurs, and little attention has been directed so far towards finding out the reasons for that behavior. Transmission electron microscopy and high‐voltage electron microscopy were used in this work to study the morphology and microdeformation behavior of PP/wood‐flour composites modified with high amounts of maleated poly(propylene) as a coupling agent. It was found that the coupling agent containing a higher concentration of grafted maleic anhydride forms a separate phase in the poly(propylene) matrix, influencing the mechanical properties of the composites.

HVEM micrograph of the deformation structure of wood‐filled poly(propylene) composite showing fibrils stretching between the coupling agent domains and the PP matrix.