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Improvement in the mechanical performance and interfacial behavior of kenaf fiber reinforced high density polyethylene composites by the addition of maleic anhydride grafted high density polyethylene
通过添加马来酸酐接枝高密度聚乙烯改善洋麻纤维增强高密度聚乙烯复合材料的机械性能和界面行为

Fauzani Md. Salleh • Aziz Hassan • Rosiyah Yahya •
福扎尼·马德·萨利 • 阿齐兹·哈桑 • 罗西亚·叶海亚 •Ruth A. Lafia-Araga • Ahmad Danial Azzahari •
露丝·拉菲亚-阿拉加 • 艾哈迈德·丹尼尔·阿扎哈里 •Mohd Nazarul Zaman Mohd Nazir
莫哈末纳扎鲁扎曼 Mohd Nazir

Received: 12 December 2013 / Accepted: 7 April 2014 /Published online: 19 April 2014
收稿日期： 2013-12-12 /录用日期：2014-4-7 /在线出版日期：2014-04-19
© Springer Science+Business Media Dordrecht 2014
© Springer Science + Business Media 多德雷赫特 2014

Abstract  抽象

The effects of compatibilizer on the tensile, flexural and interfacial adhesion behavior of kenaf fiber reinforced high density polyethylene composites were investigated. The addition of maleic anhydride grafted high density polyethylene (MA-HDPE) as compatibilizer into the composites was found to improve the mechanical properties and the adhesion behavior of the composites. These improvements were due to the improved compatibility between matrix and fiber. 8 % 8 % 8%8 \% MA-HDPE loading provided maximum enhancement in tensile and flexural properties when compared to the other compatibilizer contents. Meanwhile, uncompatibilized composites showed poorer mechanical properties and interfacial behavior relative to the compatibilized composites. Fourier transformed infrared spectroscopy analysis confirmed the changed chemical structures by the appearance of stretching vibration of the ester carbonyl groups ( C = O ) ( C = O ) (C=O)(\mathrm{C}=\mathrm{O}) around 1725 cm − 1 1725 cm − 1 1725cm^(-1)1725 \mathrm{~cm}^{-1} to 1742 cm − 1 1742 cm − 1 1742cm^(-1)1742 \mathrm{~cm}^{-1} and the peak of hydroxyl group at 3327 cm − 1 3327 cm − 1 3327cm^(-1)3327 \mathrm{~cm}^{-1} in the compatibilized composites. This indicates that the maleic anhydride has bonded to the kenaf fiber through esterification reaction, giving rise to strong interfacial bonding between the matrix and fiber. The improvement in the interfacial behavior was evident from the tensile fracture
研究了增容剂对洋麻纤维增强高密度聚乙烯复合材料的拉伸、弯曲和界面粘附行为的影响。发现在复合材料中添加马来酸酐接枝高密度聚乙烯 （MA-HDPE） 作为相容剂可以改善复合材料的机械性能和粘合性能。这些改进是由于基体和纤维之间的兼容性得到改善。 8 % 8 % 8%8 \% 与其他增容剂含量相比，MA-HDPE 负载在拉伸和弯曲性能方面提供了最大的增强。同时，相对于相容复合材料，不相容复合材料表现出较差的力学性能和界面行为。傅里叶变换红外光谱分析通过相容复合材料中酯羰基 ( C = O ) ( C = O ) (C=O)(\mathrm{C}=\mathrm{O}) 周围的 1725 cm − 1 1725 cm − 1 1725cm^(-1)1725 \mathrm{~cm}^{-1} 拉伸振动 1742 cm − 1 1742 cm − 1 1742cm^(-1)1742 \mathrm{~cm}^{-1} 和羟基峰值的 3327 cm − 1 3327 cm − 1 3327cm^(-1)3327 \mathrm{~cm}^{-1} 出现证实了化学结构的变化。这表明马来酸酐通过酯化反应与洋麻纤维结合，从而在基体和纤维之间产生很强的界面结合。从拉伸断裂中可以明显看出界面行为的改善

surface morphology using a field emission scanning electron microscopy.
使用场发射扫描电子显微镜的表面形态。
Keywords Mechanical properties • Interfacial behavior • Compatibilizer • Kenaf fiber
关键词 机械性能 • 界面行为 • 相容性 • 洋麻纤维

1. Introduction  1. 引言

Kenaf fiber is a type of lignocellulosic natural fiber which has the potential to be used as a replacement for the traditional reinforcement materials in composites. The addition of kenaf fiber is believed to confer strength and rigidity to the weak and brittle plastic matrix, reducing the high manufacturing cost of plastic application and increasing the value of natural fiber. Furthermore, the global demand for natural fibers is increasing due to a greater request for green industrial products.
洋麻纤维是一种木质纤维素天然纤维，有可能用作复合材料中传统增强材料的替代品。洋麻纤维的添加被认为可以赋予弱脆塑料基体强度和刚度，降低塑料应用的高制造成本并增加天然纤维的价值。此外，由于对绿色工业产品的需求增加，全球对天然纤维的需求正在增加。
However, drawback factors such as the tendency to form aggregates during processing, poor resistance to moisture, and weak interaction and adhesion in lignocelluloses fiber are some of the disadvantages when using this type of fibers. The weak interaction and adhesion between the fiber and matrix arise due to the hydrophilic nature of the fiber and the hydrophobic characteristic of the polymer. This leads to poor compatibility between the fiber and the matrix, thus resulting in unfavorable properties of the composites.
然而，使用此类纤维时的一些缺点，例如在加工过程中容易形成聚集体、耐湿性差以及木质纤维素纤维中的相互作用和粘附力弱。纤维和基体之间的弱相互作用和粘附是由于纤维的亲水性和聚合物的疏水性而产生的。这导致纤维和基体之间的相容性差，从而导致复合材料的不良性能。
In order to enhance the compatibility between natural fiber and plastic, identification of a suitable compatibilizer is very important to improve the interfacial adhesion, thereby developing an effective interface structure with improved physical and mechanical properties of the composites. Several techniques ranging from chemical treatment, grafting of shortchain molecules and polymers onto the fiber surface by using
为了增强天然纤维与塑料的相容性，确定合适的相容剂对于提高界面附着力非常重要，从而开发出有效的界面结构，改善复合材料的物理和机械性能。多种技术，包括化学处理、将短链分子和聚合物接枝到纤维表面
coupling agents and radical induced adhesion promoters have been reported for improving interfacial bonding [1-3]. As reported [ 4 , 5 ] [ 4 , 5 ] [4,5][4,5], grafting is one of the techniques to improve wetting between the fiber and matrix by promoting interfacial bonding through diffusion of the chain segments of the grafted molecules with the matrix. Coupling agents and radical induced adhesion enhance interfacial bonding by producing covalent bonds between the fiber and the matrix.
据报道，偶联剂和自由基诱导粘附促进剂可改善界面粘合 [1-3]。据报道 [ 4 , 5 ] [ 4 , 5 ] [4,5][4,5] ，接枝是通过接枝分子的链段与基质的扩散来促进界面键合，从而改善纤维和基质之间的润湿性。偶联剂和自由基诱导粘附通过在纤维和基体之间产生共价键来增强界面键。
Maleated coupling agents have always been used in reinforced composite material. Two important functions of maleic anhydride - polyolefin in the composite is to produce economical products and to create good interaction between maleic anhydride (MA) surfaces that link polyolefin with reinforced fiber composites. Keener et al. [4] showed that the addition of 3 % 3 % 3%3 \% maleic anhydride polyethylene (MA-PE) coupling agents in wood composites doubled the tensile strength when compared to the ones without coupling agents. Maleic anhydride grafted to polypropylene (MA-PP) was also reported [5] to show great efficiency in kenaf/polypropylene composite. MA-PP showed polarized interaction and bonded covalently with hydroxyl groups in lignocellulosic fiber. The chemical interactions that occur between the anhydride groups from the coupling agent and the hydroxyl groups of the natural fiber can help to overcome the unfavorable nature of both materials; hence an increase in the tensile and flexural strength results. Majid et al. [6] suggested that the reason for the usage of MA-PE as a compatibilizer in the composite are based on two factors. Firstly is the ability of the anhydride groups from the compatibilizer to undergo an esterification reaction with the hydroxyl groups of natural fiber, and secondly is due to good compatibility between grafted PE chains and the PE phase.
马来酸偶联剂一直用于增强复合材料中。马来酸酐 - 聚烯烃在复合材料中的两个重要功能是生产经济的产品，并在连接聚烯烃和增强纤维复合材料的马来酸酐 （MA） 表面之间产生良好的相互作用。Keener等[4]表明，与没有偶联剂的复合材料相比，在木质复合材料中添加 3 % 3 % 3%3 \% 马来酸酐聚乙烯（MA-PE）偶联剂的拉伸强度增加了一倍。据报道，接枝到聚丙烯上的马来酸酐 （MA-PP） [5] 在洋麻/聚丙烯复合材料中显示出很高的效率。MA-PP 表现出极化相互作用并与木质纤维素纤维中的羟基共价键合。偶联剂的酸酐基团与天然纤维的羟基之间发生的化学相互作用有助于克服这两种材料的不利性质;因此，拉伸强度和弯曲强度增加。Majid等[6]认为，在复合材料中使用MA-PE作为相容剂的原因基于两个因素。首先是由于相容剂中的酸酐基团能够与天然纤维的羟基发生酯化反应，其次是由于接枝的 PE 链与 PE 相之间的良好相容性。
In this research, the investigation on the effects of addition of MA-HDPE on the mechanical and interfacial properties of kenaf fiber/high density polyethylene (HDPE) composites has been done at different percentages of MA-HDPE content. Fourier transformed infrared (FTIR) characterization was used to assign the functional groups of chemical species subjected to the various modifications. Field emission scanning electron microscopy (FESEM) was applied to investigate the morphology of the fracture surface and elucidate the interfacial adhesion between fiber and matrix. The purpose of this work is to prove the usefulness of MA-HDPE through improvement in mechanical properties and interfacial behavior of kenaf fiber reinforced HDPE composites and supported by the FTIR analysis.
在本研究中，在不同百分比的 MA-HDPE 含量下，研究了添加 MA-HDPE 对洋麻纤维/高密度聚乙烯 （HDPE） 复合材料的机械和界面性能的影响。傅里叶变换红外 （FTIR） 表征用于分配受到各种修饰的化学物质的官能团。应用场发射扫描电子显微镜 （FESEM） 研究断裂表面的形貌，阐明纤维与基体之间的界面粘附。这项工作的目的是通过改善洋麻纤维增强 HDPE 复合材料的机械性能和界面行为来证明 MA-HDPE 的有用性，并得到 FTIR 分析的支持。

2. Experimental  2. 实验

2.1. Materials  2.1. 材料

Kenaf bast fiber of 3 mm length with an average density of 134.3 kg / m 3 134.3 kg / m 3 134.3kg//m^(3)134.3 \mathrm{~kg} / \mathrm{m}^{3} was obtained from the National Kenaf &
长3毫米的洋麻韧皮纤维，平均密度从 134.3 kg / m 3 134.3 kg / m 3 134.3kg//m^(3)134.3 \mathrm{~kg} / \mathrm{m}^{3} 国家洋麻和国家用布中获得。
Tobacco Board, Malaysia. It was sieved and fibers with diameter of less than 0.5 mm were collected. A semi-crystalline HDPE, Titanzex HI 1100 with a density of 961 kg / m 3 961 kg / m 3 961kg//m^(3)961 \mathrm{~kg} / \mathrm{m}^{3} and melt flow index of 7 g / 10 min 7 g / 10 min 7g//10min7 \mathrm{~g} / 10 \mathrm{~min}, manufactured by Titan Petchem (M) Sdn. Bhd, Malaysia was used as the matrix. Maleic anhydride grafted high density polyethylene, MAHDPE (NG 1002), with 1 % 1 % 1%1 \% MA graft, density of 880 kg / 880 kg / 880kg//880 \mathrm{~kg} / m 3 m 3 m^(3)\mathrm{m}^{3} and melt flow index 1.5 g / 10 min 1.5 g / 10 min 1.5g//10min1.5 \mathrm{~g} / 10 \mathrm{~min} was manufactured by Shanghai Zeming Plastic Co. Ltd China and used as the compatibilizer. All materials were used as received.
马来西亚烟草局。对其进行筛分并收集直径小于 0.5 mm 的纤维。以密度和 961 kg / m 3 961 kg / m 3 961kg//m^(3)961 \mathrm{~kg} / \mathrm{m}^{3} 熔体流动指数为 7 g / 10 min 7 g / 10 min 7g//10min7 \mathrm{~g} / 10 \mathrm{~min} 密度的半结晶高密度聚乙烯 Titanzex HI 1100 作为基体，由马来西亚 Titan Petchem （M） Sdn. Bhd 制造。马来酸酐接枝高密度聚乙烯 MAHDPE （NG 1002），具有 1 % 1 % 1%1 \% MA 接枝、密度 880 kg / 880 kg / 880kg//880 \mathrm{~kg} / m 3 m 3 m^(3)\mathrm{m}^{3} 和熔体流动指数 1.5 g / 10 min 1.5 g / 10 min 1.5g//10min1.5 \mathrm{~g} / 10 \mathrm{~min} ，由中国上海泽明塑料有限公司制造，用作增容剂。所有材料均按收到时使用。

2.2. Extrusion  2.2. 挤出

Kenaf fiber/HDPE composites were prepared by meltcompounding using a co-rotating twin screw extruder with gravimetric metering device feeder (Brabender KETSE 20/40 Lab Compounder, Germany). The screw has a diameter of 20 mm and aspect ratio of 40 . Extrusion was carried out at screw speeds of 80 rpm at 2 kg / h 2 kg / h 2kg//h2 \mathrm{~kg} / \mathrm{h} feeding rate with temperature settings of 165 ∘ C , 170 ∘ C , 175 ∘ C , 180 ∘ C 165 ∘ C , 170 ∘ C , 175 ∘ C , 180 ∘ C 165^(@)C,170^(@)C,175^(@)C,180^(@)C165^{\circ} \mathrm{C}, 170{ }^{\circ} \mathrm{C}, 175^{\circ} \mathrm{C}, 180^{\circ} \mathrm{C} and 185 ∘ C 185 ∘ C 185^(@)C185^{\circ} \mathrm{C} from the hopper to the die. Pure HDPE and MA-HDPE were loaded into the feed hopper by using gravimetric metering device while kenaf fiber was introduced to the barrel at the side feeder between zones 3 and 4 . The strands leaving the circular extruder die with diameter of 3 mm were pelletized. The pelletized composites were then oven-dried at 80 ∘ C 80 ∘ C 80^(@)C80^{\circ} \mathrm{C} for 24 h and stored in a sealed plastic bag inside desiccator for injection molding. Composites were prepared at two different fiber compositions of 8.5 wt . % 8.5 wt . % 8.5wt.%8.5 \mathrm{wt} . \% and 17.5 wt . % 17.5 wt . % 17.5wt.%17.5 \mathrm{wt} . \% and the MA-HDPE compatibilizer was added at different loadings of 0 % , 4 % 0 % , 4 % 0%,4%0 \%, 4 \%, 8 % 8 % 8%8 \% and 12 % 12 % 12%12 \% of the total weight of the composites.
使用带有重量计量装置喂料机（Brabender KETSE 20/40 Lab Compounder，德国）的同向旋转双螺杆挤出机通过熔融复合制备洋麻纤维/HDPE 复合材料。螺钉的直径为 20 毫米，纵横比为 40。挤出以 80 rpm 的 2 kg / h 2 kg / h 2kg//h2 \mathrm{~kg} / \mathrm{h} 螺杆速度以进料速率进行，温度设置为料斗 165 ∘ C , 170 ∘ C , 175 ∘ C , 180 ∘ C 165 ∘ C , 170 ∘ C , 175 ∘ C , 180 ∘ C 165^(@)C,170^(@)C,175^(@)C,180^(@)C165^{\circ} \mathrm{C}, 170{ }^{\circ} \mathrm{C}, 175^{\circ} \mathrm{C}, 180^{\circ} \mathrm{C} 和 185 ∘ C 185 ∘ C 185^(@)C185^{\circ} \mathrm{C} 从料斗到模具。使用重量计量装置将纯 HDPE 和 MA-HDPE 装入进料斗，同时将洋麻纤维引入 3 区和 4 区之间侧喂料机的桶中。离开直径为 3 mm 的圆形挤出机模具的拉条被造粒。然后将造粒复合材料烘箱干燥 80 ∘ C 80 ∘ C 80^(@)C80^{\circ} \mathrm{C} 24 小时，并储存在干燥器内的密封塑料袋中用于注塑成型。制备了 8.5 wt . % 8.5 wt . % 8.5wt.%8.5 \mathrm{wt} . \% 和 两种 17.5 wt . % 17.5 wt . % 17.5wt.%17.5 \mathrm{wt} . \% 不同纤维成分的复合材料，并在复合材料总重量的不同载荷 0 % , 4 % 0 % , 4 % 0%,4%0 \%, 4 \% 8 % 8 % 8%8 \% 12 % 12 % 12%12 \% 下添加了 MA-HDPE 增容剂。

2.3. Injection molding  2.3. 注塑成型

The dried pelletized composites were then injection molded with a single gated, four cavities mold for tensile test specimens using injection molding machine (Boy ® 55 M ® 55 M ^(®)55M{ }^{\circledR} 55 \mathrm{M}, Germany). The barrel was set at temperatures between 160 ∘ C 160 ∘ C 160^(@)C160{ }^{\circ} \mathrm{C} 190 ∘ C 190 ∘ C 190^(@)C190{ }^{\circ} \mathrm{C}, an injection pressure of 100 bar − 120 bar 100 bar − 120 bar 100bar-120bar100 \mathrm{bar}-120 \mathrm{bar}, cooling time of 120 s and mold temperature of 20 ∘ C 20 ∘ C 20^(@)C20^{\circ} \mathrm{C}.
然后使用注塑机（德国 Boy ® 55 M ® 55 M ^(®)55M{ }^{\circledR} 55 \mathrm{M} ）用单门、四腔模具对干燥的造粒复合材料进行注塑成型，用于拉伸试样。将料筒设置在 、注射压力 、 100 bar − 120 bar 100 bar − 120 bar 100bar-120bar100 \mathrm{bar}-120 \mathrm{bar} 冷却时间为 120 秒和模具温度 20 ∘ C 20 ∘ C 20^(@)C20^{\circ} \mathrm{C} 之间 160 ∘ C 160 ∘ C 160^(@)C160{ }^{\circ} \mathrm{C} 190 ∘ C 190 ∘ C 190^(@)C190{ }^{\circ} \mathrm{C} 。

2.4. Determination of the functional group of composites
2.4. 复合材料官能团的测定

Infrared absorption spectra of the uncompatibilized and compatibilized kenaf fiber composites were recorded using a fourier transform infrared, FTIR, spectrophotometer (PerkinElmer-Spotlight 400, USA) combined with a universal attenuated total reflectance, ATR accessory at a resolution of 4 cm − 1 4 cm − 1 4cm^(-1)4 \mathrm{~cm}^{-1} with 64 sample scans for each spectrum in the wavelength of 4000 − 500 cm − 1 4000 − 500 cm − 1 4000-500cm^(-1)4000-500 \mathrm{~cm}^{-1}.
使用傅里叶变换红外、FTIR、分光光度计（PerkinElmer-Spotlight 400，美国）结合通用衰减全反射、ATR 附件 4 cm − 1 4 cm − 1 4cm^(-1)4 \mathrm{~cm}^{-1} 以 64 个样品扫描波长记录不相容和相容洋麻纤维复合材料的红外吸收光谱 4000 − 500 cm − 1 4000 − 500 cm − 1 4000-500cm^(-1)4000-500 \mathrm{~cm}^{-1} 。

2.5. Determination of the tensile properties
2.5. 拉伸性能的测定

Tensile tests were conducted according to ASTM D-638 using a universal testing machine (Instron 5569, USA) equipped with a load-cell of 50 kN at a constant cross-head speed of 5 mm / min 5 mm / min 5mm//min5 \mathrm{~mm} / \mathrm{min}, and a gauge length of 50 mm . For each test, a minimum of seven samples were tested and an average of at least five reproducible results were presented. The test was conducted under ambient conditions.
根据 ASTM D-638 使用配备 50 kN 称重传感器的万能试验机（Instron 5569，美国）以恒定的横头速度和 5 mm / min 5 mm / min 5mm//min5 \mathrm{~mm} / \mathrm{min} 50 mm 的标距长度进行拉伸试验。对于每项测试，至少测试了 7 个样品，平均提供了至少 5 个可重复的结果。测试是在环境条件下进行的。

2.6. Determination of the flexural properties
2.6. 弯曲性能的测定

A universal testing machine (Instron 5569, USA) was used to perform the flexural test under ambient condition. Three point bending flexural tests were set up according to ASTM D-790. Specimen support span, L, was fixed at 50 mm with maximum deflections of 30 mm and constant cross-head speed of 1.27 mm / min 1.27 mm / min 1.27mm//min1.27 \mathrm{~mm} / \mathrm{min}. For each test, a minimum of seven samples were tested and an average of at least five reproducible results were presented.
使用万能试验机（Instron 5569，美国）在环境条件下进行弯曲试验。根据 ASTM D-790 设置三点弯曲弯曲试验。试样支撑跨度 L 固定在 50 mm，最大挠度为 30 mm，恒定横头速度为 1.27 mm / min 1.27 mm / min 1.27mm//min1.27 \mathrm{~mm} / \mathrm{min} 。对于每项测试，至少测试了 7 个样品，平均提供了至少 5 个可重复的结果。

2.7. Fracture surface observation
2.7. 裂缝表面观察

The fractured surface of the tensile specimens was observed using the field emission scanning electron microscope, FESEM (Zeiss-Auriga,39-22, Germany) under an acceleration voltage of 1 kV . The non-coated samples were mounted on the aluminium sample holder and placed in the specimen chamber in a vacuum condition of 0.06 mbar at room temperature. Digital images were taken from the fractured surfaces of the tensile test samples at a magnification of 100 × , 500 × 100 × , 500 × 100 xx,500 xx100 \times, 500 \times and 1000 × 1000 × 1000 xx1000 \times.
在 1 kV 的加速电压下，使用场发射扫描电子显微镜 FESEM （Zeiss-Auriga，39-22， Germany） 观察拉伸试样的断裂表面。将无涂层样品安装在铝制样品架上，并在室温下以 0.06 mbar 的真空条件放置在样品室中。从拉伸试验样品的断裂表面以放大倍数 100 × , 500 × 100 × , 500 × 100 xx,500 xx100 \times, 500 \times 和 1000 × 1000 × 1000 xx1000 \times 拍摄数字图像。

3. Results and Discussion
3. 结果与讨论

3.1 FTIR

FTIR spectra of pure HDPE and compatibilizer (MA-HDPE), are shown in Fig. 1. MA-HDPE showed the appearance of symmetric stretching of carbonyl absorption at 1712 cm − 1 1712 cm − 1 1712cm^(-1)1712 \mathrm{~cm}^{-1} and 1791 cm − 1 1791 cm − 1 1791cm^(-1)1791 \mathrm{~cm}^{-1}. The appearance of a small peak at 1791 cm − 1 1791 cm − 1 1791cm^(-1)1791 \mathrm{~cm}^{-1} is associated with the presence of C = O C = O C=O\mathrm{C}=\mathrm{O} of 1 % 1 % 1%1 \% anhydride functional group grafted onto the HDPE. However, this peak was not observed in the pure HDPE spectrum. Previous researchers observed the two absorbances near 1774 cm − 1 1774 cm − 1 1774cm^(-1)1774 \mathrm{~cm}^{-1} and 1790 cm − 1 1790 cm − 1 1790cm^(-1)1790 \mathrm{~cm}^{-1}, and these were attributed to MA symmetric C = O C = O C=O\mathrm{C}=\mathrm{O} stretching of MA-PP and MA-PE, respectively [7-9].
纯 HDPE 和相容剂 （MA-HDPE） 的 FTIR 光谱如图 1 所示。MA-HDPE 在 和 1791 cm − 1 1791 cm − 1 1791cm^(-1)1791 \mathrm{~cm}^{-1} 处 1712 cm − 1 1712 cm − 1 1712cm^(-1)1712 \mathrm{~cm}^{-1} 表现出羰基吸收的对称拉伸外观。小峰的出现 1791 cm − 1 1791 cm − 1 1791cm^(-1)1791 \mathrm{~cm}^{-1} 与 C = O C = O C=O\mathrm{C}=\mathrm{O} 接枝到 HDPE 上的 1 % 1 % 1%1 \% 酸酐官能团的存在有关。然而，在纯 HDPE 光谱中未观察到该峰。以前的研究人员观察到 和 1790 cm − 1 1790 cm − 1 1790cm^(-1)1790 \mathrm{~cm}^{-1} 附近的 1774 cm − 1 1774 cm − 1 1774cm^(-1)1774 \mathrm{~cm}^{-1} 两个吸光度，它们分别归因于 MA-PP 和 MA-PE 的 MA 对称 C = O C = O C=O\mathrm{C}=\mathrm{O} 拉伸 [7-9]。
Figures 2 and 3 shows two key features of the FTIR spectra of uncompatibilized and compatibilized composites at 8.5 wt . % 8.5 wt . % 8.5wt.%8.5 \mathrm{wt} . \% and 17.5 wt . % 17.5 wt . % 17.5wt.%17.5 \mathrm{wt} . \% fiber loadings, respectively. The peak in the range of 3700 cm − 1 3700 cm − 1 3700cm^(-1)3700 \mathrm{~cm}^{-1} to 3100 cm − 1 3100 cm − 1 3100cm^(-1)3100 \mathrm{~cm}^{-1} indicates the presence of hydroxyl group and the peak in the range of 1800 cm − 1 1800 cm − 1 1800cm^(-1)1800 \mathrm{~cm}^{-1} to 1680 cm − 1 1680 cm − 1 1680cm^(-1)1680 \mathrm{~cm}^{-1} indicates the presence of carbonyl groups. From
图 2 和图 3 分别显示了在 17.5 wt . % 17.5 wt . % 17.5wt.%17.5 \mathrm{wt} . \% 纤维负载和纤维负载下 8.5 wt . % 8.5 wt . % 8.5wt.%8.5 \mathrm{wt} . \% 不相容和相容复合材料的 FTIR 光谱的两个关键特征。 3700 cm − 1 3700 cm − 1 3700cm^(-1)3700 \mathrm{~cm}^{-1} to 3100 cm − 1 3100 cm − 1 3100cm^(-1)3100 \mathrm{~cm}^{-1} 范围内的峰表示存在羟基， 1800 cm − 1 1800 cm − 1 1800cm^(-1)1800 \mathrm{~cm}^{-1} to 1680 cm − 1 1680 cm − 1 1680cm^(-1)1680 \mathrm{~cm}^{-1} 范围内的峰表示存在羰基。从
Fig. 2, the appearance of symmetric stretching of carbonyl absorption of MA-HDPE at 1712 cm − 1 1712 cm − 1 1712cm^(-1)1712 \mathrm{~cm}^{-1} shifted to the range of 1725 cm − 1 − 1742 cm − 1 1725 cm − 1 − 1742 cm − 1 1725cm^(-1)-1742cm^(-1)1725 \mathrm{~cm}^{-1}-1742 \mathrm{~cm}^{-1} and disappearance of peaks at 1791 cm − 1 1791 cm − 1 1791cm^(-1)1791 \mathrm{~cm}^{-1} was observed in the case of compatibilized composites. This new appearance of the ester carbonyl groups shows that there could be interfacial bonding between the kenaf and matrix via the MA-HDPE. It was also observed that the new ester carbonyl groups peaks around 1725 cm − 1 1725 cm − 1 1725cm^(-1)1725 \mathrm{~cm}^{-1} 1742 cm − 1 1742 cm − 1 1742cm^(-1)1742 \mathrm{~cm}^{-1} shifted with the addition of compatibilizer from 4 % 4 % 4%4 \% to 12 % 12 % 12%12 \% into the system, with the highest peak intensity obtained at 12 % 12 % 12%12 \% compatibilizer content.
图 2，在相容复合材料的情况下，观察到 MA-HDPE 的羰基吸收在 1712 cm − 1 1712 cm − 1 1712cm^(-1)1712 \mathrm{~cm}^{-1} 偏移到范围时出现对称拉伸 1725 cm − 1 − 1742 cm − 1 1725 cm − 1 − 1742 cm − 1 1725cm^(-1)-1742cm^(-1)1725 \mathrm{~cm}^{-1}-1742 \mathrm{~cm}^{-1} ，并在 处 1791 cm − 1 1791 cm − 1 1791cm^(-1)1791 \mathrm{~cm}^{-1} 观察到峰消失。酯羰基的这种新外观表明，洋麻和基体之间可以通过 MA-HDPE 进行界面键合。还观察到，随着增容剂的加入，新的酯羰基峰 1725 cm − 1 1725 cm − 1 1725cm^(-1)1725 \mathrm{~cm}^{-1} 1742 cm − 1 1742 cm − 1 1742cm^(-1)1742 \mathrm{~cm}^{-1} 周围从 4 % 4 % 4%4 \% 到 12 % 12 % 12%12 \% 添加到 系统中，在增容剂含量下 12 % 12 % 12%12 \% 获得最高峰强度。
Broad absorption bands of hydroxyl ( -OH ) stretching are present in both uncompatibilized and compatibilized composites. Figure 2 shows that the hydroxyl peak of uncompatibilized composites is at 3345 cm − 1 3345 cm − 1 3345cm^(-1)3345 \mathrm{~cm}^{-1}. After the addition of compatibilizer, only 8 % 8 % 8%8 \% compatibilizer loading presented a shift in the hydroxyl peak to a higher wavelength with the highest peak intensity when compared to the other compatibilizer loadings. It is possible esterification reaction may have taken place and resulted in two products; one is the copolymer with diester structures and the other is the copolymer with half ester structure and half carboxylic structure [10]. The formation of half carboxylic structure after esterification reaction can give rise to intramolecular hydrogen bonding between hydrogen atoms of a hydroxyl group from kenaf fiber with the oxygen atom of a MA-HDPE from compatibilizer. This could also be the reason for the highest performance of 8 % 8 % 8%8 \% compatibilizer at 8.5 wt . % 8.5 wt . % 8.5wt.%8.5 \mathrm{wt} . \% fiber loading.
羟基 （-OH） 拉伸的宽吸收带存在于不相容和相容复合材料中。图 2 显示，不相容复合材料的羟基峰为 3345 cm − 1 3345 cm − 1 3345cm^(-1)3345 \mathrm{~cm}^{-1} 。添加相容剂后，与其他相容剂上样量相比，只有 8 % 8 % 8%8 \% 相容剂上样物的羟基峰向具有最高峰强度的更高波长偏移。可能发生了酯化反应并产生两种产物;一种是具有二酯结构的共聚物，另一种是具有半酯结构和半羧基结构的共聚物 [10]。酯化反应后形成半羧基结构可导致洋麻纤维的羟基氢原子与增容剂的 MA-HDPE 氧原子之间产生分子内氢键。这也可能是 8 % 8 % 8%8 \% 增容剂在纤维负载下 8.5 wt . % 8.5 wt . % 8.5wt.%8.5 \mathrm{wt} . \% 具有最高性能的原因。
Figure 3 shows that there were no appearances of ester group peaks in the uncompatibilized composites. However, with the addition of compatibilizer, the ester group peaks were observable at 1737 cm − 1 1737 cm − 1 1737cm^(-1)1737 \mathrm{~cm}^{-1} ( 4 % 4 % 4%4 \% MA-HDPE) and 1728 cm − 1 1728 cm − 1 1728cm^(-1)1728 \mathrm{~cm}^{-1} ( 8 % 8 % 8%8 \% and 12 % 12 % 12%12 \% MA-HDPE) where the peak intensity increased with increasing amount of MA-HDPE. These ester group peaks were also found to have shifted to the higher wavelength compared to the appearance of symmetric stretching of carbonyl absorption of MA-HDPE at 1712 cm − 1 1712 cm − 1 1712cm^(-1)1712 \mathrm{~cm}^{-1}. From Fig. 3, uncompatibilized composites showed the presence of hydroxyl group at 3373 cm − 1 3373 cm − 1 3373cm^(-1)3373 \mathrm{~cm}^{-1} due to the hydroxyl compound from the kenaf fiber. The peak of the hydroxyl group of all compatibilized composites shifted to lower wavelength (around 3345 cm − 1 3345 cm − 1 3345cm^(-1)3345 \mathrm{~cm}^{-1} ) with the addition of compatibilizer when compared to the uncompatibilized composites. Similar to the finding above, the addition of 8 % 8 % 8%8 \% compatibilizer loading showed the highest peak intensity of hydroxyl group at 3327 cm − 1 3327 cm − 1 3327cm^(-1)3327 \mathrm{~cm}^{-1} suggesting that this percentage of compatibilizer loading gave the most effective esterification and intramolecular hydrogen bonding reaction inside the compatibilized system. At higher percentage fiber loading of 17.5 wt . % 17.5 wt . % 17.5wt.%17.5 \mathrm{wt} . \%, the peak intensity of hydroxyl groups for compatibilized composites was much higher compared to the uncompatibilized composites. This was due to higher amounts of fibers contributing to higher existence of hydroxyl groups.
图 3 显示，在未相容的复合材料中没有出现酯基峰。然而，随着增容剂的加入，在 （ 4 % 4 % 4%4 \% MA-HDPE） 和 1728 cm − 1 1728 cm − 1 1728cm^(-1)1728 \mathrm{~cm}^{-1} （ 8 % 8 % 8%8 \% 和 12 % 12 % 12%12 \% MA-HDPE） 处 1737 cm − 1 1737 cm − 1 1737cm^(-1)1737 \mathrm{~cm}^{-1} 可以观察到酯基峰，其中峰强度随着 MA-HDPE 量的增加而增加。还发现这些酯基峰与 MA-HDPE 的羰基吸收对称拉伸的出现相比已经转移到更高的波长 1712 cm − 1 1712 cm − 1 1712cm^(-1)1712 \mathrm{~cm}^{-1} 。从图 3 中，由于洋麻纤维中的羟基化合物，未相容的复合材料显示出羟基 3373 cm − 1 3373 cm − 1 3373cm^(-1)3373 \mathrm{~cm}^{-1} 的存在。与未相容复合材料相比，添加相容剂后，所有相容复合材料的羟基峰都向较低的波长（周围 3345 cm − 1 3345 cm − 1 3345cm^(-1)3345 \mathrm{~cm}^{-1} ）移动。与上述发现类似，添加 8 % 8 % 8%8 \% 相容剂负载显示出羟基的最高峰强度， 3327 cm − 1 3327 cm − 1 3327cm^(-1)3327 \mathrm{~cm}^{-1} 表明该百分比的相容剂负载在相容系统内产生了最有效的酯化和分子内氢键反应。在较高的纤维负载百分比下 17.5 wt . % 17.5 wt . % 17.5wt.%17.5 \mathrm{wt} . \% ，相容复合材料的羟基峰强度远高于不相容复合材料。这是由于较多的纤维导致羟基的存在更高。
  1. F. M. Salleh • A. Hassan ( ⊠ ) ⋅ ( ⊠ ) ⋅ (⊠)*(\boxtimes) \cdot R. Yahya • A. D. Azzahari
    F. M. 萨利 • A. 哈桑 ( ⊠ ) ⋅ ( ⊠ ) ⋅ (⊠)*(\boxtimes) \cdot R. 叶海亚 • A. D. Azzahari
    Polymer and Composite Materials Research Laboratory, Department of Chemistry, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia
    马来亚大学理学院化学系聚合物和复合材料研究实验室，马来西亚吉隆坡 50603
    e-mail: ahassan@um.edu.my
    电子邮件： ahassan@um.edu.my
    R. A. Lafia-Araga  RA Lafia-Araga
    Department of Chemistry, School of Natural and Applied Sciences, Federal University of Technology, 920001 Minna, Nigeria
    尼日利亚 920001 Minna 联邦技术大学自然与应用科学学院化学系
    M. N. Z. M. Nazir
    M. N. Z. M. 纳齐尔
    Central Service Unit (Laboratory), Dean’s Office, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia
    马来亚大学工程学院院长办公室中央服务单位（实验室），马来西亚吉隆坡 50603