翻译定稿

Easy estimation估计 of the progress of artificial Weathering风化侵蚀 of palm棕榈fiber-polypropylene composites by chemiluminescence化学发光

Date palm leaves were compounded with polypropylene (PP) and UV stabilizers安定装置稳定器 to form composite materials. Residual剩余的 thermo-oxidation

stability of such composites undergone to accelerated 加速的weathering in Xenotest has been investigated by chemiluminescence method.It has been found that

composites are much more stable 稳定的than PP alone which wasattributed to the direct interaction 交互作用of cellulose纤维素 fibres (reinforcing effect) and lignin木质素(anti-oxidation 抗氧化effect) with polypropylene peroxyl过氧化氢 radicals. Samples in which polypropylene is compatibilized with cellulose by Epolene E-43 wax are generally less stable than uncompatibilized ones probably because of the pro-initiation正面的开始effect of cellulose on polypropylene oxidation. 1. Introduction

Since 1990 one can register记录登记 an increasing interest in the development of industrial and consumer products that combine联合 lignocellulosic fibers and

plastics. The primary 主要的impetus推动力 has come from one of these goals:目标 1. To reduce material costs by combining a lower cost material acting as担当 filler or extender with a higher cost material.2. To develop products that can utilize利用recycled再循环materials.3. To produce a composite material that exhibits展示 specific properties that are superior compared to either ofthe component 成分materials alone (e.g. increased strength to weight ratio, improved abrasion resistance, etc.) The processing temperature of thermoplastics热塑性塑料 withcellulosic fibers is limited due to the cellulose degradation降解at higher temperatures. However, it has been reported that no deterioration变坏退化of properties of composite materials containing cellulose was observed观察when processing temperatures are maintained维持below 200.C The composites of cellulose fibers with thermoplastics can withstand抵挡higher stresses压力than either their individual constituent要素because the fibers and matrix interact and redistribute重新分布the stresses. The ability of these two constituents to exchange stresses depends critically主要的on the effectiveness效力of the coupling耦合or

bonding黏结between fiber and matrix [6]. It is well known that compatibility兼容性between lignocellulosic materials and the polymer matrix plays a crucial只管紧要的role in determining the properties of a composite. Lignocellulosic materials,which have polar极性hydroxyl groups on the surface, have difficulty in forming well

bonded interfaces界面with nonpolar polymer matrix materials such as polyethylene and polypropylene. Various各种各样的chemical reagents试剂 have been employed to enhance the compatibility between the constituent materials. These include Epolene E-43 (Maleic anhydride modified polypropylene) [2,7, 8, 11–13], poly[methylene(polyphenyl isocyanate)](PMPPIC), γ

-methacryloxypropyltrimethoxysilane,poly(propylene acrylic acid) and

poly(propyleneethylene acrylic acid) [7], etc. From the practical viewpoint, the resistance抵抗力of the above materials towards thermo-oxidation should be of

interest重要性 影响as it determines the remaining保留service life of the material. Until now very few studies investigating the artificial weathering of

polypropylene/cellulose fiber composites exist. On the other hand, the antioxidant抗氧化剂properties of lignin木质素in polypropylene were reported several times [14–16]. The authors underline the necessity of compatibilization of lignin with polypropylene to explore the maximum of its antioxidant properties due to hydroxyl groups involved in monomer unit.

Objective目的of this report is to show how the extent程度范围 of stabilization of polypropylene/date palm cellulose fiber composites changes with the time of exposition暴光of sample to artificial ageing. The chemiluminescence method has been used for an easy characterization of the remaining thermo-oxidation

stability.The thermal oxidation of polypropylene alone was Examined调查by this method many times and the agreement between induction time\\诱导时间so

determined and those determined by other methodswas several times reported. The method itself is typical with extreme极度的sensitivity敏感but the

chemiluminescence behavior of polymers may differ each from the other. There are polymers, polypropylene including, which give typical sigmoidal S形的autocatalytic自身催化的 increase of the light emission光发射under isothermal等温的

conditions条件which coincides with与..相符the oxidation runs融化的determined by other methods.On the other hand, cellulose has a relatively short length of kinetic oxidation chains and does not give an autocatalytic自身催化的shape of

chemiluminescence runs. Intensity强度of the light emission of oxidized cellulose decays衰退steadily有规则的稳定的from the initial最初的level. Different authors indicate that the elementary初步的基本的 processes from the oxidation mechanism which might be responsible for the light emission are not quite clear but the

predominating 占优势opinions favor the recombination再结合of peroxyl过氧化氢radicals which proceeds according to Russel’s scheme.In the Equation 1 asterix denotes显示the excited singlet state of oxygen and excited triplet三重态state of carbonyl羰基 groups on the polymer chain, respectively. The light comes from the transfer of these excited particles粒子极少量to their ground states. Together with this emissive发射的route路程路线 of deactivation钝化惰性化of excited states there occur发生quenching淬火processes. Non-emissive way of transfer of excited into ground state may be much more significant and may modulate调整调节the proportionality constant比例常数 in linear

relation线性关系between chemiluminescence intensity强度 I and the rate of oxidation氧化.I = _ · rate of oxidation (2)

2. Experimental2.1. Materials Polypropylene used in the study was supplied by Saudi Basic Industries Corporation (SABIC). The brand name商标for it is LADENE PP570P. It is a homopolymer均聚物used for producing rigid刚性的injection molded注模articles商品. Details of the polymer are given in Table I. Maleated 马来酸盐的polypropylene was used as a compatibilizer and was supplied by Eastman Chemicals Two stabilizers稳定器Irgastab and Tinuvin-783

were used to stabilize the composites for thermal and UV degradation降解during processing and weathering. Polypropylene wax was added to facilitate促进推动the injection molding喷射摸塑法of the composites. The formulations明确的表达used in preparation预备of composites are shown in 2.2. Fiber preparation

Branches分支obtained获得 from palm trees were cut into pieces about 6 inch long. Thereafter,随后they were air dried风干for 48 h at room temperature. The pieces of branches were then granulated颗粒状的to a small size using a Granulator造粒机The fibers were then size依大小排列separated分开by using sieving筛分machine. Only the large fraction片断of fibers was used in this study. The fibers size distribution was characterized

using a digital vernier caliper.数字的游标卡尺 The average length of the fibers was 4.7 mm with a standard deviation标准偏差of 1.7 mm and an aspect ratio纵横比 of 10.8. The fibers obtained were then cleaned to remove the volatile organic compounds.有机挥发性化合物The chemicals化学药品 used for cleaning were

Ethanol乙醇 and Toluene甲苯in the ratio比率 of (1:2) (V/V). The mixture of these two chemicals was prepared in a large container.容器 The fibers were soaked in吸收the mixture for 24 h.

The fibers were then washed with water and dried in a vacuum oven真空电炉at 105.C for 24 h to remove residual moisture.残留水分 2.3. Compounding混合 and molding成型

The composite components were compounded using a Brabender Measuring Head, Model S-650, No:G126 mounted with安放a single screw extruder.螺杆挤压机 The fibers were hand mixed with和..混合 polypropylene and other additives添加剂prior to在前compounding. In both cases the fibers and

the resins were first hand mixed in a bowl and then transferred to转 the

mixer/extruder.搅拌器挤压机The conditions of mixing were varied in such a way to determine the optimum conditions最佳条件that will produce samples with

maximum最大量最大限度dispersion散布of fibers, good mechanical properties, good color and smell. The mixed compositesobtained

from the extruder were granulated颗粒状的 then molded浇铸using an injection molding machine 注模机at 200.C. The composite specimen样品were molded into standard ASTM (American Society of Testing Materials, 美国材料实验协会)D-648–94B specimen, which were then weathered and characterized. 2.4. Weathering trials试验

The complete details详细资料of the trials may be seen below: Equipment used: Xenotest Beta-LM Total duration of exposure:暴露时间2000 h

Parameters参数of Xenotest Beta-LM Irradiance:发光45 w/m2 between 300–400 nm Black panel temp. (BPT): 63. ± 3.C Black sensor temp. (BST): 70. ± 3.C Humidity:湿度50 5%

2.5. Characterization of aged samples

The composite materials exposed to使易受artificial weathering trials were