<Emphasis Type="BoldItalic">In-situ</Emphasis> microfibrillar PP–PA6 composites: rheological,morphological and mechanical properties

In this study, the rheology, morphology and mechanical properties of microfibrillar composites based on polypropylene reinforced with polyamide 6 (PA6) fibres have been investigated. Influence of different factors such as the PA6 composition and drawing ratio on the output of the extruder, and the compatibilizer composition on the properties of these composites, were investigated. The results of rheometric mechanical spectrometer rheological measurements and melt flow index (MFI) showed that the storage modulus, loss modulus and complex viscosity of the microfibrillar composites are directly related to the composition of PA6. It was also shown that the presence of compatibilizer was the main factor that led to decrease of some properties including the storage modulus, loss modulus and complex viscosity and increase in the MFI. The results of mechanical tests on samples prepared with different drawing ratios showed that by increasing the drawing ratio from 3 to 5, the mechanical properties increase, while increasing draw ratio from 5 to 8 reduces the mechanical properties. With the increase in the composition of the polyamide phase, the tensile strength of microfibrillar composite compatible with polypropylene-grafted-maleic anhydride initially increased; however, the tensile strength decreased with a high composition of polyamide phase. Scanning electron microscope images also revealed that the presence of the compatibilizer in the microfibrillar composites leads to decrease in the number of undeformed drops, while it reduces the micro-fibres diameter, which greatly improved the final properties of the composites.     

特殊形态结构导电高分子复合材料的电学性能

先使聚丙烯接枝马来酸酐(PP-g-MAH)与炭黑(CB)反应,再与聚丙烯/尼龙6(PP/PA6)共混制备出CB位于两相界面处的PP/PA6/PP-g-MAH/CB导电高分子复合材料,研究了材料的特殊结构和电学性能。结果表明,在PP/PA6/CB体系中CB粒子分布在PA6相,体系的逾渗阈值为2%;而在PP/PA6/PP-g-MAH/CB体系中,CB被PP-g-MAH诱导分布在两相界面处。PP/PA6两相为海岛结构时,PP/PA6/PP-g-MAH/CB体系仍可导电。PP/PA6/PP-g-MAH/CB体系的逾渗阈值降至1.6%,低于PP/PA6/CB体系。体系的正温度效应(PTC)强度远高于PP/PA6/CB体系,在90-135℃范围内不出现负温度效应(NTC)。PP/PA6/PP-g-MAH/CB体系的电学性能归结于其特殊的界面形态结构:导电通道由位于共混物界面处的PP-g-MAH和CB构建而成。     

Mechanical properties of wood–fiber reinforced polypropylene composites: Effect of a novel compatibilizer with isocyanate functional group

Natural fibers are increasingly being used as reinforcement in commercial thermoplastics due to their low cost, high specific properties and renewable nature. While the maleic anhydride modified polypropylene (MAPP) is most commonly used as compatibilizer to improve interfacial adhesion between hydrophilic wood–fibers and hydrophobic polypropylene, in this study, a novel compatibilizer (m-TMI-g-PP) with isocyanate functional group was synthesized by grafting m-isopropenyl-α,α-dimethylbenzyl-isocyanate (m-TMI) onto isotactic polypropylene (PP) in a twin screw extruder. The effect of filler concentration on the mechanical properties of wood–fiber filled composites, prepared by using m-TMI-g-PP as the compatibilizer, was investigated. The addition of the compatibilizer resulted in greater reinforcement of composites, as indicated by the improvement in mechanical properties. Tensile strength of composites so prepared increased by almost 45%, whereas 85% increase in flexural properties was observed. However the addition of wood–fibers resulted in a decrease in elongation at break and impact strength of the composites.     

In situ microfibrillar morphology and properties of polypropylene/polyamide/carbon black composites prepared through multistage stretching extrusion

Isotactic polypropylene/polyamide/carbon black (PP/PA/CB) composites with microfibrillar morphology were designed and prepared using a multistage stretching extruder with an assembly of laminating-multiplying elements (LMEs). CB was selectively located in PA. With the increase of LME number from zero to seven, the conductive PA/CB phase was found to experience an elongating-breaking-elongating process. This morphological development resulted in the strong dependence of electrical resistivity on the LME number. When no LME was used, PP/PA/CB materials with 2.0, 3.0, or 4.0 wt% (1.0, 1.6, and 2.1 vol%) CB employed were insulators (resistivity: 10¹⁰ Ω cm) due to their droplet morphology. With the introduction of LMEs, a conductive network was formed because of the microfibrillation of the conductive PA/CB phase; these materials became conductors (resistivity: 10⁴–10⁶ Ω cm). The percolation threshold can lower to 1.5 wt% (0.9 vol%). The low resisticity and percolation threshold cannot be obtained through the conventional method.     

多级拉伸PP/PA1010/CB导电复合材料的结构与性能

利用自主设计的多级拉伸挤出设备,制备了含不同长径比的聚酰胺/炭黑（PA1010/CB）纤维的原位微纤聚丙烯/聚酰胺/炭黑（PP/PA1010/CB）导电复合材料,炭黑仅选择性分散在PA1010中,形成一种特殊的双逾渗现象。扫描电子显微镜观察、电学性能测试结果表明,随着分割叠加单元个数的增加,（PA1010＋CB）导电相...     

PP-g-Si与KH550对聚丙烯/滑石粉体系的增容效果

硅烷接枝聚丙烯（ＰＰ－ｇ－Ｓｉ）对聚丙烯／滑石粉（ＰＰ／Ｔａ）混合体系有一定的增容作用,可使复合材料的力学性能得以提高,占复合材料总质量３．５％的ＰＰ－ｇ－Ｓｉ（相当于含硅烷０．２％）对ＰＰ／Ｔａ体系的增容效果与含０．８％（质量分数）的ＫＨ５５０的增容效果相当,ＫＨ５５０对复合材料中聚丙烯（ＰＰ）的结晶熔融行为基本上无影响。而ＰＰ－ｇ－Ｓｉ能进一步使材料中ＰＰ的结晶峰温和熔融峰温提高。     

Morphology and electrical properties of polyamide 6/polypropylene/multi-walled carbon nanotubes composites

Morphology, electrical properties and conductive mechanisms of polyamide 6/polypropylene/muti-walled carbon nanotubes (PA6/PP/MWNTs) composites with varied compositions and different blending sequences were investigated. The MWNTs were found to be located preferentially in the PA6 phase in the composites, whatever the PA6 was continuous or dispersed phase. While the incorporation of MWNTs changed the dispersed PA6 phase from spherical to elongated or irregular shape. The PA6/PP/MWNTs (20/80/4) composite with a dispersed PA6 phase exhibited a higher electrical conductivity in comparison with the PA6/PP/MWNTs (50/50/4) composite which has a co-continuous phase and exhibits double percolation. This was due to the formation of a conductive MWNTs networks in the PA6/PP/MWNTs (20/80/4) composite as proved by means of field emission scanning electron microscopy and rheological measurements. The morphology and electrical properties of the PA6/PP/MWNTs (20/80/4) composites were significantly influenced by blending sequences. When blending 3.9 phr MWNTs with a pre-mixed PA6/PP/MWNTs (20/80/0.1) composite, the dispersed PA6 phase formed an elongated structure, which was beneficial to the electrical properties.     

Microstructural image analysis and structure–electrical conductivity relationship of single- and multiple-filler conductive composites

The electrical conductivity of polypropylene/graphite (PP/G) composites and polypropylene/graphite/carbon black (PP/G/CB) was investigated in this paper. The conductivity experimental data of PP/G composites was correlated to theoretical models, which exist in the literature, and the results showed higher values of the exponent t compared to the expected typical values. Moreover, these analytical models were unable to describe the electrical behaviour for multiple-filler conductive composites such as PP/G/CB composites. A 2D computer simulation to numerically compute the electrical conductivity based on digital image analysis was found to be somewhat useful to describe the mechanism of conduction in PP/G/CB composites and to determine the critical factors in developing high electrically conductive composites.     

Role of micro/nano fillers on mechanical and tribological properties of polyamide66/polypropylene composites

The objectives of this research article is to evaluate the mechanical and tribological properties of polyamide66/polypropylene (PA66/PP) blend, graphite (Gr) filled PA66/PP, nanoclay (NC) filled PA66/PP and NC plus short carbon fiber (NC + SCF) filled PA66/PP composites. All composites were fabricated using a twin screw extruder followed by injection molding. The mechanical properties such as tensile, flexure, and impact strengths were investigated in accordance with ASTM standards. The friction and sliding wear behaviour was studied under dry sliding conditions against hard steel on a pin-on-disc apparatus. Scanning electron micrographs were used to analyze the fracture morphologies. From the experimental investigation, it was found that the presence of NC and SCF fillers improved the hardness of PA66/PP blend. Further, the study reveals that the tensile and flexural strength of NC + SCF filled PA66/PP was higher than that of PA66/PP blend. Inclusion of micro and nanofillers reduced the wear rate of PA66/PP blend. The wear loss of the composites increased with increasing sliding velocity. The lowest wear rate was observed for the blend with nanoclay and SCF fillers. The wear rates of the blends with micro/nanofillers vary from 30–81% and lower than that of PA66/PP blend. The wear resistance of the PA66/PP composites was found to be related to the stability of the transfer film on the counterface. The results have been supplemented with scanning electron micrographs to help understand the possible wear mechanisms.     

Effect of flame retardants on flame retardant,mechanical, and thermal properties of sisal fiber/polypropylene composites

A flame retardant efficiency of flame retardants; ammonium polyphosphate (APP), magnesium hydroxide (Mg(OH)₂), zinc borate (Zb), and combination of APP with Mg(OH)₂ and Zb in sisal fiber/polypropylene (PP) composites was investigated using a horizontal burning test and a vertical burning test. In addition, maleic anhydride grafted polypropylene (MAPP) was used as a compatibilizer to enhance the compatibility in the system; i.e. PP-fiber and PP-flame retardants. Thermal, mechanical, and morphological properties of the PP composites were also studied. Adding the flame retardants resulted in improved flame retardancy and thermal stability of the PP composites without deterioration of their mechanical properties. APP and combination of APP with Zb effectively enhanced flame retardancy of the PP composites. No synergistic effect was observed when APP was used in combination with Mg(OH)₂. SEM micrographs of PP composites revealed good distribution of flame retardants in PP matrix and good adhesion between sisal fiber and PP matrix.     

Polyolefin composites with curaua fibres: Effect of the processing conditions on mechanical properties,morphology and fibres dimensions

Composites of polypropylene (PP) and high density polyethylene (HDPE) reinforced with 20 wt.% of curaua fibres were prepared using a twin-screw extruder and the effect of screw rotation speed (SRS) was evaluated by measuring the output, the mechanical properties of the composites, the morphology and the fibre dimensions. Increase in SRS causes a decrease in length, diameter and aspect ratio of the fibres in both composites, due to the high shear forces acting in the molten polymer and transferred to the fibres. Consequently, the reinforcement effect of the fibres decreased, as evidenced by the flexural and tensile mechanical properties of the composites. Additionally, polymeric matrices undergoes thermo-mechanical degradation during processing, this also contributed to the changes in the mechanical properties. Comparison between the matrices showed that PP composites are less affected by changes in SRS, suffering fewer changes in fibre dimensional parameters and in the mechanical properties than HDPE composites.     

聚丙烯/尼龙6共混物的X射线衍射研究EI

用广角 X射线衍射 (WAXD)方法研究了不同接枝聚丙烯对聚丙烯 /尼龙 6 (PP/PA6 )共混物结晶行为的影响。结果表明 ,与简单机械共混物相比 ,由于增容剂的加入 ,PP的结晶行为发生变化——不同晶面的生长速率不同 ,且在所研究的范围内有随增容剂含量的增加 。     

Grafting effects of polypropylene/polyethylene blends with maleic anhydride on the properties of the resulting wood-plastic composites

In the presented study, polypropylene (PP) and high density polyethylene (PE) were blended at the ratios of 80/20 and 20/80 to simulate recycled waste thermoplastic mixtures. The effects of in situ grafting of PP/PE blends with maleic anhydride through the extruder on the mechanical and rheological properties of resulting wood/plastic composites were investigated. Different ratios of PP and PE in the blends created distinct properties in the resulting composites. Grafting of PP and PE blends improved the tensile and flexure properties of the resulting composites. The composites exhibited a reduced water uptake and resultant dimensional swelling due to grafting with maleic anhydride. Grafting of the blends also considerably improved the interfacial bonding and enhanced the dispersion of wood in the matrix, as evidenced by rheological analysis and scanning electron microscopy.     

炭黑／聚丙烯／聚碳酸酯复合材料导电性能和PTC特性

以聚丙烯（PP）／聚碳酸酯（PC）共混物为基体,采用不同种类炭黑（CB）填充制备导电复合材料并对其导电性能和PTC特性进行研究。结果表明：在常温时,PP／PC共混基体中PP含量大于40wt％时,材料的电阻率急剧下降;共混比为50：50（wt％）复合材料的电阻率达到最小值。加热时,两者均未出现明显NTC现象,说明PP／PC的共混可以有效的消除NTC效应。但PTC强度仅为1个数量级,远低于PP／CB二元复合材料。CB是影响PTC效应的重要因素之一,达到逾渗值时随着体系CB含量减少PTC效应会增强;乙炔炭黑与炉法CB填充的CB／PP／PC复合材料相比较,前者的体积电阻率较低,而两者的逾渗阈值相近,均为6．6％;乙炔CB为填料的CB／PP／PC三元复合材料的阿C突变温度在140℃附近,以炉法CB为填料时,PTC效应突变点出现在150℃（PC的Tg）附近。DSC分析结果表明,复合材料中PP的结晶度随着CB含量增加呈上升趋势,CB含量为15％时,PP的结晶度为32．75％,对于整个PP／PC／CB体系而言结晶部分的含量较低,因此该体系的PTC效应强度较低。     

Influence of hexamethylene diamine functionalized graphene oxide on the melt crystallization and properties of polypropylene nanocomposites

Hexamethylene diamine was chemically grafted to the graphene oxide (GO) surface via two type of reactions viz. (i) amidation reaction between amine groups and carboxylic acid sites of GO and (ii) nucleophilic substitution reactions between amine and epoxy groups on surface. Successful grafting of HMDA on GO surface was confirmed using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and thermogravimetric results (TGA). These chemically modified GO (AGO) with varying loading amount were incorporated in polypropylene matrix in the presence of maleic anhydride-g-polypropylene (PP-g-MA) compatibilizer through melt processing technique. X-ray diffraction (XRD) and differential scanning calorimetric (DSC) studies revealed that the loading of AGO resulted in the improvement in crystallization characteristics of polypropylene. Owing to the strong interfacial interactions between AGO and polymer, significant enhancement in mechanical and electrical properties was observed, when compared to pristine GO filled polypropylene composites.     

Characterization and biodegradability of polypropylene composites using agricultural residues and waste fish

The objective of this research was to study the potential of waste agricultural residues such as rice-husk fiber (RHF), bagasse fiber (BF), and waste fish (WF) as reinforcing and biodegradable agents for thermoplastic composites. Addition of maleic anhydride grafted polypropylene (MAPP) as coupling agent was performed to promote polymer/fiber interfacial adhesion. Several composites with various polypropylene (PP) as polymer matrix, RHF, BF, WF, and MAPP contents were fabricated by melt compounding in a twin-screw extruder and then by injection molding. The resulting composites were evaluated through mechanical properties in terms of tensile, flexural, elongation at break and Izod notched impact following ASTM procedures. Biodegradability of the composites was measured using soil burial test in order to study the rates of biodegradation of the composites. In general, the addition of RHF and BF promoted an increase in the mechanical properties, except impact strength, compared with the neat PP. According to the results, WF did not have reinforcing effect on the mechanical properties, while it could considerably improve the biodegradation of the composites. It was found that the composites with high content of WF had higher degradation rate. Except impact strength, all mechanical properties were found to enhance with increase in cellulosic fiber loading In addition, mechanical properties and biodegradability of the composites made up using RHF was superior to those of the composites fabricated with BF, due to its morphological (aspect ratio) characteristics.     

接枝架桥剂配比对PP/a-PA66原位成纤复合材料形态结构和力学性能的影响

用反应性单体与助反应单体不同配比(C/R)制得的特殊结构的反应性增容剂(SCRC)与尼龙66(PA66)反应性共混,制得活性PA66(a-PA66),再将聚丙烯(PP)与a-PA66原位成纤复合,即采用"后期增容"技术,制得了一系列PP/a-PA66原位成纤复合材料,对其形态结构及力学性能进行了表征。结果表明,制SCRC时C/R过小,如2/8时,复合材料中PA66形成较均匀的微纤,但微纤与PP界面结合弱,综合力学性能不好;C/R过大,如6/4时,复合材料中PA66难以成纤,界面结合也弱,综合力学性能也不好;C/R为4/6时,复合材料中微纤的异形化程度最大,构筑成结合强的适度柔性界面,综合力学性能最佳,缺口冲击强度(NIIS)、拉伸屈服应力(TYS)、弯曲模量(FM)分别为原料PP的1.41倍、0.99倍、1.22倍。     

The falling weight impact properties of maleic anhydride compatibilized polypropylene–polyamide blends

A series of polypropylene–polyamide 6 (PP–PA) blends of composition 80: 20, 50:50 and 20:80 have been prepared in a twin screw extruder followed by injection moulding. Maleic anhydride grafted polypropylene was used as a compatibilizer for these blends. Static mechanical and falling weight impact tests were performed on these blends. The fracture surfaces of impact specimens were subsequently examined by scanning electron microscopy (SEM). The mechanical properties of the blends were found to be strongly dependent on the PP–PA blend ratios. The Young’s modulus, tensile strength and impact energy were observed to increase with increasing PA content. The impact strength was better in blends when the PA content approached 80 wt %. SEM observations revealed that the addition of compatibilizer resulted in good adhesion between the PP dispersed domains and PA matrix in the PP–PA 20:80 blend. Furthermore, the SEM fractographs also indicated that the cold drawn of PA matrix and debonding of PP domains were responsible for the high impact strength of this blend. This revised version was published online in November 2006 with corrections to the Cover Date.     

Mechanical properties and flammability of sisal/PP composites: Effect of flame retardant type and content

In this research, magnesium hydroxide (Mg(OH)₂) and zinc borate, as flame retardants, were incorporated into sisal/PP composites. Maleic anhydride grafted polypropylene was also used as a compatibilizer. Adding flame retardants into sisal/PP composites reduced burning rate and increased thermal stability of the composites. No synergistic effect was observed when both magnesium hydroxide and zinc borate were incorporated in the sisal/PP composites. In addition, the sisal/PP composites exhibited insignificant difference of shear viscosity at high shear rate indicating that types of flame retardants used in this study had no impact on the processability of the composites. Good distribution of flame retardants and sisal fiber in PP matrix was also observed. All PP composites had lower impact strength than the neat PP. However, the sisal/PP composites with the addition of Mg(OH)₂ and zinc borate exhibited comparable tensile and flexural properties to the sisal/PP composites without adding those flame retardants. Therefore, the addition of Mg(OH)₂ and zinc borate enhanced flame retardancy of sisal/PP composites without sacrificing their mechanical properties.     

力化学方法制备PP—g—HMA增容PA6／PP／硅灰石复合材料的形？…

以力化学方法制备的Ｎ－羟甲基丙烯酰胺接枝聚丙烯（ＰＰ－ｇ－ＨＭＡ）作尼龙６（ＰＡ６）／聚丙烯（ＰＰ）共混体系的增容剂,将增容尼龙６／聚丙烯共混体系与硅灰石复合。研究了复合材料的形态结构、硅灰石用量、偶联剂种类和用量以及增容剂等对复合材料的力学性能的影响。结果表明,ＰＰ－ｇ－ＨＭＡ能提高ＰＡ６／ＰＰ／硅灰石复合材料的力学性能,而ＫＨ－５５０和ＯＮ－３３０两种偶联剂复配使用则可以显著提高ＰＰ－ｇ－ＨＭ