A comparative study of polypropylene/(chloroprene rubber) and (recycled polypropylene)/(chloroprene rubber) blends

The blends of virgin polypropylene (PP) and recycled polypropylene (RPP) with chloroprene rubber (CR) have been prepared. The effect of different blend ratios on tensile properties, swelling behavior, morphology, and crystallinity of both blends of virgin and RPP was investigated. The tensile strength and Young's modulus of both blends decreased with increasing CR in blend ratios but the elongation at break was increased. It was found that the tensile properties of PP/CR blends were better than the RPP/CR blends. The PP/CR blends showed the lower value of swelling index. The scanning electron micrograph of the tensile fractured surface of PP/CR blends indicates that a higher energy is needed to cause failure compared with RPP/CR blends. The differential scanning calorimery results indicated that the degree of crystallinity of PP/CR blends also was found to be higher than RPP/CR blends. J. VINYL ADDIT. TECHNOL., 21:122–127, 2015. © 2014 Society of Plastics Engineers     

The effect of polypropylene maleic anhydride on polypropylene/(recycled acrylonitrile butadiene rubber)/(sugarcane bagasse) composite

The effect of polypropylene maleic anhydride (PPMAH) on the tensile properties and morphology of polypropylene (PP)/(recycled acrylonitrile butadiene rubber) (NBRr)/(sugarcane bagasse) (SCB) composites has been studied. Six different composites (100/0/10, 80/20/10, 70/30/10, 60/40/10, 50/50/10, and 40/60/10), with fixed 5 wt% of PPMAH compatibilizer and without PPMAH addition, were carried out. The composites were prepared through melt‐mixing technique at 180^oC for 9 min using a rotor speed of 15 rpm. The specimens were analyzed for mechanical properties and examined with scanning electron microscopy. The tensile strength was found to decrease with increasing filler content. However, tensile strength and Young's modulus of the PPMAH compatibilized composites were found to increase, while the elongation at break showed the opposite trend as compared with the control composites. The morphology results support the tensile properties and indicated a better interaction between the SCB filler and PP/NBRr matrices with the presence of PPMAH as a compatibilizer. This is due to the esterification bonding between the SCB filler and PP matrix in the presence of PP/NBRr matrices. J. VINYL ADDIT. TECHNOL., 23:228–233, 2017. © 2015 Society of Plastics Engineers     

胶乳-悬浮液共沉法天然橡胶/埃洛石纳米管复合材料的结构与性能

利用天然橡胶(NR)胶乳和埃洛石纳米管(HNTs)悬浮液的负电稳定性,采用胶乳-悬浮液共沉法制备了NR/HNTs复合材料,并对其硫化特性、微观结构、力学性能以及动态力学性能进行了研究.结果表明,HNTs的引入可促进NR的硫化反应,随HNTs用量的增加,焦烧期和正硫化时间缩短;HNTs在复合材料中的分散性极佳;随着HNTs用量的增加,纳米复合材料的定伸应力和邵尔A硬度明显增大,扯断伸长率有所下降,综合力学性能在20份时最好;随着HNTs用量的增加,纳米复合材料的玻璃化转变温度略有升高,转变区的损耗因子明显下降.     

Investigation on microstructure and properties of foamed (wood fiber)/(recycled polypropylene) composites

Microcellular foamed (wood fiber)‐reinforced recycled polypropylene composites (MFWPCs) were prepared by an injection molding process where azodicarbonamide was used as a chemical foaming agent. The influence of injection parameters (injection temperature, dwell pressure) on the microcellular structure (cell diameter and cell density) and the mechanical properties of the MFWPCs were investigated. The results indicated that when the melting temperature was 180°C and the dwell pressure was 12.5 MPa, a uniformly distributed microcellular structure of MFWPCs was obtained. Compared with solid wood plastic composites, the density of the MFWPCs decreased by 24.5%, and its impact strength of MFWPCs increased by 53%, because the propagation direction of the crack changed to the “skip” or “bifurcation” mechanism as a result of the microcellular structure, and the surrounding matrix of this structure made it easy to produce forced high‐elastic deformation. The toughening mechanism of the microcellular structure was analyzed. J. VINYL ADDIT. TECHNOL., 2012. © 2012 Society of Plastics Engineers     

Hybrid‐filler filled polypropylene/(natural rubber) composites: Effects of natural weathering on mechanical and thermal properties and morphology

Comparison was made between the properties of recycled newspaper (RNP)/carbon black (CB) and recycled newspaper (RNP)/silica hybrid filled polypropylene (PP)/natural rubber (NR) composites. The properties studied were mechanical, thermal, and morphological. These composites were also subjected to natural weathering, i.e., the tropical climate in Penang, Malaysia, for 6 months. The incorporation of CB and silica at all weight ratios of RNP/CB and RNP/silica hybrid gave increases in tensile strength, elongation at break (E_B), Young's modulus, melting temperature (T_m), heat of fusion of composites (ΔH_f(com)), crystallinity of composites (X_com), and the crystallinity of PP (X_PP). As expected, the tensile properties (except for Young's modulus), T_m, ΔH_f(com), X_com, and X_PP of the composites exhibited lower values after weathering than before weathering. The extent of chemical degradation was studied by Fourier transform infrared spectroscopy, and the results showed the formation of several functional groups, i.e., hydroxyl, hydroperoxide, vinyl, carboxylic acid, and ketone. At the same filler weight ratio, the composites filled with RNP/CB hybrid showed higher values of tensile strength and E_B but lower values of Young's modulus, ΔH_f(com), X_PP, and X_PP, as compared to those with the RNP/silica hybrid under weathering conditions. The good retention in tensile properties indicated that the replacement of RNP by CB and silica improved the weatherability performance of the PP/NR composites. J. VINYL ADDIT. TECHNOL., 2008. © 2008 Society of Plastics Engineers     

Effect of filler surface treatment on the properties of recycled high‐density polyethylene/(natural rubber)/(Kenaf powder) biocomposites

Biocomposites were prepared from a kenaf core powder and recycled high‐density polyethylene/(natural rubber) blend by using an internal mixer at 165^oC and 50 rpm. The effect of the filler content and the filler surface treatment was studied. Chemical modification of kenaf filler was performed with alkali pretreatment followed by treatment with silane. Scanning electron microscopy and infrared spectroscopy studies confirmed changes in the chemical compositions and structural characteristics induced through the modification. It was found that treated biocomposites offered higher tensile strength and tensile modulus, but lower elongation at break compared with untreated biocomposites. Lower water absorption and higher thermal stability of the resultant biocomposites were also obtained when treated fillers were used. J. VINYL ADDIT. TECHNOL., 20:218–224, 2014. © 2014 Society of Plastics Engineers     

碳纳米管的尺寸及用量对天然橡胶复合材料性能的影响

将碳纳米管（CNTs）添加到天然橡胶（NR）中制备了CNTs/NR复合材料,考察了CNTs的管径和用量对复合材料硫化特性、力学性能、动态力学性能和分散性的影响。结果表明,在管径相同时,随着CNTs用量的增大,复合材料的正硫化时间延长。随着CNTs用量的增大,复合材料的拉伸强度和扯断伸长率先增大后减小。相同管径件下,CNTs的用量越大,Payne效应越强,储能模量变化越大,损耗因子也越大;而在相同用量下,CNTs的管径越大,Payne效应越弱,储能模量变化越小,损耗因子也越小。当CNTs用量为15份、管径为80 nm时,其在NR基体中的分散性最好,复合材料的综合力学性能及动态力学性能最佳。     

碳纳米管/天然橡胶复合材料的结构与性能

通过机械混炼法制备了碳纳米管(CNT)／天然橡胶(NR)复合材料,研究了CNT的预处理方式对复合材料结构与性能的影响。结果表明,与NR相比,CNT／NR复合材料的硫化返原现象减轻,硫化后凝胶质量分数降低,硫化剂用量应适当增加,由混酸氧化处理的CNT填充橡胶复合材料的硫化迟滞效应明显;复合材料内部存在CNT的富集区域和CNT含量很少的橡胶区域,CNT与NR之间的界面结合作用不好;由HF处理的CNT填充橡胶复合材料的整体性能最好,但受CNT在橡胶基体中的不良分散状态及界面性质的影响,其力学性能不高。     

Investigation of the dynamic mechanical behavior of polypropylene/(wood flour)/(kenaf fiber) hybrid composites

Polypropylene/(wood flour)/(kenaf fiber) hybrid composites were prepared in an internal mixer. Kenaf was considered as a fibrous filler and wood flour as a particulate filler. The lignocellulosic loading used was 50%. Dynamic mechanical thermal analysis properties such as storage modulus (E′), loss modulus (E″), damping factor (tan δ), and adhesion factor were evaluated. It was found that the adhesion factor could interpret the interfacial adhesion between lignocellulosic fillers and the plastic matrix macroscopically. This factor was affected by the type of filler used and the coupling agent concentration. The variation of storage modulus was affected more by the shape of the filler and the coupling agent concentration at higher temperatures than at temperatures below the glass transition. Owing to a higher probability of agglomeration in a sample containing 50 wt% of wood flour, the storage modulus and complex viscosity of this sample were higher than those of other samples. Cole‐Cole diagrams showed that the homogeneity of samples containing a higher amount of coupling agent was higher than that of samples with a lower concentration. J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers     

Novel epoxidized natural rubber toughened polyamide 6/halloysite nanotubes nanocomposites

A novel ternary epoxidized natural rubber (ENR-50) toughened polyamide 6/halloysite nanotubes (PA6/HNTs) nanocomposites were successfully prepared by extrusion followed by injection molding. The HNTs revealed a favourable interaction with the PA6 matrix as seen by the improvement in mechanical properties and presence of a new FTIR vibrational peak. The ENR-50 showed an improvement of the impact strength up to 300% with a super tough characteristic at only 15 wt% ENR-50. The naturally occurring nanotubes proved to be a suitable candidate to replace other synthetic nanotubes.     

Effects of partial replacement of commercial fillers by recycled poly(ethylene terephthalate) powder on the properties of natural rubber composites

Commercial fillers, including carbon black (N550), halloysite nanotubes (HNTs), and precipitated silica, were replaced by recycled poly(ethylene terephthalate) powder (R‐PET) in natural rubber (NR) composites. Five different compositions of NR/N550/R‐PET, NR/HNTs/R‐PET, and NR/silica/R‐PET compounds, i.e., 100/20/0, 100/15/5, 100/10/10, 100/5/15, and 100/0/20 parts per hundred rubber (phr), were prepared on a two‐roll mill. The curing behavior, tensile properties, and morphological characteristics of the natural rubber composites were investigated. The results indicated that the replacement of carbon black, HNTs, and silica by R‐PET decreased the tensile strength and tensile modulus, such that NR/silica/R‐PET composites showed the lowest effect, followed by NR/HNTs/R‐PET and NR/N550/R‐PET composites. The negative effect on these properties can be explained by the decrease of crosslink density. The curing results revealed that with the replacement of carbon black by R‐PET, the scorch time and cure time decreased, but that the NR/HNTs/R‐PET and NR/silica/R‐PET composites exhibited the opposite trend. Scanning electron microscopy investigation of tensile fracture surfaces confirmed that the co‐incorporation of N550/R‐PET improved the dispersion of R‐PET and enhanced the interaction between the fillers and NR matrix more than R‐PET and silica/R‐PET hybrid fillers. J. VINYL ADDIT. TECHNOL., 2012. © 2012 Society of Plastics Engineers     

Crystallization behavior and mechanical properties of polypropylene/halloysite composites

In this work, halloysite nanotubes (HNTs), a new type of inexpensive filler, were used for the modification of polypropylene (PP). HNTs were first surface treated by methyl, tallow, bis-2-hydroxyethyl, quaternary ammonium, then melt mixed with PP. Scanning electron microscope (SEM) was used to examine the dispersion of HNTs in PP matrix. Differential scanning calorimetry (DSC), polarized light microscope (PLM), dynamic melt rheometry and wide angle X-ray diffraction (WAXD) were employed to investigate the crystallization behavior of the prepared PP/HNT composites. The mechanical properties were evaluated by Instron and impact tests. SEM results revealed that HNTs could be well-dispersed in PP matrix and had a good interfacial interaction with PP, even up to a high content of 10 wt%. DSC data indicated that HNTs could serve as a nucleation agent, resulting in an enhancement of the overall crystallization rate and the non-isothermal crystallization temperature of PP. PLM showed a constant spherulite growth rate and a decreased spherulite size at given isothermal crystallization temperature, suggesting that nucleation and growth of a spherulite are two independent processes. The result obtained by dynamic melt rheometry indicated that HNTs mainly promoted nucleation and had not much influence on the growth of PP crystallization. Nevertheless, by fast cooling the samples, almost constant spherulite size can be obtained for both pure PP and PP/HNT composites due to the limited nucleation effect of HNTs on PP crystallization. WAXD showed that HNTs mainly facilitated α-crystal form of PP. Though a good dispersion of HNTs in PP matrix was observed, out of our expectation, not much enhancement on mechanical properties of PP/HNT composites had been achieved, and this could be mainly ascribed to the constant crystallinity and spherulite size of PP as well as the small length/diameter ratio of HNTs.     

Effects of dynamic vulcanization on the physical,mechanical, and morphological properties of high‐density polyethylene/(natural rubber)/(thermoplastic tapioca starch) blends

Blending of high density polyethylene (HDPE), natural rubber (NR), and thermoplastic tapioca starch (TPS) have been studied. Two series of samples having 5–30 wt% of TPS were prepared: (a) unvulcanized blends (control) and (b) dynamically vulcanized HDPE/NR/TPS blends. The composition of the HDPE/NR was constant and fixed at a blend ratio of 70/30. Morphology studies by SEM showed that the TPS particles were homogeneously dispersed and well‐embedded in vulcanized HDPE/NR matrix. The SEM micrographs showed agreement with the tensile strength and elongation at break values. Tensile strength improved significanly when the HDPE/NR/TPS blends were vulcanized by using sulfur curative system. The enhancement in tensile properties is attributed to the crosslinking reaction within the NR phase. J. VINYL ADDIT. TECHNOL., 18:192–197, 2012. © 2012 Society of Plastics Engineers     

The effect of adding devulcanized rubber on the thermomechanical properties of recycled polypropylene

This work aims to investigate the effect of adding vulcanized or partially devulcanized rubbers on recycled polypropylene (PPr), considering thermomechanical and morphological properties. The study proposes to better understand how structural changes underwent by rubber (after the devulcanization) contributed to improving the mechanical properties of the PPr. The PPr/rubber blends were prepared by a co-rotating twin-screw extruder and then were injected. The blends composed of the most devulcanized rubbers by microwaves with refined microstructure showed higher values of elongation at break and toughness. Data showed that the devulcanization process applied to the rubber interfered positively in its adhesion to the PPr. Data from dynamic mechanical analysis and atomic force microscopy indicated that the most devulcanized rubbers presented an interface more connected to PPr. These chemical interactions possibly impacted the mechanical properties of the PPr. Moreover, dilatation processes favored the fracture mechanisms of the PPr when rubber was added to it.     

埃洛石纳米管对丁苯橡胶的增强作用

研究了未经表面改性和用双-[3-(三乙氧基硅)丙基]四硫化物(Sj-69)改性的埃洛石纳米管(HNTs)对丁苯橡胶(SBR)硫化胶力学性能的影响及其微观形貌.结果表明,HNTs对SBR具有明显的增强作用;Si-69能进一步提高其增强效果,有效地改善HN/s在橡胶基体中的分散,并能降低SBR/HN了s硫化胶的滚动阻力和动态生热.     

Effects of natural weathering on the degradation of alkaline‐treated peanut shell filled recycled polypropylene composites

The present work evaluates the potential of the natural filler peanut shell powder (PSP) on the properties and degradation behavior of alkaline‐treated PSP filled recycled polypropylene (RPP) composites. For this purpose, 0–40 wt% of untreated PSP and hydrogen peroxide‐treated PSP were incorporated into RPP composites that were fabricated via a melt‐mixing molding system. The fabricated composites were exposed to the natural environment of Penang, Malaysia for 6 months. The properties of both untreated and treated RPP/PSP composites were assessed. Results showed that the tensile properties of the treated RPP/PSP composites were higher than that of the untreated RPP/PSP composites. The treated RPP/PSP composites were less affected by weathering degradation compared to the untreated RPP/PSP composites. An increase in the carbonyl index of both composites also confirmed that some degradation had taken place. On comparing the crystallinity of both composites, the treated composites showed lower crystallinity than untreated composites. J. VINYL ADDIT. TECHNOL., 25:26–34, 2019. © 2018 Society of Plastics Engineers     

Properties of polypropylene/(natural rubber)/organomontmorillonite nanocomposites prepared by melt blending

The aim of this work was to study the effects of an organomontmorillonite or organoclay (OMMT) on the properties of a thermoplastic elastomer blend prepared by melt blending and based on polypropylene (PP) and natural rubber (NR). The results obtained showed a slight improvement of the blend mechanical (strength, modulus, and elongation), thermal, and solvent resistance properties when the amount of the organoclay was 3 phr. Results obtained by XRD analysis showed that at 3 phr of organoclay loading there was a shift toward low angles of the organoclay (001) plane diffraction peak and a disappearance of the PP β–phase peak. This shift signifies an intercalation of the polypropylene/(natural rubber) chains between organoclay platelets. An SEM study revealed that at the 3 phr organoclay concentration the blend became tougher, and the organoclay was located both at the PP/NR interface and inside the NR dispersed phase. A DSC study showed a decrease of the melting temperature of the PP phase at the 3 phr organoclay loading. A rheological study revealed that the addition of organoclay had not increased the melt viscosity of the PP/NR blend, and the stiffness was related to the maximum torque increase as a function of the organoclay loading. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers     

聚丙烯基高含量埃洛石纳米管复合材料的制备和性能

采用双螺杆挤出机制备聚丙烯(PP)基高含量(33 phr)埃洛石纳米管(HNTs)复合材料,从挤出机沿程3个位置和机头出口处取样,观察样品的微观结构并测试其流变性能和热稳定性。结果表明,本文设置的螺杆结构提供的分散和分布混炼使PP/HNTs复合材料中HNTs团聚体的尺寸快速减小,HNTs在PP基体中分散得越来越均匀,使挤出机沿程3个位置所取复合材料样品的低频区储能模量逐渐提高、末端斜率逐渐降低、松弛时间逐渐变长。机头入口所取复合材料样品的热稳定性要比机头出口样品的高,这归因于前者样品中较为无序且较均匀排列的HNTs纳米空腔能更有效地诱捕降解产物。     

Comparison of natural halloysite with synthetic carbon nanotubes in poly(lactic acid) based composites

The objective of this study is to compare the mechanical properties, structure and degradability of the nanocomposites prepared with tubular nanofillers, halloysite (HNT) and carbon nanotube (CNT) in poly(lactic acid) (PLA), and thermoplastic polyurethane (TPU) toughened PLA (T‐PLA) matrices. In the PLA matrix, CNT increased, whereas HNT decreased the tensile strength with increasing filler content. Also, the elongation at break and impact strength decreased with increasing CNT content, but these properties were relatively unchanged with increasing HNT content. However, when (TPU) was used as an impact modifier‐compatibilizer, addition of HNT further increased the impact strength and the elongation at break of the matrix, since short and straight HNT fibers were pulled out from the extensible, toughened matrix. The long and curvy CNT fillers always caused brittle fracture and affected the impact strength and elongation at break in a negative manner as the CNT content was increased. Both types of fillers did not significantly influence the degradation of PLA or toughened PLA matrices. POLYM. COMPOS., 38:2337–2346, 2017. © 2015 Society of Plastics Engineers     

Naturally occurring halloysite nanotubes for enhanced durability of natural rubber/ethylene propylene diene monomer rubber vulcanizate

A facile approach of using halloysite nanotubes (HNTs) was proposed to address the durability performance demands of natural rubber (NR)/ethylene propylene diene monomer rubber (EPDM) blends and to protect them from the deleterious effects of the service environment including ozone, chemicals, abrasion, and cyclic loading. The introduction of HNTs substantially improved the stability of NR/EPDM when exposed to ozone (over fourfold enhancement with the addition of 5 phr HNTs). Moreover, the HNT-filled NR/EPDM vulcanizates offered approximately 66% reduction in the solvent-mediated swelling in comparison to the unfilled sample. Fatigue life studies showed that the HNT-reinforced NR/EPDM composite could withstand 30% more cycles to failure than the un-reinforced NR/EPDM blend. The effect of various HNT loading on the morphological, mechanical, physical, and rheological properties of nanocomposite vulcanizates based on NR/EPDM was also investigated. The morphological investigations revealed that the introduction of HNT into the NR/EPDM rubber matrix caused a rough morphology in fracture surface and a well-dispersed structure was obtained with the addition of up to 5 phr of HNTs. These findings were further supported by rheological, mechanical, and thermodynamical results.