Three-body abrasive wear behaviour of carbon and glass fiber reinforced epoxy composites

Three-body abrasive wear behaviour of carbon–epoxy (C–E) and glass–epoxy (G–E) composites has been investigated. The effect of abrading distance, viz., 270, 540, 810 and 1080 m and different loads of 22 and 32 N at 200 rpm have been studied. The wear volume loss and specific wear rate as a function of load and abrading distance were determined. The wear volume loss increases with increasing load/abrading distance. However, the specific wear rate decreases with increase in abrading distance and increases with the load. However, C–E composite showed better abrasion wear resistance compared to G–E composite. The worn surface features have been examined using scanning electron microscope (SEM). SEM micrographs of abraded composite specimens revealed the high percentage of broken glass fiber compared to carbon fiber and also better interfacial adhesion between epoxy and carbon fiber.     

Mechanical and three-body abrasive wear behaviour of three-dimensional glass fabric reinforced vinyl ester composite

The mechanical and three-body abrasive wear behaviour of two- and three-dimensional E-glass woven fabric reinforced vinyl ester composites were studied in this article. The mechanical properties were evaluated using universal testing machine as per ASTM D-638. Three-body abrasive wear tests were conducted using rubber wheel abrasion tester (RWAT) under different abrading distances at two loads, wherein the wear volume loss were found to increase and that of specific wear rate decrease. The results indicate that the three-dimensional glass woven fabrics in vinyl ester (G_3D–V) have significant influence on wear under varied abrading distance/loads. Further, it was found that G_3D–V composite exhibited lower wear rate compared to two-dimensional glass woven fabric reinforced vinyl ester (G_2D–V) composite. The worn surface features, as examined through scanning electron microscope (SEM), show ruptured glass fiber in G_2D–V composite compared to G_3D–V composites.     

Development of a new inexpensive green thermoplastic composite and evaluation of its physico-mechanical and wear properties

In the present study an attempt has been made to use turmeric spent (TS) as reinforcing filler to fabricate polypropylene (PP) green composite for load bearing and tribological applications. PP/TS composites were fabricated using varying amounts of TS viz, 10%, 20%, 30% and 40% (w/w) by twin screw extrusion method. The fabricated PP green composites were evaluated for physico-mechanical and tribological properties. Experimentally obtained tensile values were compared with theoretically predicted values using different theoretical models. Tensile modulus of composites increased from 1041 to 1771 MPa with the increase in filler addition from 0 to 40 wt.%. Flexural strength and flexural modulus of composites were improved after incorporation of TS into PP matrix. The water absorption characteristics of composites were determined. The effect of abrading distances viz., 150, 300, 450, and 600 m and different loads of 23.54 and 33.54 N at 200 rpm on the abrasive wear behaviour were studied using dry sand/rubber wheel abrasive test rig. The TS filler lowered the abrasion resistance of PP/TS composites. The wear volume loss and specific wear rate as a function of abrading distance and load were determined. The surface morphology of tensile fractured green composites and their worn surface features were examined under scanning electron microscope.     

Influence of fibre orientation on three-body abrasive wear behaviour of unidirectional carbon fibre-reinforced polyetherimide composite

Three-body abrasive wear behaviour of neat polyetherimide (PEI) and unidirectional carbon fibre-reinforced PEI (CF/PEI) has been studied using a rubber wheel abrasion test rig. The abrasive wear studies were carried out at different loads (5–20 N) at a constant sliding velocity (v = 2.4 m/s) of rubber wheel. The influence of fibre orientation, i.e. parallel (P-fibre orientation) and anti-parallel (AP-fibre orientation) on wear rate of CF/PEI composite has also been studied. The results showed that the fibre orientation has a significant influence on the three-body abrasive wear behaviour of CF/PEI. The abrasive wear rate was higher when fibres are oriented at anti-parallel than that of parallel orientation of fibres. The worn surfaces have been observed using scanning electron microscope to understand the possible wear mechanisms involved during material removal processes.     

Investigations on hygrothermal aging of thermoplastic polyurethane material

In this investigation, the absorption and diffusion of water in thermoplastic polyurethane (TPU) was studied. Water-sorption experiments, physical and mechanical property tests were performed after immersion in water at a set temperature of 70 °C for up to 6 months. Emphasis was given to the effect of immersion aging on thermal, mechanical and tribological properties. Fickian diffusion behaviour was found during the initial immersion time followed by saturation stage as time progressed. The use of differential scanning calorimetry (DSC) analysis showed that the glass transition temperature (Tg) was sensitive to the effect of hygrothermal aging and it decreased with increasing water uptake.More significantly, the mechanical properties in bulk material, obtained from tensile test, were affected by aging. Elastic modulus and stress at 200% of strain of the studied TPU were decreased after sufficient exposure to moisture. On the other hand, the mechanical properties of the material surface were equally investigated with the help of an abrasive wear test. A decrease in wear resistance of the aged TPU was discerned. The reversibility of mechanical and physical properties after moisture exposure was also assessed in this study. The polymer degradation was found as irreversible phenomenon.Finally, the evolution of the mechanical properties seems to be well correlated to structural modifications obtained from Fourier transform infrared spectroscopy (FTIR) characterization.     

Abrasive wear behaviour of hard powders filled glass fabric–epoxy hybrid composites

The effect of incorporation of tungsten carbide (WC) and tantalum niobium carbide (Ta/NbC) powders on three-body abrasive wear behaviour in glass fabric–epoxy (G–E) composites was investigated and findings are analysed. A vacuum assisted resin transfer moulding (VARTM) technique was employed to obtain a series of G–E composites containing different fillers (WC and WC + Ta/NbC). Dry sand rubber wheel abrasion test was carried out at 200 rpm speed. The effect of different loads (22 and 32 N) and abrading distances (from 135 to 540 m) on the performance of the wear resistance were measured. The wear volume loss of the composites was found increasing with the increase in abrading distances and under the same conditions the specific wear rate decreases. The hard powders filled G–E composite systems exhibit lower wear volume loss and lower specific wear rate as compared to unfilled G–E composite system. The features of worn surfaces of the specimen were evaluated at higher and lower abrading distances at load of 32 N were using scanning electron microscope (SEM) and results indicate more severe damage to matrix and glass fiber in unfilled composite system as compared to hard powder filled composites.     

Processability of PVDF/PMMA blends studied by torque rheometry

The processing characteristic of blends of poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA), in different compositions, were studied by torque rheometry. The polymers were mixed in a batch mixer in proportions of 20, 40, 60 and 80% by weight of PVDF, at 190 °C using rotor speeds of 30, 60 and 100 rpm. The results have shown that the increase of the PMMA content improved the processability of the blends, in spite of an increase of the activation energy of flow. Higher speeds of blending caused a reduction of the homogenization blending times of the blends. The PMMA processing at different speeds studied by parallel plate rheometer showed that a similar behavior and did not affect considerably the degradation of PMMA, according the Carreau model.     

Polyacetal and thermoplastic polyurethane elastomer toughened polyacetal: crystallinity and fracture mechanics

The effect of thermoplastic polyurethane (TPU) elastomer on the melting point and the percentage crystallinity of polyacetal (POM) is studied by differential scanning calorimetry (DSC). Wide angle X-ray diffraction (WAXD) scans of POM, TPU and their blends have been taken and the results indicate that the crystalline structure of POM remains unaffected even after the addition of amorphous TPU. The influence of defects like holes and notches on the ultimate tensile strength has been examined. The resistance to crack initiation (J _c), the resistance to steady state crack propagation (R _p) and the resistance to crack growth at maximum load (R _max) are estimated. The POM/TPU blends display higher crack resistance values than pure POM. The hysteresis energy of blends is determined and is found to increase with TPU content.     

Effect of fiber loading on mechanical and morphological properties of cocoa pod husk fibers reinforced thermoplastic polyurethane composites

In this study, cocoa (Theobroma cacao) pod husk (CPH) fiber reinforced thermoplastic polyurethane (TPU) was prepared by melt compounding method using Haake Polydrive R600 internal mixer. The composites were prepared with different fiber loading: 20%, 30% and 40% (by weight), with the optimum processing parameters: 190 °C, 11 min, and 40 rpm for temperature, time and speed, respectively. Five samples were cut from the composite sheet. Mean value was taken for each composite according to ASTM standards. Effect of fiber loading on mechanical (i.e. tensile, flexural properties and impact strength) and morphological properties was studied. TPU/CPH composites showed increase in tensile strength and modulus with increase in fiber loading, while tensile strain was decreasing with increase in fiber loading. The composite also showed increase in flexural strength and modulus with increase in fiber content. Impact strength was deteriorated with increase in fiber loading. Morphology observations using Scanning Electron Microscope (SEM) showed fiber/matrix good adhesion.     

In situ polymerization preparation of blends of poly(methyl methacrylate) and poly(styrene-co-acrylonitrile)

The in situ polymerization of methyl methacrylate (MMA) with poly(styrene-co-acrylonitrile) (SAN) was studied. The PMMA/SAN in situ polymerization blends obtained were examined by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), tensile tests and scanning electron microscopy (SEM). The blends with compositions of 95/5, 80/20, 70/30, and 60/40 in weight ratios were miscible and had a single phase structure. However, the 90/10 PMMA/SAN in situ polymerization blend obtained was inhomogeneous and had a two-phase structure; polymerization-induced phase separation occurred during the preparation process of the blend. Both tensile strength and elongation at break increase with increasing SAN content up to 30 wt%. The degradation temperature and thermal stability of PMMA increased remarkably on incorporation of SAN up to 30 wt%.     

Influence of graphite filler on two-body abrasive wear behaviour of carbon fabric reinforced epoxy composites

The influence of graphite filler additions on two-body abrasive wear behaviour of compression moulded carbon–epoxy (C–E) composites have been evaluated using reciprocating wear unit and pin-on-disc wear unit under single pass and multi-pass conditions respectively. The carbon fabric used in the present study is a plain one; each warp fiber pass alternately under and over each weft fiber. The fabric is symmetrical, with good stability and reasonable porosity. Abrasive wear studies were carried out under different loads/abrading distance using different grades of SiC abrasive paper (150 and 320 grit size). Graphite filler in C–E reduced the specific wear rate. Further, the wear volume loss drops significantly with increase in graphite content. Comparative wear performance of all the composites showed higher specific wear rate in two-body wear (single-pass conditions) compared to multi-pass conditions. Further, the tribo-performance of C–E indicated that the graphite filler inclusion resulted in enhancement of wear behaviour significantly. Wear mechanisms were suggested and strongly supported by worn surface morphology using scanning electron microscopy.     

挤出次数及相容剂对ABS/PMMA合金性能的影响

用熔融共混的方法制备了丙烯腈-苯乙烯-丁二烯共聚物(ABS)/聚甲基丙烯酸甲酯(PMMA)合金,研究了挤出次数和相容剂对合金性能的影响,采用差示扫描量热法(DSC)测定了ABS/PMMA合金的玻璃化转变温度,用场发射扫描电镜(SEM)观察了材料冲击断口的表面形貌。结果表明,挤出次数对拉伸强度没有明显影响,对冲击强度有小幅度影响;苯乙烯-马来酸酐共聚物(SMA)作为相容剂增加了合金的拉伸强度,降低了合金的韧性。SEM观察表明,PMMA使材料由韧性断裂向脆性断裂转变,SMA对于ABS/PMMA合金的相容性没有明显的改善作用。     

The effect of heat treatment on high temperature mechanical properties of microalloyed medium carbon steel

In the present work, high temperature tensile properties and abrasive wear performance of a microalloyed medium carbon steel has been examined. Tensile and abrasive wear testing were carried out on as-received and heat treated specimens. The research has shown that microalloyed medium carbon steel was susceptible to dynamic strain ageing due to interaction of mobile dislocations and solid atoms, such as carbon and/or nitrogen. The interaction between dislocations and solid atoms at 200–300 °C changes the work hardening rate and contributes to dynamic strain ageing. These interactions also increased abrasive wear resistance of the microalloyed medium carbon steel at 300 °C. Therefore, the inference can be drawn that dynamic strain ageing caused an improvement on abrasion resistance.     

Influence of fiber content on mechanical,morphological and thermal properties of kenaf fibers reinforced poly(vinyl chloride)/thermoplastic polyurethane poly-blend composites

Kenaf (Hibiscus Cannabinus) bast fiber reinforced poly(vinyl chloride) (PVC)/thermoplastic polyurethane (TPU) poly-blend was prepared by melt mixing method using Haake Polydrive R600 internal mixer. The composites were prepared with different fiber content: 20%, 30% and 40% (by weight), with the processing parameters: 140 °C, 11 min, and 40 rpm for temperature, time and speed, respectively. After mixing, the composite was compressed using compressing molding machine. Mechanical properties (i.e. tensile properties, flexural properties, impact strength) were studied. Morphological properties of tensile fracture surface were studied using Scanning electron microscope (SEM). Thermal properties of the composites were studied using Thermogravimetric Analyses (TGA). PVC/TPU/KF composites have shown lower tensile strength and strain with increase in fiber content. Tensile modulus showed an increasing trend with increase in fiber content. Impact strength decreased with increase in fiber content; however, high impact strength was observed even with 40% fiber content (20.2 kJ/m²). Mean while; the 20% and 30% fiber contents showed higher impact strength of 34.9, 27.9 kJ/m²; respectively. SEM showed that there is poor fiber/matrix adhesion. Thermal degradation took place in three steps. In the first step, composites as well as the matrix had a similar stability. At the second step, matrix showed a slightly better stability than the composites. At the last step, composites showed a better stability than the matrix.     

Effect of sequence of nanoclay addition in TPU/PP blends: thermomechanical properties

Nanoclay filled thermoplastic polyurethane (TPU)/polypropylene (PP) blends compatibilized with maleic anhydride grafted polypropylene (MA-g-PP) have been studied with emphasis on sequence of nanoclay addition. In sequence I [TPU(nano)/PP/MA-g-PP], nanoclay was first added to TPU and this nano composite was blended with PP, using MA-g-PP as compatibilizer. In the case of sequence II [TPU/PP(nano)/MA-g-PP], nanoclay was added first to PP and blended with TPU, using MA-g-PP as compatibilizer. These blend systems were evaluated by DSC, FTIR, DMA, SEM, XRD and tensile properties. The results indicated that sequence I imparted greater compatibility to the polymers and better nanoclay dispersion than sequence II. Overall the TPU(nano)/PP/MA-g-PP blend system shows better dispersion than TPU/PP(nano)/MA-g-PP.     

Toughening mechanism of PA1010/ester-based TPU blends

To improve the notched impact strength of polyamide-1010 (PA1010), it was modified with a thermoplastic poly (ester urethane) elastomer (ester-based TPU). The notched impact strength of PA1010/ester-based TPU blends was investigated by using an impact tester and the fracture morphology of PA1010/ester-based TPU blends was investigated by means of SEM. In the impact experiments, it was found that the notched impact strength of the blends is obviously higher than that of pure PA1010, and the fracture surfaces of the blends show a corrugated and oriented structure. The results indicate that the brittle-to-tough transition of the blends occurs when the content of ester-based TPU is 20 wt.% and there is a new toughening mechanism, which is the multi-layer crack extension mechanism, besides the crazing with a shear-yield mechanism in the process of fracture for the blend samples under impact.     

PBT／PMMA共混体系的研究

通过PBT/PMMA、PB/PMMA/PC共混物的拉伸行为、动态力学行为和形态,讨论了PC对PBT/PMMA共混体系的性能及形态的影响。指出PC的存在导致共混物中PMMA的粒径变小,使PMMA对PBT显示出增韧效应,但对PBT-PMMA的相容性无明显影响。     

热塑性聚氨酯/聚己内酯共混物的形状记忆和力学性能

利用简单的熔融共混制备得到不同组分比的热塑性聚氨酯(TPU)/聚己内酯(PCL)共混体系,研究了两相组分比的变化对共混材料相形态、形状记忆性能和力学性能的影响。偏光显微镜观察发现,随着结晶相PCL含量的增加,其逐渐从分散相过渡至连续相再发展为基体相。热性能测试结果表明TPU的加入对PCL的熔融行为影响甚微,整个共混体系基本表现出与PCL一致的熔点。形状记忆性能测试发现共混材料的形状记忆性能表现出明显的组分依赖性,并在组分比为50%/50%性能达到最优(R_r=91%,R_f=96%)。而力学测试结果表明,PCL的加入既不会显著劣化TPU原有的拉伸强度,还能进一步提高其断裂伸长率。     

Structure and properties of melt-processed PVDF/PMMA/polyaniline blends

Ternary blends composed of the matrix polymer poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA) with different proportions of thermally doped polyaniline (PAni) using an alkylated dopant (dodecylbenzenesulfonic acid) (DBSA) were prepared by melt mixing. The effectiveness of these blends was compared with the corresponding binary blends of PVDF or PMMA with PAni–DBSA complex. Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) measurements, thermal analysis by differential scanning calorimetry (DSC) and morphological studies by optical microscopy and scanning electron microscopy (SEM) were carried out to characterize the blends in light of the interactions between their components and on the resulting electrical conductivity. Though a notable dispersion of PAni–DBSA in the PMMA matrix was incurred along with better conductivity with respect to PVDF/PAni–DBSA and PVDF/PMMA/PAni–DBSA blends, the thin films based on PMMA/PAni–DBSA were found to be fragile in nature. However, the presence of PMMA in the ternary blends of PVDF/PMMA/PAni–DBSA provided improved dispersion of PAni–DBSA in the PVDF/PMMA host matrix as compared to PVDF/PAni–DBSA binary blends. An enhancement in the conductivity by about two orders of magnitude at >5 wt% PAni–DBSA was witnessed in the ternary blends than that of PVDF/PAni–DBSA binary blends. Thin films made of ternary blends of PVDF/PMMA/PAni–DBSA also offered superior mechanical properties and flexibility than that of PMMA/PAni–DBSA binary blends due to the contribution of PVDF in the blend.     

Miscibility and shape memory property of poly(vinyl chloride)/thermoplastic polyurethane blends

The miscibility and the shape memory effect of PVC blends with segmented thermoplastic polyurethanes (TPUs), synthesized from diol-terminated polycaprolactone (PCL), hexamethylene diisocyanate, 4,4-dihydroxy biphenyl, were studied. PVC was miscible with PCL segment in TPU and the glass transition temperature of this miscible amorphous domain varied smoothly with composition. When PVC was blended with TPU by the weight ratio of 8/2, the hysterisis in repeated cyclic tensile test was reduced compared with PVC. However, in 6/4 blends, unrecoverable permanent deformation was increased compared with PVC. Dynamic mechanical properties were examined to explain these results.