Chi-Yuan Huang

The EMI shielding effectiveness of PC/ABS/nickel-coated-carbon-fibre composites

Abstract The aim of this investigation is to prepare polycarbonate (PC)/acrylonitrile–butadiene–styrene (ABS)/nickel-coated-carbon-fibre (NCF) conductive composites possessing electromagnetic interference (EMI) shielding effectiveness (SE). A series of PC/ABS/NCF composites were prepared by the melt blending method. The various compositions of PC/ABS were 90/10, 70/30, 50/50, 30/70 and 10/90 percent by weight. The results indicate that the processability of PC/ABS/NCF could be improved by increasing the ABS content and that the mechanical strength of PC/ABS/NCF could be enhanced by adding NCF. Adding a higher amount of ABS in the PC/ABS/NCF composite could markedly improve the processability of the composites effectively. The NCF mean fibre length of PC/ABS/NCF also increased with increasing amounts of ABS. The best EMI shielding effectiveness of all PC/ABS/NCF is about 47 dB. However, for the reason of phase separation between PC and ABS, the oxygen could diffuse into the PC/ABS matrix and then reacted with Ni to form oxides little by little as heat treatment. As the oxidized layer on the filler increases the specific resistance, the EMI SE values markedly decrease with increasing heat treatment time.

Study on the Crystallization, Miscibility, Morphology, Properties of Poly(lactic acid)/Poly(ε-caprolactone) Blends

A series of blends of poly(lactic acid) (PLA) and poly(ϵ-caprolactone) (PCL) with different mass ratio were prepared by means of the melt blending method to study their crystallization, miscibility, morphology, and thermal and mechanical properties. The result of DSC tests showed that the melting temperatures of PLA and PCL shifted toward each other, and that the largest shift appeared at the PLA70PCL30 blend. This result reveals that the PLA70PCL30 blend gives the strongest interaction intensity among the blends. Combined the result of dynamic mechanical analysis and SEM morphologies, it was found that PLA and PCL form a partial miscible blend, in which an amount of amorphous PCL (amorphous PLA) is dissolved in the PLA-rich phase (PCL-rich phase), leading to a depression of the Tg. value. The polarized optical micrographs showed that PCL can serve as a nucleating agent to promote PLA crystallization in the PLA/PCL blend. Moreover, the PLA70PCL30 blend gave the largest growth rate of PLA spherulite. Finally, the mechanical property of PLA/PCL blends indicated that PLA can easily be tuned from rigid to ductile by the addition of PCL.

Studies on processing parameters and thermal stability of ENCF/ABS composites for EMI shielding

Electroless nickel coated carbon fibers (ENCF) were blended with acrylonitrile-butadiene-styrene (ABS) to prepare composites for electromagnetic interference (EMI) shielding. The effects of processing parameters, such as additives, temperature, and fiber loading amount, on EMI shielding effectiveness (SE) were researched. The thermal stability of EMI SE of ENCF/ABS composites was tested by heat treating composites in a drying oven at 60°C, and SE was measured at an interval of one week to consider the degradation of SE. The best SE of ENCF/ABS composites could be reached was 44 dB at optimum processing parameters. The thermal stability of ENCF/ABS composites for EMI shielding was steady without obvious degradation after 60°C heat treatment for five weeks.

The effect of attached fragments on dense layer of electroless Ni/P deposition on the electromagnetic interference shielding effectiveness of carbon fibre/acrylonitrile–butadiene–styrene composites

The high-coating-thickness electroless nickel carbon fibre (HENCF) with the designed structure which is composed of attached fragments on a dense layer has been fabricated. Owing to the lubricating behaviour resulting from the attached fragments, HENCF can absorb most of the mechanical energy to avoid the fibre been broken off when they are compounded with plastics. The average aspect ratio of the HENCF, therefore, increases significantly. Meanwhile, nickel/phosphorous (Ni/P) particles or flakes detached from the attached fragments of electroless nickel-coated carbon fibres (ENCF) are distributed uniformly in the zone between fibres and polymers; hence, a compact conductive network in the composite matrix is formed. Consequently, the mechanical properties and electromagnetic interference (EMI) shielding effectiveness (SE) are greatly improved. In addition, if the fibres are immersed into a dilute polymer solution immediately after the electroless plating processes, the mechanical properties and EMI SE of those conductive composites will be enhanced. The EMI SE of the composites can be over 50 dBm.

Effect of plasma treatment on the AAc grafting percentage of high-density polyethylene

Abstract Argon (Ar) plasma pretreated high-density polyethylene (PHDPE) was grafted with acrylic acid (AAc-g-PHDPE) using benzoyl peroxide (BPO) as an initiator and alcohol as a solvent. Effects of plasma treatment time, plasma power, and storage time on CO/CO ratio of PHDPE were studied. Effects of initiator concentration and reaction time on percent grafting were also studied. In this study, the authors used electron spectroscopy for chemical analysis (XPS) to measure the maximum CO/CO ratio of PHDPE, except that the maximum peroxide concentration of PHDPE was measured by 1,1-diphenyl-2-picryhydrazyl measurement method. Furthermore, the PHDPE was susceptible to further surface modification by thermal-induced graft copolymerization with a vinyl monomer, such as AAc and used BPO as initiator. The grafting percentage of AAc-g-PHDPE was from 10% without BPO initiator to 25% with BPO 1×10 −4 M. The plasma power and plasma treatment time affected not only the surface composition of treated film but also the grafting percentage. As AAc was grafting in alcohol solution, the carboxylic acid will be formed and an overlapped carboxylate ion.

The effect of plasma surface modification from a rotary plasma reactor on the styrene grafting onto a polypropylene surface

In this investigation, the influence of an initiator, benzoyl peroxides (BPO), plasma pretreatment and grafting time of the styrene (St) grafting onto the surface of polypropylene (PP) were studied. At first, the PP pretreated by rotary glow discharge argon (Ar) plasma (PPP) and then styrene was grafted onto the PPP by using a thermal-induced grafting method with or without adding an initiator (BPO). It was found that plasma pretreatment was useful for grafting a vinyl monomer onto the surface of PPP. The ATR-FTIR spectra showed that adding an initiator and plasma pretreatment possessed a synergistic effect on the styrene grafting co-polymerization. ATR-FTIR spectra also showed that the grafting degree of styrene was increased with increasing grafting time. However, long-term plasma treatment was disadvantageous for grafting styrene onto the PPP, resulting from surface cross-linking. From SEM, a number of star-polygon structures can be found on the styrene-grafted PPP surface. This is because the amorphous region of the PP spherulite structure was etched by Ar plasma ion and re-appeared after grafting PS. The spherulite of PP could be revealed by grafting styrene onto the surface of PPP and its size could be estimated by SEM. In this investigation, the spherulite size of PP ranges between 20 and 30 μm.

Effect of plasma treatment on the degree of AAm grafting for high-density polyethylene

Abstract The aim of this article was to determine a suitable method and optimal conditions for grafting of acrylamide (AAm) monomer onto the surface of high-density polyethylene (HDPE). We studied argon plasma treatment of HDPE (PHDPE) and AAm graft copolymerization (AAm-g–PHDPE) using thermal induction with or without adding an initiator, benzoyl peroxide (BPO) [AAm-g (BPO)–PHDPE]. The 1,1-diphenyl-2-picrvlhydrazyl (DPPH) method was adopted to estimate the concentration of peroxide, and consequently the appropriate plasma treatment conditions were determined according to its optimal concentration. ATR-FTIR spectroscopy and ESCA analysis were used to evaluate the degree of grafting copolymerization. The maximum degree of grafting was 0.55 and 2.41 as evaluated by total-reflectance Fourier-transform IR (ATR-FTIR) spectroscopy and electron spectroscopy for chemical analysis (ESCA), respectively. The degree of grafting shows similar trends by ATR-FTIR and ESCA analysis and the optimal grafting time is 4 h. The result also shows that the degree of grafting is also affected by the plasma treatment time. DPPH measurements showed that the maximum peroxide introduced onto HDPE sheets by plasma treatment at 40 W for 3 min and air exposure for 1 h is 5.2×10 −8 mol cm −2 . In this investigation, the best graft copolymerization conditions for HDPE are plasma treatment at 40 W for 3 min and thermally induced grafting for 4 h with an initiator (2×10 −3 M).

The effect of interface modification between POM and PTFE on the properties of POM/PTFE composites

A plasma technique was applied to modify the surface of polytetrafluoroethylene (PTFE) fiber to improve the compatibility between PTFE and polyacetal (POM). This technique used argon (Ar) plasma to treat PTFE fiber first and then grafting the fiber with acrylic acid (AAc) by peroxidation. The Ar plasma-treated PTFE (PPTFE) fiber and AAc-grafted PPTFE (AAc-g-PPTFE) fiber were added into POM to increase the wear resistance and to decrease the friction coefficient of POM. The variables of the experiments were plasma treatment time, monomer concentration of AAc, and grafting time. The graft copolymer was characterized by Fourier transform infrared (FTIR) spectroscopy. The stress–strain behavior, impact strength, Taber wear factor, friction coefficient, and morphology of composites were also investigated. The properties of POM/PTFE composites could be successful modified by surface modification of PTFE in this investigation. The impact strength of POM/AAc-g-PPTFE composites was more than twice of that of POM/PTFE composites. The Taber wear factor and friction coefficient of POM/AAc-g-PPTFE composites decreased markedly.

The effect of reprocessing on the emi shielding effectiveness of conductive fibre reinforced ABS composites

Abstract In this investigation, the acrylonitrile-butadiene-styrene copolymer (ABS) was used as the matrix. Ni-coated conductive carbon fibre (NCF) and conductive carbon fibre (CF) were used as the conductive fillers. For processing, a Twin-Screw Extruder (TSE) and the Brabender Plasti-Corder were used here for compounding composites. The fibre length of composites which were compounded by the twin screw extruder were below the critical length, 200 μm. Thus, the tensile strength and modulus were not increased by adding fibres. At the same time, the conductive fibre cannot form a conductive network. In this case, the shielding effectiveness (SE) value of composites was 0 decibel (dB). But, when the composites were compounded by the Brabender, the fibre length was above critical length, 200 μm, even after three processings. The maximum SE value of conductive composites was 47 dB. The SE values of composites decreased with increasing the number of processing cycles. The viscosity of composites decreased with increasing the number of processing cycles. In addition to the polymer chain being scissored, the short fibre length was another reason. SEM shows that the interfacial adhesion between NCF and ABS was not so good. The interfacial adhesion between ABS and CF was better than that of between ABS and NCF.

Ultra-thin Cr 2 O 3 well-crystallized films for high transmittance APSM in ArF line

Ultra-thin Cr2O3 well-crystallized thin films are deposited on UV grade fused sifica substrates and Si wafers by using r.f. reactive unbalanced magnetron sputtering from a Cr metal target in an atmosphere of Ar and O2 at 350 °C. The optical constants of such thin films were found to be a sensitive function of oxygen-to-argon flow rate ratio. At the ratio of 0.2, a Cr2O3 well-crystallized thin film with appropriate refractive index and extinction coefficient at a wavelength of 365 nm can be used as attenuated phase-shifting mask (APSM) blank as well as being good for inspection. The simulated thickness range of a Cr2O3 well-crystallized thin film was found to be between 28.2 and 30.3 nm. This meets the optical requirements for high transmittance APSM (HT-APSM) with a transmittance of 18-20% at 193 nm for the pattern fabrication and with transmittance less than 50% at 365 nm for the mask inspection. One such Cr2O3 well-crystallized thin film that satisfies the optical requirements was fabricated.