Microwave Induced Degradation of Glass Fiber Reinforced Polyester for Fiber and Resin Recovery (original) (raw)
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Microwave Induced Degradation of Glass Fiber Reinforced Epoxy for Fiber Recovery
2015
A solvolysis process to depolymerize the resin in glass fiber reinforced composites and recover the glass fibers has been investigated using microwave induced irradiation. The depolymerization was carried out in HNO 3 with concentrations in the range of 1M-7M and in KOH with concentrations ranging from 1M-3.5M. In case of 3.5 M HNO 3 , 100 % resin removal at 208°C and recovery of pristine glass fibers without damage on the surface was achieved. Furthermore, recovery of the monomer phthalic acid was obtained using HNO 3. Decreased level of depolymerization was observed using KOH at concentrations ranging from 1-3.5M. Maximum 63 % resin removal was achieved using 1 M KOH and the resin removal efficiency decreased at higher KOH concentrations (3.5M). The glass fiber surfaces were damaged at both concentrations with more pronounced damages using 3.5M KOH. It was not possible to recover monomers using KOH.
Fiber Reinforced Polyester Resins Polymerized by Microwave Source
Journal of Materials Engineering and Performance, 2007
Polyester resin based composite materials are widely used in the manufacture of fiberglass boats. Production time of fiberglass laminate components could be strongly reduced by using an intense energy source as well as microwaves. In this work a polyester resin was used with 2% by weight of catalyst and reinforced with chopped or woven glass fabric. Pure resin and composite samples were cured by microwaves exposition for different radiation times. A three point bending test was performed on all the cured samples by using an universal testing machine and the resulting fracture surfaces were observed by means of scanning electron microscopy (SEM). The results of mechanical and microscopy analyses evidenced that microwave activation lowers curing time of the composite while good mechanical properties were retained. Microwaves exposition time is crucial for mechanical performance of the composite. It was evidenced that short exposition times suffice for resin activation while long exposure times cause fast cross linking and premature matrix fracture. Furthermore high-radiation times induce bubbles growth or defects nucleation within the sample, decreasing composite performance. On the basis of such results microwave curing activation of polyester resin based composites could be proposed as a valid alternative method for faster processing of laminated materials employed for large-scale applications.
Scientific Research and Essays, 2012
Depolymerization of polycarbonate (PC) is one of the important issues in environment especially in industry field. In this project degradation of PC is done by employing the hydrolysis method using microwave irradiation. PC degradation was carried out under constant amount of tetrahydrofuran (THF) as co-solvent and by using various amount of water (H2O) as main solvent and different concentration of sodium hydroxide (NaOH) as catalysts in a microwave reactor for low power and different time. The solid main product bisphenol A (BPA) was analyzed by FTIR and HPLC. It was found that PC degradation is favored by increasing amount of H2O, concentration of NaOH and time duration of process. Complete depolymerization was found to occur in 12.5 min when the amount of water was 3.5 g and concentration of NaOH was 0.5 g at 110°C. Key words: Hydrolysis, polycarbonate, microwave irradiation, bisphenol A.
Influence of polymerization cycle in properties of acrylic resin polymerized by microwave energy
Revista Odonto Ciência
Objective: The purpose of this study was to evaluate the physicochemical properties of acrylic resin polymerized by microwave energy in short cycle of polymerization.Methods: Two brands (Classico and VIPI) and two cycles were evaluated (manufacturer cycle and short cycle). The characteristics and properties as degree of conversion, glass transition temperature, impact strength-Izod, Knoop hardness, swelling degree, soluble fraction, specific mass, water sorption and solubility were evaluated.Results: Glass transition temperature, hardness, specific mass, soluble fraction and solubility were statistically significant between cycles and brands (p<0.05). Water sorption showed no difference between cycles (p>0.05) and impact strength presented difference between brands in short cycle (p<0.05). Acrylic resin polymerized by microwave energy with manufacturer cycle presented no difference in physicochemical properties between evaluated brands. Conclusion: The short cycle of polyme...
Glass Fibres Recovered by Microwave Pyrolysis as a Reinforcement for Polypropylene
Polymers and Polymer Composites, 2013
Glass fibre composites were recycled by microwave pyrolysis. The glass fibres recovered were evaluated as a reinforcement agent for polypropylene (PP). Samples were prepared with a micro-compounder and the resulting compounds were evaluated with tensile testing, flexural testing, Charpy impact testing and scanning electron microscopy (SEM). The adhesion between fibre and glass was relatively poor, and an attempt was made to improve it. Various coupling agents were evaluated, in addition to the use of maleic anhydride-grafted PP (MA-PP). Tests showed that MA-PP had a relatively strong effect on the mechanical properties.
2.45 GHz Microwave Processing and Its Influence on Glass Fiber Reinforced Plastics
Materials
During the production of fiber-reinforced composite materials, liquid resin is introduced into the fiber material and cured, i.e., hardened. An elevated temperature is needed for this curing. Microwave curing of composites has been investigated for some time, but it has mostly been done using small domestic or laboratory equipment. However, no investigation has been carried out using an industrial-sized chamber-microwave for glass fiber-reinforced plastic (GFRP). Here, we show that microwave curing produces laminates of the same quality as oven-cured ones. The study shows that, if the process is done right, GFRP samples can be produced with an industrial scale microwave. Even if not fully cured, microwave samples show a glass transition temperature measured with DMA (T g−DMA) that is comparable to the T g−DMA according to the proposed cure cycle on the data sheet. Specific microwave-cured configurations show better inter-laminar shear strength than oven specimens. The results show that microwave-based heat introduction can be a beneficial curing method for GFRP laminates. A microwave-optimized process is faster and leads to better mechanical properties.
Composites Part A: Applied Science and Manufacturing
Accelerated curing of high performance fibre-reinforced polymer (FRP) composites via microwave heating or radiation, which can significantly reduce cure time and increase energy efficiency, has several major challenges (e.g. uneven depth of radiation penetration, reinforcing fibre shielding, uneven curing, introduction of hot spots etc). This article reviews the current scientific challenges with microwave curing of FRP composites considering the underlying physics of microwave radiation absorption in thermoset-matrix composites. The fundamental principles behind efficient accelerated curing of composites using microwave radiation heating are reviewed and presented, especially focusing on the relation between penetration depth, microwave frequency, dielectric properties and cure degree. Based on this review, major factors influencing microwave curing of thermoset-matrix composites are identified, and recommendations for efficient cure cycle design are provided.
Microwave Radiations for Heat-Setting of Polyester Fibers
Journal of Engineered Fibers and Fabrics, 2009
The use of radio and microwave frequency is gaining importance for industrial applications such as heating, drying, and other processing. The most important advantage of using microwave is that it is non-contact or localized heating and the heat is produced within the material. This can be much more effective than indirect heating where the heat propagation is by heat conduction through the material. We have been investigating the influence of microwave radiation on different fibers for the last few years. In the present investigation we used microwave frequency of 2450 MHz to investigate its effect on polyester fibers. The polyester fibers were heat set in air as well as a liquid, which acted as a lossy substances. The liquid was chosen on the basis of earlier experiments, which showed the maximum effect. A comparative study was also carried out using conventional heating in silicone oil. Using the method of X-ray Diffraction (XRD) we calculated the changes in % crystallinity and o...
MICROWAVE CURE PROCESSED POLYMER COMPOSITES - A REVIEW
Polymer composites by and large found suitable for many specific applications in the filed of electrical, electronics, marine, aerospace and microelectronics. Thus a new technique for processing polymer composites has been explored and one such is microwave curing. The particulate filled epoxy composites are much preferred for many applications and the curing of such thermoset systems are of much important and should be efficient with reduced time cycle. In that regard the microwave curing becomes an alternative curing technique to meet the demand of these composites. Thus this paper attempts to describe the advancement occurred for past few years illustrating the different properties and their behaviour when these composites are cured with microwave techniques.
Polymers
The work is devoted to the creation of an energy-saving microwave technology of composite materials for thermal insulation based on an inorganic polymer—liquid glass—and the establishment of the formation patterns of their structure and properties, depending on the parameters of microwave radiation. Due to volumetric heating and the mechanism of "non-thermal" action of microwave radiation on processed objects, the duration of their heating is significantly reduced, and the performance properties of products are improved due to the modification of the structure of the liquid glass matrix under the influence of its irradiation with this type of energy. In the course of the research, the relationship between the processing conditions and the obtained properties of heat-insulating materials was established. The prospects of using the microwave electromagnetic field in the production of new building materials, expanding their range, and improving quality and competitiveness are...