Processing of Polymers and Polymer Composites In a Microwave Applicator

1990 ◽  
Vol 189 ◽  
Author(s):  
Martin C. Hawley ◽  
Jianghua Wei
Keyword(s):  
Polymer Composites ◽  
Reaction Rates ◽  
Diglycidyl Ether ◽  
Flexural Properties ◽  
Diaminodiphenyl Sulfone ◽  
Epoxy Amine ◽  
Thin Film Technique ◽  
Microwave Applicator ◽  
Heating Mode ◽  
Resonant Heating

ABSTRACTPolymers and polymer composites have been processed In a cylindrical resonant microwave applicator at a frequency of 2.45GHz. Stoichlometric mixtures of two epoxy/amine systems, DGEBA (Diglycidyl Ether of Bisphenol A)/DDS (4,4'-Diaminodiphenyl Sulfone) and DGEBA/mPDA(m-Phenylene Diamine), were microwave and thermally cured Isothermally using a thin film technique. FTIR was used to determine the extent of cure. Increased reaction rates were observed In microwave cure when compared to those of thermal cure. The rate Increase due to microwave effects was much greater for the DGEBA/DDS system than for DGEBA/mPDA. Also, crossply and unidirectional 24-ply and 72-ply graphite/epoxy laminates(AS4/3501-6 prepreg, Hercules Corp.). were processed using microwave radiation. The flexural properties of the microwave processed composites were strongly dependent on the resonant heating mode. Comparable flexural properties were obtained for the unpressurized microwave processed composites and the pressurized autoclave processed composites. Proper controlled-hybrid modes are required to process composites of high mechanical properties. The procedures for obtaining these controlled-hybrid modes are described.

scholarly journals Bisphenol-Free Epoxy Resins Derived from Natural Resources Exhibiting High Thermal Conductivity

Proceedings ◽  
2020 ◽  
Vol 69 (1) ◽  
pp. 18
Author(s):  
Matthias Sebastian Windberger ◽  
Evgenia Dimitriou ◽  
Frank Wiesbrock
Keyword(s):  
Thermal Conductivity ◽  
Natural Resources ◽  
Polymer Networks ◽  
Sio2 Nanoparticles ◽  
Diglycidyl Ether ◽  
Epoxy Compound ◽  
Inorganic Materials ◽  
Limiting Factor ◽  
Epoxy Amine ◽  
Π Stacking

Polymers commonly have low thermal conductivity in the range of 0.1–0.2 W·m−1·K−1, which is a limiting factor for their usage in the course of continuously increasing miniaturization and heat generation in electronic applications. Two strategies can be applied to increase the transport of phonons in polymers: (i) the embedment of thermally conductive inorganic materials and (ii) the involvement of aromatic units enabling anisotropy by π–π stacking. In this study, the thermal conductivity of resins based on bisphenol A diglycidyl ether BADGE and 1,2,7,8-diepoxyoctane DEO was compared. DEO can be derived from pseudo-pelletierine, which is contained in the bark of the pomegranate tree. The epoxy compounds were cured with isophorone diamine IPDA, o-dianisidine DAN, or mixtures of the both diamines. Notably, isophorone diamine is derived from isophorone of which the latter naturally occurs in cranberries. The formulations were produced without filler or with 5 wt.-% of SiO2 nanoparticles. Significantly enhanced thermal conductivity in the range of 0.4 W·m−1·K−1 occurs only in DEO-based polymer networks that were cured with DAN (and do not contain SiO2 fillers). This observation is argued to originate from π–π stacking of the aromatic units of DAN enabled by the higher flexibility of the aliphatic carbon chain of DEO compared to that of BADGE. This assumption is further supported by the facts that significantly improved thermal conductivity occurs only above the glass-transition temperature and that nanoparticles appear to disrupt the π–π stacking of the aromatic groups. In summary, it can be argued that the bisphenol-free epoxy/amine resin with an epoxy compound derivable from natural resources shows favorably higher thermal conductivity in comparison to the petrol-based epoxy/amine resins.

scholarly journals Build-To-Specification Vanillin and Phloroglucinol Derived Biobased Epoxy-Amine Vitrimers

Polymers ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 2645
Author(s):  
Aratz Genua ◽  
Sarah Montes ◽  
Itxaso Azcune ◽  
Alaitz Rekondo ◽  
Samuel Malburet ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Renewable Resources ◽  
Diglycidyl Ether ◽  
Vanillyl Alcohol ◽  
Molecular Architecture ◽  
Covalent Bonds ◽  
Thermoset Resins ◽  
Epoxy Amine ◽  
Reversible Covalent ◽  
Epoxy Matrices

Epoxy resins are widely used in the composite industry due to their dimensional stability, chemical resistance, and thermo-mechanical properties. However, these thermoset resins have important drawbacks. (i) The vast majority of epoxy matrices are based on non-renewable fossil-derived materials, and (ii) the highly cross-linked molecular architecture hinders their reprocessing, repairing, and recycling. In this paper, those two aspects are addressed by combining novel biobased epoxy monomers derived from renewable resources and dynamic crosslinks. Vanillin (lignin) and phloroglucinol (sugar bioconversion) precursors have been used to develop bi- and tri-functional epoxy monomers, diglycidyl ether of vanillyl alcohol (DGEVA) and phloroglucinol triepoxy (PHTE) respectively. Additionally, reversible covalent bonds have been incorporated in the network by using an aromatic disulfide-based diamine hardener. Four epoxy matrices with different ratios of epoxy monomers (DGEVA/PHTE wt%: 100/0, 60/40, 40/60, and 0/100) were developed and fully characterized in terms of thermal and mechanical properties. We demonstrate that their performances are comparable to those of commonly used fossil fuel-based epoxy thermosets with additional advanced reprocessing functionalities.

Analysis of the effect and mechanism of microwave curing on the chemical shrinkage of epoxy resins

2016 ◽  
Vol 29 (10) ◽  
pp. 1165-1174 ◽  
Author(s):  
Xiaochun Wu ◽  
Yingguang Li ◽  
Nanya Li ◽  
Jing Zhou ◽  
Xiaozhong Hao
Keyword(s):  
Epoxy Resins ◽  
Diglycidyl Ether ◽  
Heating Process ◽  
Hydroxyl Groups ◽  
Chemical Shrinkage ◽  
Positron Annihilation Lifetime ◽  
Microwave Curing ◽  
Diaminodiphenyl Sulfone ◽  
Influencing Mechanism ◽  
Lower Tensile Strength

The microwave cure–induced chemical shrinkage of epoxy resins in composite materials was researched in this article. Four kinds of epoxy resins were cured using the microwave and thermal heating process. An improved device containing fiber Bragg grating sensors was applied to accurately measure the chemical shrinkage–induced linear strains in those samples. Experimental results indicated that the chemical shrinkage of diglycidyl ether of bisphenol A (DGEBA)/polyetheramine (PEA) and tetraglycidyl diaminodiphenylmethane/4,4′-diaminodiphenyl sulfone epoxy resins was significantly reduced by microwave curing, and the reductions about 37.1 and 38.4% were achieved compared with the thermal-cured counterparts. However, the chemical shrinkage of the thermal- and microwave-cured samples was almost the same for DGEBA/methyl tetrahydrophthalic anhydride and DGEBA/dicyandiamide epoxies. In order to analyze the influencing mechanism of microwaves on the chemical shrinkage, the chemical structure of various samples was characterized by using Fourier-transform infrared spectroscopy, and the free volume was measured by positron annihilation lifetime spectrometer. It was found that microwaves can greatly decrease the contents of hydroxyl groups in epoxy resins, leading to the reduction of the chemical shrinkage. Furthermore, the mechanical properties of both microwave- and thermal-cured DGEBA/PEA epoxies were studied, and the results showed that the microwave-cured specimens have a higher impact strength but a lower tensile strength.

scholarly journals Flexural Properties of Chopped Kenaf and Carbon Fibre Reinforced Polymer Composites Embedded with Carbon Nanotubes

2019 ◽  
Vol 8 (4) ◽  
pp. 6842-6846
Keyword(s):  
Carbon Nanotubes ◽  
Flexural Strength ◽  
Carbon Fibre ◽  
Polymer Composites ◽  
Flexural Properties ◽  
Specimen Thickness ◽  
Reinforced Polymer ◽  
Roll Mill ◽  
Carbon Fibre Reinforced Polymer ◽  
Fibre Reinforced Polymer

An experimental study was performed to investigate the flexural behaviour of chopped kenaf and carbon fibre reinforced polymer composites embedded with carbon nanotubes (CNT). The fibre content in the composites was 10 wt.% with three different CNT loadings, which were 0.5wt.%, 1.0wt.%, and 1.5wt.%. The CNT were dispersed in the epoxy resin using the mechanical stirrer and three-roll mill machine and mixed with the chopped fibres before being poured into the designated mould. Three-point bending tests were conducted with a specimen thickness and width of 4 mm and 10 mm, respectively, and a standard specimen length of 20% longer than the support span. The flexural test results showed that the chopped carbon fibre reinforced polymer (CFRP) with 0.5wt.% CNT exhibited the highest flexural strength and modulus (42 MPa and 2.9 GPa, respectively) compared to other composites with 1.0wt.% and 1.5wt.% CNT loading. The chopped kenaf fibre reinforced polymer (KFRP) composite with 0.5wt.% CNT loading showed the highest increase in the flexural strength and modulus, at 30 MPa and 2.8 GPa, respectively. Hence, it was concluded that the addition of CNT improved the flexural properties and 0.5 wt.% CNT was the ideal loading to enhance the flexural properties of chopped fibre-reinforced polymer composites.

Studies of Mechanical Properties of Multiwall Nanotube Based Polymer Composites

2014 ◽  
Vol 5 (3) ◽  
Author(s):  
A. K. Gupta ◽  
S. P. Harsha
Keyword(s):  
Mechanical Properties ◽  
Polymer Composites ◽  
Composite Structures ◽  
Secondary Reinforcement ◽  
Chemical Vapor ◽  
Carbon Composite ◽  
Diglycidyl Ether ◽  
Two Phase ◽  
Three Phase ◽  
Structural Applications

The two phase polymer composites have been extensively used in various structural applications; however, there is need to further enhance the strength and stiffness of these polymer composites. Carbon nanotubes (CNTs) can be effectively used as secondary reinforcement material in polymer based composites due to their superlative mechanical properties. In this paper, effects of multiwall nanotubes (MWNTs) reinforcement on epoxy–carbon polymer composites are investigated using experiments. MWNTs synthesized by chemical vapor deposition (CVD) technique and amino-functionalization are achieved through acid-thionyl chloride route. Diglycidyl ether of bisphenol-A (DGEBA) epoxy resin with diethyl toluene diamine (DETDA) hardener has been used as matrix. T-300 carbon fabric is used as the primary reinforcement. Three types of test specimen of epoxy–carbon composite are prepared with MWNT reinforcement as 0%, 1%, and 2% MWNT (by weight). The resultant three phase nanocomposites are subjected to tensile test. It has been found that both tensile strength and strain at failure are substantially enhanced with the small addition of MWNT. The analytical results obtained from rule of mixture theory (ROM) shows good agreement with the experimental results. The proposed three phase polymer nanocomposites can find applications in composite structures, ballistic missiles, unmanned arial vehicles, helicopters, and aircrafts.

scholarly journals Biodegradation in simulated soil of HDPE/pro-oxidant/rice husk composites: application in agricultural tubes

2018 ◽  
Vol 23 (4) ◽  
Author(s):  
Cristiano Cunha Costa ◽  
George Ricardo Santana Andrade ◽  
Luís Eduardo Almeida
Keyword(s):  
Mechanical Properties ◽  
Polymer Composites ◽  
Rice Husk ◽  
Agricultural Waste ◽  
Degradation Process ◽  
Flexural Properties ◽  
Degradation Tests ◽  
Intense Light ◽  
Mechanical Tensile ◽  
Uv Range

ABSTRACT The use of agricultural waste, such as rice husk (RH), for the production of cheap and eco-friendly polymer composites has emerged as a promising field of interest. The aim of this work was the preparation of highdensity polyethylene (HDPE)-based composites reinforced with rice husk and an organic pro-oxidant (EG15) for the production of seedlings tubes. Photodegradation and degradation tests in simulated soil were performed for 90 and 180 days in order to study the decomposition of these composites. The SEM and OM images suggest that degradation of the composites samples was more extensive than the pure HDPE samples, probably because the composites present intense light absorption in the UV range, facilitating the degradation process even before biodegradation begins. In addition, after introducing RH particles in the polymeric matrix, the mechanical tensile and flexural properties, experienced significant changes, suggesting that the RH particles were homogeneously dispersed throughout the polymer matrix. Finally, the results have demonstrated that HDPE, RH, and EG15 are attractive materials for the design of polymeric composites for the production of seedlings tubes with excellent mechanical properties, being also easily decomposed in the environment once discarded.

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