Retention Of Tensile Properties Research Articles

Tensile behavior of angle ply carbon reinforced PPS laminates under severe thermal aggressions: Homogeneous and heterogeneous temperature conditions

AbstractThis study explores the effects of critical temperature conditions on carbon fiber‐reinforced Poly Phenylene Sulfide (PPS) laminates, focusing on the coupling between thermal and mechanical behaviors. The thermo‐mechanical behavior of angle‐ply laminates is examined under both homogeneous (thermal decomposition and deformation/damage) and heterogeneous (fire) conditions following three primary objectives: (i) Investigate the impact of temperature distribution on the formation of porosities within the composite, considering their significance in thermal transfer and stress concentration—(ii) Evaluate the changes in residual mechanical behavior and properties under tension due to thermally‐induced damage—(iii) Improve the understanding of the interactions between severe thermal exposures and the mechanical behavior. X‐ray tomographic analyses and tensile tests were conducted to achieve these goals. Porosities resulting from thermal damage are identified as a key factor affecting the structural integrity of C/PPS laminates for high‐temperature applications. Mechanical testing reveals that the porosity content significantly reduces the tensile properties (axial stiffness and strength). Under homogeneous temperature conditions, the decrease in the tensile properties is significant up to Tonset (465°C) from which both the axial strength and stiffness dramatically decrease by −75 and −50%, respectively. As exposed to a kerosene flame during 60 s, corresponding to an aggression of 115 kW/m2 on one face of the laminates, the retention of the residual tensile properties remains good (−12% and −22% in stiffness and strength respectively), despite the dramatic decomposition of the polymer matrix. This can be explained from the stress redistribution from the exposed to the back face, and from the role of thermal insulator played by porosities.Highlights Carbon fibers/PPS laminates were subjected to severe thermal aggressions The formation of thermally‐induced porosities is studied A homogeneous aggression significantly decrease the tensile properties (−75%) Once the PPS matrix is severely decomposed, the load transfer is not possible After a 60 s flame exposure, the retention of tensile properties is good (−20%)

About the influence of high temperature or fire testing conditions on the tensile behavior of carbon reinforced poly phenylene sulfide laminates

This study aims to investigate the thermo-mechanical coupling in carbon fibers reinforced Poly Phenylene Sulfide (PPS) laminates subjected to critical temperature conditions. In order to dissociate the physical phenomena (degradation/decomposition on the one hand and deformation/damage mechanisms on the other hand) at play in quasi-isotropic laminates (fiber-dominated mechanical behavior), homogenous and fire testing conditions (heterogenous) were considered with or without mechanical loading. X-Ray tomographic and fractographic analyses were conducted to identify the role played by porosities formation (resulting from thermally induced deformations and damages) on the structural bearing capabilities of C/PPS laminates to be used in high-temperature environments. Under high temperature conditions (homogenous temperature distribution), the retention of tensile properties is not well preserved as the axial stiffness and strength decrease of 50% and 75%, respectively. Under fire conditions (heterogenous temperature distribution), the degradation of tensile properties is more dramatic with an 80% decrease.

The use of diisopropyl xanthogen polysulfide as a potential accelerator in efficient sulfur vulcanization of natural rubber compounds

AbstractWith the emerging concerns on the use of nitrosamine evolving accelerators, safer alternatives are desirable for the rubber industry. In the present study, cure characteristics, physicomechanical properties, crosslink density, aging, dynamic mechanical, and thermal properties of vulcanizates prepared with two nitrosamine safe binary accelerator systems containing diisopropyl xanthogen polysulfide (DIXP) and tetrabenzyl thiuram disulfide (TBzTD), and DIXP and dibenzyl dithiocarbamate (ZBeC) were investigated for efficient sulfur vulcanization of natural rubber (NR) compounds. Synergistic effect in both cure and physicomechanical properties was observed for all the combinations of the two accelerator systems. The composition containing DIXP with a lower loading (0.6 phr) of TBzTD, and ZBeC, demonstrated the highest technological performance. Retention of tensile properties on oxidative aging was highest for the vulcanizate prepared with DIXP/TBzTD (1.4/0.6). Dynamic mechanical and thermogravimetric analysis further confirmed the crosslink density and thermal stability of the network structure of the binary systems. In overall, DIXP shows the potential to be used as a safer accelerator in the manufacture of appropriate dry NR‐based rubber products.

Hierarchical crystallization strategy adaptive to 3-dimentional printing of polylactide matrix for complete stereo-complexation

A novel strategy adaptive to 3D printing of PLA matrix for complete stereo-complexation was designed. Stereo-complexation has been demonstrated for its effectiveness in simultaneously improving aqueous stability and heat resistance of PLA. However, current techniques could not be directly incorporated into 3D printing of stereo-complexed PLA since stereo-complexed crystallites are easily formed before printing. High printing temperatures are thus required but decompose PLA materials at the same time. The hypothesis for this research is that controllable hierarchical crystallization in three thermal processes, the filament preparation, 3D printing and post annealing, could ensure feasibility of the strategy and a 100% stereo-complexation level in PLA matrices. Effects of extrusion, ambient and annealing temperatures on material structures were analyzed via WAXD, DSC and DMA. Resistance to hydrolysis and heat of the 3D printed PLA matrix was evaluated under practical conditions. It was showed that homo-crystallites anchored molecular chains of PLA during the post-annealing process for a high retention of tensile properties, while stereo-complexed crystallites provided stronger intermolecular interactions for improved hydrolytic and thermal resistance. This novel strategy via incorporating controlled hierarchical crystallization into 3D printing would enrich the fabrication and exploration of high-performance 3D printed PLA materials.

Enhanced mechanical performance via laser induced nanostructure formation in an additively manufactured lightweight aluminum alloy

To date, the primary focus of metal additive manufacturing (AM) research has been the development of strategies for fabricating complex architectures, reducing internal stress and optimizing microstructure. Traditional Al alloys have presented further challenges in this effort due to solidification cracking and complex laser coupling dynamics. To overcome these limitations, identification of novel alloys that exploit the rapid solidification conditions inherent in laser-based AM is required. In this work, laser-induced melting of an Al-8Ce-10Mg alloy is revealed to generate a nanoscale microstructure which results in improved hardness, tensile strength, and mitigated solidification cracking (e.g., hot tearing) in single laser tracks in as-cast material and laser powder bed fusion (LPBF)-fabricated components. In situ X-ray imaging shows the nanostructure arises from laser-induced melting of intermetallic particles embedded into the alloy during casting and then rapid resolidification of the molten material in ~ 400 µs. The formed Ce-rich nanostructures are highly resistant to thermal coarsening at 300 °C, as confirmed by microscopy and retention of tensile properties. These results pave the way for development of AM-specific Al alloys that possess the ability to form mechanically favorable nanostructures in fabricated components due to the rapid cooling inherent in LPBF.

Mode of dipentaerythritol stabilization during thermo-oxidative aging of glass fibre reinforced PA66

Thermo-oxidative aging of dipentaerythritol (DPE) stabilized, glass fibre reinforced PA66 compounds was studied at 200°C. The influence of DPE as a thermo-oxidation stabilizer on the retention of tensile properties, molecular weight, crystallinity, oxidized layer thickness as well as the specimen surface and fracture morphology was analysed. Moreover, the impact of DPE on the intrinsic humidity inside the test specimens before aging was examined due to its hygroscopic behaviour. The reduction of the extractable amount of DPE from test granules over the aging time proved the existence of chain extension or crosslinking reactions between the polyamide or its degradation products and DPE. Whereas DPE improves the retention of mechanical characteristics during aging only slightly, the combination of DPE and glass fibres reaches retention of mechanical characteristics above 50 % after 1000 h of aging at 200°C in air. DPE raises the intrinsic humidity during processing and before aging resulting in an increase of PA66 degradation during processing and in the first aging phase due to additional hydrolysis. Both the ensuing shorter chain length and water-induced post-crystallisation give rise to higher crystallinity after processing, increasing the oxygen diffusion limitation which results in slower thermo-oxidation. In addition, DPE accelerates the formation of the oxidized layer on the PA66 surface but slows down its growth during the later aging phase.

Enhanced mechanical properties of radiation vulcanized natural rubber latex by using t-butyl hydroperoxide

The mechanical properties of both radiation (RVNRL) and peroxide vulcanized natural rubber latex (PVNRL) are low when compared to sulphur prevulcanized natural rubber latex (SVNRL). This paper deals with the effect of peroxide on the mechanical properties of radiation vulcanized NR latex film. Here, n-butyl acrylate (n-BA) was used as sensitizer and t-butyl hydroperoxide (t-BHPO) as co-vulcanizing agent during irradiation. It was found that the addition of t-BHPO is more practical method to reduce the vulcanization dose. Thermal ageing study showed that the best retention in tensile properties was shown by RIPV vulcanizates.

Effect of Maleic Anhydride Grafted Ethylene Vinyl Acetate Compatibilizer on the Mechanical, Thermal Properties and Weathering Resistance of Polyamide 11/Bamboo Fiber Composite

In this research, short bamboo fiber (BF) has been used as filler in the fabrication of the composite based on polyamide 11 (PA11) by melt-mixing method. In order to improve the compatibility between BF and PA11, maleic anhydride grafted ethylene vinyl acetate copolymer (EVAgMA) was introduced into the composite preparation process. The effect of EVAgMA contents on mechanical, thermal or weathering resistant properties of the composites was investigated. In the presence of the EVAgMA, the tensile strength, impact strength and flexural modulus of composites showed the improvement in comparison to without compatibilizer. Differential scanning calorimetry (DSC) analysis indicated that the melting temperature of composites did not depend on the EVAgMA contents, while its fusion heat (ΔHm) decreased with increasing EVAgMA contents. Dynamic mechanical thermal analysis (DMTA) evaluated the role of EVAgMA on the enhancement of composites’s storage modulus (G′) in the glassy plateau and the interaction between BF and PA11 matrix. After 840 hours of accelerated weathering test, the composites using EVAgMA were decomposed faster than that of neat PA11 and PA11/BF composite. This result was also agreed with the observation of scanning electronic microscopy (SEM) images and the change of carbonyl index (CI). However, the retention of tensile properties of PA11/EVAgMA/BF composites is higher than that of PA11/BF composite.

Tunable Structure and Properties of Segmented Thermoplastic Polyurethanes as a Function of Flexible Segment.

Segmented thermoplastic polyurethanes (PUs) were synthetized using macrodiols with different functional groups (carbonate, ester, and /or ether) as a segment with a molar mass of 1000 and 2000 g/mol, and 4,4’-diphenylmethane diisocyanate (MDI) and 1,4-butanediol as a rigid segment. The polyurethanes obtained reveal a wide variation of microphase separation degree that is correlated with mechanical properties and retention of tensile properties under degradation by heat, oil, weather, and water. Different techniques such as differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), Fourier transform infrared (FTIR), and synchrotron small-angle X-ray scattering (SAXS) were used to determine rigid-flexible segments’ phase behaviour. Retention of tensile properties determines the stability of the samples under different external factors. This work reveals that pure polycarbonate-based macrodiols induce the highest degree of phase miscibility, better tensile properties, hardness shore A, and retention of tensile properties under external agents.

Influence of Alkaline Environments on the Mechanical Properties of FRCM/CRM and their Materials

Fabric Reinforced Mortar (FRCM) used as Externally Bonded Reinforcements (EBR), provide a sustainable solution for retrofitting and repair of existing masonry structures. They are commonly made by fibrous meshes embedded in a cementitious/hydraulic lime matrix. This technique represents a valid alternative to the well-known FRP (Fiber Reinforced Polymer) composites, which show some limitations in heritage masonry applications. In this scenario, a new system known as CRM (Composite Reinforced Mortar) has been developed in the last years. In this system, a pre-cured FRP grid is utilized as internal reinforcement in a mortar layer. The system reproduces the traditional technique of reinforced plaster, where the steel grid is substituted by a non-metallic one. In masonry applications high compatibility with the substrate, sustainability and removability are commonly required in heritage construction. These goals are not easily achieved by using fibers immersed into a polymeric resin. Moreover, the inorganic matrix ensures the transpiration of substrates and consequently a higher durability of the whole strengthened system is expected. On the other hand, the recent use of these new materials in civil engineering needs appropriate design guidelines. The proposed paper focuses attention on the initial results of a large experimental study on the durability of FRCM/CRM systems and their single components (dry glass fibers, resin, pre-cured FRP grid and mortar). In particular, the influence of three alkaline environments solutions was studied. Exposure conditions were stressed by increasing the temperature of the three aqueous solutions. The mechanical retention of tensile properties was measured by performing direct tensile tests after different exposure times.

Calcination of UV shielding nanopowder and its effect on weather resistance property of polyurethane nanocomposite films

In this study, the synergistic effect of ZnO nanoparticles in combination with two different crystal phases of TiO2 nanoparticles on improving weather resistance property of polyurethane (PU) film has been studied. The UV shielding nanopowder containing TiO2 and ZnO nanoparticles was calcinated at varying conditions, and the process was optimized to obtain the desired crystal structure. After calcination, the change in crystal phase, crystal size, inter-planer distance in crystal and particle size was characterized using XRD, TEM and particle size analyzer, while chemical changes were analyzed by FTIR and EDX. The as-received as well as calcinated UV shielding nanopowders (1–5 wt%) were incorporated in PU matrix by melt mixing in a twin-screw extruder, and the extrudate nanocomposites were used to make films. The neat PU and nanocomposite films were exposed in accelerated artificial weathering for 300 h, while the films were analyzed at a 100-h interval. The physical and chemical changes of exposed film surface were analyzed by SEM, AFM and FTIR. The UV protection factor (UPF) of both types of PU nanocomposite films increased with increased loading of nanoparticles, although the UPF values were slightly lower for calcinated UV shielding nanopowder-based PU nanocomposite films. The calcinated UV shielding nanopowder showed good potential in improving weather resistance of PU nanocomposite films in term of—(1) lower change in surface morphology and surface chemistry and (2) better retention in tensile properties after exposure in accelerated artificial weathering. The synergistic effect of ZnO nanoparticle and rutile phase enriched TiO2 nanoparticles in calcinated UV shielding nanopowder enhanced the weather resistance of PU films significantly.

Cyclic Extrusion of Recycled High Density Polyethylene/Banana Fiber/Fly Ash Cenosphere Biocomposites: Thermal and Mechanical Retention Properties

AbstractDisposal of composite materials used vastly in structural applications raises the need to study the reprocessability of these systems for environmental benefits. In this paper, composites of recycled high density polyethylene (R) containing 30 wt.% banana fiber (BF)/7.5 wt.% fly ash cenospheres (FACS) were prepared with 3 wt.% maleic anhydride grafted high density polyethylene (MA-g-HDPE) as a coupling agent using twin screw extrusion followed by injection molding. The effects of thermal cycles (two times extrusion followed by injection molding) were studied on R and its composites. The samples were characterized by using tensile, flexural, izod impact tests, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetry (TGA) and dynamic mechanical analysis (DMA). The tensile and flexural properties were improved by addition of both BF/FACS into the R matrix. The percentage retention in tensile properties of R/BF/FACS(E2) biocomposites (i.e. two times extrusion followed by injection molding) is more than 80 %, while that for flexural properties is more than 90 %. This indicates that R/BF/FACS composites exhibit good retention ability in mechanical properties after subjecting to two times twin-screw extrusion followed by injection molding. DSC results revealed that repeated extrusion improved the crystallization temperature and crystallinity of the composites with a slight reduction in melting temperature. From the TGA results, it was observed that the thermal stability (e.g. Tonset) of R was reduced by the addition of BF/FACS. However, repeated extrusion showed an improvement in thermal stability of the composites.

ANALYSIS OF AUTOHESION AND PHYSICO-MECHANICAL PROPERTIES (MULTIFUNCTIONAL BEHAVIOR) OF THE COAGULUM FROM THE LATEX OF EUPHORBIA CADUCIFOLIA HAINES VIS-À-VIS COMPARISON AGAINST SYNTHETIC RESINS IN NATURAL RUBBER COMPOUNDS

ABSTRACT Soft and tacky mass recognized as whole coagulum (Cog) and its toluene soluble fraction (TE) obtained through coagulation of latex of Euphorbia caducifolia Haines has been investigated in this article as green tackifier cum multifunctional agent in natural rubber (NR) based gum compounds. It was observed that inclusion of TE and Cog in the formulations increased tack strength over the control compound (without TE and Cog). At the same loading, autohesion for natural and commercial coumarone indene resin was found comparable. However, phenol formaldehyde (non–heat reactive octyl phenol formaldehyde) resin demonstrated highest tack strength among all the NR compositions studied. Presence of various functional groups such as esters/carboxylic acid, carbon–carbon unsaturation, and so on, in natural resin activated the system and reduced the activation energy barrier for curing. The optimized composition with 5 phr TE showed nearly 5% reductions in activation energy over the control compound. However, no such cure acceleration was displayed by Cog. Unaged tensile properties of the compounds with natural resin at similar proportions to commercial resins were found comparable. Retention of tensile properties after aging for the vulcanizates with TE was better than those with the commercial resins. For Cog, however, the retention of elongation at break and tensile strength were slightly higher compared with tensile modulus.

Hydrogenated nanosized polyisoprene as a thermal and ozone stabilizer for natural rubber blends

Abstract Hydrogenated polyisoprene (HPIP) nanoparticles, synthesized via organic solvent-free hydrogenation using RhCl3/TPPMS as a catalyst, are novel nanofillers for natural rubber (NR) blends. Hydrogenation of a polyisoprene (PIP) emulsion was carried out in a Parr reactor. Rhodium trichloride (RhCl3.3H2O) and monosulfonated triphenylphosphine (TPPMS) were used as the catalyst precursor. The HPIP was characterized by proton nuclear magnetic resonance spectroscopy. The PIP hydrogenation in the absence of organic solvent is a first-order reaction with respect to carbon–carbon double bond concentration, and the rate constant was dependent on catalyst concentration. The highest hydrogenation degree of 93% was achieved at a catalyst concentration of 250 μM with a reaction time of 12 h. The NR/HPIP blends (blend ratio = 80:20) after thermal aging show high % retention of their tensile strength and modulus, maintaining 94.5% and 93.7%, respectively. Moreover, a combination of HPIP in NR improved the ozone resistance at the surface of the rubber blends. Therefore, the NR/HPIP composite exhibited a good retention of tensile properties after thermal aging and good resistance toward ozone.

A comparative study of aging characteristics and thermal stability of oil palm ash, silica, and carbon black filled natural rubber vulcanizates

ABSTRACTFiller‐filled natural rubber (NR) vulcanizates were prepared by conventional laboratory‐sized two roll mills and cured using sulfuric system. The effect of thermal aging on physical properties and thermogravimetric analysis (TGA) of oil palm ash (OPA) and commercial fillers (i.e., silica vulkasil C and carbon black N330)‐filled NR vulcanizates at respective optimum loading and equal loading were studied. Before aging, the OPA‐filled vulcanizates showed comparable optimum strength as carbon black‐filled vulcanizates. The hardening of aged filler‐filled NR vulcanizates happened after aging, thereby tensile strength and elongation at break reduced while the modulus increased. Fifty phr carbon black‐filled vulcanizates showed better retention in tensile properties as compared to silica (10 phr) and OPA (1 phr). This was attributed to the addition of different filler loading and this finding was further explained when equal loading of filler‐filled vulcanizates was studied. Fourier transform infra‐red analysis showed chemical structure had changed and tensile fractured surface exhibited smooth appearance due to the deterioration in tensile properties after aging. TGA also denoted the thermal stability was depending on the amount of filler loading. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4474–4481, 2013

Effect of chemical degradation on the mechanical properties of ethylene–propylene–diene (5-ethylidene-2-norbornene) terpolymer-BaSO4 nano composites

Time dependent degradation of the gum vulcanizates of ethylene propylene diene (EPDM) and EPDM-barium sulphate nano composites in sulphuric acid were studied. Impact of degradation on the mechanical properties of these composites was also evaluated. Gum compounds and nanocomposites cured with efficient vulcanisation system were subjected to an aggressive acidic medium containing 60% aqueous solution of sulphuric acid (H2SO4). The changes in functional groups were monitored using Fourier transform infrared spectroscopy (FTIR). The results reveal the formation of several oxygenated species on the EPDM rubber molecule due to acid attack; which is enhanced in the absence of barium sulphate nanofillers. Crosslink densities of acid aged samples were measured by the swelling method. An initial decrease in crosslink density as observed in EPDM gum vulcanizates is an indicative of hydrolytic attack at the crosslink sites, whereas the effect is less pronounced in nano composites. The effects of acid attack on mechanical properties were traced out by evaluating the percentage retention in tensile, elongation at break, compression set and abrasion resistance. For aged EPDM gum vulcanizates the retention in tensile showed a positive sign for a given increase in crosslink density, but on further increase of crosslink density due to combination of species formed during decrosslinking, tensile strength decreases. In the case of nano composites the retention in tensile properties was well around 100%. Scanning electron microscopy was used to monitor the changes in surface topography due to attack of acid and it well supports the degradation phenomenon and stabilisation of mechanical properties in the presence of barium sulphate nanoparticles.

Thermal-oxidative degradation of polyamide 6,6 containing metal salts

The thermal-oxidative stability of oven aged polyamide 6,6 (PA6,6) doped with Co, Cu, Ni and Zn chlorides combined with KI was examined. Aging caused a depression in melting temperature and an increase in enthalpy of fusion of PA6,6 films due to the formation of a strongly degraded crystalline fraction with a lower molecular weight. A build-up of carbonyl absorption in the range 1700–1780 cm −1 due to primary and secondary photo-oxidation products was detected. The kinetics of carbonyl accumulation was affected by the morphology of the samples, and it was observed that at a later stage of aging the crystalline phase was also involved in the oxidation process. The above mentioned changes were greatest in the case of neat, Co and Ni doped polymer, suggesting that these metal salts acted as pro-oxidants. On the other hand, the use of Cu and Zn chlorides brought about a substantial increase in long-term polymer stabilization. Tensile tests revealed a large reduction in ductility as a result of aging for neat, Co and Ni doped polymer, whereas long-term retention of tensile properties was found for the polymer stabilized with Cu and Zn. The presence of the metal salts combined with KI led to increased stabilization for chlorides of Ni, and Co, owing to the participation of KI in non-radical decomposition of peroxides. No effect due to KI was observed for ZnCl 2.

Natural Weathering Test of Styrene Butadiene Rubber and Recycled Acrylonitrile Butadiene Rubber (SBR/NBRr) Blends

The effect of recycled acrylonitrile butadiene rubber (NBRr) content of SBR/NBRr blends on natural weathering was studied. Three different size of NBRr (S1; 117–334 µm, S2; 0.85–15.0 mm and S3; direct sheeted form) were used and the blends were exposed to natural weathering for 3 and 6 months. The results indicated that the SBR/NBRr blends with smallest size of NBRr (S1) show a better retention of tensile properties, which are able to withstand better weathering than coarser size (S2 and S3) of SBR/NBRr blends. The presence of hydroxyl, carbonyl and nitro group after exposure to natural weathering was detected in FTIR analysis, which related to the UV oxidation process of rubber blends. The scanning electron microscopy proved that the SBR/NBRr blends with smallest size of NBRr (S1) with higher content of NBRr, shows a better resistant to natural weathering.

Structure and Mechanical Properties Relationship of Wood-Filled Recycled Multilayer Films

The effect of compatibilizers such as polyamide-6 (PA) having oxazoline functionality or styrene–ethylene/butylene–styrene block co-polymer (SEBS) having anhydride functionality on structure and mechanical properties of recycled multilayer film waste (MFW) filled with wood fibre were investigated. The influence of aging at 105°C for 7 days on the mechanical properties of the composites also was tested. The results show that the investigated properties of the composites depend extensively on the compatibilizer used. The wood fibre causes slight decrease in tensile strength and drastic effect in elongation, on the one hand, and improves modulus on the other. The strength and modulus were not substantially affected by aging at 105°C for 7 days. But the situation was different in the case of elongation. At higher filler concentration (>20 wt%), the composites showed a better maintaining of elongation compared to low (10 wt%) filler concentration. However, the composites showed good retention of tensile properties.

Investigation on Ageing Characteristics of Short Nylon-6 Fibre Reinforced NBR Composites

The ageing characteristics of nylon 6 fibre reinforced NBR composites have been analysed by exposing them to degrading agents such as heat and gamma (γ) radiation. The effects of fibre loading, curing systems and bonding agents on the retention of tensile properties of the composite samples which were exposed to these degrading agents have been studied. The addition of fibres improves the ageing resistance of NBR. The DCP cured composites exhibit a reduction in their ability to retain the elastic modulus as the thermal ageing period increases from 7 to 14 days, whereas sulfur cured composites show a reverse trend. The efficiency for the retention of modulus of sulfur cured samples increases as the dosage of γ-radiation increases from 5 to 10 Mrad whereas a higher dose of 15 Mrad lowers it. However, the DCP cured samples show a continuous reduction in their ability to retain modulus. The composite system containing hexa-resorcinol as the bonding agent has better resistance to heat and γ-radiation than the unbonded one.