Thermoplastic Research Articles

In situ X-ray diffraction and thermal simulation of material extrusion additive manufacturing of polymer

Material extrusion additive manufacturing (AM) has gradually become a dominant technology for the fabrication of complex-designed thermoplastic polymers that require a higher level of control over the morphological and mechanical properties. The polymer internal crystal structure formed during the AM process can present significant impacts on the mechanical properties of the individual filaments, as well as the whole structure. Currently, limited details are known about the crystal structure evolution during the material extrusion AM processes of polymers. A novel in situ synchrotron X-ray diffraction (XRD) experimental configuration was developed enabling us to capture the material evolution data throughout the extrusion AM process. The in situ time-resolved data was analysed to reveal nucleation and crystallization sequences during the continuous deposition, with the aid of both complimentary numerical simulations and post-process (ex situ) characterisations. The thermal simulations supported the prediction of the filament temperature profile over time and location during the AM process, while ex situ characterisations validated the correlation between polymer crystallinity (resulting from printing parameters) and corresponding mechanical properties. The results obtained from varied process parameters suggest that the processing temperature has a dominant influence on the crystal microstructure evolution compared to the deposition velocity. A lower processing temperature just above the melting temperature permitted favourable crystallization conditions. The overall analysis demonstrated prospects for enhancing polymer AM, to engineering mechanically hierarchical structures through correlative investigations.

Comparison of the in situ compressive behavior of carbon fibers woven ply laminates exposed to one‐sided heat flux: Thermoplastic versus thermosetting composites

AbstractThis study investigates the influence of a combined thermal heat flux (imposed by a cone calorimeter) and a compressive loading on the deformation and damage mechanisms within quasi‐isotropic carbon fibers reinforced thermoplastic (polyetherether ketone [PEEK] and polyphenylene sulfide [PPS]) and thermosetting (epoxy) laminates. First, thermogravimetric Analyses conducted under nitrogen provide valuable information on the thermal decomposition of these materials depending on the matrix nature (580–510°C and 350°C, respectively) which is a key factor to explain the mechanical behavior under fire conditions. Second, under the same testing conditions (creep loading under a 50 kW/m2 heat flux), the time to failure is about 17 times as high (C/PEEK), twice as high (C/PPS) with respect to C/epoxy laminates. At the ply scale, the exposure of thermoplastic matrices (PEEK and PPS) to a 50 kW/m2 heat flux causes softening and thermal decomposition, facilitating the micro‐buckling of fiber bundles in matrix‐rich areas. At the laminates scale, this mechanism ultimately leads to the formation and propagation of plastic kink bands in the transverse direction. In epoxy‐based laminates, the onset of matrix pyrolysis occurs at lower temperatures (350°C) during thermal aggression, and thermal decomposition has started in all the plies of the laminates. Combined with the low ductility of the epoxy matrix, the compressive response is elastic‐brittle and results from the buckling of 0° plies outside the thermally‐damaged area.Highlights Study on the compression of polymer composites exposed to a 50 kW/m2 heat flux. The influence of the matrix nature (thermoplastic vs thermoset) is discussed. Time to failure is about 17 times higher in C/PEEK compared to C/Epoxy. Plastic kink bands propagate in thermoplastic composites at T > Tg. C/Epoxy laminates undergo buckling outside the thermally damaged area.

Thermal kinetic, mechanical and wear properties of glass fiber reinforced polyamide 6 thermoplastic composites

AbstractPolyamide 6 (PA6) thermoplastic‐based composites are often used in automobile, aerospace, marine, and biomedical applications. Here, PA6 and its composites with varied chopped glass fiber (GF) concentrations of 5, 10, and 20 mass% were fabricated by injection molding. The specimens were characterized by structural, thermal kinetic, mechanical, as well as tribological analyses. Tribological performance was evaluated in dry pin‐on‐disc test apparatus with three different levels of time, speed, and load factors. The PA6/GF composites showed high decomposition activation energy compared to pure PA6. Thermal activation, Ea increased to 46.16% with increasing of GF content up to 10 mass% in the composites compared to PA6. PA6/5GF exhibited best mechanical properties (e.g., strength = 44.46 MPa and Hardness = 45.2). Addition of GF in PA6 significantly improved tribological properties, coefficient of friction (COF) and specific wear rate (WR) besides thermal stability and mechanical properties of the composites. Especially, COF and WR of PA6/5GF composite decreased by 17%–65% and 68%–92%, respectively, compared to PA6. ANOVA statistical results determined the significant contribution of the tribological factors to the performance metrics of the composites for COF and WR. Therefore, the PA6/5GF composite would highly be useful for tie‐rod gears and bearings as a crucial structural component in automotive bodywork.

Investigation of MXene@APP/FDS/AgNPs@EG system for preparing multifunctional thermoplastic polyurethane composites with flame retardancy and electromagnetic shielding performance

In order to comply with the requirement of flame retardancy and electromagnetic interference (EMI) shielding for encapsulant applied to electronic devices, multifunctional thermoplastic polyurethane (TPU) composites are prepared with the construction of an intumescent flame retardant (IFR) system comprising internal conductive network. In this work, ammonium polyphosphate wrapped with MXene (MXene@APP) is attained by microencapsulation, and expandible graphite decorated with Ag nanoparticles (AgNPs@EG) is prepared by the reducibility of silk sericin. The IFR system with conductivity is established by the introduction of MXene@APP, AgNPs@EG and furfural-derived Schiff base (FDS). The as-prepared TPU/MXene@APP/FDS/AgNPs@EG composites are able to attain significant elevation in flame retardancy, exhibiting V-0 rating and a LOI value of 33.1 %. Furthermore, TPU composites are integrated with warp-knitted metal mesh (WMM) to fabricate TPU@WMM coated fabric, displaying strengthened electromagnetic interference (EMI) shielding effectiveness (SE) of 37.53 dB within X band. This work provides a potential method for application in encapsulant with flame retardancy and electromagnetic protection.

Study on short fiber reinforcement mechanism for mechanical performance improvement of 3D‐printed short‐continuous carbon fiber reinforced thermoplastic composites

Study on short fiber reinforcement mechanism for mechanical performance improvement of <scp>3D</scp>‐printed short‐continuous carbon fiber reinforced thermoplastic composites

Fabrication and characterization of natural fiber reinforced cowpea resin-based green composites: an approach towards agro-waste valorization.

A paradigm shift towards using bio-resins or bio-derived resins among materials scientists has led to wide exploration of the sector. Polymers such as soy protein isolate, poly(hydroxy alkanoate), poly(lactic acid), and thermoplastic starch are all synthetically modified bio-based resins and are costly. The cowpea-derived resin with the least chemical modification was used in this study as a matrix for the formation of composites with natural fibers at a lesser cost. Fabrication of composites of vetiver and jute with varying weight percentages of fiber (50, 60, and 70%) in the innovative cowpea resin resulted in favorable mechanical properties and degradability. The tensile strength was the highest for the jute-cowpea composite (JCP2) at around 37.49 MPa, which also has a flexural strength of 40.3 MPa. Dynamic mechanical analysis of composites reflects the moderate storage moduli of 1802 MPa for JCP2 and 1351 MPa for vetiver-cowpea (VRCP2) composites. Impact strength studies and thermal stability also show optimistic results. The contact angle, water absorption behavior, and swelling in thickness show the moderate hydrophobicity of the composites. This is also a reason for the improved degradability of the composites in soil-burial and microbial environments. Characterizations such as FE-SEM and FTIR spectroscopy, conducted after the degradation of the samples, showcased the level of deterioration. All these results suggest using the innovative cowpea resin as a good alternative to various other synthetic thermoplastic resins used in the fiber reinforced composite manufacturing field.

Additive manufacturing of polymeric pressure die for rotary draw bending process

3D printing or additive manufacturing (AM) possesses enormous potential to benefit the manufacturing industry. Presently, rotary draw bending (RDB) is one of the most commonly used cold-forming industrial process for bending metal tubes. Pressure die is a fundamental forming tool in RDB processes, and it is conventionally made by various grades of comparatively expensive alloy steels. This research presents a novel design of a pressure die which can be 3D printed by using inexpensive polymeric filaments. In this research paper, the 3D-printed pressure die is named as “FFF-pressure die.” The material used to fabricate the FFF-pressure die is a thermoplastic polymer known as “ecoPLA.” The mechanical properties of ecoPLA are studied in relation to the process conditions of a RDB process. Firstly, an initial feasibility of using the FFF-pressure die in a RDB process is obtained by conducting a quick static stress analysis with actual process conditions. After initial feasibility, a complete RDB process is developed and simulated with actual process conditions and material properties. The FFF-pressure die is then practically fabricated by FFF 3D printer and experimentally tested on an industrial RDB machine. The results of practical experiments are compared with the simulation results. In order to make a comparison of the FFF-pressure die with the conventional metal pressure die, the simulation and practical process is also conducted with the conventional metal pressure die. A performance and cost comparison is made between the polymeric FFF-pressure die and the conventional metal pressure die. Von Mises stresses, contact forces, failure risk, and elastic deformations are analyzed. The advantages and limitations of using the FFF-pressure die in a RDB process are discussed in the end. This research intends to widen the avenue of using cost-effective and lightweight forming tools in metal forming industries.

PEBAX® 5533D Formulation for Enhancement of Mechanical and Thermal Properties of Material Used in Medical Device Manufacturing

The medical device industry is constantly innovating in the search for materials that demonstrate superior performance, better intrinsic characteristics, profitability, and a positive impact on potential patients. The thermoplastic polymer resin Pebax® 5533D is one of the most widely used commercial materials for manufacturing medical device parts due to its easy processability. However, its mechanical and thermal properties require improvements to mitigate identified manufacturing defects, such as a decrease in material flexibility, high susceptibility to moisture, and thermal degradation during processing. Therefore, this study integrated different materials, such as plasticizers and filler additives, to produce a polymer compound prototype formula as a solution technique to enhance the current material’s performance. Modifying mechanical and rheological properties allows to evaluate the impacts on the polymeric material’s flexibility and thermal behavior. This was achieved by processing mixed additives using injector-molding equipment to obtain equal-molded samples of every formula. In addition, material characterization was performed to determine the variations in the samples’ crystallization, flexural strength, and moisture content. Calcium stearate was determined to be the most significant component serving as a mechanical resistance modifier and thermal stabilizer alongside calcium chloride as a moisture content reducer combined with Pebax® 5533D.

Effects of Thermoforming Parameters on Woven Carbon Fiber Thermoplastic Composites.

The quality of woven carbon fiber fabric/polycarbonate thermoplastic composites after thermoforming and demolding was investigated using finite element simulation and the Taguchi orthogonal array. The simulation utilized a discrete approach with a micro-mechanical model to describe the deformation of woven carbon fabric, combined with a resin model. This simulation was validated with bias extension tests at five temperatures. The thermoforming process parameters considered were blank temperature, mold temperature, and blank holding pressure, with three levels for each factor. Optimal values for the fiber-enclosed angle, spring-back angle, mold shape fitness, and the strain of the U-shaped workpiece were desired. The results indicated that the comparison of the stress-displacement curve of bias extension tests verified the application of the discrete finite element method. Results from the Taguchi array indicated that blank holding pressure was the dominant parameter, with the optimal value being 1.18 kPa. Blank temperature was the second most significant factor, effective in the range of 160 °C to 230 °C, while mold temperature had a minor effect. Furthermore, the four quality values are dependent and have a similar trend. The best combination was identified as a blank holding press of 1.18 kPa, a blank temperature of 230 °C, and a mold temperature of 190 °C.

Additive manufacturing and mechanical performance of short fiber reinforced PEEK (polyether ether ketone) thermoplastic composites in a vacuum environment

Short fiber reinforced thermoplastic composites (SFRTC) have gained popularity in the material extrusion (MEX) method, which is an additive manufacturing (AM) technology, allowing for the simpler and more cost-effective production of polymer composites. However, parts produced using MEX 3D printing technology often exhibit poor mechanical properties and surface quality compared to products manufactured using injection molding, which is one of the main disadvantages of this method. Various methods are used to overcome these challenges, such as production in a vacuum environment, heat-based processes, ultrasonic vibrations, and others. The objective of this study was to achieve parts with lower porosity and improved mechanical properties when printed in a vacuum environment compared to an atmospheric environment. Additionally, an investigation into the optimization of printing parameters was conducted to determine the parameters that yield the highest mechanical properties. For this purpose, SFRTC parts were printed at different vacuum levels (0.5, 10, 100 mbar), and they were subjected to flexural tests to determine their mechanical properties. The results showed that the flexural stress and elastic modulus of the samples produced in a 0.5 mbar vacuum environment increased by 79.75% and 39.41%, respectively, compared to samples produced in an atmospheric environment. Furthermore, the cross-sectional images of the samples were examined using an optical microscope, revealing the lowest porosity in the samples printed in 0.5 mbar vacuum environment.

FDM printing of microneedles based on biocompatible and biodegradable thermoplastic polymers

AbstractMicroneedles are an emerging class of transdermal drug delivery systems for biomedical applications. These devices allow minimally invasive and painless drug delivery, making them an attractive alternative to hypodermic injections. This paper focuses on the study of polymer‐based solid microneedles fabrication process using the fused deposition modeling (FDM) method. Biodegradable and biocompatible polymers are selected as printing materials. For this study, the thermoplastic polylactic acid (PLA), currently used for FDM microneedle preparation was selected. To overcome the potential brittleness of PLA during transdermal application, two other materials are also studied: polycaprolactone (PCL) and a PLA/PCL blend. The effect of 3D printing parameters on the dimensional accuracy of the microneedles is studied to determine the optimum printing conditions for each filament. In addition, the dimensions and/or geometry of the microneedles are modified to print its with minimal dimensions. Then, a post‐fabrication chemical etching treatment is used to improve both, size and shape of the printed solid microneedles.

Repercussion of fiber content on the mechanical, thermal, and thermomechanical properties of natural fibers reinforced thermoplastic composites for automotive application

Natural fibers are becoming very popular as a reinforcement in composite materials owing to their benefits, such as low-price, lightweight, availability, and environmental friendliness. In this study, abaca fiber-reinforced polypropylene (PP) and high-density polyethylene (HDPE) composites were created with the help of the injection molding method. Prior to composite fabrication, abaca fibers were chemically treated with a 5 wt% caustic soda (NaOH) solution to improve the bonding between the abaca fibers and the matrix and to enhance their properties. Scanning electron microscopy (SEM) was utilized to assess the fiber surface microstructures before as well as after the chemical treatment, along with the fractured surfaces of tensile specimens. The mechanical properties, such as tensile, bending, and impact strength, of abaca/PP and abaca/HDPE composites were evaluated and compared. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) methods were utilized to investigate the thermal behavior of composites. Also, the dynamic mechanical analysis (DMA) method was utilized to explore the thermomechanical properties of the fabricated composites. The outcomes of the experimental findings showed that abaca/PP composite with 10 and 20 wt% fibers is the best choice of material to be used in the automobile industry.

Restoration of Strength in Polyamide Woven Glass Fiber Organosheets by Hot Pressing: Case Study of Impact and Compression after Impact.

Thermoplastic composite organosheets (OSs) are increasingly recognized as a viable solution for automotive and aerospace structures, offering a range of benefits including cost-effectiveness through high-rate production, lightweight design, impact resistance, formability, and recyclability. This study examines the impact response, post-impact strength evaluation, and hot-pressing repair effectiveness of woven glass fiber nylon composite OSs across varying impact energy levels. Experimental investigations involved subjecting composite specimens to impact at varying energy levels using a drop-tower test rig, followed by compression-after-impact (CAI) tests. The results underscore the exceptional damage tolerance and improved residual compressive strength of the OSs compared to traditional thermoset composites. This enhancement was primarily attributed to the matrix's ductility, which mitigated transverse crack propagation and significantly increased the amount of absorbed energy. To mitigate impact-induced damage, a localized hot-pressing repair approach was developed. This allowed to restore the post-impact strength of the OSs to pristine levels for impact energies below 40 J and by 83.6% for higher impact energies, when OS perforation was observed. The measured levels of post-repair strength demonstrate a successful restoration of OS strength over a wide range of impact energies, and despite limitations in achieving complete strength recovery above 40 J, hot-pressing repair emerges as a promising strategy for ensuring the longevity of thermoplastic composites through repairability.

Effect of Adding Different Concentrations of Silver Nanoparticles on Flexural Strength and Microhardness of Different Denture Base Materials.

This study aimed to evaluate the effect of adding different concentrations of silver nanoparticles (AgNPs) on the flexural strength and microhardness of various denture base materials. For this study, a total of 60 specimens were used and divided into equal groups. The first group consisted of heat-cured acrylic resin (Vertex-Germany), while the second group consisted of thermoplastic resin (Breflex 2nd edition, Germany). The samples were created using a split brass mold with dimensions of 65 × 10 × 2.5 mm, in accordance with the specifications of the American Dental Association (specifically No. 12 for flexural and microhardness). Following this, the samples were divided into three groups (A, B, and C) based on different concentrations of AgNPs (0, 2, and 5%). The flexural and microhardness of the samples were assessed using a universal testing machine and the Vickers hardness test, respectively. The data were gathered, organized, and analyzed using statistical methods. The flexural strength findings showed a significant difference between the two groups. Also, there was a considerable decrease in the average value of the acrylic group as the concentrations of AgNPs rose, while the flexural strength of the thermoplastic group notably improved. Regarding microhardness, the results showed a significant difference between the two groups. It showed that the mean value of both groups increased with increasing concentrations of AgNPs. Within the limitations of laboratory testing conditions of this study, it was discovered that AgNPs negatively impact the flexural strength of acrylic resins. Furthermore, an increase in the concentration of AgNPs was found to be directly related to the flexural strength of thermoplastic resin and the microhardness of both groups. The concentration of AgNPs has a significant impact on certain mechanical properties of denture base materials, but it is important to consider their potential toxicity. How to cite this article: El-Hussein IG. Effect of Adding Different Concentrations of Silver Nanoparticles on Flexural Strength and Microhardness of Different Denture Base Materials. J Contemp Dent Pract 2024;25(5):417-423.

Material extrusion fabrication of continuous metal wire-reinforced polymer–matrix composites

3D printing via material extrusion is capable of using polymeric materials for a large range of applications. They are generally used, however, for prototyping as opposed to creating functional parts due to their lower mechanical properties in comparison to other materials, such as metals or epoxies, and processing methods, such as compression molding or injection molding. Carbon fiber, glass fiber, and kevlar have been used as reinforcement materials with very positive results in terms of creating functional parts. However, little focus has been placed on metallic wire reinforcement. In this investigation, a novel strategy to manufacture continuous metallic wire-reinforced polymer–matrix composites with increased mechanical properties by material extrusion is presented. A customized multimaterial 3D printer was built and used to fabricate coupons of unidirectionally reinforced Al wire/PLA matrix composites with either 15% or 25% wire volume fraction. The microstructure of the composites was analyzed to understand the formation of porosity during processing. These results also showed the potential of the manufacturing technique to precisely control the wire location and orientation. Incorporation of a volume fraction 25% of Al wires led to a 600% increase in elastic modulus and a 63% increase in tensile strength compared to pure PLA. These results indicate an efficient load transfer between the polymer matrix and the incorporated wires, despite exhibiting a relatively low interface strength. Overall, the novel strategy opens the possibility to manufacture high volume fraction composite laminates of thermoplastic polymers reinforced with metallic wires by material extrusion.

Integration of recycled denim waste cotton fibre and jute fibre in thermoplastic bio composite applications

High-stiffness and high-strength natural fibres are commonly utilized in thermoplastic matrices to manufacture biobased thermoplastic composites. Low-end applications such as construction and furniture industries do not require a high load-bearing capacity, thus favoring cost-effective, moderately strong, sustainable natural materials and quickly manufacture thermoplastic composites. Recycled biobased cotton fibres collected from the denim industry can effectively penetrate this composite industry due to their cost-effectiveness and desirable physical and mechanical properties. However, retaining structural integrity and enhancing the reinforcing efficiency of recycled yarns in composites pose challenges. Addressing these issues, we propose a new method of extracting recycled cotton from denim waste fabric and transforming it into dry preform with minimal damage to the structural integrity of cotton fibres. Jute fibres have been introduced alongside recycled denim fibers within a polypropylene matrix to optimize the hybrid reinforcing efficacy of the composites. The effect of denim fibre length on composite quasi-static tensile and flexural test results showed that a yarn length of 20 mm yielded the highest tensile strength (⁓27.83 MPa), tensile modulus (⁓ 1.76 GPa), flexural strength (⁓62.35 MPa), and flexural modulus (⁓1.17 GPa). Composites comprising recycled denim yarn and jute fibre improved the tensile modulus to approximately ⁓2.1 GPa and the impact strength to approximately ⁓66.1 kJ/m2, following the hybrid rule of mixture, while jute fiber serves to increase the stiffness and toughness of the composites. This work demonstrates that recycled denim cotton fibre and strong jute fibre can be successfully integrated into thermoplastic composites to achieve tailored mechanical properties.

In-situ crystallization process monitoring of thermoplastic composites by dielectric sensing during laser-assisted automated fiber placement

The crystallization process during the laser-assisted automated fiber placement (LAFP) is important for the mechanical performance and process-induced deformation of fiber reinforced thermoplastic composites. However, there is lack of method for in-situ crystallization process monitoring of thermoplastic composites during the LAFP process with rapid cooling and multiple heating. Here we present a novel dielectric method for in-situ measurement of crystallization development of glass fiber reinforced polypropylene (PP) during the LAFP process using interdigital electrodes for the first time. The accuracy of the dielectric method was verified by standard XRD and DSC methods at different cooling rates. Furthermore, the effect of laser power on crystallinity was analyzed by the proposed method. The feasibility of this method for monitoring crystallinity development during continuous LAFP process was performed. We anticipate that the dielectric method offers considerable potential for quality monitoring for the LAFP process and other additive manufacturing processes for thermoplastic composites.

APPLICATION OF MODULAR CSIPS TO TRADITIONAL KOREAN HANOK TIMBER STRUCTURES FOR THERMAL AND ENERGY PERFORMANCE

ABSTRACT This study examines the thermal and energy performance capabilities of composite structural insulation panels (CSIPs) for traditional Korean architecture, specifically Hanok. Hanok buildings, renowned for their cultural and architectural significance, often face thermal efficiency and energy consumption challenges. This research aims to explore the environmental potential of CSIPs to improve the thermal performance of Hanok structures while maintaining the traditional aesthetics of these buildings. Simulations were conducted to analyze the thermal behavior, heat flow, and energy use intensity (EUI) by wall cases of Hanok buildings, applying continuous-fiber-reinforced thermoplastic composites as a type of CSIP. The findings demonstrated that applying continuous-fiber-reinforced thermoplastic composites (CFRTCs) to the target Hanok building significantly enhanced the thermal performance, including the thermal bridge and envelope airtightness, as these composites can reduce the thermal conductivity and minimize heat loss, thus improving the insulation capabilities. Furthermore, adopting modular CSIPs in Hanok architecture offers environmental benefits and aligns with sustainability and constructability goals. By reducing reliance on mechanical heating and cooling systems, CSIP-enhanced Hanok buildings can contribute to lower energy consumption and greenhouse gas emissions. This simulation study highlights the significant potential of CSIPs with fiber-glass-reinforced thermoset (FRT) polymer skins to enhance the thermal and energy performance of traditional Korean Hanok buildings. CSIPs as applied to the target Hanok can potentially reduce heating energy consumption by approximately 21% to 29%, leading to overall energy savings of about 4% to 5% in site EUI and CO2 emissions levels per unit area.

Physical and Mechanical Properties and Durability Characteristics of New Pultruded GFRP Bars with Thermoplastic Resin

Physical and Mechanical Properties and Durability Characteristics of New Pultruded GFRP Bars with Thermoplastic Resin

Effects of Egg and Snail Shells on Biodegradation and Tensile Properties of Waste Plastics Fabricated Thermoplastics Elastomer Composites

The essence of this study is to proffer solution on the degradation of the environment caused by non-degradable plastics waste. A novel approach on plastic waste management was adopted by fabricating a thermoplastic natural rubber (TPNR) composite using waste Polyethyleneterephthalate {PET}plastics and eggshell as biofillers to initiate degradation by microorganism.Waste Polyethylene Terephthalates (PET) was grinded andmelted blended with Natural Rubber with 40pphr of Eggshell to fabricate a Natural Rubber Thermoplastic elastomer (TPNR) composite. The resultant thermoplastic elastomer composite was prepared for soil burial for a period of 90 days to obtain percentage weight loss as an indication of biodegradation. The NR/PET composite was evaluated for tensile properties. The results obtained were of the new that the tensile strength, elongation at break and modulus decreases with increase in soil burial duration time. The eggshell as a biopolymer has been shown to initiate biodegradation. There was a reduction in tensile strength at a blend ratio of 50/50 NR/PET blend, an indication that degradation has occurred, hence tensile properties are useful tools for the evaluationof biodegradation of polymeric materials