Dynamic Mechanical Measurements Research Articles

Design of epoxy-silica hybrids based on cycloaliphatic diol of natural origin for conservation of lithic materials

This work is focused on the development of sustainable stone conservation materials, based on BPA-free epoxy-silica hybrid resins, with consolidating and hydrophobic properties, for long-term treatments. For this purpose, a cycloaliphatic diol, with minor health and environmental associated issues with respect to classic phenolic derivatives, was selected to synthesize a BPA-free bio-based epoxy resins precursor, 2,2,4,4-tetramethyl-1,3-cyclobutanediol diglycidylether (CBDO-DGE). Fourier transform infrared (FT-IR) and Raman spectroscopies were employed to assess the synthesis and clean-up procedures. In addition, both 1H-NMR and 13C-NMR in solution were used to ascertain the structure and purity of the bio-based epoxy. The development of the epoxy thermosets by 1,8- diaminooctane (DAO), triethylenetetramine (TETA) and 5-amino-1,3,3-trimethylcyclohexanemethylamine (IPDA) curing agents was followed by attenuated total reflection infrared (ATR FT-IR) and Raman spectroscopies, whereas their suitability as organic counterpart of the hybrids was established by differential scanning calorimetry (DSC) and thermogravimetric (TGA) measurements. In addition, epoxy-silica hybrids were obtained by exploiting sol-gel technology, carrying out the epoxy hardening reactions also in the presence of (3-glycidyloxypropyl)trimethoxysilane (GPTMS) and octyltriethoxysilane (OcTES), as silica-forming additives. To investigate the properties of the resulting hybrid materials imparted by the selection of the different reactants, various blends were studied by a combination of scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM-EDS), ATR FT-IR and Raman analysis. Furthermore, the assessment of the hybrids tunability as materials for stone conservation was ascertained in terms of thermostability and hydrophobicity by TG-DTA, DSC, dynamic mechanical analysis (DMA) and contact angle measurements.

Investigation of filler network percolation in carbon black (CB) filled hydrogenated butadiene-acrylonitrile rubber (HNBR)

The filler network is one of the most important concepts in filled rubber nanocomposites. It ensures the rubber matrix some properties, such as electrical conductivity, heat conductivity, reinforcement property, and so on. The more or the less the filler content, the worse the combination properties. Therefore, the filler network percolation threshold is very significant to be controlled. In this work, the filler network percolation in CB filled HNBR was investigated, combining dielectric with dynamic and quasi-static mechanical measurement. The results showed there are two sudden increases in the platform value of the conductivity by 1–3 orders of magnitude by means of dielectric measurement. They are defined as the (α) process and the (α′) process, respectively. The (α) process that the CB content is between 25 vol.% and 26.5 vol.% is classified to the electric percolation threshold, according to the percolation theory prediction. Meanwhile, the (α′) process that the CB content is between 21.7 vol.% and 23.4 vol.% corresponds to the mechanical percolation threshold, according to the result of mechanical measurement.

Correlating ultra‐toughening of bio‐based polyamide 410 with melt rheological and solid state relaxation dynamics by gelation rheology approach

AbstractThe sol–gel or viscous‐elastic transitions of the bio‐based polyamide 410/POE‐g‐MA (polyethylene‐co‐octene copolymer grafted with maleic anhydride) blends have been systematically discussed in the framework of melt rheology as assessed on a parallel plate rheometer set‐up in small amplitude oscillatory shear mode and solid state dynamic mechanical relaxation measurements. The viscous response dominated enhancement in elastic moduli of the blends that was characterized by the phase transitions across the composition range of 10–15 wt% of POE‐g‐MA. A direct correlation between the gel point (estimated from the cross‐over of frequency‐independent loss tangent curves) and the ultra‐toughness (maximized to an extent of ~15‐fold increase in notched Izod impact strength) could be established vis‐a‐vis its corroboration from the morphology of the impact‐failed surfaces. The extent of maleic anhydride (−MA) content induced phase interaction with polyamide 410 via the formation of a polyamide‐co‐(polyoctene‐co‐ethylene) type copolymer linkage in solid‐state and its subsequent impact on solid‐state damping was analyzed. The study establishes qualitative correlation between ultra‐toughening of polyamide 410 to that parameters based on relaxation dynamics measurements using melt rheology and solid‐state dynamic responses conforming to the principles of gelation rheology.

Gel growth of aqueous konjac glucomannan solution containing sodium trimetaphosphate dialyzed with dilute sodium hydroxide

The growth rate of the hydrogel of the aqueous konjac glucomannan (KGM) solution containing sodium trimetaphosphate (STMP) dialyzed with aqueous NaOH was investigated in a rectangular cell. The growth rate of the KGM-STMP gel depended on both the KGM and STMP concentrations in addition to the NaOH concentration. The initial growth rate of the KGM-STMP gel was closely related to the diffusion of NaOH into the KGM-STMP solution, leading to the ring-opening reaction of STMP and the deacetylation of KGM at the interface. The time course of the gelation of the KGM-STMP solution was analyzed on the basis of the moving boundary picture theory by introducing the characteristic length to express the consumption of NaOH in the gel layer accompanying the decomposition of STMP. Dynamic mechanical measurements were performed to compare the gelation of the KGM-STMP solution mixed homogeneously with dilute NaOH and the gel dynamics by the dialysis method.

The role of ionic clusters in the determination of the properties of partially neutralized ethylene-acrylic acid ionomers

Ionomers with different degree of neutralization were prepared from an ethylene-acrylic acid copolymer of 8.5 wt% acrylic acid content. The ionomers were characterized by Fourier transform infrared spectroscopy, small angle X-ray scattering, differential scanning calorimetry and dynamic mechanical thermal analysis measurements as well as rheology and tensile testing. The main relaxing species in ionomers are the methylene groups and the ethylene-acrylic acid copolymer segments. The mobility of these latter decreases upon neutralization and above a critical degree of neutralization a phase consisting of polyethylene segments attached to ionic clusters forms. The crystalline structure of the polymer contains primary and secondary crystallites. The amount and regularity, i.e. lamella thickness, of the latter decrease with increasing neutralization. Multiplets form from ionic species already at a small degree of neutralization and then they associate into clusters with increasing size as ion content increases. The mechanical properties of the ionomers are determined by their crystalline structure and cluster formation. Clusters increase strength and modulus, while decrease deformability. The combined effect of the two factors (crystallinity, cluster size) on stiffness was successfully described by a simple model.

Carbon nanotube enhanced shape memory epoxy for improved mechanical properties and electroactive shape recovery

This paper focuses on the processing, fabrication and characterization of a novel carbon nanotube (CNT) based electroactive shape memory epoxy nanocomposite with significant improvements in static and dynamic mechanical properties. Electro-active shape memory specimens have been fabricated by soaking CNT membranes (buckypaper) in shape memory epoxy polymer (SMEP) through a specialized fabrication process developed in-house that results in a high CNT wt. fraction of 30 wt%. The novel fabrication approach leads to drastic improvement in mechanical performance due to effective interfacial interaction between the SMEP and CNTs at the nanoscale. This is accomplished as the SMEP thoroughly permeates the buckypaper through the nano- and micro-pores, owing to the microstructure-induced capillary action. The improvement in quasistatic and dynamic mechanical properties of the baseline SMEP using CNT buckypaper is demonstrated and correlated with the microstructure through scanning electron microscopy characterization. For the buckypaper-enhanced SMEP (CNT-SMEP), the improvement in elastic modulus in the temperature extremes of 20 and 50ׄ°C was found to be 52% (1810 MPa compared to 2740 MPa) and 514% (7.6 MPa compared to 46.7 MPa), respectively. Furthermore, through the dynamic mechanical measurements, the increase in storage modulus in the range of 30-90ׄ°C was found to be 60% and 82%, respectively. In addition, the shape memory recovery response for this material system is characterized by stress-free electrical actuation of the CNT-SMEP using a 12V DC supply as well as using stress and temperature control testing.

The role of octadecylamine as zirconium phosphate intercalating agent on poly(vinyl alcohol)/poly(N-vinyl-2-pyrrolidone) biodegradable systems

Biodegradable ternary systems based on poly(vinyl alcohol)/poly(N-vinyl-2-pyrrolidone)/octadecylamine-containing zirconium phosphate were studied. Firstly, the synthesis and intercalation of lamellar zirconium phosphate were accomplished. As precursors, phosphoric acid (H3PO4) and zirconium(IV) oxide chloride 8-hydrate (ZrOCl2·8H2O) were used in the ratio P:Zr equals 18. ZrP d-spacing was expanded by octadecylamine as an intercalating agent using 1:1 amine:ZrP molar ratio. Ternary systems based on mixing of PVA and PVP water solution at different proportions (30/70, 50/50 and 70/30 mass/mass%) plus the addition of ZrPOct (2 mass%) were carried out. Infrared spectroscopy revealed that the interaction of PVA and ZrPOct was prominent evidencing an action of octadecylamine as compatibilizing agent. X-ray diffraction showed the decrease in PVA crystal size and the ZrPOct new diffraction angles as a function of the arrangement of polymers inside of the ZrPOct. Mass loss derivative thermogravimetric curves indicated polymer segregation and the decrease in PVA rich phase thermal stability. PVA crystallinity degree (Xc), cold crystallization and melting temperatures (Tcc and Tm) were drastically influenced by PVA/PVP compositions and ZrPOct. Dynamic-mechanical measurements supported that octadecylamine altered the polymer–polymer interaction acting as compatibilizing agent. Also, multiphase systems were reached owing to the free and linked octadecylamine molecules which provided variable polymer molecular motion and PVA/PVP participation effectiveness degree of each rich phase. The system was thought for future application as a control drug delivery.

Preparation of polyurethane composites reinforced with halloysite and carbon nanotubes

AbstractPolyurethane composites were synthesized using carbon nanotube (CNT) and CNT‐halloysite (HNT) hybrid in different amounts. Thermal, rheological, and mechanical properties of the composites were studied using thermogravimetric analysis, rheometrics mechanical spectrometry, dynamic mechanical thermal analysis, stress‐strain analysis, and hardness measurement. In this context, phase separation, elastic modulus, the Young's modulus, damping, tensile strength, ductility, thermal degradation, hardness, and conductivity were measured and discussed in detail. Modulus, tensile strength, and hardness were increased by 69%, 29%, and 1%, respectively, with incorporation of CNT, while tensile strength was reduced in the hybrid composites containing CNT‐HNT hybrid. In addition, hard and soft segment phase separation and melting points were increased up to 0.8% and 21%, respectively, by the addition of CNT. However, these characteristics were reduced with the addition of CNT‐HNT hybrid in the related composites. Uniform dispersion of HNT and CNT in the polyurethane matrix is clearly shown in the transmission electron microscopy images.

Synthesis, characterization and applications of poly(vinyl chloride) nanocomposites loaded with metal oxide nanoparticles

Metal oxide (i.e., Fe2O3, ZnO and TiO2) nanoparticles (NPs) have been prepared and investigated by various techniques with the objective of synthesis of nanocomposites thin films based on poly(vinyl chloride) (PVC) as a matrix. Different loadings of metal oxide NPs (i.e., 2.0, 5.0, 10.0 and 15.0 wt%) were incorporated in PVC followed by solution casting. The prepared film samples were characterized by X-ray diffraction (XRD), Raman spectra, scanning electron microscopy (SEM), dynamic mechanical analysis (DMA), thermal and electrical measurements. Also, the antibacterial activity was tested against Gram-positive (i.e., Bacillus subtilis and Staphylococcus aureus) and Gram-negative bacteria (i.e., Escherichia coli and Pseudomonas aeruginosa). The results were discussed in relation to metal oxide NPs content and type. XRD of the prepared nanocomposite films was almost the same as that of mixed ZnO metal oxide NPs with an amorphous region of PVC. Raman spectra suggested that ZnO NPs were just physically inserted into PVC matrix. SEM revealed a homogeneous distribution of the NPs on using 10 wt% in PVC matrix, while the NPs agglomerations at higher content (i.e., 15 wt%) were formed. The dynamic mechanical results, as a function in temperature, indicated an increase in the storage and loss moduli and a decrease in loss factor tan δ with shifting to higher glass transition temperature, with increasing metal oxide NPs content up to 10 wt%. Thermal gravimetric analysis revealed that utilizing Fe2O3 and TiO2NPs in PVC matrix improved thermal stability of PVC in comparison with ZnO NPs with catalytic behavior and polymer decomposition acceleration. Metal oxide Nps increased the electrical conductivity of PVC, the electrical conductivity values were found to be in the order of 10−13 for ZnO, while it is in the order of 10−11 for Fe2O3 and TiO2. This finding is highly recommended such composites to be used in antistatic applications as the needed range for such application is 10−9–10−14Ω−1 cm−1. Metal oxide nanocomposites improved the antibacterial activity of PVC toward both types of bacteria and can be used as an effective antibacterial agent in biomedical healthy applications.

Improving through‐thickness conductivity of carbon fiber reinforced polymer using carbon nanotube/polyethylenimine at the interlaminar region

AbstractThe through‐thickness conductivity of carbon fiber reinforced polymer (CFRP) composite was increased by incorporating multiwalled carbon nanotubes in the interlaminar region. Carbon nanotubes (CNTs) were dispersed in a polyethylenimine (PEI) binder, which was then coated onto the carbon fiber fabric. Standard vacuum‐assisted resin infusion process was applied to fabricate the composite laminates. This modification technique aims to enhance the electrical conductivity in through‐thickness direction for the purpose of nondestructive testing, damage detection, and electromagnetic interference shielding. CNT concentrations ranging from 0 to 0.75 wt% were used and compared to pristine CFRP samples (reference). The through‐thickness conductivity of the CFRP exhibited an improvement of up to 781% by adopting this technique. However, the dispersion of CNT in PEI led to a viscosity increase and poor wetting properties which resulted in the formation of voids/defects, poor adhesion (as shown in scanning electron micrographs) and the deterioration of the mechanical properties as manifested by interlaminar shear strength and dynamic mechanical analysis measurements.

Investigation of Thermophysical Properties of AW-2024-T3 Bare and Clad Aluminum Alloys.

In this paper, thermophysical and viscoelastic dynamic mechanical measurements (DMA) were performed for bare and clad aluminum AW-2024-T3 alloys. Specific heat, thermal diffusivity, and dynamic module (storage and loss) tests were performed in the range of 50 to 500 °C, except for DMA ones (RT–400 °C). All tests were carried out using the following specialized measuring stands: a light flash apparatus (LFA), differential scanning calorimeter (DSC), and a dynamic mechanical analyzer (DMA). The microstructures and compositions of alloys were investigated by light microscope (LM), scanning electron microscope (SEM), and energy-dispersive X-ray spectroscopy (EDS). Furthermore, Vickers micro-hardness measurements were conducted prior to and after DSC studies. Different precipitation kinetics of the θ′ and S′ metastable phases in the bare 2024-T3 compared to the clad alloy were observed by DSC. Additionally, the DSC results for a few selected scan rates were analyzed by the Kissinger method to give activation energies for the precipitation of θ′ and S′ metastable phases in the alloys. The apparent activation energy of the θ′ and S′ phases corresponds to 137.1 ± 4.4 for the bare alloy and 131.0 ± 6.0 (exo) and 104.1 ± 2.1 (exo) (two peaks) for the clad alloy.

Effects of temperature increase during surgical drilling in acrylic resin.

Acrylic resin is employed for drilling bone biomodels. Since drilling causes temperature rise, the mechanical properties of thermoplastic acrylic resin can be altered, consequently affecting drilling properties. However, it is currently unclear how this temperature increase impacts drilling. This study reports the effects of temperature rise on both mechanical and drilling properties through experiments in which acrylic resin is drilled under machining conditions employed in surgical operations. Drilling tests were performed using a surgical drill on medical acrylic resin under dry conditions to observe generated cutting chips and measure drilling properties such as torque, drilling time, and temperature rise. Dynamic mechanical analysis measurements were performed to consider temperature effects. According to the morphological classification of the cutting chips, the drilling process is divided into three phases corresponding with the generation of cylindrical helix, waved, and rounded nubby chips respectively. During drilling, the temperature of the chips can exceed the glass transition temperature (100∘C) resulting in decreased viscoelasticity, which is associated with decreased torque. While drilling acrylic resin under surgical machining conditions, increasing temperature can decrease torque and morphologically change cutting chips due to the decrease in mechanical properties above the glass transition temperature.

Stable ion bond for high damping, high wet resistance, and low rolling resistance high vinyl polybutadiene rubber‐based dicarboxylate ionomer

AbstractSince the implementation of European Union (EU) tire label, the focus of recent attention has been focused on high performance green tire with low rolling resistance, high wet resistance, low noise, and excellent auto‐braking properties. However, it is a significant challenge to simultaneously achieve these performances for rubber materials. In this research, we developed a novel concept on the construction of stable ion bonds for high performance high vinyl polybutadiene rubber (HVBR)‐based dicarboxylate ionomers. HVBR‐based dicarboxylate sodium ionomer (hereafter referred as Na ionomer) was fabricated through complexation reaction of some or all of carboxylic functional groups on the preprepared maleinized HVBR molecular chains with sodium hydroxide. In the case of Na ionomers, the formation of sodium carboxylate group was certified from Fourier transform infrared spectra. Physical and dynamic mechanical measurements indicated that the tensile strength, wear resistance, wet skid resistance, dry sliding resistance, low rolling resistance, and low heat buildup of the Na ionomer were significantly improved compared to that of HVBR, and Na ionomer simultaneously showed better damping properties and the effective damping temperature range was broadened from −8.8 to 30.1°C, which was closer to the room temperature. Consequently, the approach and results collectively represent a significant advance toward the development of high performance green tire rubber materials.

Understanding puffing in a domestic microwave oven

AbstractThis work is intended to develop an overall understanding of puffing of a starch‐based snack in a home microwave oven, using primarily the microwave energy. Combination of experimental measurements was used, including dynamic mechanical thermal analysis, CT‐Scan, SEM, image processing, and measurement of temperature, moisture content, and expansion ratio. Effects of various product and process parameters on puffing, including those of pretreatment to produce the half product, were studied. Experimental data showed that the physicochemical processes contributing to crust formation were gelatinization of starch, migration of soluble ingredients to the surface, and shrinkage at the surface. A thicker material was harder to puff due to its increased mechanical resistance. Higher microwave power, leading to higher rate of evaporation, increased expansion. Evolution of mechanical properties of the crust greatly affected the final shape of the puffed product. In overall understanding, critical determinants of a puffing process were attributed to three material factors (reduced surface permeability, optimal moisture content, and deformability) and two process factors (intense heat and higher internal pressure from evaporation).

Double-step moulding: An effective method to induce the formation of β-phase in PVDF

Nowadays, the investigation of smart methods promoting PVDF β phase has become an important research topic in many energy related fields. In this work, compression moulding was proposed as an effective, simple and easy-scalable technique to tune PVDF polymorphism and obtain the desired crystalline form, exploiting a procedure in two steps. After a preliminary principal component analysis of the infrared spectra, the different moulding conditions tested were correlated with the electroactive phase amount, obtaining a non-monotonous trend. Finally, dielectric and dynamic-mechanical measurements were carried out on selected samples. Experimental evidence indicates that the double-step moulding induces the β phase formation due to the orienting effect generated by the shear stresses in the not completely molten polymer. Moreover, this method determines an increase in permittivity, a reduction of the dielectric losses and a change of PVDF molecular relaxations with respect to the reference film moulded through a simple single-step moulding.

Reprocessable polybenzoxazine thermosets crosslinked by mussel-inspired catechol-Fe3+ coordination bonds

The traditional thermosets cannot be reprocessed, which causes serious environmental pollution and resource waste. The catechol-Fe3+ coordination bonds existing in marine mussel byssal cuticle provide a reversible crosslinking structure for reprocessable thermosets. A reprocessable polybenzoxazine thermoset (PBOZ-dopa45-Fe3+) by catechol-Fe3+ coordination bonds was synthesized successfully based on mussel-inspired chemistry and benzoxazine chemistry. Firstly, benzoxazine monomers containing carboxyl groups were synthesized. Secondly, polybenzoxazine with carboxyl groups was obtained through thermal ring-opening polymerization. And then catechol groups were grafted onto the pendant groups of polybenzoxazine. Finally, the reprocessable polybenzoxazine was obtained by catechol groups coordinating with Fe3+. The structure of polybenzoxazine was characterized by NMR, FTIR and SEC measurements. The formation of reversible crosslinked network composed of catechol-Fe3+ coordination bonds is confirmed by UV–Vis absorbances, system color changes, and dissolution states in methanol solutions of different pH. Reprocessing experiments indicate that the reversible catechol-Fe3+ coordination bonds endow remarkable reprocessability of cured resin. Dynamic mechanical measurements and thermogravimetric measurements show that the PBOZ-dopa45-Fe3+ can still maintain excellent thermal properties. Cross-linking by catechol-Fe3+ coordination bonds provides a new way for the preparation of reprocessable thermosets.

Self-healing nanocomposites comprised of poly(urea formaldehyde) nanocapsules in a thermosetting polyurea

In this study, poly(urea formaldehyde) (PUF) nanocapsules with epoxy cores were blended into a polyurea matrix, formulated as poly[(phenyl isocyanate)–co-formaldehyde] (PMDI) (f = 3.4), and a diamine curing agent (VERSALINK 650) to form nanocomposites. The nanocomposites were then subjected to impact delamination tests at temperatures below −74 °C. Scanning electron microscopy was used to qualitatively inspect the nanocomposites before the impact (virgin), after the impact, and after self-healing. Dynamic mechanical analyzer measurements were carried out to characterize the mechanical properties of the nanocomposites. Specifically, their stiffness was characterized by the storage modulus, and damping by the loss modulus. The influence of the curing agent and the loading concentration of the PUF nanocapsules on the morphology and mechanical properties of the nanocomposites were investigated in order to optimize the cure rate, distribution, and loading concentration of the PUF nanocapsules in the polyurea matrix. It was found that when 1 wt% PUF-epoxy nanocapsules were loaded into the polyurea, the recovery of the storage modulus after impact, which was used to characterize self-healing, was found to be 32 ± 1% and 56 ± 1% after 3 and 30 days, respectively.

Overmolded hybrid composites of polyamide-6 on continuous carbon and glass fiber/epoxy composites: ‘An assessment of the interface’

In this study, we investigated overmolding of thermoplastics on thermoset composites as an alternative joining method, in order to enable production of hybrid thermoset composites. Specifically, we explored the parameters affecting adhesion between overmolded polyamide-6 (PA6) and continuous glass or epoxy fiber-reinforced composites. Three main factors were studied: type of reinforcing fiber (carbon and glass), moulding temperature during overmolding process (30 °C and 80 °C), and application of peel-ply on composite surface. Overall, peel ply application, higher mould temperature (80 °C) and composite surface with carbon fiber reinforcement resulted in better adhesion. Three point bending, dynamic mechanical analysis (DMA), roughness, and contact angle measurements reveal strong bonding. Scanning electron microscopy (SEM), micro-computed tomography (micro-CT) images and energy-dispersive X-ray spectroscopy (EDS) results support the improvement due to peel-ply application. Findings from thermal analysis confirm the effect of reinforcement material type on crystallinity of overmolded polymer and underline the essential role of contact surface chemistry.

In situ TEM observations of high-strain-rate deformation and fracture in pure copper

Abstract The plastic deformation of polycrystalline metals at high strain rates is controlled by the way defects (dislocations and twins) nucleate, propagate, and interact in the microstructure. To-date, the role of these defects has been estimated based on dynamic mechanical measurements coupled with ex situ investigations of the deformed microstructure. However, such investigations are fundamentally limited in their ability to characterize transient mechanisms. Here, we present for the first time direct, experimental observations of the nucleation, motion, and interaction of defects and cracks during deformation of pure copper at strain rates between 103 and 104 s−1. These observations are enabled by coupling a custom-built in situ high-rate straining stage with nanosecond-resolution dynamic transmission electron microscopy. The results show that while twins play only a minor role in the deformation of copper at quasi-static strain rates, the twin nucleation rate increases markedly at high strain rates. The preferred nucleation sites for twins also change, and the new twin interfaces become preferential paths for crack propagation, facilitating fracture through the original grains.

Long period grating in a multimode cyclic transparent optical polymer fiber inscribed using a femtosecond laser.

In this Letter, we report, to the best of our knowledge, the first inscription of long period gratings (LPGs) in a multimode cyclic transparent optical polymer (CYTOP) fiber using a femtosecond laser inscription method. The LPG was inscribed directly in the center of the fiber core, tailored for operation at 1560nm. The CYTOP-LPG was characterized in transmission, and its response for relative humidity and temperature was measured. The humidity measurements, to the best our knowledge, are the first for a POF-LPG, whereas the temperature sensitivity is significantly higher than reported in other works. In addition, dynamic mechanical measurements were performed comparing the mechanical characteristics of the laser exposed sections of the polymer fiber, where the LPG was inscribed, with the unexposed regions.