Application of a Portable Handheld Infrared Spectrometer for Quantitation of <Emphasis Type="Italic">trans</Emphasis> Fat in Edible Oils

Trans fat poses serious health risks to consumers. In order to meet the FDA labeling requirements for trans fatty acids, development of fast, accurate, easy-to-use analytical methods for oils, fats and related products is desirable. Fourier transform infrared spectroscopy (FTIR) is a well-established analytical technique for quantifying trans fats, and the development of handheld FTIR units over the past decade presents new application opportunities. Our objective was to evaluate the performance of a handheld FTIR sensor for measuring trans fat content between 0.1 and 20% trans (w/w) in edible saturated and unsaturated oils. Calibration models were built by measuring height of the band at 966 cm⁻¹ and by partial least squares regression (PLSR) using benchtop FTIR as a reference method. Predictive accuracy of the models was validated with an independent test set of commercial edible oils. Calibration models developed using PLSR and linear regression of band heights gave correlation coefficients R ² > 0.98. Multivariate analysis for the handheld unit gave standard error of prediction (SEP) of approximately 1%, comparable to values obtained with benchtop systems. This study demonstrates that handheld FTIR spectroscopy coupled with chemometrics is a suitable method for quantitation of trans fat content.     

Kinetic study of the reaction between hydroxyl-terminated polybutadiene and isophorone diisocyanate in bulk by quantitative FTIR spectroscopy

A kinetic study of the reaction between a hydroxyl-terminated polybutadiene (HTPB) and isophorone diisocyanate (IPDI) was carried out in the bulk state by using quantitative Fourier transform infrared (FTIR) spectroscopy. The reaction is shown to obey a second-order rate law, being first order in both the HTPB and IPDI concentrations. The activation parameters obtained from the evaluation of kinetic data are ΔH‡ = 41.1 ± 0.4 kJ mol, ΔS‡ = −198 ± 2 J K⁻¹ mol⁻¹ and E_a = 43.8 ± 0.4 kJ mol⁻¹, which are quite different from the solution values. However, they are in agreement with the results obtained on propellants by torsional braid measurements. The large negative value of the activation entropy is indicative of an associative mechanism, which is in accord with the second-order rate law for the polyurethane formation. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1979–1983, 1997     

A new method for determining gossypol in cottonseed oil by FTIR spectroscopy

A new method was developed to determine the gossypol content in cottonseed oil using FTIR spectroscopy with a NaCl transmission cell. The wavelengths used were selected by spiking clean cottonseed oil to gossypol concentrations of 0–5% and noting the regions of maximal absorbance. Transmittance values from the wavelength regions 3600–2520 and 1900–800 cm⁻¹ and a partial least squares (PLS) method were used to derive FTIR spectroscopic calibration models for crude cottonseed, semirefined cottonseed, and gossypol-spiked cottonseed oils. The coefficients of determination (R ²) for the models were computed by comparing the results from the FTIR spectroscopy against those obtained by AOCS method Ba 8-78. The R ² were 0.9511, 0.9116, and 0.9363 for crude cottonseed, semirefined cottonseed, and gossypol-spiked cottonseed oils, respectively. The SE of calibration were 0.042, 0.009, and 0.060, respectively. The calibration models were cross-validated within the same set of oil samples. The SD of the difference for repeatability and accuracy of the FTIR method were better than those for the chemical method. With its speed (ca. 2 min) and ease of data manipulation, FTIR spectroscopy is a useful alternative to standard wet chemical methods for rapid and routine determination of gossypol in process and/or quality control for cottonseed oil.     

Synthesis and characterization of copolymer of styrene with methacrylic acid initiated by triphenylbismuthonium 1,2,3,4‐ tetraphenylcyclopentadienylide

The radical copolymerization of styrene with methacrylic acid (MAA) initiated by triphenylbismuthonium 1,2,3,4‐tetraphenylcyclopentadienylide in dioxan at 80 ± 0.1 °C for 3 h results in the formation of alternating copolymer as evidenced from the values of reactivity ratios as r₁ (styrene) = 0.03 and r₂ (MAA) = 0.025. The kinetic expression is R_p α [I]^0.5 [Sty] [MAA] and overall energy of activation is computed to be 23 kJ/mol. The FTIR spectrum of the copolymer shows the presence of bands at 3054 cm^?1 assigned to the phenyl group of styrene and at 1724 cm^?1 assigned to the ? COOH group of MAA. The ¹H‐NMR spectrum of the copolymer shows peaks between 7.20 and 7.27 δ assigned to the phenyl protons of styrene and at 12.5 δ assigned to the COOH proton of MAA. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1838–1843, 2005     

Multivariate determination of cloud point in palm oil using partial least squares and principal component regression based on FTIR spectroscopy

A rapid FTIR spectroscopic method was developed for quantitative determination of the cloud point (CP) in palm oil samples. Calibration samples were prepared by blending randomized amounts of palm olein and palm stearin to produce a wide range of CP values ranging between 8.3 and 47.9°C. Both partial least squares (PLS) and principal component regression (PCR) calibration models for predicting CP were developed by using the FTIR spectral regions from 3000 to 2800 and 1800 to 1600 cm⁻¹. The prediction capabilities of these calibration models were evaluated by comparing their standard errors of prediction (SEP) in an independent prediction set consisting of 14 palm oil samples. The optimal model based on PLS in the spectral range 1800-1600 cm⁻¹ produced lower SEP values (2.03°C) than those found with the PCR (2.31°C) method. FTIR in conjunction with PLS and PCR models was found to be a useful analytical tool for simple and rapid quantitative determination of CP in palm oil.     

Determination of thermal cure kinetics of thin films of photocatalysed dicyanate ester by FTIR emission spectroscopy

Emission Fourier transform infrared (FTIR) spectroscopy has been found to be a suitable technique for monitoring the thermal cure of thin films of photocatalysed dicyanate ester resins. The kinetics of the polymerization of a commercial cyanate ester resin (AroCy RTX‐366) catalysed by an organometallic compound, tricarbonyl cyclopentadienyl manganese (CpMn(CO)₃), have been determined using this technique and the results compared with those obtained from transmission FTIR. The trimerization reaction rate of the resin is found to have a first order dependence upon both the cyanate fraction and the active catalyst concentration until diffusion control occurs. To elucidate the mechanism, a system with premade catalyst, which was the photoreaction product of the resin and the organometallic compound, has also been studied. The activation energy for this system is 91 ± 10 kJ mol⁻¹ compared to 72 ± 8 kJ mol⁻¹ for the directly irradiated system. This may arise from different distributions of three photoproducts identified as complexes between manganese and the cyanate ester. © 2000 Society of Chemical Industry     

Determination of tacticity in polypropylene by FTIR with multivariate calibration

A method for determination of tacticity in polypropylene (PP) using FTIR associated with multivariate analysis is presented. Blends of PP with known tacticity were prepared with isotactic, syndiotactic, and atactic polymer and analyzed by ¹³C‐NMR. The FTIR spectra were recorded and processed through principal components regression (PCR) and partial least‐squares regression (PLS), using information from several different portions of the spectra. The method was compared with the classical methods of tacticity determination by FTIR based on the intensities of the bands at 998 cm^?1 (isotactic), 868 cm^?1 (syndiotactic), and 975 cm^?1 (internal standard), which are known to be dependent on the crystallinity of the polymer and, thus, affected by temperature and sample preparation. The models obtained with multivariate calibration, both with PCR and PLS, gave prediction errors up to fivefold smaller than that of the classical methods, and were also shown not to be heavily dependent on the bands that are affected by the crystallinity of the polymer, but rather on the methyl and methylene bendings at 1375 and 1462 cm^?1. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 734–745, 2002     

Characterization of chemically modified wood fibers using FTIR spectroscopy for biocomposites

Chemical modifications of wood fibers (Lignocel® C120) were performed for biocomposite applications, and chemically modified wood fibers were analyzed by FTIR spectroscopy. NaOH treatment showed band shifts from Cell‐I to Cell‐II in FTIR spectra from 2902 cm^?1, 1425 cm^?1, 1163 cm^?1, 983 cm^?1, and 897 cm^?1 to 2894 cm^?1, 1420 cm^?1, 1161 cm^?1, 993 cm^?1, and 895 cm^?1 and the change in peak height at 1111 cm^?1 and 1059 cm^?1 assigned for Cell‐I structure. Silane treatment showed peak changes at 1200 cm^?1 assigned as Si? O? C band, at 765 cm^?1 assigned as Si? C symmetric stretching bond, at 700 cm^?1 assigned as Si? O? Si symmetric stretching, and at 465 cm^?1 assigned as Si? O? C asymmetric bending. Benzoyl treatment resulted in an increase in the carbonyl stretching absorption at 1723 cm^?1 and in band characteristics of aromatic rings (1604 cm^?1 and 710 cm^?1) and a strong absorption at 1272 cm^?1 for C? O band in aromatic ring. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Study of crosslinking AMS/DGEBA system by FTIR

Fourier transform infrared spectroscopy (FTIR) was used to follow the curing of the diglycidylether of bisphenol A (DGEBA) typical epoxide resin by poly(styrene-alt-maleic anhydride) (AMS), the reaction being accelerated by triethylamine (TEA) in the presence of methanol. The study was done in an isothermal mode for four temperatures: 85, 82, 80, and 75°C. We followed, for each temperature, the variation of the area of the epoxy band (916 cm⁻¹) versus time. After 200 min of reaction, the degree of conversion of epoxy is 0.5 at 85°C. A postcure at 100°C during 96 h allows one to reach a total conversion of epoxy. The reaction mechanism involves three steps to form the tridimensional network. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1167–1178, 1998     

Irreversibility of stretching‐induced local conformational changes as verified through an FTIR dichroism study for PVC

The dichroic behaviour of 615 and 637 cm⁻¹ bands of the IR spectrum of poly(vinyl chloride) (PVC) has been analysed through FTIR measurements on PVC films stretched to various elongation ratios. By comparing the evolution both of the dichroic ratios and of the relative absorbance of those bands in the perpendicular direction to that of stretching, the occurrence of local chain orientation related to the conformational change GTTG⁻TT⇒ GTGTTT at mmr isotactic tetrads can be differentiated from the normal orientation of syndiotactic sequences, so confirming earlier proposals that the above conformational change takes place when stretching PVC. © 1999 Society of Chemical Industry     

Novel method for rapid monitoring of lipid oxidation by FTIR spectroscopy using disposable IR cards

A new FTIR approach was investigated for assessing edible oil oxidative stability with the use of polymer IR (PIR) cards as sample holders. This approach allows oil oxidation to be monitored at moderate temperatures owing to the fairly rapid rate at which unsaturated oils oxidize on the PIR cards. To assess the FTIR/PIR card method, pure TAG—triolein, trilinolein, and trilinolenin—were loaded onto cards and placed in a chamber where warm air (55°C) flowed over them continuously to facilitate oxidation. At periodic intervals, individual cards were removed and their FTIR spectra scanned, after which they were replaced in the aeration chamber. All spectra were normalized to compensate for variations in PIR card path lengths or oil loadings, and for each card the initial spectrum recorded (t=0) was subtracted from all subsequent spectra taken over time to produce differential spectra. With the use of a peak-find algorithm, the absorbance minimum in the cis region (3017–3000 cm⁻¹) and the absorbance maxima in the hydroperoxide (3550–3200 cm⁻¹), isolated trans (977–957 cm⁻¹), and conjugated trans regions (995–983 cm⁻¹) were measured in the differential spectra and plotted as a function of time. For all three TAG, the loss of cis double bonds was linearly related to the development of hydroperoxides and isolated trans bonds for much of the oxidation process, whereas for the polyunsaturated TAG a similar relationship also existed for conjugated trans species. Based on experimentally determined hydroperoxide (ROOH) absorbance slope factor (0.06 mAbs/PV), ROOH absorbance changes were converted to PV, allowing direct PV monitoring as a function of time using the PIR cards. Trilinolenin, trilinolein, and triolein attained a PV of 100 mequiv/kg oil after, 43,98, and 2889 min, respectively, their relative reaction rates being similar to ratios published in the literature. The assessment of the FTIR/PIR card method using TAG indicates that it may be a practical and rapid means of oxidizing lipids and tracking their oxidative state in terms of PV so as to provide a measure of their oxidative stability.     

Evaluation of the Performance of a Portable Mid-Infrared Analyzer for the Rapid Determination of Total Trans Fat in Fast Food

The performance of a novel, transmission‐mode, portable, Fourier transform infrared (FTIR) analyzer was evaluated and compared to that of a benchtop attenuated total reflection (ATR)‐FTIR spectrometer. The total concentration of trans fatty acids in the fat extracted from 19 representative fast foods was rapidly (<5 min) quantified in a single measurement after conversion to fatty acid methyl esters (FAME). While the FTIR determination is rapid, the time required for extraction and derivatization is not. For all extracts, the total trans FAME concentration varied from approximately 0.5 to 11 % (of total FAME) as determined using the portable FTIR analyzer. The trans fat contents (mean ± SD), expressed in grams per serving and calculated on the basis of total fat content and FTIR determination of trans fat content, were found to be 1.00 ± 0.42 for hamburgers, 0.67 ± 0.78 for chicken tenders, 1.00 ± 1.24 for French fries, and 0.27 ± 0.23 for apple pies. Determinations of total trans‐unsaturated FAME were consistent with those obtained by use of ATR‐FTIR and GC official methods (AOCS Cd 14e‐09 and AOCS Ce 1j‐07, respectively). These results indicate that the portable FTIR analyzer is suitable for the rapid and routine quantification of total trans fat measured as FAME prepared from fats extracted from fast foods.     

Rapid FTIR determination of water,phenolics and antioxidant activity of olive oil

A rapid Fourier transformed infrared (FTIR) attenuated total reflectance (ATR) spectroscopic method was applied to the determination of water content (WC), total phenol amount (TP) and antioxidant activity (ABTS ^{. +}) of virgin olive oils (VOO) and olive oils. Calibration models were constructed using partial least squares regression. Oil samples with WC ranging from 289 to 1402 mg water/kg oil, with TP from 46 to 877 mg gallic acid/kg oil and with ABTS ^{. +} from 0 to 5.7 mmol Trolox/kg oil were considered for chemometric analysis. Better results were obtained when selecting suitable spectral ranges; in particular, from 2260 to 1008 cm^?1 for WC, from 3610 to 816 cm^?1 for TP and from 3707 to 1105 cm^?1 for ABTS ^{. +}. Satisfactory LOD values by the FTIR‐chemometric methods were achieved: 9.4 (mg/kg oil) for WC; 12.5 (mg gallic acid/kg oil) for TP, and 0.76 (mmol Trolox/kg oil) for ABTS ^{. +}. The evaluation of the applicability of these analytical approaches was tested by use of validation sample sets (n = 16 for WC, n = 11 for TP and n = 14 for ABTS) with nearly quantitative recovery rates (99–114%). The FTIR–ATR method provided results that were comparable to conventional procedures. Practical applications : The presented method is based on ATR–FTIR in combination with multivariate calibration methodologies and permits a simultaneous evaluation of important quality parameters of VOO (WC, TP and ABTS ^{. +}). This approach represents an easy and convenient means for monitoring olive oil quality with the advantage of ease of operation, speed, no sample pretreatment and no consumption of solvents. The data obtained with this method are comparable to those obtained using the official reference method. Therefore, the technique is highly plausible as an alternative to the standard procedure for routine analysis or control at‐line of production processes.     

Acrylonitrile content as a predictor of the captan permeation resistance for disposablenitrile rubber gloves

The aim of this study was to determine whether the acrylonitrile (ACN) content influences the permeation resistance of disposable nitrile rubber (NBR) gloves to aqueous solutions of the pesticide captan. Attenuated total reflectance/Fourier transform infrared (ATR–FTIR) spectrophotometry at 2237 ± 5 cm^?1 was used to measure the ACN contents of seven different NBR gloves. The ACN contents of the gloves ranged from 12.7 to 29.9%. Permeation was conducted according to American Society for Testing and Materials (ASTM) Method F 739‐99a with a gas chromatography/mass spectrometry analysis of captan in the hexane collection liquid. Significant correlations were found between (1) the ACN content and mass‐to‐area ratio and the logarithm of the steady‐state permeation rate (SSPR; Pearson correlation coefficient = 0.9227, p ≤ 0.05), and (2) the ACN content and mass‐to‐area ratio and the ASTM normalized breakthrough detection time (NBT) at 0.25 μg/cm² (Pearson correlation coefficient = 0.9471, p ≤ 0.05). On average, the NBT increased 120 min for every 5% increase in the ACN content. The average SSPR ranged from 0.002 to 0.40 μg/cm²/min, a 200‐fold difference. Increasing the ACN content resulted in decreased SSPR. ATR–FTIR was useful in determining the NBR polymer ACN content, surface homogeneity, and potential glove chemical resistance. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2057–2063, 2007     

Application of a Handheld Portable Mid-Infrared Sensor for Monitoring Oil Oxidative Stability

This study evaluated the capabilities of a handheld mid-infrared (MIR) spectrometer combined with multivariate analysis to characterize oils, monitor chemical processes occurring during oxidation, and to determine fatty acid composition. Vegetable oils (corn, peanut, sunflower, safflower, cottonseed, and canola) were stored at 65 °C for 30 days to accelerate oxidation reactions. Aliquots were drawn at 5 day intervals and analyzed by benchtop and portable handheld mid-infrared devices (4,000–700 cm⁻¹) and reference methods (IUPAC 2301 [1], 2302 [1]; AOCS Cd 8-58 [2]; and Shipe 1979 [3]). PLSR and soft independent modeling of class analogy (SIMCA) models were developed for oil classification and estimation of oil stability parameters. Models developed from MIR spectra obtained with a benchtop spectrometer equipped with a 3-bounce ATR device resulted in superior discriminative performances for classifying oils as compared to those obtained from handheld spectra (single-bounce ATR). Models developed from reference tests and handheld spectra showed prediction errors (SECV) of 1 meq/kg for peroxide value, 0.09% for acid value and 2% for determination of unsaturated fatty acids in different oils. Spectral regions ~3,012–2,850 cm⁻¹ (C–H stretching bands/shoulders of fatty acids), ~1,740 cm⁻¹ (C=O stretching of esters), and ~1,114 cm⁻¹ (–C–O stretching) were found to be important for prediction. Handheld-FTIR instruments combined with multivariate-analysis showed promise for determination of oil quality parameters. Portability and ease-of-use makes the handheld device a great alternative to traditional methods.     

Chelation of chitosan derivatives with zinc ions. II. Association complexes of Zn2+ onto O,N‐carboxymethyl chitosan

The chelation of zinc ions onto O,N‐carboxymethyl chitosan (ONCMCh) was characterized using a Fourier transform infrared (FTIR) spectrophotometer and a scanning electron microscope (SEM). From the FTIR spectra, little change in the absorption intensities and frequencies at 3300–3600 cm⁻¹ of Zn²⁺ ONCMCh chelated specimens suggested that  OH and  NH₂ groups were not participating in the chelation reaction. The absence of absorption bands at 1755–1700 cm⁻¹ suggested that the carboxyl group CO was not ionized, and the ionized CO bands were observed at 1400–1600 cm⁻¹ for chelated specimens. Thus, the chelation sites took place at the carboxyl group rather than at the  OH and NH₂ groups. It also confirmed that water‐insoluble chelates, which were formed through the Zn O and Zn N bonds, presented a tetrahedral structure. The water‐soluble complexes where zinc ions connected with oxygen of CO and water molecules were only due to electron attraction. Formation of different microstructures on the surfaces, as revealed by SEM, provided evidence to distinguish different chelating mechanisms between water‐soluble and water‐insoluble complexes. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1476–1485, 2001     

FTIR analaysis of coal. 1. techniques and determination of hydroxyl concentrations

The preparation of coal samples for the determination of hydroxyl content by FTIR is described. It is concluded that the FTIR method provides good quality infrared spectra on opaque materials such as coal and char. If sample preparation procedures are followed carefully, quantitative spectra of coals can be reproduced within ±5%. Beer's law is followed in the range 0.3–1.3 mg of coal/cm². The broad absorbance in the range 2000–3600 cm^?1 appears when using several different preparation techniques and is caused by hydrogen-bonded OH. The use of quantitative FTIR specta offers a simple method of estimating the hydroxyl content of a coal. Reasonable results have been obtained despite the problem of interference by water. The KBr pellets were dried for 48 h at 105 °C and the absorbance was reduced at 3200 cm^?1 and the problem of scattering was minimized by using a rectilinear baseline. With these procedures the hydroxyl oxygen concentrations in the coal were determined to an accuracy of ±10%.     

Determination of monomer reactivity ratios using in situ FTIR spectroscopy for maleic anhydride/norbornene‐free‐radical copolymerization

Monomer reactivity ratios for maleic anhydride (MAH) and norbornene (Nb) free‐radical copolymerizations were estimated by using a linear graphical method, which is based upon the terminal model developed by Mayo and Lewis. Reactions were performed by using optimized reaction conditions that were previously determined. MAH/Nb copolymerizations (3 mol % AIBN initiator, 60% solids in THF, 65°C, 24 h). Copolymerization data were collected via in situ FTIR to low degrees of conversion (～ 10%) for copolymerizations of MAH and Nb. The following five different MAH/Nb comonomer feed molar ratios were analyzed: 40/60, 45/55, 50/50, 55/45, and 60/40. Conversion data that were measured with in situ FTIR were employed in the rearranged copolymer composition equation to estimate MAH and Nb reactivity ratios. Both of the reactivity ratios were determined to be near 0 (r_MAH = 0.02, r_Nb = 0.01), which was indicative of an alternating copolymerization mechanism. The highest observed rate constant for copolymerization was obtained at an equal molar concentration of monomers. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3240–3246, 2004     

Palm oil analysis in adulterated sesame oil using chromatography and FTIR spectroscopy

This study highlights the application of two analytical techniques, namely GC‐FID and FTIR spectroscopy, for analysis of refined‐bleached‐deodorized palm oil (RBD‐PO) in adulterated sesame oil (SeO). Using GC‐FID, the profiles of fatty acids were used for the evaluation of SeO adulteration. The increased concentrations of palmitic and oleic acids together with the decreased levels of stearic, linoleic, and linolenic acids with the increasing contents of RBD‐PO in SeO can be used for monitoring the presence of RBD‐PO in SeO. Meanwhile, FTIR spectroscopy combined with multivariate calibration of partial least square (PLS) has been successfully developed for the detection and quantification of RBD‐PO in SeO using the combined frequencies of 3040–2995, 1660–1654, and 1150–1050 cm^?1. The values of coefficient of determination (R²) for the relationship between actual versus FTIR‐calculated values of RBD‐PO in SeO and root mean square error of calibration (RMSEC) obtained are 0.997 and 1.32% v/v, respectively. In addition, using three factors, the root mean square error of prediction (RMSEP) value obtained using the developed PLS calibration model is relatively low, i.e., 1.83% v/v. Practical Application: The adulteration practice is commonly encountered in fats and oils industry. It involves the replacement of high value edible oils such as sesame oil with the lower ones like palm oil. Gas chromatography and FTIR spectroscopy can be used as reliable and accurate analytical techniques for detection and quantification of palm oil in sesame oil.     

Real‐time FTIR and WAXS studies of drawing behavior of poly(ethylene terephthalate) films

The development of molecular orientation and crystallization was studied during uniaxial drawing of poly(ethylene terephthalate) (PET) films, which was immediately followed by subsequent taut annealing at the drawing temperature. The behavior was monitored in real time throughout the drawing and annealing using dynamic FTIR spectroscopy and in situ WAXS measurements using the Daresbury Synchrotron Radiation Source. Films were drawn at 80 and 85°C at varying strain rates (0.001–0.7 s⁻¹). The true stress–strain behavior was determined at each of the drawing conditions and the density and optical anisotropy of unloaded samples was measured. The IR spectra were analyzed using curve reconstruction procedures developed previously, and they showed that orientation of the phenylene groups and the trans glycol conformers occurred before significant gauche–trans conformational changes could be seen. The onset of crystallization, defined as the point that the crystalline 1 05 reflection could be first observed using WAXS, was not found to correlate with any specific change in the proportions of trans and gauche isomers nor with any feature on the stress–strain curve. However, it was clear that, for these comparatively low strain rates, crystallization occurred during the drawing process while the crosshead was moving and the draw ratio was increasing. The orientation of the crystallites was calculated from the 1 05 reflection observed in a tilted film, transmission geometry. The crystallites were found to form at a draw ratio of about 2.5 with high orientation values (P₂ > 0.8) that increased during drawing and annealing to P₂ values of 0.95, irrespective of the drawing conditions. Semiquantitative measurements of crystallinity showed that the fraction of crystalline material that developed during drawing decreased with increasing strain rate. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1825–1837, 2001