Studies on the thermal properties of caprolactam/long chain lactam copolymer

The thermal properties of caprolactam/long chain lactam copolymer were studied with a Perkin-Elmer DSC 7. The melting point (T _m), heat of fusion (δH _m), crystalline degree (X _c), crystallization temperature (T _c) and glass transition temperature (T _g) of the copolymers increase with decrease of the content of the log chain lactam. From the changes in the mechanical properties with corresponding changes in the thermal properties, it is clear that the copolymers are thermal plastic and elastic. In addition, it is found that the results at a heating rate of 10 deg·min^?1 are almost the same as that at 20 deg·min^?1 after thermal history is erased.     

Thermal properties of polylactides

A thermal analysis of a series of polylactides (PLA) was carried out based on the number of average molecular mass (M _n), and the nature of isomer (D, L and DL). It is confirmed that the glass transition temperature (T _g) of PLA increased as a function of molecular mass irrespective of isomer type except sample with a high polydispersity index. The melting temperature (T _m) and enthalpy of crystal fusion (ΔH _f) of L-isomer increased as the M _n was increased from 1100 to 27500. The degree of crystallinity (χ_c%) increased as a function of molecular mass. However no crystallization peak was detected in the lower molecular mass range (550–1400). The non-isothermal crystallization behavior of the PLA melt was significantly influenced by the cooling rate. Both D and L isomers exhibited insignificant difference in thermal properties and DL lactides exhibited amorphous behavior at identical molecular masses. Change in microstructure showed significant difference between two isomers. Analysis of the FTIR spectra of these PLA samples in the range of 1200–1230 cm⁻¹ supported DSC observation on crystallinity.     

Thermal properties of poly(lactic acid)/organo-montmorillonite nanocomposites

Poly(lactic acid)/organo-montmorillonite nanocomposites were prepared by melt intercalation technique. Maleic anhydride-grafted ethylene propylene rubber (EPMgMA) was added into the PLA/OMMT in order to improve the compatibility and toughness of the nanocomposites. The samples were prepared by single screw extrusion followed by compression molding. The effect of OMMT and EPMgMA on the thermal properties of PLA was studied. The thermal properties of the PLA/OMMT nanocomposites have been investigated by using differential scanning calorimeter (DSC) and thermo-gravimetry analyzer (TG). The melting temperature (T _m), glass transition temperature (T _g), crystallization temperature (T _c), degree of crystallinity (χ_c), and thermal stability of the PLA/OMMT nanocomposites have been studied. It was found that the thermal properties of PLA were greatly influenced by the addition of OMMT and EPMgMA.     

Analysis of thermodynamic characteristics of imidazolium-based ionic liquid on coal

To investigate the effects of ionic liquids (ILs) on the oxidative combustion characteristics of coal, the oxidation characteristics of ILs on coal, such as characteristic temperature, thermal mass loss rate, and oxidation kinetics characteristic parameters, were determined. The results the [BMIm][I]-treated coal samples increased cracking temperature (T₁), maximum oxidization mass gain (T₂), ignition temperature (T₃), burnout temperature (T₄), minimum thermal rate (T_a), maximum thermal energy (T_b), and maximum thermal rate (T_c) by 33.2, 29.3, 20.7, 42.8, 11.4, 23.0, and 27.9 °C, respectively. The increase mass ratio of coal samples treated with ILs increased and decreased at the water evaporation and thermal decomposition stages, respectively. The apparent activation energy (E_a) of coal samples treated with ILs increased, and the mechanism function also changed accordingly. These showed that the ILs improved the thermal stability of the coal samples in the stages of absorbing oxygen and increased mass, and the loss of combustion. The ILs caused damage to the molecular structure of the coal and ultimately effected changes in the combustion performance. In addition, the [BMIm][BF₄] hardly weakens the inhibitory effectiveness of the coal sample over time; coal spontaneous combustion could be effectively inhibited.

     

Evaluating the Thermal Hazard of Double-Base Propellant SQ-2 by Using Microcalorimetry Method

The thermal decomposition behavior of double‐base rocket propellant SQ‐2 was studied by a Calvet microcalorimeter at four different heating rates. The kinetic and thermodynamic parameters were obtained from the analysis of the heat flow curves. The critical temperature of thermal explosion (T_b), the self acceleration decomposition temperature (T_SADT), the adiabatic decomposition temperature rise (ΔT_ad), the time‐to‐explosion of adiabatic system (t), critical temperature of hot‐spot initiation (T_cr), critical thermal explosion ambient temperature (T_acr), safety degree (SD) and thermal explosive probability (P_TE) were presented to evaluate the thermal hazard of SQ‐2.     

Investigations on the Thermal and Elastic Properties of ZnO-Incorporated Phosphate Glasses and Glass Ceramics

Abstract

Glasses of the 45P₂O₅-(40-x)CaO-15Na₂O-xZnO system with increasing zinc oxide (ZnO) concentrations within the ranges of 3 ≤ x ≤ 12 mol% were obtained by employing the melt-quench technique. ZnO inclusions in the phosphate glass network lead to increases in its density and, conversely, a decrease in its molar volume. On the basis of the obtained thermal analysis data, the glasses underwent thermal treatment, which helped to derive their glass ceramic equivalents. The evaluations of structural and elastic properties of glasses before and after thermal treatments were made using X-ray diffraction (XRD) studies and ultrasonic nondestructive testing. The differential thermal analysis data show the reduction in the crystallization tendency and increase in thermal properties, such as crystallization temperature (T _P), thermal stability

(T _c – T _g) (where T_c is crystallization onset temperature and T _g is glass transition temperature), thermal stability parameter (S), and degree of glassification (D _g) of phosphate glasses against the progressive additions of ZnO. The XRD of glass ceramics confirmed the dominance of metaphosphate, pyrophosphate, and ZnO-related crystalline features. The measured elastic moduli, such as longitudinal (L), shear (G), Young's (Y), and bulk (K), and Vicker's microhardness values increased in both glass and glass ceramics with an increase in ZnO incorporation.     

Morphology and modulus–temperature behavior of semicrystalline poly(ethylene terephthalate) (PET)

The influence of the thermal history on the morphology and mechanical behavior of PET was studied. The degree of crystallinity (density measurements) and the morphological structure (electron microscopy and small-angle x-ray diffraction) depend on the crystallization temperature. The viscoelastic parameters obtained from the modulus–temperature curves are mainly determined by the morphology of the samples. The glass-transition temperature, T_i, is a function of the crystallinity and the crystallization temperature. It is maximum for a crystallinity between 0.34 and 0.39 for a sample crystallized isothermally between 120 and 150°C. This dependence on crystallization conditions is ascribed to the conformation of the amorphous chain segments between the crystalline lamellae as well as the concentration and the molecular weight of the polymer material rejected during isothermal crystallization. Both factors are supposed to be temperature-dependent. The value of the rubbery modulus is a function of both the volume concentration of the crystalline lamellae and the structure of the interlamellar amorphous regions (chain folds, tie molecules, chain ends, and segregated low molecular weight material). Annealing above the crystallization temperature of isothermally crystallized samples has a marked influence on their morphology and mechanical behavior. The morphological structure and the viscoelastic properties of annealed PET samples are completely different from those obtained with samples isothermally crystallized at the same temperature.     

Synthesis and characterization of poly(L‐lactic acid)–poly(ε‐caprolactone) multiblock copolymers by melt polycondensation

An Erratum has been published for this article in J. Polym. Sci. Part A: Polym. Chem. (2004) 42(22) 5845 New multiblock copolymers derived from poly(L‐lactic acid) (PLLA) and poly(ε‐caprolactone) (PCL) were prepared with the coupling reaction between PLLA and PCL oligomers with ? NCO terminals. Fourier transform infrared (FTIR), ¹³C NMR, and differential scanning calorimetry (DSC) were used to characterize the copolymers and the results showed that PLLA and PCL were coupled by the reaction between ? NCO groups at the end of the PCL and ? OH (or ? COOH) groups at the end of the PLLA. DSC data indicated that the different compositions of PLLA and PCL had an influence on the thermal and crystallization properties including the glass‐transition temperature (T_g), melting temperature (T_M), crystallizing temperature (T_c), melting enthalpy (ΔH_m), crystallizing enthalpy (ΔH_c), and crystallinity. Gel permeation chromatography (GPC) was employed to study the effect of the composition of PLLA and PCL and reaction time on the molecular weight and the molecular weight distribution of the copolymers. The weight‐average molecular weight of PLLA–PCL multiblock copolymers was up to 180,000 at a composition of 60% PLLA and 40% PCL, whereas that of the homopolymer of PLLA was only 14,000. A polarized optical microscope was used to observe the crystalline morphology of copolymers; the results showed that all polymers exhibited a spherulitic morphology. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5045–5053, 2004     

Kinetics of crystallization of Zr52Cu18Ni14Al10Ti6 metallic glass

Metallic glasses have received considerable attention in comparison to normal metallic materials due to their superior physical and mechanical properties. These systems possess large under cooled region, ∆T (∆T = T _x − T _g where, T _x is crystallization temperature and T _g is glass transition temperature) and hence increased thermal stability against crystallization. Due to this, the study of their crystallization kinetics is important and interesting. It is interesting because of the fact that, crystallization becomes multi-step process due to several components present in these systems. In this paper, we report the experimental investigations of crystallization of Zr₅₂Cu₁₈Ni₁₄Al₁₀Ti₆ glassy alloy system, which is among the best non-beryllium containing glasses, using differential scanning calorimetry (DSC). The crystallization, as expected, consists of multiple steps. Interestingly, the peak heights of these steps vary with heating rate. At lower heating rates, first peak is most prominent and subsequently diminishes with increase in heating rate with last peak prominence visible at highest heating rate. Both, iso-kinetic and iso-conversional methods of analysis of kinetics of crystallization have been used to evaluate the activation energy and Avrami exponents and consistent results are obtained.     

Influence of stereochemistry on the thermal properties of partially cycloaliphatic polyamides

The effects of the partial substitution of 1,4‐disubstituted cyclohexane monomers for linear aliphatic monomers in polyamides are discussed. More specifically, the relation between the stereochemistry of the cycloaliphatic residues and the thermal properties [melting temperature (T_m) and crystallization temperature (T_cr)] was investigated. For this purpose, two different types of copolyamides were synthesized: in polyamides 12.6, the adipic acid residues were partially replaced by cis/trans‐1,4‐cyclohexanedicarboxylic acid (1,4‐CHDA), whereas in polyamides 4.14, the 1,4‐diaminobutane residues were partially substituted with cis/trans‐1,4‐diaminocyclohexane (1,4‐DACH). For both systems, increasing the degree of substitution of cycloaliphatic residues for linear aliphatic residues resulted in a rise of both T_m and T_cr. This points to the isomorphous crystallization of the linear and cycloaliphatic residues. In contrast to the use of 1,4‐DACH as a comonomer, 1,4‐CHDA residues showed isomerization upon thermal treatment of the polyamides. This isomerization of the cyclohexane residues influenced the thermal properties of the copolyamides. The use of a nonisomerizing cis–trans mixture of 1,4‐DACH exhibited the large influence of the stereochemistry of the cycloaliphatic residues on the T_m of the copolyamides. For both the 1,4‐CHDA‐ and 1,4‐DACH‐based copolyamides, differential scanning calorimetry analysis revealed that recrystallization occurs during melting. This exothermal effect becomes less pronounced with an increasing content of rigid cycloaliphatic residues. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1962–1971, 2002     

Segmented polyethylene oxides: A new class of polyethers prepared via melt transetherification

Several segmented polyethylene oxides (SPEOs) were prepared by a melt-transetherification process using 1,4-bis(methoxymethyl)-2,3,5,6-tetramethylbenzene and polyethylene glycols (PEGs) of different molecular weights (di-, tri-, and tetraethylene glycols and PEGs of molecular weights 300, 600, 1000, 1500, and 3400) as the monomers. The effect of polymerization temperature (185 and 150 °C) on the molecular weight of SPEOs was studied, and it was shown that the molecular weight is larger at a higher polymerization temperature. The reversal of the polycondensation (transetherification) equilibrium by treatment of the polyethers with excess methanol transformed them completely into the starting monomers. The analysis of the degraded products by mass and NMR spectroscopies revealed that side reactions, such as the self-condensation of diols, are insignificant. The polymers containing shorter PEG spacers are amorphous, whereas the ones with longer PEG spacers are semicrystalline. The glass-transition temperature (T_g) of the SPEOs decreased with increases in the spacer length and attained the value of PEO at PEG-600, whereas the melting transition (T_m), crystallization temperature (T_c), and their enthalpies of transition, (ΔH_m) and (ΔH_c), increased with increases in the spacer length. The introduction of “molecular kinks” into SPEOs by the use of another monomer, 1,3-bis(methoxymethyl)-2,4,5,6-tetramethylbenzene, surprisingly, showed little effect on their thermal properties. A “branched-PEO” analogue, containing pendant oligoethyleneoxy units, was also prepared, and its thermal properties were compared with its linear analogue. Preliminary ionic conductance measurements showed that some of these SPEOs could serve as potential candidates for solid polymer–electrolyte applications. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1615–1628, 2001     

Ultraviolet‐induced crosslinking of poly(butylene succinate) and its thermal property,dynamic mechanical property,and biodegradability

Crosslinking is an effective way to improve polymer properties. This paper focuses on ultraviolet‐induced crosslinking of poly(butylene succinate) (PBS) in the presence of a photoinitiator and a crosslinking agent at ambient temperature. The effects of the concentration of photoinitiator, the crosslinking agent content, and the irradiation time on the crosslink behavior were investigated. To obtain an appropriate gel fraction in different irradiation times, 3.0 wt% of photoinitiator and 10.0 wt% of crosslinking agent were proved to be the optimum choice. Furthermore, properties such as thermal properties, dynamic mechanical property, and enzymatic degradation of PBS before and after crosslinking were examined. Differential scanning calorimetry (DSC) analysis revealed that glass transition temperature (T_g) increased with increase in gel fraction, while melting temperature (T_m) and the degree of crystallinity decreased. This may be caused by the reduced molecular chain mobility and inhibited molecular motion for crystallization in crosslinked samples. The crosslinked polymer also showed improved thermal stability and dynamic mechanical property. In addition, the introduction of crosslinking retarded the enzymatic degradation rate of PBS, but it was still biodegradable. The improved properties of crosslinked PBS will extend the application of PBS. Copyright © 2009 John Wiley & Sons, Ltd.     

Thermal Behavior and Non-isothermal Decomposition Reaction Kinetics of NEPE Propellant with Ammonium Dinitramide

Thermal decomposition behavior and non‐isothermal decomposition reaction kinetics of nitrate ester plasticized polyether NEPE propellant containing ammonium dinitramide (ADN), which is one of the most important high energetic materials, were investigated by DSC, TG and DTG at 0.1 MPa. The results show that there are four exothermic peaks on DTG curves and four mass loss stages on TG curves at a heating rate of 2.5 K·min^?1 under 0.1 MPa, and nitric ester evaporates and decomposes in the first stage, ADN decomposes in the second stage, nitrocellulose and cyclotrimethylenetrinitramine (RDX) decompose in the third stage, and ammonium perchlorate decomposes in the fourth stage. It was also found that the thermal decomposition processes of the NEPE propellant with ADN mainly have two mass loss stages with an increase in the heating rate, that is the result of the decomposition heats of the first two processes overlap each other and the mass content of ammonium perchlorate is very little which is not displayed in the fourth stage at the heating rate of 5, 10, and 20 K·min^?1 probably. It was to be found that the exothermal peak temperatures increased with an increase in the heating rate. The reaction mechanism was random nucleation and then growth, and the process can be classified as chemical reaction. The kinetic equations of the main exothermal decomposition reaction can be expressed as: dα/dt=10^12.77(3/2)(1?α)[?ln(1?α)]^1/3 e^{?1.723×104/T}. The critical temperatures of the thermal explosion (T_be and T_bp) obtained from the onset temperature (T_e) and the peak temperature (T_p) on the condition of β→0 are 461.41 and 458.02 K, respectively. Activation entropy (ΔS^≠), activation enthalpy (ΔH^≠), and Gibbs free energy (ΔG^≠) of the decomposition reaction are ?7.02 J·mol^?1·K^?1, 126.19 kJ·mol^?1, and 129.31 kJ·mol^?1, respectively.     

Preparation and properties of silicon containing copolyamides

Copolyamides containing siloxane moieties in main chain were prepared by a melt polycondensation with 1,3-bis(3-aminopropyl)tetramethyldisiloxane (E), hexamethylenediamine (N6), and adipic acid (6). Glass transition temperature (T_g), cold crystallization temperature (T_cc), and melting temperature (T_m) were measured by differential thermal analysis (DTA). The depression of T_m for copolyamide was fitted by the Flory curve. Melting peak remarkably broadens with increasing E6 component in copolyamide. The change of T_g was fitted by the Gibbs and Dimarzio's equation in which the number of flexible bond is considered. The difference between T_g and T_cc increased with increasing E6 component. These DTA studies suggest that the crystallization of N66 component in copolyamide is hindered by the bulky siloxane moiety, while the micro-Brownian motion of amorphous segment is promoted by the flexible siloxane bond. Tensile strength and Young's modulus decreased with increasing E6 component. The solubility in various solvents increased with increasing E6 component. Permeability of oxygen and nitrogen increased with an increase of temperature and E6 component. The separation coefficient of oxygen to nitrogen rapidly increased near 50 mol% of E6 concentration and then leveled out above 70 mol%. The contact angle with water and methylene iodide increased with an introduction of the siloxane moiety into polymer chain.     

Thermal stability and crystallization kinetics in superionic glasses using electrical conductivity–temperature cycles

The present work demonstrates application of electrical conductivity (σ)–temperature (T) cycles to investigate thermal properties viz., crystallization and glass transition kinetics in AgI–Ag₂O–V₂O₅–MoO₃ superionic glasses. The σ–T cycles are carefully performed at various heating rates, viz., 0.5, 1, 3, 5, and 7 K/min. The conductivity in Ag⁺ ion conducting glasses exhibit anomalous deviation from Arrhenius behavior near glass transition temperature (T _g) followed by a drastic fall at crystallization (T _c). The temperature corresponding to maximum rate of crystallization (T _p) is obtained from the derivative of σ–1/T plots. With increasing heating rates, the characteristic temperatures (T _g, T _p) are found to be shifting monotonically toward higher temperatures. Thus, activation energy of structural relaxation E _s, crystallization E _c and other thermal stability parameters have been obtained from σ–T cycles using Kissinger equation and Moynihan formulation. For a comparative study, these kinetics parameters have also been calculated from differential scanning calorimetry plots. The parameters obtained from both the methods are found to be comparable within experimental error.     

New insights into the multiple melting behaviors of the semicrystalline ethylene‐hexene copolymer: Origins of quintuple melting peaks

A semicrystalline ethylene‐hexene copolymer (PEH) was subjected to a simple thermal treatment procedure as follows: the sample was isothermally crystallized at a certain isothermal crystallization temperature from melt, and then was quenched in liquid nitrogen. Quintuple melting peaks could be observed in heating scan of the sample by using differential scanning calorimeter (DSC). Particularly, an intriguing endothermic peak (termed as Peak 0) was found to locate at about 45 °C. The multiple melting behaviors for this semicrystalline ethylene‐hexene copolymer were investigated in details by using DSC. Wide‐angle X‐ray diffraction (WAXD) technique was applied to examine the crystal forms to provide complementary information for interpreting the multiple melting behaviors. Convincing results indicated that Peak 0 was due to the melting of crystals formed at room temperature from the much highly branched ethylene sequences. Direct heating scans from isothermal crystallization temperature (T_c, 104–118 °C) were examined for comparison, which indicated that the multiple melting behaviors depended on isothermal crystallization temperature and time. A triple melting behavior could be observed after a relatively short isothermal crystallization time at a low T_c (104–112 °C), which could be attributed to a combination of melting of two coexistent lamellar stack populations with different lamellar thicknesses and the melting‐recrystallization‐remelting (mrr) event. A dual melting behavior could be observed for isothermal crystallization with both a long enough time at a low T_c and a short or long time at an intermediate T_c (114 °C), which was ascribed to two different crystal populations. At a high T_c (116–118 °C), crystallizable ethylene sequences were so few that only one single broad melting peak could be observed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2100–2115, 2008     

Thermal properties of freezing bound water restrained by sodium lignosulfonate-based polyurethane hydrogels

In order to develop a new functional product from lignin, sodium lignosulfonate (LS)-based polyurethane (LSPU) hydrogels were prepared from LS and hexamethylene diisocyanate (HDI) derivatives in water. Isocyanate/hydroxyl group ratio (NCO/OH ratio) was varied from 0.05 to 0.8 mol mol⁻¹, and water content (W_c = mass of water/mass of dry sample) of the obtained LSPU hydrogels was varied from 0 to 3.0 g g⁻¹. Phase transition behavior of hydrogels with various W_c’s was investigated by differential scanning calorimetry (DSC) and thermogravimetry (TG). In DSC heating curve of LSPU hydrogels, glass transition, cold crystallization, melting and liquid crystallization were observed. Cold crystallization, two melting peaks and variation of melting enthalpy indicate that three kinds of water, i.e., non-freezing water, freezing bound water and free water, exist in LSPU hydrogel. Glass transition temperature (T_g) decreased from 230 to 190 K in a W_c range where non-freezing water was formed in the hydrogel. T_g increased when freezing bound water was formed in the system. T_g leveled off in a W_c range where normal ice was formed. The effect of NCO/OH ratio on molecular motion of LSPU hydrogel is examined based on T_g and heat capacity difference at T_g (ΔC_p). Water vaporization curve measured by TG also indicates the presence of bound water which evaporates at a temperature higher than ca. 410 K. By atomic force microscopic observation, the size of molecular bundle of LSPU hydrogel is calculated and compared with that of LS-water system. By cross-linking, the height of molecular bundle decreased from ca. 3–1 nm and lignin molecules extend in a flat structure.

     

Thermal properties of polyurethanes derived from molasses before and after biodegradation

Polyurethane (PU) foams derived from molasses were placed in soil for various periods from 3 to 12 months. Thermal properties of PU's before and after biodegradation were investigated by differential scanning calorimetry (DSC) and thermogravimetry (TG). Glass transition of PU's after 3 month's degradation was separated into two stages indicating that molecular chains of the original and decomposed portions move independently. Based on variation of glass transition temperature (T_g), heat capacity difference at T_g (δC_p), thermal degradation temperature and mass loss, the degradation mechanism of PU was established.     

The effect of ions irradiation on the thermal properties of poly(ether ether ketone)

The effect of irradiating amorphous poly (ether ether ketone), PEEK, with ions, 11 MeV proton (H⁺), and 25.6 MeV helium (He²⁺), has been investigated focusing on the changes in thermal properties. The extent of chain scission and crosslinking was evaluated using the Charlesby‐Pinner equation. Crosslinking increased the glass transition temperature (T_g) in line with the DiBenedetto equation from which the crosslinking constant for each ion was calculated. The effect of irradiation on the thermal degradation kinetics was studied in an argon atmosphere at a constant heating rate by mean of the Chang and the second Kissinger methods. Irradiation significantly reduced the thermal stability of the polymer and its service lifetime. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2212–2221, 2008     

CRYSTALLIZATION AND MULTI-MELTING BEHAVIOR OF POLY (ETHYLENE TEREPHTHALATE) MODIFIED BY SODIUM SALT OF 5-SULPHO-ISOPHTHALIC ACID

The crystallization kinetics of the copolyester, poly(ethylene terephthalate) (PET) modified by sodium salt of 5-sulpho-isophthalic acid(SIPM), was investigated by means of differential scanning calorimeter. The experimental results and polari-microscopy observation all showed that the introduction of SIPM did not affect the nucleation of crystallization. Within the temperature range between their glass transition temperature T_θand melting point T_m, the crystallization rate of the copolyester sample decreased with increasing content of SIPM. The relative crystallization rate constant Z of SIPM/DMT (dimethyl terephthalate) 4mol % sample was about 1% pure PET's Z value. For isothermal crystallized copolyester samples, DSC heating curves displayed multi-melting behavior. This was interpreted by molecular weight fractionation during crystallization and premelting-recrystallization mechanism. This interpretation showed why the second melting point T_(m2) will change according to Hoffman-Weeks(H-W) equation and the first melting point T_(m1) will increase with increasing SIPM. The principal cause of these phenomena is the high temperature crystallization rate decreases rapidly with increasing SIPM.