Greater Heat Resistance Research Articles

Heat resistance differences are common between both vegetative cells and spores of Clostridium perfringens type F isolates carrying a chromosomal vs plasmid-borne enterotoxin gene.

Clostridium perfringens type F isolates utilize C. perfringens enterotoxin (CPE) to cause food poisoning (FP) and nonfoodborne gastrointestinal diseases. The enterotoxin gene (cpe) can be located on either the chromosome or plasmids, but most FP isolates carry a chromosomal cpe (c-cpe) gene. Our 2000 article in Applied and Environmental Microbiology (66:3234-3240, 2000, https://doi.org/10.1128/aem.66.8.3234-3240.2000https://doi.org/10.1128/AEM.66.8.3234-3240.2000) determined that vegetative cells and spores of c-cpe isolates are more heat resistant than those of plasmid cpe (p-cpe) isolates, which is favorable for their survival in improperly cooked or held food. However, that 2000 article was recently retracted (90:e00249-24, 2024, https://doi.org/10.1128/aem.00249-24). To our knowledge, the 2000 article remains the only study reporting that heat resistance differences are common between both vegetative cells and spores of type F c-cpe isolates vs type F p-cpe isolates. To confirm and preserve this information in the literature, the heat resistance portion of the 2000 study has been repeated. The 2024 results reproduced the 2000 results by indicating that, relative to the surveyed type F p-cpe isolates, the vegetative cells of surveyed type F c-cpe isolates are ~2-fold more heat resistant and the spores of most surveyed c-cpe isolates are ~30-fold more heat resistant. However, consistent with several reports since our 2000 paper, one surveyed type F c-cpe isolate (which did not appreciably sporulate in 2000 but sporulated in 2024) produced spores with intermediate heat sensitivity, confirming that spores of some type F c-cpe isolates lack exceptional heat resistance.IMPORTANCEClostridium perfringens type F food poisoning (FP), which is the second most common bacterial cause of FP, involves the production of C. perfringens enterotoxin. While the enterotoxin gene (cpe) can be located on either the chromosome or plasmids in type F isolates, most FP cases are caused by chromosomal cpe isolates. The current results support the conclusion that the vegetative cells and spores of type F chromosomal cpe isolates are often more heat resistant than vegetative cells and spores of type F plasmid cpe isolates. Greater heat resistance should favor the survival of the spores and vegetative cells of those chromosomal cpe isolates in temperature-abused food, which may help explain the strong association of type F chromosomal cpe strains with FP.

Polysilazane hybrid phenolic resin ceramic aerogels with excellent electromagnetic wave absorption performance

AbstractAlthough various aerogels with electromagnetic wave (EMW) absorbing properties have been extensively explored, the development of aerogels with excellent wave absorption performance, low density, and great heat resistance has still met profound challenges. Herein, polysilazane hybrid phenolic resin aerogels (PRVS aerogels) were prepared using the vinyl addition reaction of polysilazane and cross‐linking reaction between polysilazane and phenolic resin. A SiOCN ceramic aerogel with multistage pore structure was prepared via a simple and quick freeze‐drying method and polymer‐derived ceramic (PDC) methods. The SiOCN ceramic aerogels exhibited low density (0.15–0.27 g/cm3), good heat‐shielding (thermal conductivity in the range of 0.03–0.04 W/(m·K)), and excellent wave absorption performance (i.e., RL was about –31.6 dB@16.48 GHz and EAB was 3.85 GHz when the thickness of the ceramic aerogel was 1.2 mm). Hence, the ceramic aerogel absorbing materials could meet the requirements of “wide absorption bandwidth, strong reflection loss, lightweight and thi thickness”. Moreover, the mechanism of low weight, heat insulation, and wave absorption properties of the aerogels were also investigated. We believe this work is of great significance in ceramic aerogels prepared by traditional polymers, which may provide new opportunities for new ceramic aerogels with applications ranging from EMW absorption to aerospace and information technology.

Effect of alumina content on the thermal, mechanical and tribological properties of resin‐based friction materials

AbstractTo investigate the effect of alumina on the thermal, mechanical, and tribological properties of resin‐based friction materials, five friction materials with different alumina contents were prepared by the hot press molding process. The experimental results showed denser friction materials possessed higher hardness, while compressive strength and compression modulus dropped as alumina decreased. Friction material with 6 wt% alumina exhibited outstanding impact strength and great heat resistance. It also showed excellent friction stability, with a maximum mean coefficient of friction (COF) steady between 0.408 and 0.425 at various braking speeds. The wear resistance of friction materials had a positive relationship with the stability of the COF, and the greater the stability of the COF, the better the wear resistance and the lower the corresponding wear rate. The morphology of the worn surface indicated multiple sources of friction at different braking speeds, and large areas of dense friction films were beneficial to stabilizing the COF and reducing the wear rate.Highlights The sample with 6 wt% alumina showed excellent heat resistance, with a residual value of 83.5% at 800°C. The highest compressive strength and compression modulus were achieved in the sample with 8 wt% alumina. The sample containing 6 wt% alumina exhibited the highest COF and the lowest wear rate. The maximum subsurface temperature of the friction materials basically rose as braking speed increased. Large areas of dense friction films were beneficial to stabilizing the COF and reducing the wear rate.

Development of Photosensitive Hydrogel-based 3-dimensional Bioprinting Using Locally Extracted Pectin From Durian Rind Waste and Cellulose for Pharmaceutical Application

Introduction: Hydrogels have gained prominence in a variety of fourth industrial revolution applications, including three-dimensional (3D) printing. However, there are limitations to 3D manufacturing, such as deformities in the final product. This is a significant obstacle to adopting this technology in the pharmaceutical industry, as printed products may have insufficient mechanical properties and a high brittleness, making further processing of these dosage forms problematic. The objective of this study is to produce a new 3D bioink from a mixture of locally produced pectin-based material from durian rind waste and cellulose-based material (pectin/cellulose hydrogel) and to partially characterize the bioink hydrogel. Methods: Four formulations of pectin/cellulose-based hydrogel (3:1, 3:2, 4:1, and 5:3 ratio of pectin/cellulose) from durian rind waste and carboxymethyl cellulose (CMC) powder, as well as cross-linking agents, were developed and evaluated using a rheometer to evaluate viscoelastic properties, FTIR Spectroscopy to identify compounds, and thermogravimetric analysis (TGA) to evaluate thermal stability. Results: All bioink formulations exhibit outstanding shear-thinning behavior suitable for 3D printing. The viscosity of edible ink increases as the pectin/cellulose concentration increases. The formulation of 3:1 pectin/cellulose has greater heat resistance than others (highest thermal stability with 21.69% of residual weight) and the lowest percentage of weight loss (76.18%). Conclusion: The study of a pectin/cellulose hydrogel mixture provides an attractive outcome for the creation of bioink due to the effective synthesis of 3D printing shapes that are both smooth and uniform.

Transparent, Heat-Resistant, Ductile, and Self-Reinforced Polylactide through Simultaneous Formation of Nanocrystals and an Oriented Amorphous Phase

Imparting polylactide (PLA) films with great heat resistance, transparency, and balanced mechanical performance simultaneous is a big challenge in academia and industry due to mutual exclusiveness of properties. In this work, a newfound strategy that combines elongational stress field and thermal field is proposed to reorganize the crystalline and amorphous structure of PLA films. It is discovered that the oriented PLA films with high draw ratios form a unique structure of the oriented amorphous phase restricted by the oriented nanosized crystal during thermal treatment at an appropriate temperature. Superb stiffness–toughness balance of the film is achieved as the elongation at break increases from 16 to 91.9% after the thermal treatment at 150 °C, while the yield strength increases from 50.0 to 76.0 MPa. It is worth noting that the PLA film also has excellent transparency, i.e., a transmittance as high as 86.6% (550 nm), owing to crystallites formed on the nanometer scale. Excellent heat resistance is also obtained, with the onset decline temperature increasing from 63.7 (for the unstructured casting film) to 77.1 °C due to increased crystallinity. Furthermore, a new understanding of the orientation of the amorphous phase promoted by the confinement effect to the toughening of PLA is obtained, and a phenomenal model for the thermal-treatment-induced toughening effect is proposed. This work could provide a significant guidance for the facile preparation of a PLA film with promising comprehensive properties of toughness–stiffness balance, high transparency, and good heat resistance.

Fast curing phthalonitrile modified novolac resin: Synthesis, curing study and preparation of carbon and glass fibric composites

Phthalonitrile modified novolac (PNN) was synthesized in aim to develop a fast-curing resin for hot-pressing processing and characterized by NMR to confirm a full substitution of hydroxyl groups with phthalonitrile. PNN blended with high amounts (10–50 wt%) of the amine curing agents have been investigated by DSC, FT-IR spectroscopy and TGA, which revealed T5% = 420 °C. Curing times for the compositions were 4–16 min at 240 °C. The 50 min post-curing cycle for FRPs was selected based on DMA. Composites were fabricated via hot-pressing of prepregs including post-curing at 280 °C (providing Tg > 340 °C) in total of 60 min, which is the fastest curing cycle for thermosetting resins developed for applications up to 300 °C. Carbon and glass fabric reinforced polymers (CFRP and GFRP) were obtained by the developed program yielding integral composites with high mechanical properties and great heat resistance. Interlaminar shear strengths of the CFRP were up to 31 MPa and up to 70 MPa for GFRP. The latter which demonstrated retention of 75% of initial ILLS values after dwelling for 200 h at 300 °C. Thus, a new fast-processing phthalonitrile resin was developed for application in electric transport, aerospace and heat-resistant insulation.

Enhanced mechanical properties of bridged graphene oxide/bismaleimide nanocomposites

AbstractAs the primary matrix resin for advanced composites, bismaleimide (BMI) is highly demand in the aerospace field, but its development is limited due to the brittleness of the cured resin. Graphene oxide (GO) is often used as a toughening filler for thermosetting resins due to the special structure, but the dispersion and interface interaction with the matrix have been puzzling. To improve toughening effect of GO in BMI, we proposed a strategy to selectively functionalize the surface of GO. In our work, GO was functionalized by maleic anhydride (MAH) and BMI resin (QY8911‐IV) was selected as the matrix of the nanocomposite. A series of characterizations demonstrated that MAH has been bonded to the surface of GO and modified GO still maintained a nanoscale dimension. Moreover, the short‐chain of MAH can provide a bridging effect. The impact strength of MAH‐GO/QY8911‐IV nanocomposite was 29.06 kJ/m2 at 0.05 wt% loading of MAH‐GO, which was 93.2% higher than that of neat QY8911‐IV. Morphology analysis revealed that the fracture behavior of MAH‐GO modified nanocomposites changed from brittle to ductile. Meanwhile, the nanocomposite showed great heat resistance and thermal stability, so it could be expected to be popularized in high‐load and high‐temperature working environments.

Improvement of Surface Coating and Interfacial Properties of Hot-Waxed Wood Using Maleic Anhydride Grafted Polypropylene Wax

Beeswax is used on wood furniture surfaces in China. Beeswax is expensive and has a low melting temperature, and the wax film is easily softened and destroyed. To overcome these problems, a modified polypropylene wax grafted with maleic anhydride, with a high melting temperature and low price, was used in hot-waxed wood. The adhesion, hardness, hydrophobic properties, heat resistance, color, and gloss of hot-waxed woods were also examined. The surface and interfacial properties were characterized by FTIR, XRD, and SEM. The modified polypropylene wax showed a higher melting temperature than beeswax by DSC, and the heat resistance of hot-waxed wood using it was revealed by TG. The adhesion for the modified polypropylene wax hot-waxed wood surface was shown to achieve grade 1. In addition, it maintained original grades in adhesion after soaking in water and was greater than beeswax hot-waxed wood. The hot-waxed wood surfaces become hydrophobic compared with untreated wood, and the hydrophobicity of the modified polypropylene wax hot-waxed wood surfaces, with a decreased water contact angle, were slightly weaker than beeswax hot-waxed wood and polypropylene wax hot-waxed wood. Moreover, in hardness, the modified polypropylene wax hot-waxed wood surfaces (2H) were harder than beeswax hot-waxed wood (3B), representing stronger scratch resistance and performing well in decorative characteristics, such as color and gloss. The results of SEM, FTIR, and XRD showed mechanical and weak chemical bonding between the waxes and the surface of the wood with the presence of wax in a wood structure. Therefore, the modified polypropylene wax could be used in hot-waxed wood with great heat resistance, adhesion, and surface performance. The study is beneficial for the application of wood coatings using synthetic wax in the future.

Organic/inorganic double-precursor cross-linked alumina aerogel with high specific surface area and high-temperature resistance

Alumina aerogel has drawn a great research interest in the aerogel community owing to its great high-temperature heat resistance. The typical preparation can be divided into two approaches depending on the type of precursors. However, the alumina aerogel derived from organic aluminum alkoxides suffers from poor monolithic integrity, whereas the one from inorganic aluminum salts presents unsatisfied thermal stability. In this work, we develop a novel organic/inorganic double-precursor cross-linking method to prepare alumina aerogels. Aluminum chloride hexahydrate is used to provide an acid condition for the hydrolysis and condensation reaction of aluminum sec-butoxide (ASB), and serves as a reactant to co-condensate with the hydrolyzed ASB to form an interpenetrating chain structure. The resulting alumina aerogel exhibits a high specific surface area (SSA) of 667 m2/g and good high-temperature thermal insulation performance. Moreover, it can still retain SSA of 224 and 105 m2/g after heating at 1000 and 1300°C, respectively.

Bio‐resourced eugenol derived phthalonitrile resin for high temperature composite

AbstractEugenol (EG) is an abundant renewable compound that has been widely used in the synthesis of bio‐based thermosetting resin, but there are few reports on the phthalonitrile (PN) resin derived from EG. In this study, a new kind of bio‐based PN resin (MEG‐PN) derived from EG derivative was successfully synthesized. PN is a traditional class of high‐performance thermosets with poor processability for its ultra‐high melting point and curing temperature. The MEG‐PN resin possesses excellent processability: its melting temperature is much lower (77°C), and it can be cured at a moderate temperature (281°C) in the absence of curing agents. The cured MEG‐PN resin exhibited great heat resistance according to its 5% weight loss temperature at 448°C and its char yield percentage as high as 75.6% at 800°C under nitrogen. The properties of the carbon‐fiber reinforced MEG‐PN composite were comparable to those of petroleum‐based PN resins: the glass transition temperature was around 397°C; the flexural strength and modulus were as high as 756 MPa and 119 GPa, respectively. Overall, a bio‐based PN thermoset with great comprehensive performance was synthesized possessing the potential in the application of advanced composite.

Highly Toughened and Heat-Resistant Poly(lactic acid) with Balanced Strength Using an Unsaturated Liquid Crystalline Polyester via Dynamic Vulcanization

Poly(lactic acid) (PLA) is a well-known sustainable plastic but with an inherent brittleness, slow crystallization rate, and poor heat resistance, which significantly limits its application. In this work, toughened PLA with a balanced tensile strength, fast crystallization rate, and great heat resistance was obtained by dynamic vulcanization with an unsaturated liquid crystalline polyester (PBDPSM) in the presence of a free radical initiator of dicumyl peroxide (DCP). PBDPSM is efficient in enhancing the tensile toughness of PLA in that the elongation at break of PLA significantly increased from 15 to 179% while adding only 1 wt % PBDPSM. When adding 8 wt % PBDPSM, the PLA/PBDPSM8 blend has an elongation at break of 265%, tensile toughness of 107.2 MJ/m3, and notched Izod impact strength of 22.5 kJ/m2. Moreover, it keeps a high tensile strength of 62.6 MPa. In addition, the crystallization rate of PLA has dramatically accelerated due to the apparent nucleation effect induced by DCP and PBDPSM. PLA/PBDPSM3 shows the highest crystallinity with 44.4%. Furthermore, it shows a high Vicat softening temperature of 152.2 °C, which is 92.2 °C higher than that of neat PLA. Finally, highly toughened PLA materials with balanced tensile strength and good heat-resistant properties were realized.

Increase in the heat resistance of carbon steels by thermodiffusion treatment and vacuum coating application

Inthisarticleissubstantiatedthehypothesisof the possibility of increasing the heat resistance of hypoeutectoid carbon steels by preliminary thermal diffusion alloying followed by the application of vacuum nitride coatings. It was established that thermal diffusion layers obtained as a result of saturation with boron and aluminum have the greatest heat resistance in terms of relative mass gain, then in order of decreasing heat resistance: layers obtained as a result of saturation with boron and silicon, boron and chromium, boron and nitrogen, and as a result of boriding. New composite coatings of heat-resistant compositions “thermodiffusion layer – vacuum ion-plasma coating” have been developed, which are also solid, wear-resistant, and corrosion-resistant under atmospheric corrosion, solutions of salts and certain acids. The influence of ionic-plasma coatings on additional increase in heat resistance of steels with the produced thermodiffusion layers, during which the most efficient compositions of the developed coatings are defined and given to improve the temperature resistance of the surface, was assessed. The results of the calculation of the predicted heat resistance of the developed compositions “diffusion layer – ion-plasma coating” on hypoeutectoid carbon steels are given in the article.

Application of a Zwitterionic Hydrophobic Associating Polymer with High Salt and Heat Tolerance in Brine-Based Fracturing Fluid.

ZID16PM, a zwitterionic hydrophobic associating polymer, has equivalent positive and negative charges and some hydrophobic monomers with twin-tailed long hydrophobic chains. It exhibits a great heat resistance and salt tolerance to the common salt in formation brine (MgCl2, CaCl2, NaCl, and KCl), which is attributed to its anti-polyelectrolyte effect and strong association force. High-salinity water (seawater or formation water) can be prepared as a fracturing fluid directly. In this paper, the formation water of the West Sichuan Gas Field is directly prepared into fracturing fluid with a concentration of 0.3% ZID16PM (Fluid-1), and the seawater of the Gulf of Mexico is directly prepared into fracturing fluid with a concentration of 0.3% ZID16PM (Fluid-2). Finally, rheological measurements, proppant suspension tests, and core matrix permeability damage rate tests for the Fluid-1 and Fluid-2 are conducted. Results show that after 120 min of shearing at 140 and 160 °C, respectively, the viscosity of Fluid-1 remains in the range of 50–85 mPa·s, and the viscosity of Fluid-2 remains in the range of 60–95 mPa·s. And the wastewater produced by an oilfield in Shaanxi, Xinjiang, and Jiangsu are also prepared into fracturing fluids with a concentration of 0.3% ZID16PM, the viscosity of these fracturing fluids can remain 32, 42, and 45 mPa·s, respectively, after 120 min of shearing at 160 °C. All results demonstrate that the polymer ZID16PM displays prominent performance in fracturing fluids.

Effect of natural zeolite as substrate filler on the properties of NBR/EPDM blend

The NBR/EPDM blend has a great ozone, oil, and heat resistance. Carbon black is the most commonly used filler material for rubber goods. But, it is less environmentally friendly and less healthy friendly. In this study, we will study the use of natural zeolite as a substitute for the filler. This blend was carried out by a two-roll mill and tested by rheometer and tensile strength tester. From the research that has been done, it is known that vulcanizate with carbon black is better than all of the vulcanizate using zeolite as filler substitute. Vulcanizate with CB provide the fastest curing time, the fastest reaction speed and also the best mechanical properties. Vulcanization with the 10 phr zeolite gives the optimum curing time and the best mechanical properties compared to the substitution of other fillers. This shows that 10 phr zeolite (16.7%) can be a suitable filling material for NBR/EPDM blend.

Improved adhesion, heat resistance, anticorrosion properties of epoxy resins/POSS/methyl phenyl silicone coatings

A series of coatings composed of hydroxyl-terminated methyl phenyl silicone rubber (PSi) and silanized epoxy resins (SERs) were prepared in a facile way. Four kinds of SERs with different structures and degree of functionality were synthesized successfully and used to modify the silicone coating. The obtained room temperature vulcanized (RTV) silicone coatings showed excellent adhesion, great heat resistance and anticorrosion properties. Compared with pure PSi, the coatings containing 25 wt% SERs showed better thermal properties, manifested as delayed degradation temperature and greatly increased char yield at 800℃. The adhesion of coatings all reached the highest level (degree 0) which exceeded that of pure PSi coating (degree 2). Furthermore, the anticorrosion property of the coatings in 5 wt% acid, alkaline, and saline environments was all improved. The incorporation of SERs improved the compatibility between the silicone rubber and epoxy resins, in which the epoxy group created more adhesion of cured blended coating and POSS led a significant enhancement in thermal and anticorrosive properties. Their combined effect endowed silicone coatings with more application prospects.

Functionalization of Recycled Diatomite for Green, Stable, and High-performance Phase Change Material (PCM) Composite

This study reports on the functionalization of recycled diatomite (DT) for preparing green and shape-stabilized phase change material (SSPCM); the DT-based SSPCM can be employed in HDPE composite for high latent heat and good thermal conductivity. After purification, the purified DT (P-DT) adsorbed polyethylene glycol (PEG) by the straight dipping process for producing SSPCM. P-DT showed high surface area of 58 m2g-1 and low organic impurity (<1%); the PEG/P-DT SSPCM exhibited high latent heat of 45 Jg-1 and low leakage (<0.3%). By adding PEG/P-DT SSPCM into the HDPE, the SSPCM/HDPE composite improved both the heat deflection temperature (HDT) and maximum decomposition temperature (Tmax) to 89.18? and 500.2?, respectively. In seeking to enhance tensile strength and thermal conductivity, maleated polyethylene (MAPE) and alumina (Al2O3) were studied in the SSPCM/HDPE composite. In the end, the SSPCM/HDPE composite exhibited great heat resistance, mechanical property and thermal conductivity.

Magnetic and Electrical Properties of Iron-Based Soft Magnetic Composites with Silicone Resin Insulation Coating

This paper investigates the magnetic and electrical properties of iron silicone resin soft magnetic composites. Scanning electron microscopy, energy dispersive X-ray spectroscopy analysis, distribution maps and density measurements confirm that the particles surface layer contains a thin layer of silicone resin with complete coverage of powders surface. The thickness of silicone resin film is averagely 120nm according to the results of transmission electron microscopy. Magnetic measurements show that the silicone resin insulation has a greater heat resistance than the conventional phosphate insulation, which enables stress reliving during annealing at higher temperature (600°C) without a large increase in magnetic loss. The results of annealing at 600°C show that the electrical resistivity increased from 8μΩ·m for SOMALOYTM samples to 55μΩ·m for the silicone insulated composites produced in this work.

Development of a Dry Inoculation Method for Thermal Challenge Studies in Low-Moisture Foods by Using Talc as a Carrier for Salmonella and a Surrogate (Enterococcus faecium)

The objective of this study was to obtain dry inocula of Salmonella Tennessee and Enterococcus faecium, a surrogate for thermal inactivation of Salmonella in low-moisture foods, and to compare their thermal resistance and stability over time in terms of survival. Two methods of cell growth were compared: cells harvested from a lawn on tryptic soy agar (TSA-cells) and from tryptic soy broth (TSB-cells). Concentrated cultures of each organism were inoculated onto talc powder, incubated at 35°C for 24 h, and dried for additional 24 h at room temperature (23 ± 2°C) to achieve a final water activity of #0.55 before sieving. Cell reductions of Salmonella and E. faecium during the drying process were between 0.14 and 0.96 log CFU/g, depending on growth method used. There was no difference between microbial counts at days 1 and 30. Heat resistance of the dry inoculum on talc inoculated into a model peanut paste (50% fat and 0.6 water activity) was determined after 1 and 30 days of preparation, using thermal death time tests conducted at 85°C. For Salmonella, there was no significant difference between the thermal resistance (D85°c) for the TSB-cells and TSA-cells (e.g. day 1 cells D85°C = 1.05 and 1.07 min, respectively), and there was no significant difference in D85°C between dry inocula on talc used either 1 or 30 days after preparation (P > 0.05). However, the use the dry inocula of E. faecium yielded different results: the TSB-grown cells had a significantly (P < 0.05) greater heat resistance than TSA-grown cells (e.g. D85°C for TSB-cells = 3.42 min versus 2.60 min for TSA-cells). E. faecium had significantly (P < 0.05) greater heat resistance than Salmonella Tennessee regardless what cell type was used for dry inoculum preparation; therefore, it proved to be a conservative but appropriate surrogate for thermal inactivation of Salmonella in low-moisture food matrices under the tested conditions.

Increasing the Strength and Wear Resistance of Friction Composite Materials by Modifying Them with Boric Acid Polymethylene-P-Triphenyl Ester

The possibility is shown of controlling the strength and wear resistance of polymer friction materials based on rubbers by adding boric acid polymethylene-p-triphenyl ester without altering the basic production technology of the composites. The greater heat resistance of the modified friction composites is established.

Electrical properties of heat‐treated polylactic acid

AbstractPolylactic acid (PLA), a biodegradable plastic, has excellent electrical insulation properties at temperatures ranging from room temperature to around 70 °C. At temperatures higher than 70 °C, however, the insulation performance of PLA deteriorates due to its poor heat resistance. In this study, PLA was heat‐treated at 100 °C to endow it with greater heat resistance, and the effects of this heat treatment on the electrical properties of PLA were investigated. Before being subjected to heat treatment, the crystallinity (xc) of PLA was about 6%. After the heat treatment was begun, xc increased in proportion to the heat treatment time, such that measurements revealed that xc had increased to about 42% by 15 minutes after the start of the heat treatment. The temperature dependence of the insulation breakdown strength (EB) of heat‐treated PLA was investigated, and it was found that EB of heat‐treated PLA (PLA‐A) decreases at a more moderate rate at temperatures above 60 °C. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 180(1): 1–8, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21272