Rheological properties and foam preparation of biodegradable poly(butylene succinate)

To produce biodegradable poly(butylene succinate) (PBS) foam by compression molding, high viscosity PBS was prepared with dicumyl peroxide (DCP) as a crosslinking agent and trimethylolpropane trimethacrylate (TMPTMA) as a curing coagent by crosslink method. The influences of various factors on the foaming process and the properties of PBS foams were investigated. The results show that the use of DCP and TMPTMA simultaneously can effectively increase the melt viscosity of PBS. Zinc oxide/zinc stearate was used to reduce the thermal decomposition temperature of the blowing agent azodicarbonamide, which can balance well the vulcanization of PBS and the decomposition of blowing agent. Finally, closed‐cell PBS foams with degradable property have been successfully prepared by a traditional chemical compression molding foaming way. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effects of parameter changes on the structure and properties of low‐density polyethylene foam

Several parameters, such as crosslinking agent concentration, blowing agent concentration, and temperature, were varied to evaluate their effects on the structure and mechanical properties of low‐density polyethylene (LDPE) foams. Dicumyl peroxide (DCP) was used as crosslinking agent, while azodicarbonamide (ADC) was utilized as the blowing agent at different levels. The formulations were prepared by using a thermostatically controlled heated two‐roll mill and foamed by using a compression molding technique via a single‐stage foaming process at three foaming temperatures (165, 175, and 185°C). The resultant LDPE foams were characterized and found to have a closed cell structure. The density and gel content increased proportionally with crosslinking level, whereas density decreased when ADC level and foaming temperature were increased. Another characteristic evaluated was the foam cell size decreased when the crosslinking level and foaming temperature were increased. In contrast, increasing the ADC concentration only gave a maximum cell size increase up to 6 phr that decreased when 8 phr of ADC was used. Results also indicated that compression stress increased proportionally with DCP level and decreased when ADC concentration and foaming temperature were increased. Impact studies on the prepared foams showed that their ability to absorb impact energy decreased with increasing crosslinking level, foaming temperature, and blowing agent concentration. J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers     

聚丁二酸丁二醇酯泡沫材料的制备

采用模压化学发泡的方法制备了可生物降解的聚丁二酸丁二醇酯(PBS)泡沫材料,并研究了其性能.结果表明,采用过氧化二异丙苯(DCP)作交联剂辅以三羟基甲基丙烷三甲基丙烯酸酯(TMPTAM)作助交联剂能明显提高PBS的黏度,使其具有较高的熔体强度.当DCP用量为4～5份时,泡沫材料泡孔均匀且密度适中,同时,PBS泡沫材料在...     

Extruded foams from microbial poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) and its blends with cellulose acetate butyrate

Extrusion foaming of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) and two blends of PHBV with cellulose acetate butyrate (CAB) were studied using an azodicarbonamide (AZ) blowing agent and a single‐screw extruder. The concentration of the blowing agent was systematically varied from 0 to 4.0 phr to achieve maximum density reduction reaching 41%, as well as to obtain information on the dependence of cell growth on blowing agent concentration. Extruded foams were characterized in terms of their bulk densities and cellular morphologies. Stereological and statistical methods permitted full characterization of the three‐dimensional cell size distributions, assessing the average cell diameters (ranging from 58 to 290 μm) and cell densities (ranging from 650 to 180,000 cm^?3). The variation in cellular morphology among foams consisting of different polymer matrix or blowing agent concentration was compared. The results were analyzed by considering the influence of viscoelastic properties of the polymer matrix on the bubble growth during foaming. Significantly higher melt viscosity and elasticity and reduced gas solubility of the PHBV/CAB blends are believed to retard cell coalescence and collapse during foam expansion, resulting in more uniform cell size distribution and better homogeneity of cellular morphology. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Manufacture of rigid PVC/wood‐flour composite foams using moisture contained in wood as foaming agent

Relatioships between the density of foamed rigid PVC/wood‐flour composites and the moisture content of the wood flour, the chemical foaming agent (CFA) content, the content of all‐acrylic foam modifier, and the extruder die temperature were determined by using a response surface model based on a four‐factor central composite design. The experimental results indicated that there is no synergistic effect between teh CFA content and the moisture content of the wood flour. Wood flour moisture could be used effectively as foaming agent in the production of rigid PVC/wood‐flour composite foams. Foam density as low as 0.4 g/cm³ was produced without the use of chemical foaming agents. However, successful foaming of rigid PVC/wood‐flour composite with moisture contained in wood flour strongly depends upon the presence of all‐acrylic foam modifier in the formulation and the extrusion die temperature. The lowest densities were achieved when the all‐acrylic foam modifier concentration was between 7 phr and 10 phr and extruder die temperature was as low as 170°C.     

Microcellular foaming of low‐density polyethylene using nano‐CaCo3 as a nucleating agent

In this study, microcellular foaming of low‐density polyethylene (LDPE) using nano‐calcium carbonate (nano‐CaCO₃) were carried out. Nanocomposite samples were prepared in different content in range of 0.5–7 phr nano‐CaCO₃ using a twin screw extruder. X‐ray diffraction and scanning electron microscopy (SEM) were used to characterize of LDPE/nano‐CaCO3 nanocomposites. The foaming was carried out by a batch process in compression molding with azodicarbonamide (ADCA) as a chemical blowing agent. The cell structure of the foams was examined with SEM, density and gel content of different samples were measured to compare difference between nanocomposite microcellular foam and microcellular foam without nanomaterials. The results showed that the samples containing 5 phr nano‐CaCO₃ showed microcellular foam with the lowest mean cell diameter 27 μm and largest cell density 8 × 10⁸ cells/cm³ in compared other samples. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Peroxide modification of poly(butylene adipate‐co‐succinate)

We attempted to introduce crosslinking into poly(butylene adipate‐co‐succinate) (PBAS) to improve the properties, such as the mechanical strength and elasticity, by a simple addition of dicumyl peroxide (DCP). Prior to curing, the thermal stability of PBAS was investigated. Above 170°C PBAS was severely degraded, and the degradation could not be successfully stabilized by an antioxidant. The PBAS was effectively crosslinked by DCP, and the gel fraction increased as the DCP content increased. A major structure of the crosslinked PBAS was an ester and aliphatic group. The tensile strength and elongation of PBAS were improved with an increasing content of DCP, but there was little affect on the tear strength. The biodegradability of crosslinked PBAS was not seriously deteriorated. A higher degree of crosslinking gave a lower heat of crystallization and heat of fusion. However, the melt crystallization temperatures of the crosslinked PBAS were higher than that of PBAS. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 637–645, 2001     

填料对乙烯-醋酸乙烯酯橡胶发泡材料性能的影响

使用无转子发泡硫化仪、RPA橡胶分析仪、体视显微镜以及力学性能测试仪器等研究了白炭黑和炭黑对乙烯-醋酸乙烯酯橡胶(EVM)硫化发泡特性、发泡材料微观结构和性能的影响。结果表明,白炭黑用量较少时,体系焦烧时间和正硫化时间均延长,发泡剂分解速度提高。与相同用量的白炭黑体系相比,炭黑体系不易焦烧,正硫化时间较长,发泡剂分解速度较快。白炭黑体系泡孔质量好于炭黑体系,其中添加30份白炭黑的泡沫材料具有最低密度。RPA分析结果表明,减少白炭黑用量或采用炭黑作填料均能降低体系储能模量(G′)和损耗模量(G″),炭黑体系泡沫材料动态模量具有较强温度敏感性。     

建筑用酚醛泡沫塑料制备与性能研究

在确定树脂黏度和固含量的前提下，考察了发泡温度、发泡剂、固化剂等对酚醛泡沫塑料性能的影响。结果表明，升高温度有利于发泡，但温度过高，泡沫发生穿孔现象。固化剂用量增大，泡沫起泡时间和指干时间缩短，当其用量在16～18份（质量份，下同）时，泡沫体表观质量较好。发泡剂用量增大，泡沫表观密度和压缩强度显著降低。当发泡剂用量大于12份后，泡沫体密度变化不大。     

Preparation of microcellular poly(ethylene‐co‐octene) rubber foam with supercritical carbon dioxide

In the past 3 decades, there has been great advancement in the preparation of microcellular thermoplastic polymer foams. However, little attention has been paid to thermoplastic elastomers. In this study, microcellular poly(ethylene‐co‐octene) (PEOc) rubber foams with a cell density of 2.9 × 10¹⁰ cells/cm³ and a cell size of 1.9 μm were successfully prepared with carbon dioxide as the physical blowing agent with a batch foaming process. The microcellular PEOc foams exhibited a well‐defined, closed‐cell structure, a uniform cell size distribution, and the formation of unfoamed skin at low foaming temperatures. Their difference from thermoplastic foam was from obvious volume recovery in the atmosphere because of the elasticity of the polymer matrix. We investigated the effect of the molecular weight on the cell growth process by changing the foaming conditions, and two important effect factors on the cell growth, that is, the polymer matrix modulus/melt viscoelastic properties and gas diffusion coefficient, were assessed. With increasing molecular weight, the matrix modulus and melt viscosity tended to increase, whereas the gas solubility and diffusion coefficient decreased. The increase in the matrix modulus and melt viscosity tended to decrease the cell size and stabilize the cell structure at high foaming temperatures, whereas the increase in the gas diffusion coefficient facilitated cell growth at the beginning and limited cell growth because most of the gas diffused out of the polymer matrix during the long foaming times or at high foaming temperatures. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Polylactide foams prepared by a traditional chemical compression‐molding method

To reduce environmental pollution and oil shortages, biodegradable polylactide (PLA) from plants was used to replace synthetic plastic from petroleum. In this study, high‐melt‐viscosity PLA was achieved through the in situ reaction of carboxyl‐ended polyester (CP) and solid epoxy (SE) first; then, PLA foams were successfully prepared by a chemical compression‐molding method. The detailed foaming factors were also studied, including the decomposition temperature of the blowing agent, the foam temperature, and the open‐mold temperature. The results reveal that the obtained PLA foams had good water absorption and degradable properties, and the foam density was low as 0.16 g/cm³. Moreover, the effects of the CP/SE concentration and the AC content on the properties of the foams were also investigated. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Preparation of Enhanced Poly(butylene succinate) Foams

Biodegradable poly(butylene succinate) (PBS) foams with high performance are usually difficult to be prepared because of its lower melt viscosity. Herein, high‐melt‐viscosity PBS was firstly prepared by combining the in situ reaction between carboxyl‐ended polyester (CP) and solid epoxy (SE) both as viscosifier and strengthening agent with the presence of crosslinking agent of dicumyl peroxide (DCP) and crosslinking co‐agent of trimethylolpropane trimethacrylate. Then enhanced PBS foams were successfully prepared by the traditional chemical compression‐molding method. Furthermore, the content effects of CP/SE, blowing agent azodicarbonamide, and DCP on the properties and morphologies of enhanced PBS foams were studied in details. Results revealed that the tensile strength of the as‐prepared PBS foams was as high as 32.3 MPa with the density of 0.58 g/cm³, which was higher than that of pure PBS resin (25.6 MPa). POLYM. ENG. SCI., 56:1275–1282, 2016. © 2016 Society of Plastics Engineers     

Preparation and properties of composites based on melamine‐formaldehyde foam and nano‐Fe3O4

In this work, a novel melamine‐formaldehyde‐Fe₃O₄ foam was prepared from a mixture containing melamine‐ethanolamine‐formaldehyde resin, melamine‐glycol‐formaldehyde resin and carboxylated Fe₃O₄ nanoparticles by microwave foaming method. The two resins were characterized by ¹³C‐NMR, respectively. The structures of foams, mechanical and fire‐retardant properties were experimentally characterized separately by scanning electron microscopy, universal testing machine, limit oxygen index, thermogravimetry‐differential thermal analysis, and Fourier transform infrared spectra. The effects of the resin viscosity, emulsifier, nucleating agent, curing agent, silicone oil, microwave heating time and blowing agent on the structure of foam were investigated. Results showed that the properties of foam were decided by not only the molecular structure but also structure of foam, and the carboxylated Fe₃O₄ nanoparticles can improve the toughness and flame retardant properties of magnetic foam obviously from both aspects. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2688–2697, 2013     

软质PVC发泡材料的研究

采用化学发泡一步法模压成型制备了软质PVC发泡材料,研究了发泡剂、泡孔成核剂、改性剂等主要助剂用量对软质PVC发泡材料密度、泡孔结构以及力学性能的影响,并进行了软质PVC发泡材料的配方筛选.结果表明加入吸热发泡剂N能提高发泡体系的发泡效果,降低材料的密度,改善材料的力学性能,当发泡剂AC用量为2份,用量为0.6份时,材料的综合性能优异;当成核剂用量为1份时,体系发泡效果较好;加入粉末NBR不仅能提高发泡材料的断裂伸长率和柔韧性,还可降低发泡材料密度,改善泡孔结构;当NBR用量为20份时,发泡材料密度达到0.44 g/cm3,力学性能优异.     

Novel preparation and mechanical properties of rigid polyurethane foam/organoclay nanocomposites

A novel method for preparing rigid polyurethane (PU) foam/organoclay nanocomposites was developed through the direct incorporation of an organoclay into PU foam matrices without the addition of any physical or chemical blowing agent. The resultant foams with an appropriate content of the organoclay had a finer cell structure than the pristine PU foams because the organoclay not only acted as a nucleating agent as expected but also acted as a blowing agent of the PU foams; this could be attributed to the bound water between the interlayers of the organoclay. In addition, the incorporation of the organoclay up to 4 phr resulted in improvements in the tensile and compressive strengths, with the maximum values appearing at 2 phr (110 and 152%, respectively). The significant improvement in the mechanical properties could be attributed to the finer cell structure and the increased internal strength of the materials due to the higher degree of hydrogen bonding. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

A conductive foam: Based on novel poly(styrene‐b‐butadiene‐co‐styrene‐b‐styrene) tri‐block copolymer filled by carbon black

In this article, a conductive foam based on a novel styrene‐based thermoplastic elastomer called poly(styrene‐b‐butadiene‐co‐styrene‐b‐styrene) tri‐block copolymer S(BS)S was prepared and introduced. S(BS)S was particularly designed for chemical foaming with uniform fine cells, which overcame the shortcomings of traditional poly(styrene‐b‐butadiene‐b‐styrene) tri‐block copolymer (SBS). The preparation of conductive foams filled by the carbon black was studied. After the detail investigation of cross‐linking and foaming behaviors using moving die rheometer, the optimal foaming temperature was determined at 180°C with a complex accelerator for foaming agent. Scanning electron microscopy (SEM) images shown that the cell bubbles of conductive foam were around 30–50 µm. The conductivity of foams was tested using a megger and a semiconductor performance tester. SEM images also indicated that the conductivity of foams was mainly affected by the distribution of carbon black in the cell walls. The formation of the network of the carbon black aggregates had a contribution to perfect conductive paths. It also found that the conductivity of foams declined obviously with the foaming agent content increasing. The more foaming agent led to a sharp increasing of the number of cells (from 2.93 × 10⁶ to 6.20 × 10⁷ cells/cm³) and a rapid thinning of the cell walls (from 45.3 to 1.4 µm), resulting in an effective conductive path of the carbon black no forming. The conductive soft foams with the density of 0.48–0.09 g/cm³ and the volume resistivity of 3.1 × 10³?2.5 × 10⁵ Ω cm can be easily prepared in this study. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41644.     

聚丁烯-1模压发泡工艺研究

以聚丁烯-1(PB-1)为基体,过氧化二异丙苯(DCP)为交联剂,偶氮二甲酰胺(AC)为发泡剂,采用模压发泡法制备了PB-1发泡材料,分别研究了AC用量、DCP用量和滑石粉用量对PB-1发泡材料性能的影响.结果表明:当DCP用量为0.15份、AC用最为2.00份、滑石粉用量为5.00份时,PB-1发泡材料的综合性能最佳.     

Continuous extrusion of microcellular polycarbonate

Extruded microcellular foams have been obtained from mixtures of polycarbonate (PC) and n‐pentane. Cell diameters were in the range of 2 to 5 μm and the foam densities varied between 400 and 700 kg/m³. Although two types of PC have been investigated, one linear and one branched, the presence of side branchings did not modify the extruded foam characteristics. Use of carbon dioxide as the blowing agent was also attempted, and cell sizes below 10 μm have been successfully obtained. One prerequisite for microcellular foaming was believed to consist in a concentration of the blowing agent close to its limit of solubility as that defined under the actual processing conditions of pressure and temperature. This hypothesis was validated from the observation of extrusion of regular PC foams (intermediate to low densities and cell sizes ranging between 100 μm and 1 mm) using moderate concentrations of blowing agents, and from solubility and viscosity measurements on similar polymer/blowing agent systems.     

Low‐temperature clean preparation of poly(lactic acid) foams by combining ethyl lactate and supercritical CO2: correlation between processing and foam pore structure

This study reports the low‐temperature and clean fabrication of porous poly(lactic acid) (PLA) through solid‐state foaming using various mixtures of ethyl lactate (EL) and supercritical CO₂ (scCO₂) as the blowing agent. Results showed that adding a small amount of EL (up to 0.2% molar fraction) to scCO₂ enhanced the plasticizing effect of the blowing agent mixture. As a direct consequence, at an operating temperature of 35 °C, PLA foams could be manufactured with homogeneous morphology, density as low as 0.09 ± 0.01 g cm^?3, mean pore sizes up to 519.0 ± 205.0 µm and pore densities in the range 2.0 × 10⁵ to 3.4 × 10⁸ pores cm^?3. Conversely, at a temperature of 40 °C, an increase of plasticizer concentration in the blowing agent mixture up to 0.2% promoted the crystallization of the polymer during sorption stage and, consequently, foaming was slightly reduced. © 2013 Society of Chemical Industry     

Development of water‐blown bio‐based thermoplastic polyurethane foams using bio‐derived chain extender

Water‐blown bio‐based thermoplastic polyurethane (TPU) formulations were developed to fulfill the requirements of the reactive rotational molding/foaming process. They were prepared using synthetic and bio‐based chain extenders. Foams were prepared by stirring polyether polyol (macrodiol), chain extender (diol), surfactant (silicone oil), chemical blowing agent (distilled water), catalyst, and diisocyanate. The concentration of chain extender, blowing agent, and surfactant were varied and their effects on foaming kinetics, physical, mechanical, and morphological properties of foams were investigated. Density, compressive strength, and modulus of foams decrease with increasing blowing agent concentration and increase with increasing chain extender concentration, but are not significantly affected by changes in surfactant concentration. The foam glass‐transition temperatures increase with increasing blowing agent and chain extender concentrations. The foam cell size slightly increases with increasing blowing agent content and decreases upon surfactant addition (without any dependence on concentration), whereas chain extender concentration has no effect on cell size. Bio‐based 1,3‐propanediol can be used successfully for the preparation TPU foams without sacrificing any properties. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013