The effect of citrate esters as plasticizers on the thermal and mechanical properties of poly(methyl methacrylate)

Plasticizers play a key role in the formulation of polymers and in determining their physical properties and processability. This study examines the effects of citrate esters, triethylcitrate, and triacetine as plasticizers on the thermal and mechanical properties of poly(methyl methacrylate). The samples were characterized by differential scanning calorimetry, dynamical mechanical analysis, and mechanical testing under different plasticizer contents. Both citrate esters proved to be effective as plasticizers, DSC data for the triacetine additive fits with Fox equation. Microstructure and relaxation properties were studied by dynamic mechanical analysis where loss modulus shows clearly that absorbed plasticizer shifts the α‐transition to lower temperature and β‐relaxations associated to ester side groups are unchanged even up to 30 wt % plasticizer. Mechanical properties were evaluated with an Instron testing machine. Both additives produced (1) an initial plasticization, with a decrease in tensile strength and modulus; (2) an antiplasticization, reflected as an increase in tensile strength; and modulus and (3) a final plasticization, with a notable decrease in tensile strength and modulus and an increase in elongation where a 35 wt % of triethylcitrate added to the poly(methyl methacrylate) increased in 200% its elongation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

PEG/N-100中增塑剂扩散性能的微观与介观模拟

为探究含能钝感增塑剂三羟甲基乙烷三硝酸酯(TMETN)在硝酸酯增塑聚醚(NEPE)推进剂黏合剂中的扩散性能,采用分子模拟(MD)法比较了硝化甘油(NG)、1,2,4-丁三醇三硝酸酯(BTTN)及TMETN在聚乙二醇/固化剂(PEG/N-100)中的扩散系数、分析了扩散机理,并讨论了温度及增塑比对TMETN扩散性能的影响。结果表明:增塑剂扩散系数的大小顺序为NGBTTNTMETN,这说明TMETN的扩散能力较弱;从微观角度分析扩散的机理为:增塑剂与预聚体的分子间相互作用越强、体系的自由体积分数越小、增塑剂分子的尺寸越大,则增塑剂越难发生扩散;在三种增塑体系中,TMETN与PEG/N-100的结合能力最强、原子间氢键作用最强、该体系中PEG/N-100的自聚集能力最弱,且TMETN分子尺寸最大,故而TMETN最难发生扩散;随着温度升高,TMETN扩散系数的增加先缓慢后剧烈,这与高温加速老化的规律保持一致,分析温度对扩散机理的影响为:高温使原子间氢键作用峰值减小、位置后移,即增塑剂与黏合剂的相互作用减弱,并且体系的自由体积分数也变大;随着增塑比的增加(2.5、2.8、3),TMETN扩散系数减小,介观研究表明体系的相容性变好是其中的原因之一。     

Polymer properties associated with chemical permeation performance of disposable nitrile rubber gloves

Unlike other chemical protective clothing and devices, disposable gloves are not reliably certified to exceed chemical permeation performance standards. In light of generalized chemical compatibility charts, significant variability in performance exists between similar products on the market. This study evaluates whether nitrile rubber composition and uniformity are better associated with the observed product variability in chemical resistance than the available mechanical testing (e.g., tensile strength) done on these products. The independent variables evaluated include two physical, three mechanical, and four compositional parameters. Based on correlation and multiple regression analyses, the factors associated with variation in permeation of ethanol are area density, acrylonitrile content, carboxylation of the base polymer, the amount of extractable oils and oily plasticizers, and polymer uniformity. Increases in area density, acrylonitrile content, and carboxylation improve chemical resistance. Decreases in extractable oils and polymer variability (uniformity) also improve chemical resistance. On average, these combined factors accounted for about 53–67% of the observed variability in permeation, which were moderate but not strong associations. In contrast, tensile strength accounted for about 1% of the observed variability, a negligible effect. These results support the notion that standardized tests and certification criteria need to address polymer composition and uniformity to reduce gaps in performance. However, in light of the lack of strong correlations, further evaluation with tighter control over chemical composition is warranted. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41449.     

Influence of plasticizer with different functional groups on thermoplastic starch

Retrogradation of amorphous thermoplastic starch (TPS) films obtained by compression molding of spray dried modified potato starch was investigated. The aim was to investigate the influence of plasticizers with similar molecular weight but different functionality, i.e., isoleucine, asparagine and malic acid, on the properties of plasticized powder and TPS films. Combinations of malic acid with glycerol, urea, and maltodextrin were also evaluated. Except for isoleucine formulated starch, all samples were obtained as amorphous powders and films. Malic acid was identified as a strong antiretrogradation agent as it inhibited recrystallization of starch over the full range of humidity levels. Malic acid was also found to inhibit the retrogradation of formulations containing urea, glycerol and maltodextrin. The converse of the strong inhibition implied strong moisture absorption and high strain at break values, and low tensile strengths. Malic acid was also identified as a potential crosslinking agent to control swelling of starch‐based products. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42012.     

Protein‐based bioplastics and their antibacterial potential

The use of conventional petroleum‐based plastics in many applications poses the risk of contamination, potentially causing infection when used in medical applications, and contamination when used in food packaging. Nontraditional materials such as protein are being examined for their potential use in the production of bioplastics for applications that require uncontaminated materials. The proteins of albumin, soy, and whey provide possible sources of raw material for bioplastic production, as they have already been utilized in the area of edible films and low‐stress applications. We conducted this study to investigate the thermal, viscoelastic, and antibacterial properties of the albumin, soy, and whey bioplastics with the use of three plasticizers—water, glycerol, and natural rubber latex (NRL). Bacillus subtilis and Escherichia coli were utilized as Gram (+) and Gram (?) species, respectively, for antimicrobial analysis. Albumin and whey bioplastics exhibited similar thermal and viscoelastic properties, whereas soy bioplastics had varied viscoelastic properties based on the plasticizer used. In terms of antibacterial activity, the albumin–glycerol and whey–glycerol were the best bioplastics, as no bacterial growth was observed on the plastics after 24 h of inoculation. In terms of the future impact of this research, the aim will be to scale up production of the bioplastics for use in food packaging as well as biomedical applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41931.     

Bronsted-Lewis双酸性离子液体催化合成对苯二甲酸二(二乙二醇丁醚)酯

制备了具有不同SnCl2摩尔分数的Bronsted-Lewis双酸性离子液体3-(1-吡啶基)丙磺酸-氯化亚锡离子液体([3-(1-Py)-(CH2)3-SO3H]Cl-xSnCl2),x为Lewis所占的摩尔分数。用吡啶探针红外光谱作为表征手段,比较了不同x值催化剂的酸性强度变化,并将其应用于对苯二甲酸二(二乙二醇丁醚)酯的合成反应。考察了x值、原料配比、催化剂用量、带水剂用量、反应时间等因素对酯化率的影响,并对精制产品用1HNMR进行结构表征。结果表明,当x=0.5时,该离子液体的催化活性最高。以[3-(1-Py)-(CH2)3-SO3H]Cl-0.5SnCl2为催化剂,对苯二甲酸(PTA)和二乙二醇丁醚(DGBE)的摩尔配比n(DGBE):n(PTA)=2.3:1,催化剂用量为4.0%(PTA质量),带水剂正丁醚用量为60.0%(PTA质量),反应时间为2.5h,搅拌转速300r/min时,产品的酯化率高达99.43%。催化剂在不进行任何处理的情况下,可以循环使用5次。 关键词：双酸性离子液体;对苯二甲酸; 二乙二醇丁醚 ;对苯二甲酸二(二乙二醇丁醚)酯;增塑剂     

废弃资源回收PTA制备环保增塑剂DOTP研究

采用酸析法从碱减量废水中回收对苯二甲酸(PTA),考察酸析温度和p H值对PTA纯度和回收率等的影响;利用回收PTA作为原料制备环保增塑剂对苯二甲酸二异辛酯(DOTP),并对其制备工艺条件进行了考察,确定最佳工艺条件为:醇酸物质的量比2.4∶1,催化剂用量为0.5%,反应温度220℃,反应时间4 h;通过对制备DOTP产品进行红外分析和质量检验,结果表明,利用PTA回收料制备DOTP的质量合格,符合国家工业标准。     

我国对邻苯二甲酸酯类化合物检测方法的研究现状

邻苯二甲酸酯类作为塑料添加剂有80年的历史,很容易迁至食品和环境中,影响人类的身体健康。本文对邻苯二甲酸酯类化合物检测方法做了总结,为进一步认识邻苯二甲酸酯类化合物提供参考。     

Reactive Energetic Plasticizers for Energetic Polyurethane Binders Prepared via Simultaneous Huisgen Azide‐Alkyne Cycloaddition and Polyurethane Reaction

Reactive energetic plasticizers (REPs) for use in glycidyl azido polymer (GAP) based polyurethane (PU) energetic binders were investigated. These REPs consisted of an activated terminal alkyne group that was expected to give rise to Huisgen azide‐alkyne 1,3‐dipolar cycloaddition within the specific pot life for a PU formulation to prevent the migration of plasticizers, and with a gem‐dinitro group as an energy resource. A quantitative miscibility investigation between the plasticizers and uncured GAP showed that REPs exhibited better miscibility than conventional energetic plasticizers. The plasticization effect of the REPs on the GAP prepolymer with respect to the reduction of the viscosity illustrated REPs can effectively reduce the viscosity of the GAP prepolymer from 6,015 cP to 150–240 cP at the processing temperature when 50 wt‐% of REP was added. A comparison of the click reactivity and activation energies (E_a) of REPs and GAP prepolymer elucidated that the reactivity of azide‐alkyne cycloaddition depended on the dipolarophilicity of REPs which could be controlled by adjusting the length of methylene spacer between electron‐withdrawing groups (EWG) and neighboring alkynes in REPs. Thermogravimetric analysis manifested REP/GAP‐based PU binders maintained the thermal stability of the control GAP‐based PU binder. The mechanical properties and impact insensitivity of the GAP‐based PU binders were also improved by the incorporation of REPs.