聚丙撑碳酸酯的辐射效应

研究了室温条件下聚丙撑碳酸酯(PPC)在钴-60和电子加速器辐照过程中的响应行为。结果表明,聚丙撑碳酸酯是一种辐射裂解型聚合物,其分子量随着辐射剂量的增加而减小。1mm厚PPC片材在室温和N2气保护条件下,其裂解G值为Gs,γ-ray=10.81;Gs,EB=4.9。不同的裂解G值表明,O2气在聚丙撑碳酸酯的辐射裂解过程中有重要影响。红外光谱研究表明,辐射后聚丙撑碳酸酯在3474cm-1处的峰宽峰高增加,表明其裂解后端—OH基增加。由于裂解作用,辐射后聚丙撑碳酸酯的抗张强度和断裂伸长率均下降。在通常的辐射消毒剂量范围内(25~50kGy),PPC的保留抗张强度大于23MPa,断裂伸长率大于4%,裂解后试样的力学性能依然能够满足实际应用需要,因此PPC可以经受辐射消毒。     

聚丙烯/聚乙烯共混物的辐射凝胶生成动力学研究

本文研究辐照PP/HDPE共混物的溶胶生成分数s与辐照剂量R的关系,结果表明适用于某些纯聚合物辐射交联规律的Charlesby-Pinner关系式和陈-刘-唐关系式皆不适用于PP/HDPE共混体系。张万喜等人曾研究过许多纯聚合物的辐射交联,提出裂解度正比于R~β的假定,β是与高分子结构相关的参数,这个假定可与大多数聚合物的辐射交联实验数据符合。同样的假定被应用于本文的共混体系,不同的是根据共混物结构特点对R~β项进行了必要的修正,即共混物的R~β=∑f_iR~(βI),其中f_i,β_i分别为共混物第i组分的重量分数及β值。用修正后的R~β处理辐照PP/HDPE共混物的实验数据,R(s+√s)～R~β,有很好的线性关系。     

辐照对聚己内酯结构和性能的影响

研究了γ 辐照对不同分子量的聚己内酯 (PCL)的力学性能、热性能、结晶行为的影响 ,在此基础上 ,研究了辐射交联后的PCL的形状记忆行为 .研究结果表明 ,PCL的分子量越大 ,辐射交联所需的凝胶化剂量越低 .溶胶分数S +S1 2 与 1 D的关系很好地符合Charlesby Pinner关系式 ,说明PCL的辐射交联属于无规交联 .剂量对PCL的力学性能影响显著 ,剂量越大 ,抗张强度和断裂伸长率下降越多 ,但分子量较高的PCL的抗张强度受剂量的影响较小 .DMA分析表明 ,聚己内酯辐照交联后的弹性模量和耐热性能显著提高 .交联度较高的PCL表现出高弹态 ,可以拉伸 ,并具有较好的形状记忆行为 .DSC分析表明 ,辐射交联使PCL的结晶度有所增加 ,但也使结晶熔点有所降低     

二甲基二烯丙基氯化铵的辐射聚合和性质研究

对二甲基二烯丙基氯化铵进行了辐射聚合,得到线型聚合物的交联的水凝胶, 实验测定了线型聚合的转化率与剂量和水凝胶的凝胶的凝胶分数、平衡溶胀与剂量 的关系。结果表明聚二甲基二烯丙基氯化铵水凝胶的凝胶含量与剂量的关系符合 Charlesby-Pinner公式,外推S + S~(1/2) = 2求得凝胶剂量D_g,从而求出G(x) 等值;并首次利用二甲基二烯丙基氯化铵及其聚合物稀水溶液的电导率与浓度的线 性关系,发展了一种对电解质的辐射聚合反应转化率的电导测定法。     

K-型卡拉胶/聚乙烯吡咯烷酮共混水凝胶的辐射合成

采用辐射技术合成了K 型卡拉胶 (KC) /聚乙烯吡咯烷酮 (PVP)共混水凝胶 ,研究了天然高分子KC、单体N 乙烯基吡咯烷酮 (N VP)、交联剂二甲基丙烯酸十四甘醇酯 ( 1 4G) ,辐照剂量以及剂量率等对辐射合成的KC/PVP共混水凝胶性质的影响 .实验发现 ,KC与适当比例的N VP共混后在一定剂量范围内辐照可得到高强度、高溶胀行为的KC/PVP共混水凝胶 ,随着共混凝胶内KC含量的相对增加 ,凝胶强度及溶胀性的能均显著提高 ,但合成该共混凝胶的最佳剂量却相对提前 ;加入 1 4G后降低了KC/PVP共混凝胶辐射合成最佳剂量 ,同时使KC/PVP共混凝胶的强度进一步提高 ;剂量、剂量率对KC/PVP共混凝胶的性质亦有很大的影响 .分析表明 ,KC与N VP共混后 ,在较低剂量下KC的降解被抑制 ,从而获得一种由物理交联的KC和化学交联的PVP形成的互穿网络 (IPN)凝胶     

结晶对等规立构聚甲基丙烯酸甲酯辐射消旋和辐射裂解的影响

本文通过核磁氢谱、DSC和分子量测定,研究了结晶对等规立构聚甲基丙烯酸甲酯辐射消旋和辐射裂解的影响.分子量测定的结果表明,等规立构聚甲基丙烯酸甲酯结晶后,其辐射裂解反应减弱,裂解G值减小将近一半.核磁氢谱测定辐照试样的空间立构变化结果为:随着辐照剂量的增加,等规立构逐渐变为无规立构和间规立构,其变化规律相似于非晶试样.结果还表明,晶区的消旋反应比裂解反应更为显著.DSC测得的试样熔点,随着辐照剂量的增加而急剧下降,由Flory结晶熔化理论计算得晶区的辐射破坏G值为8.8.该值远大于聚乙烯晶区的破坏G值.     

聚己内酯/聚酯丙烯酸酯共混物的辐射交联及其形状记忆行为

研究了聚酯丙烯酸酯 (PEA)类多官能团物质与聚己内酯 (PCL)共混物的辐射交联效应 .分别考察了多官能团PEA的用量、官能团数目、辐射交联剂量等因素对聚己内酯的辐射交联规律、动态力学性能、形状记忆行为等性能的影响 .结果表明 ,PCL PEA共混物的辐射交联规律不再遵从Charlesby Pinner关系式 ,而是符合陈欣方 刘克静 唐敖庆关系式 .多官能团PEA的加入可以显著提高PCL辐射交联的效率 ;相同剂量时 ,官能团数目越多、用量越大的样品 ,生成的凝胶含量越多 ,强化辐射交联效应越大 .DMA分析表明 ,PCL强化辐照交联后的弹性模量和耐热性能显著提高 .强化交联PCL在其熔点以上都呈现出高弹态平台 ,可以实现形状记忆 .且交联度较高 ,形状记忆恢复速率较快 .     

PMMA-PEO共混体系的辐射交联

<正> 聚甲基丙烯酸甲酯(PMMA)是典型的辐射裂解型聚合物。经辐照后,PMMA主链发生无规断裂。在聚合物共混体系中,PMMA是否能发生交联,这是辐射化学中一个非常重要的研究课题之一,也是一项探索性工作。 PMMA-PEO共混体系是可以分子水平共溶的体系。本文试图将共混体系的相容性与共混体系中的裂解型聚合物的辐射效应联系起来,讨论PMMA-PEO共混体系的辐射交联。     

结晶对等规立构聚甲基丙烯酸甲酯辐射消旋和辐射裂解的影响

 本文通过核磁氢谱、DSC和分子量测定,研究了结晶对等规立构聚甲基丙烯酸甲酯辐射消旋和辐射裂解的影响.分子量测定的结果表明,等规立构聚甲基丙烯酸甲酯结晶后,其辐射裂解反应减弱,裂解G值减小将近一半.核磁氢谱测定辐照试样的空间立构变化结果为:随着辐照剂量的增加,等规立构逐渐变为无规立构和间规立构,其变化规律相似于非晶试样.结果还表明,晶区的消旋反应比裂解反应更为显著.DSC测得的试样熔点,随着辐照剂量的增加而急剧下降,由Flory结晶熔化理论计算得晶区的辐射破坏G值为8.8.该值远大于聚乙烯晶区的破坏G值.     

聚乙烯醇/羧甲基壳聚糖共混水凝胶的辐射合成及性能

采用电子加速器辐照法制备了聚乙烯醇(PVA)/羧甲基壳聚糖(CMCH)共混水凝胶;研究了PVA与CMCH的配比、辐照剂量、温度以及pH值对PVA/CMCH共混水凝胶性能的影响.实验发现,PVA与CMCH在辐照剂量为40 kGy、配比为w(PVA)/w(CMCH)=5/1的条件下可得到强度较好的PVA/CMCH共混水凝胶,该水凝胶具有一定的温度和pH敏感性:在5~20℃时具有较高的溶胀率,温度在20℃以上溶胀率较低;水凝胶在pH<4.0和pH>6.0时溶胀率均较大,而当pH为4.0~6.0时溶胀率较小.     

Thermal expansion of irradiated polytetrafluoroethylene

The thermal expansion coefficient of gamma-irradiated Polytetrafluoroethylene (PTFE) has been measured in the temperature range 80–340 K by using a three-terminal capacitance technique. The samples are irradiated in air at room temperature with gamma rays from a Co⁶⁰ source at a dose rate of 0.26 Mrad/h. The change in crystallinity is measured by an x-ray technique. The expansion coefficient is found to increase with radiation dose below 140 K owing to the predominant effect of degradation. Above 140 K, the expansion coefficient is found to decrease with radiation dose because of the enhanced crystallinity. The temperatures of the two first-order phase transitions are also found to shift to lower temperatures owing to degradation of PTFE.     

•OH对聚二甲基硅氧烷乳液辐射效应的影响

通过凝胶和溶胶分析与分子量测定的方法，研究了不同体系下，^•OH对PDMS乳液γ辐射效应的影响. 结果表明，^•OH不仅可引发聚二甲基硅氧烷的分子间交联，也能促进其降解. 对于纯PDMS乳液，在所研究的剂量范围内，^•OH对其辐射交联行为影响较小. 但若体系中加入H2O2、KIO4 和 N2O这些提高^•OH生成产额的添加剂时，^•OH对PDMS的促降解作用会随着吸收剂量增加而表现更明显，导致凝胶含量与纯乳液辐照情况相比下降较多. 即使加入交联剂-三羟甲基丙烷三甲基丙烯酸酯（TMPTMA），在过量的^•OH存在下，当吸收剂量大于40 kGy以上时，TMPTMA不仅没有提高交联度，反而会与^•OH协同，使PDMS的凝胶含量下降更显著，同时产生更多的小分子聚合物，并使PDMS的平均分子量分布变窄. 这可能是由于交联剂首先与^•OH作用，形成的产物会加快PDMS的降解.     

·OH对聚二甲基硅氧烷乳液辐射效应的影响

通过凝胶和溶胶分析与分子量测定的方法,研究了不同体系下,"OH对PDMS乳液γ辐射效应的影响.结果表明,"OH不仅可引发聚二甲基硅氧烷的分子间交联,也能促进其降解.对于纯PDMS乳液,在所研究的剂量范围内,"OH对其辐射交联行为影响较小.但若体系中加入H2O2、KIO4和N2O这些提高"OH生成产额的添加剂时,"OH对PDMS的促降解作用会随着吸收剂量增加而表现更明显,导致凝胶含量与纯乳液辐照情况相比下降较多.即使加入交联剂-三羟甲基丙烷三甲基丙烯酸酯(TMPTMA),在过量的"OH存在下,当吸收剂量大于40kGy以上时,TMPTMA不仅没有提高交联度,反而会与"OH协同,使PDMS的凝胶含量下降更显著,同时产生更多的小分子聚合物,并使PDMS的平均分子量分布变窄.这可能是由于交联剂首先与"OH作用,形成的产物会加快PDMS的降解.     

聚琥珀酸丁二酯的辐射交联和它的热变形行为

近年来 ,塑料废弃物污染环境的问题日趋严重 .对于环境的关心 ,已经使越来越多的科研人员对于研究环境友好化合物的发展产生了极大的兴趣 .发达国家先后制订了限制或禁止某些场合使用非降解性塑料 ,因此 ,多种可生物降解性塑料已经发展起来 .目前已经商业化的可生物降解性聚合物主要有脂肪族聚酯、聚醚、聚乙烯醇和聚多糖 .其中 ,利用化学合成法开发的可生物降解性聚合物是非常重要的 .脂肪族聚酯 ,例如聚乳酸(ＰＬＡ) .聚乙二酸 (ＰＧＡ)等被广泛地用于药物的载体[1] ,聚 (ε 己内酯 ) (ＰＣＬ)也已经被用作生产生物降解性薄膜 .脂肪族聚酯…     

Formation and characterization of a hydrophilic polymer hydrogel under gamma irradiation

Formation and characterization of hydrogel of a hydrophilic polymer in a wide range of gamma absorbed doses is reported. An aqueous solution contains 2% polyvinyl alcohol (PVA) by mass irradiated under gamma rays of ⁶⁰Co was chosen for study. The hydrogel was synthesized without using any additives. It was found that gel fraction is an exponential saturation function that increases with an increase of absorbed dose while swelling ratio is an exponential saturation function that decreases with an increase of absorbed dose. The results are described by energy transfer model.     

Effect of gamma irradiation on ethylene–octene copolymers

Two ethylene–octene copolymers (POE) were irradiated with ⁶⁰Co gamma radiation and influence of irradiation atmosphere, absorbed dose and heat treatment of samples on the crosslinking were studied. Thermal properties and crystalline morphology of non-irradiated and irradiated POE were determined by using differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXS), respectively. The Charlesby–Pinner equation was used to describe the relationship between absorbed dose and sol fraction. The gel fraction of irradiated POE was lower and decreased with the increase of octene content when irradiated in oxygen, compared to irradiation in nitrogen atmosphere. The gel fraction increased significantly with the increasing of absorbed dose for the two copolymers. Heat treatment of samples prohibited the crosslinking of irradiated POE. The DSC results indicated that a subtle change of thermal properties of POE was observed before and after gamma irradiation at low dose. No change was found from the WAXS spectra of non-irradiated and irradiated POE. For heat-treating samples, the Charlesby–Pinner equation can not fit perfectly with the relationship between the sol fraction and absorbed dose, but it fits well with the crosslinking reaction of POE pellets.     

Effect of electron radiation and triallyl isocyanurate on the average molecular weight and crosslinking of poly(ε‐caprolactone)

Investigation of the effect of electron radiation on the flow rate and average molecular weight of poly(ε‐caprolactone) (PCL) as well as on formation of the gel fraction of this polymer being irradiated in the presence of triallyl isocyanurate (TAIC) was the aim of the present paper. It was found that PCL macromolecules upon the electron radiation underwent both degradation and linking, because of which the polymer molecular weight increased. The processes associated with elongation of the polymer chains prevailed over the degradation ones. It was also found that PCL irradiated in the presence of TAIC underwent crosslinking resulting in formation of a significant amount of the gel fraction. The largest amount of this fraction was created upon the radiation with the dose of 60 kGy, which was confirmed by the results of determination of the swelling index. Changes in properties of PCL, occurring because of the electron radiation, are important for controlling viscosity of polymeric materials during processing of these materials. Copyright © 2015 John Wiley & Sons, Ltd.     

Thermal expansion of irradiated polyoxymethylene

The thermal expansion coefficient of gamma irradiated polyoxymethylene has been measured in the temperature range 80–340 K by using a three terminal capacitance technique. The radiation induced changes are measured by recording the i.r. spectra of the irradiated samples. The change in crystallinity caused by irradiation is measured by an X-ray technique. The thermal expansion coefficient increases with radiation dose below 170 K due to the predominant effect of degradation. Above 170 K, this trend reverses and the expansion coefficient decreases with radiation dose due to the increased crystallinity caused by irradiation.     

Radiation effect studies on anticancer drugs, cyclophosphamide and doxorubicin for radiation sterilization

Two anticancer drugs, cyclophosphamide (CPH) and doxorubicin hydrochloride (DOXO), in powder form were exposed to a range of doses of ⁶⁰Co gamma and electron beam radiation to study the effects of ionizing radiation. Pharmacopoeia tests, discolouration, degradation products, effect of irradiation temperature and dose rate were investigated. CPH undergoes less than 2% degradation at 30 kGy. Chromatographic studies revealed formation of several trace level degradation products, discolouration and free radicals in the irradiated CPH. N,N-bis (2-chloroethyl) group in the molecule is particularly sensitive to radiation degradation. Irradiation to 5 kGy at low temperature (77 K) did not result in significant changes. DOXO was observed to be quite radiation resistant and did not undergo significant changes in its physico-chemical properties and degradation product profile. It can be radiation sterilized at normal sterilization dose of 25 kGy.     

Three-dimensional polymer gel dosimetry: basic physical properties of the dosimeter

This study concentrated on assessment of the basic physical properties of a polymer gel dosimeter evaluated by NMR. For this, BANG-2 type polymer gel was prepared. The dosimeters were irradiated by ⁶⁰Co gamma photons and by 4, 6 and 18 MV X-ray photons for doses in the range 0–50 Gy. The multi-echo CPMG sequence was used for the evaluation of T₂-relaxation times in the irradiated gel dosimeters. Dependence of 1/T₂ in terms of the following factors was studied: absorbed dose, energy of applied radiation, temperature during NMR evaluation, time between irradiation and NMR evaluation and strength of the magnetic field. An exponential dependence of the 1/T₂ response on absorbed dose in the range 0–50 Gy was observed, while in the range 0–10 Gy the data could be fitted by a linear function. This paper also describes the dependence of 1/T₂ response on: radiation energy, strength of magnetic field and time from irradiation of the dosimeters to NMR evaluation. Increase of gel dosimeter 1/T₂ response with the decrease of the temperature during NMR evaluation has been qantitatively described. The polymer gel dosimetry system used in this study proved that it is a reliable system for three-dimensional dose distribution measurement.