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以D,L-丙交酯和蚕丝丝素蛋白(SF)为原料,在氯化亚锡/对甲苯磺酸体系的催化作用下聚合得到丝素蛋白改性聚D,L-乳酸的共聚物(PSFLA)。该共聚物的结构与性能采用红外光谱法、1H NMR、热重分析、差示扫描量热法、粘度法、旋光度法和扫描电镜等方法进行研究。所得的PSFLA均不具有光学活性,但原料配比对共聚物的微结构与结晶性能有重要的影响。当D,L-丙交酯与丝素蛋白的质量比为6∶1时,共聚物中可能形成了络合结晶,结晶的熔点为128℃,且随着D,L-丙交酯用量的增加,结晶的熔点略微增加。PSFLA的热分解温度大于220℃。PSFLA中的SF与聚乳酸(PLA)链段间可能存在着氢键相互作用,SF与乳酸链段可自组装形成片层结构。 相似文献
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以聚L-乳酸(PLLA)和麦草(WS)为原料,以N-甲基吗啉-N-氧化物(NMMO)为溶剂,采用溶液共混法制备了PLLA/WS共混物。首先将麦草溶解在NMMO后,再添加聚L-乳酸并溶解,制备聚L-乳酸与麦草的共混溶液。共混溶液采用浇膜法制备PLLA/WS共混物,采用差示扫描量热法、X射线衍射法、傅里叶变换红外光谱、热重分析和扫描电镜等方法对所得的共混物进行表征。结果表明,聚L-乳酸与麦草可以形成均匀的共混溶液。共混物中PLLA与麦草组分之间具有较强的相互作用,相容性较好。当共混物中PLLA的质量分数为50%时,共混物可以形成结晶结构,且随着PLLA含量的增加,其结晶更加完美,熔点与热稳定性提高。共混物薄膜断面结构较为致密,这说明PLLA与麦草相容性较好,混合均匀。通过调节聚L-乳酸和麦草的配比,可以制备不同性能的生物高分子材料。 相似文献
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以N-甲基吗啉-N-氧化物为溶剂,制备聚L-乳酸(PLLA)与麦草纤维(WSF)的共混溶液,并制备PLLA与WSF的共混物。采用傅里叶变换红外光谱、差示扫描量热法和X射线衍射等方法对PLLA/WSF共混物进行表征,探讨PLLA/WSF共混物中两组分的相容性和结晶性。结果表明,聚乳酸和麦草纤维的N-甲基吗啉-N-氧化物溶液可以均匀混合形成共混溶液。在PLLA/WSF共混物中,PLLA与WSF两组分之间的相互作用较强,具有较好的相容性。PLLA/WSF共混物的组成对其形态与性能具有显著影响。随着PLLA用量的增加,共混物的玻璃化温度逐步降低。当PLLA与WSF的质量比小于6∶4时,共混物为非晶态物质,而当PLLA与WSF的质量比大于6∶4时,共混物则具有结晶结构,且结晶熔点随着PLLA质量分数的增加而增加。因此,通过改变PLLA和WSF组分的配比,可以制备不同性能的可生物降解高分子材料。 相似文献
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-乳酸-乙基纤维素可生物降解材料的研究 总被引：4，自引：0，他引：4
聚L-乳酸（PLLA）和乙基纤维素（EC）的三氯甲烷溶液以不同比例混合均匀后．浇膜制备PLLA-EC可降解材料，并采用红外光谱（FT-IR）、差示扫描量热法（DSC）和X射线衍射等方法表征所得共混物。共混物的PLLA组分可能形成结晶，且其熔点随着EC含量的增加而略微降低，结晶度和晶体完整度均显著下降。同时，共混物的亲水性随着EC含量的增加而增大。这些因素影响着PLLA-EC共混物的降解性能，当EC含量高于30％时，PLLA-EC共混物在磷酸缓冲液中的降解速率迅速增大，并在EC为80％时最大。 相似文献
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《林产化学与工业》2018,(5)
为了改善聚乳酸材料的结晶性能、耐热性能和亲水性,以乳酸和葡萄糖为原料,熔融聚合制备了聚L-乳酸-葡萄糖共聚物(PLLAG)和聚D-乳酸-葡萄糖共聚物(PDLAG),并将PLLAG和PDLAG溶液共混,制备含葡萄糖基的聚乳酸立构复合物(sc-PLAG)材料。采用傅里叶变换红外光谱(FT-IR)、差示扫描量热(DSC)法、X射线衍射(XRD)法、偏光显微镜(POM)法和接触角法等对sc-PLAG进行表征,结果表明:sc-PLAG的立构复合结晶(SC)结构由PLLAG的L-乳酸链段与PDLAG的D-乳酸链段相互作用而形成的,结晶速度快、球晶形貌规整。当PLLAG用量为40%~60%时,sc-PLAG只生成立构复合结晶;当PLLAG用量小于40%或大于60%时,sc-PLAG则同时含有SC和同质结晶(HC)。当葡萄糖基质量分数均为5%时,所有sc-PLAG的SC熔点(T_m)均为197.5℃,与PLLAG用量无关。sc-PLAG的玻璃化转变温度(T_g)、T_m和接触角均随着葡萄糖基质量分数的增加而降低,但其结晶度则随着葡萄糖基质量分数的增加而增大,当葡萄糖基质量分数为5.0%时结晶度最大,为53.84%。含葡萄糖基的聚乳酸立构复合物改善了聚乳酸材料的结晶性能、耐热性能和亲水性。 相似文献
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增容处理对废PE木塑复合材料性能和结构的影响 总被引：2，自引：0，他引：2
采用熔融共混法制备二次植物纤维／废渣粒子混杂增强废地膜木塑复合材料,考察了增容剂马来酸酐接枝聚乙烯（PE—g—MA）对废地膜混杂木塑复合材料性能和结构的影响。研究表明,PE—g-MA是共混体系的良增容剂,PE—g—MA的加入显著提高了共混体系的力学性能。ATR和DSC分析表明,PE—g—MA的加入有效改善了混杂共混物的界面粘着力,提高了基体的结晶程度。 相似文献
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采用一步法连续挤出技术将麦秸粉和高密度聚乙烯复合制备木塑复合材料,并用马来酸酐接枝聚乙烯共聚物（MAPE）作为相客剂,研究其加入量对力学性能的影响。M-APE的加入对复合材料的拉伸、弯曲和冲击强度均有较大改善,且MAPE的加入量为9～12份时复合材料的力学性能达到最大值,扫描电镜所得的界面微观特征图也证明了这一点。 相似文献
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《Scandinavian Journal of Forest Research》2012,27(5):427-435
In Scandinavia, moose (Alces alces L.) sometimes cause severe browsing damage to economically-important pine. Moose-vehicle accidents have spurred construction of fences along roads, and these may interfere with moose migration between summer and winter ranges, or the road alone may be a barrier. If this happens and moose build up along roads, landowners may suffer economically. Therefore, this study investigated whether roads, fences or other factors influence the use of young pine stands by moose. Eighty stands along roads in northern Sweden were evaluated in which individually-browsed branches were counted on 9972 pines. Moose browsing was not significantly related to birch (Betula pendula Roth, B. pubescens Ehrh.) density, nor did it differ between pines (Pinus contorta Douglas or P. sylvestris L.). However, increased pine density, site productivity and proximity to a highway were associated with increased browsing. Further large-scale studies are needed to understand moose habitat selection and the effects of roads. 相似文献
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《Scandinavian Journal of Forest Research》2012,27(3):206-217
The root systems of 2-yr-old Picea glauca, Picea mariana and Pinus banksiana seedlings were submitted to various frost temperatures during an artificial frost to induce different levels of root damage. Frost-damaged and control seedlings were placed in a greenhouse under high and low soil moisture regimes. Seedling growth and physiology were evaluated periodically. Seedling survival was reduced when root damage reached levels of 60-80%. Root systems of all three species showed partial to total recovery by the end of the experiment. In general, root freezing damage caused reductions in seedling growth, with these reductions becoming less significant over time. Root damage had little to no effect on black spruce and jack pine seedling physiology, while white spruce CO 2 uptake decreased with increasing root damage. Shoot nitrogen content of all three species decreased slightly with increasing root damage. 相似文献
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《Scandinavian Journal of Forest Research》2012,27(1):53-61
This study investigated the stand structure in pine, spruce and deciduous forests in the border district of Finland and Russia. A total of 46 mature forest stands was selected as pairs, the members of each pair being as similar as possible with respect to their forest site type, age, moisture and topography. The stands were then compared between the two countries by means of basal areas and number of stems. The proportions of dominating tree species were 2-12% lower, and correspondingly the proportions of secondary tree species higher, in Russian forests. The density of the forest stock was also higher in each forest type in Russia. The forests in the two countries differed most radically in terms of the abundance of dead trees. The amount was two to four times higher in Russian deciduous and spruce forests, and in pine forests the difference was 10-fold. The stand structures indicated that Russian coniferous stands, in particular, were more heterogeneous than intensively managed pine and spruce stands in Finland. 相似文献
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《Scandinavian Journal of Forest Research》2012,27(1):15-27
The root collar diameter and the height:diameter ratio are of particular importance in container-grown seedlings where a high density in the containers may produce spindly seedlings. Temperature regimes and light quality are known to affect plant growth. The aim of this study was to identify responses in Picea abies (L.) Karst. seedlings grown with light providing different red:far-red ratios and under temperature regimes with alternating day (DT) and night temperature (NT) from negative (DT < NT) to positive (DT > NT) difference (DIF) between DT and NT. Experiments were conducted in controlled environment chambers and in a daylight phytotron. Only limited thermoperiodic responses appeared in P . abies seedlings with respect to seedling height and dry weight accumulation. The formation of terminal buds, however, was clearly delayed in seedlings grown at negative DIF. The results indicate a requirement for day extension light that is high in far-red, to prevent terminal bud formation under natural short-day conditions. An extended study should be conducted to clarify the minimum level of light intensity and the optimal light quality needed to prevent terminal bud formation under natural short-day conditions. 相似文献
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本文分析了CAD在设计中引起的正面和负面影响,并进行了系统的阐述,从而使设计者在应用中能够保持客观的态度。 相似文献
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《Scandinavian Journal of Forest Research》2012,27(5):472-479
Based on an enquiry, risk perception among non-industrial private forest owners is described in relation to climate change and forestry hazards. Of the respondents, 11% took action to remedy the effects of climate change. Out of a given set, hazards were ranked according to each respondent's experience of recent substantial financial loss to the estate and in relation to his or her willingness to make investments aimed at risk reduction. For each hazard, the respondent assessed the risk in four classes ranging from very high to negligible risk. Six hazards were considered most problematic in all three aspects: browsing damage, falling timber prices, damage by wind, spruce bark beetle, root rot and pine weevil. A majority of the respondents claimed to take action to reduce the risk associated with at least one hazard, while 35% did not know whether they did. Excluding climate change, the need for decision support was the largest in relation to damage by wind owing to a combination of perceived high risk and a high level of ignorance in relation to whether risk-reducing measures were taken. 相似文献
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Srisuda Thippayarugs Banyong Toomsan Patma Vityakon Viriya Limpinuntana Aran Patanothai Georg Cadisch 《Agroforestry Systems》2008,72(2):137-148
In situ produced plant residues contain a mixture of different plant components of varying quality. To assess synergistic
or antagonistic interactions occurring during the decomposition and mineralization of such mixtures, individual plant parts
(stems, leaves, leaf litter and roots) or the mixture of stems, leaves and leaf litter of the agroforestry species pigeonpea
(Cajanus cajan) or of crop residues of peanut (Arachis hypogaea) or of the weed hairy indigo (Indigofera hirsuta) were incubated in pots for 19 weeks. Periodically, remaining plant residues were sieved out (>2 mm), weighed and N content
as well as soil mineral N determined. Above- and below-ground residues of peanut decomposed fastest and showed the largest
N release in agreement with their high N concentration and low-acid detergent fibre (ADF) : N ratio. Hairy indigo was hypothesized
to be of lower quality than pigeonpea because of its high-polyphenol content. However, it decomposed faster than pigeonpea,
largely because of the higher N and lower lignin concentration of its components. Ranking of individual plant components for
N mineralization resulted in the following pattern, leaves > leaf litter > roots > stems. In mixtures of the different plant
components a similar species order in decomposition was obtained, e.g. peanut > hairy indigo > pigeonpea. The amount of N
released from the mixture was dominated by stem material that comprised 46–61% of the mixture. The interactions in mixtures
were relatively small for peanut (generally high-quality components) as well as for pigeonpea (low proportion of high-quality
components, i.e. N rich leaf material). However, a positive interaction occurred during later stages of N mineralization in
the mixture of hairy indigo as it had a significant proportion of N rich components and absence of highly reactive polyphenols.
Thus, for plants with low to intermediate chemical quality attributes, manipulating plant composition (e.g. by varying harvest
age, affecting stem and leaf proportions) will be important to obtain significant interactions during decomposition when its
components are mixed. 相似文献
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A. Rigueiro-Rodríguez M. R. Mosquera-Losada E. Gatica-Trabanini 《Agroforestry Systems》2000,48(3):245-256
The use of organic waste materials such as milk sewage as an organic fertilizer could have the dual advantages of organic-waste
disposal and reduced dependence on inorganic fertilizers. The effects of fertilization with (1) conventional mineral fertilization,
(2) milk sewage sludge at 40 kg N ha−1 target rate and (3) no fertilization on pasture production and tree growth were examined in an experiment consisting of two
pasture mixtures under a one-year-old Pinus radiata plantation with a density of 2500 trees ha−1. The two pasture mixtures were: (1) Dactylis glomerata L. var. saborto (25 kg ha−1) + Trifolium repens L. group Ladino (4 kg ha−1) + Trifolium pratense L. var. Marino (1 kg ha−1); (2) Lolium perenne L. var. Tove (25 kg ha−1) + Trifolium repens L. group Ladino (4 kg ha−1) + Trifolium pratense L. var. Marino (1 kg ha−1). The experiment began in the spring of 1995 using a randomized block design with three replicates in Castro Riberas de Lea
(Lugo, Galicia, north-western Spain). Plot size was 12 × 8 m2, with a 1 m buffer strip between plots. Two-year data showed that fertilization with either material had a positive effect
on pasture production, with no significant difference between the two fertilization treatments. Tree growth in the milk sewage
sludge plot was significantly higher than in the control plots. Inorganic fertilization increased pasture production, but
affected tree growth negatively. The results show that milk sewage sludge could be used as a fertilizer in silvo-pastoral
systems.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
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《Scandinavian Journal of Forest Research》2012,27(2):166-178
This study investigated the forest history, structural characteristics, the presence of fungal species suggested to indicate ecological continuity in old-growth forest, and the species composition of saproxylic beetles in 30 old forest ''woodland key habitats'' (WKHs), and compared them with production forest in the same age-class in south-eastern Norway. No statistically significant differences in forest characteristics, community of saproxylic beetles or number of red-listed beetles were found between the WKHs and the production forest, probably owing to a combination of profound long-term logging and a lack of will to delineate sufficiently large WKHs in the one area with significantly less forestry impact. The study indicates the advantage of including forest history information in WKH selection where such data exist, and the importance of restoring habitats in heavily exploited forest landscapes. 相似文献