Severe plastic deformation (SPD) of biodegradable magnesium alloys and composites: A review of developments and prospects

The use of magnesium in orthopedic and cardiovascular applications has been widely attracted by diminishing the risk of abnormal interaction of the implant with the body tissue and eliminating the second surgery to remove it from the body.Nevertheless,the fast degradation rate and generally inhomogeneous corrosion subsequently caused a decline in the mechanical strength of Mg during the healing period.Numerous researches have been conducted on the influences of various severe plastic deformation(SPD)processes on magnesium bioalloys and biocomposites.This paper strives to summarize the various SPD techniques used to achieve magnesium with an ultrafine-grained(UFG)structure.Moreover,the effects of various severe plastic deformation methods on magnesium microstructure,mechanical properties,and corrosion behavior have been discussed.Overall,this review intends to clarify the different potentials of applying SPD processes to the magnesium alloys and composites to augment their usage in biomedical applications.

A Literature Review on Sustainability of Bio-Based and Biodegradable Plastics:Challenges and Opportunities

This study examines the literature on bio-based and biodegradable plastics published between 2000 and 2021 and provides insights and research suggestions for the future.The study gathers data from the Scopus and ISI Web of Science databases,then picks 1042 publications objectively and analyses their metadata.Furthermore,144 papers from the Web of Science are analysed to present insights and classifications of the literature based on content analyses,including assessment/evaluation of the sustainability of bio-based and biodegradable Plastics,sustainability of biodegradable Plastics,and factors driving the uptake of biodegradable plastics.The study finds that most research on bio-based and biodegradable plastic film evaluations considered only one dimension of sustainability,few considered two dimensions,and very few considered three dimensions.Though,in recent years,academic and industrial interest has grown dramatically in biodegradable plastics towards sustainability.The triple bottom line method in this report(economic benefit,social responsibility,and environmental protection)was employed to assess the biodegradable plastics towards sustainability.Top journals,Influential authors,top contributing institutions,top contributing nations,and contributions by fields are all identified in this study.This research gives a detailed but straightforward theoretical design of bio-based and biodegradable polymers.The study’s results and future research initiatives provide a new path for further investigation and contribution to the field.

Effects of biodegradable mulch on soil water and heat conditions,yield and quality of processing tomatoes by drip irrigation

To combat the problem of residual film pollution and ensure the sustainable development of agriculture in oasis areas,a field experiment was carried out in 2019 at the Wuyi Farm Corps Irrigation Center Test Station in Urumqi,Northwest China.Four types of biodegradable mulches,traditional plastic mulchs and a control group(bare land;referred to as CK)were compared,including a total of six different treatments.Effects of mulching on soil water and heat conditions as well as the yield and quality of processing tomatoes under drip irrigation were examined.In addition,a comparative analysis of economic benefits of biodegradable mulches was performed.Principal component analysis and gray correlation analysis were used to evaluate suitable mulching varieties for planting processing tomatoes under drip irrigation.Our results show that,compared with CK,biodegradable mulches and traditional plastic mulch have a similar effect on retaining soil moisture at the seedling stage but significantly increase soil moisture by 0.5%-1.5%and 1.5%-3.0%in the middle and late growth periods(P<0.050),respectively.The difference in the thermal insulation effect between biodegradable mulch and plastic mulch gradually reduces as the crop grows.Compared with plastic mulch,the average soil temperature at 5-20 cm depth under biodegradable mulches is significantly lowered by 2.04°C-3.52°C and 0.52°C-0.88°C(P<0.050)at the seedling stage and the full growth period,respectively,and the water use efficiency,average fruit yield,and production-investment ratio under biodegradable mulches were reduced by 0.89%-6.63%,3.39%-8.69%,and 0.51%-6.33%(P<0.050),respectively.The comprehensive evaluation analysis suggests that the black oxidized biological double-degradation ecological mulch made from eco-benign plastic is the optimal film type under the study condition.Therefore,from the perspective of sustainable development,biodegradable mulch is a competitive alternative to plastic mulch for large-scale tomato production under drip irrigation in the oasis.

Development Situation and Prospect Analysis of Biodegradable Film Industry

Application and promotion of biodegradable plastic film in modern agricultural production construction have become trend and direction of agricultural development.As important production material,biodegradable plastic film not only effectively changes agricultural production mode but also effectively decreases environmental pollution.Accompanied by degradation of new material,upgrading of optimizing process,and infiltration and blending of science and technology in new plastics industry,new biodegradable plastic films have been developed and popularized effectively and rapidly.In this paper,starting from development situation and prospect of degradable plastic film in China,natural-based biodegradable plastics,petroleum-based biodegradable plastics and biological-based biodegradable plastics are introduced in detail from basic material of plastics.The advantages and disadvantages of additive biodegradable film and fully biodegradable film are scientifically analyzed,and seasonal and periodic characteristics of biodegradable plastic film industry are elaborated.Moreover,disadvantages of biodegradable plastic film industry development are explored from technical barrier,brand and channel barriers,and talent barrier.Finally,development trend of biodegradable plastic film industry in China is predicted and analyzed scientifically.The research could provide guidance for the development of biodegradable plastic film industry in China ,research of biodegradable plastic film technology,and demonstration and extension of biodegradable plastic film application.

Preliminary Studies on the Microbial Degradation of Plastic Waste Using <i>Aspergillus niger</i>and <i>Pseudomonas</i>sp.

The possibility of microbial degradation of plastic waste was investigated by isolating microorganisms present in dumpsite containing low-density polyethylene (LDP). Aspergillus niger (fungi) and Pseudomonas sp. (bacteria) were identified and subsequently used to biodegrade plastic waste. The medium was made up of 0.2 g of MgSO4, 1.0 g of KH2PO4, 1.0 g of K2HPO4, 1.0 g of NH4NO3, 0.02 g of CaCl2, 0.05 g of FeCl3 in 1000 ml water. 10 ml of the medium containing the bacteria and/or fungi was poured into test tubes and 0.1 g of the plastic sample (Pure water sachet) pre-treated with ethanol was introduced into the tubes. The pH of the medium was adjusted to 7.2, 5.4 and 6.0 for Pseudomonas sp., Aspergillus niger and the mixed culture respectively. Each experiment was carried out aerobically at room temperature and incubated on a rotary shaker at 120 rpm. The weight loss in each experiment was monitored at 10 days interval for 60 days. The total weight loss after 60 days was 7.2%, 12.4%, 15% for degradation with Pseudomonas sp., Aspergillus niger and the mixed culture respectively. From this study it can be inferred that Pseudomonas sp. and Aspergillus niger have the ability to degrade plastics. It can also be inferred that Aspergillus niger degraded plastics better than Pseudomonas sp. and there was synergy between the two microorganisms since the mixed culture gave a higher degradation.

Improving Polylactide Toughness by Plasticizing with Low Molecular Weight Polylactide-Poly(Butylene Succinate)Copolymer

A low-molecular-weight polylactide-poly(butylene succinate)(PLA-PBS)copolymer was synthesized and incorporated into polylactide(PLA)as a novel toughening agent by solvent casting.The copolymer had the same chemical structure and function as PLA and it was used as a plasticizer to PLA.The copolymer was blended with PLA at a weight ratio from 2 to 10 wt%.Phase separation between PLA and PLA-PBS was not observed from their scanning electron microscopy(SEM)images and the crystal structure of PLA almost remained unchanged based on the X-ray diffraction(XRD)measurement.The melt flow index(MFI)of the blends was higher as the amount of PLA-PBS increased,indicating that the block copolymer did improve the mobility of the PLA chains.Moreover,tensile tests revealed that PLA with greater PLA-PBS copolymer exhibited higher elongation at break and it reached the maximum at 8 wt%of PLA-PBS in PLA,which was around 6 times higher than that of pure PLA.Furthermore,the glass transition temperature,measured by differential scanning calorimetry(DSC),markedly decreased with an increasing amount of the copolymer as it decreased from 61.2℃ for pure PLA to 41.3℃when it was blended with 10 wt%PLA-PBS copolymer.Therefore,the PLA-PBS copolymer was shown to be a promising plasticizer for fully biobased and toughened PLA.

PRODUCTION OF BIOPLASTICS AND HYDROGEN GAS BY PHOTOSYNTHETIC MICROORGANISMS

Our efforts have been aimed at the technological basis of photosynthetic-microbial pro-duction of materials and an energy carrier. We report here accumulation of poly-(3-hydroxybutyrate)(PHB), a raw material of biodegradable plastics and for production of hydrogen gas, and a renewable en-ergy carrier by photosynthetic microorganisms (tentatively defined as cyanobacteria plus photosynthetic ba-teria, in this report).A thermophilic cyanobacterium, Synechococcus sp. MA19 that accumulates PHB at more than 20%of cell dry wt under nitrogen-starved conditions was isolated and microbiologically identified. The mecha-nism of PHB accumulation was studied. A mesophilic Synechococcus PCC7942 was transformed with thegenes encoding PHB-synthesizing enzymes from Alcaligenes eutrophus. The transformant accumulated PHBunder nitrogen-starved conditions. The optimal conditions for PHB accumulation by a photosynthetic bac-terium grown on acetate were studied.Hydrogen production by photosynthetic microorganisms was studied. Cyanobacteria can produce hy-drogen gas by nitrogenase or hydrogenase. Hydrogen production mediated by native hydrogenase incyanobacteria was revealed to be in the dark anaerobic degradation of intracellular glycogen. A new sys-tem for light-dependent hydrogen production was targeted. In vitro and in vivo coupling of cyanobacterialferredoxin with a heterologous hydrogenase was shown to produce hydrogen under light conditions. A trialfor genetic trasformation of Synechococcus PCC7942 with the hydrogenase gene from Clostridum pasteuri-anum is going on. The strong hydrogen producers among photosynthetic bacteria were isolated and charac-terized. Co-culture of Rhodobacter and Clostriumdium was applied to produce hydrogen from glucose.Conversely in the case of cyanobacteria, genetic regulation of photosynthtic proteins was intended to im-prove comversion efficiency in hydogen production by the photosynthetic bacterium, Rhodobactersphaeroides RV. A mutant acquired by UV irradiation will be characterized for the mutation and for hydro-gen productivity in comparison with the wild type strain. Some basic studies to develop photobioreactorsare also introduced.

Plastic Waste Management by Substituting Natural Fibres

This paper presents substitute for non-biodegradable plastic packed material which comes as a part of municipal solid waste and becoming global problem due to its overuse. The plastic as packaging material has its advantages but also have more disadvantages because of its durability that it does not degraded. If the packaging material is made up of natural fibres it has more effect on local ecosystem. This paper provides the solution that use of natural fibres as pack-aging due to its light weight, high strength to weight ratio, corrosion resistance and other advantages are useful for the industry as well as commercially availability for the markets.

Fabrication of Manila Hemp Fiber Reinforced Cross Ply Biodegradable Composites and Their Tensile Properties

Natural plant fibers, including flax, kenaf, jute, bamboo, ramie and much more are renewable and sustainable resources and are considered good candidates for cost-effective alternatives to glass and carbon fibers. In this research, cross ply biodegradable composites were fabricated by press-forming method. The biodegradable composites consist of Manila hemp textile as a reinforcement and starch-based biodegradable plastics as a matrix was fabricated and investigated about mechanical properties. The tensile strength increased with the fiber content until fiber content of about 50% and leveled off thereafter. This dependence on the fiber content is due to the decrease in fiber strength of loading direction caused by fiber damages introduced during hot-pressing. In order to decrease the damage of fibers aligned in loading direction, Manila hemp textile was produced by using Manila hemp fibers for warp and biodegradable resin thread for weft. As a result, the tensile strength of cross ply composites increased from 153 MPa to 202 MPa.

Research State of Disposable Nonplastic Straws

The continuous production of disposable plastic straw places a high demand on global petrochemical resources and a significant environmental burden.Biodegradable and eco-friendly straws have therefore been studied and produced worldwide.This article briefly introduces the characteristics of paper straws and polylactic acid(PLA)straws,and focuses on edible straws made using,e.g.,hydrophilic colloids,zein,and starch.Raw-material selection,preparation methods,advantages,and defects of straws are summarized,to provide a reference for the development and research of eco-friendly straws.

Knowledge and Opportunities from the Plastisphere:A Prelude for the Search of Plastic Degrading Bacteria on Coastal Environments

Plastic pollution has become an urgent issue,since its invasion to everyecosystem has led to multiple impacts on the environment and human pop-ulations.Certain microbial strains and genera had shown the ability to bio-degrade plastic sources under laboratory conditions.In this minireview,wecallect and analyze scientific papers and reports of this microbial activity aswe contextualize this information on the global plastic pollution problem,toprovide an updated state of the art of plastiq/biodegradation with microbialagents.Along with a broad understanding of the general process of plasticbiadegraclation hosted by micrnarganisms.The contributions of this mini-revicw came from the identification of rescarch gaps,as well as proposalsfor new approaches.One of the main proposals focuses on coastal environ-nents and in particular coastal wetlands as a great microbiome source withpatential for plastic biodegradation,whether reported or undiscovered.Ourfinal proposal consists of the application of this knowledge into technologictools and strategies that have a remarkable impact on the battle against theplastic pollution problem.

水性丙烯酸树脂对PBAT/淀粉复合材料性能影响

研究了四种水性丙烯酸树脂对聚对苯二甲酸-己二酸丁二酯(PBAT)/淀粉复合材料性能的影响,选择最佳水性丙烯酸树脂进一步研究其用量对复合材料性能的影响。通过万能拉伸测试仪、熔体流动速率仪、接触角测试仪、差式扫描量热仪、热失重分析仪对复合材料力学性能、熔体流动性能、亲水性能、热性能进行了分析;采用红外光谱仪、偏光显微镜对PBAT/淀粉复合材的分子结构与微观组织形貌进行了表征。研究结果表明:玻璃化温度较低的水性丙烯酸树脂对淀粉的改性效果更佳;当水性丙烯酸树脂7168(B7168)用量为25.2g时,复合材料拉伸强度和断裂伸长率有最佳值,较空白样提高10.8%和38.5%;随B7168的增加,复合材料熔体流动速率先减小后趋于平缓,亲水性能增加,对PBAT的结晶和熔融温度影响不明显,对球晶形貌影响不大,但使球晶平均直径略有减小,3000~3600 cm^(-1)的红外响应峰强度有增加的趋势,波峰略向低波数方向移动;热失重显示B7168的加入,使体系热分解起始温度提前,700℃残余量增加。

全生物降解地膜对湖南不同地区果蔬生长的影响

针对塑料地膜使用造成土壤环境污染的问题,研究以白色/黑色全生物降解地膜和普通塑料地膜为参试材料,在湖南省长沙市、沅江市、汉寿县等地区开展了西瓜、莴苣、秋葵等作物的覆膜试验,探究全生物降解地膜对不同作物的生长、品质、产量及土壤性质等指标的影响,观察全生物降解地膜的降解情况。结果发现,两种全生物降解地膜对湖南各地区果蔬生产均起到提质增效的作用。沅江地区黑色降解地膜覆盖栽培西瓜,西瓜单瓜重增加25.8%,叶片数增加45.5%,显著高于未覆膜处理;覆盖白色降解地膜的秋葵叶片长度比对照高42.1%,叶片宽度比对照高55.9%,叶片数增加43.2%,产量增加55.5%。普通塑料地膜在作物收获后未能降解,白色和黑色全生物降解地膜的降解率分别为80.3%~90.7%和63.0%~80.3%。综合不同地区的试验结果,认为两种降解地膜均可作为普通塑料地膜的潜在替代品,具有较大的推广前景。

典型生物可降解塑料热处理特性及动力学

为了探究生物可降解塑料在热处理过程中的特性,采用热重分析仪分别在不同升温速率下(10,20和30℃/min)对由聚乳酸(PLA)和聚对苯二甲酸-己二酸丁二酯(PBAT)组成的生物可降解塑料(BP1)的失重特性进行分析,BP1在氮气和空气气氛下的反应过程都非一步完成,主要反应阶段都存在明显的两步失重过程,在氮气和空气气氛下两个主要反应阶段的质量损失率分别达到87.99%~89.64%,84.99%~86.88%,且两反应阶段温度区间存在明显重叠.利用Flynn–Wall–Qzawa(FWO)、Kissinger-Akahira-Sunose(KAS)、Starink三种等转化率法计算动力学参数,得到BP1在氮气气氛下阶段一、阶段二的平均活化能E分别是88.95,90.92kJ/mol,空气气氛下阶段一、阶段二的平均活化能E分别是67.23,91.27kJ/mol;采用积分主图分析法(Master-plots法)基于10℃/min确定其动力学反应机理,表明BP1主要反应阶段均符合随机成核和核生长模型(An),但反应级数有所区别,说明氮气和空气不同气氛,并不会影响其反应机理,只是在活性点位的产生和失活速率快慢方面有所区别.

壬酸增塑改性明胶膜的制备及性能研究

可生物降解塑料的研发对于实现“双碳”目标具有重要的意义和价值。以明胶为原材料,通过壬酸增塑、双醛淀粉交联和热压处理相结合的方法制得明胶膜,探究壬酸增塑和热压处理对双醛淀粉交联的明胶膜结构和性能的影响。结果表明,当壬酸添加比例为20%时,改性的明胶膜表面光滑、结构致密,具有最高的抗张强度和较低的断裂伸长率、水蒸气透过率和溶胀性能。经过11 min的热压处理后,明胶膜表现出良好的耐水性和力学性能,且在土壤中被降解22 d后仍然能够维持较完整的薄膜形貌,降解34 d后其质量损失超80%。基于壬酸增塑、双醛淀粉交联和热压处理制备的明胶膜机械强度高、耐水性好且可生物降解,其为环境友好蛋白塑料的研发提供了有益策略。

改性复合生物降解地膜的制备及玉米田间应用评价

[目的]使用生物降解地膜替代传统聚烯烃地膜已成为治理农业白色污染的一项重要技术。主流材料聚对苯二甲酸-己二酸丁二醇酯(PBAT)在制备生物降解地膜时表现出优异的成膜性能,但其水蒸气阻隔性较差,导致降解时间短,限制了其在农用地膜方面的应用。因此,需要进行改性研究以解决PBAT生物降解地膜在拉伸强度、水蒸气阻隔性能和降解期等方面的不足。[方法]本研究将PA6(尼龙6)与PBAT相结合,使用高分子共混法制备PBAT/PA6改性生物降解地膜。该方法制备的生物降解地膜有效地将PBAT与PA6融合在一起,电子显微镜测试表明,混合地膜的表面和横截面均无明显缺陷。于2023年春玉米生长季,在北京顺义地区农田设置不同覆膜处理(PBAT地膜覆盖,PBAT/PA6-10地膜覆盖,PE地膜覆盖,不覆膜处理即CK)的田间对比试验,研究土壤温度、地膜田间降解情况、春玉米产量及其构成因素的变化。[结果]与纯PBAT生物降解地膜相比,本研究所开发的生物降解地膜的拉伸强度提高了约2.7倍,水蒸气阻隔性能提高了79.44%,功能期延长了30 d。玉米作物田间试验表明,改性生物降解地膜更适合农业生产,因其可提高隔热性和保湿性,使玉米产量较纯PBAT地膜提高7.03%,接近传统聚乙烯地膜产量。[结论]将PA6与PBAT材料相结合,开发出了一种新型复合生物降解地膜PBAT/PA6。PA6的加入与PBAT反应形成酰胺键使其整体结构具有稳定性,所制备复合生物降解地膜表面和截面形貌良好,内部无明显孔洞,较PBAT地膜表面更光滑,同时在力学性能和水蒸气阻隔性能上较纯PBAT地膜有显著提升,在田间试验过程中,复合生物降解地膜PBAT/PA6具有优秀的耐降解性能,延长了覆盖时间,并较纯PBAT地膜显著提高春玉米的产量。

塑料降解测试中塑料混合物湿度的变化规律

通过对比塑料混合物各组分湿度测量方法,以不破坏塑料混合物且测量结果原理上相对准确的干燥称重法为基础,结合GB/T 19277.1—2011的测试方法,设计了塑料混合物湿度的测量方案。结果表明,与常规的烘干称重法获得的塑料混合物测量的质量湿度差距在3%~5%之间,质量湿度达到9%左右就很难再进行快速变化;塑料混合物湿度变化过程具有常速率、减速率和残余3个阶段,使用Boltzmann函数能够较好地拟合出塑料混合物湿度变化的常速率与减速率阶段的变化趋势;按需补水更有利于需氧生物降解活动的进行,更符合国标对塑料需氧生物降解测试的要求;根据3种气体流量下塑料混合物水分质量散失变化曲线,得到了任意气体流量下的水分质量散失变化曲线计算方法。

生物降解渗水地膜覆盖对旱作燕麦土壤酶活性及产量的影响

为探讨生物降解渗水地膜覆盖对黄土高原旱作区穴播燕麦土壤酶活性及产量的影响,于2021年开展了普通地膜、渗水地膜、生物降解渗水地膜3种类型地膜覆盖穴播燕麦研究,以不覆膜为对照(CK),分析不同类型地膜覆盖对旱作燕麦田间水热效应、土壤酶活性及产量的影响。结果表明,与CK相比,覆膜处理苗期地表土壤温度提高了0.04~4.98℃,显著(P<0.05)提高了0~40 cm土层土壤含水量;生物降解渗水地膜显著提高苗期土壤过氧化氢酶、脲酶活性以及成熟期蔗糖酶、脲酶活性,增幅11.03%~39.37%;在抽穗期,上述三种酶活性均达最大,生物降解渗水地膜覆盖处理0~20 cm土层土壤过氧化氢酶和蔗糖酶活性显著提高(增幅分别为0.82%和55.88%)。与CK相比,覆膜处理显著增加了燕麦籽粒产量和生物产量,总体表现为渗水地膜>普通地膜>生物降解渗水地膜>不覆膜,生物降解渗水地膜与普通地膜间无显著差异;生物降解渗水地膜较普通地膜覆盖节约成本1800元·hm^(-2)。综合考虑生态效益和经济效益,推荐在黄土高原旱作区应用生物降解渗水地膜穴播燕麦技术。