Tannin-Based Biofoams-A Review

This review details the development of tannin-based biofoams for fire resistance and acoustic insulation and details the different varieties of these foams that have been developed,from tannin-furanic self-blowing foams to tannin-furanic polyurethanes and finally non-isocyanate tannin-basedcarbohydrates polyurethanes(NIPU).

Dielectric Permittivity of Rigid Rapeseed Oil Polyol Polyurethane Biofoams and Petrochemical Foams at Low Frequencies

Early investigations of dielectric permittivity of rigid polyurethane foams at low frequencies were made on petrochemical-origin foams,mainly by means of parallel plate capacitors.In the present investigation biopolyol was synthesized from Latvia-grown rapeseeds’oil by the transesterification method with triethanolamine,in an environmentally friendly process,without emission of harmful substances,at temperatures 175℃±5℃.Rigid,closed-cell rapeseed oil polyol polyurethane biofoams and petrochemical foams were made ensuring content of the renewable rapeseed oil polyol in ready foams 27 wt.%–29 wt.%.Dielectric permittivity of the polyurethane foams and the underlying monolithic petrochemical-origin polyurethane and biopolyurethane was measured with a non-destructive dielectric spectrometer equipped with a capacitive sensor of one-side access type at 16 discrete frequencies distributed geometrically over the band 10 Hz,…,330 kHz.Permittivity value of the gaseous phase in the closed-cells was estimated to beεg≈1.001 that corresponds to the values,characteristic for the most of gases.Dielectric permittivity of petrochemical polyurethane foams and the mentioned biofoams was compared with permittivity of polyurethane foams from industrial producers Sika JSC and General Plastics Manufacturing Co.Polyurethane foams of the developed formulation exhibit competitive,low dielectric permittivity,not exceeding that of the foams from industrial producers:petrochemical foams up to 550 kg/m^(3) and the mentioned biofoams,comprising the renewable rapeseed oil polyol,up to densities 230–250 kg/m^(3).Considering petrochemical-origin polyurethane foams as a heterogeneous media“Polymer—gaseous phase”,the applicability of the rule of mixture and Maxwell–Garnett equation to model mathematically the dependence of effective dielectric permittivity on the volume fraction of phases was showed.

Glucose-Biobased Non-Isocyanate Polyurethane Rigid Foams

Glucose-based non-isocyanate polyurethanes(NIPU)were prepared by reaction of glucose with dimethyl carbonate and hexamethylene diamine.These were used to prepare partially biobased polyurethane foams by reaction with NaHCO3 as a blowing agent and addition of a silane coupling agent having different functions such as coreactant and adjuvant to obtain more uniform and smaller cells.The foams were foamed and hardened by applying heat.The foams presented very limited fire resistance indicating that as for synthetic polyurethane foams the eventual use of a fire retardant appears to be necessary.The 2 hours water absorption was used to indicate if close cells or open cells occur.More characteristic is their stress strain behaviour.While compression does indeed flatten the cell walls nonetheless the cellular structure is maintained and the cell walls have not been destroyed.This indicates a certain level of elasticity in the cell walls of formulations containing NaHCO3.In effect the macro-appearance of this foams,confirms this explanation as the foam is densified and holds together.

Self-Blowing Non-Isocyanate Polyurethane Foams Based on Hydrolysable Tannins

ABSTRACT Non-isocyanate polyurethane(NIPU)foams using a hydrolysable tannin,also vulgarly called tannic acid,namely here commercial chestnut wood tannin extract was prepared.Compression strength did not appear to depend on the foam apparent density while the formulation composition of the NIPU foams has been shown to be more determinant.These NIPU foams appeared to be self-extinguishing once the high temperature flame is removed.The ignition time gave encouraging results but for improved fire resistance the foams may need some fire-retardant addition.FTIR spectrometry showed the formation of non-isocyanate urethane linkages.Thermogravimetric analysis indicated a good thermal resistance of these foams,with thermal degradation following four phases.First in the interval 25℃–120℃ range,mainly evaporation of water occurs with a maximal loss of 10%weight.In the 150℃–450℃ temperature range foams mass loss is of almost 70%.In particular in the 125℃–275℃ range occurs the degradation of some small molecular weight substances.In the 500℃–790℃ temperature range the foams do not present any further large degradation.

Amorphous Polylactide Bead Foam–Effect of Talc and Chain Extension on Foaming Behavior and Compression Properties

Polylactide(PLA)bead foams show a high potential regarding their applicability in packaging or consumer products.Concerning the comparable properties of PLA to Polystyrene(PS)and the good CO_(2) footprint it represents a potential alternative to petroleum-based polymer foams.However,foaming of PLA is challenging,due to its low melt strength,therefore chemical modifiers are often used.Concerning the bead foam technology regarding PLA,the available literature is limited so far.Within this study,the bead foaming behavior of neat and modified amorphous PLA was investigated.The material was modified by talc and an epoxy-based chain extender.These compounds have been investigated regarding their sorption behavior in CO_(2) atmosphere and their foaming behavior.Foaming was conducted by using the batch foaming method based on a rapid temperature increase after saturation with CO_(2).In order to achieve welded bead foams,a one-step processing for foaming and welding has been established.Finally,the compression properties of the PLA bead foams have been investigated.Densities below 50 kg/m^(3) for single bead foams and 80 kg/m^(3) for molded foams were achieved,respectively.

生化曝气单元泡沫产生原因分析及对策

针对炼油污水处理装置生化曝气单元产生泡沫的现象,先分析了产生泡沫的一般影响因素,再根据对现场污泥性状的全面分析,找出了生物曝气单元产生生物泡沫的原因,对生化系统的进水温度、污泥龄、pH、DO及进水组分有针对性地采取了措施,并采用人工转移的方法降低泡沫量。实践证明,这些措施实施后大幅度削减了生物泡沫的数量,为总排出水COD、SS及浊度组分达标创造了条件,取得了较好的效果。

应用于包装领域的明胶泡沫性能研究

目的制作和表征基于明胶的生物基可堆肥降解泡沫材料,并应用于包装领域。方法明胶泡沫通过机械发泡和在周围环境中干燥制成。研究明胶含量、表面活性剂含量以及发泡温度对泡沫最大发泡倍率(MER)、收缩、密度、结构以及压缩性能的影响。此外,研究不同明胶含量样品的导热率。结果研究的3个因素对泡沫性能和结构有显著影响。MER值和收缩是黏度相关,并极大地影响泡沫密度、力学性能以及热导率。增加明胶含量制造出了密度和压缩强度更高的泡沫(由于MER值更低)。表面活性剂质量分数从0.75%增加到1.5%由于发泡性提升造成泡沫密度轻微下降。然而,进一步将表面活性剂质量分数提升至3%造成黏度显著增加、MER值下降,从而导致泡沫密度增加。更高的发泡温度可以得到更高的MER,但是由于液态泡沫稳定时间更长,收缩程度更大,泡沫密度更大。结论明胶泡沫展现出作为低密度传统塑料泡沫(密度小于30 kg/m^(3))环保替代品极具潜力的性能。研究成功实现了明胶泡沫的低热导率〔0.038~0.039 W/(m.K)〕和相对较低的收缩程度。

Starting materials, processes and characteristics of bio-based foams: A review

Biofoam products have attracted considerable attention lately because there is a growing demand for green/sustainable products.To this end,various biobased foams have either been developed or are currently in development,e.g.,bio-based polyurethanes(PUs),polylactic acid(PLA),starch,and polyhydroxyalkanotates(PHAs).Indeed,significant progress has been made;however,chal-lenges still persist,for example,biobased foam products have poor processability,inferior com-patibility,thermal and strength properties.In this review,we focus on five biofoam products:namely bio-based PUs,PLA,starch,PHAs,and cellulose biofoam products,along with their prop-erties and performance,as well as their manufacturing processes.Further efforts are still needed to unlock the full potential of these bio-based products and meet the goal of complementing and gradually replacing some of their fossil-based counterparts.Finally,the challenges,as well as arising opportunities of future research directions are discussed.